U.o. ->'^f'- 
 
 ^^ l^ '^// ^^^^^.^^^Ay /S.^
 
 WAR DEPARTMENT - - OFFICE OF IHE CHIEF SIGNAL OFFICER 
 
 MANUAL NO. 3 
 
 TECHNICAL EQUIPMENT OF 
 THE SIGNAL CORPS 
 
 1916 
 
 WASHINGTON 
 GOVERNMENT PRINTING OFFICE 
 
 1917
 
 \\'ar Department, 
 Dncuineni No. 541. 
 fice of the ( 'hirf Sigval Officer,
 
 IL^,-^-. 
 
 TABLE OF CONTENTS. 
 
 ('HAI'TKIi 1. 
 
 The voltaic cell, Ohm's law, aiul primary aiul .^('((iiiilary batteries 1 
 
 C' HAI'TKII 2. 
 
 Telegraphy and the in<lui1ion t olograph wt 33 
 
 CuArTKR :'>. 
 
 Telejihony, (he camp lelephoiic ami t he Inizzor 67 
 
 Chapter i. 
 Cable and (^11)10 sy.slems iOl 
 
 Chapter 5. 
 Aerial line construction 175 
 
 Chapter (i. 
 Post telei)h()nc systems 211 
 
 Chapter 7, 
 Small-arms target range signaling systems 265 
 
 Chapter 8. 
 Technical ecpiipment issued by the Signal Corps 283 
 
 Chapter 9. 
 Miscellaneous tests and general information 381 
 
 Chapter 10. 
 Requisitions and general main1enan<e regulations 423 
 
 Chapter II. 
 Long submarine cables; Submarine tclesraph\ ; Tests ol longsul>marine cables. 437 
 
 HI 
 
 .'J615^.7'
 
 INTRODUCTORY. 
 
 This mannnl, whioli siiporsodes Mannnl No. o. edition of 1910, and Manual 
 No. 4, Handbook of Suhniai-iiie Cables of tlie United States Signal Corps, 
 1905, relates principally to the latest technical equipment of the Signal Corps 
 issued for held use of the mobile army, and to the technical eiiuipnient in- 
 stalled at mobile army posts. An enumeration of all Signal Corps equipment 
 appears in chapter S. 
 
 Fire-control systems and their eiiuipment are described in Signal Corps 
 Manual Xo. 8, latest edition. 
 
 Technical information relative to radiofelegraphy and e([uipment Is em- 
 bodied in •• Kadiotelegraphy ■'( Signal Office Circular Xo. 1). 
 
 Information concerinng signaling eciuipment may be found in Signal Book, 
 I'nited States Army. 
 
 Signal Corps Manual No. 4, Handiwiok of Submariiie Cables of the United 
 States Signal Corps, 1905 has become obsolcir and information relative to 
 laying, operation, and maintenance of long sulmiarine cables is supplied in 
 chapter 11 of this manual.
 
 CnAI'TKK 1, 
 
 THE VOLTAIC CELL. OHM'S LAW. AND PRIMARY AND SECONDARY 
 
 BATTERIES. 
 
 I'HK \(>I.1'AH ( Kl.l.. 
 
 If zinc and carbon are immersed in an acid or .saline solution and the two 
 connected externally by a wire, an electric current will flow from one to the 
 other. Any two dissinnlar metals when inunersed in an ackl solution which 
 acts on one more than on the other and connected externally by a wire will 
 produce similar results. There are a few nunmetallic substances which if used 
 in a voltaic cell in the place ()f metal elements will produce the same result, 
 'riir sulimerijed substances are termed plates or elements, and the solution is 
 termed electrolyte. The combination of plates or elements, electrolyte, and 
 containing ves.sel constitutes a voltaic cell. 
 
 Authorities differ as to .lust why a current of electricity flows under the 
 conditions stated above. Suflice it to say that it does flow, and that invariably 
 one (if the plates is acted upon (decompo.sed or eaten away) to a very much 
 greater tlegree than the other. Experiment has shown that substances uniler 
 above conditions which are acted uiion eiiually do not cause a current of elec- 
 tricity to flow. • 
 
 Where carbon and zinc are used as the plates in the voltaic cell, the carbon 
 is termed the negative plate or element and the zinc is termed the positive plate 
 or element. The carbon or negative element forms the positive pole of the bat- 
 
 Fig. 1-1.— VOLTAIC CELL. 
 
 . tery. and the zinc or posiUvc clemeni foinis the negative pole. The reason for 
 this apparent ctmtradiction is as follows : In any source of electricity the current 
 flows from positive to negative, and in the voltaic cell, with plates connected 
 externally with a wire, the current flows from zinc through electrolyte to car- 
 bon ; this is termed the internal circuit. Outside the battery current flows from 
 
 (1)
 
 2 Signal Corps Manual No. 3. — Chapter I. 
 
 carbon plate through wire to zinc ; this is termed the external circuit. Thus it 
 will be noted that in the internal circuit the current tlows to and from directly 
 opposite plates to those in the external circuit. Figure 1-1 illustrates the above. 
 The term " circuit " is applied to the entire path through which the current 
 of electricity flows. The wire joining the plates is a conductor. Bringing the 
 ends of the conductor into contact is called making or closing the circuit, and 
 their .separation, opening or breaking the circuit. A substance through which 
 the current readily flows is a good conductor. Any substance which offers an 
 extremely high resistance to the flow of an electric ciu'rent is an insulator. 
 Most metals are good conductors, while mica, glass, porcelain, dry wood, dry 
 atmosphere, rubber, etc., are insulators. 
 
 ohm's law. 
 
 With any circiiit through which a direct current of electricity is flowing there 
 are the three governing factors, which are as follows : 
 
 (1) The difference of potential between the positive and negative pole of the 
 generating medium, known as the pressure or electromotive force, the Tinit of 
 which is the volt. (Abbreviated V., E., or E. M. F.) One volt is that electro- 
 motive force which would maintain in a circuit having 1 ohm resistance a cur- 
 rent strength of 1 ampere. 
 
 (2) The resistance or opposition by the conductor to the flow of current, the 
 unit of which is the ohm. (Abbreviated R.) One ohm is that i-esistance in a 
 circuit which if impressed with an electromotive force of 1 volt allows a current 
 strength of 1 ampere to flow through the circuit. One ohm is the resistance of 
 a column of mercury about 42 inches high and 0.00155 square inch in cross- 
 sectional area at zero centigrade. 
 
 (3) The current strength or rate of flow, the unit of which is the ampere. 
 (Abbreviated I.) One ampere is that strength of current which would be main- 
 tained in a circuit having 1 ohm resistance if imjiressed with an electromotive 
 force of 1 volt. 
 
 From the above it will be noted that a deflnite relation exists between these 
 factors, so that the value of any one of them can be found if the values of the 
 other two are known. This relation, expressed by Ohm's law, is as follows : 
 
 (a) The current strength in a circuit may bt" lound by dividing the pressure, 
 or electromotive force, applied to it by the resistance. 
 
 r,- „N E M F (in volts) 
 
 /(m amperes)— ' 
 
 R (in ohms) 
 
 {})) The electromotive force, or i)ressure, i-eriuired to lUiiinlMin a certain cur- 
 rent strength in a circuit may be found by nuilfiplying the current in amperes 
 by the resistance in ohms. 
 
 (c) The resistance in any circuit may be found by dividing the electromotive 
 ff)rce by the current strength. 
 
 i> /• I ™ \ E M F (in volts\ 
 It (ni ohmH) = - ,-,. - — - v). 
 / (in amperes) 
 
 Wlien the total electromotive force is used in Ohm's law, the total rpsistance musi 
 be used to calculate the current strength. For example, if a coil of 0.5 ohm resist- 
 ance is connected to a cell of 2 volta E. M. F., the current through the coil would not 
 
 V 2 
 
 be ^ or =4 amperes as might be supposed. It requires a certain part of the 
 
 (2)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 . 3 
 
 cell's E. M. F. to force the current through the internal circuit; therefore, the inter- 
 nal and external resistances must always be added together and divided into the 
 total E.M.F. to find the current flowing. Now, if the internal resistance of the 
 above cell were 0.5 ohm, the total resistance would be 0.5+0. 5=^1 ohm and 
 
 F 2 
 /=— =— =2 amperes, or half of the first result. 
 K 1 
 
 Ohm's law applies also to any part of a circuit the same as to the whole 
 circuit. "When applied to part of a circuit care must be taken to use only the 
 E. M. F., resistance, and current strength of that portion of a circuit considered. 
 Therefore, when E is used as total E. M. F.. R nuist be the total resistance, and 
 when E is used as the pressure applied to part of a circuit, R to correspond 
 must be the resistance of that part of the circuit to which the E was applied. 
 This api)lication of the law may be illustrated by the followins problem : 
 
 The E. M. F. of a cell is 2 volts; its internal resistance 0.5 ohm. It is con- 
 nected to three .si)ools of wire in series. By measurement we find that the E 
 causing the current to flow through one of the spools, of which the 7^=0.4 ohm, 
 is 0.(5 volt. What current is flowing through this spool? 
 
 Bv Ohm's law / =^=-^ = 1.5 amperes. 
 h 0.4 
 
 Now, since the current is the same in all parts of a series circuit, 1.5 amperes 
 flow through each of the spools and also through the internal resistance. This 
 also illustrates the difference between the E. M. F. and potential ditference. The 
 difference of potential or pressure between the ends of the spool is 0.6 volt, while 
 the E. M. F. of the cell is 2 volts. 
 
 What part of the total E. M. F. is used in overcoming the internal resistance 
 of the cell in the above problem? 
 
 By Ohm's law E'^/X 7^=1.5 X 0.5=0.75 volt. 
 
 This gives pressure lost or " volts drop " inside the cell. 
 
 The resistance of any conductor increases with its length and decreases with 
 area of cross section and for most conductors the resistance increases with rise 
 of temperature. 
 
 Electric ciu'rent so far discussed in this maniial has been direct or unidirec- 
 tional as appertaining to its flow in a circuit and is termed " direct current." 
 (Abbreviated D. C.) This current may be so treatiMl that it will become either 
 alternating or pulsating in character. When* this occurs Ohm's law still applies, 
 but there are other factors that mu.st be considered in coniiniting values of 1.. 
 E. M. F., or R. 
 
 With an alternating current (abbreviated A. C.) the flow In a circuit is con- 
 tinually reversing in direction. Certain types of generators produce alternating 
 currents which change direction periodically and uniformly, the speed of rota- 
 tion of the rotor of such generators being constant. Such currents are expressed 
 in number of cycles per second, 60 cycles being the most conunoidy used for 
 commercial electric lifihting and power systems. Two alternations (chanjre of 
 direction) are contained in a cycle. 
 
 Unlike this current, the alternating current produced in telephonic comnni- 
 nication is not periodically \nuform nor is the E. M. F. in any way constant. 
 The E. M. F. of these alternating currents is usually extremely high and the 
 current sti'ength very low, consequently the source of the current for trans- 
 mitting the voice waves from a single instrument need only be capable of 
 producing a comparatively weak current strength. For this reason a person 
 
 (3)
 
 4 Signal Corps Manual No. 3. — Chapter 1 . 
 
 ciiiuiii^' into c<ml:icl willi lioth sitlt's of a talkiiifj; circuit will not l)c injured iiy 
 tlie talkinjr current. 
 
 A pulsating current is one whicii varies in niaj;nitu(le. As ordinarily em- 
 ployed the term refers to unidirectional current. A i)ulsatiug current may als(j 
 he formed by superimposing upon a direct current an alternating current. 
 A\'hen the altern^iting current is flowing in the same direction as the direct 
 current the former accentuates tlie latter, and when llowing in the reverse di- 
 rection it counteracts, in a degree, the direct current. 
 
 These curreiits will he (>ncountered in the study of the ojiei-ation of the 
 telephone and similar appai'atus. In (liai)ter 1^ of (his manual exjjlanation is 
 made of how they are jn'oduced. 
 
 Standard P>a itkkiks Stpplied hy the Signal Corps. 
 
 There are two classes of hatleries, viz. primary and secondary, the latter 
 being sometimes known as storage batteries or accunudatoi's. 
 
 Primary batteries are divided into two classes, known as oi)en-circuit and 
 closed-circuit, and while there is a great variety of each class, the basic ]»riii- 
 ciple employed is the same. 
 
 ( >pen-circuit cells are used f<_)r intermittent service where curr»Mit is required 
 for only short intervals of time, such as in operating electic bells. Open- 
 circuit cells kept in continuotis .service foi' some time become polarized or 
 completely exhausted but will recuperate to a considerable degree on open 
 circuit. 
 
 The dry battery is an excellent example of the oiien-circuit type. 
 
 Closed-circuit cells are. adapted for sttpplying current continuously until the 
 energy of the chemical is nearly (>xpiMuled. 
 
 This is the form of jirimary cell most extensively used in telegraithy. where 
 a small but constant cun-ent is re(|uired. 
 
 While f(»rmerly tlie Signal Cor]»s issued several difft'i'ent kinds of oi)en- 
 circuit itriniary battery cells, such as the Laclanclu'. (Jonda, and the Sampson, 
 all of which employed carbon and zinc foi- elements, salanuuoniac dissolved in 
 water as electrolyte and a conlaining Jar of glass. t'xi>erience has shown that 
 the di-y-cell tyi)e of jirimary battery is most satisfactory, and consequently 
 this tyi>e foiMus the standard issue of the Signal Cori)s. 
 
 While all dry cells ol' this ty|ie conform in general with the following 
 (le.sci'iption. it is found that different makes \ai'y in efliciency. In order to 
 ascertain the comparative merits of each make, a careful life lest is jyeriodically 
 made in the Signal Corps laboratory, Washington. 1 >. C. 
 
 The dry battery is a form of sal-ammoniac batter\ in which the zinc plate 
 consiiUHes i)oth the containing vessel and negative |i<ile, 1 hei'eby doing away 
 with the breakable gla.ss Jar. An absoi'beiit porous material with a dei>olarizing 
 mixtui'e .around it tills the space between the carbon in the center and tlie zinc 
 vessel. This porous materi.-il is salui-alc(| wiih a solution contaiinng chloride 
 of zinc and sal anmioiiiac. The top of liie cell is seaJed with asi)halt (»r similai" 
 material. I'.inding p(»sts for zinc and carlion elements, and pasteboard cover 
 t(» jirevent sliort cii-culliiiLr wilh adjacent cells, complete this form of battery. 
 These cells when carefull.\ manufactured and properly stored are reliable. 
 The cell can not be i-enewed, hut their low cost and the conveni(>nce affcu'ded 
 by iialui'e of the conslruciioii makes them superior jo the wet cell for general 
 use. When these cells are exhausted, a short jieriod of usefulness may be 
 obtained from llieni in the I'ollowiiiL: manner: ranch a number of holes through 
 
 it)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1. 5 
 
 tilt' zinc (•ontaiiiiii^^ case and |ila<t' (licni in Jars containing' a solution of sal 
 annnoniac and water. Sal( solid ion lor- lids imrposc may he used Inil it is not 
 as elToctivc as tlio sal ammoniac. 
 
 The standard sizes of the dry cell are shown in lijiure 1-2, hut it is pointed 
 out that only two of the.se sjzes are in ;4eiieral use with jiost teleithoue systems 
 and Willi insrrunients use<l hi ti»e field. 
 
 - v- 6i 
 
 OCZJ 
 
 TUNGSTEIN, TYPE A 
 
 Dimensions are for a^/ls a/.'-j 
 :Yiper cov?rinq rprnov?ct. 
 
 No,4-0 
 
 HL 
 
 No. 8 No. 6 No.4 
 
 Fig. 1-2.— BATTERY, DRY CELLS, STANDARD SIZES. 
 
 Size iS'o. G. lijrure \-l. is invariahly useil when a local hallery is desired for 
 telephones of post teli'phone .systems. 
 
 The tiintrsten tyju' A hattery shown in tijiure l-'J is used with the service 
 huzzer. the 1!)14 induction tele.irraph set. the camp telephone, radio test huzzer, 
 and the hand tlasldijiht. This type of hattery is similar in construction to that 
 described above hut in order tt) obtain a comparatively hifrh volrase with mini- 
 mum wei.fflit and bulk, the cells ;ire of small diameter and two cells are so 
 placed in a rii;id i)ai>er tube that they are connected in series. This combina- 
 tion uives a total voltaiic of o — 1 ■] beiiii: normal voltasre of eai'li cell. 
 
 RESKRVK TYCK DIJY CELT.. 
 
 The ordinary tyiie of dry cell deteriorates if kept lon.ir in storasre, even thouirh 
 not in nse. To jirovide a type of dry cell which could be kept in sioraire with- 
 
 (5)
 
 6 
 
 Signal Corps Manual No. 3. — Chapter 1. 
 
 out deterioration, tlie Signal Corps issues a dry cell known as ttie " reserve 
 type." sliown in figure 1-3. Tliis cell, although containing all the elements and 
 ingredients of an ordinary dry cell, does not become active until water has been 
 poured into a cavity of the carbon element. To place the cell in service, remove 
 the plug from the top of the carbon element and fill with water (rain water 
 preferred). As soon as this is absorbed, fill again, until the following amounts 
 of water have been added: Type 4-0, li ounces; type 5, 2i ounces; type 0. 
 3i ounces ; after which no more water should be added to these dry batteries. 
 
 Great care should be exercised in pouring the water, in order to avoid wetting 
 the cardl)oard cover. If no funnel is availalile it is advisable to remove card- 
 l)oar(l container during tilling. When tlie cell becomes wealc through \ise, a 
 little sal-anniioniae solution placed inside the cai-l)on element will rejuvenate it 
 to some extent. 
 
 FahneatocJK berminats 
 
 In no insCance'Shall Ht. 
 height above txiffy of-ttte 
 oeil exceed 4 
 
 No 6 No.4-0 
 
 'resolve:' 'reserve:' 
 
 Dinoensions are of cells with paper covennq pemored. 
 
 Fig. 1-3. -BATTERY, RESERVE DRY CELLS, STANDARD SIZES. 
 
 Referring to ligures 1-'J ;iud 1-;'.. it will l»e noted that the two sizes of 
 re.serve dry cells cori-espond in dimensions with cells of similar number not of 
 tiie reserve type, Tlie reserve tyi)e has i)ractically been adopted by the Signal 
 Corps. The Xo. 5 size is not a standard issue. 
 
 Tlie v(»ltage of a cell is important and should in no case be less than one volt, 
 but the internal resistance is of greater importance since the cell which is 
 nearly exhausted may at times show a conii)iiratively high K. M. F. 
 
 With an Jiiiinieler c(Hiiiecte(l directly to the leniiinals of a No. (> cell, new cells 
 should show a reading of at least 15 nniperes (some cells will show 124). The 
 voltage reading of a new cell on oj»en circuit should l)e at least 1.4. 
 
 .\iiiiiieter rejuUngs should be accomplished as (piicUl.v as jiossilile, as in milk- 
 ing the lest llie cell is jiractically short circuited, the olimic resistance of 
 ammeter being very low. 
 
 (6)
 
 Voltaic Cell, Ohm's Law, Batteries — -Chapter 1 . 7 
 
 Ordinarily, dry cells tested in iifcordaiu*' with tlic above wiiieli show a 
 voltage lower tliaii 1 or a reading of aniineter less than 2 should under no eir- 
 t innstances l»e turned into supply depots or transferred to accountable officers. 
 
 The above does not apply to the reserve type of cell unless it has been put in 
 cnnnnission l>y the addition of water. 
 
 Dry cells in good condition liave a voltage of about ].4."i. The internal resist- 
 ance and weights of the various types are aliout as follows: 
 
 Size. 
 
 Interna 
 resistance. 
 
 Weight. 
 
 Size Internal 
 resistance. 
 
 Weight. 
 
 4-0 
 
 Ohmx. 
 0.2.5 
 .25 
 .20 
 .20 
 .12 
 
 Ounces. 
 Ill 
 9 
 
 IS 
 
 :« 
 56 
 
 Ohmx. 
 8 0.10 
 
 Ounces. 
 SO 
 
 i 
 
 Reserve 4-0 .29 
 
 Reserv 5 .22 
 
 Reserve 6 .19 
 
 Type A tungsten " .30 
 
 Hi 
 18 
 
 
 ti 
 
 32 
 
 7 
 
 8 
 
 
 
 ' Internal resistance shown is for each cell of the unit. Weight shown is for the unit complete, including 
 cardboard container. 
 
 CLOSED-CIRCUIT BATTERIES. 
 
 The gravity, Fuller, and Edison are tlie types of closed-circuil cells sup- 
 plied by tlie Signal Corps. 
 
 Useful data on the above cells is shown in the following table: 
 
 
 Type of cell. 
 
 Voltage. 
 
 Weight. 
 
 Internal 
 resistance. 
 
 
 
 .- 1 - 1.00 
 
 Pounds. 
 115 
 
 12 
 11 
 
 Ohms. 
 3.0 
 
 Fuller . 
 
 
 2. on 
 
 
 
 
 . «7 
 
 .07 
 
 
 
 
 
 GRAVITY CELL. 
 
 This is the form of i)riinary cell most extensively used in telegraphy and 
 telephony when a small but constant current is required. The usual form 
 is sliown in figure 1-4. 
 
 These cells have been furnished previously in two sizes, each l>eing desig- 
 nated by dimensions of containing jar. One size is 6 by 8 inches and the 
 other is 5 by 7 inches. Tlie latter size has been recently adopted by the Signal 
 Corps as standard, and this size only will hereafter be issued. 
 
 In the bottom of the jar are placed three strips of sheet copper, riveted 
 together, as shown in figure, with a rubber-insulated wire attached to one 
 of the strips. There are many forms of zincs, but the " crowfoot " is the 
 form now almost universally used. 
 
 To set up the cell, place about 3 pounds of bluestone (svilphate of copper) 
 in the cell after putting in the copper, then hang the zinc and fill with 
 water. The bluestone should be allowed to settle without any attempt to 
 dissolve it by stirring or other means. The cell or cells are then " short- 
 circuited " (zinc and copper connected together) and allowed to stand sev- 
 eral days. By that time part of the bluestone will have dissolved, the blue 
 line being well defined. Above this will be a clear solution of sulphate of zinc, 
 formed by the action of the battery ; the sulphate of zinc, being of less spe- 
 cific gravity than the copper sulphate solution, will remain on top if the cell 
 is not shaken or stirred up. The battery may now be put into service. 
 
 (7)
 
 S Signal Corps Manual No. 3. — Chapter 1. 
 
 If in a hurry fur llie coll, it may lie .started off at once by stirring up about 
 a tablospoonful of .salt with the water before pouring it into the cell ; but 
 this method is apt to malce a battery dirty and considerably .shorten its period 
 of usefulness. Any long, dark masses forming on the lower part of the zinc 
 should be removed with a stick. The zinc sulphate solution will grow stronger 
 and stronger, until finally the -svhite salts will begin to creep or climb up llu' 
 sides of the jar and the zinc. As they will corrode the connections and ( aus*' 
 dirt and loss of insulation around the cells, they should be removed. IVIuch 
 of the trouble will be obviated if, as soon as they appear, part of the zinc 
 sulphate solution is drawn off with a battery syringe or a siphon made of 
 lient-glass tube, and watiM- juit in its i»lac(>. If the upper parts of the cells are 
 
 Fig. 1-4.— BATTERY CELL, GRAVITY. 
 
 Part 
 No. 
 
 Name. 
 
 lleference 
 No. 
 
 .Tar, glas.s 
 
 Crowfoot, zinc 
 
 Strips, copper v.'itli lead 
 
 Hluestone, 1 charge (3 pounds). 
 
 wanned an<l smeared wilh iiaraflin if will heli) mailers. I'.nt the besl jilan of 
 preventing evaporation and criH'iiing of salts is to use a good <piality of parallin 
 or lubricating oil, pouring on a layer about one-fonrlii inch (hick as soon as Hie 
 • ells are set up. In cleaning cells after that, wet cottnii waste (lipped in sand 
 will cIcMii tlio zincs, etc., of the adhering oil. As .soon as the bine solution goes 
 down below the level of the copjier more bhH>stone slionid be ailded. (/orrosion 
 oC the connections of the zincs with their wires shotdd be carefidly looked after. 
 It is betler to have routine insjiec-t ions of batteries made, and, if practicable, 
 instrumental tests ijiade wilh the voltmeters or voltaninieters. r>y (his means 
 deterioration may bi' acfiiiati'ly noted and many annoyances, breakdowns, and 
 delays which are fr<-(piently due to neglect and lack of regular inspection of 
 (he l»atterle.s may l>e av(»ided. 
 
 The internal resistance of a gravity cMl in good condition will be found 
 to be about 3 (duns, its E. M. F. 1 volt. 
 
 (8)
 
 Vdtaic Cell, Ohm's Law, Batteries — Chapter 1 . 9 
 
 ni.l.EU IJAITKUV. 
 
 Tills helonjis to the class poimlaily called " aeid batteries." The cell has 
 a hi^li electromotive foree, a eoinparalively low internal resistance ((>..") olun), 
 and is much used as transmitter battery on lonj;-distance heavily w(n-ked tele- 
 phones or local battery telephone switchboards. Its only disadvantafre is that 
 it uses a corrosive solution containinji suli»huric acid, necessitatinj,' nuich care 
 in handling. It consists of a glass jar about 8 inches high and 6 inches in 
 diameter, with a wooden cover treated with asphaltum or P. & B. paint. 
 (Fig. !-.">.) This supports a carbon plate ;ili«iul 4 inches wide, 9 inches long, 
 and one-t'ourth inch thick, with tlie (op c(iat<'d with pui-aHin to prevent the cor- 
 
 Fig. 1-5.— BATTERY CELL, FULLER. 
 
 Part 
 Xo. 
 
 Name. 
 
 Reference 
 No. 
 
 Jar, glass 
 
 Cover, wooden with carbon plate. 
 
 Porous cup 
 
 Zinc conical, with wire 
 
 Mercury, 2 ounces 
 
 Chromic, 1 charge (1 pound). . . . . 
 
 rosion of the connection liy the acid. In the jar stands an earthenware porous 
 cup 7i by 3 inches, in the bottom of which is placed about 2 ounces of. mercury. 
 In this stands a conical zinc cast to a copper wii-e which extends out at 
 the top. In the glass jar is placed the " electropoion " solution, luade by 
 slowly adding 1 pound of strong sulphuric acid to 9 pounds of distilled water, 
 and then stirring in 3 pounds of pulverized bichromate of potash or 2^ pounds 
 of bichromate of sodium. This last is preferable, as the crystals formed in 
 the action of the cell are not so hard and insoluble as those produced by the 
 potasli. In the porous cell with the zinc and mercury is placed water in 
 which about n tablespoonful of salt has been dissolved. This (;ell will usually 
 
 (9)
 
 10 
 
 Signal Corps Manual No. 3. — Chapter 1. 
 
 require little attention for three or four mouths. When the solution assumes 
 a muddy bluish tint it is about exhausted. 
 
 If the copper wire at its junction with the zinc is covered with paraffin or 
 ozite, or if the copper wire is well amalgamated by rubbing with mercury 
 after dipping it into acid, the wire does not tend to be eaten off at the junction, 
 as it otherwise does under heavy service. The Signal Corps issues the ma- 
 terials for the solution in <lry form, which when dissolved form the electrolyte. 
 This is purchased under various commercial names as chromac, voltac, chro- 
 mite, salts, etc., the first being the usual designation. It is packed in tin cans 
 with thin cut-out top, containing 1 pound, which is the amount for one charge. 
 Full directions for using are marked on each can. 
 
 The carbon of this cell lasts indetinltely, but should be soaked in warm 
 water when renewals are made. The zinc may last through several renewals 
 of the electropoion fluid. The mercury should be saved and used repeatedly. 
 
 The following table, cpioted from Alibdtfs Telepliony, indicates the effect of 
 age on efficiency of transmission with the Fuller cell. 
 
 Two-veil Fuller battery. 
 
 
 Volume of 
 
 
 Volume of 
 
 Age. 
 
 transmis- 
 
 Age. 
 
 transmis- 
 
 
 sion. 
 
 
 sion. 
 
 Days. 
 
 Per cent. 
 
 Days. 
 
 Per cent. 
 
 20 
 
 92 
 
 60 
 
 7(i 
 
 30 
 
 88 
 
 70 
 
 70 
 
 40 
 
 84 
 
 80 
 
 li2 
 
 50 
 
 80 
 
 90 
 
 54 
 
 From this it would appear that the (vlls nuist be renewed at least once in 
 three months when used on a telephone transmitter. 
 
 EDISON PRIMARY BATTERY. 
 
 The type V cell shown ui figure 1-6 is the standard Edison cell. As 
 previously manufactured for the Signal Corps, it has the same capacity as 
 the old Edison La Lande cells, but its enameled steel jar was slightly conical, 
 enabling the cells to be nested together for transportation. The caustic soda 
 and oil for each cell are issued in tin cans, so that there is nothing that will 
 not stand transportation. This cell has a very low internal resistance (not 
 exceeding one-eighth ohm) and will i-ciiiain s(>t up on open circuit for a long 
 time without ai)preciable depreciation. It has a capacity of about 1.10 ampere 
 hours, which means that it will furnish about 210 days' continuous service 
 on a line where the curn-nt is HO niilliamperes and 40 days' service when the 
 current is about O.ifi ampere. 
 
 If gives but 0.67 volt E. M. F. in stoady worU. 
 
 The following complete directions fur setting up. niMnagcmcnt, and ronewal 
 of these cells are furnished by the conii»any nianutactnring tlit-ni: 
 
 DIBKCTIONS FOR HKTTING IP AND USING KDISON PUIMAHY HATTKRY, KNOWN AS 
 
 EDISON CELL, TYPE V. 
 
 TO CHARGE AND CONNECT BATTERIES. 
 
 To wake Holutinn. — Fill tlic colls with water to H indies of the top. 
 Add the caustic sotla gra<lually to the water, stirring until the soda is en- 
 tirely dis.solved. 
 
 (10)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 , 
 
 11 
 
 When the solution cools, more water should lie added to hrln^ it up to li 
 inches of tlie top. Then pour contents of bottle of heavy paraflin oil from 
 bottle furnished for each jar on the solution. 
 
 NoTK 1. — The caustic soda will burn the skin and clothes. In stirring the 
 litiuid, avoid splashing it. 
 
 Fig. 1-6.— BATTERY CELL, EDISON PRIMARY TYPE V. 
 
 Jar, enameled steel 
 
 Cover for jar 
 
 Plate , oxide 
 
 Copper bolt 
 
 Copper nut 
 
 Thumb luit 
 
 Jamb nut 
 
 Double /-inc plate 
 
 Leather washer 
 
 Insulating tubes, hard rubber 
 Frame 
 
 C. 
 
 F. 
 
 G. 
 
 H. 
 
 N,A. 
 
 M,D. 
 
 Z. 
 
 E. 
 B. 
 
 To act up rrllfi. — Unscrew the nut .Y and the .ianil> nut V from the screw on 
 tlie brass neck of the double zinc jilate and remove tlie leather washer. I'ass 
 tlie screw from below through the central hole in the cover (\ lieplace the 
 leather washer and the .iamb nut .1/ on the screw and tighten down the jamb 
 nut until the zinc plate is rigid to tlie cover. The thumb nut .Y can then be 
 screwed on. ' 
 
 Unscrew the nuts A A and jamb nut /> from the screws on tin* two side 
 ])ieces B B of the co])per frame, leaving the tlat leather washers in i>osition 
 on the screws, and jiass the screws from below through the two round boles 
 in the cover (\ Keiilace the jamb nut on one of the .screws and one of the 
 Ihumb nuts on the other screw, and tighten both down until the frame sides 
 Jire rigidl.v clamped to the cover. lit^place the other thumb nut on the screw 
 holding jamb nut. Then slip the hard rubber insulating tubes E E over the 
 sides of the frame, one on each side. 
 
 To fill coiiinr f rallies.- — (In this cell only one oxide plate is used.) (See 
 fig. 1-6.) Slide the oxide plate /' suflicieutly far into the fi-ame to enable the 
 copper bolt (7 to be passed underneath it through the slots in the bottom of the 
 frame sides and the copper nut H tightened up on same. 
 
 4(3581^—17- 
 
 (11)
 
 12 Signal Corps Manual No. 3. — Chapter 1. 
 
 Be careful that the zinc plates do not touch the copper oxide plates or the 
 cell will he short-circuited. 
 
 The copper connection is made between the thumb nut A and the jamb nut 
 D on one end of tlie copper frame and the zinc connection between the thumb 
 nut A" and the jamb nut .1/ on the brass bolts suspending the zincs. 
 
 After the oxide and zinc plates are properly connected to the cover, as above, 
 soak them in water and while still wet insert in jar filled with caustic solution. 
 
 (Wetting the plates prevents the oil in jar from adhering to them.) 
 
 Important. — In order to allow the cover on the jar to fit easily, it is ad- 
 visable to wet the rubber gasket ring fitting into the grooved edge of the 
 cover by placing it in water. This will cause the cover to slip on easily and 
 will make the cell liquid tight. 
 
 It is absolutely necessary that the upper edge of the oxide plates should be 
 submerged at lea.st 1 inch below the surface of the caustic soda soluticin in the 
 jar ; also on no account can the layer of oil on top of the solution be omitted. 
 
 RENEWING. 
 
 When the cell becomes exhausted the solution and the remains of the zinc and 
 oxide plates must be thrown away. The renuiining parts can be used again. 
 
 TO TAKE THE CF.LLS APART. 
 
 Lift the lids, tmscrew the bolts, and remove the zincs and oxide plates. Wash 
 off (with water) the copper frames, bolts, and rubber insulators, brightening up 
 the metal where corroded with emery paper, especially the inside grooves of the 
 copper frame sides. I'our away the solution carefully and set up cells with new 
 caustic soda, oxide plates, and zincs according to directions. 
 
 Note. — In taking the cells apart the parts that have been immersed in the 
 caustic soda must be washed before they are handled. 
 
 TO ASCERTAIN IF THE OSIDiC PLATES ARE EXHAUSTED. 
 
 Pick into the body of the oxide plates with a sharp-pointed knife. If they are 
 red throughout the entire mass, they are comi)letely exhausted and need re- 
 newing. If on the contrary, there is a layer of black in the interior of the plate, 
 there is still some life left, the amount being dependent entirely upon the thick- 
 ness of the layer of black oxide still remaining. 
 
 COPPUR FliAME.S. 
 
 When renewing I he battery it is desirable 1o clean (he inside grooves of the 
 coitjier frames. wJiere the copper-oxide jtiates make conlact. so as to insure a 
 good electrical comiectit)n. This is es]teci;illy imi»ortant when* the batteries 
 iire recpiired to give a heavy current for caulery or motor itun><>ses. These 
 frames can be easily cleaned by wrapi)ing a small pi(>ce of emery paper around 
 a slick which will just lit into the groove, or by inmiersing lliem in a dilute 
 solution of 1 part of sulphuric acid and 4 parts Wiiter. iind then cnrefnlly 
 rinsing them in clean water to nMiiovt^ all traces of the acid. 
 
 (Uiution. — The oxide plates should never be remove<l from the caustic .soda 
 solution and allowed to dry in the air. as, if this is done, the surface of the 
 plates becomes oxidized by absorbing tlu> oxyg(Mi from (lie air, and the oxide 
 thns formed is mucii nn»re didicult of reduction than the original oxide of which 
 (he plates are formed. The internal resistance is consetiueiitly vei-y greatly in- 
 creased and the ciii'i'<'nt materially diminished. 
 
 .NoTK. — Where batteries are jilaced in warm plac(>s they should be examined 
 every (wo or three months to see (hat the solution has not evaporated, as this 
 will gradually lake i)lace, in sjiile of the oil, if they are in a Iio( room. If the 
 solntion is founrl to have evaporated, add more water to bring it again to the 
 I)roper height. It is of (he first im|ior(ance that all ))inding posls and connect- 
 ing wires should be kept clean and lii-iglil at the jioints of connection. 
 
 The (ype V cell is excelleni for nse as an ignition battery or in lieu of small 
 capacity storage batteries where no charging current exists. The Signal Corps 
 uses (his type of ba(tery quite extensively in comiection with the Alaska 
 Military ('able and Telegraph System. 
 
 (12)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 . 
 
 13 
 
 GROUPING OF CELLS. 
 
 When it is necessary to cause a certain current to flow through a con- 
 siderable resistance, as a long telegraph line, for instance, the necessary 
 E. M. F. is obtained by connecting cells in series — that is. the copper of one 
 cell to the zinc of the next, and so on until the requisite E. M. F. is obtained, 
 tlie relatively small increase of the total resistance due to the internal resist- 
 ance of the cells being of little effect. The total voltage is the sura of the 
 voltages of all the units so connected. But when it is desired to get a certain 
 current through a low resistance, another grouping must be made. The in- 
 ternal resistance of the ordinary gravity cell is about 3 ohms. And with 
 its one volt E. M. F. the current through a short thick wire of no appreciable 
 resistance connecting its poles will l)e one-third ampere. And if we have 100 
 
 Fig. 1-7.— BATTERY CELLS CONNECTED IN SERIES. 
 
 cells in series and connect the terminals of the entire battery, we would get 
 ifg ampere, or one-third, as before. For any number of these cells in series, 
 to obtain an increased current through low external resistance, we must cut 
 down tlie internal resistance of our battery. This, with a given type of cell, 
 may be done by linking them in parallel — that is, by connecting all the zincs 
 together and all the coppers together and then connecting the multiple zinc 
 and multii)lo copper thus obtained to the low external resistance. The E. M. F". 
 
 + 
 
 Fig. 1-8.— BATTERY CELLS CONNECTED IN MULTIPLE. 
 
 of tlu' battery remains the same as that of one cell, but the current output 
 is now e(iUMl to the sum of the current capacities of all the units .so connected. 
 
 Figure 1-7 shows four cells of battery connected in series and figure 1-8 
 shows four cells of battery connected in multiple, or parallel as it is sometimes 
 called. 
 
 In the first case we should get a current of ^^ = 1 ampere through our 
 short circuit; and in the second case, I=l^i=i ampere. 
 
 While in botli figures the gravity cell is shown, the rule is applicable to any 
 type, class, or make of primary or secondary battery cells. 
 
 (13)
 
 14 Signal Corps Manual No. 3. — Chapter 1. 
 
 Number and kinrl of hattcrij cells required by various apparatus. 
 (Where more than one battery cell is indicated the cells are invariably connected in series.] 
 
 Instrument. 
 
 Cell. 
 
 L. B. post-telephone switchboard i {puller ^ 
 
 Camp s\\-itchboard No. 6 reserve 
 
 L. B. telephone, pos^ telephone system do 
 
 Camp telephone ; Type A tungsten. 
 
 Service buzzer I.... .do 
 
 Induction telegraph set do 
 
 Test buzzer for radio pack set do 
 
 Flash-light , do 
 
 Number of cells. 
 
 3. 
 2. 
 2. 
 2. 
 
 1 unit (2 cells). 
 
 2 units (4 cells). 
 
 Do. 
 Do. 
 1 unit (2 cells). 
 
 I Either gravity or Fuller may be used for operator's transmitter circuit. In addition, 2 cells of No. 6 
 reserve may be used for night alarm. 
 
 Secondary Batteries. 
 
 The storage battery differs from the primary battery in its action in tliat 
 when it has given out all the energy the chemicals present enable it to supply, 
 instead of requiring new elements, the cell can be completely regenerated or 
 brought back to its original charged condition by passing a current into it in 
 a direction opposite to that in which the flow took place on discharge. 
 
 Although there are many combinations which can be used for storage bat- 
 teries, a large majority of those in commercial use and all those installed by 
 the Signal Corps are of the lead-sulphuric acid type, which in its basic prin- 
 ciple consists of two especially prepared dissimilar lead plates immersed in 
 diluted sulphuric acid. Each cell of the lead-sulphuric acid storage battery 
 has an E. M. F. of about 2.05. 
 
 The Edison storage battery which has recently been developed and placed on 
 the market makes use of oxides of nickel and iron in the positive and negative 
 electrodes respectively. The grids supporting the active material are made 
 of nickel-plated steel, and the electrolyte is a solution of caustic potash and 
 water. These cells when fully charged have a normal E. M. F. of 1.2 volts 
 and are charged at about 1.7 volts. They stand abuse much better than the lead- 
 sulphuric type of battery and are highly advantageous for vehicle purposes, as 
 it is claimed the output per unit of weight is nearly twice that of lead cells. 
 An idea of tlie ruggedness of this battery can be imagined when consideration 
 is given to the fact that when the battery becomes unhealthy or impaired by 
 liick of work, or t«»o nnich work, s'.iort circuiting tl\ebattery for a moderate pcritxl 
 will assist in returning the btittery to a healthy condition. 
 
 Secondary batteries in the form of storage battiTies or accunudators tire used 
 by the Signal Corps for supplying necessary cuiMcnt in coiuiection with com- 
 l)aratively large telephone systems, signaling systems. mihI teiegrapli systems 
 where a suitidile charging circuit is available. When used for sui)plying cur- 
 H'nt for the oi)eration of post telephone .systems, the system.s are invariably 
 what are termed "common-liattery" or "central-energy" systems. With this type 
 of .system the current for operation of all ai)paratus is obtained from one bat- 
 tery. Ill a local-battery telephone system llie swildiltoard and e;ich telephone 
 is e(|uijiiiei| with ;i l)attery. 
 
 Ill lii-c-(((iil i-o| systems :il seaconst defenses 1." cells of storage hatlery, con- 
 nected ill .series, are installe<l for siiitplying <-m'rent for operation of (he telephone 
 .system of (he fire-control system pro|>er. and in a great many in.stances (he same 
 battery furnishes current n«'ce.ssiny in the oj»erati<)n of the entire post 
 
 (14)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1. 15 
 
 t('lei)liono system. In emorgoiicy the saiue battery may also he used to siijiply 
 Jill signal apparatus of the fire-control system, which nornjally is supplied by 
 current obtained from a motor generator set, the motor generator set lieing 
 used to charge the storage battery when oiieration of tlie system is not in 
 progress. 
 
 Either a battery of 12 cells (jr a battery of 15 cells of storage battery, con- 
 nected in series, are installed for supplying necessary current for operation of 
 common-battery post telephone systems at interior posts. 
 
 General Data Concerning the Storage Battery. 
 
 The elementary form of storage cell is made by innnersing two lead plates 
 in dilute sulphuric acid. The principle inv(jlved in the storage cell is the 
 chemical action produced by a current which causes such changes of the 
 lead plates in the acid that upon cessation of the current, if the two plates 
 are connected together by a wire, a current will flow in the opposite direction 
 from the original one and the plates will tend to return to their original 
 condition. 
 
 The action of the current is to coat the plate that is connected with the 
 positive pole of the charging dynamo with pentxide of lead, and to reduce 
 to spongy metallic condition the surface of the plate connected with the 
 negative pole. When the plates are connected by a wire the peroxide coating 
 tends to be reduced back to lead and the spongy lead on the other plate to 
 become oxidized. The plates thus becoming alike the current will cease and 
 the cell is said to be discharged. Various methods of manufacture are in- 
 tended to give the plates more capacity; that is, to prepare more reducible 
 peroxide on one and more spongy lead on the other. The means adopted are 
 to make the plates up in the form of tine strips (tr grids of lead and till in 
 these interstices with the oxides of lead by various processes. These plates, 
 being made up in sets, are then innnersed in acid and given what is called 
 a " forming charge," after which they may be used. 
 
 The plates as receivetl fi'om the manufacturer are of two kinds. The 
 .sets of plates of one kind are of a chocolate brown, while the other sets are 
 of a grayish leaden color. When these are placed in the jars the .sets (jf 
 I)lates represent the zinc and copper, respectively, of a primary battery, the 
 gray plates acting as zincs and the brown as copper. In connecting cells in 
 series the brown .set of one cell should be connected with the gray .><et of an- 
 other, and so on. Care should l>e taken that no plates of different kinds touch 
 on the inside of cells, and that the separators are properly placi'd, if these 
 are furnished with the kind of cell use<l. The connecting lugs should all be 
 brightened before they are bolted t<tgether, and after all connections are 
 made it is well to go over them with a coating of cosmoline or sisphaltum 
 varnish. The cells should always be set up in a dry place, preferably where 
 there is a good means of lighting and where there may be ample ventilation. 
 
 The first or initial charge of any storage battery takes a nuich greater 
 length of time than the subsequent regular charges. The initial charge of any 
 make of storage battery shoxild be continuous if possible. With most bat- 
 teries it takes from 50 to 60 hours to complete the initial charge, while the 
 regular charge thereafter should be completed in approximately eight hours 
 at the normal rate. The battery should not be discharged below 1.70 volts 
 per cell. 
 
 Purity of electrolyte is of first importance in storage battery oi>eration, 
 and all acid should be tested where a douljt as to its purity exists. 
 
 (15)
 
 16 Signal Corps Manual No. 3. — Chapter 1. 
 
 TESTS FOR PURITY OF ELECTROLYTE. 
 
 The necessity for using pure electrolyte in storage batteries is sometliing 
 whicli is seldom recognized. Its importance in maintaining a battery in its 
 highest efficiency for any length of time is a matter which sliouhl receive 
 attention, not only at the time the battery is set up but subsequently, in the 
 addition of water or fresh electrolyte. 
 
 The most frequent impurities in water are sodium or magnesium chloride, 
 and some of the salts of lime and iron. The presence of lime will of course 
 be objectionable, but its presence in very small quantities is less objectionable 
 than that of the other impurities. 
 
 In general, it may be stated that the only suitable water for safety is 
 distilled water, and no amount of trouble necessary to get this kind of water 
 should be considered as too great when making up the electrolyte if strong 
 acid be furnished, or for subsequent additions to replace loss by evaporation. 
 
 Of course all dry reagents should be dissolved only in distilled water in 
 preparing for tests. Unless otherwise stated, the testing solutions should 
 be about one-half saturated. 
 
 If strong acid is furnished, the method of mixing this with the requisite 
 amount of water to bring the specific gravity of the solution to 1.210, is stated 
 later. It is urged that no aciil be useil which is made from iron pyriti's ; the 
 only suitable electrolyte is nuule from acid which is manufactured from pure 
 sulphur. 
 
 The impurities which may be in the acid, and for which tests shoiild be 
 made, are : Chlorides or free chlorine, the salts of iron, copper, mercury, and 
 the nitrates. Small cases of reagents may be furnished by the Signal Corps 
 for storage-battery installations where there are 15 cells and upward, and 
 tests should be made before setting up the battery and in subsequent addi- 
 tions of electrolyte if a doubt as to its purity exists. 
 
 It must be noted that after running some time the electrolyte may becinne 
 contaminateil with cldorides or nitrates from the plates, formed dm-ing man- 
 ufacture. 
 
 The sniallreagent cas(> (lig. 1-0) is furnished for testing t'li'ctrolyte. The 
 contents of tiiis case are shown in the parts list of tiu» illustration. 
 
 If distilled water is used, of course no tests <tf it will be necessary, but any 
 natural water should be open, to suspicion. 
 
 Tests for chlorine or ehlorUJes. — A few (h'ops of solution of nitrate of silver 
 in a test tube partly filled witli elccti-olyle will give a curdy, white precipitate 
 of silver chloride if chlorin(> or its salts are iiresenl. This chloride turns to a 
 violet tint on exposure to light. If the cleai- licpiid be jtoured off and strong 
 ammonia added to the white i)ri'cipitate, it w ill dissolve. 
 
 Test for iron. — The presence of ferrous salts in the ehvfrolyte is shown if a 
 dark-bine precii)itate is given upon the addition of a solution of the i-ed i)rnssiate 
 ol jHitassium. If fei'rif,- salts are i)resent in the electrolyte*, a solution of yellow 
 prussiate of jtotassiuni will give a blue tint, (^on.seepu'ully, if into two test 
 tubes, one of which contains a few drops of y<'llow ])rnssiale and the other a 
 few drops of red prussial(>, a little, electrolyte be poured, the two tests can be 
 made at once. If the impurities be ))reseiit in siii.-ill (|n:intilies there will not 
 be a precii)ilate formed, but a hluish-gi-een (•(ihii'al ion will i-esult. 
 
 Test for eopper. — Place a small (piantity of electrolyte in a test tube and add 
 an excess of strong ammonia. If coiii)er be present tliere will l)e a bright 
 bluish tint given to the mixture. If present in large (pianlities, a chocolate- 
 
 (16)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 , 
 
 1 
 
 colored substance will be formed upon the addition of a solution of the j'ellow 
 prussiate of potassium. 
 
 Test for mercury. — The luercurous salts will {^ive an olive-green precipitate 
 with iodiile of potassium ; the mercuric salts, a scarlet precipitate with the 
 same reajient. 
 
 Fig. 1-9.— CASE, REAGENT. 
 
 Part 
 No. 
 
 Name. 
 
 Reference 
 
 No. 
 
 Acid, sulphuric, 8 ounces 
 
 Aqua ammonia, 8 ounces 
 
 Bottles, stoppered, glass 
 
 Case, wooden 
 
 Diphenylamiiie, \ ouneo 
 
 Iodide of potassium, J ounce 
 
 Prussiat e of pot ash, red , h ounce 
 
 Prussiate of potash, yellow, i ounce. 
 
 Silver nitrate, i ounce 
 
 Tubes, reagent'] stoppered 
 
 Tubes, testing, 4 
 
 The use of hydrometers having mercury in the lower bulb will frequently 
 give a mercury impurity in the electrolyte through breakage of this bulb. Con- 
 sequently it is better to use only a shot-filled hydrometer. 
 
 Test for nitrates. — Some hiphenylamine slioidd l)e dissolved in a small quan- 
 tity of concentrated, chemically pure, sulpluu-ic acid and put in a test tube. A 
 small quantity of electrolyte is tlien carefully dropped in the same tube. If a 
 blue color results, nitrates or nitrites are present. Traces of nitrates are very 
 ob.iectionable. They cause a surprisingly rapid deterioration of the plates. 
 
 The following instructions relative to installing and initial charge of storage 
 batteries is furnished by the Electric Storage Battery Co., of Philadelphia : 
 
 (17)
 
 18 Signal Corps Manual No. 3. — Chapter 1. 
 
 UNPACKING AND CARE OF MATEKIAL. 
 
 1. Great care should be taken in the unpacking and subsequent handling of 
 the various parts of the liattery, as many of them are easily broken or bent out 
 of shape by rough handling. 
 
 2. Open the crates or packing boxes on the side marked "Up" and carefully 
 lift out the contents ; never slide out by turning crate on its side. 
 
 3. As the contents of each box or crate is removed, carefully count the parts 
 and check with the shipping list. A number of small parts will usually be 
 found in each shipment, and care should be taken to examine packing to make 
 sure that no parts have been overlooked. All material should be carefully ex- 
 amined for breakage. Cracked or broken jars must not be installed. No claim 
 for damage in transit will be considered and no claim for shortage will be 
 adjusted unless accompanied by a memorandum showing the number of case or 
 package, as a record of all cases by number is carefully preserved by the com- 
 pany, showing the exact contents of all packages, the contents having been 
 double-checlved before shipment. 
 
 4. The wood separators (sheets and dowels) which have been given a special 
 treatment are shipped wet, and they should be kept so until installed in the 
 battery, and not allowed to dry under any circumstances. If there is any 
 delay in setting up the battery, the sheets arid dowels should be left in the 
 packing cases and kept wet by being frequently sprinkled with water at least 
 once a week, the lid of the case being removed while sprinkling. If a supply 
 is to be kept on hand for any length of time, they should be kept completely 
 immersed in a vessel of water to which electrolyte of 1.210 specific gravity has 
 been added in the proportion, by volume, of one part of electrolyte to nine or ten 
 parts of water. The vessel (which must not be of metal) should be covered 
 to keep out impurities. 
 
 ELECTROLYTE. 
 
 5. The electrolyte shipped with a battery is dilute sulphuric acid of a specific 
 gravity of 1.210 or 2o° Baume (except fen* type I^ cells, see note) as shown on 
 the hydrometer at a temperature of 70° F. If it is not convenient to procure the 
 electrolyte from the Electric Storage Battery Co., already mixed and ready for 
 use, it may be prepared by diluting sulphuric acid of 1.840 specific gravity or 
 6G° Baume (oil or vitriol), which has been made especially for storage battery 
 use, with pure water (preferably distilled) in the pi"oi)ortion of one part acid 
 to four and one-third of water by volume; 1.4(10 specific gravity acid may be 
 reduced to 1.210 specific gravity by mixing equal volumes of the acid and pure 
 water. It is absolutely es.sential that both the acid and water should be practi- 
 cally free from inqiurities such as iron, nitric or hydrochloric acid. When mix- 
 ing, slowly pour the acid into the water (not the water into the acid) and 
 thoroughly stir with a wooden paddle. The final specific gravity must be 
 read when the solution is cool. A metal vessel nuist not be used for mixing 
 or handling the solution; a glazed (»r earthenware crock or a lead-lined tank is 
 suitai)le, or a wooden vessel which has not been used for any other purjiose. such 
 as a new wnshtub, can l)e used for mixing, hut not for storing the electrolyte. 
 1'lie electrolyte must be cool when ])oured into the cells. 
 
 Note. — For type D cells (fid! numlier of plates installed), when being first put 
 into conmu.ssion, electrolyte of I.ISO si)ecific gravity or 22° Baume must be \ised. 
 If the electrolyte is to be mixed on the ground, the proportions of acid (of 1.S40 
 .«;pecific gravity) and water an? one part acid to five and one-quarter of water, 
 by volume. I>in-ing the initial charge the gravity will rise to about 1.210 (the 
 slanrliird gravity). For type D cells (less than full number of i)lates installed) 
 electrolyte of 1.210 specilic gravity sliould l)e iised. 
 
 LOCATION OF IJATTERY. 
 
 0. The proper lociilion is inqxirtant. It should preferably be in a separate 
 room, which should be well venlihitcd, dry, ;ind of niodci-iit(> tt'mi)ei\Mtur<\ 
 
 7. The ventilation should be free, not only to insure dryness (in a damp 
 rooiri leakage from grounding is li;dtle to develoj), but to i)reveid chance of an 
 exitlosion, as the ga.ses given off dui'ing charge form an exitlosive mixture if 
 (•(infilled. F''or this reason never bring an ex]tose(l flame near the battery when 
 it is gassing. 
 
 (18)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 . 19 
 
 8. To obtain the best results, the room temperature should be between 50° 
 and 80° F. If the temperature is very high, that is, over 80° F., for any great 
 length of time, tlic wear on tiic philcs is excessive. If tlie teniperature is low, 
 no harm results, but tiie availai)ie capaeity is reduced during the period of low 
 temperature. 
 
 INSTALLING BATTEKY. 
 
 9. Before assembling the cells, suitable racks or stands should be provided 
 and so located in the room that each cell will be easily accessible. 
 
 10. Place the jars in the trays, which should previously be filled evenly with 
 the top with tine dry bar sand. Place the elements as they come from the pack- 
 ing cases on a convenient stand or table (the elements are packed positive and 
 negative groups together, the positive group having plates of a brownish color 
 and the negative of a light gray; also the negative group always has one more 
 plate than tlie positive grouji). Scrape both sid(>s of the lug at the bolt hole 
 to in.sure good contact when the cells are connected together. Cut the binding 
 strings an<l carefully pull the positive and negative groups apart. Remove 
 any loose or foreign matter and place the negative group crosswise on a strip 
 of webbing; then slip the plates of the positive group between tliose of the 
 negative group, so that the vertical edges of all the plates will be flush. (See 
 fig. l-I). ) The spacing sticks should then be inserted, as shown in figure 1-D, 
 in order to keep the plates apart while lifting. 
 
 11. Lift the element by the webbing and lower very cai'efully into the jar 
 (fig. 1-E), withdrawing the webbing and spacing sticks when the element is 
 properly in i)lace. Be sure that the hanging lugs rest evenly on the sides of 
 the jar. Lift the cell, together with the sanil tray, into position on the rack, 
 leaving an air gap of one-half inch between trays. Be careful that the direc- 
 tion of the lugs is relatively the same in each case, thus bringing the positive 
 lug and the negative lug of adjacent cells together. This insures the proper 
 polarity throughout the battery, bringing a i)ositive lug at one free end and a 
 negative at the other. If cells are connec-ted with wrong polarity, the plates 
 will be seriously injured. If wood sand trays (fig. 1-F) are used, put the 
 gla.ss insulators in place by first raising one end of the tray and then the 
 other end, the insulators being so located under the tray that they will be 
 directly luider the corners of the jar. Glass sand trays (fig. 1-E) have pro- 
 jections, or feet, on the bottom, and therefore do not recpiire insulators. 
 
 12. When all the cells are in position bolt the lugs together, first applying 
 vaseline or grease to the bolt studs. The nuts should be gone over and 
 tightened several times after the lugs are first fastened together, to insure 
 thoroughly good connection. At this time the connections with the charging 
 source (which must be available for charging) nnist be made ready. 
 
 13. The wood separntors can now be installed. Itemove from packing case or 
 water bath only suflicieut sheets and dowels for e(piipi)ing a f(>w cells at a time. 
 The dowels nnist always be placed on the sheets at right angles with — that is, 
 across — the grain of the wood. The separators, when eipiiiiped with the dowels, 
 should be inserted from the top (see fig. 1-F), one between each plate of the 
 element, the long, solid pointed end of the dowels in every case being downward. 
 Immediately after an element has been equipped with its sejiarators the cells 
 should be filled with electrolyte to one-half to three-quarters inch above tiiQ 
 top of the plates. An element with the separators in place must not be ex- 
 posed to the air any longer than is absolutely necessary. When the electrolyte 
 is in all the cells, place the glass hold-downis in position on the separators, 
 across the miihlle of the cell, and at right angles with the plates. 
 
 CONNKCTING VP THE CIIAKGING CIRCTIT. 
 
 14. Direct current only must be used for charging. If alternating current 
 alone is availaltle, a current rectifier must be used for obtaining direct current. 
 In connecting the battery for charging, the positive pole of the charging source 
 must be connected to the positive end of the battery, and likewise the negative 
 of the charging source to the negative of the liattery. If a voltmeter is not at 
 hand, the polarity may be determined by dipping two wires from the charging 
 terminal into a glass of water to which a teasjioonfid of table salt has been 
 added, care being taken to keep the ends at least 1 inch apart to avoid danger 
 of short circuits. Fine bubbles of gas will be given off from the negative pole. 
 
 (19)
 
 20 
 
 Signal Corps Manual No. 3. — Chapter 1, 
 
 Hard Rubber Pin to 
 support Separator 
 
 Hard Rubber Pin to 
 support Separator 
 
 1 
 
 r 
 
 Fig. 1-A. 
 Assembly of Typo F separator. 
 (See par. 13.) 
 
 Fig. 1-B. 
 
 Jliddle dowel 
 
 (sliowiiiiT 
 support pm). 
 
 A-> 
 
 -VssemMy oi Typo D and K sepa- 
 rators. 
 (See par. 13.) 
 
 Fig. 1-D. Fig. 1-E. Fig. 1-F. 
 
 (See par. 10.) (Sec par. 11.) (Sco pars. U and i;i.) 
 
 ASSEMBLY OF STORAGE BATTERY PARTS. 
 
 'J'dlilc of Vdlinns. 
 
 Tvpe 
 
 D. 
 
 
 
 r 
 
 
 
 
 
 T 
 
 
 
 
 
 
 Size of plates (not including lups). 
 
 3 
 
 31 
 
 12 
 
 6 by C inches. 
 
 73 by 75 inches. 
 
 11 by lOJ inches. 
 
 
 5 
 
 5 
 
 7 
 
 18 
 
 7 
 
 lOi 
 25 
 
 9 
 
 10 
 14 
 
 20 
 
 11 
 
 12.i 
 17.1 
 
 30 
 
 13 
 
 15 
 21 
 
 25 
 
 5 
 
 10 
 14 
 
 22 
 
 7 
 
 15 
 21 
 
 30 
 
 9 
 
 20 
 28 
 
 33 
 
 11 
 
 25 
 35 
 
 37 
 
 13 
 
 30 
 42 
 
 40 
 
 15 
 
 35 
 49 
 
 42 
 
 9 
 
 40 
 5li 
 
 30 
 
 11 
 
 50 
 70 
 
 32 
 
 13 
 
 00 
 81 
 
 42 
 
 15 
 
 Normal rate (amperes), clmrse 
 and disi^liarce 
 
 Ma.NJmum cliarKe rale (amperes). 
 
 Huii^'o in specific pravitv fapprox- 
 imal c) for complete cliscliar«e ' . 
 
 70 
 98 
 
 45 
 
 ' For exa 
 discharged 
 gravity. 
 
 mplo: If the specifie gravity of a tvt)0 K7 cell is 1 .207 wlion fully charged, it will bo completely 
 when the gravity lias fallen about 30 points (0.030 specific gravity), i. o., to about 1.177 specific 
 
 (20)
 
 Voltaic Cell, Ohm's Law, Batteries— Chapter 1. 21 
 
 INITIAL CHARGE. 
 
 [See table of rating.] 
 
 16. The charge should be started at tlie normal rate as soon as practicable 
 after all the cell.s are filled with electi'olyte and all the connections made, and 
 continued at the same rate until both the si)ecific gravity and voltage show no 
 rise over period of 10 hours, and gas is being freely given off from all the 
 plates. The positive plates will gas sometimes before the negative plates. To 
 meet these conditions, from 50 to CO hours' charging at the normal rate will be 
 reciuired ; if the rate is k'ss, the time rcMiuired will be proportionately increased. 
 In case the charge is intiTi-upted, jiarticulariy during its earlier stages, or if it 
 is not started as soon as the electrolyte is in the cells, the total charge requireil 
 (in ampere hours) will be greater than if the charge is continuous and started 
 at once. As a guide in following the progress of the charge, readings of the 
 cuiTent, specihc gravity, and voltage .should l>e regularly taken and recorded. 
 The gassing should also be watched, and if any cells are not gassing, or are 
 not gassing as much as the surrounding cells, they should be carefully examined 
 a nil the cause of the trouble removed. The temperatiu'e of the electrolyte 
 should be closely watched, and if it approaches 100° F. the charging rate must 
 be reduced, or the charge temporarily stojiped until the temi)erature lowers. 
 The .specilic gravity will fall after the electrolyte is added to the cell and will 
 then greatly rise as the charge progresses until it is up to the 1.210 or there- 
 about. The voltage of each cell at the end of charge will be between 2.50 and 
 2.70 volts, and for this reason a fixed or definite voltage should not be aimed 
 for. If the specific gravity of any of the cells at the completion of the charge 
 is below 1.205, or above 1.215, allowance being nuule fV)r the temperature cor- 
 rections (see below), it should be adjusted to within these limits, adding elec- 
 trolyte if low, and replacing some of the electrolyte in the cell with water if 
 high, keeping the surface at the proper height (one-half to three-foiu'tlis inch) 
 above the to]) of the ])lates. 
 
 TEMPEBATURE. 
 
 17. As the temperature affects the gravity, this nuist be considered and cor- 
 rections made as follows: To correct to normal temperature (70° F. ) subtract 
 one point (0.001 specilic gravity) for each 8° F. below 70° and add one point 
 for each o° F. above 70°. For instance, electrolyte, which is 1.213 at Gl° and 
 1.207 at 79°, will be 1.210 at 70°, It is of the utmost importance that the initial 
 charge be (ompleted in every respect. If there is any doubt, it is better to 
 (•barge too long than risk injury to plates by stopping the initial charge before 
 it is complete. 
 
 Whi](> the preceding directions may be applied to any make of storage bat- 
 tery, different manufacturers recommend slightly ditferent methods of pro- 
 cedure in the initial charge of their batteries, which should be carefully fol- 
 lowed, as this is ,the only means by whii-h they can be held responsible for 
 the conduct of their cells, which may be sold on guaranties. 
 
 INITIAL CHARGES FOR DIFFERENT ilAKES OF CELLS. 
 
 For a " chloride " battery the charge should be started at the normal rate 
 as soon as the electrolyte is in the cells (covering the plates about three-fourths 
 inch), and continued at the same rate until both the specific gravity and 
 voltage show no rise over a period of 10 hours and all the plates are gassing 
 freely. Electrolyte of 1.170 specific gravity is furnished for the type BT, CT, 
 PT, and D cells and of. 1.210 specific gravity for all the other larger types. 
 The positive plates will gas some time before the negatives. To meet these 
 conditions, from 50 to 60, hours continuous charging at the normal rate will 
 be required for the larger cells, while the types BT, CT, PT, and P3T require 
 from 30 to 40 hours for the initial charge; and if the rate is less, the time 
 required will be proportionately increased. In case the charge is interrupted, 
 
 (21)
 
 22 
 
 Signal Corps Manual No. 3. — Chapter 1. 
 
 particularly during its earlier stages, or if it is not started as soon as the 
 electrolyte is in the cells, the total charge requiriMl (in ampere hours) will be 
 greater than if the charge is continuous and started at once. 
 
 For this operation the Willard Storage Battery Co. rccoiumends as follows: 
 
 The charge must be commenced immediately upon filling the cells with elec- 
 trolyte of 1.200 specific gravity. The battery sliould be charged at a rate equal 
 to two-thirds of its normal or eight-hour charging rate. The charging should 
 
 Fig. 1 10.— BATTERY, STORAGE, CHLORIDE. 
 
 be continued until llic voltage of each cell is 2.(1 volts, the reading IxMUg tak(Mi 
 while the iiattcry is being charged at the above rate. After the cells have 
 reached the voltage named above, or higher, the charge sliould be continued 
 until tiie specific gravity of each cell ceases to rise, or has remained constant 
 for at least throe hoiii-s. This will usually happen after a battery has lu^en 
 charged f<»r a]ii»roximalely (iO hours. The experience of the Signal Corps 
 has i)een that a longer juriod of charge is re<|uired. If any cells do not show 
 the proper rise in voltage, or do not gas freely, they should be examined. Care 
 should be taken that there are no internal short circuits. If there are they 
 should be removed at once and the chai'ge continued until the cells indicate 
 us above. 
 
 (22)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 
 
 23 
 
 The Gould Storage Battfi-y Co. reconiineiuls tlie I'ollowiiij: proctMlure for the 
 initial charge of their batteries : 
 
 Fill the cells with the electrolyte furiiished which lias a specilie gi'avity of 
 1.210. Conuiience initial charge at twice the normal or eight-liour rate and con- 
 tinue for 12 hours, then reduce to 1.4 times the normal charge rate for 2(i 
 hours, then decrease to the normal or eight-hour rate and charge for 20 hours. 
 The specific gravity should he about 1.210 (corrected to temperature) at the 
 end of cliai"ire. 
 
 
 Fig. 1-11.— BATTERY, STORAGE, WILLARD. 
 
 In later paragraphs on the maintenance of storage batteries emphasis is laid 
 <tn the fact that storage batteries should not be allowed to remain in a dis- 
 cliarged state. This is because lead oxide immersed in sulphuric acid will be 
 chemically attacked, independent of any current tlow, and change into lead 
 sulphate, so that discharged plates tend to take on a coating of lead sulphate, 
 a nonconductor, impairing the efficiency of the cell as an accumulator. 
 
 (23)
 
 24 
 
 Signal Corps Manual No. 3. — Chapter I. 
 
 Various methods of manufacture are used to give tlie plates more current 
 capacity — that is, to expose more reducible peroxide of lead in the positive and 
 spongy lead in the negative plate to the action of the electrolyte. The various 
 methods (jf manufacture consist in changing the form of the grids and different 
 methoils of filling them Avith the oxides and spongy pure lead. Inasmuch as 
 neither of these have any mechanical strength in themselves, the grids or 
 frames are necessary to make up a suitable electrode. 
 
 <;lass covku 
 
 ^l.l^M;A•ro(; i;i;t.\i\i:k 
 
 ^-.«> 
 
 noi.T 
 
 CON'XECTOIl 
 
 WOOlj Si;i'\i; \T. I 
 
 M:(;.\ri\K uijui r 
 
 (•()\KR 
 
 I'asiTivL; (iijoi !• 
 
 (iLASS JAR 
 
 OAK S\NI) TUAY.WI'IH SAM) 
 
 (il, \SS INSULA roij.s 
 
 » 
 
 ri^;. 1-12. — BATTERY, STORAGE, GOULU. 
 (24)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 
 
 25 
 
 Different makes of .*;torajit' l)atteries are used by tlie Signal Corps. l)ut to 
 date practically all tliose used are of the lead types, made by the Electric 
 Storage Battery Co., known as the " Chloride " battery ; those made by the 
 Willard Storage Battery Co. and known as the " Willard ; " and those made 
 by the Gould Storage Battery Co., known as the "Gould" batteries. (See 
 tigs. 1-10, 1-11, 1-12.) 
 
 TABLE OF RATINGS. 
 
 The ampere-hovir capacity and sizes of batteries can be determined by the 
 table herewith, covering all the makes and types of storage batteries used by 
 the Signal Corps. 
 
 To determine the normal charge and discharge rates of a battery multiply the 
 " amperes per positive plate " for the particular type in question by the number 
 of positive i)lates i)er cell ; thus for a type F battery of 13 plates per cell (6 posi- 
 tive and 7 negatives) the normal rate is 60 amperes. 
 
 
 
 Type and number of plates. 
 
 Size of plates, not including lugs. 
 
 Normal 
 charge rate 
 (S hours) 
 per posi- 
 tive plate. 
 
 Gould. 
 
 Chloride. 
 
 Willard. 
 
 
 Manufac- 
 turers 
 type. 
 
 Number 
 of plates. 
 
 Manufac- 
 turers 
 type. 
 
 Number 
 of plates. 
 
 Manufac- 
 turers 
 type. 
 
 Num- 
 ber of 
 plates. 
 
 3 bv 4 inches 
 
 Amperes. 
 
 1^ 
 li 
 li 
 2' 
 2* 
 3' 
 4i 
 
 GGW... 
 
 CW 
 
 CL 
 
 2 
 3 
 3 
 
 BT 
 
 2 
 
 CC 
 
 2 
 
 
 
 
 
 1 
 
 
 5 bv 5 inches 
 
 CT 
 
 2 
 
 DC 
 
 2 
 
 
 CX 
 
 CM 
 
 CY 
 
 3 
 3 
 3 
 
 
 6 bv 6 inches . . . 
 
 D 
 
 PT 
 
 ET 
 
 }^ 
 
 3-13 
 2 
 2 
 
 5-15 
 
 
 
 5 bv 8J inches 
 
 BC 
 
 EC 
 
 E 
 
 2 
 
 
 2 
 
 7 J bv ~l inches 
 
 
 JCN i 3 
 
 \N' 5-15 
 
 CZ ! 3 
 
 5-13 
 
 5-15 
 
 8 bv 9 inclies 
 
 6 
 10 
 10 
 
 
 10'. bv lOV inches . . . 
 
 
 
 
 
 10* by 11 inches 
 
 F 
 
 9-27 
 
 F. ...... 
 
 ^27 
 
 
 
 
 In all of the above types, except the two-plate type, there is one more negative than 
 positive plate. All two-plate types have one negative and one positive plate. 
 
 ADUITIONAl, l.XSTKUCTIONS FOR ERECTING STORAGE B.\TTERIES. 
 
 Storage batteries, wlien received at storerooms, should be placed in a dry 
 location and an effort made to erect the batteries as .soon as po.ssible after 
 their receipt. When unpacked, preparations should be made to handle each 
 group of elements as a unit. After the lead elements are unpacketl. care 
 must be used in handling so that the plates and lugs will not be bent or 
 broken. This can be accomplished by lifting the plates with a stick placed 
 under all the lugs of each element, which can then be lowered carefully in 
 the jars. Care must be used to prevent breaking the tank or jar, or bending 
 the plates of supporting lugs. Types of storage battery racks suitalilp for 
 cells of the sizes installed by the Signal Corps are shown in figures 1-13 and 
 1-14. These can be made of any sound timber with the necessary strength, 
 which can be secured locally; all boltheads carefully puttied over, the whole 
 given several coats of acid-proof paint. The rack is then located in its 
 permanent position, and if the battery room has an asphalt floor, provision is 
 made for wide bases for the uprights of the rack to prevent them sinking 
 
 (25)
 
 26 
 
 Signal Corps Manual No. 3. — Chapter 1 
 
 into the floor. The rack .shouUl he carefully leveled before the batteries are 
 installed. The stringers must be of sufficient strength to support the cells 
 rigidly and perfectly level. The insulators should be placed, and the wood 
 tanks or sand trays and glass jars carefully aligned, care being taken that 
 they do not touch each other. If bolt connections are nsed, they should be 
 thoroughly cleaned by scraping. The strap lugs should also be scraped where 
 they will be in contact, and all connections bolted tight and then painted with 
 an insulating paint. The leads to the storage battery from the switchboard 
 room should be lead-covered cable if possible. The sheath should be cut back 
 about S inches from the end. The terminal lugs should then be sweated onto 
 the end of the conductor by filling the hole in the terminal lug with melted 
 resin solder, into which the wire is forced after being carefully cleaned and 
 tinned. The insulation and the shank of the lug is then carefully taped up 
 and given several coats of acid-proof paint. Where the lead rises from the 
 floor, loricated conduit can be used to protect it from injury. 
 
 The sand trays and sand must be carefully dried before being installed. The 
 trays can be dried by ordinary methods, but the sand must be baked for a 
 sufficient time to insure that all moisture has been expelled. Before com- 
 mencing the intitial filling of the jars with electrolyte, if wood separators are 
 
 5 
 
 CrtfcVr zurfact given bvo good coats of aad-proof paint 
 
 Hv r"^1 
 
 r^'i 
 
 'i'dc^yeJ qfuui and naitta 
 
 Fig. 1-13.— BATTERY, STORAGE, TELEPHONE, STAND FOR. 
 
 used, they should be installed and arrangements should be made to do the 
 work rapidly. A su(fi(ient number of glass or earthenware jars nuist be avail- 
 able so that several men can be engaged in the filling of the l)attery jars with 
 electrolyte. It is essential tlml tlic electrojyte l)e kept clean during this 
 process, and every precaution should be taken to that end. Electrolyte of the 
 proper specific gravity is furnished with each battery by the maker. Care 
 should be taken that a sufi'icient amount of electrolyte of the correct specific 
 gravity is available before the filling is connni'uced. It should be known with 
 ab.solute certainty that the reciuired i)o\ver for the necessary length of time 
 will !)(> availaitle before an initial charge is conuuenced. The maxinnim voltage 
 availaltle for <liarging should be at least 2.7.") volts for every cell to b(? charged, 
 and till" ami»eragc available lliat recpiired by the tyi»e of cell. 
 
 CAliK Ol' STOIt.\(lK li.MTKKIKS. 
 
 Kxcessive charging nnist be avoided. A battery should not be under- 
 charged, overdiscliarged, or let to stand completely discharged. 
 
 I')attery slionlil prefcraljly be charged at the normal rate. It is iiiii)ortant 
 tliat it should he sullicicnl ly charged, but the charge should not be <(>ntinued 
 beyond that jioint. I'.olli from the standi)oint of efficiency and lil\' of the 
 plates the best practice is tlie method which embraces what may be called a 
 
 (20)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 
 
 27 
 
 <cDOQiiJiLOi:4t>^Jj2ZOQ-OZQ: 
 
 46581°— 17 3
 
 28 
 
 Signal Corps Manual No. 3. — Chapter 1. 
 
 regular charge, to be given when battery is from one-half to two-thirds rlis- 
 fhargetl, and an overcharge to be given once every week. 
 
 A " pilot cell " should be selected, one that is readily accessible, and at the 
 same time representative of the battery as a whole. The surface of the 
 electrolyte in this cell must be kept at a fixed height, three-fourths inch above 
 the top of the plates, by adding a small quantity of water occasionally. This 
 cell is to be used particularly in following the charge and indicating when it 
 should be stopped. Where batteries are not equipped with the full number of 
 plates, the excess electrolyte in the pilot cell should be displaced by a properly 
 treated and weighted wooden block. 
 
 REOfLAR CIIAROE. 
 
 The normal rate should bo used throughout the charge when conditions 
 pei'mit ; but if it is necessary to hasten the charge a maximum charging rate 
 as given in the table which follows may be used during the first part of the 
 charge ; that is, until the cells begin to gas, when it should be reduced to 
 normal. Do not charge at a higher rate than normal after the cells are gassing. 
 The indications of sufficient charge are as follows : 
 
 (a) The gravity of the pilot cell having risen to a point which is five points 
 (0.005 specific gravity) below the maximum reached on the preceding over- 
 charge ; for instance, if the maximum reached on the preceding overcharge 
 was 1.209, the gravity to be reached on the regular charge is 1.204. If the 
 cells are but partially filled with plates and the excess electrolyte is not dis- 
 placed, the limit should be three points (0.003 specific gravity) instead of five 
 points (0.005 specific gravity). 
 
 Type. 
 
 Size of plates (not including lugs). 
 
 6 by 6 inches. 
 
 73 by 7J inches. 
 
 11 by lOJ inches. 
 
 Number of plates per cell 
 
 Normal rate (amperes) charge 
 and dischargp 
 
 Maximum charge rate (amperes) . . 
 
 Range in specific gravity (ap- 
 proximate) for complete dis- 
 charge ' 
 
 3 
 
 5 
 
 7 
 
 9 
 
 11 13 i 5 
 
 7 
 
 9 
 
 11 
 
 13 
 
 15 
 
 9 
 
 11 
 
 13 
 
 2.J 
 3A 
 
 5 
 7 
 
 7J 
 lOi 
 
 10 
 14 
 
 12h 15- 10 
 17i 21 14 
 
 15 
 21 
 
 20 
 
 28 
 
 25 
 35 
 
 30 
 
 42 
 
 35 
 
 49 
 
 40 
 
 56 
 
 50 
 70 
 
 60 
 84 
 
 12 
 
 IS 
 
 25 
 
 20 
 
 30 ! 25 22 
 
 1 
 
 30 
 
 33 
 
 37 
 
 40 
 
 42 30 
 
 32 
 
 42 
 
 15 
 
 • For examj)!)*: If 1 tie specific gravity of a type E-7 coll is 1.207 when fully charged, it will be completely 
 discharged when the gravity has fallen about ;iOpoinls (0.030 sp. gr.), i. e., toal)out 1.177 specific gravity 
 
 (h) The voltage across battei-y having risen to a point which is 0.05 to 0.10 
 volt per cell below what it was on the preceding overcharge, the charging 
 rale being I he same in both cases; for instanct*. if the maxinunn voltage it«>r 
 (I'll ;illain(«d on the overcharge is 2.52. the voltage per cell to be reached on 
 the regular charge is from 2.12 to 2.17 volts pin- cell. 
 
 (c) The cells all gassing moderately. 
 
 OVKRCMARCK. 
 
 Once ;i wi'fU. and preferably on the same day of the weel<, tli(> regular charge 
 shoidd be |)roloi)ge(l until the; conditions given below an^ fulfilled: 
 
 If rate is less than normal, the lime at maxinnnn imist be projMii-t ionately 
 increased. 
 
 («) The gravity of the jiijot cell luiving reached ii maximum, five successive 
 J5-minute readings of this ceil showing no fmiher rise. 
 
 (28)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1 . 29 
 
 (&) The voltage aci-oss battery luivinj,' reached a maximum, five successive 
 15-minute readings showing no furtlier rise, tlie cluirging rate being kept 
 constant. 
 
 (c) The cells all gassing freely. 
 
 As the temperature affects tiie gravity, this must be considered and correc- 
 tion made as follows: To correct to normal temiierature (70° F.). .subtract one 
 point (0.001 specific gravity) for each 3° F. below 70° and add one point for 
 each 3° F. above 70°. For instance, electrolyte, which is l.lil3 at 01° and 1.207 
 at 79°, will be 1.210 at 70°. 
 
 CiENERAL. 
 
 After the completion .of a charge and the current off. the voltage will quite 
 rapidly fall to about 2.0.5 volts per cell and there remain while <in open circuit; 
 falling to 2 volts when the disl-harge is .started. 
 
 Also, after the completion of a charge, particularly an overcharge, the .specific 
 gravity of the electrolyte will rise slightly, due to passing off of the gas bubbles 
 formed during the charge. For this reason ail of the pilot-cell gravity readings 
 must be taken before the charging current is cut off. 
 
 The voltage should not be allowed to fall below 1.75 volts per cell with cur- 
 rent at normal rate; the limiting voltage, however, is higher if the rate is less 
 than normal, and lower if the rate is above normal. 
 
 The specific gravity falls very closely in direct proportion to the ampere 
 hours discharged and can therefore be used as a guide in following the dis- 
 charge; thus, with the cells equipped with the full number of plates or the 
 pilot cell with a displacing block, the range in gravity from full charge to 
 complete discharge is as given in the preceding table. If the cells have not the 
 full number of plates and therefore have an excess of electrolyte, the range is 
 proportionately decreased, as is also the case where the capacity of the battery 
 has decreased due to normal wear or' to abuse. If the discharge is at higher 
 l-ates than normal, the gravity range is reduced in proportion to the reduced 
 atupere hour capacity at the higher rates. 
 
 The gravity and voltage limits are not necessarily reached at the same time ; 
 but either being reached, the discharge should be stopped. 
 
 The specific gravity of the pilot cell (or tjie battery voltage and current if 
 the pilot-cell method is not used) should be rea<l and recorded just before the 
 beginning and end of every charge ; also the temperature of the pilot cell at the 
 end of charge. 
 
 A specific-gravity reading of all cells should be taken and recorded once a 
 week, just before the start of charge on overcharge day and also, if the battery 
 is not overcharged weekly, at the corresponding time on the off w«'ek. If not 
 practicable to take these readings on overcharge day. they may be taken the 
 day before. In(livi<lual cell voltage readings are to be taken just before end of 
 overcharge with current flowing at normal rate. Open-circuit voltage readings 
 are of no value. 
 
 Just before the overcharge every cell should be inspected carefully, paying 
 especial attention to any cells noted as loir in the weekly readings. Make sure 
 that the hanging lugs are in place and not touching adjoining lugs; al.so any 
 peculiarity in the color of the plates slumld be noted. Near the end of the over- 
 charge all cells should be looked over to see that they are gassing freely. 
 
 In case a cell falls off in specific gravity or in voltage relative to the rest of 
 the cells, or shows lack or deficiency of gassing on overcharge as compared with 
 surrounding cells, or shows the color of the plates marke<lly lighter or darker 
 .than the surrouudiug cells, the cause should at once be determined uud remov^U. 
 
 (29)
 
 30 Signal Corps Manual No. 3. — Chapter 1. 
 
 Short' circuits are to be removed witli :i thiu strip of liard wood ; never use 
 metal. 
 
 If, after the cause of the trouble has been removed, the readinj^s do not 
 come up at the end of the overcharge, then the cell must be cut out of circuit 
 on the discharge, to be cut in again just before beginning the next charge. If 
 this does not bring it up, the process should be repeated. 
 
 Impurities in the electrolyte will also cause a cell to work irregularly. Should 
 it be known that any impurity has gotten into a cell, it should be removed at 
 once. In case removal is delayed and any considerable amount of foreign 
 matter becomes dissolved in the electrolyte, this solution should be replaced 
 with new immediately, thoroughly flushing the cell with water before putting 
 in the new electrolyte. If in doubt as to whether the electrolyte contains 
 impurities, a half-pint sample, taken at the end of discharge, should be sub- 
 mitted to the department signal officer for test. ' 
 
 The accumulation of sediment in the bottom of the jars must be watched and 
 not allowed to touch the plates, as if this occurs rapid deterioration will result. 
 To remove the sediment from type D and E cells, first prepare in a suitable 
 receptacle, such as a glass, earthenware, or lead-lined tank, enough new elec- 
 trolyte of 1.210 specific gravity to fill several cells. Starting at one end of the 
 battery, remove several elements, pressing the plates together to avoid disturb- 
 ing the separators; siphon or pour off the electrolyte, taking care to disturb 
 the sediment as little as possible ; clean the jars, examine element for dam- 
 aged separator's, and replace with new where necessary ; put the element back 
 and fill the cells with the new electrolyte at once, so that the elements will not 
 dry. Then add enough 1.400 specific gravity acid to the old electrolyte drawn 
 from these cells to bring it up to 1.210 specific gravity, so that it can be used to 
 fill the next two or three cells cleaned, and so on throughout the battery. The 
 1.400 specific gravity acid must never be added directly to the cells. Before 
 bolting cells together, the lugs should be well scraped at point of contact. At 
 completion of the work give a long charge until the gravity and voltage have 
 been at a maximum for from 5 to 10 hours. At the end of this charge read the 
 gravity of all cells and adjust where necessary to normal (1.205 to 1.215). 
 Type F cells, on account of their size and weight, can usually be best cleaned 
 by either the "scoop" or "water circulaticm "' metliods, though if care is exer- 
 cised the sediment can be removed as described above. 
 
 Note. — Very often it will be found that the depth of sediment is };r(>atest under the 
 middle plates, and if the sediment is leveled over the bottom of the eell its removal will 
 not be necessary for some time lonjrer. The leveling can bo done l).v usini; :ni L-shaped 
 device, which has no metal in lis construction. 
 
 Water only is lost by evaporation and nuist Ite rephiced with water. Do not 
 allow the surface of the electrolyte to get below the top of the plates; keep it 
 at its proper level (one-half to thr*ee-fourths inch above the top of the phites) 
 by the addition of pure water, which should be added at the beginning of a 
 charge, preferably the overcharge. It will not be necessary to add new elec- 
 trolyte, except iit long intervals or when removing sediment. To transjiort or 
 store the water, use clean glass or rub!)er vessels. Wooden r-eceplacles, if they 
 have not been used for otlier purposes, may also be used, but they should be 
 allowed to stand full oC water for a week before iise. In case of doubt as to 
 tlie purity of tlic wiitcr, ii quart s.-iiiipic sliotild be submitted for test. 
 
 Ordinarily it will not be iicccssaiw to add new electrolyte, except at long 
 intervals (once every year or two) or following removal of sediment. When 
 the si)ecific gravity of c<'lls in good condition at full charge and at normal 
 temperatui-e (70° F.) has fallen to 1.190, it should be restored to standard 
 
 (30)
 
 Voltaic Cell, Ohm's Law, Batteries — Chapter 1. 31 
 
 (1.20.") to l.*_'ir») hy till! addition of now electrolyte of 1.210 specific gravity 
 instead of water when repUiciiif; evaporation. If the' overcharge gravity is 
 considerably l»elow 1.190, as is sometimes the case after removing sediment, 
 the cpiickest way to raise the gravity is to draw off the electrolyte from one 
 cell, refill it with electrolyte of 1.210 specific gravity, and add siiJRcient 1.400 
 specific gravity acid to that drawn off from the first cell to raise it to 1.210, 
 then draw off the electrolyte from the second cell and refill with this 1.210 elec- 
 trolyte, and so on throughout the battery. Never under any circumstances add 
 electrolyte of higher gravity than 1.210 directly to the cells. 
 
 If it is not convenient to procure the electrolyte already mixed and ready for 
 use, it may be prepared by diluting sulphuric acid of 1.S40 .specific gravity or 
 G6° Baum<5 (oil of vitriol), which has been made especially for storage battery 
 use, with pure water (preferably distilled) in the proportion of one part acid 
 to four and one-third of water by volume; 1.400 specific gravity acid may be 
 reduced to 1.210 specific gravity by mixing equal volumes of the acid and pure 
 water. It is absolutely essential that both the acid and water should be practi- 
 cally free from impurities, such as iron, nitric or hydrochloric acid. When 
 mixing, slowly pour the acid into the water (not the water into the acid) and 
 thoroughly stir with a wooden paddle. The final specific gravity must be read 
 when the solution is cool. A metal vessel must not be used for mixing or 
 handling the solution; a glazed or earthenware crock or a lead-lined tank is 
 suitable, or a wooden vessel which has not been used for any other purpose, 
 such as a new washtub, can be used for mixing, but not for storing, the electro- 
 lyte. The electrolyte must be cool when poured into the cells. 
 
 When charging, those end cells which may have been successively cut into 
 circuit on discharge should be cut out again on the following charge as soon 
 as they are charged as shown by their gassing moderately. The cells which 
 were last cut into circuit on discharge will, of course, become charged before 
 th(jse that were first cut in. All the end cells, whether used or not, should be 
 cut Into circuit at the beginning of the overcharge and each cell kept in circuit 
 until it gasses freely, but no longer. 
 
 If the battery is to stand idle or be used at infrequent intervals, an overcharge 
 should be given every two weeks. Several storage battery companies have 
 advised that during such a jieriod exercising or discharging battery through 
 artificial resistance, which for years was the custom, is unnecessary and, in fact, 
 is a wear and tear on the battery. 
 
 If the use of the battery is to be entirely discontinued for a period not longer 
 than about nine months and it is not practical to charge at least once a month, 
 care should be taken that an overcharge is given just before the idle period. 
 Water should be added to the cells during the overcharge so that the gassing 
 will insure thorough mixing. The level of the electrolyte should be about one- 
 quarter inch from the top of the jars. After the overcharge is completed, 
 remove the fuses to prevent the use of the battery during the idle period. 
 Though not likely, the level of the electrolyte may, due to excessive evaporation 
 during the idle period, fall below the top of the plates ; if this should occur, 
 add water to keep them covered ; if in a place where freezing is apt to occur. 
 stir the electrolyte after adding the water, as thoroughly mixed electrolyte will 
 not freeze solid. 
 
 If the battery is to be entirely out of service for over nine months, then pro- 
 ceed as follows: After thoroughly charging, siphon off the electrolyte (which 
 may be used again) into thoroughly cleaned glass rceptacles, and as each cell 
 becomes empty inunedi;itely fill it with fresh, pure water. AVhen water is in all 
 
 (31)
 
 32 Signal Corps Manual No. 3. — Chapter 1. 
 
 the cells, allow the battery to stand 12 or 15 hours. Remove and throw away 
 the wood separators. Next siphon the water out of each cell, and the battery 
 can then he allowed to stand indefinitely. If there is any considerable amount 
 of sediment in the cells, it should be removed before it dries. 
 
 If the electrolyte has not been withdrawn, all that is necessary to place bat- 
 tery in commission is to add water, if needed, to the cells and give an over- 
 charge until the gravity of the electrolyte has ceased rising over a period of five 
 hours. 
 
 If the battery has been standing without electrolyte, proceed as follows : 
 Equip cells with new separators and fill with either new electrolyte of 1.210 
 specific gravity or, if the old electrolyte has been saved, add enough new of 1.210 
 specific gravity to replace loss. Charge for 3u hours at the normal rate, or for 
 a proportionately longer time at a lower rate. If the gravity after the first 
 charge is low, it should be restored to standard. 
 
 (32,
 
 Chapter 2. 
 TELEGRAPHY AND THE INDUCTION TELEGRAPH SET. 
 
 ThK MoKSK TkI.K(!UAIMI. 
 
 The two methods ol' Mi-ranfrini;; tiir onliiciry Mui-sc ciiciiils ;iiv culled tlie 
 " open " and " closed " cirouit systems. 
 
 The latter is frequently called the American system, a diagn'am of which is 
 shown in figure 2-1. In this oidy one line battei-y is necessary, although in 
 practice it is found better to divide tlie battery l)etween the terminal stations 
 as shown, care being taken hot to connect the batteries in opposition. Each 
 key is furnished Willi a circuit-closer lever, and when tlie line is not in use 
 the current is constantly flt)wlng, keeping the relays and sounders closed. 
 When operator at any station opens the circuit by means of the lever, he con- 
 
 Fig. 2-1.— telegraph SYSTEM. CLOSED CIRCUIT. 
 
 trols it entirely with the key. This system is In univiTsal use in the United 
 States and Canada. 
 
 A diagram of the open-circuit telegraph system is shown in figure 2-2. With 
 this system each station must have sutiicient main-line battery to operate all 
 relays in the circuit. The keys have a front and back contact fsee fig. 2-5). 
 When the line is not in use there is no current flowing and when operating key 
 at any station is depre.ssed, the back contact of that key is opened' and the 
 main-line battery to the front contact is placed in the circuit which operates 
 all relays on the line. The relay is sometimes placed in the line connected to 
 back contact, in which case the home relay is not operated. By this means the 
 resistance of the circuit is diminished approximately li50 ohms, which is the 
 resistance of the main-line relay. However, the American operator usually 
 prefers having the relay connected as shown in the diagram, so that the home 
 relay will operate, thereby operating the home sounder. 
 
 This system has been used exclusively on the short Signal Corps subma- 
 rine cables. It obviates the constant application of battery to the cable, 
 as would result from use of the closed-circuit system. 
 
 (33) 1
 
 2 Signal Corps Manual No. 3. — Chapter 2. 
 
 Telegraph Office Equipments. 
 
 Tlio familiar esstMitial instruments of tl't' ordinary Morse lolcj^raiili ollicc 
 need hut brief mention, as it is assumed that tlie reader is already familiar 
 witli the tirst principles of telegraphy. 
 
 Fig. 2-2.— TELEGRAPH SYSTEM, OPEN CIRCUIT. 
 
 The ordinary American Morse or closed-circuit key is shown in figure 2-3. 
 The lever .1 is ordinarily of steel nickel plated; the milled-head screw /•' 
 adjusts the tension of the sju-ing below it. O is the base which supports the 
 
 Fig. 2-3.— TELEGRAPH KEY, CLOSED CIRCUIT, LEG TYPE. 
 
 trumiioii bearings of the key. .1/ is the circuit-closer lever, which is i)iv- 
 oti'd al Ihe rear and slips undt r a curved melal piece »S', which is insu- 
 
 Flg. 2-4.— TELEGRAPH KEY, CLOSED CIRCUIT LEGLESS TYPE.
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 
 
 3 
 
 late<l from tlie base, l)Ut in connoction witli the front leg L. This front leg 
 is (•oiiiicctcd witii tlie ri-l:iy and tiie \nirk Ic^ // to tlie battt-ry or olln-r liiie 
 if it is a "way" ollitv. (' represents tlie uiipor ami lower C'onta<-t points of 
 piatiniuii, this iiictai resistiiii,' tlie corroding; action of the spark produced on 
 openin;^ the l^t'y. 
 
 The lejiless key is shown in fijjure 2-4. The binding posts instead of the legs 
 are connected to line and battery, respectively. The parts corresponding to the 
 leg key are siuiilarly lettered. 
 
 Fig. 2-5.— TELEGRAPH KEY, OPEN CIRCUIT, LEG TYPE. 
 
 The "open-circuit" key has an insulated front and an' insulated back contact, 
 and the circuit-closing lever is dispensed with. As shown in figure 2-5, the 
 screw C on the ba.se of the key is connected with the relay, the insulated lower 
 front contact, D, with the battery, and tlie insulated back contact, E. with the 
 ground at a terminal station or with the outgoing wire at a "way" station. 
 
 Tlie o]K'n circuit key, legle.ss type, may also be supplied. 
 
 THF, 1!KI..\V. 
 
 The function of the relay is, briefly, to cause a comparatively powerful local 
 current tlirough a sounder to be controlled by a much feeliler one in the main- 
 
 Fig. 2-6.— TELEGRAPH, RELAY, r.". 
 
 Lii 
 
 line circuit. The rehiy coils are inchnU'd in the main-line circuit, the two bind- 
 ing posts on tlie right (fig. 2-0) being connected with the key anil line, respec- 
 tively, the bintling posts on the left being connected with the s(»under and local 
 battery, respectively. The main and local circuits are indicated by the broken 
 
 (35)
 
 4 Signal Corps Manual No. 3. — Chapter 2. 
 
 lines. The resistance of the rekiy coils is now almost universally 150 ohms, 
 although on some short lines a "pony" relay of 20 ohms is used. 
 
 Fig. 2-7.— TELEGRAPH, BOX RELAY. 
 
 The box relay with the key on the base is shown in figure 2-7. This relay 
 has a heavier lever for giving a louder sound than that of the ordinary relay, 
 the resonance of the box assisting. As it may be used at temporary field offices. 
 
 Fig. 2-8.— TELEGRAPH, MAIN LINE SOUNDER. 
 
 when local batteries arc not (iltfaiiiablt>, and is of gri'at sfrcMigtli and simplicity, 
 it is a most useful instrument for military lines. 
 
 The "main-line sounder" (fig. 2-S) is somewhat of an improvement on the 
 box relay. The coils are usually wcuiid lo ITiO (tlniis, the same as other main- 
 tine in.strument.s. 
 
 The "pocket relay" is a c()mi)act I'di-m of main-line sounder for testing pur- 
 poses. About 40 milliamiicrcs curri-nl is i'c(|iiirc(l to oju'rate the ir>0-<)lmi instru- 
 ment to best advantage. 
 
 THK SOUNDER. 
 
 This well-known instrument is shown in figure 2-9, this being one of the 
 most common foi-ms now in use. Its connection with the relay and local battery 
 circuit has already been indicated. The coils are usually wound to a resistance 
 of 4 ohms, and it requires about oiic-fourth ampere to operate the sounder as 
 vigorously as is recpilred for ordinar.v ollices. Hence two bluestone cells, each 
 having about 1 volt 10 M F and 2 olniis internal resistance, will give the required 
 current. 
 
 (^J-^;. 25-2^2+4/ 
 
 (36)
 
 Telegraphy and tKe Induction Telegraph Set.— Chapter 2. 5 
 
 If the sounder is connected in circuit with colls of higher E M F an<l lower reeiat- 
 aQce, eome resistance wire should be inserted to keep the current down to one-fourth 
 
 Fig. 2-9.— TELEGRAPH, 4-OHM SOUNDER. 
 
 ampere; otherwise the battery will be iised up wastefully. For example, with a Fuller 
 
 1 8 
 cell of 1.8 volts E M Fand one-fourt hohm internal resistance, 7=j--j— =.42 ampere, 
 
 which is considerably more current than necessary. The necessary added resist- 
 
 1 8 
 ance, X, can be found as follows: Required current is .25 ampere, so .25= ." „ 
 
 4+i+A; 
 
 1.06+. 25 X=1.8; X='i ohra.«. the '"dead resistance" to be introduced in circuit. 
 
 In cii.ses when a nunilier of sounders are fed from one storage cell, a " dead 
 
 resistance" of 4 olnns .should be inserted in each sounder circuit, as the storage 
 
 ceil lias virtually no internal resistance and an E. M. F. of 2 volts. 
 
 SWlTCimOAUDS. 
 
 These are either terminal or intermediate in their use, and as there is con- 
 siderable difference in extent and character of the wiring they will be con- 
 sidered .separately. 
 
 The intermediate or way-station switchljoard is repi-esented in simplest 
 form in figure 2-10. Suppose two lines coming into a station are brought to 
 
 Fig. 2-10.— TELEGRAPH SWITCHBOARD, INTERMEDIATE. 
 (37) 
 
 :iGi567'
 
 6 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 tlie tops of the verticiil strips of ln-iiss. ;is .shown, usually throui;h lightning 
 arresters. Between these vertieal strips of brass are vertical rows of brass 
 disks. ;ill the disks in any horizontal row being connected together by a metal 
 strip on tht' back of the board. Semicircular spaces are cut atljoining each 
 other in the strips and disks so connections may be made at any of these 
 points between the disks and strips by the insertion of conical metal plugs 
 with hard-rubber heads. By means of these, sets of instruments may be con- 
 nected up with each other, the different lines, or the ground. To cut out a 
 set of instruments insert plugs at 21 or 22. To cut in the upper set on line 
 No. 1 take plug out of 21 and insert plugs at 4 and 5 or 3 and G. To cut 
 upper set in on line No. 2 remove plugs from 3, 4, 5, 6, and 22 and insert them 
 at 13 and IG or at 14 and 15. In a similar manner the lower set of office 
 instruments may be cut in on either line. 
 
 Suppose either of the home sets is cut in on No. 1 line and an open circuit 
 in the line develops. To ascertain whether the open circuit is east or west 
 of the station proceed as follows : Insert plug at No. 2. If communication is 
 established the defective line will be east of station. If comnuinication is not 
 established insert plug at No. 1, when communication will be established with 
 .station east of home station unless both lines are open. The foregoing illus- 
 trates the use of the ground wire. 
 
 Due to defects in one of the lines, the main office may desire a " patch " 
 made. This means that it is desired to cross connect lines 1 and 2. Suppose 
 the chief operator directs that line No. 1 west be connected with line No. 2 
 east. Of course it is desired to keep one of the sets cut in at this oflice on 
 this i)atched line. 
 
 Plugs are inserted at 3 ami IG and ail otiier 1)1u.l;s ai-e removed. 
 
 To patch No. 1 east with No. 2 west, put i)Iugs at 4 and 15. 
 
 To loop No. 1 west with No. 2 west, put plugs at 3 and 15, if desired to 
 leave instrumenis in. II' desired in k'ave them out, insert ]ilug at ll> instead 
 of at 15. 
 
 If directed to ground tliis looj), as may be needed sometimes in testing, insert 
 a plug at either 1 or 11. 
 
 The simi)lest foi'ni of ofliee switch, called a i)lug cut-out, i.s* shown in figure 
 2-11. The lini> wires come in from above, the wires to instruments come out 
 
 Fig. 2-11.— TELEGRAPH, PLUG SWITCH AND LIGHTNING ARRESTER. 
 
 iielow. and llie cenlral wire leads to ground. Tli«> insertion of the plug in 
 the lower holes groinids " cast " oi- "wesi," .-md when in the >ij)iter hole cuts 
 out the .statittn. The central ;;round jiliile near the line strips acts as a 
 lij;htninu arrester. 
 
 (88)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 7 
 
 LIGHTNING ARRESTERS. 
 
 The principle in seneral nj)on wliich tliesf aiv nuule is to itrinj: tlio line 
 or some of tlie first metal parts to wliich it is coiinocted in tlie odice rlose 
 to a conductor connected directly to the ground. Tlie lij,'htninn jumps to this 
 ground coiuiection instead of going througli the instruments. Tliese arresters 
 are frecpiently parts of the switchboard, consisting of a metal plate connected 
 to the ground, extending across the vertical line strtips and not quite touching 
 tliem, or of a series of I)rass disks extending closely over tlie stra)ts. the dislvs 
 l)eing all connected fo tli(> gi-ound wire. A simple form of arrester is shown 
 in tigiu-e li-ll, lieing part of the plug cut-out. 
 
 Tlie Mason llglitning arrester, fully described in chapter C, of ibis niamial, 
 is sometimes used in protecting telegraph apparatus, and cables where connec- 
 tion is made to aerial llne.s. 
 
 Terminal Ofiick Switchhoaiu) and IIattkuy Ai;kan(;kments. 
 
 The general jilan of the terminal swltcliboard is shown in ngure li-12. intro- 
 ducing a row of spring jacks at the bottom of the board. Tlie method of utili/-- 
 ing these in cutting in sets of instruments by insertion of the double flat plugs 
 is shown. These flat plugs, with hard-ruliber insulation between the metal 
 strips composing them, are connected with flexible insulated double-conducting 
 cords leading to the sets of instruments. It will be seen that each line comes 
 in through a fuse wire to the top spring contact of the jack, and, if no plug is 
 inserted, passes through the back contact and up to one of the vertical straps 
 of the board. The insertion of a round conical plug at the appropriate disk 
 connects it to the battery and ground. The insertion of a flat plug and cord 
 leading to a set will introduce that instrument into the circuit. The various 
 arrangements for interconnecting, the provision for duplex and repeater sets, 
 
 13 K- 15 IS 
 
 2DISCI9 
 
 Fig. 2-12.— TELEGRAPH SWITCHBOARD, TERMINAL TYPE. 
 (39)
 
 8 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 and the connections for loop switches can be studied out, especially if the 
 reader will consult Maver's American Telegraphy and Jones's Pocket Edition 
 of Diagrams, etc., both of which have been consulted in preparing the diagrams 
 and above descriptions. 
 
 As most modern terminal and repeating offices are now provided witli storage 
 battery and dynamo sources of current, the method of supplying the terminal 
 switchboard and its connecting lines will be described in the general scheme 
 outlined in figure 2-13. 
 
 With the wire E F disconnected and the + and — mains connected as shown 
 in the dotted lines, the cells are connected to the dynamo in two rows in parallel 
 for charging. When completely charged they are disconnected at C and D and 
 reconnected by E F. This puts the GO cells in series again with the negative 
 end to ground. At various points (10, 20, 30, etc.) taps are taken off, through 
 incandescent lamps introduced as safety resistances, to various horizontal rows 
 of disks on the switchboard. Tims, beginning at the top, this row of disks is 
 at the highest potential (120), and a conical plug inserted, connecting any disk 
 of this row with the line leading to the vertical strap through the jack at the 
 bottom, will give the strongest current, and so on down the rows to 10. which 
 brings into the circuit only the last 5 cells next to the grounded end of the 
 battery. The low internal resistance of the storage battery permits feeding 
 almost any number of lines out of the same row of cells without interference. 
 The introduction of lamp resistances is necessary because of this low internal 
 resistance of the cells, as a grounding of the line close to the terminal office 
 would otherwise cause a current dangerous to the instruments. The amount 
 of lamp resistance to be inserted at each potential is, according to Jones, in his 
 
 Switchboai^d 
 
 jo; 
 
 p 
 p 
 p 
 p 
 p 
 p 
 p 
 p 
 p 
 b 
 
 Ij 
 
 +1 120 Volt s 
 
 ■— W 
 
 I 110 
 
 I 
 
 100 
 
 60 
 
 . 1^ /--^iHiiii 'iN'l'l'NTl'l'l'l'l'l'N1'l'l'l'l'l'l"l'|fF 
 iS^ + — D 
 
 
 50 -\- 
 
 II 1 1 1 1 11 1 
 
 40 
 
 I I 11 I I I I 
 
 30 
 
 20 
 
 I III 
 
 /O 
 
 li 1 1 |^=Y 
 
 Fig. 2-13.— TELEGRAPH SWITCHBOARD, POWER CONNECTIONS. 
 
 Pocket Edition of Dingrnnis. etc., 2 ohms for each volt. One ordinary 16- 
 candlepower liimp would he iiliout right for (he 110-volt poteiithd, and two of 
 thc.'ic in parallel for the TiO-volt potential. 
 
 (40)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 
 Telegkai'h Repeaters.' 
 
 THE MILLIICEN REPEATEU. 
 
 This was one of the earliest repeaters introihir-ed into the telegraph .service, 
 and it is still a standard repeater of the i)rinclpal telepraph conii)jinies of 
 this country. The Siirnal Corps has a nunilter in use in connection with 
 telegraph lines in Alaska. 
 
 This repeater may iiiMliaps he termed an automatic electromechanical re- 
 peater, lor, while electricity is the control liiii,' force in the performance of 
 its automatic functions, the ultimate action is mechanical. 
 
 Figure 2-14 is a theoretical diagram of the connections of the Milliken re- 
 peater. R and R' are the main-line relays. EM and FAI' are extra magnets, 
 
 1 The descriptions and diagrams of the Milliken and Weiny repeaters are taken by per- 
 mission from Maver's American Telegraphy. 
 
 (41)
 
 10 Signal Corps Manual No. 3. — Chapter 2. 
 
 ■which in practice are supported on metal standards that liold them rigidly 
 in their respective positions relative to the main-line i-elays. The armature 
 levers of the extra relays are pivoted at the top as shown. T and 3" are 
 transmitters. The levers L h' of the transmitters are insidated from the 
 tongues X x' at points i i' and from screw posts F F' hy small pieces of hard 
 rubber. 
 
 The working of this repeater may perhaps be best described by assmning that 
 the east is about to send. To that end he opens his key ; that opens relay R' and 
 its lever V falls back, as in the figure, and opens the local circuit controlling 
 the transmitter 7". As the latter instrument opens, it breaks the local circuit 
 of FM at a' ; the retractile spring 8 of extra magnet EM at once pulls its lever 
 against the lever I of relay R as in figure, and the transmitter T' opens the 
 western circuit at x' ; this demagnetizes relay R, and its spring would withdraw 
 its lever I from its front stop /, thereby opening the transmitter T, and conse- 
 quently the eastern circuit at x, but that, as already stated, the lever of EM is 
 against lever I, holding it on its front stop, and thus keeping the local circuit 
 of T closed. AYhen the east again closes his key, relay R' also closes; conse- 
 quently so does T' . This action closes EM, and the lever of that intrument is 
 withdrawn from its position against the lever R. This releases R's lever, but, 
 as now the western circuit is closed at x' , the lever / is held forward by its 
 armature. 
 
 In this way the function of the repeater in keeping closed the opposite trans- 
 mitter, and virtually also the circuit which is being "repeated" into, is per- 
 formed. 
 
 Should the west now desire to " break " or send to the east, he opens his key, 
 which action, by opening the local circuit of transmitter T at F, opens the 
 eastern circuit at x. The east, finding his circuit now open, closes his key to 
 await the remarks of the west, when the "repeating" actions just described are 
 reversed. 
 
 THE MEINY EKl'EATER. 
 
 Tliis repeater, which is in operation on the lines of the United Press, the 
 Postal Telegraph Co., and Signal Corps, is shown in figure 2-1.1. The opposite 
 transmitter is kept closed at the repeating station by the action of an 
 extra magnet added to the main-line relays, the construction and operation 
 of wlucii is, briefly, as follows: Tlie extra magnet is wound, as shown, Avith two 
 coils, through which a current fiows from a local battery in opposite directions 
 around the core, so that the latter is normally not magnetized. When, how- 
 ever, one of these extra coils is opened the current in the other coil magnetizes 
 the core. The wire which is joined to both coils of the extra magnet goes 
 directly to tlie ri^ht-hand end of the opposite local battery. The other end of 
 each coil passes to the other jmlc of the same battery, (uic coil by way of the 
 left side of frame and the other by way of the lever of the opposite -trans- 
 mitter, as sJiown. This lever is insulated from the left-hand post when the 
 transmitter is open, (^onsetpiently, when the left-hand transmitter is open, as 
 in figure, the circuit of the left-hand coil of the extra magnet of the eastern 
 relay is open at the left-liand post of the western transmitter, and as a result 
 thereof that extra magnet is magnetized by the current passing through the 
 right-band coil, and licence the armatuic lever of th.il n^lay is held against its 
 front sloj). Thus, for exairiple, when, as in the figure, the west sends to the 
 east, and thereby opens his key, the western relay in the repeating office opens 
 and its armature lever falls back, o])eniMg the local circuit of the western trans- 
 
 (42)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 
 
 11 
 
 niitter. As this transmitter opens it first breaks, at its left-hand post, the cir- 
 cuit of the left-hand coil of tlie extra magnet of the eastern relay, and next 
 opens the eastern main-line circuit at the right-hand post. As, however, the 
 armature of the eastern relay is ivcpt closed in the manner stated by its extra 
 magnet, the eastern circuit remains unbroken in the repeating station. 
 
 
 i I ^_^_ i , 
 
 The local battery, it will be seen, is also utilized to operate its respective 
 transmitter. A button switch is phiced on the base of each transmiter for the 
 purpose of short-circuiting the main-line contact points on the transmitter 
 when it is desired to use the transmitter simply as a sounder for the relay. 
 
 Figures 2-16 show the circuits of a telegraph repeater which is usetl in rej^at- 
 ing signals from open-circuit telegraph systems to closed-circuit telegraph 
 systems, or vice versa. 
 
 46581°— 17 
 
 (43)
 
 12 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 Operation. — The illustration shows the normal position of all instruments 
 when receiving. 
 
 To send from open-circuit station, move tlie two-point switch to battery ; this 
 puts current to line through back contact of key. Close the key ; this takes 
 battery from line, thus permitting the spring to withdraw the armature from 
 
 0=0^^ 
 
 T C/osed Circuit 
 
 i: StaUon 
 
 Fig. 2-16.— TELEGRAPH REPEATER CIRCUITS FOR O. C. AND C. C. OPERATION. 
 
 relay No. 2, closing the local .rounder circuit at its baclv contact. At the same 
 tin)e relay No. 4 is deenergized, permitting its armature to close the circuit for 
 the closed-circuit station at its back contact. Thus it is seen that closing the 
 open-circuit key causes its sounder to close, at the same time closing the distant 
 closed station. Now open the open-circuit key. This puts the battery to line, 
 which causes the armature of relay No. 2 to be attracted, which opens the local 
 circuit of its sounder ; at the same time the armature of relay No. 4 is attracted, 
 which opens the circuit for the open-circuit station. Thus it is seen that a signal 
 at the open-circuit station is reproduced at the closed-circuit station. When 
 through sending, move two-point switch to the other stop — to ground. 
 
 To send from the closed-circuit station, open the key, which opens the local 
 sounder circuit ; at the same time relay No. H is demagnetized, thus permitting 
 its relay to clo.se a local circuit at its back contact. A local battery energizes 
 relay No. 3, which attracts its armature, thus closing a circuit for a battery 
 to energize the open-circuit station, relay No. 2; this opens the sounder circuit 
 at that station. 
 
 Now close the key. This closes the local sounder circuit; relay No. 5 attracts 
 its armature, thus opening the local circuit for relay No. 3. The latter is thus 
 deenergized and permits the retractile spring to withdraw the armature from 
 Its front contact, tbus eliminating all battery from tlie open-circuit line; then 
 relay No. 2 permits its iiniiiilui-c 1<i cIdsc the DiKMi-circnit sounder circuit at 
 its back contact. 
 
 It is now seen that signals sent fnmi fillicr sliilion arc aulimiatically repeated 
 to the other. 
 
 (44)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 13 
 
 The two lines are always in an oppoate electrical state, which tiioy shoulil be. 
 
 The closed-circuit station has the ordinary apparatus. 
 
 The open-circuit station must reverse the contacts of its relay ami connect 
 battery to line on its !)ack contact; also, it requires a two-way switch to <ut out 
 battery when not sending;. 
 
 If desired, a combination key may be utilized for the ordinary oi»en-circuit key ; 
 in this case he two-point switch shown, is not required. 
 
 For best results relay No. 5 shoiUd be the same kind as No. 6. Also rehiy 
 No. 4 should be the same kind as No. 2. No. 3 may be of any desired resistance 
 or nature, as it is on an independent local circuit. 
 
 No. 5 relay is in the closed-circuit line, and No. 4 relay is in the open-circuit 
 line. 
 
 The local sounder battery at the open-circuit station nmst be a closed-cinuii 
 one. The other butteries are all of the open-circuit type. 
 
 The followin.i; should i)t' observed in tiie adjustment and care of telegraph 
 repeaters: 
 
 The distance between cores of magnets and armature operated thereby sliould 
 be no si'pater than necessary to i>revent armature from stiekins. Controlling 
 mafinets once adjusted for obtaining maximum strength seldom require further 
 adjustment. 
 
 Adjustments should be so line that a considerable change in the temi>era- 
 ture of the room will so alter the distance between contact points that they 
 will require readjustment. With such adjustments a particle of dust will some- 
 times bridge the contact points, and they should be cleaned daily, or more 
 frequently if necessary. 
 
 An extra relay in each circuit at repeater stations makes it possible for a 
 repeater attendant to know beyond doubt just how the signals are received at 
 distant stations. This obviates depending on the varying judgment of men at 
 different stations. He can send rapid signals and observe exactly how they 
 pass through repeaters. 
 
 The repeater should be so located that contacts are readily accessible and 
 that light can be seen between the contact points or reflected to them by means 
 of white paper, thereby obtaining the same result. The repeating point of the 
 repeating sounder armature is on a spring which admits, if the adjustment is 
 correct, the repeating point to be opened only after the rigid points on this 
 armature which control the extra or controlling magnets have opened. 
 
 TEST FOR OPERATION OF TELEGRAPH REPEATERS. 
 
 A thorough knowledge of the operation of telegraph repeaters, personal inter- 
 est, and a comparatively small amount of time are necessary in order that 
 attendants may becoiue proficient in the care of telegraph repeaters. 
 
 MILLIKEN REPEATERS. 
 
 Figure references below refer to figure 2-14. The extra relay in each circuit 
 at repeater station reconuuended in the foregoing is not shown in tigure 2-14. 
 
 Slowly raise the left end of the armature of the repeating sounder T'. This 
 will break the circuit of the controlling magnet EM. and the return of its 
 armature will be distinctly heard. The next instant the spring contact x' of the 
 repeating sounder T' will be opened, thereby opening the circuit leading to 
 the relay A*, extra relay (not shown), and line. The oi)eniug click of the arma- 
 ture of the extra relay will be distinctly heard. It will be notinl that in the 
 above operation the armature of the relay If is held in the closed ixisition by 
 the armature of the extra magnet EM even though tlSe relay R be deeuergized. 
 
 (45)
 
 14 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 REVERSE OPERATION. 
 
 Upon lowering by hand the armature of the repeating sounder T', the spring 
 contact will first be closed and at the same instant the closing of the arma- 
 ture of extra relay mentioned above will be heard. At the next instant the 
 rigid contact points A' close, thereby closing the circuit to the extra magnet 
 E M. This draws the extra magnet armature away from the armature L of 
 relay R. 
 
 WEIXV REPEATERS. 
 
 With Weiny repeaters the effect is the same ; the opposite controlling arma- 
 ture, instead of falling back as in the Rlilliken, is held in position due to the 
 opening of one winding only of the two differentially wound coils of the magnet. 
 This fact is indicated by a sound emanating only from its armature. In rapid 
 sending the difference between the opening and closing of rigid and springy 
 contact points can not be detected, but nevertheless the difference must exist 
 l)efore the repeaters will operate satisfactorily, for should both open simul- 
 taneously, uneven, ragged signals will result. 
 
 Duplex Telegraphy. 
 
 [t'ondenst'd from "American Telegraph I'ractice," McNicol.] 
 
 By duplex telegraphy is meant a system which makes possible the transmis- 
 sion of two messages over a single wire at the same time, one in each direction. 
 
 THE SINGLE-CURRENT UUPLEX. 
 
 The most important elements of the single-current duplex are the trans- 
 mitter, the differential relay, the artificial-line rheostat, and the condenser. 
 
 LINE 
 
 Fig. 2-17.— TELEGRAPHY, DUPLEX, SINGLE CURRENT, THEORETICAL CONNECTIONS. 
 
 The single-current duplex is sometimes referred to as the Stearns duplex, in 
 lioiior of the inventor, Mr. Joseph B. Stearns. 
 
 Ill single Morse circuits, the armatures of all relays in the circuit, including 
 tliat at the home station and that at the distant station, are operated simul- 
 taneously when any signaling key connected into the circuit is manipulated. 
 
 When it is required to tran.smit a message in each direction over a line 
 simultiineously, it is evident that the receiving relay at each of the two 
 terminal stations nuist resjxtnd to the maniitulations of the signaling key at 
 the distant station, and not to the oiteration of the key at the home stalion. 
 
 Figure 2-17 is a diagram of the llieoretical connections of the single-current 
 duplex. \ line is shown extending l»etween stations A and li. T and T' are 
 the transniitters, l>li and DIV the different i.il relays, ,4/^ and Alt' the artiflcial- 
 
 (46)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 
 
 1") 
 
 line i^ieostats, and b and h' tlie main-line batteries at A and /{ resiieciively. 
 The nmction of the transmitter is simply that of a sifjnalinK key (•nnneeteil 
 into the mainline cireuit in such a manner that when the key is eloscd haltery 
 is applied to the line, and when the key is (ji»ened the liiu' is jirounded. 
 
 Fij:ure 2-18 shows a k«'y eonnectwl into the niain-liu(> circuit direct, to do 
 the work of a transmitter. Here, as in the case of the transmitter shown 
 in figure 2-17, it is apparent that wlien the key is depressed, battery is ap- 
 plied to the line, and when the key is openetl the line is grounded. 
 
 In the operation of duplexes — as will be explained more fully later — it i.« 
 essential that in the operation of the transmitter or of the key the shortest 
 possible interval of time shall elapse between the instant battery is removed 
 from the main line and the instant the ground connection is substituted there- 
 for. Obviously if an ordinary key were used to control the application of 
 battery and removal of ground connection, and vice versa, in the act of signal- 
 ing, the lapse of time between these two contacts would be excessive, due to 
 the comparatively slow movement of the hand in working the key, being more 
 pronounced the wider the gap maintained between the contacts of the key. 
 Also, were the ordinary key useil directly in the line circuit, the speed of 
 operation would be considerably curtailed owing to the requirement imposed 
 
 Fig. 2-18.— TELEGRAPHY, DUPLEX, SINGLE 
 CURRENT, THEORETICAL CONNECTIONS. 
 
 upon the operator to make equally firm and solid contact between the key 
 lever and the ground connection as between the lever and the battery contact ; 
 a condition that the average operator would find quite difficult to meet. 
 
 The transmitter, therefore, is used for the purpose of insuring instantane<nis 
 transfer of the line connection from battery contact to ground contact in 
 response to the operation of the key which controls the operation hu-ally of the 
 transmitter, regardless of whether the key is operati'd rapidly or slowly. 
 
 By noting the construction of the transmitter shown in connection with the 
 diagram, figure 2-17. it may be .seen that the moving element of the instru- 
 ment may be so adjusted that at the instant the battery is removetl the ground 
 contact is made, and thus the continuity of the line is pre.serve«l, or. in other 
 words, the period during which the line is open is reduced to a minimum. This 
 is a requirement of considerable consequence in the operation of nniltiplex 
 telegraphs. 
 
 All that is required in a differential relay is that when currents of c«iual 
 strength pass through both windings of the differential magnet, the cores shall 
 not become magnetized. It is to be remembered, however, that the amount 
 of magnetism produced in either core is directly dependent upon the strength 
 of current flowing in the winding around the core, and if the magnetic effect 
 
 (47)
 
 16 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 produced by one of the coils is to be exactly neutralized by that of the'*other, 
 it is essential that the current strength in the two coils be equal. 
 
 If the current strength in one coil is greater than that in the other coil, 
 naturally the excess current produces a certain anH)unt of magnetism which 
 is not neutralized and, due to this magnetism, the armature of the relay is 
 attracted. 
 
 It is already understood that the strength of the current flowing in a cir- 
 cuit is dependent upon the value of the applied e. m. f. and upon the ohmic 
 resistance of the circuit. In the case of the differential relay, therefore, it is 
 essential that if the relay is to be truly differential the current strength in 
 both windings must be identical, and this in turn imposes the requirement that 
 the resistance of each circuit must be identical. 
 
 Fig. 2-19.— TELEGRAPHY, DUPLEX, SINGLE 
 CURRENT, THEORETICAL CONNECTIONS. 
 
 Suppose a differential relay having a resistance of 200 ohms in each winding 
 is connected with a source of e. m. f. so that current flows through both coils 
 as indicated in figure 2-19. If it is required that the cores of the relay 
 magnets shall not be magnetized, it is necessary that equal current values 
 obtain in each of the divided paths to ground. The fact that the resistance 
 of each of the relay coils "is the same is of little consequence unless the circuits 
 beyond the relay also are of equal resistance. 
 
 In figure 2-19 current passes through one coil of the relay and beyond 
 through a line wire having 1,000 (»hms resistance, thence to ground. The other 
 coil of the relay forms a portion of a path to ground through a resistance coil 
 of 800 ohms. It is evident, therefore, that as the current divides at S, it has 
 two paths to ground, one having a resistance of 1,000 ohms and the other a 
 resistance of 1,200 ohms, and it is apparent that tliere will be more current 
 flowing in the circuit having less resistance than in the oilier. As a con.se- 
 quence, one core of the relay is to a certain extent magnetized, due to the (>xtra 
 cuii-fiil in one C(»il of tiie relay over that in the other cdil. 
 
 The resistance of main-line wires varii'S from a lew Iniiidi-cd oliiiis to 
 several tliousand olims iiml wliere dilVerentiMl relays ai-c used in duplex 
 operation, in ordri- to iiisurt' tiiat equal (MU'reiit \nlues ohlaiii in eni'h coil of 
 the rehiy wlien llie lioine liallei-y is ai>plie(l lo llie line .•irnl llie distant (Mid of 
 the line is grounded, it is neeessai\v to liave at tlie lioiiie station an ad.justal)le 
 resistance Ihi'ougli wiiiili the other coil of (he relay may be connected to 
 ground. 
 
 Obviously if this resistance is adjusted to have a \aliie e(iiial to lliat of the 
 line wire to the distant station, like current values will exist in both coils of 
 the relay, and there will not be any magneti.sm produced in the cores of the 
 relay. 
 
 (48)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 17 
 
 The adjustable resistance used le e([uate the resistance of llie niain-line wire 
 is generally called the artificial liiu'. 
 
 TllK AKTIKICIAI. l.INK. 
 
 All line wires possess electrostatic capacity. The quantity of electric charge 
 accumulated upon the surface of the conductor depends upon the superficial 
 area of the conductor, upon the distance intervening between the conductor 
 and the earth (or between the conductor concerned and other conductors in 
 electrical contact with the earth), and upon the nature of the insulating 
 medium intervening between the line wire and the earth. In any line of con- 
 siderable lenf^th a portion of the current is l)ound up in the form of static 
 charge. 
 
 The first rush of current into the line at the instant the battery is applied 
 thereto (sometimes referred to as the current of charge) for an instant 
 produces a much greater magnetic effect upon the armature of the h(jme relay 
 than obtains wlieu the entire line has been fully charged and permanent con- 
 ditions established in the circuit. 
 
 The result of the initial inrush of current, greatly exceeding in volume, as 
 it does, the final current, is that a false signal or " kick " of the relay armature 
 is produced. The energy of the kick depends upon the electrostatic capacity 
 of the line, being gi-eater where the capacity is high, and less pronounced as 
 the static charge taken on by the line wire is less. 
 
 Also, there is to be considered the effect of static discharge, which occurs 
 at the instant the line wire is shifted from the battery connection to the 
 ground connection upon opening the key controlling the operation of the 
 transmitter. At this instant the electrostatic charge, which has been accumu- 
 lated upon the surface of the conductor, flows back to ground by way of 
 the ground contact of the transmitter, passing tlu-ough the main-line coil of 
 the differential relay, again producing kick of the relay armature. 
 
 In view of these considerations, therefore, it is necessary if the false sig- 
 nals which are produced at the beginning and the end of each intended signal 
 are to be neutralized or nullified that the artificial line be made to possess 
 properties identical with those of the main-line wire; i. e., resistance and 
 capacity. 
 
 The application of the condenser as an adjunct of the artificial line gives to 
 the latter the desired property of electrostatic capacity. 
 
 A condsenser path to ground via the artificial-line coil of the differential 
 relay results in an initial rush of current through that coil at the instant bat- 
 tery is applied to the line, which, by means of adjustalile " timing " resistances 
 in series therewith, may be made to exactly equal in strength and duration the 
 corresponding rush of current which takes place at the same instant through 
 the main-line coil of the relay, thus at the critical moment insuring identical 
 current values in both coils of the relay. 
 
 And, further, when the line wire is shifted from battery contact to the 
 ground connection, at the moment the key is opened the discharge from the 
 condenser associated with the artificial line takes place through the relay 
 coil, forming a portion of the artificial-line circuit at the same instant that the 
 main line discharges through the relay coil, forming a portion of the main-line 
 circuit, thus again at the critical moment insuring equal current values in the 
 two coils. 
 
 (49)
 
 18 Signal Corps Manual No. 3. — Chapter 2. 
 
 To understand the import of the above remarks, one must have in mind 
 the positions of the main-line circuit and of the artificial-line circuit throuj^li 
 tlie windinjrs of the respective rehiy coils, also that the magnet made up hy 
 the artiticial-line relay coil and the magnet made up liy the main-line relay 
 coil both control the same armature. 
 
 When the relay is operated by current from the distant station its operation- 
 is due to a surplus of current in the main-line coil over wliat may be in the 
 artificial-line coil of the relay. 
 
 When the signaling keys at each end of the line are closed and like poles 
 of battery are applied at both ends of the line, the desired signal is made by 
 the home battery on the home relay and is the result of a surplus of current 
 in the artificial-line coil of the relay over what may be in the main-line coil. 
 
 AVhen, due to electrostatic charge or discharge of the main line, the current 
 in the main-line coil of the relay is augmented above that traversing the 
 artificial-line coil of the relay, a false signal will be produced unless at that 
 instant the current flowing in tlie artificial-line side of the relay is increased 
 to an equal value. This is what is accomplishe<l by using condensers and re- 
 tardation resistance coils in connection with the artificial line. 
 
 DOUBLE-CXJREENT DUPLEX SYSTEMS. 
 
 As a result of the development of more efficient and satisfactory duplex 
 systems, the single-current duplex is rarely used in this country, except where 
 it is combined with the polar duplex in forming the differential quadruplex 
 system of telegraphy by means of which two messages are sent in each di- 
 rection over a single wire simultaneously. 
 
 THE POLAR DUPLEX. 
 
 The essential elements of the polar duplex are a battery pole changer, a 
 differentially wound polarized relay, an artificial line rheostat, and an arti- 
 ficial capacity. 
 
 THE POLE rilAXCEU. 
 
 The transmitter sliown in connection with the single-current duplex, figure 
 2-17, has connected to one of its contacts the positive pole of a main-line 
 battery and to the other contact a circuit to ground. If to the latter the 
 negative pole of a main-line battery were connected instead of the ground 
 wire, closing the signaling key would send to line a positive impulse, and 
 opening the key would send to line a negative impulse, in which case the trans- 
 mitter might correctly l)e regarded as serving as a pole changer, inasnuich as 
 the polarity of the battery placed in contact with the line wire changes from 
 positive to negative and vice versa each time the transmitter tongue is cau.sed 
 to break contact with the positive battery terminal and make contact with 
 tlie negative battery terminal. 
 
 The introduction of the double-c-urrent duplex t-alled for the substitution of 
 a transmitter in place of tlie type of instrument used with the single-current 
 dui)Iex, which would meet the changed conditions. 
 
 'I'lie new form of transmitter, or pole changer as it has sinci' been termed, 
 provides ff)r tlie maintenance of an air gap, as 11i(> iiiiiin-linc contact is shifted 
 from one iK)le of the battery to the other. 
 
 So far as the pohir duplex is concerned, the saiiie necessity does not exist for 
 the employment of a coriliiiuity pre.serving transiiiilter as was the case with 
 the single-current duplex, the reason for which will be explained. 
 
 (50)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 
 
 10 
 
 THK I'OI.AK RELAY. 
 
 All of tlic iiiluM-('ii( riillicultics cxiHTifiiccd in tlu* ((]H'i-:ili<»ii of siii;ile Mor.se 
 lines are encoiintcrcil in ilic oiicrai imi nl' ilic siii;il('-(iirr('iil liinVi-fulial liiiplex 
 system. 
 
 Duriiif^ favorable weather and where a hif^h degree of line in.siilatioii is 
 maintained both of these methods of telegraphy are satisfactory. But when, 
 due to excessive lealcage conductance, the current values at tlie receiving end 
 are low, considerable difliculty is experienced in maintaining satisfactory 
 operation. 
 
 The polar chiplex overcomes this difliculty to a great extent, and by means 
 of this system lines may be worked satisfactorily long after adverse weather 
 conditions have rendered single Morse and single-current duplex systems in- 
 operative. 
 
 Figxire 2-20 shows a theon'tical view uf tlie magnetic circuit of the polar 
 relay. 
 
 Arttflinc 
 
 Artif.line 
 
 Fig. 2-20.— TELEGRAPHY, DUPLEX, POLARIZED RELAY, THEORETICAL CONNECTIONS. 
 
 It will be .seen that the windings are identical with those of the ordinary 
 single-current differential relay. Current from the battery flows through ilie 
 windings in opposite directions, the action of one coil neutralizing that of 
 the other, the result of which is that the core is not magnetized so far as 
 any action due to the cun*ent from the battery is concerned. 
 
 The fundamental difference between the two instruments is that in the 
 polar relay the tongue is held on either side, due to the magnetic pull of the 
 permanent magnet which constitutes the cores of the electromagnets. 
 
 In the case of the common differential relay, the armature tongue is held 
 in the closed position by the action of either or both magnet colls and in the 
 open position by a spiral spring. With the polar relay the armature is drawn 
 into contact with one or the other poles, due to magnetism in the cores, result- 
 ing from the action of current in either coil of the instrument. The im- 
 portant feature with the latter relay is that after the armature has once l>een 
 attracted toward either contact it will remain there, whether current remains 
 in the coil winding or not (provided there is no current in the opposite coil). 
 
 Referring to flgure 2-20: When the key is operated, the armature lever of 
 the pole changer is caused to make contact, first, with the negative ix)le terminal 
 and then with the positive pole terminal. If the ohmic resistances of the real 
 line and the artificial line are equal, current from wliichever dynamo is con- 
 nected with the armature lever will flow through the companion windings of the 
 
 (51)
 
 20 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 relay differentially, with the result that there is no electromagnetism produced 
 in the cores facing the relay armature. It matters not whether the outgoing 
 current is from a positive source or from a negative source, owing to the fact 
 that it passes through the windings of the relay dilTerentially there will be no 
 magnetism produ^CTl, and this irrespective of the polarity of the current 
 flowing in the circuit. 
 
 If the key is manipulated, there will be sent out a series of impulses alternat- 
 ing in sign, from positive to negative each time the key is closed and opened, 
 and if the resistance of the artificial line side of the relay balances that of 
 the line side, the armature of the relay will not be affected. Moreover, it will 
 be found that if the relay tongue is moved by hand into contact with its closed 
 contact or with its open contact, it will still remain passive to the outgoing 
 reversals from the i)ole changer. 
 
 The magnets of polar relays are so wound that when current from the distant 
 station flows through the main-line coil, it is given a path through an auxiliary 
 winding in the opposite coil in the reverse direction which results in the perma- 
 nent-induced magnetism in one of the cores being neutralized, while the magnet- 
 ism existing in the other core is intensified, causing the armature to be attracted 
 
 Fig. 2-21.— TELEGRAPHY, DUPLEX, POLAR, CIRCUITS. 
 
 toward the opposite contact. The reverse action takes pjace when the battery 
 poles at the home station and at the distant station are in opposition (like 
 poles to line) in which case the artificial-line coil of the home relay has its 
 magneti.sm increa.sed, and the line coil has its magnetism neutralized. Tluis, 
 due to the action of the current in the coils, the armature is caused to move 
 into contact with tlie open or the clo.sed contact as desired. 
 
 The ofiice of tlie auxiliary winding in eacli case is to act as a "clearing out" 
 agency. 
 
 There are several distinct types of polar relay u.sed by tlu' v;iri(»us telegraph 
 administrations, each relay having its peculiarities of design, but the principle 
 upftn which all polar relays operate is the same. 
 
 Tlie ai'tificial line rheostat, and the artificial capacity used in connection with 
 I»olar duplex ajjparatus to "balance" (he resistance and capacity of the actual 
 line, an; the sanu; as those for tlie single-current duplex. 
 
 Oix'ratirm of tlie point' (luj)lr.v. — Figure 2-121 shows llic connections of the 
 main-line and local circuits of the ])olar dujilex. 
 
 Complete equipment at both ends of a duplexed circuit are shown so that the 
 various operations may be treated with regard to their effects upon the appa- 
 ratus at both ends of the line. 
 
 <52)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 21 
 
 PP and PC are the pole cliiinf^ers jit stations .1 and li, respectively, wliile PR 
 and PR' are the polar relays, K and K' the .signalin}< keys, locally controlling 
 tlie movements ol" the pole-clianyer armature in each case. 
 
 The dynamos, which furnish current for the operation of the main-line relays, 
 are shown — two at each en<l. In ea<-h case one of the dynamos lias its positive 
 terminal connected with the back stop of the pole changer, while the other 
 dynamo has its negative terminal connected with the closed contact of the pole 
 changer. 
 
 The resistance coils and condensers, which comiirise the artificial line, are, 
 at each end of the main-line circuit, marked AL and AL' . 
 
 In tigure 2-21 the pole changers at each end of the line are closed; that is, 
 the armature levers of the pole changers in each case are in contact with their 
 front stops, due to the fact that the signaling keys K and K' are close<l. This 
 places to line at each end a 200-volt negative battery. As the liatteries are of 
 equal potential, no current will Ilow" over the main line. At the instant both 
 pole-changer armatures make contact with their back stops — thus placing oppos- 
 ing battery to line — the levers of the polar relays at each end are moved into 
 contact with their back stops, thereby opening the local reading sounder circuits 
 at each end. At this point it is important to gain a correct understanding of 
 why the armatures of the polar relays at each terminal station are attracted 
 toward either contact when the main-line batteries at each end of the line are in 
 opposition. The explanation is tluit when the terminals of a wire are at equal 
 potential, no current will flow in the wire. Therefore, when like poles of 
 itlentical potential are to line, as in the case before us, it is apparent that the 
 terminals of the main-line wire are at equal potential. An entirely different 
 condition, however, exists with regard to the artificial line at each end. As, 
 in eacli case, one end of the artificial line is connected with the earth (which is 
 at zero potential), there is presented to the outgoing currents from each station 
 a path to ground via the artificial line magnet of the polar relay. On each 
 occasion, therefore, when like poles are to line at each end, current from the 
 liome battery flows through the artificial line and the armature of the polar 
 relay is attracted toward its back stop if the opposing batteries are positive 
 and toward its front stop if the opposing batteries are negative. 
 
 In order to carry on transmission in both directions at the same time it is 
 necessary that the operator at ^1 shall be able to control the movements of the 
 armature of the relay at B regardless of which pole of his battery B has to 
 line. Also, that the operator at B shall be able to control the movements of the 
 relay armature at A regardless of which pole of his battery ^-1 has to line. 
 
 Suppose the operator at B should depress his key (while the key at .1 is 
 open), thereby placing the tongue of this pole changer in contact with the nega- 
 tive pole of the main-line battery at B, the result will be that the main-line 
 coil of the relay at .1 will be energized and its tongue attracted toward its cU>sim1 
 contact, thereby operating sounder S. 
 
 It is evident, of course, that current continues to flow through the artificial 
 line coil of the relay at .1. but owing to the fact that the current strength in 
 the main-line coil of the relay is twice that in the former and in the opi)osite 
 direction, it is plain that the magnetism in the core of the relay at .4 is 
 reversed, and the armature, as a result thereof, moves into contact with its 
 front stop. If what has previously been statetl is true, the armature of the 
 relay at B should have remained passive to the reversal of current sent out from 
 B when the key at B was closed. That this is so is apparent, for,' although the 
 magnetism in the artificial line magnet of the relay at B has now been ueu- 
 
 (53)
 
 22 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 tralized, due to the presence of current in the main-line coil of the relay, the 
 armature is held in the open position by the action of the permanent magnet asso- 
 ciated therewith. In other words, nothing has happened so far to cause the 
 armature of the main-line relay at li to change its position ; therefore, it remains 
 in the position taken when last it was caused to move by a surplus of magnetism 
 in one coil over that obtaining in the other magnet coil. Similarly, when A 
 alone closed his signaling key, the relay at B responds, while the relay at A 
 does not. When the signaling keys at both ends are depressed, the line currents 
 once more are in opposition, and, as in this case, the currents flowing through 
 the artificial lines at each end are in the reverse direction of that taken when 
 both keys were open, the relay armatures at each end are caused to move into 
 contact with their front stops. 
 
 In effect, therefore, when the operator at A attempts to register a " dot " on 
 the relay at B, at the same instant that the operator at B intends to register 
 a " dot " on the relay at A, each station causes to be produced in his own relay 
 the signal intended to be transmitted from the distant end of the line. Or, 
 the foregoing might be paraphrased thus : The relay at A will be closed 
 whenever the key at B is depressed, regardless of whether A is sending or idle ; 
 and the relay at B will close whenever the key at A is closed whether B is 
 sending or idle, but in neither case will the signals transmitted from either end 
 conflict with those originating at the distant station. 
 
 Fig. 2-22.— TELEGRAPHY, DUPLEX, BATTERY. 
 
 THK BATTEIIV DUTLKX. 
 
 Figure 2-22 shows the theoretic connections of the main-lino inslrunients u.sed 
 to operate a polar duplex by means of gravity battery. 
 
 In this duplex arrangement the pole changer consi.sts of Iwo double-contact 
 relays, or transmitters. The transinitt(M-s are connected in series, that is, one 
 signaling key controls the opeT'atinn of Ixith inslrunients, .so that both arma- 
 tures arc in the closed posilion at the siinie time, and in the open iM)si(i<>n at 
 the same lime, depending upon whether the key is oi)en or closed. 
 
 It will be .seen at a glance that when both artnature levers are in contact 
 with their back stops the positive pole of the row of gravity cells is conni'cted 
 to line via the tongue of transmitter No. 1, and at the same time the negative 
 pole of the battery is "grounded" via the tongue of transmitter No. 2. Con- 
 versely, when the signaling key is closed mid holli tongues ai-e against their 
 front stores, the negative pole of llic hiiltcry is connected to line and the posi- 
 tive terniinal of the battery (n grouml. Tlic opnnition of the key, controlling 
 as it does simultaneously the operation of both transmitters, residts in alter- 
 nate positive and iK-gativc impulses being sent to line, the same as when two 
 dyrvimos (»f oi»posil(> i»olarities are used. 
 
 In other resfK'cts the r-oiiiiections are the same iis in the dynamo jtolar duplex. 
 
 (r.4)
 
 Telegraphy and the Induclion Telegraph Set. — Chapter 2. 
 
 23 
 
 THK " lilllUCK " DLI'LEX. 
 
 The sinRle-ciirrent duplex and tlio itolar duplex l)einK basetl <ui the differ- 
 ential principle are dependent upon iirodueint; an equality of current strengths, 
 while the bridjie duplex, which is based upon the well-known Wheatstone 
 bridge principle, is dependent upon itroducinj; an equality of potentials. 
 
 Fifiure 2-23 shows two stations .1 and Ji at either end of a line wire e<iuipi>e<l 
 with bridjie duplex apjiaratus. 
 
 li and li' are tlie niain-line batteries at .1 and li respectively, .l/y in each 
 case represents the artificial line at either end. li and Ji' are two artihcial re- 
 sistances of equal value, likewise r and r' at station B. At each end of the 
 line the relays are connected between the points c and d of the " bridge " 
 formed by the line wire and the artificial line resistance. Closing the key at .1 
 sends out a current which divides at n, half passing over the line wire to .sta- 
 tion /{ and reaching eartli via the aitjtaratus at that end of the line, while the 
 other half passes through the artiticial line at .1, reaching the earth at that end 
 of the <-ircuit. Inasmuch as the points <■ and d are equidistant, ohmically, from 
 
 LINE. 
 
 ■m^ 
 
 -Mh 
 
 Fig. 2-23— TELEGRAPHY, DUPLEX, BRIDGE, THEORETICAL CONNECTIONS. 
 
 the i)oint a, their potential values are identical, and no current will flow 
 through the windings of the relay at ^1. This is true, of course, oidy when the 
 resistance of the artificial line at A is made equal to the resistance of the 
 actual line to ground at the distant end. The relay at .1. therefore, is not 
 affected when A sends to B. The same condition prevails when B alone sends 
 to A. Signals from A operate the relay at B because the incoming signals have 
 a joint path made up of the branches c-d and c-a, thus .setting up a difference 
 of potential between the points c and d sufficient to operate the relay. 
 
 The operations which take place with different key combinations at «'itlier 
 end of the bridge duplex may be traced without difficulty. 
 
 Since the line relay employed in the bridge duplex does not need to be differ- 
 entially wound, it is evident that any ordinary relay may be used with this 
 method of duplexing. It is apparent, also, that the outgoing currents do not 
 pass through the windings of the home relay, and. as the currents pa.ss directly 
 to line, there is a minimum amount of retardation in the sending circuit. And. 
 further, it is claimed for the bridge duplex that its line relays, on account of 
 their position in the brid.ge, are not as resjionsive ti> induced line disturbances 
 or to earth currents as are the line relays in the dilTer<>ntial duplex. This is 
 due to th(> fact that in the bridgi' .system only a portion of the line currents 
 pa.ss through the relay, no matter whether the currents are the result of an 
 impressed e. m. f., of induction, or of conduction from neighboring circuits, while 
 
 (55)
 
 24 Signal Corps Manual No. 3. — Chapter 2. 
 
 in the differential duplex all currents existins in the main lin(> jiass tliroush 
 the windings of the line coil of the relay. 
 
 The bridge duplex has been more highly developed in Eiu'ope than in America, 
 and several of the refinements applied to its operation there are particularly 
 noteworthy as having a bearing on the general subject of high-speed signaling. 
 
 BALANCING THE POLAU DUPLEX. 
 
 The polar duplex is balanced by asking the distant station to " ground." 
 This he does by throwing the 3-point switch G.S', figure 2-21, to down position. 
 (Sometimes the left-hand lower "point," or disk, is connected to the earth via 
 SC, sometimes it is the right-hand lower point that is so connected.) This 
 action disconnects the pole changer and battery from the line and transfers the 
 latter to the earth via tlie resistance coil 8C or SC. These resistance coils ai'e 
 inserted, as in the Stearns duplex, to compensate for the internal resistance of 
 the battery at each end. When the distant switch has been turned the home 
 switch is also similarly turned. The adjusting screw of the polarized relay is 
 turned forward or backward until the armature remains on whichever side it 
 may be placed. The home battery is then placed to the line by turning the 
 .switch OS to the up position right. Then the pole changer is opened and 
 closed and the i-esistance in AL or Afy is adjusted iintil the armature of the 
 relay remains on either side, as before. This insures a " resistance " balance. 
 The pole changer is now closed and opened rapidly, and if short clicks are heard 
 the capacity of the condenser is varied until these disappear altogether. This 
 shows that a " static " balance has been obtained. A static balance can also 
 be had by asking the distant station to " cut in," which he does by tiu'ning the 
 switch to the up position. When he has done so, ask him to close his key. so 
 that the armature of the home relay will rest against its contact point. The 
 armatiu'e may then be given a slight bias awa.v from its contact point and the 
 home pole changer again operated. If clicks are still heard in the sounder, the 
 condenser and its resistance coil are adjusted initil they disappear, when the 
 distant end may be asked to send a few words, to give an opportunity to read- 
 just the armatui'e to its proper plac-e. As a rule, however, a good working 
 static balance can be obtained on a polar duplex without giving the armature 
 of the polarized relay a bias. 
 
 Western Union 1'ole Changer. 
 
 The Western Union standard pole changer for gravity batteries is shown in 
 figure 2-24. The contact points of the instrument are inclosed in a circular 
 glass-incased box. The end of the lover L is seen extending into the box 
 through an aperture in the back of the framework. The tension springs K S' 
 are insulated from the box. The contacts C C are attached to the framework. 
 The poles of the battery are generally connected to the springs S fi' by way 
 of their respective binding posts on the side of the baseboard. The lever is 
 connected to the earth, and the contact points C C to the line, or vice versa, 
 as desired; also via the binding posts. 
 
 TllK \l>.irST.Mi:.\T OK TELEfiKAI'H APPARATUS.' 
 
 If operators in general could be nL'idc to realize bow nnicii more comfort 
 they might take in their daily work did they but ac(|uii'(' even a slight knowl- 
 edge of the knack of adjusting their instruments i)r(»i)erly, they would certainly 
 
 1 By Willis n. Jones, in tbe Telcgrapii Age, September and October, 1902. 
 
 (56)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 
 
 25 
 
 make a move in that direction t'<ir tlieir own interest if not for tiiat of the 
 company emphtyins them. 
 
 Tliere is positively no excuse for tlie indistinct manner in winch si^rnals 
 are so frequently recorded on the really lirst-cla.ss instruments employi'<l by 
 telegraph companies to-day. When the sijrnals do not arrive in proper shape 
 there" is some good reason for it, but the theory of the fault given by the 
 average operator is nsually wide of the mark, and as he "adjusts" in ac- 
 cordance with his ideas of the trouble, he generally makes matters worse by 
 such eltorts. 
 
 Fig. 2-24.— TELEGRAPHY, DUPLEX, POLE CHANGER. 
 
 For tlie purpose of demonstration let lis see wliat may be learned in the way 
 of adjustment and care of an ordinary single-line relay and sounder. Now, 
 we will assume that the wire, battery, and instrument coils are in first-class 
 order and then introduce a few conditions for the pui'pose of noting the 
 different effects produced on the apparatus. 
 
 Wet-Weatheu Effects. 
 
 In wet weather the quantity of current which traverses the coils of a relay 
 is greatly increased at or near the battery station over and above that which 
 normally flows in clear weather, while distant-station instruments receive less 
 than the usual amount. This condition is caused by the numerous •' e.scai)es " 
 or side paths down the poles along the route which draw additional current 
 from the dynamo, all of which must necessarily pass through the relays in- 
 serted between them and the battery. Distant relays receive less than they 
 are entitled to, because much of the current on the wire " escapes " down 
 the wet poles before reaching them. Now, a strong current in the coils means 
 a strong magnetic pull on the relay armature, while a weak current, of course, 
 causes a correspondingly weak attraction. 
 
 It follows from this that the wet-weather method of adjusting a distant 
 relay is directly opposite to that followed for the home relay at the battery 
 end of the circuit. The operators at distant points must get the magnets closer 
 
 (57)
 
 26 Signal Corps Manual No. 3. — Chapter 2. 
 
 and closer to the armature as the downfall of rain increases, while the home 
 operator is compelled to draw his relay coils away from it. This seems like 
 a very simple operation to perform, but the maniier in which most operators 
 go about it explains why they fail to secure the best residts. 
 
 The first principle of adjustment lies in maintaining at all times, whether 
 the current is weak or strong, a praictically constant or normal tension of 
 the retractile spring attached to the relay armature. The explanation is 
 that a relay spring responds best to the magnetic attraction of the armature 
 when the tension is such that the " curling " is not stretched to any great 
 extent out of its original close-fitting construction when new. 
 
 The adjustment should invariably be made by moving the magnet backward 
 or forward by means of the thumbscrew. The tension of the retractile spring 
 need not be altered perceptibly except to give the operation a finishing touch. 
 The habit of stretching the relay spring to meet a strong magnetic pull not 
 only causes the former to work less efficiently at the time, but soon injures 
 it permanently by destroying its sensitiveness. 
 
 Feeling for a Distant Station. 
 
 It frequently happens in very wet weather that a distant office can not 
 " break " the operator at or near the battery station on account of the difficulty 
 the latter has in getting a fine adjustment. When informed via some othert cir- 
 cuit that such is the case the best method to pursue is as follows : IMake a 
 few dots to attract his attention (he will hear you; the distant office has the 
 advantage in this respect) and then tell him to "dot." Now pull the magnets 
 back from the relaj' armature until the circuit stands apparently just open. 
 Next turn down the retractile spring very slowly until you hear the signals. 
 If you miss them, you may sometimes catch them by placing your finger on 
 the lever of the relay and giving it a gentle pressure back and forth. If the 
 operator is dotting, you will feel the impulses and thus be able to readjust the 
 Instrument. 
 
 The latter metliod is an excellent one to pursue on a way wire when in doubt 
 as to whether anyone is using the circuit, for by this precaution one operator 
 need never break in while another is sending. However, as it is only in very 
 wet weather that an operator is bothered to any great extent by the relay, the 
 real source of daily discomfiture usually lies in an improper adjustmnet of 
 the sounder. 
 
 ad.tttstment ok sounders. 
 
 When a sounder does not give out a loud enough tone to suit an operator, he 
 almost invarial)ly proceeds to give the lever a wider play, as if that was the 
 only remedy. As a matter of fact that process in itself seldom brings about 
 the desired results unless the lever at the time happens to lie screwed down 
 abnormally close. The important thing to know is that if you give the lever a 
 play which will permit the armature to move away from the magnet cores 
 beyond a normal distance, the magnet lias a hard time getting control of it 
 again. The explanation is that a magnet loses its power to attract the armature 
 in a degree directly jtroportional to tlie square of the distance separating them; 
 or, in other words, to the square of the air gap. For example, if two magnets 
 similarly constructed in all respects be f(>(l by an ecpial strength of currcMit, and 
 tlH' air gap between the cores .hhI the :iiiiiature of one miule the thickness of a 
 cardboard, while two cards could occuiiy the gap in the second magnet, the 
 former would be practically four times as strong as tli(> latter. It is plain, 
 
 (58^
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 27 
 
 therefore, that to give the sounder lever too great a i)hi,v will so weaken the 
 pull on the armature when in its " opi-n " position tliat when tiie local circuit is 
 again closed the lever moves so shnvly at first that it hardly has time to cross 
 over the space hefore the current is again hroken. The result is that a signal 
 is partially broken up before completion. 
 
 The lesson to be learned from this is that the play given to an armature 
 lever must never l)e so great that the magnet can not bring it back promptly 
 within the time allotted to complete a signal. This, in turn, sugge.sts that the 
 amount of play given should be decrea.sed in proportion to the speed with which 
 the signals are increased. The proper method to increase the volume of sound 
 is as follows : 
 
 AI).Il'STIN(; lOK M.WI.MIWL STKENtJTII. 
 
 IMace a sheet of i)aiier between tlie aiMiialure and tlii' poles of llie sduuder 
 magnet and tiien lower the former until there is just space enough to move the 
 paper back and forth without catching. This permits the magnet to exert its 
 maximum strength on the lever, and the position should seldom be altered. 
 Whatever changes are necessary during the process of adjusting should be 
 effected by means of the spring, the upi)er thumbscrew, and those which regu- 
 late the trunnion. The adjustment of the trunnion screws is a matter too 
 generally overlooked. It is there that the pitch or quality of the sound is regu- 
 lated. The pivot nuist not bind too tightly, nor yet be too loo.se. 
 
 When signals do not reach the operator in the particular style that suits his 
 fancy, he usually atteini)ls (o remedy the fault by giving the sounder lever a 
 greater or a lesser jilay. If the trouble happens to lie in an improper adjust- 
 ment of that part of the apparatus he may possibly succeed in helping matters, 
 but the fact is that indistinct signals may be due to a great variety of causes, 
 any one of which, in his ignorance, he may never suspect. 
 
 For the purpose of illustration, let us again take the ca.^e of an ordinary 
 single-line relay and sounder and assume that despite a careful adju.strnent of 
 th(> relay and sounder magnets after the manner suggested in the prece<ling 
 installment of this article th«i signals continue to "drop out" at times. 
 
 The lirst thing to determine is whether the fault lies in the relay or the 
 sounder. Such disturbances are usually due to a loose or improper connection 
 somewiiere in the local circuit, but not alwa\s. Naturally the first move made 
 toward locating the trouble should be to examine all binding posts, and opera- 
 tors in general would save themselves many annoyances if they would acquire 
 the habit of doing this whenever they sit down to a different set of instruments. 
 If the binding-post connections prove to be secure, open the key and "dot" or 
 "write" with your hnger on the relay armature or lever, using the latter as a 
 key. If the signals then respond firmly and distinct, the local circuit is not 
 fauhy, and attention should be directed to the relay. 
 
 In many cases the source of the trouble will turn out to be too tight an adjust- 
 ment of the trunnion binding posts, thus preventing the restrained armature 
 from responding readily to the influence of the magnet. This fault is particu- 
 larly applicable to circuits in which the strength of the current flowing through 
 the relay coils is weak. Where the main-line current is strong, the magnet is 
 frequently able to overcome this drawback, but it is evident that even then tlie 
 working margin of that instrument has been cut down to the extent that the 
 trunnion binds. It follows, then, that the trunnion binding posts should always 
 be so adjusted that the crossbar or axis upon which the lever and armature 
 rests may move jterfectly free in its .sockets. 
 
 46581°— 17 5 (59)
 
 28 Signal Corps Manual No. 3. — Chapter 2. 
 
 If, hoA\ever, the signals made in the manner suggested continue to drop out 
 despite tliis precaution, the fault will possibly be found in a loose connection 
 somewhere in the local circuit. If tightening the binding posts fails to remove 
 the trouble, examine the fine wire wound around the shaft of the relay lever, 
 one end of which is attached to the shaft and the other to a part of that trun- 
 nion binding post where the local battery makes its exit. If this wire becomes 
 broken, the sounder signals will certainly "drop out" at times owing to the 
 loose connection made between the shaft and the post as the former turns in 
 the socket. The purpose of the fine wire is to bridge over this unavoidable break 
 in the local circuit, and the operator will at once see the necessity of keeping 
 that connection intact. 
 
 When a sounder stands "open" and it is desired to ascertain if the break in 
 the local circuit lies in some of the relay connections, place the blade of a knife 
 across both local binding posts (situated just behind the relay spring). If 
 the opening is in that instrument, the sounder will then close. If the latter 
 remains open, try the same method with the two posts of the sounder itself. 
 If the coil or wire connections there are broken, a si)ark will be noticed the 
 moment the blade makes and breaks contact ^^•ith the two posts. The sounder, 
 however, will not close, because the magnet coils are cut out. 
 
 The knife-blade method, however, should never be resorted to where sounders 
 are connected up in multiple, such as is usually the case in our large modernly 
 equipped offices, because the cutting out of the coil draws so much current 
 through the low-resistance route via the blade that it melts the fuse and opens 
 the other four or five companion sounders comprised in that particular group. 
 Ojjorators see this fact frequently demonstrated in large telegraph oftices 
 when someone thoughtlessly or ignorantly permits a steel penholder or other 
 piece of metal to sinuiltaneously make contact with both binding posts of the 
 sounder or resonator connections. When this occurs, the "locals" go off on 
 several adjacent desks and business is suspended imtil a new fuse is substi- 
 tuted. The blade may be placed across the local posts of the relay, however, 
 because it will not cut out the coils of the magnet, hence the resistance is not 
 lowered. It may also be done where the sounder (Toils are in series with a loop 
 or lamp resistance, such as the arrangement which obtains with duplex and 
 quadruplex circuits. 
 
 It will be seen from what has been stated that the adjustment and un- 
 derstanding of even an ordinary relay and sounder require considerable skill 
 and a fair degree of electrical knowledge, yet an operator who does not possess 
 ambition enough to interest himself to the extent of understanding the instru- 
 ment before him certainly deserves much of the needless provocations which 
 come his way. 
 
 Up to this point the suggestions concerning various methods of adjusting 
 telegraph apparatus have been confine<l to the receiving instruments. Tlie 
 sending apparatus, however, demands quite as nuich attention and skill on the 
 I)art of the operator as the receiving instruments. 
 
 Operators, as a rule, hardly realize the fact that with but a very little study 
 on their part it lies within their power to not only make their own work much 
 easier, but that also of tiie niiin at the distant end of the circuit. 
 
 One of the most connnon iiiis(Ml<('s the oi)erator makes is to find fault with the 
 key frequently because of his inability to send fast or to make the Morse alpha- 
 bet easily. It may surprise many readers to learn that as a matter of fact the 
 key is seldom to blame. It is really a matter of what is called the electrical 
 an>l the niechanifiil inertia of the instruments that cause the trouble. 
 
 (60)
 
 Telegraphy and the Inductiun Telegraph Set. — Chapter 2. 29 
 
 For example: In ji telejrraiili wire where tlien- arc a jxreat many otlices close 
 together, such as we tind on some railroad circuits, there are necessarily many 
 relays, the highly wound coils of which compose the greater part of the total 
 resistance. Where such a condition exists the counter electromotive force 
 developed within and by the coils is so great that it checks the quick action of 
 the current in its operation of building up the magnetism in the iron cores of 
 the relays, and thus deniands a slower rate of speetl on the part of the sending 
 operator in tirder to fully form his characters. Unless ho complies with this law 
 the second impluse in the formation of a character will be begun before the 
 preceding one has been fully " built up," with the result that the key will 
 " stick," as he erroneously believes, and the key gets the blame. 
 
 With sounders, as usually arranged, the case is different, but the effect is 
 just the same. If you give the lever of a sounder an abnormally great degree of 
 play, and then make " dots " exceedingly rapid, the lever will probably remain 
 in an " open " position during the experiment. Decrea.se the speed somewhat 
 and it will respond iudilYerently. If, however, you open and close the key very 
 slowly, the Uwer will follow the movement faithfully. Finally, if you adjust 
 the lever armature close to the magnet and give it l)ut very little play, every 
 " dot " will be heard, no matter how fast you make them. 
 
 The lesson to be learned from these experiments is that where speed is re- 
 quired the lever must be given as little play as practicable in order to reduce 
 the mechanical inertia to a minimum. Where an operator ignores this rule, 
 in order to get a greater volume of sound to receive by, he will experience the 
 .same dilliculty in forming the alphabet as his friend with the choked relay did, 
 and probably vie with him in condemning the greatly abused key. 
 
 The application of these lessons is directed principally to those in charge of 
 duplex and quadruplex apparatus, and cautionary to operators in branch offices 
 working sounilers on legs or loop extension. On account of the tongue and the 
 retractile spring on transmitters, and the accuracy with which pole changers 
 must be manipulated, those instruments demand very careful adjustment to 
 the speed of the transmitting operator. Sounders, on the other hand, once 
 properly adjusted, respond so clearly (on the transmitting side) that operators 
 in branch offices working on duplex loops find that the sending side works, 
 apparently, as well on a poor wire as a good one. The result is that in bad 
 weather the fact is frtniuently overlooked that the pole changer or transmitter, 
 as the case may be, can not perform their functions properly at a dry-weather 
 speed, and thus by maintaining their usual speed cause no end of trouble both 
 to themselves and the quadruplex chief at the main office. 
 
 PowEii i-OK Operating Telegraph Systems. 
 
 Most of the large telegraph systems are operated by current obtained direct 
 from generators driven by electric motors. 
 
 Where batteries are used for operating telegi-aph systems, they are fre- 
 quently of high voltage, and particular attention shouhl be given to insure of 
 their being highly insulated. 
 
 With storage batteries for this purpose, if the small porcelain or gla.ss in- 
 sidators for each cell are furnished so much the better; if not, the shelves 
 i^hould be as well insulated as possible, or strips of glass or small strips of 
 paraffined wood under each cell may be used in an emergency. 
 
 In charging some of the smaller types of cells a convenient arrangement 
 is represented in figures 2-2.") and 2-26. In this the electric-light mains are con- 
 nected with the storage cells with some incandescent lamps in parallel, as 
 
 (61)
 
 30 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 shown. If 110-volt 32-can(llepo\ver carbonized filament lamps are used, each 
 lanjp allows approximately 1 ampere of current to pass. So with a type of 
 cell requiring 6 amperes, 6 lamps in parallel would permit the required cur- 
 
 £/ectr/c Ught Leads 
 
 Lamps 
 
 'M 
 
 Storage Cef/s 
 
 Fig. 2-25.— TELEGRAPHY, POWER, CHARGING STORAGE BATTERY. 
 
 rents to pa.ss. Of course the source of supply must be a direct, not an alter- 
 nating, current. 
 
 The diagrams (figs. 2-2.'i and 2-2G) show the arrangement for an odice 
 where a constant-current lighting current is available as a supply. 
 
 Electric Light Mains 
 
 Lamps 
 
 SM 
 
 Storarfe 
 
 ISJ 
 •Cell 
 
 f^ I Relays and 
 Sounders 
 
 Fig. 2-26.— TELEGRAPHY, POWER, CURRENT FOR RELAYS AND SOUNDERS. 
 
 The lamps may be used to illuminate the office, as the opposing E. IVI. F. of the 
 one-storage cell (fig. 2-26) will not perceptibly diminish their light. As will be 
 noted, the storage cell is constantly in use even while charging. 
 
 0)n account of its low internal resistance, as many sounder circuits in 
 parallel can be fed from one of these storage cells as the capacity of the 
 battery will permit. Each sounder requires one-fourth ampere, so in 24 hours 
 it would require at most 6 ampere hours to supply it. And if the storage 
 cell had a capacity of 50 ampere hours it could supply four sounder circuits 
 24 hours and still hav(> a reserve foi- another day in case of accident to the 
 charging circuit. 
 
 Induction TKi.KoitAiMi Skt. 
 
 The induction tch'gra|)li set (tig. 2-27) is strictly a iiortable field instnunent 
 which was devei()|»ed by the Signal ('orjjs. It is designed for sending Morse 
 signals over field lines of connnunication and other lines where it is diflicult 
 
 (C2)
 
 Telegraphy and the Induction Telegraph Set.— Chapter 2. 31 
 
 Binding posts, complete 
 
 Case, complete 
 
 Case, cover for 
 
 Case, hinge for 
 
 Case, circuit diagram frame 
 
 Case, circuit diagram 
 
 Case, circuit diagram, celluloid cover for 
 
 Case, cover fastener, complete 
 
 Case, internal, for battery 
 
 Battery, timgsten, t\"pe A (2 units to a set) 
 
 BatterV, spring and support for 
 
 Switch", D. P. I). T.. complete 
 
 Switch, D. P. D. T., handle for 
 
 Key, complete 
 
 Key, spring for 
 
 Key, spring adjust ing screw , 
 
 Key, roar adjusting screw 
 
 Key, trumiion screw and lock nut 
 
 Key, handle for 
 
 Sounder, complete 
 
 Sounder base 
 
 Sounder armature. 
 
 Sounder armat ure supports ; — 
 
 Soimder permanent magnet 
 
 Sounder, coils for (2 to a set) 
 
 Sounder, armature movement adjusting screw. 
 
 Sounder spring tension adjusting screw 
 
 Induction coil, complete 
 
 Induction coil, coil for (2 to a set) 
 
 (63)
 
 32 
 
 Signal Corps Manual No. 3. — Chapter 2. 
 
 to supply the large amount of battery required for ordinary telegraphic work. 
 It can also be used for the transmission of speech by making certain moditica- 
 tions. The instrument comprises a wooden case the dimensions of whicli are 11^ 
 by 75 by 6 inches, outside. The top of the case contains instructions for op- 
 erating and a diagram of circuits. A baseboard, which is removable by means of 
 four screws, has on its underside the wiring and has on its upper surface a bat- 
 tery case of aluminum to hold two tungsten batteries ; an induction coil of the 
 closed magnetic circuit type ; a doul)le contact telegraph key of standard pat- 
 tern ; a polarized sounder, which will be described later ; a double-pole double- 
 throw switch for reversing the connections to line, and three binding posts num- 
 bered 1, 2, and 3. In addition, authority has beeu issued by the Chief Signal 
 Officer to install a fourth binding post on all instruments in service, to be con- 
 nected to the contact of the bottom battery. This is for the purpose of at- 
 taching external battery to this instrument and for this purpose the batteries 
 in the case must be removed and external battery connected to binding posts 
 3 and 4. The line is connected to binding posts 1 and 2 as usual. This set 
 can be used for ordinary Morse telegraphy, in which case the line is connected 
 to binding posts 2 and 3, and the small blocking screw which prevents the 
 switch of the key from being closed should be run down with a screw driver so 
 that the switch may be kept normally closed when not sending. 
 
 Previous models of the field induction telegraph set used a polarized relay 
 of a well-known connnercial form and, in addition, required a local battery 
 
 =^«CY 
 
 BATTEIRY 
 
 Fig. 2-28.— TELEGRAPH INDUCTION SET, THEORY OF OPERATION. 
 
 and local sounder to be connected to the relay tongue. The model 1912 set 
 contains what is known as a " polarized sounder." It consists of a I'egular local 
 sounder frame, underneath which is mounted a strong permanent magnet, the 
 cores of the coil forming the pole pieces of the magnet. The coils are so wound 
 that a current in one direction tends to increase the strength of the magnet and 
 in the other direction tends to decrease the strength of the magnet. The arma- 
 ture is adjusted by means of a .spring so that it remains in either the up or 
 down position when no current is flowing. When an instantaneous current 
 comes over the line due to the depression of the key at the distant station, the 
 direction of winding is sucli that the magnetism is suddenly increaseil and the 
 armature is drawn to the down pctsition. It remains there after the instan- 
 taneous current has ceased. Wlien tlie key at the distant station is opened and 
 an instantaneous current in flie opjiosite direction Hows through the instru- 
 ment, the magnetism of the cores is suddenly decreased with the result that the 
 armature flies to tlie up position and there i-omains. If the line is not too long 
 nor of too high a resistance, and particularly il' llicre aic not too many instru- 
 ments in .series on the line, the sound made by tills instrument Imitates very 
 closely that made by a local sounder. It may be that the imi)uls»'s from the 
 distant station will come in reversed, and for tiiis purpose the double-pole 
 
 (64)
 
 Telegraphy and the Induction Telegraph Set. — Chapter 2. 
 
 33 
 
 double-throw switch is provided whicli reverses llie connection of tlie sounder to 
 the line. If the sij,'nals come in reversed, it is only noccssary to turn tlic switch 
 over when they will come in in (he proper direction. 
 
 Thiorij. 
 
 Figure 2-28 shows the theory of operation of the held inductidii .set. (Cir- 
 cuit .1 comprises a key, primary of an induction coil, and battery. Circuit li 
 comprises the secondary of the induction coil and a polarized sounder or relay. 
 When the key is closed in circuit ^l there is an instantaneous electromotive 
 force inducetl in the secondary of the induction coil which causes an in- 
 stantaneous current to flow through the polarized Instrument and to bring 
 its armature to a certain position in which it will remain after the in- 
 stantaneous current has ceased. When the key in circuit ,1 is opened there 
 will be a similar instantaneous electromotive force tending to make a current 
 flow in the opposite direction in circuit B. This current will bring the arma- 
 ture of the polarized instrument to its other position, in which it will remain 
 after the current has ceased. As this secondary electromotive force may be 
 very high, and as polarized instruments can be made to operate on extremely 
 small currents, this induction telegraph arrangement will operate over lines 
 of high resistance, although the battery in the primai'y circuit may be one 
 of only a few volts. 
 
 INSTKUCTIONS FOR OPERATING. 
 
 To mstdll hatteries. — Open door of the battery case by releasing spring and 
 at the same time, placing the forefinger against the inside of the door through 
 the small aperture in metal case. Insert top battery unit, negative or flat end, 
 first and lower unit, positive or bottom end, first. 
 
 Fig. 2-29.— TELEGRAPH INDUCTION SET, CIRCUITS. 
 
 To use as an induction tclcgraijh set. — Coiuiect line to binding posts 1 and 2. 
 Lock circuit closing lever in the open position by unscrewing small setscrew 
 in key base until it projects sutRciently to lock the lever. If the sounder 
 fails to respond, change the direction of the current through the sounder by 
 throwing the reversing switch. 
 
 To vse as a closed-circuit telegraph set. — Remove batteries from case. Con- 
 nect line to posts Nos. 2 and 3; release circuit-closing lever by screwing locking 
 screw down until it is flush with the base. 
 
 (65)
 
 34 Signal Corps Manual No. 3. — Chapter 2. 
 
 Circnits. — As an induction telegrapli ; wlien the key is depressed current 
 from + of l)attery tlows through primary of coil, key, front contact to — of 
 battery. The instantaneous secondary current flows from secondary of coil, 
 through switch, polarized sounder (operating it), to binding post 2, line, distant 
 station, ground, binding post 1, secondary. The instantaneous secondary cur- 
 rent on opening the key follows the same path in the opposite direction. In- 
 coming impulses through line to binding post 2 go through the switch, polarized 
 sounder, key, back contact of key, binding post 1, ground. The purpose of 
 the back contact of the key is to short-circuit the secondary of the induction 
 coil and so remove its impedance from the circuit when receiving. It is not 
 essential and the key may be replaced by one having no back contact. 
 
 As a closed-circuit telegraph ; external battery one pole to ground, the other 
 to binding post 3. Batteries in instrument removed. Circuit, binding post 3, 
 front contact of key, key, reversing switch, sounder, binding post 2, line. Note 
 that circuit closing lever on key must be closed when not sending. 
 
 The resistance of the primary of the induction coil installed at present in 
 these instruments is very low, and the batteries run down very quickly in 
 service. All officers in charge of installations using these instruments should 
 keep this in mind and keep constant requisitions for new batteries going for- 
 ward. Wherever possible, as in permanent or semipermanent stations, external 
 battery should be installed. The type of external battery is innnaterial, about 
 G to K) volts lieing a good E. M. F. to use. 
 
 DUPLEX OPERATION. 
 
 The field induction telegraph set may easily be duplexed, following the simple 
 principles of the differential polar duplex system. The only additional ecpii])- 
 ment recpiired is an artificial line which can 1h> adjusted to have the same 
 resistance and, with long lines, the same capacity as the line itself. For duph'x 
 opei-atlon the line nnist be connected to binding post No. 2. The green wire nor- 
 mally connected to outside binding post U on the polarized sounder nuist be 
 shifted to inside binding post U, and the connecting bar joining inside ?' to 
 inside 1) must be in place. The artifical line goes between outside U and bind- 
 ing i)ost No. 1, and the ground is attached to binding post No. 1. 
 
 Arli/lcial line ior duplr.r.-^Auy resistance box, sliding rheostat, or other 
 variable resistance whose maximum value is equal to or greater than the 
 resistance of the line and distant instnnnent. If th(> line lias appreciable 
 capacity, as in the case of a long line or one in cable or laid on the gi'ound. a 
 balancing capacity can be constriictcd ol' the 2 m. f. condensei's used in common 
 battery tele[>liones. '^I'liey are cheaj) and easily obtained. Fractions of 2 m. f. 
 can be obtained by jiutting c<tndensers in series, (^lose static balance is rarely 
 necessary. 
 
 Instdlhition. — In large offices the operators should have in front of them only 
 the local sounder and key. All other apparatus should be in a separate room 
 under charge of an expert. This plan is especially necessary where duplex and 
 repeater sets are installed. In small ofiici's the circuits should be well installed 
 without unnecessary complication, and full instructions for operating and adjust- 
 ing should be furnished. Operators put in charge of such stations should receive 
 sftecial instruction before assuming charge, as the induction telegraph system is 
 not used commercially at present, in spite of its many advantages. 
 
 (66)
 
 ClIAPTKU 8. 
 TELEPHONY— THE CAMP TELEPHONE AND THE BUZZER. 
 
 Magnktism. 
 
 A bar of steel or iron which has the properties of attraftinj^ otlier pieces of 
 steel or iron is called a nuif^net. When freely suspended at its center it will 
 point north and south. It can also impart these powers to another piece of 
 iron or steel without losing any of its own. 
 
 The ends of a nfagnet are called its poles. The end which jxiints toward the 
 north is its north pole and the other end its south iKile. The north end of any 
 magnet will repel the north ends of all other magnets, but will attract all .south 
 poles. From this follows tlie law of magnetic attraction '* like poles repel and 
 unlike poles attract." 
 
 The force exerted by one magnet on another to attract or repel it is called 
 magnetic force. If iron filings be spread on a paper laid over a bar magnet, the 
 filings will arrange themselves about the magnet in curves which end at tlie 
 poles. These curves are called lines of force, and the whole space occupied by 
 the curves is the magnetic field of force, or magnetic field. It is assumed that 
 the lines of force come out from the north pole of the magnet, pass through the 
 air, reenter the magnet at the south pole and pass through it to the north 
 pole, thus completing the ]»ath. This path forms the magnetic circuit, and each 
 of the lines of force completes it without crossing or combining with any one 
 of the others in the field. A line of force always forms a closed h»op so that as 
 many lines enter the south pole as leave the north. 
 
 To make a magnet of a steel bar, place the bar flat on a table. Take the 
 south pole of a magnet and stroke the bar with it several times, always from 
 end to end in the same direction. The end of the bar first touched will then 
 become a south pole and the end where magnet last touched a n()rth pole. The 
 l)ar will then be a magnet. Or wind a few tin-iis of insulated wire around the 
 bar and pass a current of electricity through the wire for a slKtrt time, gently 
 tapping the bar with a hannner while the current is flowing. Upon removing 
 the bar from the coil it will be found to be a magnet. 
 
 If a piece of iron, mounted on a pivot so it is free to swing about, be phueil 
 in a magnetic field of force, the iron will move so that the greatest number of 
 lines of force of the field will pass through it. If the movable body be a magnet, 
 for example, a compass, it will turn, under the intluence of the field, so that 
 not oifly the greatest number of lines of force will pass through it. but also so 
 that its own lines of force will be in the same direction as those of the field. 
 Upon this fact is based the construction of many forms of electrical instruments. 
 
 If a bar of soft iron be placed in the field of a bar magnet, we will find on 
 testing the soft iron bar that it, too, has become a magnet having two distinct 
 poles. The iron bar is called the body under induction, the magnet the inducing 
 body, and this phenomenon magnetic induction. Magnetic induction is define<l 
 as the action and reaction which occur when a magnetic field makes a magnet 
 of a body placed therein. 
 
 (67) 1
 
 2 Signal Corps Manual No. 3. — Chapter 3. 
 
 ELECTROMAGNETISil. 
 
 Every wire throiigli which a current Hows possesses a magnetic tiehl arouiul 
 it. This fact can be proved by bringing a compass near it. The magnetic field 
 will act on the compass, and the needle will be deflected, showing not only the 
 presence of a magnetic field but also the direction of the lines of force. The.se 
 will be found to encircle the wire, always running from left to right, similar to 
 the direction in which the hands of a clock move, assuming that the current is 
 flowing directly away from the observer. 
 
 A solenoid consists of one or more layers of wire wound on a spool, usually 
 of nonmagnetic material, the length being great as compared with the diameter. 
 A magnet can be made of a solenoid by passing a current of electricity through 
 the wire. One end of the coil will be the north pole and the other the south 
 pole. If an iron bar be placed lengthwise through the coil while the current is 
 flowing, it will be found that the magnetism has been increased. This is due 
 to the fact that lines of force are much more easily set up in iron or steel than 
 in a nonmagnetic medium. A solenoid with such an iron core constitutes an 
 electromagnet. The current's magnetic field induces magnetism in a piece of 
 iron placed within its limits. 
 
 If the iron core of a solenoid is pulled out while the current is flowing the 
 attractive forjce of the solenoid will tend to pull the core back until its middle 
 point coincides with that of the solenoid. This principle is made use of in 
 many electrical devices, such as circuit breakers, ammeters, and telautographs. 
 Electromagnets are used in many kinds of instruments — electric bells, tele- 
 graph sounders, telephone receivers, and relays are some examples. The 
 strength of any electromagnet depends on the number of turns of wire and 
 the strength of current passing through it. 
 
 Electromagnetic Induction. 
 
 If a straight wire be moved across a magnetic field so as to cut lines of 
 force, a difference of potential will be set up between its ends. If the ends 
 of the wire be connected outside the field, a current will flow. This is called 
 electromagnetic induction, and the currents so produced are induced currents. 
 Upon the principle of magnetic induction is based the operation of all <lyuamos, 
 transform«>rs, induction coils, telephones, etc. 
 
 No distinction is made between tiie magnetic field of a ]iermanent steel 
 magnet and that of an electromagnet. P^ithor the magnetic field or the closed 
 circuit may be moved so long as the lines of magnetic force are made to cut 
 the wire of the closed circuit. Usually a coil of wire with an iron core (electro- 
 magnet) is used to produce the induction. It is called then the primary coil, 
 or simply "primary." The clo.sed circuit, or llie circuit under induction, is 
 then called the secondary coil, or " secondary." 
 
 Clurrent may ])e induced in the secondary l)y any of the following methods: 
 
 1. By moving either the i)riiMary or secondary while current is flowing in 
 the primary. 
 
 2. Ky making or breaking the primary circuit. 
 
 3. By altering the current in the jirininry. 
 
 4. By reversing the dirccdon of cuiM-cnl in the primary. 
 
 ;". By moving the iron core wliilc current Hows in the primarj\ 
 
 (08)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 3 
 
 El.ECTKOSTATIC INDUCTION. 
 
 It liiis Ih'cii fduiid that an iiisiilatcMl ciimliK-ioi;, siwii as a sheet of tin, an 
 aerial-line wire, or a cable Cduductor, has the property of receiving an elec- 
 trostatic charge when subjected to an electromotive force. If, for instance, a 
 conductor of the type mentioned above be thoroughly insulated antl one ter- 
 minal connected to one side of a battery, the other side of which is grounded, 
 p. certain amount of electricity will flow into the conductor and appear upon 
 its surface as an electrostatic charge, and the potential of the conductor will l)e 
 raised to that of the battery. The conductor in this condition is said to be 
 charged and holds an amount of electricity depending upon its capacity. The 
 charge is of the same polarity as the terminal of the battery to wliich the 
 conductor is connected. 
 
 Experiment has determined that a cliarge ran not exist on a conductor 
 except there be an equal and opposite charge induced upon the bodies sur- 
 rounding it, and this second induced charge is always of opposite polarity to 
 that of the first charge. If now the conductor be connected to the ground it 
 will lose its charge, but the charge of opposite sign on the surrounding bodies 
 will still be held, although having no connection with the first body or with 
 the source of electromotive force. This action by which bodies are charged 
 through an insulating medium constitutes electrostratic induction, and the 
 arrangement of two insulated conductors separated by an insulated medium 
 constitutes a condenser. The most common type of condenser is the Leyden 
 jar, in which the insulated conductors are sheets of tin foil, one placed on the 
 outside, the second on the inside of the glass jar, the latter forming the in- 
 sultating medium or dielectric, as it is commonly called. The capacity of the 
 condenser, or its ability to receive an electric charge, varies In direct propor- 
 tion to the area of its plates inversely as the square of the distance between 
 the plates and directly as the specific inductive capacity of the dielectric. 
 Where air is iised as the dielectric, this latter quantity is unity. The sub- 
 stances, other than air, ordinarily used as dielectrics have a specific inductive 
 capacity of two to three times as great as that of air. Condensers used for 
 telephone purposes where it is necessary to obtain considerable capacity in 
 very limited space are commonly built up of alternate layers of tin foil and 
 paraffined paper tightly pressed, so as to bring the layers of tin foil which 
 comprise the plates as close together as possible. The condenser is very 
 extensively used in telegraph and telephone work as a means of allowing 
 alternating or pulsating currents to pass while preventing the flow of direct 
 currents. This is the direct opposite of the functions of an impedance coil, 
 which imposes a very high resistance to varialtle currents while olTering little 
 resistance to the flow of direct current. 
 
 Principle of the Tuansformer. 
 
 An induction coil, or transformor, consists of two independent coils wound 
 on the same iron core and insulated from each other and from the core. Alter- 
 nating or interrupted currents in one of the coils (called the primary) produce 
 a variable number of lines of magnetic force in the inm core, and thus currents 
 are induced in the other coil (secondary), so that any E. M. F. that may be 
 applied to the primary may be changed to a higher or lower one in the second- 
 ary. The ratio of primary to secondary E. ^I. F. is equal to the ratio of the 
 turns in the two coils. For example, if there are 10 turns in the primary and 
 100 turns in the secondary, the induced E. M. F. will be 10 times greater than 
 that used in the primary. When a low E. M. F. in the primary is changed to a 
 
 (69)
 
 4 Signal Corps Manual No. 3. — Chapter 3. 
 
 higher one in the secondary coil, tlie latter loses in current strength what it 
 gains in pressure. For example, in the above case, if tliere is 1 ampere current 
 at 10 volts pressure in the primary and the E. M. F. of the secondary is 100 
 volts, only 0.1 of an ampere of current would he flowing through the latter. 
 This assumes that there are no losses in the transformer. This principle is 
 made use of to generate very high electromotive forces such as are used in 
 wireless telegraphy. 
 
 Theory of the Telephone. 
 
 In the act of speaking the vocal cords cause air vibrations, which, falling 
 upon the drum of the ear, are recognized by the auditory nerves as speech. If, 
 instead of falling on the eardrum, these vibrations should fall upon a diaphragm 
 wliich is capable of changing them into electrical vibrations, and there is some 
 means of transmitting them along a line and again reproducing at the other end 
 into similar air vibrations, we have the telephone. In order to understand the 
 action of the telephone it is necessary to define lines of force and explain two 
 simple laws of magnetic indviction. Lines of force are imaginary lines which 
 surround a magnet and indicate by their position and number the direction and 
 strength of its action. The laws of magnetic induction referred to are : First, 
 if a number of lines of force thread or pass through a coil of wire and this 
 number is increased or diminished, a momentary current will flow in the coil ; 
 second, if a coil of wire be wound around a permanent steel magnet and a 
 current of electricity be sent through the windings, it will, if in a certain direc- 
 tion, increa.se the strength of the permanent magnet, and if in the opposite 
 <lirecti(tn will diminish its strength. To understand how articulate speech is 
 transmitted by means of the telephone, let us take the simplest case of two 
 telephone receivers, A and /;. (•diiiuH'ted to tlic line as shown in ligurc .S-1. 
 
 Fig. 3-1.— TELEPHONE CIRCUIT SIMPLIFIED, USING TWO TELEPHONE RECEIVERS. 
 
 The telephone receiver (a more detailed description of which will appear 
 later) consists of a .soft-iron (lia]ihragm ])laced close to a permanent magnet. 
 Around the diaphragm end of this magnet is wound a coil of fine insulated 
 copper wire. Tlie air vibrations, caused by the act of si)eaklng, Tipon striking 
 the iron diaphragm at .1 cause it to vibrate. The vibrations of this dia- 
 phragm produce changes in the number of lines of force which thread through 
 the windings of tlie coll. These changes, according to the first law, produce 
 n current in the winding wliicli will be of greater or le.ss strength and in 
 opposite directions, following the vibrations of the diai)hragm. This varying 
 current proceeds along the line, and when it arrives at B will increase and 
 diminish the strength of IS's magnet. The variation of the strength of B's 
 magnet will jiroduce a varying jtnll on IVs diai)hragm and caus«' it to vibrate 
 in a manner similar to tiic diaiiluagni of ,1. The vibration of the <lia])hragm 
 
 (70)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 5 
 
 at li is recojiiiizt'd :is sduiid couiiii,:.' fioiii .1. 'I'lii' siiiijilc circuit shown in 
 figure 3-1 would iierniit a person to talk or hear, as the case may he. The first 
 modification of the circuit (fig. 3-2) is to introduce two teleiih<ine receivers 
 at the point A and two at the i)oint li, all l)eing in series, one serving as the 
 transmitting and tlie other as the receiving instrument at each point. 
 
 For certain reasons this type of receiver just described does not make a 
 good transmitter, and in practice is replaced hy a battery transmitter. 
 
 A complete local battery teleplione instrument consists of a receiver, local 
 battery transmitter, induction coil, magneto generator, call hell, and certain 
 switching devices whicii are contained in the magneto-generator box. 
 
 Fig. 3-2.— TELEPHONE CIRCUIT SIMPLIFIED, USING FOUR TELEPHONE RECEIVERS. 
 
 A complete common battery instrument consists of a receiver, transmitter, 
 induction coil, condenser, call bell, and hook switch. 
 
 LOCAL HATTEKY THAN SMISSION. 
 
 The battery transmitter depends for its action on the fact that a varying 
 pressure changes the resistance of carbon. The iransmiftcr cnnsisfs of a inmi- 
 
 Fig. 3-3.— TELEPHONE CIRCUIT, LOCAL BATTERY. Si'. 
 
 ber of carbon particles or granules in a jiropcr recei)tacle with a means ol 
 varying tlie pressure upon the granules in circuit with a battery and the coarst-- 
 wire winding of an induction coil. .The induction coil consists of a bundle of 
 soft-iron wires, surrounded by two windings of insulateil copper wire, one being 
 
 (-1J
 
 6 Signal Corps Manual No. 3. — Chapter 3. 
 
 of coarse wire, with few turns and low resistance, called the " primary." and 
 the other of fine wire, with a large number of turns and higher resistance, 
 called the " secondary." The relative position of these various parts of a local 
 battery instrument is indicated in figure 3-3, in which T is the transmitter that 
 contains the carbon granules through which the current from battery B flows. 
 T also contains a diaphragm which presses on the carbon granules, or is so 
 connected with them as to vary the pressure between the particles as the sound 
 waves fall on it. P is the coarse and S the fine wire winding of the induction 
 coil, which is connected to the receiver R and the line. The local battery 
 circuit includes B, P, H, and T. As the air vibrations fall on the diaphragm at 
 T they produce a change in the resistance between the carbon particles in contact 
 with it. This change of resistance causes the current flowing in the coarse-wire 
 coil to fluctuate, thereby inducing an alternating current in the fine-wire coil, 
 which goes to the line and receiver and reproduces speech, as has been explained 
 before. 
 
 COMMON BATTERY TRANSMISSION. 
 
 The common l)attery telephone operates similarly to the local battery tele- 
 phone in its essential details. The principal point of difference lies in the fact 
 that in conniion battery operation the current which flows through the transmit- 
 ter is furnished by battery installed at the central exchange in place of local 
 battery installed in the instrument, as in the case of the local battery tele- 
 phone. In the connuon battery telephone, battery is supplied over the same 
 wires that are used for transmitting speech. Figure 3^ shows most of the es- 
 sential parts of the common battery instrument. The induction coil for this 
 type of instrument is usually provided with primary and secondary windings 
 having more nearly the same number of turns and resistance than is found in 
 the local battei-y instrument. The receiver and transmitter are practically 
 identical with similar parts of the local battery telephone. The operation of a 
 typical set is as follows (referring to fig. 3-4) : 
 
 Fig. 3-4.— TELEPHONE CIRCUITS, COMMON BATTERY, SIMPLIFIED. 
 
 Direct curicni lioiii the positive side ol' (lie battery al liic ccnlral (>xchange 
 enters tlie iiistruincnt over the line l^\ jiasscs through the hook //, primary 
 winding 7' of liic induction coil, transmitter 7', and leaves the instrument by the 
 line //. If now the transmitter T is .sjMdien int<», the diaphragm, vibrating, pro- 
 duces a change in the resistance between the carbon particles i)laced near it 
 
 (72)
 
 Telephony — Camp Telephone and Buzzer. Chapter 3. 7 
 
 This varying resistance causes a corrospondiuK variail(»ii in the current tlowing, 
 which is received at tlie distant station as speecii. Tliis varying current in 
 the winding P acting upon the winding .S", whi<-h is placed upon tlie same core, 
 induces a curnMit in tlie receiver circuit conijiosed of the receiver R and tiie 
 winding S. In the case of receiving from a distant station the voice current may 
 be considered to follow the same course as that taken l)y the battery current. 
 This current, however, is varial»le, and in passing tiiniu;,di the winding /' of tlie 
 induction coll Induces a current in the receiver circuit. 
 
 In tlie normal condition of tlie instrument when not in use the receiver R 
 draws down the hook //, opening the contact, thus preventing the flow of battery 
 when the instrument is not in use. 
 
 Owing to the fact that the comni<m battery instrument depends for its opera- 
 tion on direct current in the line, the range of such operation is necessarily lim- 
 ited by the resistance of the line circuit. When the resistance of the line be- 
 comes so high as to materially cut down the strength of current, loutlness of 
 voice waves transmitted is correspondingly decreased. 
 
 The magneto generator is largely u.sed for producing the calling current. It is 
 the simplest form of electric dynamo and consists of an armature wound with 
 many turns of fine wire so moiuited as to enable it to be rapidly revolved be- 
 tween the poles of a permanent horseshoe magnet. Its theory dei»ends upon the 
 principle that if the number of lines of force passing through a closed coil be 
 varied a dilTerence of potential will be developed between the termijials of this 
 coil, and if an external circuit be connected electric current will flow, the 
 direction of which will depend upon the relative direction of the lines of force 
 and the movement of the coil. 
 
 The following from " Telephonology," by Van Deventer, clearly explains the 
 action of the magneto generator : 
 
 A magneto generator is shown in theory in figure S-H. N. S. represents 
 ends of the permanent magnets. The center opening is known as the " field." 
 In this is placed the revolving armaturo upon whicli is wound many turns of 
 insulated wire. The manner in which the current is generated will be under- 
 stood from a careful study of the figures. 
 
 C D 
 
 Fig. 3-5.— TELEPHONE MAGNETO GENERATOR. THEORY. 
 
 Magnetic lines of force are flowing aci-oss the field from the .V to the .^ pole. 
 To generrte a current the wire must move across the lines of force, and in .1 
 the maximum nunil)er of lines are passing through the coil. The number of 
 lines do not change until the armature has passed beyond the position shown in 
 
 (73)
 
 8 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 B ami the voltage is 0. A little beyond B the lines begin to decrease, and cur- 
 rent is generated until C is reached, when the remaining lines are shortened out 
 of the coil and the rate of change ^f the lines is greatest and tlie voltage is at a 
 maxinuun. This is the peak or highest point of the wave, shown in tigiu'e 3-6. 
 
 AMien the position shown in D is reached the lines of force pass through the 
 coil in the opposite direction and the voltage drops to 0. This continues as long 
 as the crank is turned. 
 
 While the wire is passing from the position of .1 to that in B a plus current, 
 or, as it is termed, a positive current, is generated if the north pole of the magnet 
 is on that side, while from that in C to D a minus or negative current is gen- 
 erated, because the wire is there subject to the influence of the south pole. 
 
 Fig. 3-6.— TELEPHONE MAGNETO, VOLTAGE CURVE. 
 
 Plus current is reprcseuted l).v Ihe sign + and minus currents by the sign — . 
 Current flowing flrst in ono dinM-tion and tlien in anotlier is called jdteniating 
 current, and flgure 3-G illustrates waves of a current of this kind given f)y a 
 magneto generator. On the left are flguros rei)rc.'-!enting the voltage, whil(> the 
 points 0, 1^ 2, etc., along the curved lines represent the ditferent positions 
 of the wire iluring one I'evolution and coi-respond to those in flgure 3-."). Start- 
 ing at line where there is no current, we will suppose that the upper 
 curved line represents plus current and the lower curved line minus current. 
 From this it will be seen that current from the telephone generator Hows first 
 in one direction and then the otliei-, the voltage increasing from to 1, and 
 then decreasing to 2, as the wire .-it this iM)int (see /?, fig. 3-5) is no longer 
 cutting across the lines of force, 'i'lie current then increases to 3 in the opposite 
 direction (.see C, fig. 3-;")), and again di'creases to (/>, fig. 3-5). 
 
 Magneto generators u.sed by (he Signal Corps are provided with an automatic 
 device which opens the ai'uiature circuit when the armature is at rest. 
 
 At tlie usual rate of turning the magneto generator by hand tlu> voltage will 
 be about 65 to 75 and the frequency about 15 complete cycles, or 30 alterna- 
 tions, per second. 
 
 In figure 3-7, A shows the generator armature on which are wound the many 
 turns of fine wire wliich are revolved in the magnetic field referred toabov(>. 
 It will be noted that this armature is made of a large number of thin stamped 
 metal pieces which are as.sembled on the arniiiture shaft as shown. In i)art /{ 
 of the above figure the generator armature, wound, has been placed within the 
 generator frame. Contact jiieces of the device for closing the generator circuit, 
 mounted in place on end of the generator frame, are shown in the figure. On 
 the other end a gear wliich meshes with a small piinon on armature shaft and 
 a crank for revolving arc shown. \\'hcn crank is roinled in clockwise direction, 
 tlie shaft, upon which is mounted the gi'ar. automatically protrudes througli 
 end of frame, thereby closing the two contact i)ieces which automatically ojuMi 
 when revolving of crank cejises. 
 
 C shows a conii)lete generator of Ihe 5-h,ii- type, with horseshoe ni;ignets in 
 place. 
 
 (leneriitoi's nse(| by the Signnl Corps ;ii-e provided with 3, 4, or 5 bars, depend- 
 ing upon the class of .service in whidi they ;ii-e |o be used. 
 
 (74)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 fig. 3-7.— telephone, magneto generator. 
 
 Receiver. 
 
 A linnd ree-oiver of the t.vi)o now usoil in tlii' Sii^nal I'oi'ii.s is .shown in tijrure 3-S. 
 It consists of a U-shaped permanent magnet t, to the ends of whieli are fastened 
 soft-iron jioie pieces p p. Over each pole piece i.s a coil of Hne wire wound on 
 a l)ohhin witli nonmagnetic metal heads. These coils are connected in series 
 in such a manner as to make the front end of one the north pole and the 
 similar end of the other the south pole when current flows through both coils in 
 a certain direction. The combined resistance of the.se coils connectetl in series is 
 about SO ohms. The pole pieces pass through the bottom of a metal cup C. 
 which is thus secured firmly in place. The diaphragm <!, of soft iron, tinned or 
 enameled, rests on the rim of this cup. A clamping ring / screws onto 
 the metal cup C. thus holding the diaphragm d firmly in place. The receiver 
 cords are connected to terminals »;, a strain cord lieing attached to the 1<m»j) of 
 tlu' magnet to provide against injurx- to the cord conductors. As tiius a.s.si-ml)le<| 
 
 46581°— 17- 
 
 -6 
 
 (75)
 
 10 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 tlie receiver is operative and may l)e so nsed in ease of accident to the contain- 
 ing shell and cap. This shell iS slips o\er the working parts of the receiver and 
 is held in place by the earpiece g, which screws onto the shell. The separation 
 of the diaphragm from the pole piece varies with the different types of receivers, 
 the usual separation being about 0.014 inch. 
 
 The operation of the receiver is as follows : 
 
 The pole pieces p p, being attachetl to the ends of the permanent magnet t, 
 have one a north and the other a south polarity and the magnetic circuit is 
 completed from one pole to the other through the soft iron diaphragm d, 
 which is, therefore, drawn toward the poles and held in constant tension. 
 If now a current flows through the coils in such a direction that the lines 
 of force due to it coincide with those of the permanent magnet, the diaphragm 
 will be pulled closer to the pole pieces, due to the increased strength of the 
 magnetic field. If the current flows in the opposite direction, the strength 
 of the magnetic fleld, due to the permanent magnet, will be reduced and the 
 diaphragm will spring farther from the poles. It will thus be seen that 
 wliether tlie lines of force due to the current in the coils assist or oppose 
 
 Fig. 3-8.— TELEPHONE HAND RECEIVER. 
 
 tliose due to the perniiinent magnet, a varying pull is produced on tlie dia- 
 phragm that causes vibrations in the latter in unison with the changes in 
 currcMit. The movement of the diaphra.gm will thus set up vibrations in 
 the surrounding air which may be perceived as sound. 
 
 Transmitter. 
 
 The operation of the transinitlci- di'pcnds on llie fact that the ehuMrical 
 resistanct; lietween two or more bodies, either in light or loose contact, varies 
 with changes in the j)ressure between the bodies. The change in resistance 
 is du(* to variatifin in the area of contact surfncc between the grainiles and 
 electrodes and not to compression of the caii»on granules themselves. In 
 general, the transmitters used by the Signal Corps dei)end on this principle. 
 A typical transmitter is shown in figure 3-9. A metal cup, .1, forms the front 
 electrode and is attadnMi to (lie diai)hragm for sending. The rear electrode 
 is held rigidly in a metal bridge i)iece, /*', which is in turn fastened to the 
 frame which sujijtorts tlie mouthpiece (I, and the remainder of the transmit- 
 ter. This rear electrode consists of a hard, ]>olished, carbon button, .1/, secured 
 
 (7G)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 11 
 
 to a brass hultim between two parts <if wbidi is clamped a mica ring or 
 diaphragm, O, the outer edge of whicli is clamped against the front electrode, 
 A, by means of a metal ring, S, which screws over .1. The space between 
 the front and rear electrodes is partly filled with hard granular carbon of 
 uniform size. Two dampening springs, B and C, are provided to prevent 
 vibration of the diaphragm at its natural period. 
 
 .-G 
 
 Fig. 3-9.— TELEPHONE TRANSMITTER. 
 
 The operation of the transmitter is as follows : 
 
 Current from a battery passes from one terminal, E, to the carbon electrode 
 through the granular carbon to the metal cup which forms the other electrode. 
 If the transmitter now be spoken into, the diaphragln and cup vibrate in 
 unison with the sound waves produced in the air, thus causing the pressure 
 between the front and rear electrodes on the granular carbon to vary and thus 
 change the resistance of the transmitter. Therefore, variations in the current 
 are set up which correspond exactly with the voice vibrations which reach the 
 transmitter diaphragm. 
 
 Ringer. 
 
 The magneto generator is commonly used in coimection with a polarized bell, 
 or ringer, as it is usually called, by means of which audible signals indicate 
 the incoming calls on the telephone instruments. The usual form of this 
 piece of apparatus is shown in ligure 3-10. In this figure c c represents soft- 
 iron cores upon which are wound coils of fine wire connected in series with 
 the line wires I I'. N S is a permanent magnet, and .t a .soft-iron armature 
 I)ivoted at its center. A slender rod terminating in a small metal ball is at- 
 tached to the center of the armature. Wlien no current is flowing through the 
 coil the permanent magnet A'^ S causes the upper ends of the cores to be north 
 poles and the opposite ends to be south poles. In this condition the armature 
 will be attracted by both cores and will rest against one or the other as may 
 chance to happen. If now current passes through the coils in series in such 
 direction as to increase the strength of the north pole /. and to make r south 
 
 (77)
 
 12 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 pole or weaker north pole, then / will nttract the end of the arnmtnre opposite 
 it. while c will repel this end of the armature or attract it with smaller force. 
 If the current is now reversed in direction so that / becomes a south pole or a 
 weaker north pole and e a stronger north pole, the action will be reversed, c 
 will attract its end of the armature and / repel its end or attract it with 
 
 Fig. 3-10.— TELEPHONE RINGER. 
 
 smaller force. With the rinser connected to the magneto generator as shown 
 in this figure, the armature will vibrate between the two gongs with the same 
 freciuency as the current produced by the hand generator, and a practically 
 continuous ringing soiind will result. Practically all of the ringers used by 
 the Signal Corps are wound to a resistance of 1,000 ohms. 
 
 Typks of Instruments. 
 
 The principles upon which depends the operation of the various parts of the 
 telei)hones have been explained in the preceding pages. The complete circuits 
 of tlie instruments of the various types ti.sed by the Signal (^orjvs will now be 
 lonsidercd. and it will be assumed that the operation of the various parts as 
 explained above is un<lerstood. and will not be discussed further. The instru- 
 ments herein described have been selected as being typical of those now in use, 
 and while .slight modifications of the circuits shown m;iy be encountered, it is 
 Itelieved that if u person fiimiliarizes himself with these circuits no trouble 
 will Ite experienced in mastering any which are slightly different. 
 
 It will be noted that desk t(>lephones of local battery and conmion battery 
 types employ precisely the same princii)Ies as wall te!ei>hones, but that it is 
 necessary to modify circuits iiiid relative i)Ositions of component iiarts in order 
 to meet requirements whereby the ringer (and magneb* generator in local 
 battery instrmnents) are .stationary and the transmitter, r(>ceiver, and book 
 switch (as u unit) are movable. To accomplish this, all manufacturers employ 
 
 (78)
 
 Telephony — Camp Telephone and Buzzer.— Chapter 3. 
 
 13 
 
 the woll-kiiow II (U'sk stand iiml riii^icr Ixtx. inniicctin^ Ihc two liy means of a 
 ll('Xil)le cord consisting? oT two or more conductors. Some manufacturers place 
 the induction coil in tlie ringer box and otliers in tlie base of the desli stand. 
 
 Circuits of the local battery telephone are as follows, reference being made to 
 figure 3-11. 
 
 licimj ctillcil. — Hoolc switcli contacts shown in diagram as closed would be 
 open, as receiver would not be removed from ho<ii< of hook switcli. Magneto 
 g«Mierator current enters at A. to ringer, to //. 
 
 CiiUinfi (Jistdiit fit(iti(rii., — Hook switch contacts shown in diagram as closed 
 would be open, as ivceiver would not be removed from hook of hook switch. 
 Revolving crank of magneto generator contact at r is closed and circuit is C to A. 
 thri>ugh one side of line, to ringer of distant station, through other side of line, 
 // to A. 
 
 It will be noted that ringer of station calling will also be operated. The 
 reader will bear in mind that the windings of ringers are of high impedance, 
 which, as previously explained, otTers a very high resistance to the high fre- 
 quency alternating currents transmitting the sound wfives, and for this reason 
 
 Fig. 3-11.— TELEPHONE, LOCAL BATTERY, CIRCUITS. 
 
 they can be connected direct across the line. The magneto .generators are 
 callable of operatin.g forcibly under usual line conditions api)roximately 10 
 ringers. 
 
 Li)itcni)ig. — Hook-switch contacts are closed as shown in diagram as receiver 
 should be removed from hook. A high voltage, high frequency alternating cur- 
 rent from distant telephone enters at L, passes through receiver, secondary of 
 induction coil, contact 1, hook of hook switch, and L'. 
 
 Tallinff. — Hook switch contacts are closed, as shown in diagram, as receiver 
 would be removed from hook. Direct current flows in primary circuit as fol- 
 lows: Battery, transmitter, contact 2, hook of hook switch, contact 1, primary 
 of induction coil. Voice waves fall on diajihragm of transmitter, varying 
 strength of current in primary circuit, thereby inducing in secondary of induc- 
 tion coil a high voltage and high frequency alternating current which is trans- 
 mitted to distant receiver by means of the following circuit : Secondary of in- 
 duction coil, contact 1 of hook switch, hook switch, L', one side of line, circuit 
 of distant telephone, other side of line, L. receiver, connection to induction c«)il. 
 
 A few commercial standanl local battery telephones are shown in ligures :i-V2 
 to .'i -15, which follow , 
 
 (70)
 
 14 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 ^ 
 
 
 m 
 
 A 
 
 ^^rj^M 
 
 1 
 
 rm 
 
 •-€ 
 
 I 
 
 1 
 
 f 
 
 
 
 3 
 
 1 
 
 ''^^^H 
 
 Fig. 3-12.— TELEPHONE, WALL, L. B., SUMTER MFG. CO., AND CIRCUITS. 
 
 Backboard 
 
 Shelf with hinges 
 
 Transmit (cr 
 
 TransmittLT mouthpiece 
 
 Tran.sniittor bracket 
 
 Transiniilcr-l)rackct arm 
 
 Ueceiver, hand 
 
 Receiver, hand, cord 
 
 Bindinm)()stline 
 
 I'.iiuiiiij,' post for receiver cord.. 
 
 li iiif,'('r, complete 
 
 k inj.'(T, KoiiK for 
 
 Iiin>,'('r, hammer and armature. 
 
 ItiiiKcr.coil (2 to a set) 
 
 Switch, hook, complete 
 
 Swilcli, hook, liook fcir 
 
 Switch, hook, contact springs. . 
 
 Coil, iiuiiiclion 
 
 Mat;ncl(), complete 
 
 iM;iKiicio, crank handle 
 
 Mafrnc|(),p('rni;uiot magliot. . .. 
 
 Ma>,'ncto, arnialiire for 
 
 Magneto, froiir for 
 
 Magneto, pinion for 
 
 Magneto, contact spring for. . . . 
 
 (80)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 15 
 
 l.OtAI. ItATTKKY WAl.I. TKI.KrilONK. 
 
 The circuits of tlic Iticiil hatlcry wall tclcpiioiu' nC tin- Suiiilcr Ti'lephone 
 Maiuifacturiuji; ('o.'s iiialce are sliuwn in tit^urt' 3-12. 
 
 Tliis tif,'ure imlicates the actual wirin;; nl' tlie instruineiit ami liic parts cor- 
 rectly, placed with relation to each other as they are niounteil in tiie instru- 
 ment. The circuits of this instrument may he traced as follows: 
 
 1. Incoming signals enter at line //, pass to hinge C, to hell /{. to hinge f", 
 and return to line L. The hook switch is shown in its normal position with the 
 hand receiver in place, all contacts heing open. 
 
 2. Outgtting signals pass from one pole of the generator (1 to the line /,. 
 through the distant instrument and return on 7/ to hinge C\ to the opposite 
 pole of the generator C. In this instrument the hells li are permanently con- 
 nected hetween the lines T. and //. as is also the generator (!. The latter, 
 however, by means of its switching device, is open circuited when not in 
 operation. 
 
 -O Lines O 
 
 lOOOco 
 
 )ffiK°X° 
 
 3 conductor cord 
 
 Fig. 3-13.— TELEPHONE. DESK, L. B.. SUMTER MFG. CO.. CIRCUITS. 
 
 (81)
 
 16 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 3. Tlic IdCiil li;itt(M-y aiul 1 i-aiisiiiitlcr cii-cuits pass Iroiii the l)alt('i-y llirou.iili 
 the transiiutt«n' and Iht' cdarse-wire windinir of the iiiductiun coil throusli the 
 hook switch //, wliich now has all contacts closed, to the opposite pole of the 
 battery. The receiving circuit passes from L' to the liook switch H, through the 
 tine-wire winding of the ind\iction coil, through the receiver R, to the line L. 
 
 T.OCAL BATTERY DESK SET. 
 
 In figure 3-13 is shown circuits of the local battery desk telephone of the 
 Sumter make, as furnished to the Signal Corps. The usual bridging circuit is 
 used. The diagram shows the actual wiring as it is found in the instrument, 
 and the vario\is parts are shown Ci)rrectly placed with respect to each other. 
 
 Fig. 3-14.— TELEPHONE, WALL, L. B., GARFORD MFG. CO., CI RCUITS. 
 
 The wiring of llie (Jarlurd local ballery wall iclciilicnic wliicli is furiiisjied 
 by the Signal ('orps, is shown in tigure .'{-14. In Ibis li.gure. .1 shows a sim- 
 plified circuit, and li the wiring as actually found in the instrument with tb(> 
 parts correctly locateil with respect l<i cadi otlicr. 
 
 FigUH' .'V-1."> shows the C.-irford local batlcry desk telephone and the circuits 
 employed witli tliLs in.'<trumcnl. 
 
 (82)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 17 
 
 Fig. 3-15.— TELEPHONE, DESK. L. B., GARFORD MFG. CO. 
 
 Ringer box, complete 
 
 Ringer box, door for 
 
 Ringer box, screw fastener for 
 
 Ringer box, binding post, line 
 
 Ringer box, binding post, main cord 
 
 Ringer, complete 
 
 Ringer, gong for 
 
 Ringer, hammer and armat ure 
 
 Ringer coil (two to a set) ". 
 
 Ringer, armature adjusting screw 
 
 Magneto, complete (give number of bars; 
 
 Magneto, crank handle 
 
 Magneto, permanent magnet 
 
 Magneto, armature for 
 
 Magnet o, gear for 
 
 Magneto, pinion for 
 
 Magneto, contact spring for 
 
 Coil, induct ion 
 
 Desk stand, complete with transmitter, receiver, and main cord . 
 
 Desk stand, head for 
 
 Desk stand, hook switch 
 
 Desk stand, switch hook 
 
 Desk stand, cord terminal block 
 
 Desk stand, cord terminal block, binding post for 
 
 Transmitter, complete 
 
 Transmitter, mouthpiece for 
 
 Receiver, hand, complete 
 
 Receiver, shell for 
 
 Receiver, cap for 
 
 Cord, main 
 
 COififOX UATTKKY TKl.EPHONK. 
 
 In general it may be .'^aiil that the parts used in the coininon liattery wall 
 telephones are similar to those used in the local battery. 
 
 It will usually be found that the priuuiry »»f the induetion o»ii use«l in the 
 common btitterv instruments is of lusher resistance, and that the ratio l>etween 
 
 (83)
 
 18 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 tlu> primary and secondary windiii^is of (ho induction coils arc <iuil(> dilToront. 
 Tlio distin^iuishinj; difference between the connnercia! local battery telephone 
 and common battery telephone is that the connnon battery instrument is not 
 equipped with a magneto generator for calling, or batteries for furnishing 
 current for transmitting sound waves, and is equipped with a condenser in 
 series with the ringer. The secondary of induction coil in the local battery 
 telephone is in series with outside line and receiver when receiver is removed 
 from switch hook, while with the common battery instrument under similar 
 ci)nditions the secondary of induction coil is in series with receiver, transmitter, 
 and condenser, the primary of induction coil being in series with transmitter 
 and outside line. By reference to figure 3-16, which shows circuits of the 
 common battery telephone, it will be noted that the paths of both the current 
 in primary of induction coil and current in secondary of induction coil traverse 
 the same line through transmitter. They do not interfere with each other in 
 any way, and the transmitter, being of low ohmic resistance and practically 
 zero impedance, offers comparatively no resistance to either. 
 
 LINE BINDING POSTS 
 
 -o o 
 
 Fig. 3-15.— TELEPHONE, WALL, C. B.. WESTERN ELECTRIC CO., CIRCUITS. 
 
 The reason for this rearrangement of component parts is due to tlie fact 
 that battery for furnisliing necessary current for operation is remote from 
 location of telephone and is conduclod to instrument l)y means of tlie line wires. 
 The battery lisually consists of 12 or If) cells of stora.ge battery having a voltage 
 of 24 or IM), resjiectively. 
 
 While the ohmic resislaiicc of tlit^ I'ingcr is com])arativ(>ly high, usually 
 being l.(MM) ohms, it will he svrii thiil by connecting this direct across the lint* 
 a considerable waste of curreni would ensue, conseipiently the condenser wliich 
 oi»ens tlie direct current circuit is jihiced in seiies with the ringer across tlie 
 line. An((tlier reason for this condenser is that with the commercial connnon 
 l)attery telei)hone the o))erator at switchboard is sigiinled by merely removing 
 receiver from liook, thereby closing the direct cm-rent circuit through a mag- 
 netic device at switchltoard. The <levices are ordinarily of 200 ohms resist- 
 
 (84)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 19 
 
 iuifo nn«l opprnio on iipiirfixiinaloly (».oi of :iii jihiiuth of ciirnMit, so that Ity 
 roferriuf; to Oliin'.s law in cliapter 1 tlit? reader can readily determine that this 
 .signal would he held closed if the l,00()-ohin ringer were connected directly 
 across the ordinary line without condenser In series. 
 
 A few commercial standard common batlery telephones are shown in figures 
 o-lT to [i--- which follow. 
 
 
 
 THEORY 
 
 A B 
 
 Fig. 3-17.— TELEPHONE, WALL. C. B., SUMTER MFG. CO.. CIRCUITS. 
 
 The circuits of the common battery wall telephone of the Sumter Manu- 
 facturing Co. are shown in figure 3-17. .1 shows the wiring of the instrument 
 and the parts with correct relation to each other, and B a simplified circuit 
 diagram of the in.strument. The operation of the instrument is as follows: 
 
 Assuming that the receiver is in place on the hook switch, the incoming 
 ringing current will pa.ss from the line // through the hells li, condenser C\ to 
 the line L, ringing the bells B. The hand receiver lieing removinl from the 
 hook switch, the contacts at II are closed. In this condition the battery from 
 the central exchange passes from L' through the coar.se-wire winding of the 
 induction coil, through the transmitter to the line A,. Rattery als«» pas.ses 
 from the bells /?, secondary or fine-wire winding of the induction coil, re<'eiver 
 A', transmitter T, to the line /,. The resistance of this second path is very 
 
 (85)
 
 20 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 imich greater than lliat of tlie lirst path, so tliat thi- current Mowing in this 
 liifih resistance i)ath may l)e considered nejilijiible. If now the transmitter be 
 spolven into, the current flowing through the transmitter will vary by reason 
 of the varying resistance of the transmitter caused by varying pressure between 
 the carbon granules. These fluctuations in current result in a fluctuating 
 
 
 Fig. 3-18.— TELEPHONE, DESK, COMMON BATTERY. 
 
 Part 
 No. 
 
 Reference 
 
 No. 
 
 De.sk stand, complete, with receiver, transmitter, and cord. 
 
 Bell box, complete 
 
 Coil, induction 
 
 2 m. f . conden-ser 
 
 Hook 
 
 Ilookswitch, complete 
 
 iiecei ver, hand 
 
 Receiver, .shellfor 
 
 Kecfiiver, earcap for 
 
 Ue<'pi ver diaphragm 
 
 Receiver diaphruKm, retaining ring. 
 
 {'ord, receiver 
 
 Cord, main 
 
 Tran.smitter 
 
 Transmitter, diaphragm for 
 
 Transmitter, mouthpiece for 
 
 Binding post, line 
 
 (SC)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 21 
 
 
 ■f 
 
 p 
 
 ^ 
 
 
 1 
 
 
 
 1 
 
 
 
 
 
 »* . 
 
 j 
 
 1 V^^^ 
 
 i 
 
 I 
 
 
 Mwo't'-ly II 
 
 
 
 7^ 
 
 ^^r 
 
 
 
 
 
 
 / f v^n 
 
 -F"-'ti\ 
 
 1 <^»^ 
 
 1 ^^ 
 
 
 SI 
 
 p 
 
 III 
 
 i»«i\J 
 
 V_ 
 
 -^ 
 
 ^^^^- \^ 
 
 Fig. 3-19.— TELEPHONE, WALL, COMMON BATTERY. 
 
 Part 
 
 No. 
 
 Name. 
 
 Bindinf; post, line 
 
 Coil, induction 
 
 Coil, indviction, terminals. 
 
 Condenser 
 
 Hook 
 
 Hook, switch, complete. . . 
 Receiver, hand 
 
 Refer- 
 ence 
 No. 
 
 Part 
 No. 
 
 Name. 
 
 Receiver, shell for 
 
 Receiver, ean-ap for 
 
 Receiver diaphropm _. - . - 
 
 Receiver, diaplirapm. retaining ring. 
 Rei-eiver, cord for, with terminals... 
 Ringer, complete 
 
 Refer- 
 ence 
 No. 
 
 (87)
 
 22 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 current in the primary of iutluotiou t-oil in telephone at distant station and in- 
 duce in the secondary of same induction coil a high-voltage, high-frequency 
 alternating current which affects the receiver, thereby reproducing speecli. In- 
 coming speech follows the same circuit as that taken by the battery from the 
 central exchange. This voice current, however, being pulsating in character, 
 induces a current in the fine-wire winding of the induction coil. This current 
 passes through receiver R. hook switch, transmitter T, and condenser C. thus 
 reproducing in the receiver R the sounds impressed on some distant transmitter. 
 The condenser also serves to strengthen the effect of the induced current in R 
 by reason of the varying potential across its terminals. 
 
 B/ue 
 
 Fig. 3-20.— TELEPHONE, WALL, C. B., N. E. CO., CIRCUITS AS INSTALLED. 
 
 Figure ;{-lS shows (lie gonci-al arraiigcnienl of a conmioii hallery desk tele- 
 phone ami figure .'{-ID shows the general arrangement of tiie common battery 
 wall telepiione. The circuits siiown or modilicalions of lliem are used by all 
 maiHifacturers and the general appearance of (lie apparatus closely resembles 
 that ."iliown in the illustrations. 
 
 (88)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 'J 3 
 
 Figure 3-20 shows tlic ciiciiils as iiistallt'd of a Noiili i;it'<iri<- (Jo. C. B. wall 
 teloplione. Fi;;uiv ."i-LM sliows the circuits as luniisiied in the desk set type 
 of the same iuslruuieiil. 
 
 Fig. 3-21.— TELEPHONE, DESK, C. B., N. E. CO.. CIRCUITS AS INSTALLED. 
 
 Fifjure ',i-2'2 shows the circuits, as installed, of a coininoii liattery desk tele- 
 phone, having the induction coil located in the base of the desk stand. 
 
 ^ ©"fT* 
 
 THEORY 
 
 BEJ_LBOX DESK STAND 
 
 Fig 3-22.— TELEPHONE. DESK. C. B.. GARFORD MFG. CO. 
 CIRCUITS AS INSTALLED. 
 
 The Camp Telephonk. 
 
 This teleplione, wliicli supers»^h>s the field iclcphiMic. was develop*^! I>y the 
 Signal Corps f(»r use In connection with camp leleplione systems anil small arms 
 target range systems, and may he installed in tents ami structure.s. or eon- 
 
 (89)
 
 24 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 sidered a portable iut;triiiiient for use in llie Held for testing lines or other 
 purposes. 
 
 It is of local battery type. The battery employed is one unit of tungsten 
 type A described in chapter No. 1. Figures 3-23 and 3-24 illustrate this tele- 
 phone, it being sliown dismantled in figure 3-24 to facilitate identification of 
 parts in connection with the preparation of reipiisitions for renewals. 
 
 The first lot of these instruments M'as equipped with 2-bar magnetos and 
 due to its limitations the instrument could not be used for long-distance work. 
 The new model of this instrument will be equipped with a 3-bar magneto, em- 
 ploying a special high grade steel for permanent magnets, and while in other 
 featin-es there may be a slight deviation from following description, it is be- 
 lieved that figures 3-23 and 3-24 can be used in preparing requisitions, it being 
 merely necessary to state " For Camp Telephone, o-bar magneto type." 
 
 Fig. 3-23.— TELEPHONE, CAMP, AND CIRCUITS. 
 
 Part 
 No. 
 
 Name. 
 
 Case complete 
 
 Cflver^ complete with hinges 
 
 Circuit (liaRram frame 
 
 Circuit (I iajjram , 
 
 Circiiil iliagram, celluloid cover 
 
 Metal lia^o for case 
 
 Wire not I inn frame complete 
 
 \\ir(( IK'II inj; 
 
 ('arryirm strap, complete 
 
 Fittmg and ring for carrying strap. 
 
 Reference 
 No. 
 
 The iiistniiiiciit is made as compact as ))r;iclical)l(> and is contained in an 
 oak ca.se 4.| i)y 7 by 10 inches high. The loj) consists of a metal hinged cover 
 with circuit diagram on inside, iicld rigid when closed by a si)ring sua]) which 
 can be readily ii'Iciiscd by depi-essing a bnllon. 'I'lie bottom of case is covereil 
 
 (00)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 by a ll:inj;ed piece ol" iiietal, the llaufie projecting,' ap])i-i»xiinatel.v one-iialf iiirji 
 up sides of case. Throuf^h one side of case are six three-eijiiitli iiicii liolrs 
 which are covered on the outside by a close mesh metal screen held in phue 
 by a metal frame. These apertures are for the purpose of allowing the ringer 
 to be distinctly heard. Tlie case is ecpiipped with a sub.stantial, arljustabh' 
 carrying strap, each end of which is fastened to case by means of hinged metal 
 rings. 
 
 Fig. 3-24.— TELEPHONE, CAMP, DISMANTLED. 
 
 Part 
 No. 
 
 Name. 
 
 Base complete 
 
 Coimeotinj; lilock, complete with binding post.s. 
 
 Bindinp post complete 
 
 Socket for h;unl-set cord (3 to a set) 
 
 Haiul set complete 
 
 ITand-set cord 
 
 Kiuid-set receiver 
 
 Kaiid-set receiver cap 
 
 Hand-set transmitter 
 
 Hand-set transmitter cap 
 
 Battery case 
 
 Hat tery-spring catch 
 
 Hattery spring and support 
 
 Battery, tungsten, type A (1 unit per set) 
 
 Magneto complete . ." 
 
 Magneto, crank handle for 
 
 Magneto, permanent magnet for 
 
 Magneto, contact spring for 
 
 Magneto, armature for 
 
 Magneto, gear for 
 
 Magneto, pinion for 
 
 Kinger 
 
 Ringer, pong for 
 
 Itinger. hammer and armature for.. 
 
 liinger, coils (2 to a set ) 
 
 Ringer, armature adjusting screw 
 
 Ca-se for hook switch 
 
 Hook switch, complete 
 
 Hook switch, contact springs for 
 
 Hook switch, hook for 
 
 Posts, binding, for external battery 
 
 Reference 
 No. 
 
 46581°— 17 7 
 
 (91)
 
 26 Signal Corps Manual No. 3. — Chapter 3. 
 
 A .small l'-l)ar inuiineto generator, small ringer, induction coil, alnmlnum 
 chamber for the single unit of tungsten type A dry battery, liard rnl)I)(M- block 
 upon which are mounted line binding posts, plug connections for the handset 
 used with the instrument, hook switch and hook operating it and auxiliary 
 battery binding posts are all mounted on a common base which may be readily 
 removed from case after removing magneto generator crank, metal housing 
 for it and three screws which extend through the case. 
 
 The instrument may be operated with cover closed which is highly advanta- 
 geous in inclement weather. To accomplish this there is a suitable opening for 
 leading out the 3-conductor cord to receiver and transmitter, the two latter 
 being mounted in the form of a unit, termed a handset. This handset consists 
 of a transmitter and receiver mounted on a metal piece and is so designed 
 that when the transmitter is normally placed to the mouth, the receiver is 
 automatically adjusted to the ear. 
 
 The hook of hook switch is so designed that it protrudes through case. 
 When it is desired to transport the instrument or to remove the base upon 
 which is mounted all the parts of the instrument, it is merely necessary to de- 
 press the hook and push it toward the base. By this arrangement the hook is 
 not only held in the down position, thereby opening the battery circuit, but it 
 is also protected. 
 
 The aluminum chamber for housing the single unit of tungsten type A but- 
 tery is equipped with a spring catch so located that when upper hinged piece is 
 depressed to proper position, the battery compresses a helical spring, thereby 
 insuring continual contact. The base is equipped with two screw binding posts 
 which may be used to conect leadc to an outside battery in the event of there 
 being no tungsten type A batteries available. 
 
 An aluminum frame which is supported on the base previously mentioned 
 forms a compartment for the hand.set when instrument is being transported. 
 When the instrument is installed for a temporary period, unless in actual 
 operation, the proper place for the handset is hanging .on the hook of hook 
 switch, there being a ring on the handset for this purpose. 
 
 A small screw driver which will fit practically all the screws used in the 
 construction of the instrument is supported by the metal frame and is furnished 
 with each instrument. The instrument complete weighs approximately 11 
 pounds. 
 
 TiiK si;i;\ i( K i!i'/./Ki;. 
 
 The buzzer is strictly a portable instrument and is issued to troops in the 
 held for use in connection with all kinds of lines of conununication. It may be 
 used as a teleplione or for sending customary IMorse or Continental ('ode signals 
 and for that reason it is .specially adapted for field use. 
 
 W 111 'II it becomes impracticable to transmit messages telephonically, due to 
 line becoming impaired or for other reasons, the usual telegraphic signals can be 
 transmitted and are received in distant telephone receivers in the form of a 
 high-pitched hum, somewhat similar to radiotelegraphic signals. These sig- 
 nals have been exchanged between two of these instruments after the line wire 
 had been sevt^red, both the ends, however, being slightly grounded. 
 
 The service buzzer, which is the latest approved instnniu>iit of this type of 
 apparatu.s, replaces the field buzzer, the cavalry buzzer, and the field artillery 
 telephone anri hereafter is the .standard issue where the above-enumerated 
 obsolete apparatus is involved. 
 
 In the first i)art of this chapter is explained how a circuit t>f high E. M. F. is 
 obtained by means of two coils of wire wound on a soft iron core in connection 
 
 (92)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 27 
 
 with the telephone. Thi.s method may he tei'med mutual induction and i.s em- 
 ployed in the service buzzer. A high E. II. F. can be obtained by means of one 
 coil of wire wound on a .soft iron core, the latter method being termed .self- 
 induction. In' order that operation of service buzzer may be clearly understood, 
 the theory of the field buzzer will first be explained. 
 
 The principle upon which the original firlil buzzer operates depends upon the 
 effects of self-induction; i. e., the comparatively high self-induced voltage devel- 
 oped at the terminals of an electromagnet (coil with iron core) when the cur- 
 rent through the circuit is suddenly interrupted. The interruptions are auto- 
 matically produced by a circuit breaker, which is described later. During the 
 interval of time required for the current to reach its maximum value, the field 
 of force expands in direct proportion to the current strength until it also 
 reaches maximum value. The current strength being kept constant, the mag- 
 netic tield is of constant value. Any variation in current strength produces a 
 corresponding variation in the strength of the magnetic field; therefore, when 
 the circuit is broken and the current rapidly falls to zero the field of force also 
 collapses and disappears. The energy furnished by the current and stored up 
 in the magnetic field is thus returned to the circuit and tends to sustain the 
 original current, as is noticed by a bright spark appearing at point of break. 
 
 K 
 
 \^ 
 
 mm 
 
 R 
 
 B 
 ■o-lllll ill 
 
 
 Fig. 3-25.— BUZZER, FIELD, SIMPLIFIED CIRCUIT. 
 
 On " make," then, the whirls spring out from and cut the wire, inducing 
 therein a current opposed in direction to inducing current. On " break " the 
 whirls collapse, again cutting the wire and inducing therein a current having 
 same direction as inducing current. The phenomena resulting from such cutting 
 of a wire by magnetic lines of force is called self-induction. 
 
 When the circuit contains a coil, the above-noted effects of self-induction are 
 much greater. If the coil contains an iron core the effects of self-induction 
 are still more i)ronounced. 
 
 To make clear the action of the buzzer, let us consider the diagram (lig. 
 3-25) : 
 
 B is a battery of five dry cells; K is a ki\v for making and breaking the 
 circuit ; E an electromagnet ; It a telephone receiver. 
 
 When the key is closed there is a rush of current which readn-s its maxi- 
 mum strength almost instantly. Simultaneously there is built up a magnetic 
 field of forie around the elec-tromagnet. Now, if the key be opened, a pro- 
 nounced click, of momentary duration, is heard in the receiver, which is caused 
 by a .self-inducod current of high E. M. F. produced by the collapse of the mag- 
 netic field around the coil. This induced current wouhl spark a<-ross break 
 at the key if there were not an alternate complete circuit through the re- 
 ceiver. 
 
 (93)
 
 28 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 The more rapidly the circuit is made and brolven by closing and opening 
 tlie key, the greater the rapidity with which clicks in telephone follow one 
 another, until, if the interruptions recur sufficiently often, the sounds in the 
 receiver appear to be almost continuous. 
 
 K 
 
 ^" 
 
 E 
 
 M 
 
 B 
 
 h|i|i|i|i 
 
 trnf" 
 
 Fig. 3-26.— BUZZER, FIELD, SIMPLIFIED CIRCUIT WITH INTERRUPTER. 
 
 If we introduce an automatic interrupter into the circuit (fig. 3-26), a loud 
 buzzing sound is heard in the receiver whenever the key is closed, and the 
 dot and dash of the Morse alphabet are thereby produced by making short 
 and long contacts with key. 
 
 The action of the interrupter or circuit breaker is as follows : 
 
 When the circuit is made by closing the key K, the current flows through 
 coils of the electromagnet E, magnetizing the iron core JA, which, in turn, at- 
 tracts armature A. As soon as the armature is withdrawn from contact S 
 the circuit is broken ; as a result, the core becomes demagnetized and arma- 
 ture A springs back against S\ thus again closing the circuit. This action con- 
 tinues so long as key K is kept closed. 
 
 If instead of interrupter we substitute therefor a transmitter (fig. 3-27). then 
 when the key is closed current flows from + side of the battery through the 
 coil to the lower disk (stationary) of ti'Jinsmitter, through loosely packed carbon 
 granules to upper disk (movable) which is attached to the diaphragm, to key, 
 to — side of battery. 
 
 7 
 
 ^ Upper disc 
 Lower disc 
 ■a 
 
 mm 
 
 s 
 
 B 
 
 llho- 
 
 
 Fig. 3-27.— BUZZER. FIELD, SIMPLIFIED CIRCUIT WITH TRANSMITTER. 
 
 E.xcept wlien this circuit is first nuide, there is no evidence of .self-induction 
 in the circuit until the transmitter is spoken into, tlien the sound waves of the 
 voice striking the diaplu'agm cause it to vibrate. The carbon granules between 
 tlie carlion disks are thus subjected to varying pressure; this causes a variable 
 n^sistiuice in the circuit, and the resulting current is a pulsating one (uniform 
 ill dirfftion, but varying in strcngtli). The ell'ect of the varying current i)assing 
 through the circuit. is. to increa.se and decrea.se the field of force built up around 
 
 (04)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 29 
 
 tho wire. This changing field of loi-cc in iiiin inuchicis iIm- ctTpfts of sHf- 
 inductidii, and tliese effects are i»artk'ularly noticaljlc in euil h'. 
 
 Tli«' inductive property of the coil is thus enipioywl to uuKnient the com- 
 l)artively weatc primary current to (»ne of hifih 10. M. F., which intensifies the 
 vibration of tiie receiver diapln-a^ni, tliese vibrations beinj: receive<l by the ear 
 as articulate speech. 
 
 
 ^^^s 
 
 B 
 
 mmf^ 
 
 o o 
 
 Line to distant station 
 
 Fig. 3-28.— BUZZER, FIELD, SIMPLIFIED CIRCUIT WITH TRANSMITTER AND INTER- 
 RUPTER. 
 
 The sounds thus produced are not as loud as those produced by the interrupter 
 even though the same number of cells are used, for the reason that in the latter 
 case the current is completely interrupted (circuit broken), whereas in the case 
 of the talking circuit, current is always flowing, but is varied in strength; 
 therefore the resulting field of force never reduces to zero, the cutting of the 
 wire is consequently less, and the effects of self-induction are diminished. 
 
 If we now combine the two circuits described above in one diagram we have 
 the simplified buzzer diagram which is shown in (fig. 3-li8). 
 
 Tdegraph Line 
 
 Condervser 
 
 Buzier 
 
 Condenser 
 
 o 
 
 Buzzer 
 
 Fig. 3-29.— BUZZERS. CONNECTED TO A TELEGRAPH LINE. 
 
 An examination of this figure shows that the only change made is th»' intro- 
 duction of two terminal binding posts, one of which is connected to the line. 
 the other to the ound. If a similar instrument is coniuH-te<l at the distant 
 stations, the currents traversing home receiver also pass through distant 
 receiver. 
 
 O.l)
 
 30 Signal Corps Manual No. 3. — Chapter 3. 
 
 The utilization of existing telegraph lines as a part or the whole of a circuit 
 for buzzer and telephone working, at the same time not interfering with the 
 use of the wire for Morse working, may be etfected by using condensers inter- 
 posed between the line and the buzzer. (See fig. 3-29.) 
 
 The pulsations of the ordinary INIorse sending are comparatively slow. The 
 condensers, therefore, act as a very large resistance, and no appreciable effect 
 will be noticed in the telegraph line. 
 
 The very rapid pulsations produced by the buzzer or transmitter, however, 
 will permit of transmission from one buzzer to the other with little diminution 
 of sound. 
 
 Figure 3-30 shows the circuits of the service buzzer. It will be noted that 
 with the field buzzer if a line of low insulation resistance is utilized a heavy 
 drain on the batterv will ensue, due to battery being connected to the line, 
 while with the service buzzer under like conditions a heavy drain will not 
 exist, due to battery being connected in a local circuit which does not 
 physically connect with line. It will also be noted that a condenser which 
 can be cut out by means of a short-circuiting switch is contained in the instru- 
 ment and connected in series with the line. This condenser is for use when 
 it is desired to use an existing telegraph line. (See fig. 3-29.) Two units 
 of tungsten type A dry battery are used with the service buzzer for furnishing 
 the necessary primary current, both being in circuit when sending telegraphic 
 signals, and one only being in transmitter circuit for telephone communica- 
 tion. 
 
 The circuits of the service buzzer may be classed as follows: 
 Primary sending circuit — telegraph. 
 Secondary sending circuit — telegraph. 
 Receiving circuit — telegraph. 
 Primary sending circuit — telephone. 
 Secondary sending circuit — telephone. 
 Receiving circuit — telephone. 
 
 These circuits may be traced as follows, i-eference being made to figure 3-30 : 
 
 PUIMAKY SENDING CIRCUIT TELEGRArH. 
 
 S. P. D. T. knife switch marked " Sio " must he closed on side marked 
 "buzzer." Upon depressing key K, circuit is as follows: Positive end of bat- 
 tery, through primary of induction coil, to A to B, contact 1 of key, lever of key, 
 contact 2, vibrator, to negative end of battery. 
 
 SECONDARY .SENDING CIRCUIT TELEGRArH. 
 
 /S. P. D. T. knife switch marked " Siv " is closed on side marked " buzzer." An 
 A. C. current of high E. M. F. is induced in secondary winding of induction coil 
 by interrupted current in primary and its path is as follows: G, earth or one 
 side of line (if metallic circuit is used); "receiving circuit, telegraph" of 
 distant buzzer, other side of line, L, contact 1 of key (key is depressed), li, A, 
 otiicr side of secondary winding of induction coil. 
 
 RECEIVING CIRCUIT — TEI-EGRAni. 
 
 »S'. /'. />. 7'. knife switcii marked "Sw" is closed on side marked "buzzer." 
 A. C. current of high 10. M. F. reaches L from distant instrument by one side of 
 line, contact 3 of key (key raised), receiver, C, switch marked " Sw," G, other 
 side of line to dislaiit iiisti-uiiiciit. 
 
 (00)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 31 
 
 rui.M.MtY senium; ciitci ri'^ — tki.ki'iium;. 
 
 S. r. J). T. knife switch iiiariaMl " Hw " i« closoti on side marked " talk " ; fr(»m 
 positive end of i)attery tliroufrli primary winding of indnction coil, to .1, to li, 
 tln-ouKh blade of switch marked " .S'lo" to C, through push-l)Utton switcli 
 marked "PR," throuj,'li transmitter t(» netrative side of one unit of the luii^rsten 
 type A battery. 
 
 BOTTOM VIEW OF BACKBOARD SHOWING WIRING 
 
 
 conTI 
 <T7~T^ — ^ 
 
 CON. SWITCH --/j,-*^ 
 
 •-'0 
 
 LINE 
 
 .o 
 
 BUZZERj_ SW. , TALK 
 
 SECONDARY 
 
 tWWW-', 
 
 V 
 
 ilk. I 
 
 _j Small c 
 
 J J 0///C 
 
 - T I I II (transmit 
 
 {mANSMlm) 
 
 Fig. 3-30.— BUZZER, SERVICE. CIRCUITS. 
 
 SKCOXPAItV sr,>CI>I.\(i CIUCIIT TEI.EIMHINE. 
 
 .■s'. /'. D. T. knife switch marked ".S'/r" is ch)sed on side marked "talk." When 
 sound waves fall ni)on diaphragm of transmitter, an alternating; curriMit of 
 hijrli E. M. F. is induced in .secondary windin;; of induction coil. Starting; with 
 secondary of induction coil, to (1, to earth or one side of line (if metallic circuit 
 be used), throuiL'ii •' receivin;;-circuit-telephone " of distant instrument, return- 
 ing on other side of line, to L, tln'ough contact 3 of key mark»Hl "A"" (key 
 rai.sedt, to receiver, to C, to switch marke<l " iSir," through blade of this switch 
 to B. to .1, to other side of .secondary winding of induction cuil. 
 
 IMrCEIVINC n UCf IT TELKrnoNE. 
 
 ^'. r. D. T. knife swiuli mariced "'Sir" is closed on side marked "talk." An 
 alternating current of high E. SI. F. induced in the secondary wimling of 
 induction coil in distant instrunienl. reaches buzzi-r over outside lin««, to I.. 
 thence to contact 3 of key marked " A',*' to re«'i'iver. to T. to switch mark«Ml 
 "Sir", througii blade of this switch lo /{. to .1, through secondary winding of 
 induction coil to (7, to earth or line (if metallic circuit be u.sed). to distant 
 buzzer. 
 
 (97)
 
 32 
 
 Signal Corps Manual No, 3. — Chapter 3. 
 
 When an existing telegraph line is utilized, the switch marked "con sio" 
 should be thrown to the "O" position in order that the condenser " Con" will be 
 placed in the circuit. 
 
 Tlie service buzzer is sliown in accompanying figures 3-31 and 3-32, it being 
 sliown dismantled in figure 3-32 to facilitate preparation of requisitions for 
 renewal parts. 
 
 The instrument is contained in an aluminum case fitted with a lunged cover, 
 both of wliic-h are covered externally with a russet-colored, smooth-finish leather 
 which is neatly sewed and riveted in place. The overall outside dimensions of 
 the case are approximately 3J by 5i by 7* inches. The two units of Tungsten 
 type A battery are contained in a chamber located in the bottom and are 
 accessible without opening main cover, there being an additional small hinged 
 cover in one end of case which is fastened securely, when closed, by a sub- 
 stantial spring clip, and by a flap of leather. 
 
 Fig. 3-31.— BUZZER, SERVICE. 
 
 The instrument may be operated with both covers closed, which is highly 
 advantageous in inclement weather. To ac<'omplish this there is a suitable 
 opening for leading out the cords to receivci- and transmitter, and in main cover, 
 directly over the sending key, is a round aperture which is made moisture-proof 
 by means of a covering of extremely flexible pigskin. The sending key can be 
 i-eadlly operated through this flexible pigskin. 
 
 The .sending key, induction coil, conden.sers. plug .jack, transfer switch, 
 vibrator, and binding pctst.s'for transmitter and receiver cords ai*e mounted upon 
 a common base of hard rubber. Wiring to the component parts is routed in the 
 underside of this base, which is mounted in the front of the case above the bat- 
 tery chamber previously mentioned. In the r(>ar of the inslrument is a compart- 
 nient of leather for containing llie transniitler, receiver, and cord for connect- 
 ing them. At one end of this cliiiniber. neatly moinited on a liai'd rubber strip, is 
 a .socket wrench for adjusting the nuts which secure the transmitter and 
 i-eceiver terminals, also two .screw drivers — one large and one small — which are 
 so constructed that the shanks may be inserted in the end of socket wrench, 
 thereby using socket w rcnch ;is a IkiikIIc. 
 
 Invariably there is furnisiicd willi (his instrument a two-conductor cord, 
 approximat(!ly o feet long, one end of wliidi is e(|ui|iiied with a substantial plug 
 
 (08)
 
 Telephony — Camp Telephone and Buzzer. — Chapter 3. 
 
 33 
 
 similar lo (hose used in connection witli ii'loplione switchlxtanls. At otlier end 
 one of tli(? conductors is e((uipped with a Williams test clamp for connection to 
 lino, the other conductor ))einf; equipped with a Signal Corps type D jrround 
 lod. The Williams tesi clamp is si) conslructed that to attach to line, it is 
 merely necessary to compress the two principal parts, releasing them when 
 line has heen inserted in space provided. One side of this clamp is e<piipped 
 with an 11-point stud .securely threaded to test clamp. These points make 
 excellent contact on line, regardless of whether the line be insulated or not. 
 I5y tliis means a quick connection can be made to buzzer wire or field wire 
 which is insulated, and when the clamp is removed the abrasion to in.sulation 
 is negligible. There is an opening in the case of buzzer through which the 
 plug is imserted when coimection is desired, and when plug is .so inserted, it 
 makes a positive connection by means of a substantial jack mounted <in the 
 base as i)reviously indicated. 
 
 Fig. 3-32.— BUZZER, SERVICF. DISMANTLED. 
 
 Part 
 
 No. 
 
 Xliiiio. 
 
 Referenco 
 
 Ni. 
 
 1 ] Case, complete 
 
 2 Cover for ca.-se. complete 
 
 3 Door, battery, complete witti hinges 
 
 4 ' Case, leather, for transmitter ami receiver. 
 
 5 1 Ciirryini; st rap 
 
 6 i Maiii cord witli terminals 
 
 7 Ground rod, type D 
 
 8 I Plug 
 
 (Continued on next page.) 
 (00)
 
 34 
 
 Signal Corps Manual No. 3. — Chapter 3. 
 
 Parts list— Continued. 
 
 Plug, fiber cups for. . . 
 Connector, t j-pe A . . . 
 
 Transmitter 
 
 Transmitter, cap for. . 
 
 Receiver 
 
 Receiver, cap for 
 
 Head band, complete 
 Base. 
 
 Base, holding screws for 
 
 Induction coil, complete 
 
 Condensers (3 to a .set ) 
 
 Condensers, connect ing blocks for 
 
 Condensers, short-circuit switch, complete. . 
 
 Condensers, holding clip 
 
 Jack, plug, complete 
 
 Jack , spring for 
 
 Switch, transfer, complete 
 
 Vibrator, complete (11 pieces) 
 
 Viljrator screw, clamp 
 
 Vilirator screw, contact 
 
 Vil)rator tongue with platinum contact 
 
 Key, sending, complete 
 
 Key, lever for, without button 
 
 Key, supports and screws 
 
 Key, spring for 
 
 Key, adjusting screw for 
 
 Key, hard rubber button for ._ 
 
 Binding post, complete ." 
 
 Binding post, screws and washers for 
 
 Screw dri\er, large 
 
 Screw driver, small 
 
 Handle for screw drivers, and wrench 
 
 Battery, Tungsten, type A (2 imits to a set). 
 Battery spring and support 
 
 18 
 
 The case has an adjustable carrying strap, one end of which is equipped with 
 a snap connection, the other end being sewed to hinged fitting on case. Tlie 
 instrument, Inchiding carrying strap, type D ground rod, Williams test damp, 
 plug and H-foot cord, weighs approximately 5 pounds, and full directions ft)r 
 operation, together with a circuit dhigram, are attaclied to tlie inside of main 
 cover. 
 
 Figure 3-33 shows tlie circuits employed in sending and receiving Morse 
 signals by means of service buzzers. It will be noted tluit a single conductor is 
 used to connect the two instruments, and that the earth is used for other con- 
 ductor of tlie circuit. This is the customary manner <if connecting two or more 
 service l)uzzers in tlie field. 
 
 SENDING STATION = 
 
 Ground Rod 
 
 RECEIVING STATION 
 
 Fig. 3-33.— BUZZER. SERVICE, SENDING AND RECEIVING MORSE SIGNALS, CIRCUITS 
 
 EMPLOYED. 
 
 (100)
 
 ClI.M'TF.R 4. 
 
 CABLE AND CABLE SYSTEMS. 
 
 The cables provided Ity the Sijriial Corps are oC two fieneral classes, namely, 
 submarine and sultlerranean. The two general classes may each be dividcil into 
 two classes, depending: upon the insulation used — whether rubber coiniKUiiid 
 or paper. As the development of the.se cables has been alonK different lines, they 
 will be described under separate headings. 
 
 SUBMARINE CABLES. 
 
 The first successful submarine cables employed f?utta-percha as an insulating 
 medium. This compound is subject to rapid deterioration when exposed to air. 
 and for that reason such cable nmst be kept submersed at all times. 
 
 The general use of India rubber as an insulator in subterranean and aerial 
 power cable work led American manufacturers to the development of this com- 
 pound as an insulator for submarine cable, and many hundreds of miles of deep- 
 sea, rubber-insulation submarine cable have been successfully laid and operated 
 by the Signal Corps. 
 
 While it is frequently stated that rubber compounds used in deep-sea cable 
 work are not materially affected by exposure to air for a considerable period, 
 the Signal Corps has found it impracticable to store this class of cable without 
 submerging, although rubber is undoubtedly vastly superior to gutta-percha in 
 this respect. 
 
 The most serious problem in the design of rubber insulation cables for tele- 
 phone work is due to the mechanical characteristics of the compound. Since 
 the cable must be made up in twisted pairs in order to avoid trouble from 
 induction, a tensile strain will tend to cause the conductors of the twisted 
 pairs to press through the compound at points of crossing, lowering the insula- 
 tion and eventually interrupting conununication. This trouble is most marked 
 in the larger types. 
 
 The corrosive action of sulphur used in the rubber compound, on the copper 
 conductors is a troulile which is dilhcult to eradicate completely. Another dith- 
 culty which is connnon to both rubber and gutta-percha lies in the high capacity 
 which results from the use of either of these forms of dielectric. On short 
 lengths of cable this objection is not serious, but the fact tiiat 25 miles of 
 ordinary rubber-covered twisted pair is the limit of audible conversation nmst 
 frequently be taken into consideration in designing cable. 
 
 As a re.sult of many years experience in harlutr cable maintename the modi- 
 fied conniiercial types of cable indicated herein have been adopted. 
 
 While the use of rubber in this class of cables has been gen»'rally abandoned 
 in favor of paper, the Signal Corps has retained this insulation for cables not 
 exceeding six pairs in size. It is thought that in the smaller cables there is a 
 slight advantage in simplicity of repair of rubber, and no markt^l economy is 
 gained in the use of paper insulation. For cables from five pairs upward, thera 
 are many advantages- in the adoption of the paper insulation. 
 
 (101) 1
 
 2 Signal Corps Manual No. 3. — Chapter 4. 
 
 RUBBER INSULATION SUBMARINE CABLES. 
 
 The conductors of these cables invarial)ly consist of seven strands of annealed 
 copper wire, 28.5 or 20.1 mils diameter, tinned to prevent as far as practicable 
 the corrosive action of sulphur in the rubber. Each conductor is insulated as 
 follows : 
 
 First. With a coatinc of fine Para rubber to a uniform thickness of one sixty- 
 fourth of an inch. 
 
 Second. With a compound containing either 30 or 40 per cent of fine, unre- 
 covered Para rubber to a uniform diameter of thirteen sixty-fourths of an inch, 
 the compound being applied seamlessly. 
 
 Third. With a .SO per cent rubber compound, conforming to the requirements 
 of Signal Corps specification to a diameter of nine thirty-seconds of an inch. 
 The insulation is then covered with a layer of best cloth tape saturated with an 
 approved rubber compound, and put on with a double lap. 
 
 It has been claimed that one layer of rubber compound instead of three is 
 more satisfactory, consequently in future one layer only of either 40 per cent 
 or 30 per cent compound will be applied in the manufacture of some of these 
 cables. 
 
 In multiple conductor cables, two of the conductors are twisted together 
 and all conductors are grouped together in such a manner that the finished 
 core will be cylindrical. The core is then given two sufficient servings of best 
 India jute roving, which has been previously steeped in a strong solution of 
 cutch and dried. The jute serving is put on in reverse layers. 
 
 TYPE 50 
 
 ,^f^~\ 
 
 TV:£E 56 
 
 Fig. 4-1.— CABLE, SUBMARINE, RUBBER INSULATION. 
 
 The core of the cable is then armored by having a number of steel wires 
 wound spirally about it. The lay of the armor wire is left hand, the length 
 of such lay being equal to 10 times the diameter of the cable, measured over 
 the arnioi- wires. Where a double ai-nior is applied the outer has a right-hand 
 lay. The diameter of the armor wires varies from 144 mils for 1-conductor 
 cable to 220 mils for 12-con(luctor cable. They are invariably heavily gal- 
 vanized and re(iuinMl to meet certain tests in this respect. 
 
 The completed cable is then served with two layers of India jute yarn, one 
 being in reverse direction to that of tlu' oilier, the cal)le being run through 
 hot asphalt conii)ouM<i allcr jtiacing each <»(' the nhov(> layers of jute. To pre- 
 vent sticking, the com]ilclcd cable is then nni through jiowdercd chalk (whit- 
 ing) or other aj»prov«'d impali)ably ijowdercd rock. 
 
 The following table gives the i)rincii)al (•haracteristi<'S of the latest ai)i)roved 
 tyiK's of rul)b('r insulation cable uscmI by the Signal Corps lor .submarine con- 
 tiect ions (sec tig. 4-1 ). 
 
 (102)
 
 Cable and Cable Systems. — Chapter 4. 
 
 For list of all types ol' rui)lH'r insiilalinn cnhlcs iIimi 
 niariiio foiiiioftioiis, see chapter 8 of this Manual : 
 
 ia\(' licci) lb 
 
 fur sill)- 
 
 
 
 
 Conductor. 
 
 
 
 
 Per statute milf. 
 
 
 ^^.^ 
 
 Num- 
 ber 
 of con- 
 ductors. 
 
 Twfated 
 
 
 
 Diameter 
 over insu- 
 
 Armor, 
 diameter 
 
 Lay of 
 armor not 
 
 Capac- 
 
 Resist- 
 
 Length 
 on reel 
 unless 
 
 
 Diameter 
 
 pairs. 
 
 Number 
 
 of each 
 
 lation. 
 
 in mils. 
 
 more 
 than — 
 
 ity not 
 
 ance 
 
 otherwise 
 
 
 
 of strands 
 
 strand in 
 
 
 
 more 
 
 of cop- 
 
 specified. 
 
 
 
 
 
 mils. 
 
 
 
 
 than— 
 
 per. 
 
 
 
 
 
 
 
 Inch. 
 
 
 Inches. 
 
 M.F. 
 
 Ohnu. 
 
 F',t. 
 
 50 
 
 1 
 
 
 
 7 
 
 28.5 
 
 
 144 
 
 12 
 
 . 5 
 
 9.7 
 
 10, .y.() 
 
 51 
 
 2 
 
 1 
 
 7 
 
 28.5 
 
 
 144 
 
 12 
 
 . 5 
 
 9.7 
 
 10, .>^J 
 
 52 
 
 4 
 
 2 
 
 7 
 
 28.5 
 
 
 162 
 
 14 
 
 . 5 
 
 9.7 
 
 10, .'.DO 
 
 53 
 
 6 
 
 3 
 
 7 
 
 28.5 
 
 
 204 
 
 10 
 
 . 5 
 
 9.7 
 
 5, 2s(j 
 
 54 
 
 8 
 
 4 
 
 7 
 
 28.5 
 
 
 204 
 
 10 
 
 . 5 
 
 9.7 
 
 5,2S() 
 
 55' 
 
 10 
 
 5 
 
 7 
 
 28.5 
 
 4 
 
 229 
 
 18 
 
 . 5 
 
 9.7 
 
 2,040 
 
 50 
 
 12 
 
 6 
 
 " 
 
 28.5 
 
 i! 
 
 229 
 
 18 
 
 .5 
 
 9.7 
 
 2,640 
 
 Note.— Armor shall have a left-hand lay. 
 
 Kuhher insulation cahle may he furui-slied in douhle armor if installation 
 is requiretl iii unusually rocky localities. 
 
 PAPKK-lNSrL.VnO.V SlH.MAKl.NK CAIU.KS. 
 
 The necessity for an insulation which would he free from the ohjections 
 noted for ruhher and the more numerous ohjections to gutta-percha led to 
 the development of the paper-insulation cahle. In case of a puncture of the 
 sheath the paper core swells and dampness tends to work hack but a very 
 short distance. This cable is free from all of the objections cited for rubber 
 and gutta-percha. 
 
 The conductors are insulated with two wraps of dry manila paper of such 
 character and iu such a manner as to meet specified capacity and insulation 
 requirements. The insulating manila paper is plain in color for one con- 
 ductor of each pair and colored for the other. The core of the cahle is " laid 
 up" in twisted pairs, each pair having four twists per foot. These pairs are 
 " laid up " in successive layers, each successive layer being wound in reverse 
 direction to the precetling layer, making a complete turn in fntm IS t(» 36 
 inches. The whole core is served with a covering of heavy manila paper 
 and encased in a lead sheath, the thickness of which vari»'s with the size of 
 the cahle. Jute and armor are then applied in manner previously describe*.! 
 in this chapter. 
 
 The following table gives the ))rincipal cluiracteristics of the latest api)roved 
 types of paper-insulation cable used by the Signal Corps for sul)marine con- 
 nections. ( See fig. 4-2. ) 
 
 /■OuterJute 
 
 TYPES 320 TO 327 INC 
 
 Fig. 4-2.— CABLE, SUBMARINE, PAPER INSULATION 
 
 (103)
 
 4 Signal Corps Manual No. 3. — Chapter 4. 
 
 For list of all types of paper-iusiilatinn cables that have been used for 
 submarine connections, see chapter 8 of this manual. 
 
 Paper insulation, lead covered and armored cable. 
 
 Type 
 No. 
 
 Number 
 of con- 
 ductors. 
 
 Size of 
 conduc- 
 tor, B. 
 andS. 
 gauge. 
 
 Size of 
 
 armor, 
 
 B. W. G. 
 
 gauge. 
 
 Per statute mile. 
 
 Capacity. 
 
 Eesistance 
 of copper. 
 
 Weight. 
 
 320 
 321 
 322 
 324 
 325 
 326 
 327 
 
 10 
 20 
 30 
 40 
 50 
 60 
 100 
 
 19 
 19 
 19 
 19 
 19 
 19 
 19 
 
 6 
 4 
 4 
 4 
 4 
 4 
 4 
 
 Microfarads. 
 0.10 
 .10 
 .10 
 .10 
 .10 
 .10 
 .10 
 
 Ohms. 
 45 
 45 
 45 
 45 
 45 
 45 
 45 
 
 Pounds. 
 20,400 
 27,900 
 29,880 
 35,805 
 39,115 
 47,355 
 57, 750 
 
 No*E. — All in twisted pair, double wrap, dry paper, 
 
 Reserve reels of paper-insulation caltle are provided in all coast-defense 
 commands having important submarine cable installations. Ordinarily all sub- 
 marine cables are laid and repaired by the personnel of one of the Signal Corps 
 cable ships. In the event of the cable ship not being available, the reserve 
 cable can be laid to replace one that becomes unserviceable, by means of a tug 
 and lighter, one or both of which can usually be obtained in the immediate 
 vicinity. 
 
 The latter action is taken only when the exigencies of the service require 
 communication, which has been interrupted, to be established before the cable 
 ship can be sent to make the necessary repairs. 
 
 Subterranean Cables. 
 
 The manufacture of paper-insulation cable has been perfected to such a degree 
 that the cost of this class of cable is far below that of the rubber-insulation 
 type. Subterranean cable usually supplied for communication purposes is paper 
 insulation, lead sheathed but not armored, It being understood that suitable 
 conduits for the installation will be provided. Where it is impracticable to 
 furnisli a conduit, lead-covered and armored cable is furnished (regardless of 
 insulation), and the cable is laid in a trench a])proximately 2 feet deep and 
 then covered with earth. The manufacture of rubber-insulation subterranean 
 cable and paper-insulation subterranean cable are so similar to t-ables with 
 same insulation for submarine work previously described in this chapter that 
 detailed description would be superfluous. Suffice it to say that invariably 
 cable for submarine work Is supplied with an armor regardless of nature of 
 insidallon and in addition a lead sheath if the insulation be paper, while cable 
 fi>r subterranean use is armored only when it is intended that it shall be 
 ti<'nclied or placed in an exposed location. 
 
 I)(iul)le lead-covered cable may be supi)lie(l Un- iiislnllalioii in inarslics or 
 .similar locations where mechanical damage is uiilik(>ly. 
 
 The following tables indicate the latest aiiproved tyiics of sublcrrancan cables 
 used for lines of communication. 
 
 For comiilete lists <if cables that have been used lor subtci-rancan work, see 
 chapter 8 of this manual, 
 
 (104)
 
 Cable and Cable Systems. — Chapter 4. 
 
 Ruhlx r iihsuliitioii !siil>tcn(tit>(in ctthlc 
 (See fig. 4-.3.] 
 
 Tvpe 
 No. 
 
 Nnmtx?r 
 of con- 
 ductors. 
 
 Number 
 
 and 
 
 size of 
 
 strands 
 
 B. and S. 
 
 gauge. 
 
 Diameter 
 over insu- 
 lation 
 (rubber). 
 
 .\rmor. 
 
 15. \v. <;. 
 
 gauge. 
 
 Weiglit 
 per mile. 
 
 Length 
 on reel. 
 
 213 
 214 
 
 215 
 216 
 217 
 218 
 251 
 
 2 
 6 
 
 12 
 24 
 12 
 24 
 2 
 
 7-24 
 7-24 
 
 7-24 
 7-24 
 7-24 
 7-24 
 1-18 
 
 Inch. 
 5/32 
 5/32 
 
 5/32 
 5/32 
 5/32 
 5/32 
 4/32 
 
 
 Pounds. 
 3,000 
 
 mu. 
 
 , ! 
 
 Feel. 
 1,000 
 1,000 
 1,000 
 1,000 
 1,000 
 
 
 9,200 
 
 11,100 
 14,785 
 18,800 
 26,900 
 
 
 
 14 
 9 
 
 (') 
 
 
 > Steel tape. 
 Note. — .\llin twisted pair, with J-inch lead sheath, except the type 251, which has a 1/32-iiich lead slieatb. 
 
 Armcr ':c'r':{fel f/:rv. :n30In ihJrk 
 
 TrPE- 251 
 
 TYPE 217 
 Fig. 4-3.— CABLE, SUBTERRANEAN, RUBBER INSULATION. 
 
 I'aprr insula fioii. had-corcn d lalilc. 
 [See fig. 4-4.] 
 
 Tviw 
 No. 
 
 401 
 402 
 403 
 404 
 405 
 406 
 407 
 408 
 409 
 
 Designation. 
 
 Conductor, 
 
 diameter of 
 
 each strand 
 
 in mils. 
 
 Thickness 
 of lead 
 sheath. 
 
 -Vpproxi- 
 raate out- 
 side diam- 
 eter. 
 
 10-pair. . 
 15-pair. . 
 20-pair. . 
 25-pair. . 
 30-pair. . 
 40-pair- . 
 50-pair . . 
 75-pair. . 
 lOO-pair. 
 
 3/32 
 3/32 
 3/32 
 3/32 
 3/32 
 7/64 
 7/64 
 7/64 
 7/64 
 
 Inches. 
 0.722 
 .797 
 .872 
 .922 
 .982 
 1.113 
 1.208 
 1.44.3 
 1.638 
 
 Weight per 
 
 statute 
 
 mile. 
 
 Pounds. 
 5,370 
 6,193 
 7,054 
 7,693 
 8,416 
 11,083 
 12,445 
 15, 829 
 18,860 
 
 Weight per 
 
 1.000 feet of 
 
 cable and 
 
 reel. 
 
 Pou 
 
 nds. 
 1,1S6 
 1.368 
 l,.i58 
 1,700 
 1,860 
 2,448 
 2,750 
 3,497 
 3,967 
 
 Note. — A] in twisted pair, double wrap, dry paper. 
 
 (105)
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 Paper insulation, double lead covered cable. 
 [See flg. 4-4.] 
 
 Type 
 No. 
 
 Number 
 of con- 
 ductors. 
 
 Size, B. 
 
 and S. 
 gauge. 
 
 Per statute mile. 
 
 Capacity. 
 
 Resistance 
 of copper. 
 
 Weight. 
 
 312 
 313 
 314 
 315 
 316 
 317 
 
 10 
 20 
 30 
 50 
 60 
 100 
 
 19 
 19 
 19 
 19 
 19 
 19 
 
 Microfarads. 
 0.10 
 .10 
 .10 
 .10 
 .10 
 .10 
 
 Ohms. 
 45 
 45 
 45 
 45 
 45 
 45 
 
 Pounds, 
 15,100 
 18,400 
 21,100 
 23,000 
 24, 400 
 26,400 
 
 /Ltad 
 
 TYPES 320 TO-327 INC. 
 
 Fig. 4-4.— CABLE, SUBTERRANEAN, PAPER INSULATION. 
 
 It will he notetl that paper insulatimi cable, lead covered and armored, may 
 he used either for .suhni:irine w()rk or .siihterranean w(»rk wliere it is intended 
 that the cahle he trenched. 
 
 I'OWKK CAULt. 
 
 (,'ai)lesu.se(l for transnuttinji jiower such as are necessary in underjiround lijiiit- 
 ins and power systems, the charfring and dischurjiing of storage hatteries or any 
 use where Uie strength of current employed is large as comiiiircd with (hat of 
 a lelejdione or telegra]ih circuit, are termed jiower cahle.s. 
 
 Power cahles employing pajter insulation are (piile extensively used in the 
 connnercial world, hut it is helieved that all things considered (he ruhher insu- 
 lation cahle is more .satisfactory for this ])urp()se, mid lor (hat icasoii ;dl power 
 cahles furnished hy the Signal Corps are of (he Inlter class. 
 
 Tlie rule which pre.scrihes armor for siililei-raueiin coniiMuiiicalion cahles 
 laid in trench aiijtlies also for the installation of ixtwer cahles. 
 
 The following tahle indicates jutwcM* cahles usually carried in s((M-k hy (he 
 Signal CV»rps. For complete list of power cahle that can he supi)lied, .^^ee chapter 
 S. It is imi)()rtant to note that these power cahles may he furnished in a 
 number of sizes and that ea<h size may he single or duplex, also that any 
 
 (106)
 
 Cable and Cable Systems. — Chapter 4. 7 
 
 of the cables can be supplied with either an outer braid, lead shealh, or lead 
 sheath and armor. 
 
 Rubber insula t tan power cable. 
 [See Fii;. 4-.V) 
 
 Type numbers. 
 
 Area 
 circu- 
 lar 
 mils. 
 
 Num- 
 ber of 
 strands 
 per con- 
 ductor. 
 
 Diam- 
 eter of 
 single 
 wires. 
 
 Resist- 
 ance of 
 
 con- 
 ductor 
 per 
 1,000 
 feet, 
 68° ]•'. 
 
 
 Length on reel. 
 
 Diam- 
 eter of 
 armor 
 wires. 
 
 Sin- 
 gle 
 L. C. 
 
 Du- 
 
 Du- 
 plex 
 
 L. r. 
 
 and 
 ar- 
 mor- 
 ed. 
 
 Thick- 
 ness of 
 wall of 
 nibtjer 
 insula- 
 tion. 
 
 Single 
 braided 
 
 and 
 single 
 
 L. C. 
 
 Duplex Thick- 
 L. C. ness of 
 and lead, 
 duplex ' 
 
 ar- 
 mored. 
 
 622 
 623 
 624 
 625 
 626 
 627 
 
 642 
 643 
 644 
 645 
 646 
 647 
 
 662 
 663 
 664 
 665 
 666 
 667 
 
 6. .530 
 10, 3S0 
 16,510 
 26, 250 
 33.100 
 41,740 
 
 
 Mils. 
 80.81 
 102.0 
 48.6 
 61.2 
 68.8 
 77.2 
 
 1.586 
 .9972 
 .6271 
 .3944 
 .3128 
 .2480 
 
 I-nch. 
 
 31 
 
 Feet. 
 2,000 
 1,500 
 1.500 
 l,oOO 
 1,500 
 1,500 
 
 Feet. Inch. 
 1.000 
 
 1.000 i 
 1,000 i i 
 1,000 i i 
 1.000 J 
 1,000 i 
 
 1 
 
 M\h. 
 114 
 114 
 114 
 144 
 144 
 162 
 
 TYPE:S 641 TO 654 
 
 TYPES 601 TO 614 
 
 Fig. 4-5.— CABLE, POWER. 
 
 Cable Reels. 
 
 In order to niaiiiTain a complete history of tlie various cables, each reel of 
 Sijrnal Corps cable bears a brass tag marked with the letters " S. C." and 
 a .serial number, this tag being attached to the reel when the cable there«in 
 is accepted by the Signal Corps inspector. The tag is for the juirpose of 
 identifying the reel and also the cable ami will be removed only when the 
 reel is returned directly to the manufacturer, which shipment should not be 
 made except under advice from the Chief Signal Officer of the Army. 
 
 The Chief Signal Officer of the Army will assign reel numbers at the time 
 order for cable is placed. The Department Signal Officer, Eastern Department, 
 will have charge of and issue reel tags. When cable is manufactureil in 
 !>nother dei)artnient and inspection is under the direction of the Department 
 Signal Oflicer of that department, application will l)e made to the r>epartuient 
 Signal Othcer, Eastern Department, who will furnish the necessary tags for 
 attachment to reels. Upon the placing of cable order, the Department Signal 
 Officer, Eastern Department, and the department signal offi<'er under wIio.m' 
 direction inspection is to be made will be furnished with a copy. The latter 
 
 46581°— 17 8 (107)
 
 8 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 will cause the inspector to see that the reel number and marking for the 
 shipment as shown in the order is followed, that the manufacturer's name and 
 reel number appear on the reel in some permanent form (manufacturer's 
 name and number will be omitted when the reel becomes the property of the 
 Signal Corps by terms of the order), and will advise the Chief Signal Othcer 
 of the Army of the manufacturer's reel numbers corresponding with Signal 
 Corps reel numbers. If cable is transferred from one reel to another, report 
 Avill be made at once to the Chief Signal Officer of the Army through the 
 Department Signal Officer, showing the amount and type of cable, the reel 
 from which removed, and the reel on which wound. Cable should not be 
 transferred to a reel known not to be the property of the Signal Corps if 
 it is possible to avoid it. It is not desired that full lengths of cable held in 
 stock be transferred for the purpose of freeing manufacturer's reels, but other 
 conditions being equal, cable on reels the property of manufacturers should be 
 used first. 
 
 
 
 ^^^^^^^^^■^'flp^^^^^H| 
 
 Fig. 4-6.— REEL, CABLE, WITH LAGGING. 
 
 In the installation of cal)le systems it is customary to collect a quantity of 
 empty reels before, returning them to one of the general supply depots if 
 property of the Signal Corps, or the manufacturer if property of the contractor. 
 Construction parties sIkjuUI invariably return lagging to reel as soon as prac- 
 ticable inasnuu'h as the lagging is considered a part of the reel. In former 
 years' the lagging of cable i-eels was given away or u.s(>d as kindling for fire, 
 but the material advance in the cost of lumber has made such action a waste 
 that is prohii)ited. Manufacturers require that the unbroken lagging be re- 
 turned with reels. 
 
 Installation of .(Baulks. 
 
 Submarine cal)k's an- usually laid by the j)ersoniiel of one of the cable 
 ships. The cable ships Un- laying and repairing harbor lire-control cables 
 are each equipped with an enormous reel permanently installed in a vertical 
 position on forward main deck. The revolving of this reel in either direction is 
 accomplished by means of electric motors under control of an operator who 
 is stationetl near reel. The cable to be laid is wound on reel described above, 
 
 (108)
 
 Cable and Cable Systems. — Chapter 4. 9 
 
 thereby releasing reels upon wliicli caliU' was sliiiipi'd. As the ship's reel 
 will hold many miles of cable, it is probable that the amount to be laid may 
 comprise that contained on several shiitpiny reels. Before proceeding with the 
 actual laying it will be necessary, of course, to splice the cable from the 
 several shipping reels. The sliore ends of the calile are landed by employ- 
 ing ship's launch and small boats. When one end has been landed and securely 
 fastened the ship proceeds over the route selected, the cable paying out over 
 a large sheave at a speed reguhited by the reel operator. Continuous tests 
 during the laying of the cal)le are made with delicate testing ap|taratus in 
 order that a fault may be detected as soon as possible. When the lauding of 
 cable is completed, the ends are securely anchored by means of chains. It is 
 more desirable that a submarine cable separate than to have the ends pulled 
 out to sea. After a cable is laid, a report, showing its type, length, number 
 of splices, insulation resistance, ohmic resistance, electnjstatic capacity, and 
 other data is submitted by the connnanding otlicer of cable ship to the Chief 
 Signal Odicer of the Army and copies to others who are authorized to receive 
 such reports. 
 
 In harbors, to avoid as much as possible, interruptions, due to rupture of 
 cabies by ship anchors, not only have routes been selected which will avoid 
 crossing " much used '' anchorages, but a list of forbidden anchorages cov- 
 ering paths of all submarine cables installed by the Signal Corps has been 
 prepared and furnished the Hydrographio Ofhce of the Navy Department, with 
 request that it be embodied in " Notice to Mariners " issued by that office. It 
 is believed that this action will obviate to a great degree interruptions which 
 have been occasioned by vessels anchoring in the vicinity of cables. 
 
 Signs reading "Cable crossing — don't anchor" have been installed at suitable 
 points near cable landings, and while in some instances such action has been 
 effective, in a great many instances the signs have apparently been ignored. 
 
 Complete list of cable gear and supplies may be found in chapter 8 of this 
 manual. 
 
 Aekial Cahle. 
 
 Soin<>linu's cables used in post telephone systems are installed aerially, 
 existing ixtle lines being employed as much as possible. In the installaticm of 
 aerial cable a messenger consisting of stranded galvanized-steel cable is 
 stretched tightly and fastened securely at each pole, care having been pre- 
 viously taken to guy the poles substantially where necessary. The cable is 
 then drawn along messenger, being suspended from it by hangers, one tyi)e 
 of which is made fast to cable, another type being clamped to messenger. 
 
 UNUEUUKorM) C VIU.K. 
 
 It is desirable to jilace cables under ground wherever practicable. This 
 avoids the pole lines and the necessity for ruiuiing pole lines about the post 
 in conspicuous locations, secures the cable from many sources of injury com- 
 mon to aerial lines, and makes the system reliable in operation and easy to 
 maintain. Underground construction will, in general. I)e more exi)ensive 
 than aerial, and this consideration will usually determine the form of con- 
 struction to be followeil. The first step is to decide on the general layout of 
 the system. The procedure should, in general, be the same as outlined for the 
 aerial plant. In selecting the routes, attention should be given to the contour 
 of the post; location of material obstacles to cable runs; buildings, existing 
 and projected, and probable extensions of the system in the future. The runs 
 
 (100)
 
 10 Signal Corps Manual No. 3. — Chapter 4. 
 
 between manholes .should be without curves or bends. A diagram of pair dis- 
 tribution similar to figure 4-7 should be made, after which the lengths of the 
 various sizes of cable can be determined. 
 
 Two general methods of placing cable under ground may be followed — trench- 
 ing and conduit. The first costs less to install and does not require skilled 
 labor, but has the disadvantage that the cable is not readily accessible for 
 repair and once installed can not easily be recovered. Trenched cable is also 
 more liable to mechanical injury after laying. It may be stated as general 
 that trenching will be confined to lateral runs of type 251 cable. All paper- 
 insulation cable, as far as practicable, will be placed in conduit. 
 
 DOUBLE QUARTERS OmCERS' QUARTERS OFFICERS' QUARTERS 
 
 CQr^JX) O Qo.^ QunrJO Q Q O Q Q 
 
 1^ ' \ ^ -T T i Oik:idcdistj-ii>utjnqpoi'fs 
 
 1 3r armored cable. tylK 251 trenched iiopr-K" ADM IN. B UILDING I ^ Fused jgrm ma I-.1. ^1 1 
 
 '^_ __ Al1.^£I'<^ r~%PS<L'j%e^ _ ^^S-^T7nr 
 
 ~ ~ Type4Oi.l0poir.J~conduiL 20 paiF. type,A03~^i^ ^Type.'iOI~o'p7^JfJriaT " "'^^ 
 
 P05C teUnitc/>bai\ 
 
 I' 
 
 I ill 
 
 4 lO pair type 40I _J|1 '2.!^—^R''-i2L— 
 
 " '•ji^FuSoJt^-Srpdi. -pr--jnr^_^^^^^^^/- lpoirJypeM [m,or,riu,t 
 
 
 NON-COM. OFF. QRTRS. "Si . . _ ^IFC.Z;.-.... , 
 
 NON-COM. OFF. QRTRS. "^ 
 
 k| STORL ^ 
 
 I 
 
 ^OUSE.S 
 
 SIS 
 
 5;s 
 
 □ □ I=D — 
 
 PUMP HOUSE F.C.SWBD.ROOM HOSPITAL FROMjCORAU 
 
 Fig. 4-7.— CABLE SYSTEM, DIAGRAMMATIC. 
 
 Tkenching Cablk. 
 
 The route being staked out, the trench should be excavated of sullicient width 
 ai'id not less than 18 inches in depth if practicable. Care should be taken that 
 the bottom of the trench and the first earth used for filling in are entirely free 
 from stones, sticks, or other material which will injure the cable shealli under 
 pre.ssure. The cal)le may be pulled into the completed trencii from the reel, 
 held on cable jacks. lu pulling into trench, avoid drawing cable over sharp 
 jirojections which would .score the shcalli. ^'hc same precautions should be 
 employed in sealing ends, splicing, and pot-heading as for aerial cable. After 
 the cable is laid and spliced the trciicli may be filled. The route of trench 
 with splices located sliould Ix' recorded on scale map. 
 
 ro.NDurr. 
 
 Ill all coiidiiil cniistruclidii llic roiJowing geiieral outline will apply: 
 The top of the coiHlnit line slionid never he less than IS inelu>s below the 
 surface. In many places this depth will be exceeded in order to maintain the 
 grade of the duct line. The distance between manholes should be as great as 
 local conditions and the length of the cable tiiat can be pulled into a duct 
 will j»ermit. Where fibei" or pump log conduit are used this distance should 
 not exceed 4(M) feet; for clay conduit 8.")() is considered the niaxinuun. As 
 cable is usually furiiislied in lengths of 1,(MM» feet, the spacing sliouhl be such 
 as to cut this length without wa.ste or accunndation of short pieces. 
 
 In general, it is desirable to run conduit or trench in rear of buildings and 
 (piarters to avoid cultiiig up tuif or lawns unnecessarily. The location of the 
 main line slionhl he such as to alToi-il Ihe most e<'onomical and convenient dis- 
 
 (110)
 
 Cable and Cable Systems. — Chapter 4. 
 
 11 
 
 trilMiti(Hi to stations. All cxcaviitioiis, csiM-cially on luadsvays, should he 
 ^iianUMl outside ol! w«»rking liours by suitable barricade and lanterns to prevent 
 injury to tralTK-. Avoid openin;; lont; .stretrlics of trench in which the cable 
 or c<»nduit can not be laid without delay. In many cases a plow nuiy be use<l 
 to good advantage tct remove the top layer of earth. Conduit will not be laid 
 in concrete unless four or more ducts are used. Conduit should be laiil in 
 straight line, and at same grade between maidioles if practicable. All changes in 
 direction should be made at a nuinliole <ir handhole. The bottom of the trench 
 should be smooth and firmly tamped before laying i-onduit. All work in con- 
 nection with conduit constructi<in should be accomplished un<ler the suiM»rvisi«m 
 of a thor(»ughly competent foreman. 
 
 The types of conduit used are bituminized liber, pump log, and vitrified clay. 
 For most of the Signal Corjis work the fiber conduit will be useil on ac<-onnt 
 of ea.se of installation and small tirst co.st of material. 
 
 The vitrified-clay conduit is suitable for conditions riNpiiring unusual strength 
 and rigidity. The plans shown herein are for fiber <<>ndnit in all ca.se.s. Where 
 this type is not available use may be made of either of the other types. 
 
 The standard fiber conduit is made in 5-foot lengths. 3-incli inside diameter 
 and three-eighths inch wall, weighing 2 pounds per foot. The lengths of con- 
 duit are made with male and female slip joints as shown in figure 4-8. When 
 
 Fig. 4-8.— CABLE SYSTEM. CONDUIT ENDS. 
 
 laying the conduit the end of each .section should be dipped into a water- 
 proofing liquid before jointing. Care should be taken t(» close the joint com- 
 pletely and to avoid placing st<mes or other material next the conduit in fillir»g. 
 The work of laying may be begun at a manhole or at any i»art of the trench. 
 Where the conduit work is disctintlimetl temporarily for any cause the ex- 
 posed duct eiuls should be plugged and coveri'd with a tari>aulin until work is 
 resumed. Where short lengths are niiuired the standard i)ii'ces may be cut 
 with a handsaw, using water to jirevent sticking of the saw. Care should be 
 tised in handling the «"onduit to avoid breaking the emls. The liber conduit is 
 made up in the iisiinl I'lhiiws. fi-f^;. :ind bends. 
 
 MAMKlI.KS. 
 
 To provide for acce.ss to conduit for pulling, splicing. in.sp«H'tion. and repnir 
 »)f cables, manholes are placed as needed. The usual form is shown in figure 
 4-9. The dimensii>ns of this figure may l)e varitnl to suit s|HH'ial condition.s. A 
 large number of fornuilae are in use for mixing concrete. The proj>ortions for 
 stone, sand, an<l cement varv with th«> size and character of the stone, the 
 
 (111)
 
 12 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 quality of the cement, and the purpose for which the con(^rete is to be used. A 
 good general formula is 1 part cement, 3 parts sand, and 6 parts stone. For 
 gravel, 1-2J-5 will be better. In making estimates it should be borne in mind 
 that the volumes of cement, gravel, sand, and stone taken separately will be 
 
 PLAN 
 
 Grouncf /me 
 
 
 SECTION 
 
 Fig. 4 9.— CABLE SYSTEM, MANHOLE. 
 
 groat<'r tlian tlic voiiinir of Die linislKMl concrete, and aHowance must l)e made 
 accordingly. Thus, for 1 cuhic yard of concrete by the fornuila \-'A-C>, there 
 will be nece.s.sary 1.1 barrels of cement, 0.4G cubic yard sand, and 0.9.'? cubic 
 yard st(»ne. One barrel of cement coiilaiiis four l)ags. Thi' formula is for parts 
 
 (112)
 
 Cable and Cable Systems. — Chapter 4. 
 
 13 
 
 ^ i»k' ^ 
 
 jai' 
 
 \ \ 
 
 \ I I 
 
 / ! '.----■•- lt----l:----n H vi ■ \ 
 
 y/c-%H.".-;4--*-----v-^li^-=---i^----v.ii-------i!------:^Xr^^^ 
 
 ''.-.-.-..-...-.■^4f^-.-.-.-k.-i^^.-.^yA^ I ~SN^Or------i^vi------------iK"-- 
 
 SECTION OF MANHOLt 
 Fig. 4-10.— CABLE SYSTEM, MANHOLE WITH CONCRETE TOP. 
 (113)
 
 14 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 by volume. The cement should be only the best grade Portland, the sand free 
 from loam or similar foreign matter, the stone hard and sharp, screened, and 
 not larger than will pass through a li-inch ring. The cement should be stored 
 only in a perfectly dry place. The materials should be thoroughly mixed before 
 adding water. Only such quantities should be mixed as can be placed without 
 a delay of more than 45 minutes. Water should be added very gradually 
 and thoroughly mixed with the materials as applied. The materials should 
 be accurately measured and not estimated. Mixing should be done on a board, 
 never on the ground. The excavation for the manhole being completed, the 
 bottom shall first be laid, extendding under the manhole walls. The concrete 
 shall be tamped in place and the surfaces smoothed off. 
 
 CONCRETE MANHOLE FORM 
 
 PLAN or FORM ASSEMBLCO 
 
 BRACt RODS B « C . 
 DRACe ROD A 
 
 
 Fig. 4-11.— CABLE SYSTEM, MANHOLE, REMOVABLE FORMS. 
 
 The form for the walls should be made of good dres.sed lumber, substantially 
 put together to withstand the pr(>ssuro of the concrete. The forms should bo so 
 built as to be easily removed for iise elsewhere. After forms are set and properly 
 braced the concrete should be placed to form a wall of the required thickness. 
 In some locations no outside form will be required, the earth wall serving this 
 end. The concrete should be deposiled in layers not more than G inches thick 
 and rammed in place until the surface becomes slightly fluid. The manhole 
 Khould be completed at one operation. A surface for the cover is made of cement 
 
 (IH)
 
 Cable and Cable Systems. — Chapter 4. 
 
 15 
 
 and tlio cover placed Ijefore tlie cenieiit lias set. In liiiure I t) liie cover is sliowri 
 (j inches below the surface, to allow for resoddiiit;. Where this is not required 
 the depth of the duct line below the surface may be reduced to place cover Hush 
 with ground line. In many ca.ses where it is necessary to provide access to duct 
 for distribution, inspection, etc., a much smaller manhole, usually terme<l 
 " handhole," will be sufficient. This should follow the general outline of figure 
 4-9, with an in: ide diameter of V2 by 15 and 12 inches deep, walls not over 
 inches thick. In many cases where the handhole is used to end a lateral to a 
 building the foundation may form one side of the handhole. The method of 
 construction is the same as for manholes. It is desirable t(j have (Mily one size 
 for all manholes and for all handholes, so that one set of forms will do for each 
 type, ^^'here concrete can not be useil, recourse may be had to brick or, in 
 emergency, creosoted plank not less than 2 inches thick. In some instances it is 
 advisable to furnish a cover equipped with a throat in order that entrance to 
 manhole will be liush with earth's surface, and in other instances a more expen- 
 sive construction such as is shown in figure 4-10 may be desired. The latter has 
 a cast-iron cover of somewhat dilTerent design adapted t(j withstand heavy traf- 
 fic. The dimensions of manhole given in this figure are not to be taken as stand- 
 ard. The type to be adopted depends on the number of ducts, local contours, 
 location, etc. In figure 4-11 is shown a set of removable forms for constructing 
 concrete manholes of this character. Where a number are to be constructed of 
 one size it will be found desirable to use this or a similar set of forms. These 
 should be made by local labor and of serviceable lumber. 
 
 MAN HOLE I 
 
 Fig. 4-12.— CABLE SYSTEM, DISTRIBUTION. 
 
 The method to be used in branching from a main-line conduit to a building 
 or group of buildings retiuires careful thought. Where the lateral is (»f sulhcient 
 length and the number of pairs requires a paper-insulation cable, a branch line 
 of duct with a handhole, as shown in figure 4-12, should be used. The handhole 
 is located at the wall of the central structure of the group, and the cable ends 
 in a can terminal, as shown. From the can terminal single-pair cables are 
 brought down to the handholes and are then run to each of the buihlings. being 
 trenched only after leaving the handhole. The height of the can terminal above 
 the ground is not fixed, but usually should be about ii fivt. In some cases the 
 terminals may be placed in basements, umler porches, inside storehouses, etc., 
 where the installation can be simplified. Connection from unilerground to 
 aerial cable may be made as shown in figure 4-13. 
 
 (115)
 
 16 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 
 ft^jl<.T|l';\>^ .-.Ml>->=il"...<!>^, 1,11, _ 
 
 o 
 
 z 
 
 zo 
 
 8^ 
 
 
 (110)
 
 Cable and Cable Systems. — Chapter 4. 
 
 PULLIN« CABLE IN CONDUITS. 
 
 17 
 
 L'uder no circuiiistaiHvs .should a cal)!!- .splice he ihiIIlmI in cundiiil. 
 
 Tlio conduit system hcin^' (■(►nipjctcd, |>r.t'iiaiation (or itullinji; in cajjle is made 
 by tin-cadinj: a rop*' tlu'ou^'li the »hi<ts. Tins may he acconii)iislH'd l)y tir.st pusli- 
 ing tlirougli duct rods of sections 3 or 4 feet iu length, with coupling devices 
 on each end, or u steel wire, known as u " tish wire" or "snake." (U.se may 
 be made of wooden strips, approximately i by 1 inch, cro.ss .section, notched at 
 the ends and spliced together with iron wire or by means of taping, the two 
 ends to be taped .separately and again wrai)ping the ends with tape, after the 
 two have b«'en placi-d together.) 
 
 The pulling-in roi>e is now attached to one end of the length of win* or rods 
 in the duct and pulled in. The cable reel is pla<«'d near manhole on jacks, as 
 shown in figure 4-14. 
 
 One or more men tend the reel and see that the cable feeds off freely. A man 
 In the manhole directs the cable into the duct and prevents injury to .sheath 
 from pulling across sharp corners. The pulling-in rope may be attached to cable 
 by a manufactured device shown at bottom of figure 4-l."5, or by an improvi.setl 
 one shown at top of same figure, which is made as follows : 
 
 Fig. 4-14. -CABLE PULLING. POSITION OF REEL. 
 
 Place n block of wood about H iiulies wide against tlie end of the cable; cut 
 G-foot 'engths of number 10 or 12 B. \V. G. steel wire; take two, thrtn*, or four 
 of these wires, depending on the severity of the pull, and bunch them together, 
 bend them in the middle on the block of wood, then wrap the two halves 
 spirally around the cable sheath in opposite directions, twisting the ends se- 
 curely together. When the pull of the rope comes on these wires, they biutl 
 harder on each other, on the lead, the insulation, and tlie conductors, as the 
 pull grows luirder. The seal on the lead of the cable is not broken, and n<i 
 water can come in contact with the insulation. 
 
 In pulling in paper-insulation cable of large size where tlie strain is unusually 
 great, it is advisable to make pulling roi)e fast to all conductors, as well as 
 sheath, in manner just described. This method is objiMtionable, liowever. es- 
 pecially if tliere be nuid or water in ducts, and is only resorted to iiy the Signal 
 Corps when there is tlanger of stretching lead sheath of cable to a dangerous 
 degree. 
 
 (117)
 
 18 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 Manila rope is usod for drawini:: cable tlioii^ili stoel rope may ho used. The 
 ends of the rope should be fitted with an eye around a steel thimble fastened 
 to a short length of chain with a swivel. The swivel may have a pair of 
 sister hooks, all as shown in figure 4-15. 
 
 Fig. 4-15.— CABLE GRIPS, IMPROVISED AND MANUFACTURED. 
 
 If the cable is small and run short, it may be pulled in by hand. For heavy 
 cables, winches, windlass, or horsepower may be used. The rope should be 
 led from the duct to surface over pulleys when the depth of the manhole makes 
 a direct pull inadvisable. Two pulleys on shafts which can be inserted in 
 any of a number of holes in two channels are used for this purpose, the lower 
 pulley being placed opposite the duct and the upper at a height sufficient to 
 carry the rope out of the manhole. Enough slack cable should be left in each 
 manhole for splicing and placing the cables along the sides, leaving the center 
 clear. After drawing in, examine all ends carefully to see that the seal is in- 
 tact. Two or even three cables of the sizes commonly used in Signal Corps work 
 may be pulled into one duct if drawn together. I'uUing in a second cable wilh 
 one already installed should he avoided if practicable. 
 
 HORIZONTAL SECTION Of MANHOU ^ „„ _^, 
 
 ANO PLAN OF CA8Lt3 '^^ 3u^^ *'^° BRACHtT 
 
 Fig. 4-16.— CABLE RACKING IN MANHOLES. 
 
 When distance b»'tw<M'n manholes is not over 200 feet cable may be pulled 
 through one manhole and on to next, provided the pull is in a continuous 
 straight line. The advisability of doing this is strictly u matter of judgment 
 on the r>art of person in charge of cable pulling and .slunild be regulated by the 
 amount of extra strain on cable <'aused by such action. When a cable is 
 pulled tlirough one manhole and on to the next, slack should be i)ulled back in 
 
 (118)
 
 Cable and Cable Systems. — Chapter 4. 1.9 
 
 tlie intermediate nianholc in order tiial ^■n\>h' may lie racJicd on .sides, thereby 
 i<eei)in}; center of ail manlioles clear. 
 
 A zinc tag on which is stamped the designation number is attached to each 
 cable in each manhole by means of galvanized-iron wire. In manholes where 
 cable is to be spliced, the tag described above should be placed on each .of the 
 two ends to be spliced together in order that splicer will not make a mistake. 
 
 As soon as cable has been pulled in ducts the Signal Corps representative 
 supervising cable pulling must complete a preliminary record which has been 
 I)repared on the ground prior to initiation of cable pulling and upon which has 
 been recorded designation number, type, and pair size of each cable of the 
 system and the number of the duct to be used in each stretch for each cable. 
 The following is also recorded: Pulled length of cable, reel number from which 
 cable was taken, and date pulled. The name of splicer and the date of making 
 each splice is entered on this record after splicing is initiated. 
 
 The arrangement of cables in manholes should be carefully planned to avoid 
 sharp bentls, have all cables accessible for inspection and repair, and keep the 
 center free for future operations. The cables shouUl be supported on the side 
 walls by hangers or supports of a type similar to tho.se shown in tigure 4-16. 
 This tigure shows the ideal arrangement for a large number of cables. Where 
 only one or two cables are in place tlu\v may be supported by means of pipe 
 straps attached to wall with screws and exi)ansion anchors. 
 
 Cable Splicing. 
 
 The splicing of cable is an operation which should be undertaken only by 
 an experienced man. In the installation of cable systems there should be em- 
 ployed for splicing the subterranean cables one or more cable splicers who have 
 previously shown that their work is satisfactory. If it becomes nece.ssary to 
 employ one who is not known, his work should be closely scrutinized by person 
 in charge of the installation until satistied that he is competent. 
 
 The importance of the above will be realized when the fact is considered that 
 cables of any great length must necessarily contain a number of splices, and 
 that a splice poorly made may not only make "test after laying" (which will 
 be described later) indicate 'that the cable is faulty, but may render the circuits 
 contained in the cable inoperative if repairs are not made. 
 
 When laying submarine cable the splicing is invariably acconiplislied liy the 
 personnel of the cable ship. These men have bad a wlile expi-rience in this 
 branch of work and are experts in their line. 
 
 The Signal Corps issues a chest containing all necessary tools for the work 
 of si)li(ing cables, the contents of which are enumerated in chajUer S of this 
 manual. 
 
 Where an emergency splice must be made, the following directii>ns should be 
 followed : 
 
 SPLICING RIBBEU INSl LATION SIUMAKINK CAULE. 
 
 Materials required : 
 
 Pure rubber. Tape, okonite. 
 
 Rubber cement. Tape, friction. 
 
 Serving mallet (can be improvised). Tape, P. & B. 
 
 Small .soldering kit. Small coil .11 mils galvanized iron wire 
 Spun yarn for seizing. (seizing). 
 
 Sandpaper. Vulcanizer (if vulcanized splice). 
 
 Alcohol. 00 iier cent compound (if vulcanized 
 Splicing compound splice). 
 
 (119)
 
 20 Signal Corps Manual No. 3.— Chapter 4. 
 
 (d) Cut the ends of the cable to be spliced squarely off and have one overlap 
 the other about 15 feet. 
 
 (b) The armor wires are then carefully untwisted from one of the ends for 
 aboixt 15 feet in groups of about five. These should be carefully handled so 
 they will go back into place easily (fig. 4-17). 
 
 (c) Before unlaying armor wires some small galvanized wire, called "seiz- 
 ing," is wound tightly around the cable here to prevent the untwisting from 
 going any farther back. 
 
 (d) The jute padding is then untwisted and the core is cut off to within a 
 foot of the small wire seizing, and the jute, about 2 feet from it. Meantime a 
 seizing of small wire is wound aboiit 6 inches from the other end of the cable. 
 
 (e) The armor wires are nicked with a tile and broken off close to the latter 
 seizing. 
 
 (/) The armor wires are then smoothed with a file. 
 
 (g) The jute is stripped off the short end. 
 
 (h) The tape is taken off for 6 inches at each end. 
 
 (0 The rubber insulation is cut in cone shape with a sharp knife (lig. 4-17). 
 leaving about 3 inches of conductor exposed at each end. The copper-conductor 
 strands are spread out for li inches, the central wire being cut out of each 
 for that length. 
 
 (;■) The wires are well cleaned with fine sandpaper and the ends are inter- 
 laced and neatly and closely wound about the twisted parts of each other. 
 
 (/r) The joints should be soldered at the ends of the copper strands only, 
 using a very little resin as a flux. Care must be taken to prevent the resin 
 from touching the clean rubber surfaces. Acid soldering flux of any kind 
 must positively not be used. 
 
 A well-vulcanized insulatiou for the joint is always desirable, but proper 
 vulcanizing requires almost laboratory conditions and considerable extra time, 
 and where a cable is being spliced on shipboard with ship pitching in rough 
 water, time may be a vital factor. In view of this, there has been developed 
 by the Signal Corps a method of iusulating submarine cable joints without 
 vulcanizing, which has proved highly satisfactory. The joint produced by this 
 method is termed a "raw joint" and has been used willi marked success 
 for over live years by personnel of the U. S. Army transport Jiiirnsidc. The 
 cable ends are prepared and the two ends of conductor joined as described 
 al)ove. Continued description is as follows : 
 
 III jireparing the conductor of each cable before joining same, allow at 
 least 2 inches of the core to be exposed from where it comes out of the 
 jute to the end of the cone or "pencil point" of the rubber insulation. One 
 inch of this will be taken up in forming the cone shape, the other inch of 
 exposed core retaining its original cylindrical shape. 
 
 liefore proceeding further it is w(>ll to note that u])ini tlH> ih'kikm- care 
 in i)reparing tliese 2 inclu^s of core at either side of lh(> jitiiit, may depiMid 
 the success or failure of tlH> insulating (pialities of the finished splice. 
 
 In shaping lh(; cone, wiiicli is done with a sharp knife, the core is grasped 
 in the left hand and iMillcd taut; at the place where the cone is to terminate 
 nick the surfiicc ni' ilic nililicr fur a marker, placing the forefinger of the 
 left hand for su])iiort under that part of the core where tiie cone is about 
 to b(» shaped, <-(»nnnence making the cut, <lrawing the blade of the knife 
 toward the hand holding the core, giving the blade a sawing movement, 
 which will assist greatly in the cutting, particularly if the rubber is soft 
 anil fresh. Do not try to make s[)eed or save labor by fornung the cone in 
 
 (120)
 
 Cable and Cable Systems. — Chapter 4. 
 
 21 
 
 (121)
 
 22 Signal Corps Manual No. 3.— Chapter 4. 
 
 only four or five cuts. After the coue has been shaped with the knife as well 
 as possible, care having been taken at all times not to nick the copper con- 
 ductor, a piece of rough sandpaper, about No. 2, is then used to round up 
 the cone, removing all flat places and ridges, this sandpapering also con- 
 tinuing vigorously and thoroughly over that portion of the core which re- 
 tains its cylindrical shape. Any flat places or ridges not removed from this 
 part of the core will have a tendency to form grooves along the core under 
 insulating material which will cover it, allowing moisture to woi*k its way 
 in to the conductor. 
 
 If the cylindrical part of the core is not thoroughly cleaned and roughened 
 by the sandpapering, that adhesion which is necessary between core and insu- 
 lating material wrapped on will not take place. 
 
 The conductors having been joined and the ends soldered, the rubber core 
 and conductor over which the insulation is to be wrapped should be washed 
 Avith alcohol on a piece of clean cloth or waste to remove any oil, dirt, or mois- 
 ture that may have been deposited on them due to handling. 
 
 Allow adhering alcohol to evaporate. If necessary, then scrape the rubber 
 with the edge of knife blade, to remove any lint or threads that may have been 
 left on the rubber after washing with alcohol. 
 
 The joint is now ready for the insulating materials to be wrapped on. 
 
 The part of joint most susceptible to leakage is where the insulating material 
 and rubber core join. A good grade of rubber cement, such as is used for patch- 
 ing the inner tubes of automobile tires, should then be put on the rubber core 
 and rubbed into the pores of the rubber, which has been roughened and scraped 
 for this purpose. When this first coating, which has been put on rather thin, 
 has dried — which it will do almost innnediately— a second coating should bo 
 applied, and if necessary a third, the object being to form a thin coating or 
 sleeve around the core, which becomes a part of the core itself. As this last 
 coMting becomes sticky (as it does just before drying), a piece of pure ruber tape 
 about 3 or 4 inches in length is wrapped on, commencing about a quarter of an 
 inch from the point of the cone, across the bare conductor, and running up to the 
 other cone for about a quarter of an inch ; the wrapping is then continued 
 back to the starting point, each turn overlapping the previous one. Now, hold- 
 ing the unused end of the rubber tape with one hand, cover the freshly wTapped 
 rubber with a thin coating of cement, distributing it eveidy and quickly, 
 then wrap on another layer of pure rubber. Apply a thin coating of cement 
 over this also. Next wrap on the splicing compound, conunencing at the large 
 end of the cone, wrai)ping over tlu« pure rubl)er and up to the large end of the 
 other cone, then back again, continuing till the joint has been built up slightly 
 larger than the original core. No cement is used between or over tlie layers 
 of splicing compound. 
 
 Again ai)i)ly the cement to Uiat i)art of the core as y(4, unwrapped, and 
 when ready, wraj) onto the core two layers of okonite rubbi'r tape, which will 
 bring that part of the core to the same diameter as the joint ; continue the third 
 layer of okointe all the way across the Joint, build up the core on that side, 
 then continue ba<-l< across the joint to the starting jioint. Touching a warm 
 iron to the end of tlie okonite will kee]) it from unwrapping when you let go 
 of it. 
 
 Now wrajt one layer of Iriclioii tape over the joint Ironi cml to end. allow- 
 ing the tape to overlaf) about half its width each turn, this wrapjting to be put 
 on as tight as possible, to act as a compress and binder for the rubber over 
 which it is laid. 
 
 (122)
 
 Cable and Cable Systems. — Chapter 4. 23 
 
 Over all of this wrap two layers of I*. & I!. tai>e, commencing at one end of 
 the joint ; wrap completely across, and then back again to the starting point, 
 occasionally warming the tape with a torch, if necessary, to make it lay on 
 close and even. 
 
 The joint is now ready to be warmed up. Ai)ply the flame of the gasoline 
 torch directly to the P. & B. tape, moving the tlame back and forth along the 
 top, bottom, and sides of the joint until the insulating compound in the 
 P. & B. tape is melted and commences to drip. Then, for convenience in han- 
 dling while laying on armor wires, wraj) on one layer of friction tape with 
 just enough tension to make it lay on evenly. The joint is now ready for the 
 armor wires to be laid on. 
 
 Note. — The compound of the P. & B. tajie, which is in itself an insulator, 
 will, when melted as above, give sufficient heat to cause the okonite tape to 
 form a rubber sleeve over the joint. The friction tape between the okonite 
 and P. & B. serves the purposes of a form or compress, holding the okonite, 
 which has been wrapped on with some tension, and preventing its opening up, 
 due to its own tension, if tlie lieat should not be evenly applied to all points 
 simultaneously. The pure rubber next to the copper conductor, which is pri- 
 marily put on for the purpose of preventing possible deterioration of the cop- 
 per by the rubber compounds, will, when put on as in the above joint, serve as 
 an extra precaution against leakage. 
 
 (I) The armor wires are then returned to place, which they will easily do 
 if care has been taken in handling them. It will be observed that over 1.5 feet 
 of the armor from one side will lap over that end from which the armor was not 
 removed. 
 
 (m) The armor replaced, the wires are then bound in place with several 
 seizings of small galvanized-iron wire tightly and evenly wrapped. 
 
 (h) The entire splice should then be served with a closely wound layer of 
 spun yarn. The proper way of doing this is with the serving mallet. (See 
 fig. 4-17). (^f course, if means are not present to do it <jtherwise, it shoulti be 
 served by hand. 
 
 (o) After splicing, the bight should be carefully lowered by small ropes 
 attached to each side of it to prevent straining or jerking the splice. 
 
 THK VULCANIZED .JOINT. 
 
 As previously stated, a well-vulcanized insulation for a joint is always 
 desirable and should be made as follows: The preparation of the cable ends, 
 the joining of copper conductor, the coning of insulation, the application of 
 first layer of pure rubber tape, and the replacing and serving of armor wires 
 should be accomplished identically as just described for the " raw joint." 
 consequently only the remaining insulating of conductor splice will be described 
 in the following remarks. 
 
 A 60 iier cent rubber compound in the form of tape is wrapped closely, 
 smoothly, and evenly over the pure rubber previously placeil. the edges of the 
 former overlapping each other, until the joint has been built up to a slightly 
 larger diameter than the mold in which it is to be compressed and heated. 
 Great care should be exercised in all wrapping to preclude the possibility <»f 
 air pockets forming beneath the layers. Before being placed in the vulcanizer. 
 a piece of paper should be folded and laid over the joint to prevent com- 
 pound sticking to mold. After the vulcanization has been completed and 
 the joint removed from mold the edges of paper may be trimmed with shears 
 and then imusteneil and scrubbed off so joint can be insi)ecte».l for flaws. In 
 
 46581°— 17 9 (123)
 
 24 Signal Corps Manual No. 3. — Chapter 4. 
 
 all vulcanizing of joints the compounds placed as just stated are subjected 
 to compression and heated to an even temperature approximating 220° F. 
 lor approximately 40 minutes. 
 
 There are various ways of accomplishing the above. It is believed that 
 electric vulcanizers which have been used by the Signal Corps on the U. S. 
 Army transport Biiniskle are the most satisfactory apparatus for this work 
 where a source of electric current is available. They are a specially con- 
 structed heater equipped with proper resistance for maintaining required 
 temperature for a given voltage. The heater consists of two pjirts so arranged 
 that when the upper is clamped to lower a groove in upper half comes directly 
 over groove in lower half forming a concentric aperture somewhat larger 
 than the diameter of the cable core and several inches in length. In between 
 these two electrically heated plates is placed the joint to be vulcanized, the 
 upper plate being forced down toward the low^er plate by means of a hand 
 screw, which keeps the joint under pressure during the time of vulcanization. 
 
 Where it is not practicable to use the electric vulcanizer, such as for portable 
 work, remote from a source of supply of electric current, and it is desired to 
 make the joint as with the electric vulcanizer, the same results can be obtained 
 by the use of two iron blocks each about 2 inches square and 6 or 8 inches 
 in length with a semicircular groove in one side of each block extending the 
 full length, and the blocks so arranged by means of dowel pins, or preferal)ly 
 a shoulder running the full length of both sides of the lower block, to assure 
 the alignment of one groove over the other when the two blocks are placed 
 together. In the top of the upper block a hole is bored of sufficient size and 
 depth to permit of the insertion of the bulb of a thermometer for the i)ur- 
 ])ose of observing the temperature of the blocks. A couple of ordinary iron 
 hand clamps are then used to press the upper and lower blocks together on 
 the joint to be vulcanized, and heat applied with a gasoline torch. By watch- 
 ing thermometer closely any desired temperature can be maintained, as the 
 mass of the iron blocks is sufficient to prevent sudden variations of the 
 temperature. 
 
 "When the electric vulcanizer or the iron l)]ocks previously doscrilied are not 
 available the joint can be vulcanized by using hot ])arafhn, as follows: After 
 having completed the wrapping of the rubber compound, wrap on over this 
 as tightly as i)ossible two layers of friction tape lo act as a binder or compress, 
 extending this wrapper of friction tape well back on llie original rubber <-()re 
 so that any part of the original rubber core Hint ni;iy also be in Ihe i)Mra(rni 
 during the time of vulcanization will not be exposed. If this precaution 
 is not taken the rubber core itself may be injured. In addition to the friction 
 tape it js a<lvisable to wrap twine lightly over the outside of the joint at the 
 ends where the new rubber compound is wrai)ped onto the cone shapes of 
 the original rubber core, as it is at these points most dillicult to secin-e that 
 cohesion which is necessary for a water-tight joint. After the joint has been 
 vulcanized and cooled this twine may be cut and taken olT. 
 
 The paraffin is heated by placing the tray in which it is contained over the 
 flames (tf a gasoline furnace, and when brought up to the proper temperature, 
 which is determined by means of a thermometer immersed in the paraffin, the 
 joint is then placed in the paraffin and allowed to renuiin the required length of 
 time. Fr«'(iu('nt readings of the thermometer are made during the time of 
 immersion of the joint in order to maintain an even heat. The temperature 
 readings should be taken <-los(' to ihe. joint, as under certain conditions there 
 may be a wide range of different temperatures in tlie same tray. 
 
 (124)
 
 Cable and Cable Systems. — Chapter 4. 25 
 
 AN'lioro tlu> 00 piT fi'Ut cuuipuuud and the tiim,' lor ahovo is not avnihililf, a 
 puxl water-tifTlit j»»iiit can be made by usinj,' tbe i)ure or " Para " rubber entirely. 
 Tins rublRU- cut into strips of about tbree-fourths intli widtli sliould lie tlior- 
 oujibly warmed and wrapped on closely and smootldy l»ut not too tijriitiy. If 
 the I'ara is wrapi)ed on cold and stretched ti;:htly it may he found that when 
 the joint is remove<l from the heater, the conductor, instead of bein;r in tiie 
 center, has been forced to one side ; and althou^di from outward appearances 
 the joint may appear perfect there may be no more than a thin tiim of ruhi)er 
 covering; one side of the conductor. Tiiis jiossiide condition is eliminated by 
 thoroughly warming the rubber before wrai»ping on, as the rubber will then 
 pull in two before the tension with which it is wrapped on becomes great 
 enough to cause the condition of nonconcentricity as shown above. 
 
 The electric vulcanizers wliich have been furnisheil the Biirnside in making 
 joints t)f this kind give a temperature of 220° F., and allowing the pure or 
 Tara rubber joint to remain in these heaters for 15 to 20 minutes at that heat 
 lias been found sutlicient time to give a good water-tight joint. 
 
 In all of the above methods it will be noticed that a considerable length of 
 time and preparation is required for the heating process alone, in addition to 
 \\ hicli there is the time required for the preparation of the jijint before heating, 
 as also the replacing of the armor wires, putting on the seizing wires, and 
 serving over the whole splice with spun yarn. 
 
 On the cable ship this element of time is a large factor in deti'miiiiing the 
 kind of joint to be made; especially so has this been the case on the Biinisidc 
 during the last several years, most of the work being in Alaskan waters during 
 the winter months, under the most unfavorable weather conditions, when the 
 successful accomplishment of repairs being made may depend upon the expe- 
 diency with which the various operations pertaining to the repairs are per- 
 formed. 
 
 SPLICING PAPKK-INSULATION SUBMARINE CABIJ*:. 
 
 The armori'i! portion of the cable is treated as described for rubber insu- 
 lation submarine cable, except that extra precaution should he taken in covering 
 the lead sleeve of splice, especially where outside diameter of sleeve reduces to 
 outside diameter of cable sheath. It may be necessary to till in between armor 
 wires of cable with extra lengths of armor wire, due to enlarged diameter over 
 sleeve, before serving completed splice with spun yarn. 
 
 The details of the splice otherwise conform to description for the si)licing of 
 all paper-insulation cables appearing later under this subject. 
 
 This tyi>e of cable is fre(iuently used in underground construction where 
 trenching is re-sorted to. With such use an alternative method of protecting 
 the splice is to cover it with a 3 or 4 foot length of iron pipe, it being 
 necessary to slip pipe over one end of cable before splicing is started. When this 
 method is employed, the piiie .should be left in a position slightly off the horizon- 
 tal, in order that water will not be apt to stan«l in pipe. With a well-made joint 
 the only objection to water in pipe is the likelihood of it freezing. 
 
 SPLICING OF ALL PAPER-INSULATION CABLES. 
 
 Material required. — The following inattMi.il will he i-etpiired ftir each splice: 
 (ff) Paper sleeve.s, or their approved e((uivalent, for covering the joint in 
 each conductor. 
 
 (6) Paraffin for drying the splice. 
 
 (125)
 
 26 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 (c) Strips of nuislin, or its approvod ocp.iivalont, fur wrapping tlie splice. 
 
 ((f) Lead sleeves. 
 
 (e) Solder for seams and wiped joints. 
 
 (/) Gummed paper for limiting the wiped joints. 
 
 Before being used the paper sleeves should be immersed in liot i)aralhn, or 
 otherwise thoroughly dried, until they are entirely free from moisture. 
 
 For wrapping the core after splicing and for binding the ends of a splice, 
 strips of muslin, or its approved equivalent, should be used. 
 
 Sleeves should be made of the same material of which tlie cabh' sheaths arc 
 made or of pure lead. 
 
 The thickness of the lead sleeve covering the si)lice shall be one-eighth of an 
 inch when the inside diameter of the sleeve is 3 inches or less, and three-six- 
 teenths of an inch when the inside diameter of the sleeve is more than 3 inches. 
 
 The dimensions of sleeves which may be used in splicing cables of various 
 sizes are given in the following tables. Where the cables to be spliced together 
 are not of the same size, the proper sleeve for the largest of the cables shall 
 be used. 
 
 Jjcad .s'/cercs- for f<trciifilit s/iUcc-s. 
 
 No. 19 gauge wire. 
 
 No. 22 gauge wire. 
 
 Niiinl)er 
 of pairs. 
 
 Inside 
 diameter. 
 
 Lengtli. 
 
 Inside 
 diameter. 
 
 Length. 
 
 15 
 20 
 25 
 30 
 50 
 75 
 100 
 
 ir,o 
 
 ISO 
 200 
 300 
 400 
 
 Inches. 
 1 
 
 n 
 1^ 
 
 2 
 
 2 
 
 2\ 
 
 3 
 
 3 
 
 3i 
 
 3* 
 
 4 
 
 Inches. 
 16 
 16 
 16 
 16 
 16 
 16 
 16 
 18 
 18 
 18 
 22 
 
 Inches. 
 1 
 1 
 
 1'. 
 1'. 
 2 
 21 
 
 2i 
 
 2.\ 
 3" 
 3i 
 3§ 
 
 Itiches. 
 16 
 16 
 16 
 16 
 16 
 16 
 16 
 16 
 16 
 18 
 18 
 22 
 
 1 
 
 Lead sleeves for 3-way or " Y " spUccs. 
 
 No. 19 giiage wire. 
 
 No. 22 gauge wire. 
 
 Number 
 of pairs. 
 
 Inside 
 diameter. 
 
 Length. 
 
 Inside 
 diameter. 
 
 Length. 
 
 10 
 20 
 25 
 30 
 50 
 75 
 100 
 l.W 
 
 180 
 200 
 300 
 400 
 
 Inches. 
 1 
 
 ij 
 
 2 
 
 2i 
 3 
 3i 
 
 4 
 4i 
 
 4i 
 
 Incites. 
 16 
 16 
 16 
 16 
 16 
 16 
 18 
 18 
 18 
 22 
 22 
 
 Inches. 
 
 1 
 
 1.', 
 
 1'. 
 
 2 
 
 2.'. 
 
 3 
 
 3i 
 
 4 
 
 4 
 
 4 
 
 4.', 
 
 4i 
 
 Indies. 
 16 
 16 
 16 
 16 
 16 
 16 
 18 
 18 
 18 
 18 
 22 
 22 
 
 i 
 
 For splicing cables with larger conductors than arc given in the tables, 
 sleeves may be used of which tiie h-ngtii is al)out dgbl times the outside 
 diameter of tlie cable and of which the inside diameter is alxMil .10 i)er ctMit 
 greater tlian the outside diameter of the cable. 
 
 (126)
 
 Cable and Cable Systems.— Chapter 4. 
 
 So far as possililc, splices >IhiuI(1 Ik- liiiislictl .-ukI sdldcri-tl till' (lay tiny aiv 
 begun. Where necessary, if the surroundings he dry, an nntinislied splice may 
 l)e left open overnight provided it l)e carefully wrapped and jirotected rniiii 
 moisture Ity a rul)i)er blanket or other suitable covering. In wet or daniii 
 surroundings, however, work on a splice should i)e continuous until tinishetl. 
 In such cases the splice shonld be "boiled out" with paraflin at interval."* — 
 say. after eacii .10 ])airs have been coiuiected. 
 
 Fig. 4-18.— CABLE. PAPER INSULATION. SPLICING. 
 
 Whenever it may be necessary to leave the cable end it should he thoroughly 
 dried and sealed with solder, as much care being taken as if the joint were 
 to be permanent. 
 
 If it is suspected that moisture has entered the end of a cable, a short length 
 of it should be cut off and dipped into hot paraflin. when the presence of 
 m(»isture will be indicated by a characteristic frying sound. If there is len.L'th 
 to spare, the cable should be cut back, a short portion at a time, until it gives 
 no eviilence of dampness. 
 
 After this the end should be thorouglily drieil with paratlin and a splice 
 made or the end sealed, as already described. 
 
 The operations of making a straight splice in their sequence are as follows : 
 
 1. After being sure that no moisture exists in either of the cable ends to 
 be spliced, remove the lead sheath from eai-h end for a distance equal to the 
 length of the lead sleeve used. 
 
 ^^5/ 
 
 /> 
 
 ^ 
 
 m 
 
 2 
 
 r 
 
 Fig. 4-19.— CABLE, PAPER INSULATION, SPLICING. 
 
 In removing the sheath care must be taken not to injure the insulation 
 of the wires. (Figs. 4-lS and 4-11).) 
 
 (127)
 
 28 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 2. The core is tightly bound witli strips of muslin, or its approved equivfl- 
 
 lent, at the end of the cable sheath, patking the binding close to the sheath. 
 
 This is done to prevent the wires from being cut on the edge of the sheath. 
 (Fig. 4-20.) 
 
 Muslin 
 
 Fig. 4-20.— CABLE, PAPER INSULATION, SPLICING. 
 
 3. In general, as soon as possible after the removal of the lead sheath the 
 exposed conductors are thoroughly " boiled out " by pouring hot paraffin over 
 them until all traces of moisture are removed. The binding must be saturated 
 with paraffin as well as the core. Enough paraffin remains in the core to form 
 a seal, which protects the cable against moisture while the splice is being 
 made. The temperature of the parattin should be above that of boiling water, 
 but must not be high enough to scorch or make brittle the paper insulation. 
 
 In drying or '• boiling out " a splice with paraffin, always work away from the 
 cable sheath toward the end of the conductors or middle of the splice in order 
 to prevent any moisture being driven under the sheath. The paraffin should be 
 poured on with a ladle. The paraffin draining off may be caught in the melting 
 pot or a pan 
 
 Fig. 4-21.— CABLE, PAPER INSULATION, SPLICING. 
 (128)
 
 Cable and Cable Systems. — Chapter 4. 
 
 29 
 
 4. The ciuls of tlu- lahlf slicatlis ami <<( tin- lead sleev»* sliouhl 1)0 scraiied 
 l)riKht fur 3 or 4 inches and rubbetl wiili lallow, or its approved eipiivaleiit, to 
 Iveep them clean during tlie suljsequeut work on tlie splice. The tallow also acts 
 as a llux in niakinj,' the wiped joints. 
 
 5. The lead sleeve is next slipiied over the end of one cable and moved hack 
 out of the way. 
 
 0. The two cables are placed an«l lirinly secured in the same straight line, 
 with the distance between the ends of the sheaths alntut 3 inches less than the 
 length of the lead sleeve. 
 
 Fig. 4-22.— CABLE, PAPER INSULATION, SPLICING 
 
 7. After the cables are in position the conductors are bent out of the way and 
 shall then be spliced in the following manner: 
 
 8. Starting at the center or the lower back side of the cables, a pair of wires 
 from each cable is loosely brought together with a partial twist (a, fig. 4-21), 
 thus marking by the bend in the pairs the point at which the j(»int is to be made. 
 Slip a paper sleeve over each wire of one pair and push the sleeves back far 
 enough to allow room for making the joint. 
 
 Fig. 4-23.— CABLE. PAPER INSULATION, SPLICING. 
 (1291
 
 30 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 The wires are now to be connected by a splicer's ordinary twist joint {h, 
 fig. 4-21). The like wires from the two pairs to be spliced are brought to- 
 gether at the point marked by the bend and given two or three twists (c, 
 fig. 4-21). Remove the insulation of both wires beyond the twist, being care- 
 ful not to nick or scrape the conductors. The wires are now to be bent as 
 
 Fig. 4-24.— CABLE, PAPER INSULATION, SPLICING. 
 
 shown and twisted together as if turning a crank. This action insures good 
 contact even though the wire may be coated with a film of paraffin due to 
 the " boiling out " process. The ends are cut off, so as to leave the twist of 
 bare wire not less than 1 inch in length. The twist is bent down along the 
 insulated wire and the paper sleeve slipped over the joint {d, fig. 4-21). The 
 completed joint, with the sleeves in place, is shown in e, figure 4-21. 
 
 Fig. 4-25.— CABLE, PAPER INSULATION, SPLICING. 
 
 For conductors of large size (No. 13 B. & S. gauge or larger) the wires may 
 be joined by means of a Western Union Telegraph joint or other approved 
 method. Tlic joint is covered with a paju'r sleeve. 
 
 Fig. 4-26.— CABLE, PAPER INSULATION, SPLICING. 
 (130j
 
 Cable and Cable Systems. — Chapter 4. 
 
 31 
 
 III spliciiifT. catv shoiihl \>v liiki-ii to sjiliie ilic ceiilcr ami lower pairs tirst, 
 foriiiiiiK tlie outer pairs about tJie (viili'r pairs so tliat the tiuishetl splice may 
 liave a uniform shape. 
 
 In piekiufr out the pairs to be .sidjced lo^ieljier care sliouhl be taken to trans- 
 pose the circuits thoroughly. It is sullicient if the transposin;; lie done between 
 pairs in tlie correspond injr layers of the two cables. 
 
 The wire joints should be distributed alonjx the whole len;,'lli of the splice 
 in order to keep the .spliie uniform in size and shape. 
 
 9. When all the wire joints have been ma<le, the splice is afrain "boiled <iut " 
 with hot parallin until all traces of moisture have been removeil. In apiilylufi 
 this parallin, work from the ends of the si»lice toward the middle. 
 
 10. The splice is then wrajiped with strips of muslin, or its approved ecpiiva- 
 lent, and compressed until the lead sleeve will just sliji over the splice. Tare 
 mu.st be taken not to compress the splice too tijrhlly or tin' wires may be forced 
 through the insulation and .ro^.w in the splice result. 
 
 Fig. 4-27 —CABLE. PAPER INSULATION. SPLICING. 
 
 The splice is dried out with hot paralbn after the tirst wrapping of muslin 
 has been put on and apain after the wrapping.' of the .splice is complete. The 
 dryiuff out is continued until bubbles cease to appear on the splice. 
 
 11. The lead sleeve is slipped into place before the splice has had time to 
 cool, taking care, however, to see that the sleeve is perfectly dry. 
 
 The ends of the sleeve, which should overlap the cable sheath at each end by 
 about 1* inches, are beaten down to conform to the cable sheath and a wipe<l 
 joint carefully nuide at each end. In making the wiped jtiints strips of gumuKtl 
 paper may be used to limit the joints. 
 
 Wiped joints should be carefidly inspected, using a mirror when necessary 
 to detect any imperfections in the .'jeal. 
 
 TllKKK-WAV OK "Y SIM. ICES. 
 
 The method of making a thret^-way or Y splice Is the same as for a straight 
 splice except in the following particvdars: 
 There are two general tlas.ses of Y splices — 
 
 1. Whea-e the cables all end at the splii-e. 
 
 2. Where a branch cable is to be spliced into a contiiuious cable. 
 
 In the tirst case the method is generally similar to a straight sj)lice. The 
 sheaths of all three cables are removeil for a length equal to the length of the 
 lead sleeve. The two cables forming the main cable are secin-t»«l in n straight 
 line with the distance between the ends of the sheaths about 3 inches less than 
 the length of the sleeve. The bran<-h cable is la.she«l beside one •)f the main 
 cables with the end of its sheath opitosite the end of the sheath of the mulu 
 cable.
 
 32 Signal Corps Manual No. 3. — Chapter 4. 
 
 The joint is made by twisting together lilce wires of pairs from each of the 
 three cables, taking care to include two or tliree twists of the insulation in the 
 joint in the manner hereinbefore described for straight splicing. 
 
 The lead sleeve in this case may be a whole sleeve. It should be slii^ped on 
 and pushed back on that portion of the main cable away from the branch. 
 
 In the second case a split lead sleeve must be used. 
 
 The sheath of the main cable shall be removed for a length of about 3 inches 
 less than the length of the sleeve. The sheath shall be removed from the end 
 of the branch cable for an equal distance. 
 
 The branch cable is lashed to the main cable, with the end of the sheath 
 opposite the end of the sheath of the cable. 
 
 A pair of conductors in the main cable is cut. To one end of each conductor 
 is spliced a short piece of bare wire of the same size as the cable conductors. 
 This wire should be twisted into the insulation two or three times, in order to 
 prevent its pulling back on the conductors. The second end of the main con- 
 ductor, the free end of the bare wire, and a like conductor of a pair in the 
 branch cable are twisted together, in the manner already described, and covered 
 with a paper sleeve which is long enough to cover both ends of the bare wire. 
 
 If there is slack enough in the main cable, the joint may be made without 
 splicing in the bare wires. 
 
 In putting on a split lead sleeve the seam must be carefully soldexed, then the 
 ends beaten down to conform to the sheaths of the cables and soldered with 
 wiped joints at each end. Care should be taken to retouch the ends of the 
 seam after the wiping is complete, in order to make sure that the seam has not 
 been opened while the wiping was in progress. 
 
 A grooved wooden block should be placed in the fork of each Y splice, in 
 order to keep the cables apart. This block is kept in place and the cables at 
 the same time protected from the iiossibility of too great a separation by 
 means of a wrapping of wire soldered to the cable sheaths. 
 
 POT HKADS. 
 
 It will readily be, seen that it is impracticable to connect to terminals, con- 
 ductors of a cable wrapped with manila paper. Where it is desired to termi- 
 nate such a cable, a rubber-covered wire is spliced to each conductor. A lead 
 sleeve fastened to lead sheath of cable by means of "wiped joint" is used to 
 house such si)lices and also as a container for an insulating moisture repellant 
 compound, which is jiourcd as hereinaffcr desci'ibed. 
 
 MKTHOl) OK MAKING A VOT HKAl). 
 
 This description covers the method of making a llexible cable terminal or pot 
 hea<l for terminating the conductors of a lead-incased, dry-core, ))aper-insulation 
 cable, with rui)l»er-covered conductors, and at the same time effectually sealing 
 the lead-incased cal)le against the ingress of air and moisturt>. 
 
 The lead sleeve or pipe of this terminal slumld have a lengtli of eight times the 
 outside diameter of the cat)le to which it is to be attaclicd, jilus 10 inches, and 
 an outside diameter of at least one and one-linlf times the outside diameter of 
 llie lead ("liiic. Tlie l(>ad sleeve sliouhi linve a tlii<'l<ness not les-s than that of 
 the shealli <■ ' tlie lead cable. 
 
 The wires of this terminal, which are to be sj>liced to those in the lead cable, 
 slutuld be covered willi okonit(> insulation or its aj)prov(Hl ecpiivalent. The 
 MililMi-covcii'd wires niav be loose or in tlie form of a tai)ed cable, and should 
 be of the size and length retpiired. .The Signal (.'orps sui)plies a rubber-insu- 
 
 (132)
 
 Cable and Cable Systems. -Chapter 4. 33 
 
 latldii twlstt'd pair wire, kiKnvii as iMit-hcad wiiv, lor tlu' [>iiriM»si' when loose 
 wires are eiiiiiloyed. 
 
 All tape used in the terminal should he adlicsivi' or ruhher tape of tiie best 
 quality. 
 
 The paper or cotton sleeves u.sed should he of the ordinai-y form for eovering 
 wire joints in paper-lnsidation cahle. 
 
 The tuhe for addinj; the compound to the terminal should have an inside 
 diameter of one-half inch and a h-nirth 2 inclu-s less than that of the It-ad 
 sleeve. The tube shouhl have thin walls and may lie made of metal, vul- 
 canized llher, or manila paper i-olled alVmt a half-im-li i-od and hound thcicin 
 with striufi. 
 
 "While the use of this tuhe is desirable it is not necessary if ^'reat care is 
 taki'ii to have the compound reach bottom of sleeve. 
 
 The sole leather should be ajiproximately three-sixteenths of an inch in thick- 
 ness, 3 inches in width, and lonj; enoufih to wrap once about the tajied cable 
 or rubber-covered wires. 
 
 Heavy cotton twine or wicking should be used for bindin;; purpt»ses. 
 
 The wiping solder used should be the commercial plumber's wiping .solder, 
 which is composed of 60 per cent lead and 40 per cent tin. It is sometimes 
 advisable to add a slight amount of half and half solder (.")0 per cent lead and 
 50 per cent tin) to slightly increase the proportion of tin. The latter is decided 
 by the action of the alloy. 
 
 The sealing compound should be of any approved waterproof, semielastic, 
 insulating material, which, when melted, will How readily into the lead sleeve 
 and about the wires and adhere tenaciously to the wires and lead sleeve. The 
 compound should not be sufficiently affected by the conditions of exposure as 
 to endanger the seal. 
 
 No. 1 ozite is the compound most commonly used. 
 
 DIRECTIONS 1 OK SKITINC Tl' THK I'OT HKAO. 
 [See fii.'. 4-2S.1 
 
 No paraffin shall be used in "lioiling out"" cable ends and sleeves for pot 
 heads. 
 
 The proper amount of sheath should be removed from the lead cable, the 
 lead sleeve slipped over the cable, and the cable wires .spliced to the rubber- 
 covered wires in the usual manner, using paper or cotton sleeving. 
 
 In doing this work care must be taken to remove all i>ieces of jiaper, jute, 
 tape, or other things which might obstruct the tlow of the compound, which is 
 to be poured in after the lead sleeve is in place. 
 
 Close to the end of the lead cable sheath the paper-insulat«'tl wires should 
 be tightly wound with a number of layers of twine or wicking in such a maimer 
 as to prevent the compound from entering the cable. 
 
 If rubber-insulation cable is u.sed for extending the coiuUutors of paju-r- 
 insulation cable, the preceding remarks are applicable and the outer braid or 
 covering t>f the rubber cable should be removed in order that the <"onductors 
 may separate. About lA inches of the cable, with braided or other covering, 
 should enter the sleeve. 
 
 At that point on the rubber-covered wires or rubber-insulation cable which 
 will come immediately at the end of the lead sleeve should be wrajiptMl. lirsi. a 
 single layer of sole leather, and over this several layers of adhesive or rubber 
 tape. The leather should enter the finished spli«v about IJ inehes and i>roje<'t 
 the same distance. 
 
 (l.">r>)
 
 34 
 
 Signal Corps Manual No. 3.— Chapter 4. 
 
 Rubber cabfe or nines 
 
 Rubber rape 
 Leather collar 
 
 Fig. 4-28.-CABLE, PAPER INSULATION, CONSTRUCTION OF POT HEAD. 
 
 (134)
 
 Cable and Cable Systems. — Chapter 4. 35 
 
 Tlu' eiitiio splire shoulil next lie opened np as nnu-li as possible in onler that 
 the sealing compound may flow readily iihout every wire. If a hemp ford he 
 found in the rubber cable it should be cut olT as close as possible to the cable<l 
 portion. 
 
 The one-half incli tube should then be laid alonj: in the splice with one end 
 on a line with the end of the lead cable sheath and fastened in position with 
 several turns of twine. This twine .serves the double purjxtse of keei)in}r tlie 
 tul)e in place and reducing the splice to a diameter which will allow the lead 
 sleeve to be drawn on without <listurbin!j; the sleeves C(»vering the spliced wires. 
 The turns of twine should not extend beyond the last of the wire joints on the 
 ruiiber-covered wire end of the s|)lice. It should not be drawn too tij:htly but 
 should allow the comitound a chance to t'ft to the wire. If the nianila-paper 
 tube is used, the rod on which it is rolled should be ri'tained in the tube until 
 the splice is ready to be tilled. 
 
 The lead sleeve should be drawn over the splice, allowint: it to jirnjt^ct over 
 the lead cable sheath li inches, and then connected to the lead cable sheath by 
 means of a "wiped" joint. 
 
 The lead cable sheath, with sleeve attached, should now be fastened in an 
 uprijiht position, the sleeve warmed until it becomes barely possible to touch 
 it with the hand, and the sealing compound heated t<» as hijrh a temperature as 
 is possible without burning the insulation from the wires, slowly and cautiously 
 poured in through the tube, using a funnel to assist in the operation. The 
 comi>ound should fill the sleeve to within one-half inch of the top. When the 
 compound cools sufficiently, more should be poured in at the top of the sleeve, 
 the tube not being used. 
 
 After the splice has become thoroughly cold the open _end of the lead sleeve 
 shoulil be carefully dressed into contact with the taped leather which surrounds 
 the rubber-covered wires or cable. 
 
 If possible the pot head should be mounted in an upright position. When 
 it is necessary in insitle construction to place the pot head in a horizontal 
 position, the open end of the lead sheath should be wrapped with tape to 
 prevent the compound from running out, and care should be taken to locate 
 the pot head where it will not be exposed to excessive heat. 
 
 Uubber-lnsulation lead-sheath cal)les are sometimes furnished with pot 
 head where they terminate in a subterranean cable terminal box or other 
 apparatus not supplied with a means of sealing the cable. 
 
 The placing of pot head on this type of cable is a comparatively simple 
 operation, pot head being merely for the purpose of sealing the cable to pre- 
 vent moisture entering it. A short lead sleeve is placed as described under 
 pot heads for paper-insulation cable, the condu<'tors of cable extending beyond 
 sleeve sufficient distance to permit of being laced into forms and connet>te<l 
 to terminal strips. The sleeve is then filled with a suitable sealing compound. 
 When the compound cools, it will be lu'cessary to again fill the pot head, as all 
 compounds shrink perceptibly upon cooling. 
 
 SUGGESTIONS I.N RliGAItB TO SPLICKS. 
 
 In branching a small lead-covered cable from a flexible .splice or pot head 
 it is considered advantageous to run it out at the base of the lead sleeve, 
 making a double-wiped joint, rather than to run it out with the rubber-covere<l 
 wires or taped cable. . 
 
 Should occasion arise when it becomes imperative to shorten the length of 
 the leatl sleeve, a sleeve of a greater diameter than is ordinarily recommended 
 should be selected and the space occupied by the joints in the wires con- 
 
 (135)
 
 36 Signal Corps Manual No, 3. — Chapter 4. 
 
 tracted. keeping the .space between the last wire joint on tlie rubber-covered 
 wire end and the leather wrapping the same as it would be in a regular splice, 
 this being the space where the efficiency of the seal is maintained. 
 
 The sealing compound should rise at least one-half inch above the top of 
 the paper tube. 
 
 SPLICING RUBBEK-IXSULATIOX LEAD-COVKKEl) SU15TEKKANEAN CABLE. 
 (Types 213 to 210, inchislvc.) 
 Materials and tools required are: 
 
 Solder, resin core. 
 Solder, wiping. 
 Lead sleeves. 
 Cable splicers chest. 
 
 Pure rubber. 
 Rubber cement. 
 Adhesive tape. 
 Gasoline. 
 Sandpaper. 
 
 The subterranean splice should be made as follows: 
 
 {a) Slip the lead sleeve over one end of the cable. 
 
 (6) Conductors must be thoroughly cleaned without the use of acid soldering 
 flux. 
 
 (c) The insulation must be trimmed cone shaped down to the conductor. 
 Fan out strands, interlace them, and make a Western Union joint (see fig. 
 4-17). The central conductor may be removed if the joint is large. 
 
 (d) The very slightest touch of resin flux should be used. Use very little 
 solder. Do not allow resin to touch rubber surfaces. Keep the rubber clean. 
 
 (c) File off all projecting points of solder on conductor. 
 
 if) Wrap the joint after treating with rubber cement with pui'e Para sheet 
 rubber cut in strips one-half inch in width and wind, overlapping spirally. 
 Continue winding back and forth until a little beyond each of the coned ends 
 and until the thickness of the joint slightly exceeds the original insulation. 
 Rub a clean, warm iron toool over the joint until the rubber fuses slightly. 
 Wrap a double thickness of adhesive tape. Rub warm tool over the finished 
 joint, taking care not to overheat. 
 
 (fir) In splicing multiple-conductor cable, joints in pairs should be slightly 
 staggered. 
 
 The lead sleeve is then i)lace<l in position and a " wijied " joint carefully made 
 at each end. In making the wii)ed joints, strips of gunmied paper may be used 
 to limit the joint. 
 
 SPLICING OF UUnHER-KNSULATlON LEAO-COVEKKl) AND AliMOKKI) SUBTKKRANEAN CABLE. 
 
 (Types 217 .Mnd 21S.f 
 
 Material i-cijuircd llie sanu> as tiiat iireviously (>nuni('rat«Ml lor splicing rubber- 
 insulation lead-covered subterranean cable, and in addition a ball of marline 
 and small coil of .ll mils diameter galvani zed-iron wire. 
 
 (rt) ('ut t»ne cable at the point where the si)lice is to be located. 
 
 (b) The other cable should overlap the first by about 8 feet. 
 
 (c) W^rap the shorter cable tightly with .soft iron wire at a point about 18 
 inches from its end. 
 
 (d) Remove the armor from the end of the shorter cable with a hacksaw 
 and unwind the jut<'. 
 
 (e) Cut off lead armor at a ]»oint about 10 inches from the (muI. 
 
 (/) Wrap the longer cal)Ie tightly with soft iron wire at a i)oint 18 inches 
 back of where splice will (tccur. • 
 
 (g) ('ut away the jute and unwrap the armoi- wire back to the point where 
 the cable has been wrappe<l. 
 
 (h) Slip on the lead sleeve.
 
 Cable and Cable Systems. — Chapter 4. 
 
 37 
 
 (/■) PnK'ood with .joint as (k'sci-ihcij uiidcr IciKl-covfn'd calilc. 
 
 (j) Serve layer of jute or marline over joint. 
 
 (/r) Serve armor wire over joint and onto liu> slmri t-Mlilc ;ind wrap uitli 
 bare soft iron wire at its end. 
 
 (/) Serve layer of marline over the outside of rephui-d arnioi-. 
 
 When these splices are made in manholes, the armor does lot neeil to be 
 served over the joint. For permanent trenehe<l cable this should be done. 
 
 As an alternative the joint may be covered with a 3 or 4 foot lenjrth of irou 
 pipe, it beiuf? necessary to slij) i)ipe over one end of cable before the si)licini.c is 
 started. When this method is employed, the pipe should be left in a position 
 slifihtly off the horizontal in order that water will not be apt to stand in ]»ipe. 
 With a well-made joint the only objection to water standing in pipe is the likeli- 
 hood of it freezing. 
 
 
 K 
 
 3f—— 
 
 ^ 
 
 
 %^ 
 
 -i- -^ .,■ 
 
 _J) 
 
 i 
 1 
 
 1 
 
 Drill tliae holes \'diom 
 
 
 1 
 
 G' 
 
 o 
 
 o 
 
 Scale Pull size 
 
 Sleeve and gland of cast site/ 
 Cover of mild rolled steel 
 
 COVER 
 
 SIDL 
 
 EIND 
 
 SELCTION THROUGH SPLICE 
 5ptKe- to be soldered a/xi ir^sulatrd nith rubber and fncLon tape m the usual marrrer 
 •with fncL'on iapa ccrer for all arid box ft'lfcd iritfi hot corr^pound 
 
 Fig. 4-29.— CABLE, TYPE 251, SPLICING SLEEVE. 
 
 In splicing Signal Corps type 251 cable the usual lead sleeve may be used, 
 but it is. impracticable to make a wiped joint, due to small diameter and thin- 
 ness of the lead sheath of this cable, consetiut'iitly the conductors should be 
 spliced and taped as previously described for conductors of rubber insulation 
 cable and the lead sleeve formed to bind the armor of the cable at either end. 
 By means of holes through side of sleeve near each end the sleeve is then 
 filled with melted Chatterton compound and the holes sealed tightly by means 
 of solder applied with a soldering iron. 
 
 Another methoil of splicing this type of cable makes use of a manufacturetl 
 splicing sleeve designed for this purpost-. It is shown in ligure 4-20 and is 
 
 (137)
 
 38 Signal Corps Manual No. 3. — Chapter 4. 
 
 there described iu detail to such au extent that further description would be 
 superfluous. 
 
 TESTS OF SUBTERKANEAN CABLES AFTER THEY HAVE BEEN PULLED IN DUCTS AND 
 
 SPLICED. 
 
 Practically all cable purchased by the Signal Corps is inspected during manu- 
 facture by an experienced inspector detailed for that work exclusively. The 
 duty of this inspector is to watch closely the various operations at the factory 
 and to make all prescribed tests of material mentioned in the specification. 
 He should do all in his power to facilitate the manufacture, but his paramount 
 duty is to see that workmanship is of highest class, that materials used meet 
 all prescribed tests, and that the general intent of the specification describing 
 cable being manufactured is adhered to. Results of the more important tests 
 are recorded and a copy of this record forwarded to the Chief Signal Officer of 
 the Army, who has it placed in the archives, where it may be referred to should 
 occasion for such action arise. A tag bearing order number, inspector's initials, 
 and date of acceptance is attached to reel. This tag is in addition to brass 
 tag bearing Signal Corps number, which has previously been described. 
 
 In view of the above it is safe to assume that new cable is of the best 
 quality, everything considered, and it only remains necessai*y to install and 
 splice it properly in order that this very important part of an electrical system 
 will be of the highest standard. 
 
 If any recovered cable is furnished, a preliminary test of it before installation 
 should be made, and cable that does not appear to be iu excellent condition 
 mechanically or electrically should not be used. 
 
 After the cables have been pulled in ducts and splices and pot heads placed, 
 the person in charge of the installation or an assistant will test each com- 
 pleted cable. Each conductor is assigned a number. The tests of the com- 
 pleted cable will show insulation resistance of each conductor, electrostatic 
 capacity of each conductor, and ohmic resistance of each conductor. When 
 tests are made the tester carefully records data obtained in a field book and 
 when convenient computes values and enters them on Signal Corps Blank Form 
 No. 261, issued for the purpose. 
 
 AVith cables of short length it is difllcult to obtain readings, due to high 
 value of insulation and low value of electrostatic capacity, and therefore it 
 is not necessary that actual values be recorded. A statement in effect that 
 each conductor has an insulation equal to 500 megohms per mile or that the 
 tester was unable to obtain deflection on the galvanometer will be sufficient. 
 
 Ohmic resistance of conductors should be recorded. 
 
 These tests will disclose the condition of each completed cable of the system 
 and will show whether or not defective splices or pot heads have been made; 
 also whether or not the cable has been injured in pulling it into the conduits. 
 This is especially true if the cable has been sifl).1ected to moisture, <lue to 
 rain or otherwise, after all splices have been completed. The reason for this 
 is obvious, as it can be readily understood that a hole in the lead sheath 
 would not affect the insulation resistance of a cable if the cable at that point 
 is kept absolutely free of moistur(\ 
 
 The exacting methods employed in making the factory test sliduld be ignored 
 in making this field test. This means that no correction should be made 
 for temperature w for the one-tenth megohm resistance usually left in series 
 with insulation resistance bcMug measured. 
 
 (Corrections, bcnvever, sh(»ul»l be made for insulation, capacity, and ohmic 
 resistance of leads if it is lound (hal iilliiiiate values are materially affected 
 by these values.
 
 Cable and Cable Systems. — Chapter 4. 39 
 
 For acconiplisliiiij,' tlic tests just uifiitioiu'd the .Signal Corps issues an 
 electrieal instrinnent case. 
 
 The contents of this case are as follows : 
 
 KLECTRICAL INSTRUMENT CASE. 
 [This Instrument ease Is manufaetiired under specification No. 140.] 
 
 COXTHXTS. 
 
 One insulation and capacity test set, con.sisting of the following in case: 
 1 portable galvauouieter of the D'Arsouval type, conforming to that shown in 
 
 figure 4-30. 
 1 telescope and scale for above galvanometer. 
 1 ]()().0(»0-ohm box. 
 I combined shunt ai.d switch. 
 1 condenser st't. 
 1 ohmmeter. 
 
 1 tripod, external to case. 
 
 1 service testing battery, drawing No. 199/), specification No. 185. 
 1 micrometer caliper, without ratchet stop, with morocco carrying case. 
 1 inspector's pocket tool kit, as per drawing No. 204, specification No. 186. 
 1 testing telephone. 
 1 space for forms and reports. 
 1 space for books. 
 
 MISCELLAXEOl'S PARTS A.ND SUPPLIES. 
 
 1 galvanometer coil and mirror. 
 4 round-head plugs. 
 
 6 lower suspensions. 
 6 upper suspensions. 
 
 2 milled-head screws. 
 1 piece felt. 
 
 4 screws for glass. 
 
 1 ohmmeter card. 
 
 1 piece chamois. 
 
 1 bottle vaseline. 
 
 1 bottle typewriter oil. 
 
 KKl feet No. 22 bare copper wire. 
 
 1(K> feet advance wire. No. 28. 
 
 25 feet No. 22 manganln wire. 
 
 l.">0 feet No. 34 nianganin wire. 
 
 300 feet No. 40 manganin wire. 
 
 fiO feet No. 28 manganin wire. 
 
 1 glass window. 
 
 4 paper scales. 
 
 n feet battery cord. 
 10 feet okonite wire. 
 
 5 ounces solder. 
 
 REPAHl KIT. 
 
 The repair kit contains the following instruments' 
 
 1 nickel-plated screw driver. 
 
 2 pairs tweezers, nickeled. 
 
 3 lower suspensions for galvanometer. 
 
 4 upper susjiensions for galvanometer. 
 
 46581°— 17 10 (139)
 
 40 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 Description of tlie various instruments follows. 
 
 THE GALVANOMETER. 
 
 A reflecting D'Arsonval galvanometer is supplied, arranged for mounting 
 on a tripod. It is provided with a short insulated telescope arm and an 
 optical system, which magnifies the image of the scale. Owing to this magni- 
 fication, it is necessary to mount the instrument on a solid floor or to provide 
 against jars while testing, which tend to make the image indistinct. 
 
 As 'in all the instruments of this type, the frame forms conductor for one 
 side of the circuit, and the tripod legs should be wiped thoroughly dry before 
 making a test. This precautionary measure should always be taken. 
 
 The sensibility of this instrument is 300 megohms. This is determined l)y the 
 fact that one volt through one megohm will deflect the mirror 300 scale divi- 
 sions. Figure 4-30 shows the construction of this instrument. 
 
 FRONT 
 
 era Thin UotJt glued 
 
 olJH to this before yyrwmfom 
 
 DETAILS OF CLAMP 
 Fig. 4-30.— GALVANOMETER, REFLECTING, DARSONVAL TYPE. 
 
 ( I nil
 
 Part 
 No. 
 
 17 
 
 1 
 2 
 3 
 4 
 
 5. « 
 7 
 S 
 9 
 10 
 11 
 12 
 13 
 14 
 15 
 Iti 
 ,1S 
 19 
 20 
 21,22,23 
 24 
 2", 
 
 2t) 
 
 27 
 
 2S 
 
 29 
 
 30 
 
 31,32 
 
 33 
 
 34 
 
 35 
 
 36 
 
 37 
 
 38 
 
 39 
 
 40 
 
 41 
 
 42,43,44, 
 
 45,46,47 
 
 48 
 
 49 
 
 50,51,52 
 
 53,54,55 
 
 Cable and Cable Systems. — Chapter 4. 
 
 (Seeng. 4-30.) 
 
 41 
 
 Name. 
 
 Torsion head and screw 
 
 Torison rod 
 
 Tube 
 
 I 'pper suspension 
 
 Suspension heads 
 
 Mirror , 
 
 Upper chuck and screw 
 
 Coil 
 
 Masnetic core 
 
 Lower suspension with heads . 
 
 Lower chuck and screw 
 
 Field maKiiot 
 
 Front cover and screws 
 
 Rear co\er and screws 
 
 Dampening device 
 
 Terminals 
 
 Telescope rest and screws 
 
 Steady pin 
 
 Leveling screws 
 
 IJase 
 
 Telescope arm 
 
 Arm screw 
 
 Telescope screw 
 
 Telescope barrel 
 
 Ivcns 
 
 Diaphragm 
 
 Truiuiion screws 
 
 Telescope frame 
 
 Scale-adjusting screw 
 
 Scale frame 
 
 Scale 
 
 Insulating joint 
 
 Tripod head 
 
 Upper legs, triijod 
 
 Lower legs, tripod 
 
 Clamp 
 
 Clamping screws 
 
 Wing nut 
 
 Base screw 
 
 Spurs 
 
 Hinge screws and springs. 
 
 Reference 
 No. 
 
 21 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5,6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 II 
 
 12 
 
 13 
 
 14 
 
 15 
 
 16 
 
 17.18 
 
 19 
 
 20 
 
 ,22,23 
 
 24 
 
 25 
 
 26 
 
 27 
 
 2S 
 
 29 
 
 30 
 
 31,32 
 
 33 
 
 34 
 
 35 
 
 36 
 
 37 
 
 38 
 
 39 
 
 40 
 
 71 
 
 43.44, 
 
 .46,44 
 
 48 
 
 49 
 
 .51,52 
 
 ,54,55 
 
 100,(U»0-OHM BOX. 
 
 Tin' l(M»,(KHt-(iliiii l)(ix is a circular rubV>er ease liavliij,' niouiilcil ilicii'iti lo coils 
 wound with No. 40 !>. & S. uiaujianin wire. Sliould tn)ul)le oc<ur with this 
 (knice tlie proper-sized wire will be found in tlie spare-parts case, 'i'liis box 
 is held t<i;rether with two .screws. {F'lix. 4-:U.) 
 
 Fig. 4-31.— BOX, 100.000 OHM.. STANDARD. 
 (141)
 
 42 
 
 Signal Corps Manual No. 3.— Chapter 4. 
 
 COMBINEU SHUNT AND KEY. 
 
 This sluiiit nnd koy. or button, takes the place of the usual Ayrton shunt, 
 hattery key, anil short-t-ircuit key. Its connections and general construction 
 are shown in figure 4-3"2. 
 
 ^Knurled 
 
 Fig. 4-32.— SHUNT AND KEY. 
 
 The key is provided with a bayonet joint. Tlie sliunt sliould always be on 
 0.(X>01 at tile l)eginning of tlie reading, and tlie lower l)utton is tlien turned until 
 a readable dellection is obtained. 
 
 The button B controls the battery, and the button »S controls the shunt. 
 
 This method of operating the galvanometer insures against sudden heavy 
 currents and consequent violent disturbance of the moving system incident 
 to low insulation and dispenses with the short-circuit key. 
 
 btCTlON 
 
 Fig. 4-33.— CONDENSER, STANDARD. 
 
 (142)
 
 Cable and Cable Systems. — Chapter 4 
 
 43 
 
 STA N DA i:i> ( ( »M»i;.N SKIC. 
 
 Tlic stiiiitlanl coiKlciiscr set consists (if a unc-tliii'fl nii<Tnfiii'a<l ii<>ii;i(|.inslii- 
 Itk' cdndcnst'i*, with a l<»^v lor its oprration. an«l tiic necessary liiinlin;: posts 
 and pliij,'s, as sliown in tiunrc 4-.'};{. Its conn«'ctions arc also sliown in the 
 li};ure. Hy niovint: tlie switcli N to the rijilit either liie calile or condenser may 
 he char;;ed, (h'i»cndin.ir on tlie location of tlie phi;r. Tiie condenser is of l»<'st- 
 firade mica, wiih n'<iri and beeswax tillin;;. 
 
 SKRVU'E-TKSTl \(! ItATTKUY. 
 
 The service-tostiiiLC l)attery consists of 1(H) cells o!" simmII dry hMlteries. (Fit:. 
 4-,'U. ) They should l»e examined once a month. 
 
 The battery is tapi»ed for "., ](>, 2."). fid, 7.".. and KHt cells. When new it should 
 have an K. M. F. I>etweep. 140 and "i">0, and slioidd not drop below KX* within 
 a year. When certain cells show deterii>ration they should be removed and the 
 circuit restored. New cells throujihout should be rtHpiisitioned for when a 
 majority of the cells show discoloration and the voltage of the whole battery is 
 under 80 with all connections in good order and the poorest cells cut out. 
 
 Care must be exerci.sed to keep the battery connections clear of short circuits, 
 as the total hiph voltajre will cause a heavy current to flow and ruin the bat- 
 tery very (|Uickly if cnnnectcnl to a circuit of low resistan<-c. 
 
 ®_Q_®[ 
 
 Q®i y 
 
 o <S>| 
 
 SECTION 
 
 Rg. 4-34.— UATTERY, SERVICE. TESTING. 
 
 (14:Vl
 
 44 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 OHM METER. MODE), llt04. 
 
 Tlieoliiiimoter 1'iiniislml with this case is a <-(iiiipact form of tlio orisinal nioclel 
 olimiueter. The variable resistance is wound on a cylinder so arranjied as to he 
 divided into l.UOO iniuai parts by a horizdutal scab' of 20 (-(lual i)arts and a 
 
 I h Batiery external to instrument 
 
 (^^Q^OJ 
 
 H3 
 
 PERSPECTIVE VIEW 
 
 ?; 
 
 •^ ^ey 
 
 J 
 
 ( Sliding resistance 1 
 
 CIRCUITS OF OHMMETER 
 
 PLAN WITH COVER OPENED 
 
 Fig. 4-35.— OHMMETER, MODEL 1904. 
 
 drum srale of .'0 unit parls. Tlic rcaiiinir oblained from tlic slyliis is arbitrary, 
 jitid referenc*' is lia<l (o Ihc table in tlie <-ov<'i- of tlic iust niiuent lor the actual 
 resistance corresponding to aiiv vi\''n position of Ihc sll.vns. (Sec lijj. 4-85.) 
 'IMic batlcrv kev has a bayonci calcli. 
 
 (144)
 
 Cable and Cable Systems. — Chapter 4. 
 
 45 
 
 CABLE-TKSTINfi TKLKFMIONK. 
 
 This telcphuno was designed in tlic engineering; division, Signal Uilice, fur 
 use of cable testers, and, as will lie noted, is especially arranged for this 
 work. (See figs. 4-36 and 4-37.) 
 
 The home station is provided with lour cells of 4-0 battery, a pony relay, a 
 buzzer, a choke coil, an interrupter, and a hand set. The distant station has a 
 hand .set and a resistance of 500 ohms normally in circuit with it, but this 
 resistance may be cut out by depressing the switch in the handle of tlie set. 
 
 When the home operator wishes to call the distant station he draws out the 
 ring of the interrupter, which causes the distant receiver to rattle. When the 
 distant operator picks up his hand set and closes the switch in the handle, 
 short-circuiting the otK) ohms at the distant telephone, the home relay operates, 
 closing a local buzzer circuit and causing the buzzer to vibrate. When the 
 home operator depresses his switch in tlie hand set, tlie buzzer is cut out of 
 circuit and conversation may take place. The distant hand switch is used for 
 calling only. 
 
 Fig. 4-36.— TELEPHONE. CABLE TESTING. 
 
 Part 
 No. 
 
 Name. 
 
 Reference 
 No. 
 
 Case 
 
 Battery (4 cells of 4-o). 
 
 Pony relay 
 
 Buzzer. 
 
 Choke coil „ 
 
 Intermpter , 
 
 Hand set , home station (switch in handle) 
 
 Hand set, distant station (switch and 500 ohms in handle). 
 Cord for liand set 
 
 (14."))
 
 46 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 METHOD OF MAKING FIRST TEST AFTER INSTALLATION. 
 
 The tester should have two assistants. One should he a man faniiliar with 
 electrical apparatus. The cable tester should proceed to a point from which 
 a number of cables radiate. The more experienced assistant should be sent 
 to distant end of cable. 
 
 Fig. 4-37.— TELEPHONE, CABLE TESTING, CIRCUITS. 
 
 DUTIES OF TESTER. 
 
 The galvanometer should he set up dii solid foundation in such relation to 
 the strongest lif,dit that the .scale is most ilUnninated wliile the mirror is in 
 the shadow. The box containing the insulation and capacity-testing set should 
 l>e placed on a dry foundation. Tiie lOO.OOO ohm box should be wired perma- 
 nently into circuit, to avoid dangerous currents, and should al.so be placed on 
 a dry foundation. 
 
 Ordinarily it is advisable to thoroughly insulate the battery. This may be 
 accomplished by placing a piece of heated glass between battery and support 
 or by susi)ending the battery from ceiling by means of a wire or cord, with a 
 luniiber of iioi-ci'lain knobs connected in each hanger in such a manner that the 
 <'ord or wire is not in one continuous ])ie<'e. A torch may be ai)pli(Hl occa- 
 sionally to tlie.se porcelain knobs in order to disperse the slightest tilm of 
 moisture that nuiy collect. 
 
 While the tester is setting up (he instrumenl.s, his assistant should get the 
 cable ready for test. The assistant at the distant end of the cable should have 
 been instructed to clear the ends of all conductors, .scraping them carefully and 
 taking care to keep them dry and clear of each other and ground, while the 
 test of insulation and electrostiitic capacity is in i)rogress. In some instances 
 It is necessary to apiily the Ilame of n small alcohol torch to the ends of the 
 
 (146)
 
 Cable and Cable Systems. — Chapter 4. 47 
 
 conductors in onlt-r to dissiimt*' :ill niDisiiirt'. IT lliis is rcsortcij In, ^iicit <iiro 
 siiould Ih' takfn to avoid <»\i'rlieatin;; tlu' insuialioii, as it will n'sull in sliow- 
 iiiK coniimratively heavy iealva«e. A ;,'asolint' llanic, or any llainc wliicli will 
 smoke the ends of conductors, sliould not l)e used. 
 
 The testinfc telepiione may t>e used in connection wilii identiliiation of con- 
 ductors on h>nK caldes, especially those havinj; rubber insulation or whenever 
 connnunication between tester and his assistant at opposite em! of the cable is 
 desired. 
 
 In testing short subterranean cables a satisfactory substitute for this tele- 
 piione for the purjiose mentioned above is two Coast Artillery type head sets, one 
 of these head sets to be used at each end of tlie cable. To use these head sets as 
 a telephone, tie back out of the way the common wire (black) of each head set, 
 as this wire is not used. Connect either of the two renuiining wires (red 
 and yellow) of one of the head sets to cable sheath in series with two cells of 
 dry batteries, the other wire to he attached to conductor over which it is desired 
 to conmmnicate. The other head .set at opposite end of cable is conne<'ted 
 similarly, except that the cells of dry battery are onntted. 
 
 Identification of conductors can very quickly be made by this means, as it is 
 only necessary for tester to connect one wire of his head set to a conductor 
 of cable anil assistant at other end to slide one wire of his head set over 
 conductors. When the conductor selected by tester is touched, the assistant 
 receives a loud click in the receiver of his head set. He immediately touches 
 the wire again and responds with " Hello " in the mouthpiece of the transmitter. 
 The tester assigns a number to the conductor used. Immediately following 
 this procedure the tester disconnects wire of head set from cable conductor 
 and connects it to another conductor. The operation is repeated until numbers 
 have been assigned all conductors of the cable being tested. 
 
 A check test should then be made. This can be very (juickly accomplished, 
 as it should not be necessary to hunt for conductors. 
 
 Having identified all conductors, the tester instructs the distant assistant 
 to see that all wires are clear, except one used for the telephone, and then to 
 report. When all are reported clear, the assistant may be instructed to stand 
 by and await orders; under no conditions to tou<b the cleared wires uidess told 
 to do so. 
 
 INSULATION MEASUREMENTS. 
 
 THE author's explanation OF PRINCIPLE INVOLVED IN MAKING INSI-L.\TION 
 RESISTANCE MEASITtEMENTS. 
 
 The method employed is a comparison of insulation resistance value of cable 
 with a known resistance. In order to make this comparison it is necessary to 
 know the number of divisions dellection on galvanometer scale that will be 
 obtained when a current of uniform strength is caused to flow through the 
 known resistance and the galvanometer coil in series. It must be rememberetl 
 that the detlection of galvanonu'ter arnuiture is dependent uiH»n the strength of 
 current that is tlowing through its coil <ir winding and that strength of dire<;t 
 current in any circuit is dei>endent on E. M. F. and resistance of circuit. 
 
 When the miml)er of divisions dellection through a known resistance is known, 
 it is merely necessary to compare the divisioiLs detU'ction obtained through an 
 unknown resistance with the former to determine value of unknown resistance. 
 Exami)le: If a .scale dellection of 10 tlivisions is obtained through 1 ohm and a 
 deflectiiUi of 2 divisions is obtaintMl through insulation of cable, what is insula- 
 tion resistance of cable? Ten divisions dividtnl by li divisions «Miuals ."i. there- 
 fore only one-tifth as many tlivisions detlei-tiou is obtaine<l through the insula- 
 tion of the cable as that obtained through 1 ohiiL conse<iuently the insulation 
 
 (147)
 
 48 Signal Corps Manual No. 3. — Chapter 4. 
 
 resistance of cable must be tive times 1 ohm, oi* 5 ohms. Now, assume this cable 
 to be 2 miles long and it is desired to determine the insulation per mile of such 
 a cable. If sufficient current can escape through 2 miles of the insuhition to 
 establish a value of 5 ohms insulation resistance. 1 mile of such insulation would 
 allow only sufficient current through it to show two times as high a resistance, 
 or 5 ohmsX2=10 ohms, the insulation resistance of such cable per mile. 
 
 While the foregoing clearly demonstrates the principle involved in computing 
 insulation measurements, the values usually encountered are very much higher. 
 For instance, the Signal Corps specifications require certain cable to have an 
 insulation resistance of at least 1.400 megohms per mile. One megohm equals 
 1.000.000 ohms. The reader can readily understand that in measuring such 
 values it will be advantageous to know the divisions deflection through a much 
 higher resistance than 1 ohm, consequently the standard used is 100,000 ohms, 
 or Tts megohm. In measuring high insulation values a battery of high voltage 
 must be used, as with exceedingly high insulation resistance a deflection of 
 one division on the galvanometer scale will not be obtained unless high E. M. F. 
 is used, for it must be remembered that divisions deflection is dependent upon 
 current strength, and, according to Ohm's law, current strength equals electro- 
 motive force divided by resistance in ohms. 
 
 Assume that a deflection of 10 scale divisions was obtained in measuring 
 the insulation of a cable, that the insulation value was 1,000 megohms, and that 
 the known resistance was ttj megohm ; referring to the first example quoted in 
 the foregoing and working backward, we will find that the divisions deflection 
 obtained when the known resistance was measured was 100,000 divisions. 
 
 It is impracticable to construct galvanometers with such a range, consequently 
 an instrument termed a shunt is used, and by its means only a known fraction 
 of the current in the circuit is passed through the galvanometer. These shunts 
 are usually made so the fraction can l)e changed at will and any one of the 
 following fractions of cun-ent passed through galvanometer, A, rh^j -nrinr) iTraTJ^- 
 As previously stated, the divisions deflection are directly proportional to current 
 .strength, therefore if 10 divisions are obtained when ^ shunt is used the true 
 deflection is ten times as great, or 100. 
 
 Let us now refer to the last example and assume that in measuring through 
 the known resistance {^ megohm) the xrnrff shunt was used. If the true 
 deflection was 100.000 divisions the deflection obtained using the j^uis sbunt was 
 one one-thousandth of the true deflection or 100,000 divided by 1.000 equals 
 100 divisions (a fair scale reading). 
 
 In observing the reading on known resistance, where the lowest fractional 
 proportion of the shunt will not restrict the reading to the scale of the galva- 
 nometer wlien using the battery to be employed in taking the reading on insula- 
 tion of cable, it is necessary to reduce the voltage of the battery and again in- 
 crea.se it when reading is made on insulation of cable. 
 
 V, 
 
 Again referring to Olini's l:i\\ 1 tlH-rcforc the current flow is also directly 
 
 proportional to llic voltage imi)ress('(l on the circuit. If a voltage of 10 volts 
 is used in obtaining dclU-clion with known resistance and 100 volts is used in 
 obtaining deflection wilh insulation of cable, the true detleclion on the known 
 resistance will be ten times the one obfaiiieti, as the voltiige of the latter is ten 
 times as great. HMius it will l»e seen that in measuring high insulation re- 
 sistance the divisions dellection through insulation are observed with full value 
 of liattery and witii galvanometer unshunted so tii.if I'nll strength of current 
 flows through galvanometer armature winding; it will also be observed that 
 in obtaining divisions dellection tliioii-li .-i Unown resistance llie galvanometer 
 
 (H8) 
 
 I 
 
 I
 
 Cable and Cable Systems.-^Chapter 4. 
 
 49 
 
 is shunted or hattory vollaf^o reduccHl. ny hudi, and that tlierefore it is nect^s- 
 sary to coniputc in oidci- to ohtain the true deflection that would obtain were 
 ronditions similar lo lliose wlien deflection throujrh insuhition resistance is 
 ((bserved. 
 
 The operation of findiii;; the scale divisions deflection throufih a known re- 
 sistance is termed " r>etermining the s:ilvanonieter constant." This constant 
 is expressed in the numljer of mejrohms that would l)e in the circuit when a 
 true deflection of one scale division is obtained or number of true scale divisions 
 deflection that would be obtained in measuring through 1 megolim i-esistance. 
 
 Com b'ne d Shu n land Key 
 
 \D,suinten<3 of cable CorauUor-p&>c,i!e^-fjrU:LC ' 
 Fig. 4-38.— CABLE TESTING, GALVANOMETER CONSTANT. 
 
 The sensibility of a galvanometer is expressed in meghonis. It is the number 
 of megohms required in the circuit to give a reading of one scale division 
 using a battery voltage of 1 volt. Example: Using battery of 100 Y, ^^If,^ 
 shunt and t^ megohm as known resistance, a deflection of 30 divisions is ob- 
 tained, what is sensibility of galvanometer? 
 (d)=Divisions deflection, 
 (s) =^Iultiplying jiower of shunt. 
 (v)= Voltage. 
 (kr)^Knovvn resistance in megohms. 
 
 rrX s X kr X (l=me<j;olim.s sen.'^ibilify (or di^i.^ion? deflection through 1 megohm) 
 8ub.stituting the above values: 
 
 jqqX 10000 XjqX30=.SOO divi.sinn.>^ through I megohm at 1 volt. This is equiv- 
 alent to 1 division through ;i00 megohms at 1 volt. Therefore the sensibility of gal- 
 vanometer is 300 megohms. 
 
 (149)
 
 50 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 COUKECTION KOI! l.KADS. 
 
 Oil iirt'pjiriiij,' Tor readings of insulation. (•ai)acit.v, and copjior n'sistanfe, 
 readin;,'s .sliould 1)0 taken for each of these value.s on the leads and recorded 
 for correction of the respective test readin&s. 
 
 TO DETERMINE THE GALVANOMETER CONSTANT. 
 
 The tester proceeds to get his s:^lvanometer constant for insulation, as 
 follows : 
 
 With connections as shown in figure 4-8S, he moves the sluint to 0.0001 
 and depresses the battery key on sluint. The constant is then determined 
 by dividing the resulting deflection by the shunt value and then dividing l)y 10, 
 the standard resistance box being only 100,000 ohms insteiid of 1 megohm. 
 This gives the deflection which the battery used would cause through 1 megohm 
 without shunt. 
 
 ^. 
 
 Combine d Shu nt and Key 
 
 ,^^^M^^ 
 
 *- }9 Qqq,aQ. 
 
 Seri'ice TestJng Battery 
 
 C>:.tanL end oFcoble Conaudor ■pencilled' for fci t 
 
 
 Fi(?. 4-39.— CABLE TESTING, INSULATION. 
 
 It is most important to us(> the same battery voltage in testing fts in deter- 
 mining the constant, or make due allowance for change of voltage in com- 
 puting test results. For insulation tests it is customary to utilize a voltage 
 of ai)i)roximat('l,\ ion. 
 
 INSULATION TEST. 
 
 Connections ww llim made as shown in figure 4-.^0. Tliis comiection puts 
 till' galvanomeltT :iiid hallcry in scries. Ihrough the shunt and 100.000-ohiu 
 ito\, Willi llif conductor, its insulation throughout its whole lenglh and ground. 
 All I he (itlicr (■undiict(»rs of the cable sh(»uld also be connected to ground. The 
 test is liierefore against all the other conductors ;ind ground, tlius de(«'rmining 
 tlie existence of crosses between conductors as well as insulation t«i gn»und. 
 
 (ir.O)
 
 Cable and Cable Systems. — Chapter 4. 
 
 51 
 
 Havin;,' roiiiit'itcil tlius t<i Nd. 1 cumliictor, (lie slmiit is set at O.fKM)! ami the 
 battery Imtton dcinH'ssed. Willi niiilier cables an electrification of one minute 
 is desirable. In paper cal)le the electrification is practically instantaneous, and 
 the slnmt may be moved to j;radually smaller values until a readable deflection 
 Is obtained. The deflection, shunt, and conductor numbr-r are then entered in 
 a notebook, and if the readin;? is nonnal (lie <ntidii<li>r is rci)hiced in the biMMJi 
 and the next one is tested. 
 
 On comparatively short caltles where exact i'eadiMj,'s are impracticable .'{o 
 seconds' electrification is suflicient. 
 
 Should trouble be found, the assistant shoubl be called and asked to scrape 
 the insulation of the conductor in question carefully and see that it is free. 
 Havins identified all wires, it is a simple matter to te.st the telephone wire by 
 substituting for the telephone line one of the wires fir.st tested. 
 
 Dtatont c/jrf of Cjb' 
 
 Fig. 4-40.— CABLE TESTING, CAPACITY. 
 
 The followiii;: exami)le is submitted to indicate the method of calculating 
 the insulation resistance of a cable. 
 
 Suppose our deflection Ihroujrh ]()O,(H»0 ohms, using O.lMMll shmit, to be S() 
 divisions, then the constant equals SO divided by O.tKX)! and multiplied by 
 one-tenth. Constant tHpials 80,000. 
 
 Suppose our detlection on conductor No. 1 is 40, with a shunt value of 1 : 
 then, since the constant is the deflection through 1 megohm, the number of 
 megohms represented by this deUection will be S0,(MK1 divided by 4U, or •J.fKKl 
 megohms. 
 
 If the cable -were IJ miles long, to reduce this value to megohms i>er mile 
 it would be necessary to multiply it by li, and the insulation resistance iwr 
 mile would be 3,000 megohms, an average value for paper-insulation cables 
 not including pot heads under usual weather conditions. 
 
 Tlie conductors of all completed cables of systems using new <-able should 
 show an insulation resistance of at least .100 megohms per mile. The con- 
 ductors of all completed cables of systems using re<'overe<l cable should sliow 
 an insulation resistance of at least 3(M1 megohms i»er mile.
 
 52 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 CAPACITY TEST. 
 
 Having obtained tlie insulation resistance of all the conductors, the battery 
 is disconnected, the 100,000-ohm box is set aside, and the condenser set is con- 
 nected as shown in figure 4—40. The condenser set is held in the hand or may 
 be placed on table. If the latter is resorted to, the condenser should be placed 
 between cleats fastened to table in order that switch of set may be positively 
 and quickly operated. Suitable battery (not more than 5 or 10 cells) is con- 
 nected to the condenser. The deflection on the standard condenser is then 
 compared with the deflection caused by the cable, using the same battery and 
 shunt value. 
 
 The following example shows the method of calculating capacity : 
 
 Suppose the deflection through the standard condenser were 150 and the leads 
 were negligible. 
 
 Suppo.se our deflection througli the cal)le wore 4.1(1. 
 
 w w 
 
 Fig. 4-41.— OHMMETER, THEORY, • ' 
 
 Tlie cajjacity of (lie (■■,\\)\r would then be 4r)0 divided by 1.10, or 8 times the 
 capacity of standard (one-third M. F.). The cable capacity therefore would 
 lie 1 microfarad. 
 
 If the cable were 2 miles long, its capacity per mile would be 1 divided by 
 2, or O.n microfarads, a little above the average for rubber cable. 
 
 OHMMKTEli, MODKI, 1!»04. 
 
 The Iheoretical diagram of the olinMiicIci-. model 1004, is given in figure 4-41, 
 ill uliicb the i)arts of the conventional form of llie Wheatstone bridge are 
 iilipiirent. The ,1 and /{, or " bii lance arms," are the two jiiirts of the bridge 
 wire W W into which it is divided by the " toucher." 
 
 The two standard resistiince coils 1(( mikI 100 ohms, respectively, correspond 
 to the R arm of the bridge, .V (the uid<n<»wii resistance) forming the other arm. 
 Tli(! telephone receiver may tMke the pliice of the gidvanometiT, balance 
 
 (tr.2)
 
 Cable and Cable Systems. — Chapter 4. 
 
 53 
 
 lioiii;,' indicalcd by tlic ci'ssiition of tlic clicks jiiid fryiii;: soiiml wlieii tlie 
 loiulior liiis reuclied the proper graduation on the bridge wire. 
 
 niKECTIONS FOK USING THP: OIIMMKTKU, MODKI. I'.HIl. 
 
 Connect a battery. |)referaltly a couple of dry cells external Id the testing 
 set, to posts marked ■" I'.al." and the niikiinwn resistance to jiosts A'l. A'-. If the 
 
 Sliding fi£,si stance 
 
 mmmmmm^ 
 
 Distant end of cable 
 Fig. 4-42.— OHM METER, RESISTANCE MEASUREMENT. 
 
 resistance is small, insert the plug at 10 and if large at 100. Depress the 
 key and operate catch ; then draw the stylus liyhtly across the horizontal scale, 
 touching tlie convolutions of wire until the galvanometer reverses its deflection. 
 
 Multiples of .50 are read on the horizontal scale and fractions of a turn on 
 the drum at the right. The tabular number corresponding to this number, as 
 found in the table on the lid of the olunmeter, when nudtiplied by 10 or 1(M». 
 depending on whether tlie plug is at 10 or KM), will give the correct resistance. 
 
 For example, if the balance is found between convolutions Nos. 150 and 
 200 on the horizontal scale and the drum scale reads 46, the exact reading is 
 196. Referring to the table, the number corresponding to this is 0.2438, and 
 the resistance, if the plug is inserted at 10, will be 2.438 ohms; or, if the plug 
 is inserted at 100, will be 24.38 ohms. 
 
 (153)
 
 54 Signal Corps Manual No. 3. — Chapter 4. 
 
 A telephone receiver may be used in place of the galvanometer in the ohm- 
 meter by disconnecting one of the cords from the post marked " Tel." and 
 connecting the receiver to those posts. 
 
 The portable galvanometer may be used in the place of the galvanometer 
 in the ohmmeter by proceeding as for the receiver. In this case it would be 
 advisable, however, to make use of the galvanometer with shunt. 
 
 The method of measuring conductor resistance of a cable is shown in figure 
 4-42. The copper resistance is tested in pairs and should not vary to any 
 great extent (in very large cables the outer layers will be a few per cent 
 higher in resistance than the inner layers). The resistance per stretch is 
 ordinarily determined by dividing the loop reading by 2. The resistance per 
 mile is determined by dividing the total resistance per stretch by the number 
 of miles in the stretch. 
 
 Methods of testing to locate faults in cables are described in detail, chapter 9. 
 
 POINTS FOK THE TESTER. 
 
 1. Never open a paper cable on a damp, misty, or rainy day, whether under 
 cover or not. 
 
 2. Never pronounce a cable bad until you are satisfied that all ends are 
 absolutely clear and dry. 
 
 3. Never test any kind of cable on a damp day if it can be avoided. 
 
 4. Use the service-testing battery for insulation only, thus saving it against 
 possible short circuit or heavy drain. 
 
 5. Get thoroughly acquainted with the instruments before starting the test 
 and mark all the adjustments, so that little time need be wasted in setting up. 
 
 6. Remember that accurate readings never are possible under moist con- 
 ditions, and instruments and leads should be as dry as practicable. 
 
 7. The micrometer caliper should be used to determine exact diameter of 
 the conductor. 
 
 8. All data concerning the cable should be recorded before taking down the 
 instruments, luMug sure that data is complete for each conductor. 
 
 The following tables contain data wliich may be of value to the tester: 
 
 (1R4)
 
 Cable and Cable Systems. — Chapter 4. 
 Tabic uf dihicnuiona, icciyfit, and Icnijtk of ijurc copijer ivire. 
 
 55 
 
 Size, 
 Brown & 
 Sharpe. 
 
 Diameter, 
 mil.s. 
 
 Circular, 
 mils. (if-). 1 
 mil. =.001 in. 
 
 Pounds 
 
 per 1 ,0(K) 
 
 feet. 
 
 I'ouml.s per 
 mile. 
 
 Feet per 
 pound. 
 
 0000 
 
 460.000 
 
 211600.00 
 
 639.33 
 
 3,375.7 
 
 1.56- 
 
 000 
 
 409.640 
 
 167805.00 
 
 507.01 
 
 2,677.0 
 
 1.97 
 
 00 
 
 364.800 
 
 133079. 40 
 
 402.09 
 
 2,123.0 
 
 2.49 
 
 
 
 324. 860 
 
 10.5538.00 
 
 318.86 
 
 1,683.6 
 
 3.14 
 
 1 
 
 2S9. 300 
 
 83694. 20 
 
 252. 88 
 
 1,335.2 
 
 3.95 
 
 2 
 
 257. 630 
 
 66373.00 
 
 200. 54 
 
 1,058.8 
 
 4.99 
 
 3 
 
 229. 420 
 
 52034. (K) 
 
 1,59. 03 
 
 839.68 
 
 6.29 
 
 4 
 
 204.310 
 
 41742. (K) 
 
 126. 12 
 
 ()05. 91 
 
 ' 7,93 
 
 5 
 
 181. 940 
 
 33102. 00 
 
 100.01 
 
 528. 05 
 
 10.00 
 
 6 
 
 162.020 
 
 262.50. 50 
 
 79. 32 
 
 418.81 
 
 12.61 
 
 7 
 
 144. 280 
 
 20816. 00 
 
 62.90 
 
 332.11 
 
 1,5. 90 
 
 8 
 
 128. 490 
 
 16.509. 00 
 
 49.88 
 
 2t)3. 37 
 
 20. 05 
 
 9 
 
 114.430 
 
 13094.00 
 
 39. .56 
 
 208. 88 
 
 2.5. 28 
 
 10 
 
 101. 890 
 
 10.381.00 
 
 31.37 
 
 16.5. 63 
 
 31.38 
 
 n 
 
 90.742 
 
 8234. 00 
 
 24.88 
 
 131. 37 
 
 40. 20 
 
 12 
 
 80.808 
 
 6529. 90 
 
 19.73 
 
 101. 18 
 
 .50. 69 
 
 13 
 
 71.961 
 
 5178. 40 
 
 1,5. 65 
 
 82. 632 
 
 6:?. 91 
 
 14 
 
 64.048 
 
 410(). 70 
 
 12.44 
 
 65. 674 
 
 80.38 
 
 15 
 
 57.068 
 
 3256. 7 
 
 9.84 
 
 51.956 
 
 101. 63 
 
 16 
 
 50.820 
 
 2582. 9 
 
 7.81 
 
 41.237 
 
 128. 14 
 
 17 
 
 45. 257 
 
 2048. 2 
 
 6.19 
 
 32.683 
 
 161. 59 
 
 18 
 
 40. 303 
 
 1624. 3 
 
 4.91 
 
 2,5.925 
 
 203.76 
 
 11) 
 
 35. 876 
 
 1287. 1 
 
 3. 88 
 
 20. 507 
 
 2.57. 47 
 
 20 
 
 31. 961 
 
 1021.5 
 
 3.09 
 
 16.315 
 
 324.00 
 
 21 
 
 28. 462 
 
 810. 10 
 
 2. 45 
 
 12. 936 
 
 408.56 
 
 22 
 
 25.347 
 
 642.70 
 
 1.94 
 
 10. 243 
 
 515. 15 
 
 23 
 
 22. 571 
 
 509. 45 
 
 1.54 
 
 8.1312 
 
 649.66 
 
 24 
 
 20.100 
 
 404. 01 
 
 1.22 
 
 6.4416 
 
 819. 21 
 
 25 
 
 17.900 
 
 320. 40 
 
 .97 
 
 .5. 1216 
 
 1,032.% 
 
 • 26 
 
 15. 940 
 
 254. 01 
 
 . 77 
 
 4.0656 
 
 1,302.61 
 
 27 
 
 14. 195 
 
 201. 50 
 
 .61 
 
 3. 2208 
 
 1.642. ,55 
 
 28 
 
 12.641 
 
 159. 79 
 
 .48 
 
 2. 5344 
 
 2,071.22 
 
 29 
 
 11.257 
 
 126. 72 
 
 .38 
 
 2.0064 
 
 2.611.82 
 
 30 
 
 10.025 
 
 100.5 
 
 .30 
 
 1. ,5840 
 
 3.293.97 
 
 31 
 
 8.928 
 
 79.71 
 
 .24 
 
 1.2672 
 
 4,152.22 
 
 32 
 
 7.950 
 
 63.20 
 
 .19 
 
 1.0032 
 
 5, 236. 66 
 
 33 
 
 7.080 
 
 50.13 
 
 .15 
 
 .7920 
 
 6,602.71 
 
 34 
 
 6.304 
 
 39.74 
 
 .12 
 
 .6336 
 
 8., 328. 30 
 
 35 
 
 5.614 
 
 31.52 
 
 .10 
 
 . 52,80 
 
 10,501.35 
 
 36 
 
 5.000 
 
 25.00 
 
 .08 
 
 .4224 
 
 13,238.83 
 
 37 
 
 4.453 
 
 19.83 
 
 .06 
 
 .3168 
 
 16,691.06 
 
 3S 
 
 3.965 
 
 15.72 
 
 .05 
 
 .2640 
 
 20.851.65 
 
 39 
 
 3.531 
 
 12.47 
 
 .04 
 
 .2112 
 
 26. ,302. 23 
 
 40 
 
 3.144 
 
 9.89 
 
 .03 
 
 .1584 
 
 33.175.94 
 
 46581°— 17- 
 
 -11 
 
 (155)
 
 56 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 Table of resistances of pure copper wire at 75° F. 
 
 Size, 
 Brown & 
 Sharpe. 
 
 Ohms per 
 1,000 feel. 
 
 Ohms per 
 mile. 
 
 Ohms per pound. 
 
 Feet per ohm. 
 
 0000 
 
 0. 04906 
 
 0. 25903 
 
 0. 000076736 
 
 20, 383. 
 
 000 
 
 .06186 
 
 . 32664 
 
 . 00012039 
 
 16.165.0 
 
 00 
 
 .07801 
 
 .41187 
 
 . 00019423 
 
 12,820.0 
 
 
 
 .09838 
 
 . 51937 
 
 . 00038.500 
 
 10, 166. 
 
 1 
 
 . 12404 
 
 .65490 
 
 . 00048994 
 
 8, 062. 3 
 
 2 
 
 . 15640 
 
 . 82582 
 
 . 00078045 
 
 6, 393. 7 
 
 3 
 
 . 19723 
 
 1.0414 
 
 . 0012406 
 
 5. 070. 2 
 
 4 
 
 .24869 
 
 1.3131 
 
 . 0019721 
 
 4,021.0 
 
 5 
 
 . 31361 
 
 1.6558 
 
 . 0031361 
 
 3,188.7 
 
 6 
 
 . 39546 
 
 2.0881 
 
 . 0049868 
 
 2, 528. 7 
 
 7 
 
 . 49871 
 
 2. 6331 
 
 . 0079294 
 
 2, 005. 2 
 
 8 
 
 . 62881 
 
 3. 3201 
 
 . 012608 
 
 1,590.3 
 
 9 
 
 . 79281 
 
 4. 1860 
 
 . 020042 
 
 1,261.3 
 
 10 
 
 1.0000 
 
 5. 2800 
 
 . 031380 
 
 1.000.0 
 
 11 
 
 1. 2607 
 
 6. 6568 
 
 . 050682 
 
 793. 18 
 
 12 
 
 1. 5898 
 
 8. 3940 
 
 . 080585 
 
 629. 02 
 
 13 
 
 2. 0047 
 
 10. 585 
 
 . 12841 
 
 498. 83 
 
 14 
 
 2. 5278 
 
 13.347 
 
 . 20322 
 
 395. 60 
 
 15 
 
 3.1150 
 
 16. 477 
 
 . 31658 
 
 321.02 
 
 1(> 
 
 4.0191 
 
 21.221 
 
 . 51501 
 
 218.81 
 
 17 
 
 5. 0683 
 
 26. 761 
 
 .81900 
 
 197.30 
 
 18 
 
 6.39U 
 
 33. 745 
 
 1.3023 
 
 !.-)6.47 
 
 19 
 
 8. 0651 
 
 42. 5S5 
 
 2. 0759 
 
 123. 99 
 
 20 
 
 10. 163 
 
 .53. 658 
 
 3. 2926 
 
 98. 401 
 
 21 
 
 12.815 
 
 67. 660 
 
 5. 2355 
 
 78. 067 
 
 22 
 
 16. 152 
 
 85. 283 
 
 8. 3208 
 
 61.911 
 
 23 
 
 20. 377 
 
 107. 59 
 
 13. 238 
 
 49. 087 
 
 24 
 
 25. 695 
 
 135. 67 
 
 21. 050 
 
 38.918 
 
 25 
 
 32. 400 
 
 171.07 
 
 33. 466 
 
 30. 864 
 
 26 
 
 40. 868 
 
 215. 79 
 
 35. 235 
 
 24. 46^ 
 
 27 
 
 51. 519 
 
 272. 02 
 
 84. 644 
 
 19.410 
 
 28 
 
 64. 966 
 
 343. 02 
 
 134. 56 
 
 15. 393 
 
 29 
 
 81.921 
 
 432. 54 
 
 213.% 
 
 12. 207 
 
 30 
 
 103. 30 
 
 545. 39 
 
 340.25 
 
 9. 6812 
 
 31 
 
 127.27 
 
 671.99 
 
 528. 45 
 
 7. 8573 
 
 32 
 
 164. 26 
 
 867. 27 
 
 860. 33 
 
 6.0880 
 
 33 
 
 207. 08 
 
 1,093.4 
 
 1,367.3 
 
 4. 8290 
 
 34 
 
 261. 23 
 
 1,379.3 
 
 2,17.5.5 
 
 3. 8281 
 
 35 
 
 329. 35 
 
 1,738.9 
 
 3. 468. 5 
 
 3.0363 
 
 36 
 
 415.24 
 
 2, 192. 5 
 
 5, 497. 4 
 
 2. 4082 
 
 37 
 
 523. 76 
 
 2, 765. 5 
 
 8, 742. 1 
 
 1.9093 
 
 38 
 
 660. 37 
 
 3, 486. 7 
 
 13, 772. 
 
 1.5143 
 
 39 
 
 832.48 
 
 4, 395. 5 
 
 21.896. 
 
 1.2012 
 
 40 
 
 1,049.7 
 
 5,542.1 
 
 34, 823. 
 
 .9527 
 
 In roducinjr I lie iiisiilation resi.'^tance of Okoiiito, Hnbirshaw, or Bishop c-oni- 
 pouiids to 60° F., the total (Urt'creiice botwi'i'ii \hv toiniKTature of ob.sorvation 
 and the standjird temperature, 00°, will he deteriuiiied and the proper coeHicient 
 will he found hy referrinj; to the tahle. For example, if the temperature were 
 75°, the difference of temperature, 15°, would call for a coellicient of 1.470, hy 
 which tlie insulation resistance, as calculated, will be multiplied to determine 
 the correct value at 60° F. 
 
 (ir.6)
 
 Cable and Cable Systems. — Chapter 4. 
 
 57 
 
 Temperature of cocfflcicnts for the reduction of insulation resistaiice to 60° F. 
 
 OKONITE, HABIRSHAW, AND BISHOP COMPOUNDS. 
 
 Diflerence 
 
 1 
 
 Diflerence 
 
 
 Difference 
 
 
 of tempera- 
 
 Coellicient. 
 
 of tempera- 
 
 Coeflacient. 
 
 oftempera^ 
 
 Coefficient. 
 
 ture. 
 
 
 ture. 
 
 
 tare. 
 
 
 "F. 
 
 
 'F. 
 
 
 "F. 
 
 
 1 
 
 1.026 
 
 18 
 
 1.587 
 
 35 
 
 2.456 
 
 2 
 
 1.053 
 
 19 
 
 1.629 
 
 36 
 
 2.520 
 
 3 
 
 ^ 1.080 
 
 20 
 
 1.671 
 
 37 
 
 2.586 
 
 4 
 
 1.108 
 
 21 
 
 1.715 
 
 38 
 
 2.653 
 
 5 
 
 1. 137 ! 
 
 22 
 
 1.759 
 
 39 
 
 2.722 
 
 6 
 
 1.167 
 
 23 
 
 1.805 
 
 40 
 
 2.796 
 
 7 
 
 1. 197 
 
 24 
 
 1.852 
 
 41 
 
 2.865 
 
 8 
 
 1.228 I 
 
 25 
 
 1.900 
 
 42 
 
 2.940 
 
 9 
 
 1.260 
 
 26 
 
 1.949 
 
 43 
 
 3.016 
 
 10 
 
 1.293 
 
 27 
 
 2.000 
 
 44 
 
 3.091 
 
 11 
 
 1.326 
 
 ■ 28 
 
 2.0.52 
 
 45 
 
 3.175 
 
 12 
 
 1.361 
 
 29 
 
 2.105 
 
 46 
 
 3. 258 
 
 v^ 
 
 1.396 
 
 30 
 
 2.160 
 
 47 
 
 3.342 
 
 14 
 
 1.433 
 
 31 
 
 2.216 
 
 48 
 
 3.429 
 
 15 
 
 1.470 
 
 32 
 
 2.274 
 
 49 
 
 3.518 
 
 Iti 
 
 1.508 
 
 33 
 
 2.333 
 
 50 
 
 3. 610 
 
 17 
 
 1.547 
 
 34 
 
 2.394 
 
 
 
 To correct insulation resistance for temperature wliere the cables are made 
 up of Safety, Kerite, or Standard underground rul)ber compounds, reference 
 should be made to one of the following tables for the temperature coefficient 
 at the ob.served temperature. The correct resistance is obtained by multiply- 
 ing the calculated resistance by the coefficient found in the table for that 
 compound opposite the observed temperature. 
 
 SAFETY COMPOUND. 
 
 Tempera- 
 ture. 
 
 Coefficient. 
 
 Tempera- 
 ture. 
 
 Coefficient. 
 
 Tempera- 
 ture. 
 
 Coefficient. 
 
 "F. 
 
 
 °F. 
 
 
 "F. 
 
 
 20 
 
 0.4399 
 
 47 
 
 0. 7386 
 
 74 
 
 1.4407 
 
 21 
 
 .4472 
 
 48 
 
 .7551 
 
 75 
 
 1.4811 
 
 22 
 
 .4.547 
 
 49 
 
 .7721 
 
 76 
 
 l.,5228 
 
 23 
 
 .4625 
 
 50 
 
 .7897 
 
 77 
 
 1.5647 
 
 24 
 
 .4705 
 
 51 
 
 .8078 
 
 78 
 
 1.6110 
 
 25 
 
 .4787 
 
 52 
 
 .8265 
 
 79 
 
 1.6728 
 
 26 
 
 . 4869 
 
 53 
 
 .8458 
 
 80 
 
 1. 7056 
 
 27 
 
 .4959 
 
 54 
 
 .8658 
 
 81 
 
 1. 7556 
 
 28 
 
 .5049 
 
 55 
 
 .8864 
 
 82 
 
 1.8073 
 
 29 
 
 .5141 
 
 56 
 
 .9076 
 
 83 
 
 1.8610 
 
 30 
 
 ..5237 
 
 57 
 
 .9296 
 
 84 
 
 1.9167 
 
 31 
 
 .5335 
 
 58 
 
 .9523 
 
 85 
 
 1.9744 
 
 32 
 
 . .5437 
 
 59 
 
 . 9758 
 
 86 
 
 2. 0343 
 
 33 
 
 ..5542 
 
 60 
 
 1.0000 
 
 87 
 
 2.0964 
 
 34 
 
 .5648 
 
 61 
 
 1.0251 
 
 88 
 
 2.1609 
 
 35 
 
 .5759 
 
 62 
 
 1.0,510 
 
 89 
 
 2.2278 
 
 36 
 
 ..5873 
 
 63 
 
 1.0777 
 
 90 
 
 2. 2973 
 
 37 
 
 .5990 
 
 64 
 
 1.1054 
 
 91 
 
 2.3694 
 
 38 
 
 .0112 
 
 65 
 
 1. 1340 
 
 92 
 
 2.4443 
 
 39 
 
 .6236 
 
 66 
 
 1.1036 
 
 93 
 
 2.5223 
 
 40 
 
 .0351 
 
 67 
 
 1.1943 
 
 94 
 
 2.6028 
 
 41 
 
 .6498 
 
 68 
 
 1.2260 
 
 95 
 
 2.6808 
 
 42 
 
 .6635 
 
 69 
 
 1.2587 
 
 96 
 
 2. 7740 
 
 43 
 
 . 6776 
 
 70 
 
 1.2927 
 
 97 
 
 2.8646 
 
 44 
 
 .6921 
 
 71 
 
 1. 3278 
 
 98 
 
 2.9587 
 
 45 
 
 .7071 
 
 72 
 
 1..3641 
 
 99 
 
 3.0566 
 
 46 
 
 .7226 
 
 73 
 
 1.4017 
 
 100 
 
 3.1584 
 
 (157)
 
 58 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 Temperature of coefficients for the reduction of insulation resistance to 60° F. 
 
 Continued. 
 
 KERITE COMPOUND. 
 
 Temper- 
 ature. 
 
 Coefficient. 
 
 Temper- 
 ature. 
 
 Coefficient. 
 
 Temper- 
 ature. 
 
 Coefficient. 
 
 ° F. 
 
 
 ° F. 
 
 
 ° F. 
 
 
 20 
 
 0. 2706 
 
 47 
 
 0.5187 
 
 74 
 
 2.6023 
 
 21 
 
 .2725 
 
 48 
 
 .5413 
 
 75 
 
 2.8410 
 
 22 
 
 .2747 
 
 49 
 
 .5655 
 
 76 
 
 3.0469 
 
 23 
 
 .2774 
 
 50 
 
 .5917 
 
 77 
 
 3.3035 
 
 24 
 
 .2804 
 
 51 
 
 .6199 
 
 78 
 
 3. 5865 
 
 25 
 
 .2839 
 
 52 
 
 .6503 
 
 79 
 
 3. 8988 
 
 26 
 
 .2877 
 
 53 
 
 . 6831 
 
 80 
 
 4.2438 
 
 27 
 
 .2921 
 
 54 
 
 . 7184 
 
 81 
 
 4.6256 
 
 28 
 
 . 2968 
 
 55 
 
 .7566 
 
 82 
 
 5. 0483 
 
 29 
 
 .3020 
 
 56 
 
 .7979 
 
 83 
 
 5. 5169 
 
 30 
 
 .3078 
 
 57 
 
 . 8426 
 
 84 
 
 6. 0371 
 
 31 
 
 .3141 
 
 58 
 
 .8909 
 
 85 
 
 6.6149 
 
 32 
 
 .3209 
 
 59 
 
 .9433 
 
 86 
 
 7. 2577 
 
 33 
 
 .32,S3 
 
 60 
 
 1.0(K)0 
 
 87 
 
 7.9734 
 
 34 
 
 .3363 
 
 61 
 
 1.0616 
 
 88 
 
 8. 7713 
 
 35 
 
 .3449 
 
 62 
 
 1.1281 
 
 89 
 
 9.6617 
 
 36 
 
 . 3543 
 
 63 
 
 1.2010 
 
 90 
 
 10. 6566 
 
 37 
 
 .3644 
 
 64 
 
 1.2S0() 
 
 91 
 
 11.7695 
 
 38 
 
 . 3752 • 
 
 65 
 
 1.3660 
 
 92 
 
 13.01.58 
 
 39 
 
 . 3869 
 
 66 
 
 1.4597 
 
 93 
 
 14.4130 
 
 40 
 
 .3995 
 
 67 
 
 1..5618 
 
 94 
 
 15.9814 
 
 41 
 
 .4131 
 
 68 
 
 1.6772 
 
 95 
 
 17. 7438 
 
 42 
 
 .4276 
 
 69 
 
 1.7952 
 
 96 
 
 19. 7265 
 
 43 
 
 . 44.33 
 
 70 
 
 1.9285 
 
 97 
 
 21. 9598 
 
 44 
 
 .4601 
 
 71 
 
 2.0744 
 
 98 
 
 24. 4782 
 
 45 
 
 .4782 
 
 72 
 
 2. 2343 
 
 99 
 
 27.3215 
 
 46 
 
 .4977 
 
 73 
 
 2. 4097 
 
 100 
 
 30.5353 
 
 STANDARD UNDERGROUND CO.'S RUBBER "D.' 
 
 Temper- 
 ature. 
 
 Coefficient. 
 
 Temper- 
 ature. 
 
 Coefficient . 
 
 Temper- 
 ature. 
 
 Coefficient. 
 
 ° F. 
 
 
 ° F. 
 
 
 ° F. 
 
 
 20 
 
 0. 5536 
 
 47 
 
 0.8051 
 
 74 
 
 1.2970 
 
 21 
 
 . 5603 
 
 48 
 
 .8179 
 
 75 
 
 1.3227 
 
 22 
 
 . .5672 
 
 49 
 
 . 8311 
 
 76 
 
 1.3491 
 
 23 
 
 .5742 
 
 ,50 
 
 .8446 
 
 77 
 
 1.3762 
 
 24 
 
 .5814 
 
 51 
 
 . .'v5S4 
 
 78 
 
 1.4041 
 
 25 
 
 . 5888 
 
 52 
 
 .8726 
 
 79 
 
 1 . 432.S 
 
 26 
 
 . .5964 
 
 .53 
 
 .8872 
 
 80 
 
 1.4622 
 
 27 
 
 . 6041 
 
 54 
 
 .9021 
 
 81 
 
 1.4924 
 
 28 
 
 .6120 
 
 55 
 
 .9174 
 
 82 
 
 1..5235 
 
 29 
 
 .6201 
 
 56 
 
 .9.331 
 
 83 
 
 1.. 5.5.54 
 
 30 
 
 . 6284 
 
 57 
 
 . 9492 
 
 84 
 
 1 . 5SK3 
 
 31 
 
 . 6369 
 
 5X 
 
 . 9()57 
 
 .85 
 
 1 . 6220 
 
 32 
 
 . 64.56 
 
 ,59 
 
 . 9S26 
 
 .Sti 
 
 1 . 6568 
 
 33 
 
 . 6,54() 
 
 60 
 
 I.IXHX) 
 
 .S7 
 
 1.6!t24 
 
 34 
 
 . 6626 
 
 61 
 
 I.()I7.S 
 
 8K 
 
 1.7291 
 
 35 
 
 .6731 
 
 62 
 
 1.0.%1 
 
 .S!l 
 
 l.76t;!i 
 
 36 
 
 .6827 
 
 63 
 
 1.0549 
 
 90 
 
 1.S0.57 
 
 37 
 
 . 6925 
 
 64 
 
 1.0741 
 
 91 
 
 1.84.57 
 
 38 
 
 . 7026 
 
 6.5 
 
 1 . 093!) 
 
 92 
 
 1 . SS67 
 
 39 
 
 .7129 
 
 66 
 
 1.1141 
 
 93 
 
 1 . 9290 
 
 40 
 
 . 7234 
 
 (u 
 
 1.1.349 
 
 94 
 
 1.9725 
 
 41 
 
 . 7343 
 
 68 
 
 1.1.563 
 
 !»5 
 
 2.0173 
 
 42 
 
 . 7454 
 
 69 
 
 1 . 1 782 
 
 9() 
 
 2. 06:i:t 
 
 43 
 
 .7,567 
 
 70 
 
 1 . 2(K)7 
 
 97 
 
 2. 1107 
 
 44 
 
 .7684 
 
 71 
 
 1.22.3il 
 
 9S 
 
 2.1.595 
 
 45 
 
 . 7803 
 
 72 
 
 1.2476 
 
 !t9 
 
 2. 20!)8 
 
 46 
 
 . 7925 
 
 73 
 
 1.2720 
 
 1(K) 
 
 2. 2615 
 
 (158)
 
 Cable and Cable Systems. — Chapter 4. 
 
 .59 
 
 The re.sistance of copper incroasos witli tlic increase of temperature. In order 
 to reduce copper resistances at any temperature between 0° and 120° V. to W 
 F., tlie followinji table has been calculated, in which 6 is the factor by which 
 the resistance at the observed teni])t'rature should he multiplied to reduce it 
 to 60° F. : 
 
 Reduction of copijcr rcftixtfnirc to (;0° F. 
 
 Temper- 
 
 5 
 
 Temper- 
 
 S 
 
 Temper- 
 
 J 
 
 ature. 
 
 
 ature. 
 
 
 ature. 
 
 
 " F. 
 
 
 ° F. 
 
 
 " J^. 
 
 
 
 
 1. l.iSS 
 
 41 
 
 1.0443 
 
 82 
 
 0.9,529 
 
 1 
 
 1. 1,509 
 
 42 
 
 1. 0419 
 
 83 
 
 . 9.508 
 
 2 
 
 1.1480 
 
 43 
 
 1. 0395 
 
 84 
 
 .9488 
 
 ■i 
 
 1. 14,51 
 
 44 
 
 1. 0371 
 
 85 
 
 .9468 
 
 4 
 
 1. 1422 
 
 45 
 
 1. 0347 
 
 86 
 
 .9448 
 
 o 
 
 1. 1393 
 
 46 
 
 1. 0323 
 
 87 
 
 .9428 
 
 C 
 
 1. 1364 
 
 47 
 
 1. 0300 
 
 88 
 
 .9408 
 
 7 
 
 1. 1336 
 
 48 
 
 1. 0276 
 
 89 
 
 .9388 
 
 8 
 
 1. 1308 
 
 49 
 
 1. 0252 
 
 90 
 
 .9368 
 
 9 
 
 1. 1280 
 
 ,50 
 
 1.0229 
 
 91 
 
 .9348 
 
 10 
 
 1. 12,52 
 
 51 
 
 1.0206 
 
 92 
 
 .9328 
 
 11 
 
 1. 1224 
 
 52 
 
 1. 0182 
 
 93 
 
 . 9308 
 
 12 
 
 1.1196 
 
 .53 
 
 1. 0159 
 
 94 
 
 .9288 
 
 13 
 
 1.1168 
 
 .54 
 
 1. 0136 
 
 95 
 
 .9269 
 
 14 
 
 1.1141 
 
 55 
 
 1.0113 
 
 96 
 
 . 92.50 
 
 l-> 
 
 1.1113 
 
 56 
 
 1.0090 
 
 97 
 
 .92:J1 
 
 16 
 
 1.11)86 
 
 57 
 
 1.0068 
 
 98 
 
 .9211 
 
 17 
 
 1. 1U.59 
 
 58 
 
 1.0045 
 
 99 
 
 . 9192 
 
 18 
 
 1. 1032 
 
 ,59 
 
 1.0023 
 
 100 
 
 . 9173 
 
 19 
 
 1. 100,5 
 
 60 
 
 1.0000 
 
 101 
 
 .91,54 
 
 20 
 
 1.0978 
 
 61 
 
 .9978 
 
 102 
 
 . 9135 
 
 21 
 
 1. 09,52 
 
 62 
 
 . 99,56 
 
 103 
 
 .9116 
 
 22 
 
 1. 0925 
 
 63 
 
 .9933 
 
 104 
 
 .9097 
 
 23 
 
 1. 0899 
 
 64 
 
 .9911 
 
 105 
 
 .9097 
 
 24 
 
 1. 0S73 
 
 65 
 
 .9889 
 
 106 
 
 .9060 
 
 2,5 
 
 1. 0846 
 
 66 
 
 .9867 
 
 107 
 
 .9041 
 
 26 
 
 1. 0820 
 
 67 
 
 .9846 
 
 108 
 
 .9022 
 
 27 
 
 1. 0794 
 
 68 
 
 .9824 
 
 109 
 
 .9004 
 
 28 
 
 1. 0769 
 
 69 
 
 .9802 
 
 110 
 
 .8986 
 
 29 
 
 1. 0743 
 
 70 
 
 .9781 
 
 111 
 
 .8968 
 
 30 
 
 1.0717 
 
 71 
 
 .9759 
 
 112 
 
 .8949 
 
 31 
 
 1.0692 
 
 72 
 
 .9738 
 
 113 
 
 .8931 
 
 32 
 
 1.0667 
 
 73 
 
 .9717 
 
 114 
 
 .8913 
 
 33 
 
 1.0641 
 
 74 
 
 .9695 
 
 115 
 
 .8895 
 
 34 
 
 1. 0616 
 
 75 
 
 .9674 
 
 116 
 
 .8877 
 
 35 
 
 1. 0,591 
 
 76 
 
 .9653 
 
 117 
 
 .8859 
 
 36 
 
 1. 0,566 
 
 77 
 
 .9632 
 
 118 
 
 .8841 
 
 37 
 
 1. 0,542 
 
 78 
 
 .9611 
 
 119 
 
 .8824 
 
 38 
 
 1. 0517 
 
 79 
 
 . 9.591 
 
 120 
 
 .8806 
 
 39 
 
 1. 0492 
 
 80 
 
 .9570 
 
 
 
 40 
 
 1.0468 
 
 81 
 
 .9549 
 
 
 
 A general formula for reducing copper resistance at any observed tempera- 
 ture (T) to 60° F. is given by the following: 
 
 5= 
 
 1.063 
 
 l+,00225 (T-32) 
 
 (15!»
 
 60 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 Wire table, standard annealed copper. 
 I American wire gauge (B. & S.).] 
 
 
 
 Cross section. 
 
 Ohms per 1,000 feet. 
 
 Gauge 
 No. 
 
 Diameter 
 ill mils. 
 
 
 
 
 
 
 Circular mils. 
 
 Square inches. 
 
 0°C. 
 (=32° F.). 
 
 15° C. 
 (=59° F.). 
 
 20° C. 
 
 (=68° F.). 
 
 0000 
 
 000 
 
 00 
 
 460.0 
 409.6 
 364.8 
 
 211 600. 
 
 167 800. 
 133 100. 
 
 0. 1662 
 .1318 
 .1045 
 
 0.045 14 
 . 056 93 
 .071 78 
 
 0.048 04 
 .060 58 
 . 076 39 
 
 0. 049 01 
 .061 80 
 . 077 93 
 
 
 
 1 
 2 
 
 324.9 
 289.3 
 257.6 
 
 105 500. 
 83 690. 
 66 370. 
 
 .082 89 
 .065 73 
 .052 13 
 
 .090 .'-,2 
 
 .1141 
 
 .1439 
 
 .096 33 
 
 .1215 
 
 .1532 
 
 . 098 27 
 
 .1239 
 
 .1563 
 
 3 
 
 4 
 5 
 
 229.4 
 204.3 
 181.9 
 
 52 640. 
 41 740. 
 33 100. 
 
 .041 34 ' 
 
 .032 78 
 
 . 026 00 ; 
 
 .1815 
 .2288 
 .2886 
 
 .1931 
 . 2436 
 .3071 
 
 .1970 
 .2485 
 .3133 
 
 6 
 
 7 
 8 
 
 162.0 
 144.3 
 128.5 
 
 26 250. 
 20 820. 
 16 510. 
 
 .020 62 
 . 016 35 
 .012 97 
 
 .3639 
 .4589 
 .5786 
 
 .3872 
 .4883 
 .6158 
 
 .3951 
 . 4982 
 .6282 
 
 9 
 10 
 11 
 
 114.4 
 101.9 
 90.74 
 
 13 090. 
 
 10 380. 
 
 8234. 
 
 . 010 28 
 .008 WS 
 . 006 467 
 
 .7296 
 .9200 
 1.160 
 
 .7765 
 .9792 
 1.235 
 
 .7921 
 .9989 
 1.260 
 
 12 
 13 
 
 14 
 
 80.81 
 71.96 
 64.08 
 
 6530. 
 5178. 
 4107. 
 
 .005 129 
 .004 067 
 .003 225 
 
 1.463 
 1.845 
 2.326 
 
 1.557 
 1.96:} 
 2. 475 
 
 1.588 
 2.003 
 2.525 
 
 15 
 16 
 17 
 
 57.07 
 50.82 
 45.26 
 
 3257. 
 2583. 
 2048. 
 
 . 002 558 
 . 002 028 
 .001 609 
 
 2.933 
 3. 699 
 4.664 
 
 3.121 
 3.936 
 4.963 
 
 3.184 
 4.015 
 5.064 
 
 18 
 19 
 20 
 
 40.30 
 35. 89 
 31.96 
 
 1624. 
 
 1288. 
 1022. 
 
 .001 276 
 .001 012 
 . 000 802 3 
 
 5.881 
 7.416 
 9.352 
 
 6.259« 
 7.892 
 9.953 
 
 C.385 
 8.051 
 10.15 
 
 21 
 22 
 23 
 
 28.46 
 25.35 
 22. 5/ 
 
 810.1 
 642.4 
 509.5 
 
 . 000 636 3 
 . 000 504 6 
 . 000 400 2 
 
 11.79 
 14.87 
 18.75 
 
 12.55 
 15.82 
 19. 95 
 
 12.80 
 16.14 
 20.36 
 
 24 
 25 
 26 
 
 20.10 
 17.90 
 15.94 
 
 404.0 
 320.4 
 254.1 
 
 . 000 317 3 
 .000 251 7 
 . 000 199 6 
 
 23.64 
 29. 81 
 37. ,59 
 
 25.16 
 31. 73 
 40.01 
 
 25.67 
 32. 37 
 40.82 
 
 27 
 28 
 29 
 
 14.20 
 12.64 
 11.26 
 
 201.5 
 159.8 
 126.7 
 
 . 000 158 3 
 . 000 125 5 
 . 000 099 53 
 
 47.40 
 59. 77 
 75.37 
 
 50.45 
 ()3.61 
 80.22 
 
 51.46 
 64.90 
 
 81.84 
 
 30 
 31 
 32 
 
 10.03 
 
 8.928 
 7. 950 
 
 100.5 
 79.70 
 63.21 
 
 . 000 078 94 
 . 000 062 60 
 . 000 049 64 
 
 95.05 
 119.8 
 151.1 
 
 101.2 
 127.6 
 160.8 
 
 103.2 
 130.1 
 164.1 
 
 33 
 34 
 35 
 
 7.080 
 6.305 
 5.615 
 
 50.13 
 39.75 
 31.52 
 
 . 000 039 37 
 .000 031 22 
 . 000 024 76 
 
 190.6 
 240.3 
 303.0 
 
 202.8 
 255.7 
 322. 5 
 
 206.9 
 260. 9 
 329. 
 
 36 
 37 
 38 
 
 5.000 
 4.453 
 3.965 
 
 25.00 
 19.83 
 15.72 
 
 . 000 019 64 
 .000 015 57 
 . 000 012 35 
 
 382.1 
 481.8 
 607. 5 
 
 406.6 
 512. S 
 646.6 
 
 414.8 
 523.1 
 659. 6 
 
 39 
 40 
 
 3.531 
 3.145 
 
 12.47 
 
 9.888 
 
 . 000 009 793 
 .000 007 766 
 
 766. 1 
 966. 1 
 
 815.4 
 1028. 
 
 831. 8 
 1049. 
 
 (160)
 
 Cable and Cable Systems. — Chapter 4. 
 
 Wire table, standard annealed copper — Continued. 
 [American wire gauge (B. & S.).] 
 
 61 
 
 Gauge 
 No. 
 
 Diameter 
 in mils. 
 
 Cross 
 
 section. 
 
 Ohms per 1,000 feet. 
 
 Circular mils. 
 
 Square inches. 
 
 25' C. 
 ( = 77° F.). 
 
 50° C. 
 ( = 122° F.). 
 
 75° C. 
 
 (=167° F.). 
 
 (XX)0 
 (XK) 
 00 
 
 4(iO. 
 409. (1 
 3(14. 8 
 
 211 im. 
 107 800. 
 133 100. 
 
 0.1602 
 .1318 
 .1045 
 
 0. 049 98 
 .Oti3 03 
 .079 47 
 
 0.054 82 
 .069 12 
 .087 16 
 
 0.059 65 
 .075 22 
 .094 8.5 
 
 
 1 
 
 2 
 
 324.9 
 
 289.3 
 257. (i 
 
 105 500. 
 8.3 090. 
 0(i 370. 
 
 . 082 89 
 .005 73 
 .052 13 
 
 .1002 
 .1204 
 .1594 
 
 .1099 
 . 1386 
 .1748 
 
 .1190 
 
 . l.")(l>S 
 .1902 
 
 3 
 4 
 
 5 
 
 229.4 
 204.3 
 181.9 
 
 52 040. 
 41 740. 
 33 100. 
 
 .041 34 
 . 032. 78 
 .026 00 
 
 .2009 
 .2534 
 .3195 
 
 .2204 
 . 2779 
 .3504 
 
 .2398 
 .3024 
 .,3813 
 
 
 7 
 
 8 
 
 1(12. 
 144.3 
 128. 5 
 
 2(; 2,50. 
 20 820. 
 10 510. 
 
 . 020 62 
 .016 35 
 .012 97 
 
 .4029 
 .5080 
 .6406 
 
 .4418 
 . 5572 
 . 7025 
 
 .4808 
 .6004 
 .7645 
 
 9 
 10 
 11 
 
 114.4 
 11)1.9 
 90.74 
 
 13 090. 
 
 10 3,S0. 
 
 8234. 
 
 .010 28 
 .008 155 
 .006 467 
 
 .8078 
 1.019 
 1.284 
 
 .8800 
 1.117 
 1.409 
 
 .9641 
 1.216 
 1. ,5.33 
 
 12 
 13 
 14 
 
 80.81 
 71. 9Ci 
 
 04.08 
 
 5178. 
 4107. 
 
 .005 129 
 . 004 007 
 . 003 225 
 
 1.620 
 2.042 
 2.576 
 
 1.770 
 2.240 
 
 2.824 
 
 1.933 
 
 2.438 
 3.074 
 
 15 
 10 
 17 
 
 57.07 
 50. 82 
 45. 26 
 
 3257. 
 2.583. 
 2048. 
 
 . 002 558 
 . 002 028 
 .001 009 
 
 3.248 
 4.095 
 5.164 
 
 3.502 
 4.491 
 5. 003 
 
 3.876 
 4.887 
 6. 162 
 
 18 
 19 
 20 
 
 40. .30 
 35. s9 
 31.90 
 
 1624. 
 
 1288. 
 1022. 
 
 .001 270 
 .001 012 
 .000 802 3 
 
 6.512 
 8. 210 
 10.35 
 
 7.141 
 9.004 
 11.30 
 
 7.771 
 9.799 
 12.36 
 
 21 
 23 
 
 28. 40 
 2.5. 35 
 22.57 
 
 810.1 
 642.4 
 509.5 
 
 .000 636 3 
 . 000 504 6 
 . 000 400 2 
 
 13.06 
 16. 46 
 20.76 
 
 14.32 
 
 IS. 06 
 22.77 
 
 15.58 
 19. (a 
 
 24.78 
 
 24 
 25 
 26 
 
 20.10 
 17.90 
 15.94 
 
 404.0 
 320. 4 
 254.1 
 
 .0<X) 317 3 
 .0(H) 251 7 
 .000 199 6 
 
 26.18 
 33.01 
 41.62 
 
 28.71 
 30. 20 
 45.05 
 
 31.24 
 ,39.39 
 49.68 
 
 27 
 28 
 29 
 
 14.20 
 12.04 
 11.26 
 
 201.5 
 159.8 
 126.7 
 
 .000 158 3 
 . 000 125 5 
 .000 099 53 
 
 52.48 
 66.18 
 83.46 
 
 57.56 
 72.59 
 91.53 
 
 62.64 
 78.98 
 99.60 
 
 30 
 31 
 32 
 
 10.03 
 8.928 
 7.950 
 
 100.5 
 79.70 
 63.21 
 
 .000 078 94 
 . 000 062 60 
 . 000 049 64 
 
 105.2 
 132.7 
 167.3 
 
 115.4 
 145.5 
 183.5 
 
 125. 6 
 158.4 
 199.7 
 
 33 
 34 
 35 
 
 7.080 
 0. 305 
 5. 015 
 
 50.13 
 39.75 
 31.52 
 
 . 000 039 37 
 .(K)0 031 22 
 .000 024 70 
 
 211.0 
 266. 1 
 335.5 
 
 231.4 
 
 291.8 
 367.9 
 
 251.8 
 317.5 
 400.4 
 
 3() 
 37 
 38 
 
 5.000 
 4. 4.^)3 
 3. 9ti5 
 
 25.00 
 19.83 
 15.72 
 
 .000 019 04 
 .000 015 57 
 .000 012 35 
 
 423.0 
 5,33.5 
 672.7 
 
 464.0 
 5S5.1 
 737.7 
 
 504.9 
 636.7 
 802.8 
 
 39 
 40 
 
 3. 531 
 3. 145 
 
 12.47 
 
 9.888 
 
 . 000 009 793 
 
 . (H»0 007 700 
 
 848.2 
 1070. 
 
 930.2 
 1173. 
 
 1012.0 
 
 1270. 
 
 (161)
 
 62 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 Wire table, standard annealed copper. 
 
 [American wire gauge (B. & S.)I 
 
 
 
 
 
 
 
 Feet per ohm. 
 
 
 
 Gauge 
 No. 
 
 Diam- 
 eter in 
 mils. 
 
 Pounds 
 
 per 1,000 
 
 feet. 
 
 Feet per 
 pound. 
 
 
 
 
 
 
 
 0°C. 
 (=32° 
 
 F.). 
 
 15° C. 
 
 (=59° 
 
 F.). 
 
 20° C. 
 
 (=68° 
 F.). 
 
 25° r. 
 
 (=77° 
 F.). 
 
 50° 0. 
 
 (=122° 
 
 F.). 
 
 75° r. 
 (=167° 
 
 F.). 
 
 0000 
 
 000 
 
 00 
 
 400.0 
 109.6 
 304.8 
 
 040.5 
 507. 9 
 402.8 
 
 1.501 
 
 1. 90S 
 
 2. 482 
 
 22 150. 
 17 570. 
 13 930. 
 
 20 810. 
 10 510. 
 13 090. 
 
 20 400. 
 10 ISO. 
 12 830. 
 
 20 010. 
 15 870. 
 12 580. 
 
 18 240. 
 14 470. 
 11 470. 
 
 10 700. 
 13 290. 
 10 540. 
 
 
 1 
 2 
 
 324.9 
 289.3 
 257.6 
 
 319.5 
 a53.3 
 200.9 
 
 3.130 
 3.947 
 4.977 
 
 11 050. 
 875 1. 
 6948. 
 
 10 380. 
 8233. 
 0529. 
 
 10 ISO. 
 8070. 
 0400. 
 
 9979. 
 7913. 
 6270. 
 
 9098. 
 7215. 
 5722. 
 
 8.361. 
 6630. 
 5258. 
 
 3 
 
 4 
 5 
 
 229.4 
 204.3 
 181.9 
 
 159. 3 
 126.4 
 100.2 
 
 6. 276 
 7.914 
 9.980 
 
 5510. 
 4370. 
 3465. 
 
 5178. 
 4100. 
 3250. 
 
 5075. 
 4025. 
 3192. 
 
 4977. 
 .3947. 
 3130. 
 
 4538. 
 3599. 
 2854. 
 
 4170. 
 3307. 
 2022. 
 
 6 
 
 7 
 8 
 
 162.0 
 114.3 
 128.5 
 
 79.40 
 63. 02 
 49.98 
 
 12.58 
 15. S7 
 20.01 
 
 2748. 
 2179. 
 172S. 
 
 2582. 
 2048. 
 1024. 
 
 2531. 
 2007. 
 1592. 
 
 2482. 
 1968. 
 1561. 
 
 2263. 
 1795. 
 1423. 
 
 2080. 
 1049. 
 1308. 
 
 9 
 10 
 11 
 
 114.4 
 101.9 
 90.74 
 
 39.63 
 31.43 
 24.92 
 
 25. 23 
 31. 82 
 40.12 
 
 1371. 
 1087. 
 802.0 
 
 1288. 
 1021. 
 810.0 
 
 1202. 
 1001. 
 794.0 
 
 1238. 
 981. 8 
 778.5 
 
 1129. 
 895. 1 
 709.9 
 
 1037. 
 822. 6 
 652.4 
 
 12 
 13 
 14 
 
 80.81 
 71. 90 
 04. 08 
 
 19.77 
 15. 68 
 12.43 
 
 50.59 
 63. 80 
 80.44 
 
 083.6 
 542. 
 429.9 
 
 642. 3 
 .509.4 
 404.0 
 
 629.6 
 499.3 
 396.0 
 
 617.4 
 489. 
 388. 3 
 
 .563.0 
 440.4 
 .354. 
 
 517. 3 
 410.3 
 
 325. 4 
 
 15 
 16 
 17 
 
 57.07 
 50.82 
 45. 26 
 
 9. 858 
 7. 818 
 6.200 
 
 101.4 
 127.9 
 161.3 
 
 340.9 
 270.4 
 214.4 
 
 320. 4 
 254. 1 
 201. 5 
 
 314.0 
 249.0 
 197.5 
 
 307.9 
 244.2 
 193. 7 
 
 280. 8 
 222.7 
 170.0 
 
 258. 
 201. 
 162. 3 
 
 18 
 19 
 20 
 
 40.30 
 35.89 
 31.96 
 
 4.917 
 3.899 
 3.092 
 
 203. 4 
 2.50.5 
 323. 4 
 
 170.0 
 
 134. 8 
 
 100. 9 
 
 159. 8 
 120. 7 
 100.5 
 
 150. 
 124.2 
 98. 49 
 
 153.0 
 121.8 
 90. 59 
 
 140.0 
 111.1 
 
 88.07 
 
 128. 7 
 102. 
 80.93 
 
 21 
 22 
 23 
 
 28. 46 
 2.5. 35 
 22.57 
 
 2.452 
 1.945 
 1..542 
 
 407.8 
 514.2 
 048. 4 
 
 84.81 
 67. 25 
 53. 34 
 
 79.09 
 03. 20 
 50. 12 
 
 78.11 
 01.95 
 49.12 
 
 7(). 00 
 00. 74 
 48.17 
 
 09. 84 
 .55.39 
 43. 92 
 
 04. IS 
 50. 90 
 40. 36 
 
 21" 
 
 2r> 
 
 2(i 
 
 20.10 
 17.90 
 15. 94 
 
 1.223 
 0. 9699 
 . 7692 
 
 817. 7 
 1031. 
 1300. 
 
 42. .30 
 33. 54 
 26. 60 
 
 39.74 
 31.52 
 25.00 
 
 38.96 
 30.90 
 24.50 
 
 38.20 
 30. 30 
 24.02 
 
 34. 83 
 
 27. 02 
 
 . 21.91 
 
 32.01 
 25. 39 
 20. 13 
 
 27 
 
 28 
 29 
 
 14.20 
 12. (;4 
 11.20 
 
 .6100 
 . 4837 
 .38:^6 
 
 1039. 
 2007. 
 2007. 
 
 21.10 
 16. 73 
 13. 27 
 
 19. 82 
 15. 72 
 12.47 
 
 19. 43 
 15.41 
 12.22 
 
 19. 05 
 15.11 
 11.98 
 
 17.37 
 13. 78 
 10.93 
 
 15. 90 
 12. 66 
 10.04 
 
 30 
 31 
 32 
 
 10.03 
 8.928 
 7.950 
 
 .3042 
 .2413 
 . 1913 
 
 3287. 
 4145. 
 5227. 
 
 10.52 
 8.344 
 6.617 
 
 9.886 
 7.840 
 6.218 
 
 9. 691 
 7. 085 
 0.094 
 
 9.503 
 7.530 
 5.970 
 
 8. 605 
 6.871 
 5.449 
 
 7.962 
 6.314 
 5.008 
 
 33 
 34 
 
 35 
 
 7.080 
 6.305 
 5. 615 
 
 .1517 
 .1203 
 .095 42 
 
 6591. 
 
 8310. 
 
 10 480. 
 
 5. 247 
 4. 161 
 3. .300 
 
 4.931 
 3.910 
 3. 101 
 
 4. 833 
 3. 833 
 .3.040 
 
 4.739 
 3. 759 
 2. 981 
 
 4.322 
 3.427 
 2.718 
 
 3.971 
 3.149 
 2.497 
 
 .10 
 37 
 38 
 
 5.000 
 4. 453 
 3. 90.5 
 
 .075 68 
 .0()0 0I 
 .047 .59 
 
 13 210. 
 16 600. 
 21 010. 
 
 2.617 
 2. 075 
 1. 040 
 
 2. 459 
 1.950 
 
 1.547 
 
 2.410 
 1.912 
 1.516 
 
 2. 304 
 1.874 
 1.487 
 
 2. 155 
 1.709 
 1. .356 
 
 1.981 
 1. 571 
 1. 246 
 
 39 
 40 
 
 3.531 
 3.145 
 
 .a37 74 
 .029 93 
 
 20 500. 
 33 410. 
 
 1.305 
 1.035 
 
 1.220 
 0. 9727 
 
 1.202 
 0. 9534 
 
 1.179 
 0. 9349 
 
 1.075 
 0. 8525 
 
 0.9878 
 .7834 
 
 (162)
 
 Cable and Cable Systems. — Chapter 4. 
 
 03 
 
 Wire table, Htnndard finiicfileil topper. 
 [Ainerican wire ^auge (B. A: S.).) 
 
 Gauge 
 No. 
 
 Diameter 
 in mils. 
 
 1 
 Ohms per pound. ] 
 
 0°C. (=32"?.). 
 
 15° C. (-59° F.). 
 
 20°C. (=68°F.). 
 
 0000 
 non 
 
 (10 
 
 460.0 
 409.6 
 364. S 
 
 0.000 070 41 
 .000 1120 
 .()(K) 17S() 
 
 0.000 075 09 
 .000 1192 
 .(XK) lS9(i 
 
 0.000 076 52 
 .000 1217 
 .0(K) 1935 
 
 
 
 1 
 
 2 
 
 324.9 
 2H9. 3 
 257.6 
 
 . (MH) 2.S30 
 . (MH) 4.500 
 .(KM) 71.56 
 
 .000 3015 
 jm 4791 
 . 000 7622 
 
 . 000 3076 
 .0(K) 4S91 
 . (KM) 7778 
 
 3 
 4 
 5 
 
 229.4 
 201.3 
 1S1.9 
 
 .001 l.)S 
 .(K)l S09 
 .002 S77 
 
 .001 212 
 .(K)l 927 
 .003 Wil 
 
 .001 237 
 .fK)l 966 
 .Oa3 127 
 
 6 
 
 7 
 S 
 
 162. 
 144.3 
 12S. 5 
 
 .004 574 
 . 007 273 
 .011 .56 
 
 .004 872 
 .007 747 
 .012 ,32 
 
 .004 972 
 .007 906 
 .012 .57 
 
 
 10 
 
 11 
 
 114.4 
 101.9 
 iK). 74 
 
 .018 39 
 . 029 24 
 .046 49 
 
 .019 .59 
 .031 15 
 .049 .52 
 
 .019 99 
 .031 78 
 . 0.50 53 
 
 12 
 13 
 H 
 
 SO. SI 
 71.96 
 64. OS 
 
 . 073 93 
 .1176 
 . 1S69 
 
 . 078 74 
 . 1252 
 .1991 
 
 .080 35 
 .1278 
 . 2032 
 
 1.', 
 Ifi 
 17 
 
 57. 07 
 50. S2 
 4.5. 26 
 
 .2972 
 . 4726 
 .7514 
 
 .3166 
 . .5033 
 .8003 
 
 . 3230 
 .51:56 
 
 .su;7 
 
 IS 
 19 
 20 
 
 40. 30 
 35. S9 
 31.96 
 
 1. 195 
 1.900 
 3.021 
 
 1.273 
 2.024 
 3.218 
 
 1.299 
 2. 065 
 3. 2.'s;5 
 
 21 
 22 
 23 
 
 2S. 46 
 25. 35 
 22. 57 
 
 4. 803 
 7. t)37 
 12.14 
 
 5.116 
 8. 135 
 12.93 
 
 5.221 
 8.302 
 13.20 
 
 24 
 25 
 26 
 
 20. 10 
 17.90 
 1.'). 94 
 
 19.31 
 30.70 
 
 48.82 
 
 20. 57 
 32.70 
 .52.00 
 
 20.99 
 33. 37 
 ,53. 06 
 
 27 
 2S 
 29 
 
 14.20 
 12. 64 
 11.26 
 
 77. 63 
 123.4 
 196.3 
 
 82. 69 
 131.5 
 209. 1 
 
 84.37 
 134.2 
 213.3 
 
 30 
 31 
 32 
 
 10. 03 
 
 S. 928 
 7.950 
 
 312.1 
 496.3 
 789.1 
 
 332. 4 
 528. 5 
 840.5 
 
 339.2 
 539.3 
 857.6 
 
 33 
 
 34 
 35 
 
 7.080 
 6.305 
 5.615 
 
 1255. 
 1995. 
 3172. 
 
 1336. 
 2125. 
 3379. 
 
 1364. 
 2168. ■ 
 3448. 
 
 36 
 37 
 38 
 
 5.000 
 4.453 
 3.965 
 
 5044. 
 
 8020. 
 
 12 7.50. 
 
 5372. 
 
 8542. 
 
 13 580. 
 
 5482. 
 
 8717. 
 
 13 860. 
 
 39 
 40 
 
 .3. .531 
 3. 145 
 
 20 280. 
 32 240. 
 
 21 600. 
 34 340. 
 
 22 040. 
 
 35 aio. 
 
 Continued. 
 
 (163)
 
 64 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 Wire table, stamlai-d annealed eopper — Continued. 
 [American wire gauge (B. & S.)-] 
 
 Gauge 
 No. 
 
 Diameter in 
 mils. 
 
 Ohms per poun^. 
 
 25°C. (=77° F.). 
 
 50° C. (=122° F.). 
 
 75° C. (=167° F.). 
 
 0000 
 
 (MX) 
 
 0(1 
 
 460.0 • 
 409.6 ' 
 364.8 
 
 0. 000 078 05 
 .000 1241 
 .000 1974 
 
 0.000 085 70 
 .000 13()3 
 . 000 2167 
 
 0. 000 093 34 
 .000 148:? 
 .000 2360 
 
 
 
 1 
 2 
 
 324.9 
 289.3 
 257.6 
 
 .000 3138 
 .000 4990 
 . 000 7934 
 
 .000 3445 
 .000 5478 
 .000 8711 
 
 . 000 3753 
 .000 5967 
 .000 9487 
 
 3 
 4 
 5 
 
 229.4 
 204.3 
 181.9 
 
 .001 202 
 . 002 OOti 
 .CX)3 189 
 
 .001 385 
 .002 202 
 .003 502 
 
 .001 508 
 . 032 399 
 .003 813 
 
 (■) 
 
 7 
 8 
 
 162.0 
 144.3 
 128.5 
 
 .005 071 
 .008 OM 
 .012 82 
 
 .005 568 
 .008 853 
 .014 08 
 
 .006 065 
 .009 643 
 .015 33 
 
 9 
 10 
 11 
 
 114.4 
 101.9 
 
 90.74 
 
 .020 39 
 . 032 42 
 .051 55 
 
 .022 38 
 .035 59 
 .056 60 
 
 .024 38 
 .038 77 
 .061 64 
 
 12 
 13 
 14 
 
 80.81 
 71.96 
 64.08 
 
 .081 96 
 . 1303 
 .2072 
 
 . 089 99 
 
 .1431 
 
 .2275 
 
 .098 01 
 
 .1558 
 
 .2478 
 
 15 
 16 
 17 
 
 57.07 
 50.82 
 45.26 
 
 .3295 
 .5239 
 .8330 
 
 .3616 
 .5752 
 .9146 
 
 .3940 
 .6265 
 .9962 
 
 IS 
 19 
 20 
 
 40.30 
 35.89 
 31.96 
 
 1.325 
 2. 106 
 3.349 
 
 1.454 
 2.313 
 3.677 
 
 1.584 
 2. 519 
 4.006 
 
 21 
 22 
 23 
 
 28.46 
 25. 35 
 22.57 
 
 5.325 
 8. 467 
 13.46 
 
 5.846 
 9.296 
 14.78 
 
 6.368 
 10.13 
 16. 10 
 
 24 
 25 
 26 
 
 20.10 
 17.90 
 15.94 
 
 21.41 
 34. 04 
 .54. 13 
 
 23.50 
 37.37 
 59.43 
 
 25.60 
 40.71 
 04.73 
 
 27 
 28 
 29 
 
 14.20 
 12.64 
 11.26 
 
 86.07 
 130.8 
 217.6 
 
 94.49 
 150.2 
 238.9 
 
 102.9 
 163.7 
 260.2 
 
 30 
 31 
 32 
 
 10.03 
 
 8.928 
 7.950 
 
 346.0 
 550.2 
 
 874.8 
 
 379.9 
 (i04.0 
 960.4 
 
 413.8 
 657.9 
 1046. 
 
 33 
 34 
 
 3:) 
 
 7.080 
 6. 305 
 5.015 
 
 1391. 
 2212. 
 3517. 
 
 1527. 
 2428. 
 3861. 
 
 1663. 
 2645. 
 4205. 
 
 3t; 
 
 37 
 
 .5.000 
 4.4,53 
 3.965 
 
 5592. 
 
 8892. 
 
 14 140. 
 
 6139. 
 
 9762. 
 
 15 .520. 
 
 6687. 
 
 10 {■m. 
 
 16 9(X)'. 
 
 39 
 40 
 
 3.531 
 3. 145 
 
 22 480. 
 35 740. 
 
 24 680. 
 39 2.50. 
 
 26 880. 
 42 7.50. 
 
 (164)
 
 Cable and Cable Systems. — Chapter 4. 65 
 
 STANDAKD CABhK CONSTANTS. 
 
 The standard subterranean rubber insulation cable has an insulation resist- 
 ance of about 1,800 nicf^oluns jxir mile, a capacity of about 0.40 microfarad per 
 mile, and a copper resistance ot about 37 ohms per mile wlien laid. Average 
 testing conditions should show Indelinitely an insulation resistance of not less 
 than 500 megohms per mile. 
 
 The standard rubber insulation submarine cable for fire-control and harbor 
 work has an insulation resistance of about 2,000 megohms per mile, a capacity 
 of about 0.48 microfarad per mile, and a copper resistance of about 17 ohms 
 per mile when laid. Average testing conditions should show indefinitely an in- 
 sulation resistance of not less than 600 megohms per mile. 
 
 The standard paper insulation cable for temporary and post connections hav- 
 ing No. 19 B. (k S. conductors has an insulation resistance of from 2,(XK) to 0,000 
 megohms per mile, a capacity of about 0.075 nncrofarad per mile, and a copper 
 resistance of about 43 ohms per mile when in jjlace. Average testing condi- 
 tions should show indefinitely an insulation resistance of not less than l.OdO 
 megohms per mile. 
 
 The paper insulation submarine cable has an insulation resistance as above 
 and a capacity of 0.11, with copper resistance of 43 ohms per mile when laid. 
 Average testing conditions should show indefinitely an insulation resistance 
 of not less than 1,000 megohms. 
 
 All of the above figures are based on a temperature of 60° F. 
 
 ELECTROLYSIS. 
 
 Where a subterranean cable system is so located that there is a po.ssibility of 
 it being in the path of the return current of an electric railway, tests for the 
 presence of electrolysis should be made. These tests should be made during 
 " peak of load " at railway power house, if possible. 
 
 The tests consist of connecting cable sheath of various cables of the system at 
 various points to a positive ground through a nnllivoltraeter. If practicable, the 
 street railway track should be used for the ground connection. 
 
 If a reading (regardless of magnitude) is obtained with the millivoltmeter. 
 the sheath of cable or cables should be permanently grounded at points where 
 readings are obtained. 
 
 The usual custom is to bond the cables together and connect to one heavy 
 conductor, which is connected solidly to the street railway track at a convenient 
 point. 
 
 Condemned cable makes an excellent conductor for this purpose, the con- 
 ductors and sheath both being used as the conducting medium. 
 
 FACTORY TESTING FOR THE ELECTRICAL PROPERTIES OF CABLE. 
 
 The Signal Corps .specifications require the manufacturers to supply all instru- 
 ments and facilities necessary for testing the cable. As the.se instruments are 
 different at the different factories, a description of them will not be attempted. 
 At the beginning of a series of tests at the factory, bridges, condensers, and 
 high resistances must be compared with standards to verify their accuracy. 
 
 The high-voltage test is first applied to the core. The breakdown test for the 
 standard core, after 24 hours' inmiersion in water, is the application of 6.500 
 volts alternating, for five minutes. This test will disclose any accidental im- 
 purities in the compound. While the .specifications require the application of 
 
 (165)
 
 60 Signal Corps Manual No. 3.— Chapter 4. 
 
 6.500 volts for five minutes, if a breakdown occurs it will occur almost 
 instantly after the application of the high voltage. One lead from the trans- 
 former is connected witli the copper of tlie core and the other lead inunersed in 
 the water in the tank. For the finished cable 1,000 volts are applied between 
 the armor and the core for one minute. When the high-voltage test is applied 
 to lengths of armored cable of 50 miles or more, it is, perhaps, better to use 
 direct rather than alternating voltage, to avoid any possibility of resonance and 
 the formation of stationary waves. 
 
 After the application of the breakdown test, the capacity, insulation, and 
 copper resistances of each length of the core are determined, in the order men- 
 tioned. 
 
 The capacity measurement is made by the charge method, as experience has 
 demonstrated that, using a low voltage, the readings at charge and discharge 
 are practically the same, as the effect of absorption is negligible. With some 
 of the insulating compounds used the effect of the high-voltage test is to tem- 
 porarily increase the capacity, and it will frequently happen that the first 
 measurement may be higher than that required by the specifications, but if the 
 ca1)le is allowed to stand for 24 hours the capacity will probably drop to the 
 limit prescribed by the specifications. When the first measured capacity is too 
 high it should be remeasured after 24 hours. When the capacity of long 
 lengths of cable is being tested, eitlier Thompson's or Gott's method is prefer- 
 able to using a shunted galvanometer. In measuring insulation resistance, espe- 
 cially in damp weather, care should be taken to thoroughly insulate the gal- 
 vanometer, keys, and shunt box. The leakage from the galvanometer can be 
 avoided by connecting the leveling screws together and then joining them to 
 the insulated terminal of the battery key and by supporting the leveling screws 
 on ebonite buttons. 
 
 In making the insulation measurement care should be taken to properly 
 prepare the ends of the core, so as to avoid surface leakage. The ends should 
 be freshly cut in conical form, allowing 2 or 3 inches of the copper core to 
 project so that the lead may be attached, care being taken that the freshly 
 cut surface is not touched by the fingers. It is a good plan to dry both ends 
 with an alcohol lamp, taking care that the flame does not come close enough 
 to injure the compound. 
 
 The copper resistance is measured by the usual bridge method. 
 
 In all cases, at the beginning of each series of tests, the leakage of the 
 leads, their capacity, and resi^ance are determined. 
 
 The results of each day's work should be entered on the test sheet, and 
 when the cable is finally completed the data in respect to each core and fin- 
 ished cable length should be entered on the record sheet, a copy of which 
 should be forwarded with each shipment, one retained in the office of the 
 officer making the inspection, and the third copy furnished the Chief Signal 
 Officer of the Army. 
 
 Willie the logarithmic method of computation is used in the illustrations 
 which follow, it is much better to calculate the results with the Thatcher 
 slide rule, which reads to four places of figures accurately, and by approxima- 
 tion to the fifth. One setting of this rule will serve for an entire series of 
 calculations and effects a very great saving of time. 
 
 In measuring capacity the method employe<l is the ordinary ballistic one, 
 using a batlery of but two or three volts. A deflection is obtained by charg- 
 ing a staixlard conden.ser, usually one-third of a microfarad, in series with a 
 galvanimictcr, Itattery, and key. The first throw of fhi> galvniiotiieter is noted 
 
 (106)
 
 Cable and Cable Systems. — Chapter 4. 67 
 
 -A\u\ the (leHectiuu for om- iiiicrufarad calculatctl ami ciitcri'd on tlic test sheet. 
 Tlie cable is then substituted for the standard eondenser, earthiiij^ one end 
 and the battery, and the .lellection read and noted. 
 
 In nieasurinj^ insulation resistance the galvanometer constant is first ob- 
 tained by connecting the higli resistance, usually a megohm, in series with the 
 battery of 100 volts, and galvanometer, which should be shunted with the xvins 
 sliunt, and observing the deflection, which is then corrected for the shunt 
 and noted on the test sheet. The leakage of the leads, with the same voltage, 
 is then obtained. Tlie lead is then connected to the cable, the battery applied, 
 the zinc pole to the cable, and the other side grounded. The deflection of the 
 galvanometer is noted at the expiration of a minute, and this deflectujn is 
 tiie one from whicli the insulation resistance is calculated. It is well, how- 
 ever, to allow the battery to remain on for several nunutes, noting the de- 
 flection at tlie end of each minte. Tliis deflection should fall in a gradual 
 and even manner. In the case of one of the compounds used, viz, that of the 
 Safety companj% the deflection should halve itself, 1. e., the insulatifin should 
 double itself at the third and fifth minutes. 
 
 After the insulation resistance has been obtained, the bridge is used to 
 measure the copper resistance of the c(tre and the leads. The temperature of 
 the tank is taken and noted. All measurements are made with the core or 
 cable in the tank after it lias been immersed for 24 hours, as the rubber com- 
 pound will not attain its proper insulation at any given temperature until 
 several hours after it has reached that temperature. There is always more or 
 less uncertainty about the temperature, as the water in tlie different parts of 
 the tank may not be at the same temperature ; consequently care should be 
 taken to get a uniform temperature tliroughout tlie tank. As there is less 
 uncertainty with the core than with the finished cable, tlie copper resistances of 
 the core reduced to the standard temperature may be. in case of doubt, taken 
 as a base for calculating the test temperature of the finished cable. 
 
 The insulation resistance of rubber compound varies with the temperature, 
 increasing as the temperature diminishes and decreasing as it rises. The 
 temperature law of variation of the insulation resistance can be taken ap- 
 proximately as a simple logarithmic law. The insulation resistance, diminish- 
 ing in equal ratio with an increase in the temperature, can be written in the 
 form />'=/•('', in which R is tlie resistance at the higher temperature, r the 
 resistance at the lower temperature, t the difference in tenqK'rature in <legrees 
 Fahreidieit, and C a constant, depending on the nature of the insulation com- 
 pound, which, for the Safety comi)any, can lie assumed as O.OTH, anil for the 
 Kerite O.OoU. For reilucing the insulation resistance at any observed tempera- 
 ture to that of the standard temperature, 60° F., it is necessary to have a 
 factor to multiply the resistance of the observed temperature. The O'ainife, 
 Habirshaw, and Bishop companies have found that their compounds follow the 
 logarithmic law sufficiently close for all iiracfical jturposes. The coeflidents of 
 a number of compounds, according to this simple logarithmic law, are plotted in 
 following table on logarithmic paper <lesigned by the late Mr. Townsend Wol- 
 cott. The ordinates represent the temperature and are plotted arithmetically, 
 while the abscissjie, the ratio of tlie insulation resistance at 60° F. to that at the 
 temperature of observation, are plotted logarithmically. The resistance at 60° 
 F., being taken as unity, its logarithm, zero", is in the center of the paper, and the 
 scale extends on the right to log. VlO, and on the left to log. VO.l. 
 
 (167)
 
 68 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 The following table gives the factors for reducing the insulation resistance 
 of the Okonite, Habirshaw. and Bishop companies' compounds to 60° F. accord- 
 ing to the simple logarithmic law, these compounds doubling their insulation 
 with a difference of temperature of 27° F. 
 
 Factors for retlucing the in^wlation resistance of the Okonite, HabirshaiD, and 
 Bishop compounds to 60° F. 
 
 Temper- 
 ature. 
 
 K. 
 
 LogK. 
 
 Temper- 
 ature. 
 
 K. 
 
 Log. K. 
 
 °F. 
 
 
 
 °F. 
 
 
 
 50 
 
 0.773 
 
 9. 888401 
 
 66 
 
 1.167 
 
 0. 067071 
 
 51 
 
 .793 
 
 9. 899629 
 
 67 
 
 1.197 
 
 . 078094 
 
 52 
 
 .814 
 
 9. 910802 
 
 68 
 
 1.228 
 
 . 089198 
 
 53 
 
 .835 
 
 9. 921906 
 
 69 
 
 1.260 
 
 . 100371 
 
 54 
 
 .856 
 
 9.932929 
 
 70 
 
 1.293 
 
 .111599 
 
 55 
 
 .879 
 
 9. 944240 
 
 71 
 
 1.326 
 
 . 122544 
 
 56 
 
 .902 
 
 9. 955460 
 
 72 
 
 1.361 
 
 . I33s:is 
 
 57 
 
 . 92.-. 
 
 9. 966576 
 
 73 
 
 1. 396 
 
 . U4SS.> 
 
 58 
 
 .949 
 
 9. 977572 
 
 74 
 
 1. 433 
 
 . 156246 
 
 59 
 
 .974 
 
 9.988853 
 
 75 
 
 1.470 
 
 . 167317 
 
 60 
 
 1.000 
 
 .000000 
 
 76 
 
 1. 508 
 
 . 178401 
 
 61 
 
 1.026 
 
 .011147 
 
 77 
 
 1. .547 
 
 . 1S9490 
 
 62 
 
 1. 053 
 
 . 022428 
 
 78 
 
 1.587 
 
 .200577 
 
 63 
 
 1.080 
 
 . 033424 
 
 79 
 
 1.629 
 
 . 211921 
 
 64 
 
 1.108 
 
 . 044540 
 
 80 
 
 1.671 
 
 . 222976 
 
 65 
 
 1.137 
 
 . 055760 
 
 
 
 
 As the result of careful observations of the temperature variation of the 
 Safety and Kerite compounds, Mr. Townsend Wolcott, formerly electrical engi- 
 neer, Signal Corps, gives the following formula : 
 
 Log.f§^=(.00802488+.0000446190 = (60-0 
 Log.(^J' ^ = (. 00845964+. 0002866040 = (60-0 
 
 in which Rt is the resistance at the temperature of ol>servation and /?,«, is the 
 resistance at 60° F. Calling the reciprocal of tliis ratio K, the following table 
 has been calculated for the Safety and Kerite compounds : 
 
 (168)
 
 Cable and Cable Systems. — ^Chapter 4. 69 
 
 Tcmijcrutuic corfficioil for the reduction' of insulation rdiintfUicc to U0° F. 
 
 
 Safety. 
 
 
 Kerite. 
 
 Temper- 
 
 
 
 Temper- 
 
 
 
 ature. 
 
 
 
 ature. 
 
 
 
 
 K. 
 
 Log. K. 
 
 
 K. 
 
 Log. K. 
 
 ° F. 
 
 
 
 op 
 
 
 
 50 
 
 0.789 
 
 9. 897441 
 
 50 
 
 0.591 
 
 9.772110 
 
 51 
 
 . S07 
 
 9. 907300 
 
 51 
 
 .619 
 
 9. 792:525 
 
 52 
 
 .826 
 
 9.917240 
 
 52 
 
 .650 
 
 9. 813104 
 
 53 
 
 .845 
 
 9.927277 
 
 53 
 
 .683 
 
 9. 834457 
 
 M 
 
 .865 
 
 9.937396 
 
 54 
 
 .718 
 
 9.856390 
 
 55 
 
 .886 
 
 9. 947609 
 
 55 
 
 .756 
 
 9. 878890 
 
 56 
 
 .907 
 
 9. 957908 
 
 56 
 
 .797 
 
 9. 901968 
 
 57 
 
 .929 
 
 9. 968296 
 
 57 
 
 .823 
 
 9. 92.5<)15 
 
 58 
 
 .952 
 
 9. 978776 
 
 58 
 
 .891 
 
 9. 949k;j6 
 
 59 
 
 .975 
 
 9. 989343 
 
 59 
 
 .943 
 
 9. 974632 
 
 60 
 
 1.000 
 
 0.000000 
 
 60 
 
 1.000 
 
 0.000(X)0 
 
 61 
 
 1.025 
 
 .010746 
 
 61 
 
 1.061 
 
 .025941 
 
 62 
 
 1.0r)0 
 
 .021582 
 
 62 
 
 1.128 
 
 . 0524.56 
 
 63 
 
 1.080 
 
 . 033505 
 
 63 
 
 1.201 
 
 . 079.545 
 
 64 
 
 1.105 
 
 .043500 
 
 64 
 
 1.280 
 
 . 107204 
 
 65 
 
 1.134 
 
 . 0.54625 
 
 65 
 
 1.367 
 
 . 13.5755 
 
 66 
 
 1.163 
 
 .065714 
 
 66 
 
 1.460 
 
 .164244 
 
 67 
 
 1.194 
 
 .077098 
 
 67 
 
 1.562 
 
 . 193627 
 
 68 
 
 1.226 
 
 .088624 
 
 68 
 
 1.673 
 
 .2235.84 
 
 69 
 
 1.258 
 
 .099927 
 
 69 
 
 1.796 
 
 .254106 
 
 70 
 
 1.292 
 
 .111482 
 
 70 
 
 1.928 
 
 .285210 
 
 71 
 
 1.328 
 
 . 123120 
 
 71 
 
 2.074 
 
 .316827 
 
 72 
 
 1.364 
 
 .134844 
 
 72 
 
 2.234 
 
 .349128 
 
 73 
 
 1.401 
 
 . 146666 
 
 73 
 
 2.409 
 
 .381953 
 
 74 
 
 1.441 
 
 . 158564 
 
 74 
 
 2.602 
 
 .415338 
 
 75 
 
 1.481 
 
 . 170565 
 
 75 
 
 2.814 
 
 .449310 
 
 76 
 
 1.523 
 
 . 182640 
 
 76 
 
 3.046 
 
 .483760 
 
 77 
 
 1.566 
 
 . 194820 
 
 77 
 
 3.303 
 
 .518959 
 
 78 
 
 1.611 
 
 . 207090 
 
 78 
 
 3. .586 
 
 . 5546.52 
 
 79 
 
 1.657 
 
 . 219431 
 
 79 
 
 3.899 
 
 .590900 
 
 80 
 
 1.705 
 
 . 231888 
 
 80 
 
 4.244 
 
 . 627740 
 
 The resistance of copper increases witli the increase of temperature. In 
 order to i*educe copper resistances at any temperature between 50° and 80° F. to 
 60° F., tlie following table has been calculated in whic-li 5 is the factor i).v which 
 the resistance at the observed teni[)erature should be multiplied to reduce it to 
 60° F. 
 
 Rvduction, of coiipcr rcsistdncc to 60° F. 
 
 Temper- 
 
 0. 
 
 ature. 
 ° F. 
 
 
 50 
 
 1.022 
 
 51 
 
 1.019 
 
 52 
 
 1.017 
 
 53 
 
 1.015 
 
 54 
 
 1.013 
 
 00 
 
 1.011 
 
 56 
 
 1.009 
 
 57 
 
 1.007 
 
 58 
 
 1.0(M 
 
 59 
 
 1.IK)2 
 
 60 
 
 l.()(X) 
 
 61 
 
 .9977 
 
 62 
 
 .9958 
 
 63 
 
 .9944 
 
 64 
 
 .9916 
 
 65 
 
 .9895 
 
 Log.i. 
 
 0. 009451 
 .008174 
 . 007321 
 . 0()W66 
 . 00.5609 
 .004751 
 .003891 
 . 00.3029 
 .(M)i7;{4 
 
 .IHKIStiS 
 .(MKKKX) 
 9. 99iK)81 
 9.998165 
 9. 997551 
 9.996338 
 .995428 
 
 Temper- 
 
 S. 
 
 ature. 
 
 ° /•". 
 
 
 66 
 
 0. 9875 
 
 67 
 
 .9847 
 
 68 
 
 .9.s;i4 
 
 69 
 
 .yM3 
 
 70 
 
 . 9793 
 
 71 
 
 .9773 
 
 72 
 
 . 9752 
 
 73 
 
 .9732 
 
 74 
 
 .9712 
 
 75 
 
 . 9692 
 
 76 
 
 .9672 
 
 77 
 
 . 9l\rii 
 
 78 
 
 . 9633 
 
 79 
 
 . 9613 
 
 80 
 
 .9594 
 
 Log, 5. 
 
 9.994519 
 9. 99.3614 
 9. 992707 
 9.99IS05 
 9. 99090:{ 
 9.990003 
 9. 989107 
 9.98.8211 
 9.987317 
 9. 98642.5 
 9. 985.5.35 
 9. 984647 
 9. 983760 
 9. 9828.57 
 9. 981993 
 
 The two following tables illustrate the manner in which the records of factory 
 tests are kept, and the next is an example of a record sheet. 
 
 In the following where miles are indicated, statute miles arc meant unless 
 nautical miles are specifically mentioned. iNIultiply statute miles by the factor 
 1.1538 to obtain nautical miles. 
 
 (1G9)
 
 70 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 J^ 
 
 ft; 
 
 OT3 
 
 as 
 
 ga 
 
 , • ~^ S3' 
 
 a ^= 
 
 SS -5 
 
 •^ c s 
 
 ■* o 
 
 'Si u 
 
 c o 
 
 a 
 
 
 O T.O 
 Si •— '7, 
 
 u is 
 •- ^-? 
 
 =' a 
 
 t± a 
 
 
 2.=!fc; 
 
 
 .SS; 
 
 2.2 S J- 
 
 t- aj a/ C 
 o -gtc o 
 
 
 •-^ 3 
 
 ^aa 
 
 L. 0/ O' d 
 
 or;« o 
 
 Ofc'S-B 
 
 3.a 
 
 TttpO?OCOCOCCCC(N'M'<T 
 O^ O^ O) O^ Oi ^ Oi 0^ Oi Gi 
 
 M O Ol ■«*< CO O 1:^ C-l O C^I 
 
 ■«#^COfMTfTj<COCOC0 01 
 
 O Ol d 05 05 Ol Ol Oi Ol Oi 
 
 CO O Ol CO CC'sC t^ CI c ^ 
 
 I^ Tj* -^ I--, t^ Q ^ O Tt* lO 
 
 CO CO n i-^ CO -^ CO "M CI i-H 
 
 O 'X »— I iC >0 CC Ol '— ' Oi CO 
 C-l lO O <—< Tt< Oi lO C) CO (M 
 ■"^cDCCOOfMCDt^OOW 
 
 ^1-(<N.-H(N»-H^C^1-H<N 
 
 O Oi O CI O 1-1 1^ »0 OS »o 
 Cl-^iOCOCOOO-^i-HMt^ 
 
 ■^'y^cooociot^O'^ci 
 
 ^-TF-H'cii-rcrf-H'^cri-rcf 
 
 iO»O00<X)t— lOcdl^iOGC' 
 
 : <M f cCi r- '-' 1-H CI -^ 
 
 ; ^^ -^ .— . ir: lo CO '^ >— ' 
 
 i-^ CI '^ o o c: CO CO •* c 
 ai i^ CI >c CO :o o -** I-- c 
 
 OC' CI d ^ to CO CT> ':o O CO 
 
 Ct CI CI CI CJ C) CI CI CI CI 
 
 Ct CI CI CI CI CI CO c 
 
 •-H I- C CI C: OS -^ C iC lO 
 
 OS cTj <S <:Z! v:) GTi Oi OS cA r/i 
 
 CI CI CI CI CI CJ CI CI CI CI 
 
 o>crjoscrjoiO>oiososcK 
 
 CI Cl CI CI CI CI CI CI CI CI 
 
 ^SScoSco-^^^S 
 
 CI CO CI CI CO CO CO CI CI ^ 
 
 lo to lO i/Tio lo »o»o ira »o 
 
 '^ t^ cr* o) o «-* CI CO -^ 'O 
 
 "So^SosSooooos 
 
 (170> 
 
 S f 
 
 >. ?,-9, 
 
 • CI *— 
 
 
 
 
 
 
 
 o 
 
 
 
 l^s 
 
 J:; 
 
 
 
 
 
 
 o 
 
 P5P.C3 
 
 
 
 _ Bo 
 
 g 
 
 
 22S 
 
 tn 
 
 
 .a 
 
 
 
 
 
 
 
 
 
 
 
 o 
 
 •a • 
 
 Cl 
 
 
 2iT3 
 
 
 
 -5 
 
 g_2 
 
 cf 
 
 
 c 
 
 = o 
 
 
 
 
 
 
 
 o 
 
 
 
 
 OJ 
 
 
 
 
 "3 s 
 
 
 
 
 
 
 
 
 
 
 
 
 ^•m 
 
 
 
 
 Oi 
 
 
 
 
 ■- 
 
 
 
 
 g^ ■ 
 
 
 
 
 •^a°„ 
 
 
 
 
 ^.uS 
 
 
 
 
 C o 
 
 
 
 
 t-i p, 
 
 
 
 3-w 
 
 
 
 
 .a«^ 
 
 
 
 
 u- 
 
 
 
 
 
 
 
 
 
 
 
 o3° 
 
 
 
 c 
 
 H 
 
 
 
 p g ffl C3 
 
 
 
 
 
 
 03 
 
 ■:= G c3 =5.2 
 -S.2fe-§^ 
 
 
 
 
 ^S^o 
 
 
 
 1^« 
 
 
 
 
 
 5 
 
 
 
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 o'S 
 
 
 
 
 O^ 
 
 
 
 
 f= 
 
 
 
 fco 
 
 a 
 
 
 
 Sqa 
 
 
 
 
 
 
 
 
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 p-S 
 
 ? 
 
 
 
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 « a 
 
 
 
 
 
 
 
 
 o o 
 
 
 
 C 
 
 
 
 
 
 
 
 
 ■« d 
 
 
 
 
 ii.o 
 
 
 
 
 
 
 
 
 C-x) 
 
 
 
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 A i'' S C 
 
 
 
 
 5 ^'S.2 
 
 
 
 
 
 
 
 
 ■£*-: 
 
 
 o^ a; 
 
 o 
 
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 c-Si 
 
 
 i^a 
 
 ^3 
 
 ^.g 
 
 
 
 
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 ^.■^ 
 
 
 
 
 
 
 
 « 
 
 
 o 
 H 
 
 2 P
 
 Cable and Cable Systems. — Chapter 4. 
 
 71 
 
 Record sheet. 
 
 [Manufacturer, Safety Insulated Wire and Cable Company; type, deep-sea cable; loaded on U. S. Army 
 
 transport -fiurni-jdf. J 
 
 Section 
 
 Length 
 
 Capacity. 
 
 Insulation. 
 
 Copper. 
 
 Core. 
 
 Cable. 
 
 
 
 Core. 
 
 Cable. 
 
 No. 
 
 (miles). 
 
 
 
 
 
 Core, 
 per 
 
 Cable, 
 per 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Abso- 
 
 Per 
 
 Abso- 
 
 Per 
 
 mile. 
 
 mile. 
 
 Abso- 
 
 Per 
 
 Abso- 
 
 Per 
 
 
 
 lute. 
 
 mile. 
 
 lute. 
 
 mile. 
 
 
 
 lute. 
 
 mile. 
 
 lute. 
 
 mile. 
 
 85 
 
 5.138 
 
 1.988 
 
 0.387 
 
 1.775 
 
 0.345 
 
 1,613 
 
 1,073 
 
 90.26 
 
 17.58 
 
 90.32 
 
 17. 58 
 
 86 
 
 5.097 
 
 1.944 
 
 .391 
 
 1.635 
 
 .321 
 
 1,421 
 
 1,150 
 
 89.31 
 
 17.52 
 
 89.60 
 
 17. 58 
 
 87 
 
 5.082 
 
 1.775 
 
 ..349 
 
 1.525 
 
 .300 
 
 1,269 
 
 1,119 
 
 86.36 
 
 17. .57 
 
 88.92 
 
 17.50 
 
 88 
 
 5. 125 
 
 2.063 
 
 .402 
 
 1.610 
 
 .314 
 
 1,350 
 
 778 
 
 86.99 
 
 17.55 
 
 88.47 
 
 17.26 
 
 89 
 
 4.855 
 
 1.750 
 
 .360 
 
 1.480 
 
 .305 
 
 1,409 
 
 1,108 
 
 85.12 
 
 17.13 
 
 85.46 
 
 17.61 
 
 90 
 
 4.853 
 
 1.750 
 
 .360 
 
 1.500 
 
 .309 
 
 1,416 
 
 1,077 
 
 85.05 
 
 17. .52 
 
 8.3.95 
 
 17. .30 
 
 91 
 
 4.848 
 
 1.795 
 
 .370 
 
 1.613 
 
 .333 
 
 1,416 
 
 1,122 
 
 &5. .39 
 
 18.01 
 
 83.95 
 
 17.20 
 
 92 
 
 4.841 
 
 1.964 
 
 .405 
 
 1.709 
 
 .352 
 
 1,637 
 
 1,312 
 
 84.95 
 
 17.53 
 
 84.25 
 
 17.37 
 
 93 
 
 4.877 
 
 1.807 
 
 .370 
 
 1.590 
 
 .320 
 
 1,487 
 
 1,232 
 
 85.24 
 
 17.47 
 
 85.31 
 
 17.49 
 
 94 
 
 5.133 
 
 1.889 
 
 .368 
 
 1.702 
 
 .331 
 
 1,510 
 
 1,099 
 
 89.97 
 
 17.53 
 
 89.32 
 
 17.40 
 
 95 
 
 5.138 
 
 2.115 
 
 .411 
 
 1.596 
 
 .311 
 
 1,610 
 
 1,043 
 
 90.15 
 
 17.54 
 
 88.46 
 
 17.30 
 
 96 
 
 5.097 
 
 1.863 
 
 • .365 
 
 1.630 
 
 .320 
 
 1,261 
 
 1,306 
 
 89.11 
 
 17.48 
 
 87.98 
 
 17. 26 
 
 97 
 
 5.112 
 
 2.012 
 
 .393 
 
 1.637 
 
 .320 
 
 1,454 
 
 1,039 
 
 90.34 
 
 17.68 
 
 91.34 
 
 17.87 
 
 98 
 
 5.098 
 
 1.978 
 
 .388 
 
 1.699 
 
 .333 
 
 1,699 
 
 1,306 
 
 89.50 
 
 17.56 
 
 88.40 
 
 17.35 
 
 99 
 
 5.107 
 
 1.884 
 
 .369 
 
 1.589 
 
 .311 
 
 1,267 
 
 852 
 
 89.14 
 
 17.46 
 
 90.32 
 
 17.68 
 
 100 
 
 5.138 
 
 2.172 
 
 .423 
 
 1. 6.33 
 
 .318 
 
 1,358 
 
 1,205 
 
 90.22 
 
 17.56 
 
 89.40 
 
 17.40 
 
 The fullowiug coniijutatiini illusti-ates the lo.narlthmic moth(xl of calculatiug 
 the data contained in record sheet of Safety Company cable. 
 
 CAPACITY. 
 
 Loj;. 1800=3. 255273 
 Log. 853=2. 930949 
 
 Absolute capacity, 2.110 .324324 
 Log. 5.107= . 708166 
 
 Capacity per mile, 0.413 1.616158 
 
 INSULATION RESIST.\NCE. 
 
 970—29=941 
 Log. 185000=5.267172 
 Log. 941=2.973590 
 
 Insulation at temperature of observation, 196 2. 293582 
 
 Log. K = .207090 
 
 Total insulaiioii at 60° F., 510 2. 501672 
 Log. 5.107= .7(KS166 
 
 Insulation resistance per mile, 1621 3. 209838 
 
 46381°— 17- 
 
 -12 
 
 (171)
 
 72 Signal Corps Manual No. 3. — Chapter 4. 
 
 I COPPER RESISTANCE. 
 
 94.5—1.38=93. 12 
 Log. 93.12=1. 969043 
 Log. 5 =9.983760 
 
 Total resistance at 60° F., 87.66 1. 942803 
 Log. 5.107= . 708166 
 
 Resistanct> per mile at 60° F.. 17.16 .234637 
 
 UATA FOR SAFETY IXSCLATKD WIKK A.NU CABLE COMPANY'S COMPOUND. 
 
 Specific gravity of conipoi'.nd, 1.(i46. 
 
 Weight i»er c\il)ic toot of coiiipouiul. lo."! iniuiuls. 
 
 Oajjacity per mile, solid coiiduc(or= 
 
 Capacity per nautical mile, solid coJi<luctor= 
 Capacity ])er mile, 7-stranded conduct or= 
 
 log. Z>-log. (/ 
 
 2o2U 
 
 log. Z) — log. d 
 .2063 
 
 log../) -log. 2.27 8 
 
 Capacity i)er nautical mile, 7-stranded coiiduct()r=, , ^ "' 
 
 log. />-log. 2.27 6 
 
 Insulation ivsislance jier mile, solid con(luctor = 1982 (log. J> — log. d). 
 Insulation resistance per nautical mile, solid conductor=175G (log. 1) — - 
 log. il). 
 
 Insulation resistance per mile, 7-stranded conductor=1982 (log. D — log. 
 2.27 5). 
 
 Insulation resistance per nautical mile, 7-sti-andt>(l c()nductor=1756 (log. 
 D— log. 2.27 5). 
 
 Weight i»er mile of compound, solid core=2956 (/)" — rf"). 
 Weight per mile of comi)ound, 7-stranded conductor =2956 (/>^— 6.9 5^). 
 /> = outsid(> diameter of insulation. 
 (Z=diameter of solid conductor. 
 5=dianieter of single strand. 
 
 PATA I'OU KlCKPrE. 
 
 Spe<-ific gravit.v of ••omiioiind. 1.2.">o. 
 Weight per cubic foot, 77 jxtunds. 
 
 1738 
 
 Capacity |)er mile, solid c(mductor=, ' ' , 
 
 log. />-log. d 
 
 Capacity i)crnautic:il mile, solid conductor= — ' ' " — -. 
 
 log. y> = log. a 
 
 1738 
 Capacity per mile, 7-stran(l<'d coiiductor=. 
 
 log. D-log. 2.27 6 
 
 1 Qfi9 
 
 Capacity pernautical mile, 7-8tranded conductor=, = — ^ — t^-t^ttt 
 
 *^ ' log. D-log. 2.27 « 
 
 (172)
 
 Cable and Cable Systems. — Chapter 4. 
 
 73 
 
 Insulation resistanre jht mile, solid (•(m(lu('tor=2147 lloj,'. I* — !<•;;. <l). 
 Insulation resistancv jicr iiautiiiii mile. soli<l contluctor^^lGOL' (loji. D — 
 loj,'. '/). 
 
 Insulation re.sistance jter mile, T-stranded (•onductor=2147 ( lo;r. I) — lo;r. 
 2.27 5). 
 
 Insulation resistance per nautical mile, 7-straiided <oiidu<tor=l!)(H.' (log. 
 /)— log. 2.27 8). 
 
 Weight per mile of (•(»mi)ouiid with solid (•or"^22ll ( /)' — <l^). 
 Weight per mile of compound, 7-stranded conductor=2211 ( />'— 6.9 S"). 
 Z)=outside diameter of insulation. 
 rf=diameter of solid conductor. 
 5=diaiueter of single strand. 
 
 Conversion tables. 
 
 statute miles to 
 nautical miles. 
 
 Nautical miles to 
 statute miles. 
 
 Statute 
 miles. 
 
 Nautical 
 miles. 
 
 Nautical 
 miles. 
 
 Statute 
 miles. 
 
 1 
 2 
 3 
 4 
 5 
 6 
 7 
 8 
 9 
 
 0. 8674 
 1. 7348 
 
 2. f)n2:{ 
 
 3. 4697 
 4.3371 
 5. 2045 
 6. 0719 
 6. 9394 
 7.8068 
 
 1 
 2 
 3 
 4 
 5 
 6 
 
 S 
 9 
 
 1.1528 
 2.30.57 
 3. 4585 
 4.6114 
 5. 7642 
 6.9170 
 8.0699 
 9. 2127 
 10.3756 
 
 Statute miles to kilo- 
 meters. 
 
 KDometers to stat- 
 ute miles. 
 
 Miles Kilome- 
 ^"^- ters. 
 
 Kilome- 
 ters. 
 
 Miles. 
 
 1 
 2 
 3 
 4 
 5 
 6 
 7 
 8 
 9 
 
 1. 60935 
 3. 21S(i9 
 4. 82S04 
 6. 43739 
 8.04674 
 9. 65t>()8 
 11.26543 
 12. 87478 
 14.48412 
 
 1 
 2 
 3 
 4 
 5 
 6 
 7 
 8 
 9 
 
 0. 62137 
 
 1. 24274 
 1.86411 
 
 2. 48548 
 3. 10685 
 3. 72822 
 4. 34959 
 4. 9709<j 
 5.59233 
 
 (178)
 
 74 
 
 Signal Corps Manual No. 3. — Chapter 4. 
 
 ^4 .4S s .ss .e .es .7 .7s .8 .as s as r. 
 
 FIG. 4-43— COEFFICIENTS FOR REDUCING INSULATION RESISTANCE AT 
 FERENT TEMPERATURES TO 60° F. 
 
 DIF- 
 
 (174)
 
 Chapter 5. 
 
 AERIAL LINE CONSTRUCTION. 
 
 The followiiiij,-, wliidi aiiiioared in " Tole^irapli and Tclcpliono Age, :May 10. 
 191")," sliimltl Ite noted, as il coincides witli tlie oi)inion of those wlio hav(> liad 
 wide experience in line construction 1'or the Signal Corps: 
 
 MODEUN 1,1 NE COXSTRfCTIOX. 
 
 Present-day telegraph-line construction is iu marked contrast with the notions pre- 
 vailing a few yt'ars ago. High poles were then considered to be the proper way of 
 placing a line out of harm's way, but, with the constant accretion of wires and the in- 
 creasing frequency of wind and sleet storms, a revision of former methods of construction 
 became necessary. The only way to render a line proof against the extraordinary strains 
 put upon it under modern conditions is to use shorter and stouter poles. This now is 
 the rule, with beneficial results, although the mechanical load and the violence of 
 nature's outbreaks still have to be reckoned with. The shorter poles are more durable 
 and better able to carry their burden and withstand the attacks of the elements. 
 
 Where aerial construction is employed, the system should be designed to 
 utilize cable, as far as practicable, thereby avoiding a large number of aerial 
 wires. Lightning arresters should always be installed to protect cables and 
 telephones connected to an aerial circuit. Outside distril>uting wire is provided 
 for leading from the pole to .substations of post telephone systems. 
 
 ERECTION or LINE. 
 
 The route of the line having been decided upon and the materials preparetl 
 or procured, a competent person should proceed to measure the distance and 
 indicate, by stakes, the places at which poles are to be erected. When the line 
 follows highways or other defined routes, he will necessarily be governed by the 
 bounds of such route and must place his stakes within those bounds and in .such 
 a manner as to avoid, as far as possible, danger to the line from pa.ssing vehicles. 
 
 As a general rule in open (unfenced) country the stakes may be placed in 
 .straight lines, but where there is a well defined and traveled road the line of 
 stakes umst follow the general direction of such inad and be set at such distance 
 from it that the line when completed shall not l)e exposed to injury from 
 passing vehicles, or, in case a wire should become detached from the insulators, 
 it can not by any chance hang in the road and interfere with or endanger traffic. 
 With this in view, the line must be .so placed as to be readily inspected ami 
 examined by reiiair men from the road. Whenever practicable, the line should 
 be removed from the road a distance of about 30 feet. Roads .should never be 
 crossed unless necessar.v to avoid bad ground or trees which are too nmnerous 
 to cut away, or to make material saving by shortening the line. Such crossings 
 should he made at half a right angle. In rolling country, poles should be 
 planted near the crests of hills and not on each side, as in the latter case the 
 wire will not be raised sufficiently high above the ground to be free from danger 
 of being broken by passing herds or vehicles. As far as practicable, grade the 
 line by using the longer poles in hollows and the .sliorter ones on high ground. 
 
 At all crossings the distance between poles should be shorteneil and the height 
 of wire above crowu of road be not less than IS feet. 
 
 (I75t 1
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 Poles should be preferai)l.v of red cedar, black locnst. or chestnut. Should 
 these not be lirocurable, or only at too jri'^Jit cost, recour.se may be had to other 
 kinds of timber, such as redwood, white cedar, red cypress, yellow cypress, 
 tamarack, fir, larch, spruce, white or post oak, sassafras, and othei's. from 
 which good service may be expected. 
 
 All poles should be of the first quality of live sreen timber, free from rot, and 
 sound and substantial in every respect. Each pole should contain the natural 
 butt of the ti'ee and have an approximately iiniformly decreasinc; cross section 
 from butt to top. 
 
 All poles should be cut between November 1 and March 1, and should be free 
 from all bark and soft wood. All knots shoidd be trimmed clo.sely and .smoothly. 
 The sizes and dimensions of poles should conform to the table below. 
 
 When octagonal poles are ordered they should be of the same material as 
 specified for standard jtoles, and should conform in general to the dimensions in 
 the table. 
 
 Desired (?//Hr«.s'/o«.s of irootl iioU s. 
 
 Length of 
 
 Circumference. 
 
 Length of 
 
 Circumference. 
 
 
 
 
 
 poles. 
 
 
 At 6 feet 
 
 poles. 
 
 
 At fl feet 
 
 
 At top. 
 
 from bot- 
 tom. 
 
 
 A( top. 
 
 from bot- 
 tom. 
 
 Feet. 
 
 Inches. 
 
 Inches. 
 
 Feet. 
 
 Inches. 
 
 Inches. 
 
 20 
 
 14 
 
 24 
 
 35 
 
 22 
 
 37 
 
 20 
 
 1() 
 
 25 
 
 35 
 
 25 
 
 40 
 
 25 
 
 16 
 
 25 
 
 40 
 
 22 
 
 40 
 
 25 
 
 19 
 
 27 
 
 40 
 
 25 
 
 43 
 
 25 
 
 22 
 
 30 
 
 45 
 
 22 
 
 45 
 
 :» 
 
 19 
 
 30 
 
 45 
 
 25 
 
 46 
 
 ■iO 
 
 22 
 
 34 
 
 50 
 
 22 
 
 46 
 
 30 
 
 24 
 
 36 
 
 50 
 
 2.5 
 
 48 
 
 PRESERVATIVE TREATMENT OF WOODEN POLES. 
 
 Results of an experience with treated poles over n period of 18 years by the 
 American Telegraph (S: Telephone Co. show that the life of poles is materially 
 increa.sed by such action. 
 
 It is believed to be impracticiible to state the magnitude of the increase in 
 life of poles obtained by the use of preservatives, as the increase is dependent 
 upon so many factors. The amount of preservative and depth of imi>regnation, 
 the kind of wood, and the nature of soil are all factors which enter in com- 
 puting the increase of life by using i)reservatives. Therefore, suflice it to state 
 that by using i)reservatives the life of poles, all things being equal, is increased 
 to such an extent that for permanent lines under ordinary conditions the extra 
 co.st occasioned by use of preservative is more than compensated for. Tt has 
 been found tli;il preservatives not only delay the starting of decay but when 
 started tlic decaying effect is n'tarded. 
 
 Of I lie liiclors enumerated above the most inii)ortant oii(> by far is the first 
 one sliown. nanu'Iy, the amoinit of jtreservative per given cubic foot of wood 
 and dei)th of impregnation, and while one of these seems to be dependent upon 
 the other, it will be understood that the result of a heavy coat of pre.servativ*' 
 fin outside is not so eflicient as the same amount forced into the pores of the 
 wood. 
 
 (17G)
 
 Aerial Line Construction. — Chapter 5. 3 
 
 ^here are three methods of iipplyiiii; preservative in use at this time — tlie 
 bnish. the open tantc, and (he i)n'ssure process. With the brusii nictliod the 
 preservative is applied witli a brush, the part of pole to be treated tirst t)ein>; 
 thoroujrhly cleaned. With the open-lank method the pole or butt of pole is 
 immersed in a tank of preservative, the preservative being kept hot until bub- 
 bling caused by air or water in poles ceases. The hot preservative is then 
 allowed to cool, and the vacuum created In the cells of the pole timber while 
 heating assists in drawing preservative into the wood. The penetration with 
 the latter method has a range from one-fourth to one-half inch, while in the 
 former ai)i)r<iximately one-sixteenth to somewhat under one-fourth inch may be 
 obtained. With the i)ressure process a greater penetration is olytaincd. Init ihit- 
 to cost the lii'st two methods are more popular. 
 
 Due to short life of pine poles, both above and below ground, it is believed 
 that such poles should be treated their entire length if anything approaching a 
 permanent line is constructed with such material. The part of any set pole 
 most susceptible to decay is a section from a few inches above ground line to 2 
 or 3 feet below ground line, and where it is impracticable to treat wooden poles 
 thoroughly, treatment of this section will materially add to the life of the poles. 
 
 CONCRETE POLES. 
 
 In the Tropics, and occasionally in other places, it is more advantageous to 
 manufacture reinforced concrete poles for post telephone systems. Concrete 
 poles are not recommended for telegraph lines on account of the difficulty of 
 transportation and delivery along the route. The forms may be easily pre- 
 pared by using 2-inch plank, free from knots, and dressed on one side. Three 
 pieces only are required, the top being left open for pouring the concrete. The 
 forms are held in place by side and toj) cleats secured to prevent tlie form 
 spreading when the concrete is poured. 
 
 The longitudinal reinforcement consists of four .square or twisted steel bars, 
 three-eighths inch bars l)eing about the proper size for 24-foot poles, and one- 
 half inch bars for longer poles. Tlie four bars are set about one-half inch from 
 each corner, being spaced by a piece of wood at each end of the form, with 
 holes to take the ends of the rods. It is also necessary to bind the foiu- rods 
 together by iron wire at four or five points throughout the length. The rein- 
 forcing rods are held in position at various points by wooden blocks or wire to 
 prevent sagging. The.se are removed as the concrete is poured. 
 
 A very wet mixture of concrete should be used, proportioned one part cement, 
 two parts sharp sand, and four parts crushed stone of less than one-half inch 
 size. It is important to have sharp sand. CJravel instead of crushed stone will 
 give satisfactory results, but should be cleaned well. The side walls may be 
 removed the next day after pouring. After the fourth day the concrete is 
 sufficiently set to remove the pole from the bottom form by sliding it endwi.se. 
 using heavy ice tongs. A small anioimt of troweling is necessary to finish up 
 the surfaces before the concrete is entirely set. The pole should be allowed to 
 cure about 30 days before use. Wooden pins should be placed in the form be- 
 fore pouring the concrete, for bolt holes and pole steps, if they are desireil. 
 
 Concrete poles having a length of 24 feet should be about 8 by 8 inches at the 
 base and 5 by 5 inches at the top. Beveled corners improve the appearance. 
 Twenty-four-foot poles weigh approximately 1,100 pounds, and 30-foot poles 
 1,400 pounds. Twenty-four-foot poles should be set approximately 4 feet in 
 the ground, and 30-foot poles approximately .t feet in the ground. A 24-foot 
 pole having an S-inch square base and a .")-inch square top requires about 7 
 cubic feet of concrete. 
 
 (177)
 
 Signal Corps Manual No. 3. — Chapter 5, 
 
 DIGGING HOLES. 
 
 The depth to which poles should be set depends upon the character of the 
 soil in which they are placed, the height of the pole, and the load it is to carry. 
 In rock, gravel, or stiff clays a less depth is sufficient than in light loam or 
 sand. The following table gives the depths for average conditions: 
 
 Length of Depth in 
 pole. groimd. 
 
 Depth in 
 solid rock. 
 
 Feet. 
 
 IS 
 
 20 
 22 
 25 
 30 
 35 
 40 
 45 
 50 
 
 Feet. 
 ( 13 
 I 2 3* 
 
 4 
 
 5 
 
 5?. 
 
 6" 
 
 6 
 
 6^ 
 
 7 
 
 Feet. 
 
 } ^ 
 
 3 
 3 
 3 
 
 3h 
 4 
 4 
 4i 
 
 4 
 
 1 On straight lines. = On comers. 
 
 A foreman follows v.-ith a sufficient number of men equipped with digging 
 bars, spoon sliovels, the ordinary long-handled shovel, or post-hole diggers, 
 where the soil will admit of their use. This party digs the holes for the poles 
 as marked out by the stakes. If there is a sod, one of the men, equipped with 
 an ordinary spade, may be sent ahead to remove it, indicating the size of the 
 hole to be dug and facilitating the work by performing a part thereof for which 
 the bars and spoons are not well adapted. The foreman must see personally 
 that the holes are put down to the proper depth. He will have direction of the 
 force and be held responsible for good service. For poles at crossings, curves, 
 and long spans the holes must be dug to a depth corresponding to the strain to 
 be brought upon them. 
 
 POLE SETTING. 
 
 All pole holes should be dug large enough to admit the pole without the 
 necessity of cutting away the butt and should allow space to move the pole 
 alKiut for bringing it into line. Tlie size of tlie bole .'should be such that the 
 tamping bar may be used full depth. This matter of thorough tamping as the 
 hole is filled is imi)ortant to the proper .setting of the pole. On straight lines 
 the cross arm should be placed at right angles to the direction of the pole line, 
 the arms on adjacent poles facing in opposite directions. At line terminals the 
 cross arms on the last two or three poles should be placed on the sides of the 
 poles which face the terminal. On curves the cross arms should be placed on 
 the sides of the i)oles wliich I'ace the middle of the curve. On straight lines 
 the poles shall be set vertically. It is advisable that the corner poles shcmld 
 be given a slight rake when set. varying with conditions, from 10 to 20 inches. 
 After the pole has been i)laced in position, the hole filled, and the earth well 
 tamped, the soil should be well banked up about the pole and lirnily packed in 
 place. This is to prevent a depression forming about the base of the pole, due 
 to subsequent settling of the earth. In filling holes the coarse material, soil or 
 gravel, should be used at the top of the boles. Where poles are set in rock, the 
 pieces should ]w wedged in firmly about the jjole. It will usually be foun<l that 
 there are ir)ore or less pronounced cm'ves in all wooden poles. When setting 
 the poles these curves should be so placed ;is to be least api)arent when vicwt'd 
 from the direction of the line. 
 
 (178)
 
 Aerial Line Construction. — Chapter 5. 
 
 5 
 
 In grading poles to obtain uniform lielj^lit of lea<l it is proper to cut tlie pole 
 as a last resort only when shorter poles are not at hand. If the difference in 
 height is only 1 or 2 feet, it may be taken care of by digging the hole deeper. 
 When necessary to cut a pole the top. and not the Initt, should be cut. 
 
 NUMBKK OK POLES. 
 
 The number of poles to be provided depends upon the character of the coun- 
 try and upon the number of wires or cables to be supported. No less than the 
 equivalent of 3") poles per mile mu.>*t be used; but in timbered country, with 
 crooked roads and heavy leads, it may be necessary to increase this number to 
 45 or even more in si)ecial cases. 
 
 DELIVERY OF POLES. 
 
 The poles should be delivered as soon as practicable after the holes have been 
 dug, with the butt of the pole by the hole and the top in the direction from 
 which the raising party will come. No equipment is necessary for this labor, 
 except the means used for the transportation of the poles and carrying hooks 
 with wbicli to move them as required after unloading. For crossings and long 
 spans the heaviest and longest poles should be selected ; for angles and sharp 
 curves, select the stoutest. 
 
 PREPARATION OF POLES. 
 
 When practicable, the poles must be cut when the sap is down, and the 
 bark removed, and allowed to season before they are placed in the line. This 
 increases the durability of most kinds of poles and facilitates their transporta- 
 tion and erection. The tops of the poles should be roofed, as shown in figure 
 ")-!, so that they will elTectively shed rain and snow. 
 
 LIGHTNING RODS. 
 
 A lightning rod is sometimes provided for every fifth to tenth pole of all 
 aerial lines. This rod may consist of a piece of No. 6 galvanized-iron wire 
 extending not less than 12 inches above the roof of the pole and attached to 
 the sides thereof by means of staples, ubout 1 foot apart. The lightning rod 
 should extend continuously down the entire length of the pole, and may be 
 soldered to a ground rod driven into the earth near the base of the pole or 
 may be continued to the base of the pole and there end in a small coil of wire, 
 to give good surface contact with the earth. This wire should be kept as 
 straight as possible without turns or coils in irs length and should be installed 
 before the pole is erected. 
 
 CROSS ARMS. 
 
 The standard cross arms supplied by the Signal Corps are indicated in the 
 following table: 
 
 IHnicnsions of staiulanl (■n>s>< nniis. 
 
 (179)
 
 6 Signal Corps Manual No. 3. — Chapter 5. 
 
 FKAMING POLES. 
 
 All poles supporting cross arms should be framed in the following manner: 
 Raise the pole at the top and place it in a framing buck or horse so that the 
 heaviest sag or curve will be nearest the ground. If the pole be crooked or 
 badly shaped, it should be turned with a cant hook until the best side for 
 framing is uppermost and the pole held rigidly in place. In this position the 
 pole should be roofed. After the rooting has been done, the gains should be 
 cut. These may be leveled with a straightedge or sighting stick. To bore 
 holes for cross-arm bolts, a line should be set off from the center of the top 
 of the pole to the center of the butt and the bolt-hole center laid off along this 
 line. A half-inch hole for steps niay be bored at right angles to the line or 
 in line with the cross arms, beginning 18 inches from the lowest cross arm 
 and continuing 18 inches apart or 36 inches apart when measured on the same 
 side of the pole until a point 8 feet from the ground is reached. 
 
 ..i^.^.l 
 
 
 It'-A ^-A^-i 
 
 •«"'■"■" 
 
 (g]|..^.„-v,. y^f^- 
 
 
 
 '/ 
 
 \i''*i 'log icrew 
 
 FOUR PIN ARM ON WOODtN POLEL 
 
 TWO PIN ARM AND BRACKET 
 ON WOODEIN POLE 
 
 IRON ARM ON STEEL POLE 
 
 WOODEN ARM ilON STEEL POLE 
 
 Fig. 5-1.— AERIAL LINE CONSTRUCTION, PREPARATION OF POLES. 
 
 All (TOSS arms fur carrying four wires and upward must be brai-ed. (Fig. 
 ."(-1.) (Jains lor cidss arms will not e.xceed in any case 1^ inches in depth. 
 
 The (lisliiiicc Iroin (he uiiper side of the top gain to the extreme top of the 
 pole will !((• s iiichrs, and the (listanc«> bclwceu gains from center to center 
 li feet. Cross-arm braces slioidd be attached t(» the face of the pctle and to the 
 face of the arm. Two lag bolts will be use<l in all cross arms which are not 
 braced. Cross arms must be j)laced on opi)osite sides of alternate i)oles, except 
 wiiere sjiiM-ial conditions of line wires may re(|uire (»therwise. 
 
 Cross arms should Ik- set at right angles to the pole length. This applies 
 as well to <"orner poles, no matter what the degree of rake. 
 
 (180)
 
 Aerial Line Construction. — Chapter 5. 7 
 
 Cross-arm fixtures sliould. if inacticahU', he iittaclicd lo buildings (other 
 than residences) with holts passing tlu'ough the wall. If this is not prae- 
 tical)l(\ large exiiansidii holts shoidd he used. Window casenieiits or wcmdwork 
 of huildings .should never he used for resisting the strain of the line. 
 
 Method of connection 
 for iron iv/re 
 
 SECTION THROUGH CROSS ARMS 
 
 Fig. 5-2.— AERIAL LINE CONSTRUCTION, DOUBLE ARMING. 
 
 Telephone line wires should not he terminated at residences hy means of 
 cross arms. or other type of fixtures attached to walls of residences. The 
 I'eason for this is that great aiuioyance may he occasioned hy the Iium of the 
 line wires. Either outside distrihuting or outside twisted pair wire should he 
 invariahly u.sed for .such connections, the line wire heing terminated at the 
 cross arm or hracket at nearest pole to residence and the service completed hy 
 means of the outside distrihuting or outside twisted pair wire, which may he 
 made fast to residence hy means of a hracket or other type of fixture, and 
 which should enter the residence through two porcelain tuhes. each conductor 
 of the duplex wire entering through one of the.se tuhes. If practicable, the 
 tubes should l)e slanted downward toward the «mtside of the residence in 
 order to avoid water entering the tuhes during stormy weather. If the latter 
 can not he accomplislied, the wires sliould be sagged below the tubes ou outside 
 
 (181)
 
 8 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 of the building, whicli will produce the same result. The latter are termed 
 " drip loops." 
 
 Poles shall, wherever practicable, l)e armed bi'fore they are erected. 
 
 Ih lifiure 5-1 are shown the methods of attaching,' cross arms for leads not 
 exceedinjr four wires, (a) Shows the four-pin cross arm, with braces; (b) the 
 two-pin cross arm attached with lag bolts : while (c) and id) show the methods 
 pursued in the case of steel poles. These steel poles are only used occasionally 
 to meet special conditions, and are not suitable for supporting more than four 
 wires and should only be installed in hard earth or cttncrete. 
 
 Double 07'ms. — The approved method of installing double cross arms is shown 
 in figure 5-2. The poles upon which the double arms are to be placed should 
 )ip selected from the heaviest of those available, as these nuist bear an addi- 
 tional load, and extra strength should be provided. In tigure .5-2 is also shown 
 the method of dead ending wires on doul)le cross arms. Where the wire?; are 
 not dead ended, but pass through, they will be tied to both insulators in the 
 lower groove of the glass if double-groove glasses are in place. 
 
 Porcelain-coated bridle rings may be used for su])porting bridle wire, instead 
 of cleats as shown in figure 5-2, and copper connectors may be used for splicing 
 bridle wire to hard-drawn copper line wire, instead of as shown in the same 
 figure. 
 
 BRACKET LINES. 
 
 Where not more than two wires are required on a pole line, oak brackets may 
 be used in place of cross arms. The brackets should be attached to the pole 
 with one 2(»d. and one 40d. nails and, in general, should oe placed as shown 
 
 BrQcMeta must &• 
 \on outside </cufV9k 
 
 Fig. 5-3.— AERIAL LINE CONSTRUCTION, ATTACHING BRACKETS. 
 
 in figure .5-.3. Where brackets are jtlaced on i»oles, wliicli may b(> used at some 
 biter time to support cross-arms, tiie loii end ol' the br.ickel sliould be ab(»ul 
 level with the correct location ot lo]) of tiie gain, so llial I be i)racket and its 
 wire will not iiitertere with (lie subse(nieiil ust> of the cross arm. 
 
 (182>
 
 Aerial Line Construction,— Chapter 5. 9 
 
 TEKMINAL OR OFKK'K I'OLE. 
 
 Tho toriiiiiiiil or office pole of a line eiirryinj? u nunibei' of wires is the most 
 important part of the line and demands careful attention to secure construction 
 that will be serviceable and easy to maintain. There will be necessity for fre- 
 (lueiit access to this pole, so that all wiring should be substantial in character 
 and arranj^ed to facilitate repairs and extensions. The ofiice or terminal pole 
 shown in tij^ure '>-~> indicates the construction to be followed in the typical case. 
 
 It is probable that the conditions shown in tigure .v.") will not be exactly dupli- 
 cated in any construction work which may be taken uji, but the methods shown 
 should be followed as far as practicable. 
 
 The can terminal shown may be installed or us«» may lie made of a <able box 
 shown in tigure 5-4. The hitter is, in general, considered preferable except in 
 tiie Tropics. In (jrdering these boxes the numb(>r of pairs to be acconuuodated 
 should be st:ited, as well as the number of pairs of lighlning arresters and fuse.s. 
 No aerial line should be cross-coimected at a terminal pole or to a central ex- 
 change except through fuses and lightning arresters. The terminal or cable-box 
 
 SECTIOM OF DOORS 
 
 Fig. 5-4.— AERIAL LINE CONSTRUCTION, CABLE BOX. 
 
 poles should be stepped, using for this purpose galvanized iron-pole steps, a.s 
 shown in figure 5-5. These iron-pole steps should not come do\\Ti to less than 
 S feet from the ground. To reach these steps, use may be made of a ladder, or 
 brackets with the tops cut off may be fastened to the pole for footholds, as 
 shown in figure 5-G. Bridle wires, which are used to connect the line wires 
 with can terminal or cable box, run through hardwood cleats, are shown in 
 ligure 5-2, Particular attention should be given to all wiring about the pole 
 to see that it fits neatly and is so placed that it will not be injured by the 
 workman in the performance of his necessary duties. 
 
 Where the wires which dead end on a double arm lead from one direction 
 only, it will be necessary to counterbalance the strain by running a small guy 
 from this cross arm to the next pole. 
 
 Linemen should not use climbers on poles provided with steps unless such use 
 
 is clearly unavoidable. 
 
 (183)
 
 10 
 
 Signal Corps Manual No. 3.— Chapter 5. 
 
 GUYS AND ANCHORS. 
 
 Wherever a pole line makes a curve, turns a corner, or ends iu an office or 
 other terminal pole, particular attention must be given to the matter of proper 
 
 Fig. 5-5.— AERIAL LINE CONSTRUCTION, TERMINAL POLE. 
 
 euv" an.l anclu.rs. The following- instructions cover the cases usually mot with 
 under ordinary conditions. The various methods shown of strengthening the 
 line should be adapted as occasion i-equires to meet special or unusual cases. 
 
 (184)
 
 Aerial Line Construction. — Chapter 5. 
 
 11 
 
 Ground fine 
 
 Fig. 5--6._AERIAL LINE CONSTRUCTION. POLE STEPS. 
 (185)
 
 12 
 
 Signal Corps Manual No. 3.— Chapter 5. 
 
 Guy stubs and anchor logs.— The timber used for guy stubs and anchor logs should 
 conform in all respects with that specified for poles. Anchor logs should be not less 
 than 24 inches in circiunference nor less than 4 feet in length. 
 
 ^ 
 
 
 i ^ 
 
 a==1 
 
 ^ 
 
 '> '4 
 
 .t=^-^ 
 
 [^ 
 
 
 F & 
 
 -B 1 
 
 »^ 
 
 Head guy from top of pole I to bottom of pole Z 
 and from hop of pole, 4- to bottom of pole 3 
 
 Fig. 5-7.— AERIAL LINE CONSTRUCTION, GUYING AT CORNERS. 
 
 Pig. 5-8.— AERIAL LINE CONSTRUCTION, GUYING AT ROAD CROSSING. 
 
 '.\m)
 
 Aerial Line Construction. — Chapter 5. 
 
 13 
 
 Guy stubs shall be not less than '2'2 inches in circumference. 
 
 The timber to he used for i)oh> liraces shall 1)(' of the same quality as that 
 specitied for poles. Braces should be not less than 18 inches in circumference 
 at smaller end. 
 
 A bracket line or other line supportinj; one or iwo wires will not always re- 
 quire jruys or braces except on corner poles where the anjile witli the straight 
 line approximates 90°, and at road crossings or terminal poles. Where guys are 
 required, it will usually be found that 144 mils diameter iron or steel wire, 
 galvanized, will be sufTiciently heavy, u.sed with a small deadman or 6-inch guy 
 anchor. Curves of less than 45° should be provided for by giving the pole th(j 
 proper rake. 
 
 Fig. 5-9.— AERIAL LINE CONSTRUCTION, GUYING AT CURVES. 
 
 For lines carrying six or more wires all poles which are out of line should 
 be guyed. For a lead of six or less wires, standard guy wire, one-fourth or 
 five-sixteenths inch diameter, will usually be found sufficient, useil with a 6 
 or 8 inch guy anchor or ordinary deadman. 
 
 On lines carrying 10 or more wires guy wire should be not less than three- 
 eighths inch, with not less than one 8-inch guy anchor or usual deadman. 
 
 Wherever a line makes a right angle corner with two poles, the poles should 
 be guyed as shown at .1. figure 5-7. Where it is impossible to place such guys 
 an alternative method shown at B, figure 5-7, may be employed, the line 
 
 4G581°— 17- 
 
 -13 
 
 (187)
 
 14 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 wires between poles 1 and 4 being slack, and the sti'ain of line in both directions 
 being sustained by guys placed as indicated in note. 
 
 On straight roads where the line crosses from one side of the road to the 
 other corner poles should be guyed as shown in figure 5-8. Terminal poles on 
 '20-wire lines should be head guyed, and if practicable side guyed in both direc- 
 tions. When open-wire lines of 20 wires or more are dead ended in one direc- 
 tion only, the pole adjacent to the terminal pole should be head guyed. 
 
 The methods of guying on curves are shown in figure 5-9. 
 
 The above figures showing the methods of guying also indicate the sides of 
 the poles on which the cross arms should be placed under varying conditions. 
 In locating anchor guys the distance from the butt of the pole to the eye of the 
 anchor should be not less than one-fifth the length of the pole and, preferably, 
 should be about the length of the pole. A typical "dead man" with anchor is 
 shown in figure .5-10. 
 
 The anchor rod shown is of five-eighths inch galvanized steel. The rod passes 
 through the anchor log and is held in place by a nut :ind square washer, as 
 shown. The size of the anchor log wili vary with the depth of the excavation. 
 For an excavation of 5 feet in depth the anchor log will be 5 feet long and 8 
 inches in diameter. F'or a shallow excavation a larger and longer anchor log 
 should be used. The anchor log, after being placed in the excavation, should 
 be covered with planking, as shown. If this is not available logs or rock may be 
 used for the same purpose. Guys should be attached to the pole innuediately 
 
 » a a a .f'^a a a « J 
 
 Fig. 5-10.— AERIAL LINE CONSTRUCTION, 
 DEADMAN AND ANCHOR ROD. 
 
 Fig. 5-n.— AERIAL LI NE CONSTRUCTION; 
 METHOD OF GUYING TO ROCK. 
 
 below the upi)er cross arm or the lower brack(>t, as shown al (t, figure 5-11. 
 Wiiere 144 mils diameter or otiier solid wire is used for guy.s, the wire should be 
 fastened at either end by wrapping the end about the main wire. Where 
 sli-anded wire is used, the guys shcnild be fastened at each end by means of an 
 approved form of guy clamp, either two or three bolt. A thimble should be 
 used for attaching the guy to the guy bolt or guy rod. The end of the wire 
 sliould be attached to the stub or pole and wrapped twice about this, the wrap- 
 ping being held in place on the pole or stub by a staple, lag .screw, or heavy 
 nail. 
 
 (188)
 
 Aerial Line Construction. — Chapter 5. 
 
 15 
 
 The attachment of guys to tree trunks is permissible, although when this is 
 resorted to specific permission for using the trees must invariably l»e ol)taine(l. 
 In attaching guys to tree trunks, a hole slightly larger than tlie five-eigiiths inch 
 guy rod sliould he tlrilled directly through center of tree, a short distance from 
 ground. This distance is dependent upon the size of tree, as with a compara- 
 tively small tree the swaying of the tree is apt to loo.sen line if guy is attached 
 a considerable distance from ground. Square washer and nut should be placed 
 on giiy rod, and by means of a ball hammer the rod should be headed over in 
 order that nut can not readily be removed. The guy is attached to eye of 
 guy rod in the usual manner. 
 
 When it is necessary to attach a guy to solid rock, tiie method shown at b 
 of figure 5-11 should be followed. 
 
 It may be found necessary in some cases to substitute pole braces for the guys 
 shown, although the former are not considered as desirable a reinforcement as 
 
 a aAs a a 
 
 3 1 nW 2 wra pa 0* ^ atrao^ 
 
 Fig. 5-12.— AERIAL LINE CONSTRUC- 
 TION, POLE BRACE. 
 
 Fig. 5-13.— AERIAL LINE CONSTRUCTION. 
 GUYING ACROSS ROAD. 
 
 guys. Where pole braces are used, the butt of the brace siiali b.> .spt at least 
 31 feet in the ground, on a firm support of planking, stone, or similar material. 
 An approved method of installing pole braces is shown in figure 5-lL». 
 
 Where it is necessary to raise guys over roadways or to clear obstacles, guy 
 stubs should be employed, as shown in figure 5-13. The stubs shoultl have a 
 top circumference of not less than 18 inches and should be set in the ground to a 
 depth of at least 5 feet, and should lean away from the pole to which the guy is 
 attached. 
 
 In general practice two turns of the guy should be made around each pole, one 
 end of the block attached to the body of the messenger or guy and the other 
 attached to the free end, the fall of the blocks passing back and down to the 
 
 (189)
 
 16 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 ground over a convenient stub or snatch block. All anchor guys, head guys, and 
 corners should be pulled with two sets of guying blocks, one being used as a luff 
 for the other set. 
 
 GUARD WIRES. 
 
 Where guard wires are necessary to protect wires from other wires crossing 
 above, they will be put up as described and illustrated below. Referring to 
 figure 5-14, poles 1 and 4 should be framed so as to leave 1 foot of the pole above 
 the top arm. Poles 2 and 3 should be framed in the regular way, with pin in 
 ends of arms, as shown in sketch. The upper wires represent guard wires, 
 which should be of 144 mils diameter galvanized iron where the crossing is 
 
 12 3 4 
 
 Fig. 5-14.— AERIAL LINE CONSTRUCTION, GUARD WIRES. 
 
 under low-tension wires. Where the crossing is under high-tension wires, stand- 
 ard guy wire or 229 mils diameter wire should be used as guards. 
 
 The guard wires terminate on the top of poles 1 and 4, where heavy porcelain 
 kn(>l)s or other circuit breaks should be used when the crossing is under high- 
 tension wires. The straight lines show the working wires as they will appear 
 after guard arms and wires are up. 
 
 Wliere crossing under a heavy lead and heavy guard wires are use«l, guy wires 
 should be run from the top of poles 1' and 4 to a i)oint S or more feet from the 
 butt of the next pole to hold the strain of the guard wires. 
 
 INSULATORS. 
 
 The standard insulator is the pony-porceliiiii insulator, double groove. Special 
 cases may require the use of a heavier insulator, but in general the above type 
 will be found suitable. 
 
 HTRINOING WIRE. 
 
 After the pole line has been completed, with all guys, anchors, etc., in place, 
 the stringing of the wire .should next be taken up. The working party for 
 this purpose will comprise a foreman; a suthcient number of lin^'uien, varying 
 from two to six ; one or two groundmen ; and such means of transportation 
 
 (100)
 
 Aerial Line Construction. — Chapter 5. 
 
 17 
 
 as may be necessary. The linciiu'ii arc ('(luiiiiicd witli tools for sfdicinK wire 
 and for attai-liiii;^ it t(» tiic insulators and nuist be men who are able to 
 elinib itoles and work to advaiitaf^e thereon. 
 
 No. 14 B. W. f^au^e (81 nnls diameter) j?alvanizeU-iron wire is sometimes 
 furnished for temporary local battery telephone systems. For connnon bat- 
 tery telephone work No. 12 B. & S. gauge (81 mils diameter) hard-drawn 
 bare copper wire is furnished. This wire is supplied in coils of 1 mile and 
 should be handled with extreme care to avoid bruising or scratdiing its sur- 
 face. Any scratch or bruise made should be cut from the wire before it is 
 installed. Splices should invariably be made with copper splicing sleeves fur- 
 nished especially for this pur])ose. Line splices should not be soldered. 
 
 All line wire shall be strung from pay-out reels in such manner that it shall 
 be free from kinks or twists. For copper wire, ButTalo grips should be used 
 so that it will not be injured. For galvanized-iron wire, either a Buflalo 
 grip or other form of clamp may be used. Wires are to be strung with a 
 uniform sag, so that all the wires on a cross arm shall be even. (See tabic 
 below.) For short iron-wire lines, and for copper wire, joints need not be 
 st)ldered. Iron wire should be tied in with soft iron wire of the same size 
 as the line wire. Copper wire should be tied in with pieces of soft copper 
 wire of the same size as the line wire. 
 
 Sac/ of aerial-line wires. 
 
 Temper- 
 
 60-foot 
 
 80-foot 
 
 100-foot 
 
 120-foQt 
 
 140-foot 
 
 160-foot 
 
 180-foot 
 
 200-foot 
 
 ature. 
 
 span. 
 
 span. 
 
 span. 
 
 span. 
 
 span. 
 
 span. 
 
 span. 
 
 span. 
 
 ° F. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 - 30 
 
 0.6 
 
 1.1 
 
 1.9 
 
 2.8 
 
 3.9 
 
 5.1 
 
 6.5 
 
 8.0 
 
 - 10 
 
 .8 
 
 1.5 
 
 2.3 
 
 3.3 
 
 4.5 
 
 5.8 
 
 7.4 
 
 9.0 
 
 -1- 10 
 
 1.0 
 
 1.7 
 
 2.6 
 
 3.8 
 
 5.1 
 
 6.6 
 
 8.0 
 
 10.4 
 
 + 30 
 
 1.1 
 
 2.0 
 
 ,3.1 
 
 4.5 
 
 6.1 
 
 7.9 
 
 9.4 
 
 12.0 
 
 + tiO 
 
 1.6 
 
 2.7 
 
 4.2 
 
 5.9 
 
 7.8 
 
 10. 0" 
 
 12.0 
 
 15.4 
 
 + 80 
 
 2.1 
 
 3.7 
 
 5. 6 
 
 7.9 
 
 10.2 
 
 12.7 
 
 14.9 
 
 19.0 
 
 -hlOO 
 
 2.9 
 
 .5.0 
 
 7.2 
 
 9.9 
 
 12.6 
 
 15.6 
 
 1S.0 
 
 22.4 
 
 Having provided the working force with the necessary tools, a coil of wire 
 is placed on a pay-out reel, the binding wires removed, and the outer end of the 
 wire attached at the .starting point. The wire on the reel is then carried along 
 as near the line of poles as possible, so that the wire will run out straight and 
 in a convenient position for carrying up. When a sufficient amount of wire 
 has been run out it is carried up by the linemen and placed in a loose tie on 
 the insulator. The groundmen then i)ull the wire up to the proper tension, after 
 which the tying in is completed. 
 
 The method just described of paying out wire is applicable for construction 
 of new line where there is no danger of interfering with trafhc or having the 
 wire injured. When additional wires to an existing aerial line are run, it is 
 u.sually advisable to have the pay-out reel stationary. In such cases the wire or 
 wires (a numl)er can be pulled at one time, a pay-out reel l)eing supplied for 
 each line) are attached to a long lead rope which is carrie«l up and passtnl 
 over the cross arms. The latter method is also applicable in the construction 
 of new line when it is imprudent to have wire lie on the ground. 
 
 Where more than one wire is pulled by means of the latter method the wires 
 should be made fast a short distance apart to a light, strong piece of wood 
 termed a " spreader " and the lead or jiulling rope made fast to tlie center of the 
 spreader. 
 
 (191)
 
 18 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 HANDLING HARD-DRAWN COPPER WIRE. 
 
 While hard-drawn copper wire possesses hardness and strength for all prac- 
 ticable purposes, it will not stand without injury the rough handling to which 
 iron wire is ordinarily subjected. ' 
 
 Fig. 5-15.— AERIAL LINE CONSTRUCTION, WIRES ON INSULATORS. 
 
 Every coil should be examined before the outside cover is removed. In case 
 the covering is torn, the wire itself should be carefully inspected to see that it 
 has not been cut or bruised. In case the wire is found to have been injured, 
 the injured portion should be cut out befoi'e using. 
 
 Fig. 5-16.— AERIAL LINE CONSTRUCTION, WIRES ON INSULATORS, CORNER POLE. 
 
 Copper wire sliould never be thrown from an appreciable height. 
 
 While unreeling, great care must be taken to avoid twists and kinks. Where- 
 ever either is found, it mu.st be cut out and a good splice made. This applies 
 also to splits, bruises, or indentations of any kind. 
 
 Top'i'ieyv of tie without insulator 
 
 Commencing tie - Ready lor cropping 
 
 Fig. 5-17.— AERIAL LINE CONSTRUCTION, TYING H. D. COPPER WIRE TO INSU- 
 LATORS. 
 
 (192)
 
 Aerial Line Construction. — Chapter 5. 
 
 19 
 
 111 tyiii;: the wire, caic niiist Ix- used ii<>i lu lie ii su t!::lit as to crjiiiiii <»r kink 
 it l)ot\v('('n tli«' tic wire ami tlic ;ilass. Hard-tliaw ii ccipiM-r \vii-c must not In- 
 tied with any wire oIIht tiian soft copix'r. 
 
 ^^■Il('ll oiKc liai'd-drawii (•(•iipcr wire is can'ruliy jtnt in iilacc witlioiit kinks, 
 imleiitations. or hniisos it will stand dianf^es of temperature, sleet storms, etc., 
 practically us well as iron or steel wire of niucli lower conductivity. 
 
 4^>^ 
 
 ^^j;^'^^ 
 
 No tie must have feyver than 5 tarn5 
 
 M^^^^^^^m- 
 
 Splicing iron or steel wire 
 
 "mooa 
 
 Tying with iron or steel wire 
 Fig. 5-1 
 
 Dead ending iron or steel wire 
 
 AERIAL LINE CONSTRUCTION, TYING AND SPLICING IRON AND STEEL 
 WIRE. 
 
 For straight lines, the wires should be placed on the insulators as shown in 
 figure 5-15. It will be noted that all wires are on the pole side of the insulators, 
 except the middle pair, which is placed on the outer side to provide a greater 
 separation. On corner poles all wires should oe placed as shown in figure .>-lC>. 
 
 The approved methods of tying the line wires to the in.sulators are shown in 
 figures 5-17 and 5-18. It will be noted that the methods for iron and cojjper 
 wires are different. Soft copper ties should be used for coi)per and soft iron 
 for iron or steel line. Care should be taken not to injure the wire in tying to 
 insulator, and at the same time a secure fastening should be made. 
 
 TKA.NSl'OSniOX. 
 
 It may he found nece.ssary in some eases to transpose a metallic circuit to 
 prevent cross talk between telephone lines or interference' from foreign circuits. 
 Where it is necessary to transpo.se, the method shown in figure 5^19 should be 
 followed. 
 
 Ftg. 5-19.— AERIAL LINE CONSTRUCTION, LINE TRANSPOSITION. 
 
 (193)
 
 20 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 Til making a transpdsition the use of coriuM- pdles or curves should l)e avoided 
 as far as practicahle. 
 
 On h>ng lines it will l)e found coiiveH'u'nt lo have a test station where the line 
 may be opened and tested both ways for the location of trouble. A form of test 
 .station made on a two-piece transposition insulator is shown in tiiiure 5-20. 
 
 RIVER CROSSINGS. 
 
 When navii:cahle streams cross the routi" of the line, it is usually the lietter 
 plan to use submarine cables, except where they are liable to be washed out 
 l»y freshets; but if this method l)e for any reason impracticable, elevated sup- 
 ports nuist be used and the wire suspended above dani^er from passing vessels. 
 Natural supports, such as trees well rooted in safe positions, if sucli can be 
 found of sufticient height, may be used, or masts erected and securely stayed 
 with wire or wire-rope guys. If the span between supports be not more than 
 1,500 feet, the line wire can be used, care being fallen to select the best, and a 
 
 Test connecter- 
 
 Fig. 5-20.— AERIAL LINE CONSTRUCTION, TEST STATION. 
 
 length without .joints or with joints very carefully made. For greater spans a 
 steel wire (or compound wire having a steel core) is necessary, with which 
 spans upward of 2.000 feet can l)e made, provided the points of support are high 
 enougli to allow of a proportionately deep sag to the wire. Extreu'e care must 
 be given to such crossings <an(l too great strain avoided. For further informa- 
 tion and illustrations relative to river crossings, tlie reader is referred to the 
 subject of "Long Sjians" appearing later in this chapter. 
 
 I, INK COXSTKrCTION TOOLS AXI) M.\TKUI.\L. 
 
 For complete lists of- line-construction tools and line-construction niaterial, 
 see chapler S of iliis nininial. In submitting reciuisition these lists should be 
 followed as closely as i)ossible. as the items listed therein are usually in stock 
 at supiily <lei><'ts or may be pur<-hased in ojten market without appreciable 
 delay. 
 
 Pole lines for aerial cable should lie built as specitied for oi)en wire lines in 
 the i»receding jiaiM of this chapter. The setting and guying of jxdes should be 
 given special attention, and at corners and terminal poles il is of tirst im- 
 jiortance tlial the poles hold their original positions rigidly if the cable is to 
 remain in a neat and workmanlike manner after ert'ction. After the erection 
 
 L" torpolc^ IO"orlc5'i indiam. 
 ■ lO'to 15' ■ - 
 
 Fig. 5-21.— ATRIAL LINE CONSTRUCTION, DE^D ENDING MESSENGER. 
 
 (104)
 
 Aerial Line Construction. — Chapter 5. 
 
 21 
 
 (if llio i>(»l(' line lins Ih'cii ((iiniilctt'il. with :ill ^'iiys, iiiicliors. rtc, installod, the 
 iiicsscn^itT win^ slioiild lie civctcd. Nn( sinjilh-r lliiiii I lir»'<--»'i;rlitlis inch strand 
 sliould Ik' used for nii'sst'n;;or. Tlie same size of strand that is usrd for carry- 
 ini; the (•al)U* shouhl also he us»>d fur ;-'uys. Tiic proiicrtit's of various sizes of 
 strand are i^iven in the folluwin}; table: 
 
 Breaking 
 
 strain. 
 
 Diameter 
 of strand 
 in inches. 
 
 Lav in 
 in('he,s. 
 
 KIont;ation of each wire 
 in 10 inche.s. 
 
 Weight per 
 m) feel. 
 
 ! 
 Maximnm. Average. 
 
 Pounds. 
 11,000 
 9,000 
 6,800 
 4,860 
 3,050 
 2,000 
 
 1 
 
 X 
 
 i 
 rs 
 
 4i 
 
 ^ 
 
 4 
 
 ■iK 
 3 
 . 3 
 
 Per cent. 
 13 
 13 
 13 
 
 12 
 12 
 10 
 
 Per cent. 
 11 
 
 11 
 11 
 
 9 
 
 9 
 
 9 
 
 Pounds. 
 52 
 42 
 30 
 22 
 13 
 8 
 
 An approved method of dead ending messenger wire i.s shown in figure 5-21. 
 
 It is desirable to have the messenger installed without splii-e, also to continue 
 it past la.st pole without change of level, to a guy stub. Tlie terminal pole and 
 stub are then guyed, as shown in figure 5-22. 
 
 Fig. 5-22.— AERIAL LINE CONSTRUCTION, DEAD ENDING MESSENGER, GUYING. 
 
 Whenever possible, the anchor for the stub should be placed at a distance 
 from the stub equal to the distance from the guy to the ground level. Tiiis will 
 give the anchor guys an angle of about ».'> degrees. On all poles or stults where 
 
 Fig. 5-23.— AERIAL LINE CONSTRUCTION. SHIMS AND CLAMPS. 
 (195)
 
 22 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 extra heavy steel strand or niessenisrer tU'iul ends or extra heavy guys are 
 installed, metal guy shims should be used as shown in figure r»-23. 
 
 Thimbles should be used in the eyes of all anelior rods. 
 
 Splicing of messenger should be avoided if possible l>ut when necessary may 
 be done as follows : Two ends of the messenger should be lapped about 6 feet. 
 Three 3-bolt clamps should be put on in the center lapping .sections, spacing 
 them so that they touch end to end. At each end of the outside of the three 
 clamps one Crosby clip should be placed li inches from the three clamps with 
 tlie yoke over the short end of the messenger and the bearing plate on the main 
 
 Detail of overlap serve 
 
 Fig. 5-24.— AERIAL LINE CONSTRUCTION, SPLICING MESSENGER. 
 
 mes-senger. The end should be served up with overlapping sections of serving 
 as shown. The completed splice is shown in figure 5-24. 
 
 Various methods of attaching the messenger to poles are used. Messenger 
 supports attached with two lag bolts placed as shown in figure 5-25 are most 
 commonly used. 
 
 A messenger support as shown in figure 5-26 attached by a through bolt may 
 also be used. In ordering supports of either pattern the size of the strand with 
 which they are to be used should be stated. Bolts for attaching are not fur- 
 nished as a part of the supi:)ort and should be ordered separately. The mes- 
 senger supports should be installed before the strand is run out. To erect 
 strand, place the reel on an axle supported by two jacks, if available, and run 
 off the required length along the line as near the poles as possible. This is then 
 carried up the pole by the linemen, the hangers being already in place. One end 
 is then dead ended, as shown in figure 5-21. At the other end a pair of 6-inch 
 triple blocks should be hung on the guy stub terminating the pole line, and slack 
 pulled out of the messenger and <anied around llie pole loosely and fastened 
 with a clamp for safety. Next, a l(i-iii<li snaldi block is hung Just below the 
 guy shims on flio side of the jiole iiarallel willi tiic sIi'itI. It should be secured 
 to the pole with the equivalent of four turns of inch roi)e. A piece of three- 
 eighths inch strand measuring KM) feet or m(»re should be attached to the mes- 
 senger by means of Crosby clips or three-bolt guy clamps in a j)ermanent man- 
 ner, approximately 15 feet from the stub. Tlie i)iece of strand attached to the 
 
 Fig. 5 25.— AERIAL LINE CONSTRUCTION, 
 MESSENGER SUPPORTS. 
 
 Fig. 5-26.— AERIAL LINE CONSTRUC- 
 TION. MESSENGER SUPPORT. 
 THROUGH-BOLT TYPE. 
 
 <19«)
 
 Aerial Line Construction. — Chapter 5. 
 
 23 
 
 messenger s^hould now be carried thrnuj,'li tlio siiatdi lilock to the butt of the 
 next pole, a tree or other sufliciently firm object. A i»air of lo-inch Iriple-shoave 
 hoistins lilocks shouhl be made fast to this pole or (»ther object and lashed with 
 two turns of inch rope or its equivalent. These blocks should be attached to 
 the strand leading over the snatch block with tlie blocks spread at least 30 
 feet. A pair of luff blocks should be attached to the fall of the main blocks by 
 a stopper hitch, allowing the main fall to be snubbed around the nearest s«»lid 
 support. The slack should now be pulled up by the fall (»f the luff blocks, using 
 for this purpose a horse or force of ground men. The arrangement of block atnl 
 tackle described is shown in figure 5-27. 
 
 Fig. 5-27.— AERIAL LINE CONSTRUCTION, ARRANGEMENT OF TACKLE. 
 
 "When the desired tension has been obtained, the main fall should be per- 
 manently snubbed and the messenger made fast. This is done by passing th»' 
 end twice around the pole, the free end hooked to one end of a i)air of 0-inch 
 triple block.s. The other end of the.se blocks should be secured to the main mes- 
 senger. The fall of the.se blocks should be carried through a second and smaller 
 snatch block to the ground, where it may be handled with other luffs to take 
 out the slack in the messenger. 
 
 When this is done, the messenger is secured by Crosby clip and 3-bolt guy 
 clamp, as shown in figure 5-21. The tension of the main blocks should be eased 
 otT gradually and with caution until the dead end of the me.ssenger has taken up 
 the full strain. This having been ctnupleted, the nies.senger supports shouhl be 
 tightened up on each pole. 
 
 The method of putting up messenger just described is of -general api>iitation 
 and will be found suitable for the heaviest strand installed. 
 
 The messenger should never turn double corners or change from one sido of 
 the street to the other by being pulled around the corner. (Hi double corners, 
 messenger and cable sliould make the square tiu-n, as shown in figure 5-2S. On 
 changing sides of the street the messenger shoidd terminate at last iM)le, begin- 
 ning again on the opposite side of the strtvt. both corner polfs being siile guyed 
 as well as lieud guyed. 
 
 (19T)
 
 24 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 Wlien the cable is in place on the messenger the sag in inches should not 
 exceed the limits of the following table : 
 
 Temper- 
 
 100-foot 
 
 120-foot 
 
 140--foot 
 
 160-foot 
 
 180-foot 
 
 200-foot 
 
 ature. 
 
 span. 
 
 span. 
 
 span. 
 
 span. 
 
 span. 
 
 span. 
 
 °F. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 -30 
 
 12 
 
 17| 
 
 23i 
 
 30J 
 
 39 
 
 48 
 
 
 
 12J 
 
 17* 
 
 24 
 
 314 
 
 40 
 
 49i 
 
 +30 
 
 12-J 
 
 ISJ 
 
 25i 
 
 :«i 
 
 421 
 
 521 
 
 60 
 
 13.} 
 
 20 
 
 27f 
 
 36 
 
 451 
 
 5i>i 
 
 90 
 
 15i 
 
 22 
 
 30 
 
 39i 
 
 50i 
 
 63 .\ 
 
 IL'O 
 
 18 
 
 2o.V 
 
 m 
 
 421 
 
 55 
 
 67i 
 
 When pulling the strand taut allowance should be made for the weight of the 
 cable, which will increase the sag, and the strand should lie made correspond- 
 
 ^ 
 
 Fig. 5-28.— AERIAL LINE CONSTRUCTION, CHANGING DIRECTION OF MESSENGER. 
 
 ingly taut. It will hardly he possibl(> to place tlic^ strand under too great a 
 tension. As the strain is ai>plii'd. caicrul wnl'.-li slioidd Ix' kept for loo.senlng 
 guys or anchors, buckling of poles, etc. The blocks should Ite attached to the 
 messenger wire by means of steel comealongs rather than buffalo grips. They 
 may be attached to the jxilc or aiii-liofngo by the use of a sling of messenger 
 strand or manila rope. 
 
 c.rvs. 
 
 If a single messenger wire is used on a universal hanger, the pole guys should 
 be placed aiiovo and as close to (he iiiesseugei' as jxisible. Tlie guys shoulil be 
 wrapped twice nlioiil I lie pole or guy sluli. and sliould be held with guy clamps. 
 
 Where several guys ;ire placed >\\v pole lliey sliould be assembled as 
 
 clo.sely as iMtssihle. Iml should uo| oxcrlap or hind encli olliei'. When head guys, 
 storiu guys, slrniid or other guvs are fastened 1o Hie butt of llie i>ole. they 
 should lie as close |o 1 he ground as practicable, hut usually not nearer than H 
 feet. Cuy stubs slioidd not be left with any side strain whatever. This can be 
 jtrevenled in two ways — liy side guying the stub ilsi'lf or by bringing tiie anclior 
 rods, stub, and j)oiul of strain in line. 
 
 (198)
 
 Aerial Line Construction. — Chapter 5. 25 
 
 Cable raessengers should be carried at the lowest level permitted by existing 
 conditions, such as other wires, cables, roadways, etc. The height of the 
 main-cable lead should be adjusted, if possible, to meet the requirements of 
 the branch or cross lead. If the level of the cable messenger is to be changed, 
 it should not be dropped abruptly, but should be carefully graded to meet the 
 requirements. 
 
 In serving dead ends of messenger sufficient length slmulil be left in the 
 messenger or guy to pass twice around the pole, to permit of the proper dis- 
 tance between the end of the clamp and pole, and to allow a standard length 
 of 18 inches from the clamp to the free end of the strand. This free end 
 should be carefully tightened and served to main messenger with wrapping 
 of 81 mils diameter iron wire. Where several messengers or guj'S dead end 
 on the same pole the ends and serving should be lined up. 
 
 If after the slack has been pulled out of a messenger it ajipears that the 
 grade nnght have been better, it should be considered of sufficient importance 
 to raise or lower the support or supports necessary to bring this about. If the 
 conditions are favorable, cable supports may be placed on the poles by tape- 
 line measure from the ground to determine the height. If, however, the ground 
 is uneven or the conditions are otherwise unfavorable small pieces of lath or 
 e(iuivalent may be tacked on the pole and raised and lowered until a satis- 
 factory grade is secured, the messenger supports then being placed at these 
 points. The preliminary pull on the messenger will determine the correctness 
 of the height of the supports. 
 
 Cable installed aerially is almost invariably i)aper insulation plain lead 
 covered. 
 
 CABLE HANDLING. 
 
 Great care should be exercised in handling cable, in transporting it to the 
 work and in delivery from railroad yartls to storehouses. Cable should never be 
 dropped from a platform or wagon, and the reel should never be turned on its 
 end. Reels will usually be marked on the end with a heavy arrow showing the 
 direction in which they should be rolled. The loading or unloading of reels 
 should be under the supervision of a responsilile party ^^■ho understands the 
 handling of cable. 
 
 HANGING CABLE. 
 
 The messenger having been prepared for th'_> cable, galvanized-iron rings, 
 which are used in the latest approved method of suspending cable, are clamped 
 tightly to messenger, spacing them 1.5 to 18 inches apart. The reel of cable 
 should be placed approximately one .span from the beginning of the run and 
 supported on cable-reel jacks. A temporary leading-up guy equipped with 
 rollers should be placed in position. A drag line for pulling the cable should 
 be brought through the rings from the distant end of the run and attached to 
 the cable by suitable means, such as a cable gi'ip. The cable may then be 
 pulled through the rings by means of a team of horses, winch, or a force of 
 grouudmen. It may be necessary to arrange the galvanized-iron rings after 
 cable has been pulled, as one or more of the rings are apt to slip out of place 
 along messenger during process of pulling cable. 
 
 When marline hangers are used they are made fast to cable as it leaves the 
 reel by means of the marline and are hooked to messenger by means of gal- 
 vanized-iron hook which forms a part of the hanger. When the cable is pulled 
 the hooks slide along the messenger. It is necessary to unhook from me.^senger 
 at each pole and rehook on other side. For this reason all hangers are not 
 
 (199)
 
 26 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 Fig. 5-29.— AERIAL LINE CONSTRUCTION. INSTALLATION OF FUSED CAN 
 
 TERMINAL. 
 
 (200)
 
 Aerial Line Construction. — Chapter 5. 
 
 27 
 
 hooked until (lie pulliiij,' of stivt<'li is nearinj; completion or is foniiilclt'd. 
 When the pulling is completed all hangers are spaced equiilistant and hook<'<i 
 to messenger. 
 
 PROTKCTION or CABLK. 
 
 Where cahle is lial)U' lo come into contact with wires, tree limhs, guys, or 
 other objects which will injure the lead sheath, a guard of wooden strips should 
 be put on and lashed with marliiu>. Tump log sidit lengthwise is sometimes 
 used for this purpose. 
 
 CABLK-BOX UKOUNU. 
 
 Arrester ground lor < alilc terminal poles should be carried straight down thp 
 l)ole. without curves, sharp turns, coils, or splices. This ground should consist 
 of a copper wire of suit:d>le size attached to a gnmiid plate, coil of wire, or 
 ground rod buried pernianeutl.v in moist earth. 
 
 I.AI'FING FOK SPLICING. 
 
 Three feet of lapping section is all that is necessary. Whenever necessary 
 to cut a cable, as at the end of a run or otherwise, exposed wires should be 
 driven within the sheath by a pin or bolt and the sheath closed over same and 
 sealed with solder. This is to be considen><l an iibsolutc rule — to seal all cable 
 ends in this manner innnediately after cutting. 
 
 The splicing of and making potlieads for all types of cable are fully described 
 in chapter 4. 
 
 CONNECTIONS TO AEKIAI- CABLK. 
 
 Wlien it is necessary to connect aerial wires to cabl(> it should be through 
 fuses and arresters installed in a can top or cable pole box. A typical method 
 of installing this can terminal is shown in figure 5-29. where drop wires are 
 coimected to the cable ; the tap taken out of the main cable will never be less 
 than ten pair. 
 
 
 1 
 
 - — Hup K 1 
 
 -^^"^^^^B^i K 
 
 ="^=M||i m 
 
 ~S/> m 6 ^j 
 
 Fig. 5-30.— TERMINAL, CAN, FUSED. 
 
 Part 
 
 No. 
 
 Name. 
 
 Reference 
 No. 
 
 Base, metal 
 
 Mounting, porcelain 
 
 Spring holaer, complete — 
 
 Bolts, clamping 
 
 Fuse, tubular, .Vampere — 
 
 Cover , 
 
 Chain for cover 
 
 Fuse springs 
 
 Carbons, pr. and dielectric. 
 
 1 
 
 2 
 
 3 
 
 4,4 
 
 (201)
 
 28 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 The conductors of cables are sometimes multiplod. That is to say, the same 
 cable pair appears in one or more terminals. The nuiltiple may be made in the 
 splices or by bridging pairs at the binding posts of terminal boxes. 
 
 The paper insulation cable should be terminated by a pot head unless it ends 
 in a terminal equipped with a sealing chamber, in which case the standard pot 
 head is not necessary. 
 
 3} 
 
 i 
 
 
 
 
 
 3! 
 
 
 
 
 1 
 
 
 fB 
 
 mi 
 2 ^ 
 
 
 J .-4 
 
 
 1 
 
 Fig. 5-31.— TERMINAL, CAN, UNFUSED. 
 
 Part 
 
 No. 
 
 Name. 
 
 Reference 
 
 No. 
 
 Base, metal 
 
 Mounting, porcelain 
 
 Bolts, clamping 
 
 Cover 
 
 Chain for cover 
 
 Binding post, hollow, complete 
 Binding post, nuts for 
 
 Terminals of lliis character iire the standard tyi)e furnislu'd l)y the Signal 
 Corps and are supi)lied in various sizes up to and including 52 pair for the fused 
 terminal and 2(5 pair for the unfused terminal. 
 
 Figure 5-30 shows fused style of these terminals and figure .5-31 shows the 
 unfused. It will he noted that the distinguishing difference is that one .style 
 is equipped with fuses and carboii-dielecti'ic protc'ctors and the other is not. 
 
 Fig. 5-32.— TERMINAL, CAN, UNFUSED, INSTALLATION OF. 
 {202 >
 
 Aerial Line Construction. — Chapter 5. 
 
 29 
 
 The former or similar mu's are invariably used where aerial open lines con- 
 nect to a cable and the latter are used where lines connected to cables are not 
 exposed to lightning or atmospheric influences, such as in systems employing 
 comi>lete underground distribution, or where connections are made to under- 
 ground cable which is connected to aerial cable through fuses and carljon- 
 dielectric protectors. Figure r)-32 shows method of installing unfu.sed terminals. 
 
 Fig. 5-33.— TERMINAL, CAN, UNFUSED, INSTALLED. 
 
 A brief description of aerial-line construction employed in connection with 
 the installation of a post-telephone system at the Front Royal Remount Depot 
 near Front Royal, Va., may be of interest, a.s conditions to be met were out of 
 the ordinary. The post proper, consisting of the customary administration 
 building, oflicers' quarters, veterinarian quarters, noncommissioned officers' 
 quarters, barracks, dispensary, and otlier structiu'es, is equipped with an 
 underground-cable system, the post-telephone switchboard being located in the 
 administration building. Communication to the colt-temlers' quarters is ob- 
 tained by means of aerial lines connecting with the unilerground-cable system at 
 the boundary of the post proper. The colt-tenders' quarters are distribute*! 
 throughout the mountains in various directions from the post proper and some 
 are so located that to construct a pole line to the quarters would be au ex- 
 tremely costly undertaking, when consideration is given to the fact that one sul>- 
 station only would be furnished service by such construction. Where practi- 
 
 46581°— 17- 
 
 -14 
 
 (-'Oo»
 
 30 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 Fig. 5-34.— AERIAL LINE CONSTRUCTION, FENCE POST LINES. 
 
 Fig. 5-35.— AERIAL LINE CONSTRUCTION. FENCE POST LINES, GATE CROSSING,
 
 Aerial Line Construction. — Chapter 5, 
 
 31 
 
 cable the lines were supported by posts of fence lines inclosinjj tlie numerous 
 pastures. An ordinary oak bracket was fastened in the usual manner to each 
 side of alternate fence posts and No. 12 B. W. G. iron wire was " tied in " to 
 porcelain insulators on the brackets. In order to obtain greater tensile strength 
 B. B. instead of standard E. B. B. grade of wire was used. Where gates were en- 
 countered a Signal Corps telegraph pole with cross-arm was erected beside the 
 gate posts at each side of the gate and the line carried over and above by tliis 
 means. Figures 5-34 and 5-35 illustrate this construction. 
 
 TRIPOD LINES. 
 
 In Alaska, where a great many poles have been set in perpetually frozen 
 ground, great trouble luis been experienced with the poles lifting or "freezing 
 
 Fig. 5-36.— AERIAL LINE CONSTRUCTION, TRIPOD LINES. 
 
 out." A inunber of methods lor jireventing such action have been tried, but 
 the comensus of opinion is lliat any plan which contemplates breaking the 
 surface of the moss or earth is doomed to failure. 
 
 Many miles of lines have been constructed in Alaska by the Signal Corps, 
 wliere poles were set in the ground and in addition were supported by braces 
 in tlie form of a tripod. While this construction proved more etTective than 
 former methods, it was not satisfactory, for, while tlie braces tended to hold 
 the pole in a vertical position, the " freezing out " was not eliminated in the 
 least, and in some instances assisted in lifting the pole, due to the ground end 
 of the braces moving in toward the pole as it lifted and preventing pole from 
 settling back, if so inclined, during the " break up " or thawing sea.son. This 
 operation, repeated for a few seasons, results in an esti-emely wobbly and 
 
 (205)
 
 32 
 
 Signal Corps Manual No. 3. — Chapter b. 
 
 irregular line and necessitates a great amount of traveling and work in a 
 barren country incident to placing the line again in repair. 
 
 After experimenting with various meth(«ls, the Signal Corps has adopted 
 self-supporting tripods as a means of supporting aerial lines where the con- 
 ditions are as above stated. IMany miles of lines utilizing these tripods have 
 been constructed, and resiilts obtained relative to tirst cost and maintenance 
 have been highly satisfactory. 
 
 Figures 5-36 and 5-37 are reproductions of photograplis of this approved 
 tripod construction in Ahiska. 
 
 Fig. 5-37.— AERIAL LINE CONSTRUCTION, TRIPOD LINES OVER ICE. 
 
 It ciUi |-e:nlily be seen Ihat Hn'se Irijiods .soiv(> Ihe ]ii'ol)l(>in of overcoming 
 the disiislidus i-csiills of jmiIcs " Irce/.iiig out." but in addilioii to this these 
 (ripods j)resent anoliier giTat adxniilage wliicii jicrbaps can l)e ai)pi'('ci;i1(>d only 
 l)y tjiose wlio liave had ex|>eri('iice in connection wilh constructing aciial lines 
 in Alaska. 
 
 (•rdinarily I lie digging of Hie cnsloiiiarx- Imlcs in I he earlli I'oi- jiojes is a 
 simple umleiMakMig. Imi in some pliiccs in Alasl<a Hie elimination of this i)art 
 of the work" by the sol r-sujiporl ing IrijMid is. in itself, a feature wbicli grejitly 
 reduces llic first <-(isl of line consti'iict ion and makes il possible |o nnderlal<e 
 llie work during wcallier cundilions lli;il <il herwise would be considei-ed ])ro- 
 Inbilive. Cnder- Hie Hi inches or iiioi-e ef lie:i\y spagninii mosses found in nian\' 
 localities in AUiska the eartli thaws liiil \cry little excn in ojien country. To 
 
 (20(i)
 
 Aerial Line Construction. — Chapter 5. 33 
 
 (lis holes, even late in the summer, is almost etiuivalent to digKinfr in set 
 (•('ineiit. DifTfiinjr Itars are soon l)lunte(l and must he scnl to the tool dresser 
 daily. Attemi»ts to thaw the ^I'ound hy means of tlie ordinary i)rosiK'ctor's 
 holier have proved unsatisfactory. 
 
 All material used in tlie coastruction of a trijiod line is comparatively lit,'ht 
 in weifiht, and the work involved in construction and maintenance is less than 
 for ordinary pole line. Movinji a section to avoid washouts, new roads, or for 
 any cau.se is more easily acconii)lishe(l. 
 
 Tripdd poles can often he jirocurcd where the re;^ular-line ]»oles of the 
 
 dimensions usually required can not he found, (i 1 I'Iihh! material is ofitMi 
 
 ohtained from dense S])ruce thickets. The i)oles for ordinary Alaskan line 
 supporting one or two wires should he 18 feet long, with not less than 3-inch 
 tops, and fairly straight. They should be cut at stump end with an axe, not 
 sawed, as the long, sharp kerf made by chopping in the usual manner is needed 
 for giving the butts of poles a hold in the earth or moss. If cut in the .sununer 
 the poles should be peel(>d innnediately, as the bark sets in a very few hours, 
 making the removal much more of a task. It is impracticable to peel poles 
 cut in the winter, as there is comparatively little moisture in the wood at that 
 season. 
 
 ^Yhere a large number of tripod pole.s are to be cut, it has been found advan- 
 tageous to prepare racks upon which the poles are placed and peeled as soon 
 as cut. Considerable weight is lost by the poles " drying out," consequently 
 I hoy should not be transported f<»r several days, unless the need for them be 
 lU'gent. 
 
 K1!E( TT\(i TiaPODS. 
 
 After the right of way has been cleared and iripod poles (.3 for each tripod) 
 have been delivered to the proper location, a force of six men properly 
 organized proceed to construct the line. The three poles are substantially 
 lashed together with 144-mil diameter galvanlze<l-iron wire, approximately 2^ 
 feet from their small ends, and the tripods raised and aligned in pi'oper position. 
 Oak bi-ackets and insulators are then placed, as shown in figures, and the line 
 wire " tied in " to the insulator in the customary manner. While sucH con- 
 struction is best adapted for supporting one or two wires, five or six may be 
 supjuirted with less danger of crosses than there would bo with the ordinary 
 bracket line. 
 
 As with all line construction. Judgment must be exercised in meeting vary- 
 ing conditions when constructing trii)od lines, and on curves and corners it 
 may be necessary to guy one or more of the tripods or to equip their bases 
 with three bracing members, as shown in figure .VST. This figure ilhistrates 
 the latter method, which was employed in crossing a shallow, frozen lake. 
 
 LOXr, SPANS. 
 
 As previously stated in this chapter, where unusually long aerial spans (over 
 1,.500 feet) are necessary a special composition or steel wire should be used. 
 Moderately long .spans can be made with galvanized-iron wire. In either case 
 special construction is necessary for resisting the strain, and .iu«lgment nuist be 
 u.sed in determining the manner of insulating the line and anchoring at the two 
 terminals of such a span. 
 
 The following illustrations show methods which have been adopted for tele- 
 gi'aph lines of the Washington-Alaska military cable and telegraph system in 
 Alaska whei-e it is necessary to cross swift-current rivers and mountain gorges. 
 
 (207)
 
 34 
 
 Signal Corps Manual No. 3. — Chapter 5. 
 
 
 W A'-^ 1 ■^ "■ i\ 
 
 ,i>i^4ff:' ^^m\^ 
 
 Fig. 5-38.— AERIAL LINE CONSTRUCTION, LONG SPANS, METHODS OF TERMINATING. 
 
 (208)
 
 Aerial Line Construction. — Chapter 5. 
 
 35 
 
 It will be noted that no special material except wire, in some instances, is 
 required. 
 
 Figure 5-38 shows two methods of providing support for excessive strain of 
 long spans. In some instances l)otli are u.sed, one at each end of the span. The 
 line wire is made fast at G, laid in the saddle at D, pulled up at saddle at C, 
 and made fast at .strain in.sulator attached to H. As much sag as practicable 
 should be allowed, as the strain rapidly increases as tlie wire is pulled taut. 
 The strain of long span is not borne by the land lines, and consequently proper 
 steps should be taken for guying the terminal poles of the,se lines. 
 
 Fig. 5-39.— AERIAL LINE CONSTRUCTION, LONG SPANS, CONSTRUCTION OF SADDLES. 
 
 The poles and stubs for this construction should be as short as practicable, 
 but care should be taken to keep the line wires and guy fastenings as far as 
 practicable above snow line, as deep snows will ofttimes .break guy w'ires. 
 
 '*»•• '*«'*'<^'.K.J^ 
 
 Fig. 5-40.— AERIAL LINE CONSTRUCTION, LONG SPANS, ADDITIONAL METHOD OF 
 
 TERMINATING. 
 
 (209)
 
 36 Signal Corps Manual No. 3. — Chapter 5. 
 
 At crossings on the Yukon River the l)oat thanuel is on the bluff side of the 
 river and the water on the opposite shore is usually so shallow that boats can 
 not navijrati', consequently short poles and stubs can be conveniently used. At 
 Ruby, Alaska, the bluff is of such height that the pole supporting the saddle is 
 eliminated and the line wire across span is terminated at strain insulators 
 fastened direct to stub shown at H and G in figure 5-38. While mechanically 
 the strain insulator is best adapted for terminating such lines, from an elec- 
 trical viewpoint the glass insulator with one or two petticoats properly placed 
 is better than the ordinary sti-ain insulator, as in stormy weather a film of 
 moisture can easily bridge across the strain insulator and thereby cause a heavy 
 leak. AVhere the latter insulator is used it should be housed by means of a 
 metal funnel, the small part of the funnel fitting snugly to span wire in order to 
 avoid the above-mentioned defect. 
 
 Figure 5-39 shows methods of constructing saddles for supporting long span 
 wire. The method shown on left of this illustration is the one employed in 
 figure 5-38. 
 
 Figure 5--i0 shows an additional method of terminating a long span wire, the 
 wire having passed over a saddle which is not shown in the figure. 
 
 (210)
 
 Chapter 6. 
 
 POST TELEPHONE SYSTEMS. 
 
 General Orders, No. .5, dated January 28, 1913, relates to post teleplione 
 systems. Extracts of this oriler are as follows: 
 
 1. For administrative purposes the following telephonic comnmuications are 
 authorized at military posts and will be established by the Signal Corps as 
 rapidly as funds l)ei(>me available. Telephones not specitied in this order will 
 be installed only upon the approval of the Chief Signal Officer of the Army, 
 and the specitic need for each must be stated when application is made for its 
 installation : 
 
 Office of the commanding olHcer 1 
 
 OfHce of the adjutant 1 
 
 Office of the quartermaster 2 
 
 Office of the quartermaster, additional (when approved in each individual 
 
 case; to be on same line with other telephone) 1 
 
 Office of the Artillery engineer or signal officer 1 
 
 Office of the ordnance officer 1 
 
 Office of the sergeant major (when approved in each individual ca.se) 1 
 
 Each officer's quarters 1 
 
 Officers' mess 1 
 
 The hospital 1 
 
 Each guardhouse 1 
 
 The post exchange 1 
 
 The pumping station 1 
 
 Power plant : 1 
 
 The corral 1 
 
 The quartermaster dock 1 
 
 Barracks for each organization, band included 1 
 
 Quarters of the senior master electrician, electrician sergeant at Coast 
 
 Artillery posts, or electricians at interior posts 1 
 
 Telegraph office (if located on reservation) 1 
 
 Radio station 1 
 
 Target range (when approved in each individual case) 1 
 
 The telephone switchboard will usually be located in the administration 
 building. Only telephones supiilied by the Signa^ Corps will be connected in 
 any manner to these sy.stems. 
 
 In a number of instances temporary post-telephone systems have been in- 
 stalled at military posts. Almost invariably such systems are of local battery 
 type. In some of these systems underground construction has been employwl. 
 in others aerial construction, and in others a combination of both. 
 
 When a standard system is authorized for a post equipped with a temporary 
 system, provision should be made for utilizing, as far as practicable, the 
 material u.sed in the temporary system. 
 
 For information relative to cable system chapter 4 of this marmal should be 
 consulted. For information relative to aerial-line construction chapter 5 
 should be consulted, and in chapter 8 will be found complete ,.inni'.'- "i,,.. of all 
 material and tools that will be required. 
 
 The Signal Corps standard type of post-telephone .system is coiuin.ni r.aitery, 
 utilizing underground construction as far as practicable. For telephones at a 
 
 (211) 1
 
 2 Signal Corps Manual No. 3. — Chapter 6. 
 
 great distance from post, such as corral, pumping station, and small-arms 
 target range, in some instances, it is impracticable to furnish service under- 
 gi'ound and aerial construction must be resorted to. 
 
 As stated In preceding chapter, where aerial lines are connected to a cable 
 system the cable must invariably be protected by suitable lightning arrester. 
 In addition, each telephone connected to an aerial line must invariably be pro- 
 tected by a suitable lightning arrester. 
 
 The lightning arrester protecting a telephone shouUl be located indoors and 
 as near as practicable to entrance of line. 
 
 Figure 6-1 shows the Mason lightning arrester, which to date is most com- 
 monly used by the Signal Corps, and figure 6-2 shows an arrester which is now 
 being developed for installation in locations that are damp or periodically so. 
 
 Fig. 6-1.— LIGHTNING ARRESTER, TELEPHONE. 
 
 Part 
 No. 
 
 Name. 
 
 Base, porcelain 
 
 Choke coil, left (facing choke coil end of arrester). . 
 Choke coil, right (facing choke coil end of arrester) 
 
 Clip, fuse 
 
 Clip, carljon 
 
 Carbon rod for choke coil 
 
 Mica insulators for choke coil ; 
 
 Screw, binding, with nuts , 
 
 Reference 
 letters. 
 
 Some difficulty has been experienced with the type of arrester shown in 
 figure 6-1 wliere they liave been installed in ilanip places, as laundries, due to 
 the fact that vapor cau.ses deterioration of coils and temporary low insulation. 
 It is believed that the arrester sliown in figure 6-2 Is also adapted for installa- 
 tion in the Tropics, wliere at certain seasons the atmosphere is very humid. 
 
 Tlie principle in general upon which these arresters operate is that both 
 sides of tlie incoming circuit are made to pass very closely to carbon blocks 
 wliich are connected electrically and directly with the earth. In addition, at 
 tins point a choke coil is in series with each line .so that a static charge due to 
 liglitnlng coming in on line wires encounters at the same point an easy path to 
 eartli aiMl an impediment in the path to instrument the arrester is protecting. 
 A bolt of liglitning may be of such magnitude and force that it will divide, 
 following botli paths, ixtssibly burning up arrester and instrument, but static 
 cliarges of suflicient magnitude to injure instnnuent, which are occasioned by 
 inductive effect of liglitning and which fic((U(Mit!y occur, are efficiently arrested 
 by these types of lightning arrester. 
 
 (212)
 
 Post Telephone Systems. — Chapter 6. 
 
 Fig. 6-2.— LIGHTNING ARRESTER. TELEPHONE, MOISTURE-PROOF TYPE. 
 
 Part 
 No. 
 
 Name. 
 
 Porcelain block 
 
 Cover, brass 
 
 Cover, hexagon nut for 
 
 Cover, gasket for 
 
 Cover, screw for 
 
 Binding post, long, with nuts and washer. . 
 Binding po.st, short, with nnts and washer. 
 
 Choke coiL . : 
 
 Carbon blocks 
 
 Dielectrics 
 
 Carbon clip 
 
 Fu.se clip 
 
 Angle clip 
 
 Spring clip 
 
 Fuse wire, special, feet. •- 
 
 Reference 
 No. 
 
 Lightniiii; arresters for teleplione.'^ ordinarily liave three i)roteetive features, 
 viz, fuse, air gap to ground, and impedance coil. Tlie fuse is for opening the 
 circuit whenever excessive curi'ent i'nnn any cau.se, sucli as a cross of power 
 wires, comes in on the telephone line. The fuses supplied should operate for 
 current in excess of one ampere. The air gap is u.sually a small space between 
 metal or carbon blocks ; these are often separated by celluloid or mica, one of 
 these blocks being in contact with the telephone circuit and the other connectetl 
 directly to ground. Currents of excessive volta.sie will break down the air gap 
 going directly to ground. The impedance or choke coil acts as a Iiigh resistance 
 to high frequency alternating currents which come in on telephone lines, either 
 directly or through induction, and together with the air gap usually lead such 
 currents to ground. Fuses operate too slowly to interrupt lightning or liigh 
 voltage discharges of any kind. 
 
 It is important to note that where there is danger of lines becoming crossetl 
 with external circuits, the incoming line should invariably be connecteil to fuse 
 end of arrester, otherwise an arc to ground would not be stopped by the fuses. 
 Where there is absolutely no danger of lines becoming cros.sed with external 
 circuits and where considerable trouble is occasioned by the continmd opening 
 of fuses due to slight static dischar.ws, the incoming lines may be connected to 
 
 (213)
 
 4 Signal Corps Manual No. 3. — Chapter 6. 
 
 opposite end of the arrester upon receipt of special permission for such action 
 from tlie Chief Signal Officer of the Army. 
 
 The first step in " laying out " a telephone system for a post is to procure a lar;;e, 
 accurately scaled map showing all buildings, present and projective, walks, 
 roadway, contours, and all other objects affecting the location of telephone lines. 
 On this indicate the location of the switchboard and all the telephones to be con- 
 nected to it. The routes of the various leads of poles and course should now be 
 Indicated. These should be determined only after personal inspection of the 
 ground and conference with the post authorities. It is important that the 
 routes as laid down in the first instance should not be changed later, as by so 
 doing the material ordered may be rendered unsuitable, with resulting expense 
 and delay in procuring new supiilies. Avoid changing i)ole line from one side 
 of the street to the other. Avoid trees or other obstacles that would interfere 
 with the line, sharp curves, and electric-power wires. If aerial construction is 
 used, it should be as inconspicuous as possible; other things being equal, run 
 in rear of buildings in preference to front. It may be stated in general that 
 ca1)le should be used where five or more i)airs are to be carried in one lead. 
 In laying out cable distribution, the future needs of the service should be 
 provided for as far as possible, and spai'e pairs made availaldc. 
 
 A terminal frame is provided at location of post-telephone switchboard, and 
 all lines to switcliboard ternnnate at this fi-anu>, whert> each is cross connected 
 to a suitable protector. 
 
 An exception to this is made in installations where a ternnnal box is in- 
 stalled in proximity to switchboard, in which case the incoming lines are tei'- 
 minated at terminal strips in this box. In such instances, by means of suitable 
 cabling, th(> inconung lines are led directly to protectors, and I'l-oni protectors 
 they are cross connected to cable terminals of IVain(> where Die switchboard 
 cables are ternunated. 
 
 All lines between protector frame and switchboard are contained in switch- 
 board cable, which is fully described later in this chapter. 
 
 The type of protector frame varies with size of installation. Where a 50 
 or 100 line switchboai'd is installed the protector frame is usually located in a 
 cabinet placed beside the switchboard. Tins cabinet has the appearance (^f 
 being a continuation of the switchboard cabinet. In larger installations a 
 frame termed "distributing fram(> " is installed. This frame is not incas(>d. but 
 consists of angle-iron ui)rigli1s bolted to angle-iron horizontal members and 
 braces, and may be placed at a distance from wall without being braced to it. 
 AVith eitlKM* frame, metal punchings to which ar(> soldered the inconnng lines, 
 also a means of cross connecting I'roni these punchings to the jirotectors, is 
 ]irovided. ^^■illl the distributing frame lai'ge ii'on iMngs coated with rubber com- 
 pound are fastened to the frame at convenient points. These rings are for 
 supporting the cross-connecting wires. Figure G-.^ illustrates the construction 
 and maimer of cross connecting llie distributing frame. 
 
 Various types of protectors are i)rovided, but tlie object of ail is to ground 
 the incoming line in the event of a disrui)tive cui'rent becoming imi)ose(l u])on 
 the line, thereby ol)viating damage to switchboard. All protectors are provided 
 with carbons and dielectrics. These carbons and dielectrics consist of two car- 
 bon lilocUs anil one dieleclric I'oi- each side of eacii circuit. The incoming line 
 is in eleclrical conlract willi one of the cai'bon blocks and Ihe oilier carbon 
 block is ill (jiri'cl coiila<'t with a nietiil plate which is elect rica!l.\' connected to 
 earth. The dielectric, which consists of nii(;i or celluloid api»roxiniately 1 mil in 
 thickness, the other dimensions being same ms width and length of carbon block,
 
 Post Telephone Systems.— Chapter 6. 
 
 Fia 6-3.— FRAME, DISTRIBUTING, TELEPHONE SWITCHBOARD. 
 
 (215)
 
 6 Signal Corps Manual No. 3. — Chapter 6. 
 
 is placed between the blocks, thereby insulating one from the other. The 
 dielectric is either perforated or has a small U-shaped piece removed so that 
 a dangerous current will have merely a small air gap to break down in order 
 that it will be dissipated in the earth. Static or oscillating currents of high E. 
 M. F. and high potential circuits will be grounded by the part of the protector 
 just described, but a current of comparatively low E. M. F. that would in time 
 burn out windings of switchboard would not be grounded by this means ; con- 
 sequently each protector is also provided with what is termed a " heat coil," with 
 suitable mounting, for arresting the latter currents. These currents are com- 
 monly termed " sneak currents." 
 
 In one type of these heat coils the passage of a " sneak current " causes 
 the line to be opened and the line side groundetl. In another type the line is 
 merely grounded. In either case the operation of the coil is caused by the 
 current heating to a point of " cold flow " solder which normally holds a 
 spring, which is in contact with line, clear of ground plate. The heating is 
 accomplished by means of a winding in some instances and in others by a spe- 
 cially prepared composition. The winding or composition is in series with the 
 incoming line and is so designed that heat is generated when a dangerous cur- 
 rent passes through the heat coil. The time element of operation of these 
 coils is inverse to the strength of current. 
 
 Currents induced by lightning act too rapidly for fuses or heat coils, and 
 although such currents frequently accomplish unaccountable i-esults the car- 
 bon-dielectric part of switchboard protectors almost invariably ground these 
 currents. 
 
 The crossing of telephone lines with lighting circuits might complete a cir- 
 cuit through switchboard w'hich would burn out all coils in its path and yet 
 be of such E. M. F. that the carbon-dielectric part of arrester would not act. 
 The heat coil portion of arrester would ground and dissipate such a current 
 before damage to switchboard could result. 
 
 COMMON HATTKIIY I'OST-TKT.Kl'HOX K S W ITCI I HOAKDS. 
 
 Vnrioiis types oC ('. 15. tclc|)li(iiH> switclibonnls liavc been installed at Army 
 posls. 
 
 The following dislinguisliing f(>alun>s. which arc ]»f(iminciil in idciit il'ying 
 (he various types, nvv believed to l)e wctrlhy of mention : 
 
 1. \'isu;il siguMls for line signal and visual signals for siii)ervisory signal. 
 
 2. Visual signals for line signal and lamp signals for supervisory signal. 
 8. Lamp signals for line signal and lamp signals for supervisory signal. 
 
 In most instances the keys are double ringing, although some of the switch- 
 boards installed in connection with early installations were equipped with 
 the single ringing type. With the double ringing key the switchboard ojierator 
 is enabled to ring on eiljier of the two lines which have be(>n connected by 
 means of the switchboard connecting coi-d. ■\Villi the siiigl(> ringing key. it is 
 po.ssible to ring on one line only, unless tlu' connt>cting cords are transposed. 
 
 Some of the conmion battei-y switchboards purchased by the Signal Corps 
 are designed to operate on a 30- volt circuit while others ar(> designed to 
 operate on a 24-volt circuit. Care should be exercised nol 1o operate the 
 24-volt sigriid lamps on .SO-volt circuit, as tlicir life is greatly decreased by the 
 excessive voltage. 
 
 A description of switchboard e()uipped with "visual signals for line signals 
 and visual signals for supervisory signals" follows. The circuit of the system 
 where a switchboard of this type is used is shown diagrammatically in figure 
 6-4, 'The instruments \ised in connection with this switchboard conform in
 
 Post Telephone Systems. — Chapter 6. 
 
 wiring nnd design to well-known coininerciiil standiirds, and the operation of 
 the switchboard is fully explained hereinafter. 
 
 To signal the switchboard (tig. G-5) it is merely necessary to remove the 
 receiver from the hook, which permits direct current to flow from the common 
 battery through the line signal, one contact of the cut-off jack, the line, the 
 hook, the windings of the induction coil, the transmitter, line, the jack, and 
 back to battery. This causes the line signal to close, attracting the attention 
 of the operator. 
 
 %im. 
 
 
 24 or 30 Vo/ts 
 Storage, Bati^ry 
 
 Fig. 6-^.— C. B. TELEPHONE SYSTEM, SIMPLIFIED DIAGRAM OF CIRCUITS. 
 
 Referring to figure 6-4, when the switchboard connection is made, disre- 
 garding detail of switchboard circuits, current flows from the common battery 
 through the supervisory signal, the lines in parallel to each transmitter, 
 induction coil, hook, line, and back through supervisory signal to battery. 
 The supervisory serves the dotible purpose of providing the necessary retarda- 
 tion, as previously described, under the composite circuit and of indicating t<i 
 the operator that the conversation has been completed. 
 
 Line Signa/ 
 
 ii|i|i|a|i{i|i|iii|i|i|i|i|i|i-' 
 
 30 Vo/ts 
 
 Fig. 6-5.— C. B. TELEPHONE SYSTEM. VISUAL LINE SIGNAL OPERATION. 
 
 ^217)
 
 signal Corps Manual No. 3. — Chapter 6. 
 
 The instrument circuit of one of tlie types of common battery telephones 
 used is out of the ordinary and is sliown in figure 6-5. It employs the principle 
 of the balanced \Yheatstone's bridge to keep the direct current flow from the 
 receiver, while the voice currents, which are alternating in effect, are forced 
 by a combination of retardation and low resistance, located in the arms of 
 the bridge, through the receiver. A and D are retardation coil windings and 
 B and C noninductive resistance windings. The bridge is balanced for the direct 
 current flow, indicated by the single-pointed arrows, by making the ohmic re- 
 sistance of the four arms such that the Wheatstones' bridge equation, A:B = 
 C:D, is balanced. There will, then, be no direct cun-ent flow between the 
 points 2 and 3, as their potential is the same, and the receiver, which takes the 
 place of the galvanometer in the i-egular testing bridge, will be entirely free 
 from direct-current action. The bridge, however, is completely out of balance 
 for voice currents, which can not penetrate the high retardations .1 and D, 
 
 
 rRONT VIEW VERTICAL SECTION 
 
 Fig. 6-6.— SWITCHBOARD, TELEPHONE, C. B., 50-LINE, VISUAL.
 
 Post Telephone Systems. — Chapter 6. 
 
 Part 
 No. 
 
 Name. 
 
 Reference 
 So. 
 
 Binding post, lock-nut 
 
 BitulinR post , wing-nut 
 
 MeM, night 
 
 Boll, night, binding-post nuts 
 
 BpII, night, relay 
 
 Cable, switcli board, feet 
 
 Cord, -l-way, for tninsmiller and receiver 
 
 Cord, switcliboard, complete, with terminals 
 
 Cord weight ;■. . 
 
 Cord bushing 
 
 ( 'ord plug screw 
 
 Cord plug sliell screw 
 
 Cord plug seat with screws 
 
 Cord fastener, complete, with screw s .• 
 
 Coil, induction 
 
 Coil, induction, terminals 
 
 Coil, impedance, for operator's circuit 
 
 Condenser, 2 m f 
 
 (ienerator, five-bar 
 
 Generator crank 
 
 (ienerator crank liandle 
 
 Jack, line 
 
 Jack, generator call 
 
 Key, ringing, complete 
 
 Key, ringing^ ban lie 
 
 Key, answermg, complete 
 
 Kev, answering, handle for 
 
 Line terminal 
 
 Re:>eiver, single head 
 
 Signal generator call, complete 
 
 Signal generator call, drop 
 
 Signal generator call, adjusting screw and nut 
 
 Signal generator call, moimting screw 
 
 Signal generator call, armature mounting screws. . 
 
 Signal generator call, armature pivots 
 
 Signal, line, complete 
 
 Signal, line, drop 
 
 Signal, line, a<ljiist ing screw with nut 
 
 Signal, lino, mounting screw 
 
 Signal, line, armature mounting screws 
 
 Signal, line, armature pivots 
 
 Signal, supervisory, complete 
 
 Signal, suiiervisory, drop , 
 
 Signal, supervisory, adjusting screw with nut 
 
 Signal, sujiervisory, mounting screw 
 
 Signal, supervisory, armature mounting screws. . . 
 
 Signal, supervisory, armature pivots 
 
 Switcli, transmit ter , 
 
 Switch, transmitter, han ile , 
 
 Switch, transmitter, crank with screw 
 
 Switch, transmitter, stop pins 
 
 Switch, battery test (same as transmitter switch). 
 
 Switch, night bell (same as transmitter switch) 
 
 Transmit ter 
 
 and are thus forceil tliroii.^h tlie receiver and intiiindiiorive resistances Ji and (' 
 in tlie path indicated by tlie doiible-lieaded arrows. In practice all of the coils 
 of this briilfio are wound on one spool and internally connected, so that as far 
 as external appearances or connections are concerned it resembles a standard 
 induction coil. The resistance of the four windinjrs are approximately 20 ohms 
 each for .1 and B and 30 ohms each for C and /). The total resistance of the 
 noninductive windinjrs B and (\ which are in series with the receiver, is there- 
 fore only oO ohms, thus offering: no appreciable ol»stacle t<» the voice currents. 
 In fact, the receiver is practically, in the line circuit, direct, and receives the 
 maximum available incoming transmi.><sioii with no distortion or lo.><ses. 
 
 Common battery switchboards manufactured accordinir to Sifrnal Corps sjieciti- 
 cations are furnished in three sizes acconunodatin^r a maximum of 2<M) lines. 100 
 lines, or 50 lines, respectively, the actual c(iuipment in either case deixMidin;: 
 upon the needs of the installation to which it pertains. 
 
 The three sizes are similar in arranirement of parts, in operation, and in 
 wiring. A description of the 50-liiie size therefore applies to all. This switch- 
 40581 "— 17 15 1-19)
 
 10 Signal Corps Manual No. 3. — Chapter 6. 
 
 board is shown in figure 6-6, and tlie protector cabinet mentioned in first part 
 of this chapter is sliown in figures 6-7 and 6-S. 
 
 In figure 6-S the Cook self-soldering lieat coil and protector is shown, and in 
 figure 6-9 the Western Electric heat coil and protector is shown. 
 
 The cabinet of this switchboard is built of oak and provided with an uppei- 
 and lower rear door, a front panel, a foot rail, and is designed to acconunodate 
 all of the apparatus necessary for the operation of the system, except the 
 battery. 
 
 In addition t<» the 50 common battery lines, this switchboard i>rovides a 
 mounting for 5 magneto call lines for long-distance operation, including trunk 
 connections. 
 
 Ten cord circuits are provided. The conductors of the cords are usually of 
 steel, copper, or tinsel strands. The keys provide for ringing on the calling 
 cord only. This arrangement simplifies the wiring and eciuipment. The super- 
 visory signal also acts as a retardation coil, through which the battery is fed to 
 the coil circuits. This signal, like the line signal, shows in the form of a target. 
 
 The supervisory signal operates when the cord is in use and clears wht^n 
 the parties hang iip. A movement of the user's hook up or down operates this 
 signal. 
 
 The line signal is thrown wlien the calling party removes his receiver from 
 the hook and is restored automatically when the operator inserts the answering 
 plug. 
 
 The common battery is bridged on the line through the supervisory signals. 
 
 The operator's circuit has a standard common battery induction coil, which 
 is connected to battery through a retardation coil, and has a condenser bridged 
 across the source of current supply. A condenser is also placed in the sec- 
 ondary circuit to prevent a flow of direct current when the listening key is 
 thrown. 
 
 The breast ti'ansnntter or suspended type transmitter and single-head re- 
 ceiver which form the operator's ecpiipment are connected to wing-nut binding 
 posts in cabinet of switchboard by means of suitable cords. Tlie operator's 
 transmitter is provided with a cut-out switch suitably designated. 
 
 '{"lie night-bell cii'cuit provides a relay and vibrating bell and operates, if 
 desired, whenever a call is received. 
 
 The circuits of this switchboard are shown in tigure 6-10. Reference to 
 this figure indicates that when the subscriber's hook Jl is up current flows 
 from the battery through the jack contact C to the subscriber's instnnneni, 
 tiirough the transiintt«'r and iiKhiction coil back to Jack contact A', and thence 
 tln-ough line signal to battery. 
 
 When the answering plug is inserted in the jack •/ the line signal is cut oil" 
 and falls buck. Current now Hows to the user's instrument through one 
 winding of the supervisory signal N, through c(mtii<'ls of key Ix. through cord 
 to tip of ;ins\vering T)lug, tiirough jack, retiu'iiing to the battery through lli(> 
 odiei- side of the jack, cord, and key and the olliei' winding of the super- 
 visory signal. The operator depresses listening key J\, and the user's voice 
 < urrents flow into the re^-eiver circuit at the switchboard. The calling cord 
 of the same pjiir as the miswering cord just used is now inserted in the jack 
 corresponding to the line desired, the key R is depressed, th<> generator turned, 
 and the connection is established. As .soon as the pluLT is inscrteil curi-enl flow- 
 ing through the supervisory signal shows "busy" until bolii p.-ii'ties hang up 
 (heir receivers. Should eilliiT parly desire to nllract central's attention a 
 movement of the switch hook will cause this sigiud to flutter.
 
 Post Telephone Systems. — Chapter 6. 
 
 11 
 
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 1 n 
 
 
 
 a 
 
 f=f 
 
 ' 1 ! '!l 1 
 
 
 
 ^^ 
 
 
 ' ill '^ 
 
 
 "3 Ko 
 
 t I 
 
 
 
 
 •« 
 
 
 
 
 :-: 
 
 
 
 
 H 
 
 » 
 
 1 
 
 1 
 
 1 
 
 J« 
 
 
 
 
 
 i ii 
 
 
 M 1 
 
 ■» 
 
 X 
 
 :: 
 
 
 o « 
 
 
 
 
 
 
 H 1 
 
 ;? 
 
 :1 
 
 :. 
 
 
 \ \ 
 
 i 
 
 
 
 i II 
 
 I :: 
 
 » 
 
 X 
 
 ■ 
 
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 of 
 
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 \ \ 
 
 
 
 .1 :: 
 ■*" tt 
 
 l" ii 
 
 » 
 
 i W- ' 
 
 1 
 
 
 
 
 
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 Wi 
 
 » 
 
 H 
 
 t 
 
 1 
 
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 ■<» ;; 
 
 
 
 X 
 
 
 1 M 
 
 
 
 
 -4<-H^ 
 
 > 
 
 1 
 
 i 
 
 s° 
 
 1 
 
 n 
 
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 §1^ ^_^ 
 
 ■^■^ :: 
 
 1 
 
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 it=ii 
 
 lU... -.- 
 
 t^*" 
 
 i I 
 
 
 t /2« 
 
 1 
 1 
 
 1 
 -II 
 
 •if- ' ^ i 
 
 5 ir 
 
 
 t 
 
 IL, 
 
 ^-■"l 
 
 U 1 «K 
 
 • 
 
 
 
 ^m 
 
 5..-' - ■■ -.:.-««l 
 
 b 
 
 FRONT VIEW OF CABINET 
 WITH DOOfI REMOVED I 
 
 SECTION 
 
 ARRtST^ CiffNET 
 KSXKtiOXIK 
 
 NAME PLATE 
 
 Scale ^if\*>l in. 
 
 Fig. 6-7.— SWITCHBOARD, TELEPHONE. PROTECTOR CABINET. 
 
 Part 
 No. 
 
 Name. 
 
 Heference 
 No. 
 
 Cabinet only 
 
 Gla.'^s for door 
 
 Door, front 
 
 Door, back 
 
 Panel fuse complete 
 
 Slate for fu>e panel 
 
 .Screws for mounting 
 
 Angles for mounting, large. 
 Angles for moimting, small. 
 
 Fuse, baby, 3-ampere 
 
 Fiase, telephone, j-ampere . . 
 
 (221)
 
 12 
 
 Signal Corps Manual No. 3. — Chapter 6 
 
 2 No8 LINE PROTECTOR 
 
 AND 
 
 L-3 DISTRIBUTINO FRAME 
 
 Fig. 6-8.— SWITCHBOARD, TELEPHONE, COOK PROTECTOR, DETAILS. 
 
 Part 
 Xo. 
 
 Name. 
 
 Arrester, complete, without heat coil. 
 
 Arrester mountirifr 
 
 Bolt and nut 
 
 Carbons, pairs 
 
 Coil, heat 
 
 Mica 
 
 Spacer 
 
 Spring, arrester, rinht-hand 
 
 Spring, arrest pr, left-hand 
 
 Spring', line, ri^hl -hand 
 
 Spring', line, left-liand 
 
 Terminal, cross-connect iuK, small •. 
 
 Terminal, cross-connectin;;, large 
 
 Terminals, cross-connecting, set of 20, with mounting. 
 
 Relerence 
 
 No. 
 
 Fig. 6-9.— SWITCHBOARD, TELEPHONE, WESTERN ELECTRIC PROTECTOR, DETAILS
 
 Post Telephone Systems.— Chapter 6. 
 
 i:; 
 
 The night-bell circuit of this central enertry switclihonnl is shown in figure 
 0-11. It will ho soon tlwit wlicii tlic visual siLriial niicratt's a curnMit will How 
 
 ZZ^3 r-^r — 
 
 Calling 9r Frvt Cm/ 
 
 ==^1^ 
 
 zT^yy. 
 
 t:-\\ 
 
 
 f 
 
 I — VWWWW- 
 ( — ^AAV/W— 
 
 ~»«W«r- 
 
 oo«^ 
 
 I Hl|l|l|lll|l|l|l|l[lllll|l|l|^^ 
 
 Lisli^ 
 
 ^ TrarumitLtr switz 
 
 ■o<^ 
 
 fusta iit 
 
 Fig. 6-10.— SWITCHBOARD, TELEPHONE, VISUAL, CIRCUITS. 
 
 from the common battery thi-ough the contact of the night-boll key A', thence 
 thnmgh the rolav. thence through the contact of the arniat\n-o <if the signal, 
 
 
 
 
 
 
 
 i 
 
 W^ttttttnth 
 
 
 
 J/' itHnflt)^' 
 
 
 
 G 
 
 
 
 O <j 
 
 )) — 
 
 
 
 
 1^^^ 
 
 f'l 
 
 
 
 
 
 
 
 
 J 
 
 
 
 
 
 
 
 ^ — ^11 — ' 
 
 
 Hi- 
 
 c 
 
 
 Fig. 6-11.— SWITCHBOARD, TELEPHONE. VISUAL. NIGHT-BELL CIRCUIT. 
 
 returning to the battery. The operation of the relay, however. iK'rmits current 
 to flow from the tlry cells I) through the right -han.l contact of tiie key K, theuc-e 
 
 ('2-2-Ai
 
 14 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 tliroush the bell and back to the battery D. When the niasneto drop operates, 
 current will flow from the battery D through the right-hand contact of the key 
 K, through the armature contact of the magneto drop M, through the bell B, 
 returning to the battery 7). 
 
 Pi/ot lamp , redcap 
 )30v. 
 
 Night bell, 
 for all positions 
 
 lO 0| 
 
 One relay ^ for each 
 operators position 
 
 |f^0^|_ 
 
 c5 
 
 Night bell 
 3 mtch 
 
 Rus bars on fuse panel 
 
 4 
 
 Pilot lamp, redcap 
 
 \\^ lOohms^W 
 
 rS 
 
 n 
 
 +1 — ? i 
 
 Bus bars on fuse panel 
 NIGHT-BELL CIRCUIT. 
 
 fit 
 Dry battery 
 
 Fig. 6-12.— SWITCHBOARD, TELEPHONE, 200-LINE, 
 
 It will be noted that with the visual signal a relay is utilized to close the 
 night-bell circuit. The reason for this is that the contacts of the visual signal 
 are of a delicate nature and it is advisable to reduce to a mininunn the current 
 strength broken at these contacts. 
 
 Cenerator Call Drop 
 
 Fig. 6 13.— SWITCHBOARD, TELEPHONE, 200-LINE, GENERATOR DROP CIRCUIT. 
 
 (224)
 
 Post Telephone Systems. — Chapter 6. 
 
 15 
 
 With tlio 200-lin(' size only, tlu' iii;,'lit-lK'll circuit is ;is shown in fiffiirp 0-12. 
 Witli tiiis size, a small .SO-voIt pilot lamp is lij^hted by means of a relay whenever 
 any one (»f the line sijinals is operated. 
 
 Where tlie lenjith or resistance of lines make common hattery si^rnalin;; 
 impracticable, or where the line is contained in submarine cable u con.siderable 
 distance, one of tlie generator call drops is brought into service. 
 
 Figure 6-13 shows approved metliod of wiring in a circuit of this l^ind wliere 
 a telephone instrument is installed at the distant station. 
 
 It will be noted that the telephone connected to suc-h a circuit must be of 
 l(»cal battery or composite type, and that the line between switchboard and sub- 
 station is not connected to battery leads at either end. In other words, tlie line 
 is "dead," except when calling or talking is in progress, and then the currents 
 imposed upon the line are alternating or pulsating. This condition is highly 
 desirable where line is contained in submarine cable, especially if tlie insulation 
 of cable be rubber compound. 
 
 
 fUaarsi biack. One forcfCty ten hna J«c*e 
 
 m 
 
 
 ) eo ID eo 50 ■- 
 
 o o p o 
 
 BlQiJf. f>v for ctvjy SOjitcAs 
 
 .Tx: 
 
 ^'W'I>I'I'I'I'I'^T+ 
 
 Amntrinq cord 
 
 li\ 
 
 mm 
 
 Jack^ 
 
 One bdlfaraUpaitJons 
 
 To magnito drops 
 
 Jcpiiotlgm p 
 0^200 line, 
 boanionhf 
 
 OrunQC->rf »t£ 
 
 LINE SIGNALS 
 
 PuncJitngs 
 
 m^ll 
 
 
 Dry battery 
 
 To ope/aton urcutt - D/urrrry 666 L 
 
 i- 
 
 3: 
 
 LAMP SIGNALS 
 
 To nn^rn^ drxMit. 
 Dntrng eaeL 
 
 Fig. 6-14.— SWITCHBOARD, TELEPHONE, VISUAL LINE SIGNAL, LAMP SUPERVISORY 
 
 CORD CIRCUIT. 
 
 The condensers in series with each line ar the switcliboanl prevent the 
 common battery coming in direct contact with the line, while the alternating 
 and ptilsating currents employed in calling and talking are not prevented 
 from reaching line by the condensers. 
 
 What has just been stated of the switchboards equipped with " visual 
 signal for line signal and vistial signal for supervisory signal " is true of the 
 switchboard having " visual signal for line signal and lamp signal for super- 
 visory signal," except that instead of having visual signals in the cord cir- 
 cuits a small 30-volt electric lamp with colored caps (usually red), both of 
 which are mounted on key shelf, are supplied. 
 
 (22b)
 
 16 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 By means of :i relay for each cord, when tlie operator phiss into a jack, 
 the hnnp for tliat particnhir cord lights an«l is extinjiuished when party called 
 removes receiver from hook. When either of tlie two parlies coniu'cted by 
 means of the telephone switchboard hang receiver on hook, the relay asso- 
 ciated with the particular cord used for connection is operated. This in turn 
 lights the small lamp associated with that particular cord, and the operator 
 is thereby notified that line is not in use. 
 
 This type of switchboard is now furnished for the ."(), 100, and 1200 line 
 size. 
 
 Figure 6-14 shows the cord circuit. The other circuits of the switcbboai-d 
 are identical with those of the switchl)oard previously described. 
 
 LAMP SIGNALS FOR LINE SIGNALS AND LAMP SIGNALS FOR SUPERVISORY SIGNALS. 
 
 For all telephone switchboards having a line capacity exceeding 200, lamp 
 signals for both line and supervision are supplied. Where the line capacity 
 of tlie switchboard is between 100 and 400, it is constructed for operation by 
 two operators (two-position switchboard), although provision is made whereby 
 one operator may use eitlier operator's set for operation of tlie wliole switch- 
 board by merely closing a switch. Tliis arrangement is made in order that one 
 man only need be kept on duty during period tliat few calls are made. 
 
 The only size above 300-line capacity that has been furnished by the Signal 
 Corps is 600-line. This switchboard is a three-position (three operators) 
 multiple switchboard of commercial type. The two outside positions are mul- 
 tipled. This means that either of the two outside operators may plug into 
 jacks connected to each of the lines terminating at the other's position. These 
 jacks are mounted directly above the regular line jaclcs. The operator at 
 
 RiMGiNG CIRCUIT 
 
 Fig. 6-15.— SWITCHBOARD, TELEPHONE, LAMP LINE AND LAMP SUPERVISORY 
 
 NALS, CIRCUITS. 
 (1-20) 
 
 SIG-
 
 Post Telephone Systems. — Chapter 6. 
 
 17 
 
 central position is alile to reach tlie line jacks of either of the other positions, 
 coiisejpiently the niultiiile jacks are not fiirnislied for liiis jiosition. 
 
 The princi[)al cii-cnits of all teieplione s\vI1(1iIiomi-(Is ahovc I he 'JiKi-liiif size 
 furnishi'il by the Sitrnal C\irps are similar, anil are shown in tijrnrcs C 1."i and 
 C-IG, while by referring to figure 6-17, u view of a 3(X)-line switchboar<l with dis- 
 tribiiting frame installed about S feet from switchboard may be seen. Figure G-3 
 shows this same distributing frame upon which are mounted strips supporting 
 
 e la mp No. O 
 
 ^/W\ I Pu^h button in 
 Sj U \tirte jocM position 
 
 TEST CIRCUIT IN NO. O LINE POSITION 
 
 Fi?. 6-16.— SWITCHBOARD, TELEPHONE, LAMP LINE AND LAMP SUPERVISORY SIG- 
 NALS, TEST CIRCUIT. 
 
 Fig. 6-1 7. — raVv I i k. ri bw« rs lj 
 
 ..^rHONE, LAMP LII,L / 
 NALS. IN OPERATION. 
 
 (227)
 
 IS 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 metal punchings to which inconuiif;- lines are terminated, also the protectors 
 previously described in this chapter. The cross-connecting of the lines to 
 protectors in this installation was accomplished hy usinji i)othead wire, and 
 tlie switchboard cables from protectors to switchboard were encased in an 
 oak runway, supported by 1 by 5 inch iron pieces. 
 
 In addition to tlie equipment herein described for switchboards, all size.s 
 above the 200-line size are usually equipped with a number of special relays 
 used in the operation of lines connected to the common battery circuits of 
 commercial exchanges. It must be borne in mind that in making such a 
 connection the common battei*y of the connnercial exchange is connected to 
 the line which is connected to the Signal Corps switchboard, also that super- 
 vision at both switchboards must be maintained. This is accomplished by 
 means of a locking relay for each such line connected to Government switch- 
 board. 
 
 Any of the switchboard cords may be used for connection with jacks asso- 
 ciated with these relays. The circuits usually employed with these locking 
 relavs aiv shown in tigni-(> 0-18. Tn ti-aciiig these circuits it will be noted 
 
 
 i 
 
 
 3 
 
 B.T^ 
 
 B..^e.B - 
 
 
 
 + 
 
 
 
 
 
 t 
 
 
 GROUND 
 
 bob bAR 
 
 
 PILOT LAMP 
 
 1 ; ^ 
 
 ^ 
 
 -o\ 
 
 ..,«. 
 
 f 
 
 ? 
 
 
 
 
 1 7/7//, I 
 
 7J7/J f/fff 
 
 ra 
 
 ZX2' 
 
 Ofrt &AITCR* 
 
 Fig. 6-18.— SWITCHBOARD, TELEPHONE, LOCKING RELAYS, CIRCUITS. 
 
 that a condenser prevents the connnon battery of the commercial exchange 
 cdiiiplcting a circuit through connnon l)a(tery of (Jovernment exchange when 
 the cord plug of Government exchange is inserted in trunk jack. Also, that 
 when the openitor of the commercial exchange impresses a ringing current 
 upon the line in the usual maimer, one winding of the locking relay is in 
 the circuit. This causes armature of locking relay to vibrate, due to ringing 
 current being alternating in chara<'ter. A slight vibi'atory movement of the 
 armature closes a coiitact, wliicii in turn closes a circuit consisting of the other 
 winding of relay in i)ai'allel with tnnd<-line lamp and pilot relay in series 
 and the combination In series circuit with the connnon battery of Government 
 exchange. The trunk-line lamp remains lighted when connnercial operator 
 ceases to ring, due to armature of locking relay beinj; held in contact by the 
 direct current. 
 
 When Goveriniient oi»erator withdraws cord plug from jack, upper contact 
 of jack is broken, and the sujiervisory lamj) of c<»nnnercial switchboard is 
 thereby lighted. 
 
 For Government operator to call commercial operator, it is diily ncu-essary 
 t«) insert cord plug in one of the trunk jacks. This operation signals the com- 
 mercial oi»erator in exactly the same manner as removing receiver from hook 
 of a telej)hone. 
 
 (228)
 
 Post TelepKone Systems. — Chapter 6. 
 
 19 
 
 (229)
 
 20 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 Supervision at Government switchboard is aecomplislied by niean« of super- 
 visory lamp in one side only of cord circiut. 
 
 Figure 6-19 shows the principal circuits in one diaurain of laiiiii-liiic signals 
 and lamp-supervisory signals switchboard. 
 
 FRONT VIEW VERTICAL SECTION 
 
 Fig. 6-20.— SWITCHBOARD, TELEPHONE, LOCAL BATTERY TYPE, 15 LINE. 
 
 CJ.-'.O)
 
 Post Telephone Systems. — Chapter 6. 
 
 21 
 
 MAGNETO SWITt'IIBOAKD.S (LOCAL BATTEKV TYl'K). 
 
 MaRiiPto s\vitcli!)(>;inls, or lociil battery type, are usually provided for small 
 l)osts and for temporary iustallati(»ns where conditious at post do not warrant 
 ttie installation of the standai'd couuuon battery system. 
 
 The operation and mainti'njince of such systems is nmiparalively sinii»le. 
 They may consist of a mininnim of 12 telephones. 
 
 For the small installations, the Siirnal Corps has applie<l a l."»-droii suii.li- 
 board. These were made under Siirnal Co/ps speciticatious and are shown in 
 figures 6-20 and fi-21. 
 
 Night bell 
 
 yOrvceJ/i 
 
 Drop 
 
 n^5 
 
 S^ 
 
 Jack 
 Drop 
 
 Jack 
 
 Mason or^csie.' 
 
 I O Q -SO 
 
 O ' I 
 
 Cords should conned:, in fast£ners Up to bp and skeve to sk^ve, 
 ground lines coming in on long c- ' ■■'•i 
 
 Fig. 6-21.— SWITCHBOARD. TELEPHONE, LOCAL BATTERY TYPE, 15 LINE, CIRCUITS. 
 
 This .switchboard consists of a neat oak cabinet accommodating! !"> combined 
 drops and .jacks. 5 pairs of cords with clearinj:-out drops, and "i jrroupint: jacks. 
 The operator is provided with a sinj:le head receiver, and the switchboard has 
 an adjustable operator's transmitter and the usual night-bell circuit. 
 
 (231)
 
 22 Signal Corps Manual No. 3. — Chapter 6. 
 
 An arrester cabinet providing for an ultimate installation of 20 Mason or 
 similar lightning arresters with fuses accompanies this switchboard, sufficient 
 cable being provided to reach from the usual location of the switchboard to 
 the arrester cabinet usually installed on the wall at the rear of the switch- 
 board. The operator's circuit is usually operated by 4 gravity cells. 
 
 The circuit is as follows (fig. 6-21) : 
 
 The calling party signals central by a magneto call, throwing the line drop. 
 The operator inserts an answering plug (opening the drop circuit and at the 
 same time automatically restoring drop shutter) and places key into talking 
 position. 
 
 The connection is established by inserting the calling plug into desired line 
 jack. The conversation completed, the usual ring off throws the clearing out 
 drop, signaling the operator to disconnect. All instruments operating througli 
 this board are on local battery. 
 
 (Jroupiug jacks are provided to connect several lines together by placing 
 answering plug in line jack and calling plug in grouping jack. 
 
 The operator's circuit is of the simple induction principle used in ordinary 
 telephones. 
 
 These boards are wired for 15-line di-ops only, and it is not practicable to 
 increase their line capacity without sending them to some Signal Corps supply 
 depot. It is not probable that any more of this type of board will be issued. 
 
 This board should have four cells of gravity battery, size 5 by 7, for the 
 operator's telephone, as this telephone has normally a closed circuit, and there- 
 fore dry cells or any other type of open-circuit battery should not be used 
 unless a cut-out switch is provided. 
 
 50-LINE MAtlNETO SWITCHBOARD. 
 
 For local-biittery telephone systems of more than 15 antl not exceeding 50 
 lines the Signal Corps has in service a number of local-battery magneto switch- 
 boards. These boards have an ultimate capacity of 50 lines and are so wired. 
 They are supplied to posts with 20, 30, 40, or 50 drops installed, depending upon 
 the number of telephone lines required. In this board the operator's telephone 
 is nominally a closed circuit, and four cells of gravity battery, 5 by 7 size, 
 should i)e used. 
 
 Additiouiil drops and jacks can be supplied for these boards and installed 
 with facility at any time to increase the cai)acity up to 50 lines, as the necessary 
 wiring is already complete. 
 
 This switchboard is a stock article of conniiercial use. Figures 6-22 and 
 (t-'2'.\ Illustrate the appearance and circuits of this equipment. 
 
 It has an oak cabinet and is jjrovided with hand generator, 5 pairs of 
 cords with listening and double ringing keys, bridged supervisory magneto drop 
 sigiKils. liiiiid generator and buzzer which can be cut into the ringing circuit as 
 dcsirt'd for lest, two keys for these various ringing circuits, and operator's 
 Iransniil tfi- and IicjkI rcccivci- complete. 
 
 FigUH' ()-2;{ shows the circuit of this s\\ ilchboard. It will be seen that the 
 line signal is bridged across the line jack and is cut off from both sides of 
 the line when the plug is inserted. 
 
 The cord circuit is the usual circuit with hridgiMl supervisory signal, which 
 is rung dr>wn by (lie stations coiuiectcil for ciill wIhmi tlicy ring off :it end of 
 the conversjition. 
 
 Tlic rcil keys on I he left-hand side of the keyboard arc those shown in the 
 ringing circuit. P.y throwing the key it is possible to cut the buzzer in series 
 with the ringing circuit. This is desirable when a line indicates a defective
 
 Post Telephone Systems. ^Chapter 6. 
 
 23 
 
 condition. The condition of tiie line in regard to open or short-circuited wires 
 will be indicated by the action of the buzzer, its loudness being determined 
 by the resistance in the line for a uniform rate of turning of the hand gen- 
 erator. On some of the boards the key provided for switching the ringing 
 circuit from power to hand generator, and vice versa, is so wired that it is 
 
 Fig. 6-22. SWITCHBOARD, TELEPHONE. LOCAL BATTERY TYPE. 50 LINE. 
 
 necessary when using the hand geuerat«»r to throw the key over from the 
 normal position. Inasmuch as power-i'inging current for these boards is seldom 
 available and is not provided, this key should be rewired so that the hand 
 generator is connected directly into the ringing circuit while the key is in its 
 normal position. 
 
 (233)
 
 24 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 If power ciirivnt should he avaihihle. it sliouhl he connected to the si)rinffs 
 marked " generator. Xos. 1 and 2." on the terminal board of the switchboard 
 and the Ivey circuit retained in its present form. 
 
 Ans Orange 
 
 Green 
 
 Call 
 
 White 
 Plug Ooublc ^ i'\Qirio\ Apy 
 
 White 
 Us teninq KGy 
 
 Plug 
 
 , '1 Bh.r p^ 
 
 /d ng'ing Buzzer Night bell 
 6h.Ctq Hey. key 
 
 o — , 
 Supervisory drop 
 
 No. S>4 Key 
 
 Ringing R>Y^er H^ 
 
 ^^^WJ' 
 
 Line drop 
 
 *— AWWA^ 
 
 P^iver clips 
 
 3-4 Trans battery ^\ CiAfund 
 
 5-6 Night bell battery ^\ — ^ 
 1-8 Telcplionc top 
 
 Fig. 6-23.— SWITCHBOARD, TELEPHONE, LOCAL BATTERY TYPE, 50-LINE, CIRCUITS. 
 
 7l lias also been found in some cases that the .generator armatures of these 
 switcliboai'ds contiinie to revolve after a call has l>(>en made, thus unscrewiu.ii 
 the genei'ator handle Iroui the drivin.u shaft. To avoid this a liigh resistance 
 will be prox ided to be bridged across ternnnals X and Y of tln' hand ,i:tMierator 
 shown in tigure 6-23, in order to furinsh a slight load for (he gt'uerator and 
 cause the armature to stop as soon as the .generator handle is released. A 
 requisition should be made for these resistances wherever their use is con- 
 sidered to be of advantage. 
 
 i'i-.A)
 
 Post Telephone Systems. — Chapter 6. 
 
 25 
 
 COUKI.ICSS SWlTCIinO.UM). 
 
 Figures 6-24 and 6-25 sIkiw a si^ecial cordloss magneto type switclihoard 
 designed to meet special conditions tliat ol)tained in connection witli tiie in- 
 stallation of a post telephone system at the Army Remount Depot near Front 
 Royal, Va. 
 
 As it was impracticable to furnish a switchboard operator in this instance, 
 the switchboard is operated by a clerk during ofTice hours and a watchman at 
 other times. The switchboard is supported by a table placed beside the clerk's 
 desk. 
 
 Fig. 6-24.— SWITCHBOARD, TELEPHONE, LOCAL BATTERY, CORDLESS. 
 
 It is only necessary to operate keys to obtain desired cross connections. 
 The switchboard is of 2U-line capacity and. as shown in the figures, the 
 operator's set consists of an ordinary telephone desk stand with hand receiver. 
 Figure 6-26 is a circuit diagram of the switchboard. 
 
 By depressing a locking key (marked " iV.l " in figure 6-24) a small bu/zer 
 contained in the cabinet is so connected in circuit that the buzzer will operate 
 when a call is received. By depressing an additional locking key (marked 
 "EXT" in fig. 6-24) the buzzer is cut out of circuit and a loud ringing 
 water-tight bell, located outside of the administration building, is made to 
 operate when a call is received. The latter is used to notify the watchman, 
 who is required to make regular rounds of the post at night. 
 
 The operator's circuit and bell and buzzer alarm are operated by means ol 
 No. 6 reserve dry cells contained in the cabinet of the switchboard. 
 
 46581°— 17- 
 
 (235)
 
 26 
 
 Signal Corps Manual No. 3.— Chapter 6. 
 
 Fig. 6-25.— SWITCHBOARD. TELEPHONE, LOCAL BATTERY, CORDLESS, OPEN. 
 INSTALLATION OF TELEPHONE SWITCHBOARDS. 
 
 Care should be taken in unpacking switcliboard apparatus so that it will 
 not be injured. Different manufacturers use various methods of packing ma- 
 terial SO it will not be injured in transit. Braces will be found in the packing 
 which must be removed as the material is taken out. If the apparatus is 
 found to be in an injured condition, note should immediately be made of this 
 fact, witnesses called in for verification, and a report immediately submitted 
 so that proper action may be taken. 
 
 ._:.i..t^ 4- — ij I „ K i ■ w 1 1 1 
 
 Fig. 6-26.— SWITCHBOARD, TELEPHONE, LOCAL BATTERY, CORDLESS, CIRCUITS.
 
 Post Telephone Systems. — Chapter 6. 27 
 
 The cord wci^ilits an* usually lied up and fasttMU'd. Uclays which hnw metal 
 covers are usually tilled with paper so tliat the relay will not be injured by 
 shaking. The apparatus should be given a thorough cleaning and cleared with 
 a bellows. Care should be taken that not any of the extra parts are thrown 
 away with the excelsior or other packing materials. All fuses should be 
 tested and care taken with the remainder of the apparatus. 
 
 Blue prints and instructions usually accompany each switchboard, and these 
 should be followed in the erection of the material. 
 
 Telephone switchboai'ds for post systems are usually installed in the ad- 
 ministration building, as stated in General Orders, No. .j, War Department, 
 ]J)i;i. 4n selecting the location consideration should be given the following 
 requirements in order tt) insure good telephone service: The room .selected 
 should be quiet and free from intruders, so that the operator's attention may 
 not be diverted from his dutie.s. Sleeping quarters for the operators are also 
 desirable if all-night service is contemitlated. The necessity of rvuming the 
 lead-covered cables from the switchboard room to the outside circ\iits sbouhl 
 also be remembered, as the protector equipment must always be located in the 
 same room with the switchboard. 
 
 The switchboard shoui<l be located so that the light falls on the front of the 
 board and so that the operator is not compelled to, face a strong light. The 
 back of the boards that ai'e not built for installation on the wall and hinged to 
 swing out for inspection should never be nearer than 2 feet to the wall so that 
 the wiring is always accessible for inspection. 
 
 Switchboard cable is invariably used for connecting appropriate line termi- 
 nals in switchboards with associated protectors in protector cabinet or on dis- 
 tributing frames. 
 
 The standard Signal Corps switchboard cable consists of 20 twisted pairs of 
 conductors, with one spare pair and one odd wire. The conductors are of soft 
 copper wire, 25.3 mils diameter, insulated by two wi-appings of silk applied 
 spirally in reverse directions, and a wrapping of cotton. The twisted pairs are 
 assembled, imi)regnated with beeswax and wrapped with cotton, then a wraj)- 
 ping of paper, a layer of tin or lead foil wrapped spirally and lapped, another 
 wrapping of heavy paper, a wrapping of cotton, and a heavy, close braid of 
 cotton treated with fireproof slate-colored paint. The cotton wrapping of one 
 conductor of each pair is white, and the other a color conforming to table 
 which follows. In connecting this cable, the following arrangement of colors 
 should always be adhered to. Under no conditions should any other sequence 
 of colors be followed, as this arrangement is standard, and is a very important 
 guide to the repair man who maintains the system. 
 
 SWITCHBOARD CABLE. fOl.OK SC HKME. 
 
 First pair Blue. White. 
 
 Second pair Orange. White. 
 
 Third pair Green. White. 
 
 Fourth pair Brown. White. 
 
 Fifth pair Slate. White. 
 
 Sixth pair -■ Blue-white. White. 
 
 Seventh pair Blue-orange. White. 
 
 Eighth pair Blue-green. White. 
 
 Ninth pair Hiue-browu. White. 
 
 Tenth pair Blue-slate. White. 
 
 Eleventh pair Orange-white. White. 
 
 Twelfth pair_,— _, Orange-green. White. 
 
 (237)
 
 28 Signal Corps Manual No. 3. — Chapter 6. 
 
 Thirteenth pair OraniLie-hrown. Wliite, 
 
 Fourteenth pair Orange-shite. White. 
 
 Fifteenth pair ^ Green-white. White. 
 
 Sixteenth pair Green-brown. White. 
 
 Seventeenth pair Green-slate. White. 
 
 Eighteenth pair Brown-white. White. 
 
 Nineteenth pair Brown-shite. White. 
 
 Twentieth pair Slate-white. White. 
 
 Ordinarily switchboards are not provided with the switchboartl cables con- 
 nected, and requisitions should specify the length of cable required to reach 
 the protector cabinet. The line cable should be neatly formed as directed in 
 a later paragraph and carefully soUlered to the line terminals, care being 
 taken to make well-tinned joints, as often the resin deposited when soldering 
 is mistaken for solder, and also that corresponding wires of the line cable 
 pairs are connected to similar sides of the switdiboni-d lines. In connecting 
 the line cables to the protector cabinet the method adopled must be such that 
 there will be no likelihood of the cable becoming wet wlien I be lloor is scrubbed 
 or in any other way. For this reason, if the cable is run luider tlu' tloor, 
 provision should be made for tliis contingency, as the line cables usmdly ju'o- 
 vided and a<l(ipted for this work have no particular moisture-resisting properties. 
 
 The outside line cables should be potlieaded above the tloor, the wiped joint 
 resting on the floor and taking up any strain tliat might othex'wise be upon 
 the connections in the terminal or protector cabinet. For magneto switch- 
 boards which have separate protector cabinets installed on the wall and apart 
 from the switchboard proper, the top of the pothead sleeve should terminate 
 just inside the bottom of the cabinet and pothead should be clamped securely 
 to blocks on wall and protected from injury. 
 
 Inside the cabinet the wires should be foi-med ami laced and iiermaiiently 
 held in ])lacc by small leather strajis so tlint Ibc woi"k js permanent in every 
 way. 
 
 f 
 
 mmti 
 
 Fig. 6-27.— SWITCHBOARD, TELEPHONE, FORMING CABLE CONDUCTORS. 
 
 All telephone switchboards should be installed in a i)ermanenl manner and 
 the schenu; of wiring followed which will nnnimize trouble in maintenance 
 work. 
 
 The telei)hone switchboard should always be bolted to the floor so that it 
 will be held itermanenlly in lis ixisition and also because the boards are usually 
 top-heavy and not intended to stand uiisui»ported. 
 
 The nt'cessary r-oi-d. magneto, line, and biis-baf condensers are installed at 
 the rear of the <-entral energy switchboards. A diagram showing the arrange- 
 ment (tf Ibis jii)i»aralus is iirovided with the dilferent brtards. Forms should be 
 made for these comiecti(nis, allowing as nuich slack as possible Coi- emergencies. 
 
 In wiring thntugb the lloors jtorcelain lubes of ami>le size shoidd be made 
 U.se of, and gr<'at ('are should be taUen in all the cabling (hat no damage may
 
 Post Telephone Systems. — Chapter 6. 
 
 29 
 
 result to the installation Iroiii carelessness on (lif |iarl of the occupants of 
 till' liuildiii;," ill wliifh the hoard is installed. 
 
 Wlicic cnlilc luriiis are reciuired, and |»arti<idail.v at tlir ends dl' (he cahlc 
 wliicli is to he u.'^ed to eoniiect tiic liiic wires lo liic .inH'stcr strips, ("liilf fitniis 
 sliduld lie made up as follows: 
 
 After the eahle is laid in its iiernianent position its free ends siiall he laid 
 parallel to terminals to which it is to he attached. The end of the cable 
 should extend a distance X (tig. 6-27) heyond the top clip of the strip. At the 
 hottom of the strip a butt niai*k should be made about an inch lielow the lower- 
 most clip, to which this cable is to be attached. 
 
 The outer covering of the cables should then he removed from the butt mark. 
 so as to expose the twisted pairs. This is accomiilished liy the use of a sharp 
 
 Fig. 6-28.— SWITCHBOARD, TELEPHONE, FORMING CABLE CONDUCTORS. 
 
 hnife, being careful not to cut the insulation of the wires. The knife should be 
 held in a slanting dix'ection to the cross section of the cable in this operation. 
 In cutting the cable around the butt mark, so as to leave a clean end. care 
 should be taken not to cut the insulation or damage the wires. All iiinding 
 strips should be removed with the sheath from the cable. 
 
 A strij) of cotton tape one-half of an inch in width should now be bound 
 ti.iihtly around the exposed edges of the cable covering. The operation of biiid- 
 
 • CABLCCLAt'' 
 
 ^ TWISTCD PWW - CONDUCTORS 
 
 Fig. 6-29, — SWITCHBOARD, TELEPHONE, FORMING CABLE CONDUCTORS, 
 
 ing the cable at this point is known as " butting " and should proceed as shown 
 in figure G-28. The tape is first looped, and then its long end is wound around 
 the cable four or five times and threaded throu.gh the loop which was tirst 
 formed. The end B is then drawn under the turns by pulling the end .4 and 
 closing the loop. Next, the loose ends :ire cut away and a coating of shellac is 
 
 (239)
 
 30 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 applied, completing the butt. Tlie exposed twisted pairs of the standard 
 switchboard cable should now be put in boiling yellow beeswax np to the butt 
 until all the bubbles disappear from the liquid. The purpose of this wax is to 
 expel all moisture and improve the insulation of the wires, and also to prevent 
 the braid loosening iip while the form is being completed. All siuiilus wax 
 should be gently beaten from the cable with a stick when it is removed from 
 the boiling pan. 
 
 The cable is now clamped at the butt lo the board, as shown in figure 6-29. 
 and each pair of wires is selected in numerical order, according to the color 
 code, dyed in the insulation of the conductor, and drawn into place and 
 fastened around each successive nail. The length of wire allowed between 
 the stem of the cable and the nails is always in excess of that necessary to 
 )-each the clips that must be connected. A spare pair of wires is left project- 
 ing at the end of the cable, so that it may be used in case any one of the 
 
 PACKERS NEEDLt 
 
 Fig. 6-30.— SWITCHBOARD, TELEPHONE, FORMING CABLE CONDUCTORS. 
 
 regular pairs becomes defective. The formed part of Ihe cable is sewed u]) 
 with a stout waxed linen twine liy Ihe aid of a 4-ineli packer's needle, wliich 
 facilitates the passing of the twine under the bunches of wire. 
 
 This needle, with the method of tlirea<ling it, is shown in figure 6-30. Re- 
 fore sewing up, three turns of twine should be taken next to the butt, drawn 
 up taut, and tied with the knot sliown, in which •« is the needle end of the 
 twine and b the short end. All line wires are bound together from this point 
 to the end of the twine with what is called a lock stitch, shown in figure 6-30. 
 
 A stitch is taken at each nail, and if the space between is over 1 inch an 
 extra stitch should be taken. In making the stitch the needle is passed und(>r 
 the wires and througii a loop, as sliown in figure 6-31, being careful not to 
 include In the loop tlie stitched part. Tiie loop sliouid liold without fastening 
 after being completed. The last stitch is reinforced by a knot, </, after which 
 it is preferable to take another stitch and knot h around the spare wires and 
 the other side of the last regular pair. 
 
 Before taking the cable from the forming board Ibe ends of the wires 
 should be cut off even and the Insulation removed from the ends of <>:ich, 
 using the line S L, figure 6-29, as a gui<ie. 
 
 (240)
 
 Post Telephone Systems. — Chapter 6. 
 
 31 
 
 The skinnins should be done with a sliarp knile, drawing it from the line 
 S L toward tlie end of the wire, at the same time pulling olT the covering, 
 which will slip off as soon as the threads are severed. Great care must be 
 taken not to nick the wire, as it would then be liable to break at this point 
 upon being moved or handled. 
 
 The tips sh(juhl now be shellacked lightly and allowed to dry. This pre- 
 vents unraveling of insulation when soldering. 
 
 If the wires are to be soldered to the terminal clips, their bare ends should 
 be threaded, through the holes in the clips, up to the insulation and bent 
 back. If no holes are provided, they should be wound close around the 
 notched portion of the clip. Care must be taken to get the insulation out 
 of the notch in the clip or the hole. Only resin solder should be used in 
 making soldered joints. After soldering, the free end of the wire should be 
 cut off close to the clip and each joint tested. 
 
 The cable should now be strapped in place with leather saddles. When 
 the forms are installed they may be finished with a coat of white shellac, 
 which keeps the dust and dirt from sticking to the wires due to their having 
 been boihMl in beeswax. 
 
 Fig. 6-31.— SWITCHBOARD, TELEPHONE, FORMING CABLE CONDUCTORS. 
 
 For the central energy board of from 50 to 100 line capacity, the switch- 
 board cables are sometimes furnished as part of the switchboard, which is 
 usually received with these cables connected to the terminal strips on the 
 back and of sufficient length to reach into the protector cabinet which is 
 erected next to and as part of the switchboard. The code scheme given is 
 followed in all ^switchboard wiring, but it is sometimes impossible to make up 
 the cable for the protector strip on a temporary form. However, this is 
 easily met as follow^s: 
 
 All cables are butted, as previously described, at the bottom of the arrester 
 strip, after cables are measured off for their permanent position. The wires are 
 then boiled in beeswax, as instructed, and each pair brought through the forming 
 holes of the protector strip in the same order as their connection to line 
 signals. That is, the No. 1 signal is connected to the No. 1 arrester, then 
 when all wires are in place the cables are laced into one stem and the whole 
 shellacked and soldered as in the first case. By this method the arrester 
 strip itself is used as the form for lacing. No excess slack is allowed in this 
 form, care being taken to connect all wires correctly the first time. All extra 
 wires are run to the top of the form and dead-ended. For 200-line and 
 larger, central energy switchboards which have iron frames for supporting their 
 protectors and outside line cables terminal equipment, and which are erected 
 separate from board and some distance from it, according to local conditions, 
 
 (241)
 
 32 Signal Corps Manual No. 3. — Chapter 6. 
 
 switchboard cables are not provided. Tliese must l)e made up locally to meet 
 the conditions. 
 
 The switchboard will be supplied with one or more spare jacks and drojts. 
 One of these jacks should be used for the purpose of testing cords. The magneto 
 line signal shoidd be disconnected from the spare jack and a cell of dry battery 
 should be connected to its associated line terminals. When a plug is inserted 
 in this jack, and the cord is shaken, a " cut-out " will be detected by a rasping 
 noise in the operator's receiver. 
 
 The generator call drops should be adjusted so as to fall readily on about five 
 cells of dry battery. 
 
 When the switchboard is completely installed, and before it is cut over to 
 the working lines, care should be taken to test for cross talk and incorrect con- 
 nections in the circuit from the heat-coil terminals to the line jacks. Under 
 no conditions should the switchboard be put into commission when any cross 
 talk is noticeable. It will be found sometimes that the key contact fails to 
 break on the operator's listening circuit, and thus crosses the lines with the 
 other keys. Dampness in the switchboard may also cause trouble of this kind. 
 
 All power connections should be poled alike. 
 
 INSTALLATION OF PROTECTIVE APPARATUS. 
 
 It is the practice to provide protection at the switchboard room for all lines 
 entering the telephone switchboard even though not any of the line circuits are 
 exposed aerial lines. For local battery systems Mason arresters, or similar 
 individual pair arresters consisting of a fuse and a multi-discharge lightning 
 arrester, are sufficient. For central-energy systems heat coils and lightning 
 arresters are provided. 
 
 MAGNETO SWITCHBOARD PROTECTORS. 
 
 The protection for small magneto switchlioards is usually installed separately 
 from them ; in most cases on the wall near by and within sight of the operator. 
 A cabinet of the same wood and finish as the switchboard is provided for the 
 installation of the necessary number of Mason arresters. 
 
 The connections between the switchboard and the protector cabinet should be 
 made by means of switchboard cable described elsewhere in this chapter. The 
 color scheme should be carefully followed. 
 
 The forms for both the switchboard and protector ends should be carefully 
 laced, each wire being brought out at its particular line spring or arrester. 
 The switchI)oard end should be carefully soldered after the wire is passed 
 through the hole and wrapped around the spring. The forms srtould be treated 
 in a similar manner to that described for common-battery switchboards. 
 
 If the switchboard cable is installed under floor, it should be run through 
 bottom of switchboard, coming up directly under the point of arrester cabinet 
 it is desired to enter, protecting it with loricated conduit between the floor and 
 cabinet, and nnder the floor provision should be made to protect the cable from 
 moisture. 
 
 The outsid(> lines should always be brought into the oflice and cabinet in 
 cable, even though the length of calile is short. If over 12 pair in size this 
 cable will necessarily be pajter insulation with lead sheath, and .should be pot- 
 headed at both ends to terminate the conductors in rubber insulation. The 
 method of pot heading is described in chapter 4. The pot-head sleeve should 
 extend into the protector cabinet and be protected by loi'icated c(>nduit or 
 frame constrwction between the floor and cabinet. Inside the cabinet the pot- 
 iK'ad wires should be carefully laced aflci- the wires are bi'ought out to their 
 respective arresters. 
 
 (242)
 
 Post Telephone Systems. — Chapter 6. 33 
 
 These forms slioukl l»e thorouylily sliollacked after tliey are formed, laced, 
 and tied in place. Never i)our liot i»araftin over forms of pot-iioad wire as tlie 
 rubber insulation wuuli! !•<■ injured by such aetion. 
 
 (KNTKAI, K.\KK(iV SWITCHBOARD I'KOTECTOKS. 
 
 One pair of lijilitninj,' iirresters and heat coils, as shown in figures 6-8 and 
 6-9, are provided for each line, both central energy and magneto. In addition 
 a strip for terminating the outside cable pairs is provided which usually ex- ■ 
 ceeds tlie arrester pairs by 80 per cent, as nece.ssarily more outside <-ab!e pairs 
 are installed than will be actually used by lines. 
 
 These arrester and line strips for the 50 and 100 line .switchboards are in- 
 stalled in a cabinet such as is shown in figure 6-32. 
 
 The cabinet shown is erected against the telephone switchboard and bolted 
 thereto so that in effect they comprise one cabinet or fixture. The local con- 
 ditions may affect their relative positions, but the door of the protector cabinet 
 can be hinged on either side and the strips changed inside so any condition can 
 be met. 
 
 The two cabinets are exactly alike in finish and essential dimensions and 
 built to be erected together. 
 
 The switchboard cables from the 50 and 100 line switchboards are usually 
 connected to that end when received, and sufficient length allowed for connect- 
 ing to the arrester strip in the protector cabinet, to which they are run by 
 cutting a hole in the bottom of the partitions between the two cabinets, and 
 lacing the cables together. 
 
 The switchboard cables are " butted " and formed as described in this chapter, 
 the color code being followed carefully, and corresponding numbers on the arrester 
 strip assigned to line signals of same number. The magneto drops ai"e con- 
 nected innnediately below the central energy lines, allowing for full capacity of 
 the switchboard. The full protector equipment iff furnished in the protector 
 cabinet for each central energy switchboard. 
 
 The 20-pair cables are boiled in beeswax preferably, or paraffin if necessary, 
 and laced up into one form and strapped securely to the back of strip on whieh 
 arresters are mounted, as shown in figure 6-32. The wires should.be carefully 
 soldered to the springs, first wrapping the wire around notch, which is alreaily 
 tinned. ' ' 
 
 Switchboard cable sometimes supplied by manufacturers with switchboards is 
 insulated with two silk and one cotton covering and has no particular moisture- 
 resisting qualities. It should never be installed under a fioor where it may 
 become wet from scrubbing or by any other means. It will retain its insulation 
 when installed in a dry room, but it is not intended for exposure. Neither 
 should this type of cable be used for potheading the outside line cables. 
 
 The cables to the outside circuits shou'd lie brought to the cabinet in the most 
 workmanlike manner that will meet the local conditions. It is usually possible 
 to bring them into the switchboard room directly under the cabinet by running 
 in walls and under floors. Whenever the cables are exjio-sed in the headquarters 
 building they should be protected by loricated coniluits or frame runway. In 
 terminal cabinets they should be potheaded directly inider the line terminal 
 strip and arranged to be strapped to the horizontal angle-iron piece holding 
 the arrester and line terminal strips. It may be necessary to move this iron 
 toward the front of the cabinet or provide a new iron strap, as the space usually 
 left between the iron strip furnished and the removable rear door is insufficient 
 for the cable. The potheads and wiped splices shoulil rest directly on the floor 
 of the cabinet and thus take up any strain that may be on the cable. 
 
 (243)
 
 34 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 Signal Corps pothead wire should always be used for these potheads, and 
 where several cables are brought in they are laced into one form on the back of 
 the line-terminal strip to which they are connected. 
 
 Rubber-insulated wires should never be boiled in beeswax or paraffin, but the 
 forms should be shellacked after they are laced and soldered in. 
 
 The potheads should be carefully aligned when installed and an effort made 
 to use sleeves of the same length and diameter, so that the tops will be level 
 when they ai"e completed. 
 
 Fig. 6-32.— SWITCHBOARD, TELEPHONE, 50-100 LINE AND PROTECTOR CABINET. 
 
 It will be found desirable to install the arrester cabinet on the right-hand 
 side of switchboard, facing it, as this will bring the cros.s-connecting springs 
 for intercoiuiecting the switcliboard cables terminating on the light iiiiig arresters, 
 and therefore the outside line cables, next to each other, simplifying the cross- 
 corniection work. 
 
 This will n'(niii'e that liic door he hinged on llic rigiit side. An illustration 
 of this type Is .shown in figure G-32. 
 
 (244)
 
 Post Telephone Systems. — Chapter 6. 
 
 :^5 
 
 Outsido liiip cables art' lirou.ulit to tlu' main inm I'raiiies i»i-<tvi.l<-<l U,r liiMi-linc 
 boards in tbc saiiu' maniUT used for sinaHcr s\\ itdibdards. 
 
 At tbc main framt- tbe caljies arc lir(»n;rbt tlwoii^ii tbc lioor in a positinri 
 depending on tlic 20-pair line Itlocks to wiiicii tlicy arc assiy;ticd. 
 
 'I'lic pol beads rest on tlie floor and are l)rou;,dit ui» lieside tiie vertical line 
 of iron braces holding: tbc line blocks to \vlii<-li tin- cables are connected. The 
 cables to be connected to tbe top line terminals will naturally be l)rou{,'lit ia 
 farthest from the bottom block. The potheads should preferal)ly be of same 
 size and height of sleeve and the wires carefully laced and shellacked when 
 formed and in place. The form should be carried straif^bt up and branched to 
 the blocks at the iron braces, to which tliey should be neatly fastened by tajte. 
 
 The line blocks number from the top down, and spare blocks siiould ordinarily 
 be left at the bottom. A cable should be distributed on on«' vertical row of line 
 terminal blocks. 
 
 POWER EQUlPifEXT FOR COMMON HATTERY POST TELEPHONE .SYSTEMS. 
 
 The necessary current for the operation of a conmion battery or central 
 energy telephone .system is obtained from one or more storage batteries. These 
 batteries and all necessary apparatus used in charging them should be given 
 consideration when tbe installation of a common battery telephone i^y.steni is 
 contemplated. 
 
 The power equipment is one of the most important features of the common 
 battery telephone system, and particular care must be exercisetl in its installa- 
 tion to insure reliability of service, as failure of the battery renders the entire 
 system inoperative. 
 
 At Coast Artillery posts current for the operation of post telephone system 
 is usually obtained from storage battery installed in the fire-control switch- 
 board room in connection with the fire-control system. Tliese batteries are 
 usually of either 80 or 1120 ampere hour capacity, depending upon the size of the 
 fire-control system. 
 
 The administration building, where the post telephone switchboard is located, 
 may be a considerable distance from the tire-control switchboard room, and the 
 number of i)airs in a cable necessary for a suitable battery feed under such 
 conditions would be determined by consulting the following table : 
 
 Number of circuits in use simultaneously. 12345678 
 
 10 
 
 Number of pairs required. No. 1'.' 
 
 Distance from battery: 
 
 fyOO feet 
 
 l.OOOfeet 
 
 l,.')00feet 
 
 2.000feet 
 
 2,o00 feet 
 
 3,000feet 
 
 3,.500feet 
 
 4,0nOfeet 
 
 1,500 feet 
 
 5,000 feet 
 
 5,500 feet 
 
 6,000 feet 
 
 (),500 feet 
 
 7,000 feet 
 
 7,500 feet 
 
 8,000feet 
 
 8,500 feet 
 
 9,000 feet 
 
 9,500 feet 
 
 10,000 feet 
 
 
 1 
 
 
 
 , 
 
 
 
 
 , 
 
 
 
 1 
 
 f 
 
 1 
 
 2 
 
 2 
 
 2 
 
 •) 
 
 
 
 1 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 L' 
 
 
 
 2 
 
 2 
 
 2 
 
 2 
 
 o 
 
 3 
 
 
 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 3 
 
 
 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 3 
 
 
 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 
 
 
 2 
 
 2 
 
 3 
 
 4 
 
 4 
 
 4 
 
 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 5 
 
 
 
 2 
 
 2 
 
 3 
 
 4 
 
 4 
 
 5 
 
 .S 
 
 (1 
 
 
 2 
 
 2 
 
 3 
 
 4 
 
 .5 
 
 5 
 
 6 
 
 t") 
 
 
 2 
 
 » 
 
 3 
 
 4 
 
 5 
 
 6 
 
 fi 
 
 7 
 
 
 2 
 
 .3 
 
 3 
 
 4 
 
 5 
 
 6 
 
 
 
 
 2 
 
 .1 
 
 
 5 
 
 6 
 
 6 
 
 
 
 
 o 
 
 3 
 
 
 S 
 
 6 
 
 7 
 
 
 
 
 T 
 
 3 
 
 
 5 
 
 6 
 
 7 
 
 > 
 
 y 
 
 
 > 
 
 4 
 
 
 fi 
 
 7 
 
 / 
 
 K 
 
 ^9 1 
 
 
 ■ 
 
 1 
 
 - 
 
 fl 
 
 7 
 
 n 
 
 9 
 
 10 1 
 
 (245)
 
 36 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 With this arrangement it is well to bridge the battery feed at switchboard 
 end with a condenser of approximately 8 niicrofarids. This condenser tends 
 to short circuit the talking currents and maintain an approximately constant 
 E. M. F. at the switchboard bus bars. Condensers in each cord circuit bridged 
 across the supervisory signals also reduce the tendency to cross talk. 
 
 At posts where existing storage battery is not available one or more must 
 be supplied. It should be located as near as practicable to the switchboard 
 and, although not desirable, may be installed in the same room. When the 
 latter location is decided upon a suitable cabinet should be constructed for 
 the battery. This cabinet should be painted inside (two coats) with acid- 
 proof paint and equipped with one or more vents leading to the outside of the 
 building. Figure 6-33 shows such an installation. 
 
 Fig. 6-33.— C. B. TELEPHONE SYSTEM, POWER EQUIPMENT IN SWITCHBOARD ROOM. 
 
 Tlie ideal arrangement for the larger systems is to have :i sei)atate room, 
 well lighted and ventilated, for the storage battery alone. It can then be 
 mounted on appropriate stands where they Can be conveniently examined. 
 Next to this room should be the power switchboard room, where is located the 
 l)Ower switchboard used in controlling the power circuits, the motor generator 
 used for charging the storage battery, and the dynamotor or other apparatus 
 for furnishing the ringing current. An additional room, well lighted and ven- 
 tilated, will be required, in wliich is located the telephone switchboard and 
 distril)Uting fi-ame with all jtrotector ai)paratus. The latter room should be 
 of such size that an army bunk may be placed therein in addition to the 
 telephone ai)paratus, in order lliat a night opi'rator may sleep in proximity 
 t(i the switchboard. 
 
 Ill some inslMtices the storage-battery room siiid ]i(iW(>r-switchboard room 
 liave been foriiied by the construd ion of ;i pnrtitioii in a i-ooiii in the basement 
 of the a<Inniiistration building, thereby iiinUiiig two suitable rooms of one 
 room. Tlu! telephone switchboard and distributing frame should not be located 
 in a room the floor of which is below tlie ground level. Where the battery re- 
 (|Mlred does not exceed 24-:iini)er(' hour cajiacity the two-plate or coupled type 
 may be used, thereby niiniuiizing the amount of space necessary. 
 
 (246)
 
 Post Telephone Systems.^Ihapter 6. 
 
 37 
 
 In the past it has l)eon customary to furnisli two storage batteries in order 
 tliat one may be intermittently disconnected from tiie teleplione switchboard 
 while being charged or examined. Experience lias shown this practice to be 
 uneconomical and in future, where the battery is charged by a generator, the 
 standard equipuit'iit will be one battery (ordinarily 12 cells). If the tele- 
 phone lines are noisy during the charging of storage battery, a suitable dinke 
 coil, connected in series with one of the leads between the g('nerat(»r and 
 storage battery, will usually eliiiiiiiate sudi ;i defect. 
 
 Fig. 6-34— C. B. TELEPHONE SYSTEM, MOTOR GENERATOR. 
 
 Part 
 No. 
 
 Name. 
 
 Rpferpiice 
 
 No. 
 
 Armature, complete 
 
 Armature, dynamo 
 
 Armature, motor 
 
 Box, journal, set screws for 
 
 Boxes, journal, complete 
 
 Brush holder, dynamo, left 
 
 Brush holder, dynamo, right , 
 
 Brush holder, motor, left 
 
 Bru.sh holder, motor, right 
 
 Brush and t erniiiial stud 
 
 Brush and terminal stud, nut for , 
 
 Brush and terminal stud, brass washer for. 
 
 Brushes, dynamo 
 
 Brushes, motor 
 
 Bushing, porcelain 
 
 Coil, field, d^^^amo 
 
 Coil, field, motor (state voltage) 
 
 Connection, drawing 
 
 Coupling 
 
 Feet, rubber 
 
 Generator end, complete 
 
 >totor end. complete 
 
 Name plates 
 
 Name-plate screws 
 
 Oil cock, J-inch -. 
 
 Oil-well plugs 
 
 Pole shoe 
 
 Pole-shoe screw ... 
 
 Shield cap, screws for. 
 
 Shield, connecting 
 
 Shield, front 
 
 (247)
 
 38 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 With small Installations, where tlie storage battery is charged from a direct 
 current lighting main through lamps, two separate storage batteries will 
 invariably be installed, for, if telephone switchboard is connected to storage 
 battery being charged, the electric lighting circuit is in electrical contact 
 with all telephone lines radiating from telephone switchboard, a condition 
 which should never be permitted. 
 
 Where the post lighting system is of alternating current the storage l)at- 
 tery must necessarily be charged by means of a motor generator or suitable 
 
 °C/rcu/£ffrea/rer 
 
 "(1 
 /9eci/f/er rude 
 
 /?egu/a6/h(f Compensator 
 
 Bac/r >'/<?>*' 
 of Pane/ 
 
 ^ V Xf- 
 
 66ar6/nff 
 ffes/siance 
 
 ffeac6ance 
 
 Fig. 6-35.— C. B. TELEPHONE SYSTEM, MERCURY ARC RECTIFIER. 
 
 (248)
 
 Post Telephone Systems. — Chapter b. 
 
 39 
 
 (See fig. 6-35.) 
 
 Part 
 No. 
 
 Name. 
 
 Panel, control 
 
 Panel, control, supporting frame for. 
 
 Circuit breaker, C. G. type 
 
 Ammeter 
 
 Voltmeter 
 
 Switch, S. P. D. T., combined start- 
 ing and load 
 
 Switch, S. P. S. T. (au.xiliary), for 
 starting anode circuit 
 
 Switch, D. P. S. T., for A. C. line.. 
 
 Switch, ()-point (controlled by hand- 
 wheel) 
 
 Refer- 
 ence 
 No. 
 
 Part 
 No. 
 
 Name. 
 
 Refer- 
 ence 
 No. 
 
 Switch, 11-point (controlled by hand- 
 wheel) I 10 
 
 Fu.se clip, with fuse, S. P. D. T 11 
 
 Handwhecl for tube holder ' 12 
 
 Tube holder ; 13 
 
 Tube, rectifler | 14 
 
 Resi.slante, starling load I 15 
 
 Resistance, starling anode ' 
 
 C'ompen.sator, regulating i Iti 
 
 Reactance, A. (". series 17 
 
 Transformer, insulating 
 
 current rectifier. The former is the standard method, and in lisiinu m.itHriiil 
 tor a post teleplioue system information must be furnislied concerninfr the 
 availal)le current, which will embody the following: Voltage, number of phase.^. 
 and number of cycles. Figure G-34 shows the construction of tlie motor gen- 
 erator except that the one shown is equipped with a direct-current motor. 
 
 Figure (5-35 • shows the mercury arc rectifier which has been furnislu'd in 
 special cases. 
 
 POWER SWITCHBOAEDS. 
 
 Signal Corps specification No. 519 relates to teU*iiiione imiuii >\\ lu iilmards. 
 There are five types, in order that all varying conditions can be met. Figure 
 6-86 shows the type No. 1. and figure 6-37 shows the type No. 4. Willi type 
 No. 1 the batteries are charged l)y means of lamp resistance, and with the 
 type No. 4 a motor generator is used for charging the battery. Tliese panels 
 are intended for installation about 18 inches from the wall, but their supporting 
 frames are so constructed that tliey do not have to be braced to wall, conse- 
 quently they may be placed any distance desired. 
 
 It may be necessary to install between the post electric-lighting circuit mains 
 outside of administration building and power switchboard two additional con- 
 ductors, for the reason that the electric-lighting mains to the building may be 
 of such size that they would not be capable of carrying the excess current 
 necessary for charging the storage batteries, or they may be of such size and 
 length that the excess current would occasion such tlrop in voltage that the 
 electric lights in the administration building would be dimmed. Should the 
 installation of the above-mentioned leads be resorted to, it is desirable to enter 
 the building by means of duplex power cable in undergi'ound conduit. The 
 cable should terminate in building at a fuse block which should be connecte<l 
 with a knife switch. From knife switch leads should be connected with watt- 
 hour meter before terminating at power switchboard. 
 
 Where alternating current power circuits are contained in iron conduits care 
 must be taken to install both wires in the same conduit and to have the conduit 
 grounded. 
 
 The watt-hour meter, knife switch, and fuse block referred to above will he 
 supplied by the Signal Corps and. together with material for their in.stallation. 
 should appear in estimate of apparatus necessary. Tlie fuse block and knife 
 switch should be inclosed in a metal box or. as a substitute, a wmiden box linwl 
 with asbestos. Electric current consumed in charging Signal Corps storage 
 l>atteries installed in connection with post telephone systems at interior i>osts 
 is chargeable to Signal Corps appropriaiions if obtained from a commercial 
 source.
 
 40 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 Figure 6-S3 illusti-ates an installation of the central office apparatus for a 
 small system, where direct current is available and where one room only can 
 be obtained. 
 
 With this arrangement the leads from the switchl)oards and the post power 
 should he brought up from the floor in loricated conduit fastened to the wall, 
 even with the bottom of the panel ; from this point the lead sheath is removed 
 
 1 
 
 IT'* -i 
 
 Fig. 6-36.— C. B. TELEPHONE SYSTEM, POWER SWITCHBOARD, TYPE NO. 1. 
 
 (250)
 
 Post Telephone Systems. — Chapter 6. 
 
 41 
 
 Fig. 6-37.— C. B. TELEPHONE SYSTEM. POWER SWITCHBOARD, TYPE NO. 4. 
 
 46581°— 17 17 I -5 1.1
 
 42 
 
 Signal Corps Manual No. 3.— Chapter 6. 
 
 and the wires are carried over to the connecting lugs on the rear of panel. The 
 exposed parts of the leads should be painted thoroughly with preservative 
 paint. If the storage battery cabinet is near by, the leads can be extended 
 directly to it : but if any considerable distance separates these apparatus their 
 battery leads should be lead down to the floor and then to the battery cabinet 
 in the same manner as they are lead to the panel. As previoiisly stated, lead- 
 covered cable should be used for the leads, the lead sheath being cut back at 
 the end for connections. Complete instructions for installing and applying 
 initial charge to storage batteries appear in chapter 1 of this manual. 
 
 RINGING APPAKATIS. 
 
 Ringing apparatus for furnishing ringing current for calling is sometimes fur- 
 nished with a large installation. When this apparatus is used it is only neces- 
 sary for the operator at switchboard to depress proper ringing key in order to 
 call party desired, thereby obviating the manual operation of the switchboard 
 generator. The change from dynamotor to switchboard magneto and vice versa 
 is quickly accomplished by means of special key at switchboard. The ringing 
 dynamotor has been furnished by the Signal Corps in most instances. 
 
 Telephone-power equipment is sometimes utilized for furnishing primary cur- 
 rent for the dynamotor. The current strength required for these sets furnished 
 to date is approximately 2 amperes, the motor feature of dynamotor being de- 
 signed 'for either 24-volt or 30-volt circuit. An 80-volt alternating current of 
 approximately I65 cycles is delivered at ringing keys of telephone switchboard 
 by the dynamotor. Figure 6-38 illustrates this apparatus. 
 
 10 V. A.C. 
 /6 3 cycles 
 
 To telephone switchboard 
 
 Fig. 6-38.— C. B. TCLCPHONE SYSTEM, DYNAMOTOR, RINGING, 
 (252;
 
 Post Telephone Systems. — Chapter 6. 43 
 
 The iKlvniitage in having dynaniotor operate from these voltages instead of 
 the post-power voltage is that, should the post power be cut olT, the dyuamotor 
 can be operated by the storage battery while ordinarily the storage battery 
 charging circuit could be used to operate the dynaniotor. The latter method 
 is usually inefficient, and where it is contemplated to furnish a dynaniotor, 
 using telephone-power equipment for operating it, it is advisable to furnish 
 storage battery of such capacity that the dynaniotor may be operated thereby 
 without too frequent charging. It is particularly desirable to operate the 
 dynaniotor by means of telephone-power equipment at places where power plant 
 supplying post power is not operated during daylight, a condition that com- 
 mercial telephone companies frequently have to meet. Under such conditions an 
 apparatus termed " pole changer," which is operated by primary batteries, is 
 sometimes supplied for furnishing ringing current. 
 
 Where there is a relial)Ie and continuous source i)f electric power it may be 
 advisable to ojierate the dynaniotor by means of this power. If power be 
 direct current, the motor feature of dynaniotor must be designed for the voltage 
 of the circuit available. If power be alternating current, a motor generator is 
 supplied. Thus, it will be seen that conditions should be carefully surveyed 
 before deciding upon the manner of furnishing ringing current. 
 
 TELEPHONES. 
 
 Telephones used in connection with iiost-telephone systems are of the com- 
 mercial stanilard type, and are fully described in chapter 3 of this manual. 
 
 RECORDS OF AN INSTALLATION. 
 
 It is a well-known fact that in no branch of the industrial field are records of 
 such great importance as those pertaining to electrical installations. While 
 the development of instruments and methods employed in electrical science have 
 reached a point where little time is lost in locating faults and in repairing or 
 making operative an electrical circuit that becomes inoperative, accurate records 
 facilitate to a marked degree such repairs, and are a great convenience to those 
 vested with maintenance of the systems. 
 
 The Signal Corps requires that upon completion of installation of a post- 
 telephone system, a comiilete and accurate record be prepared. This record 
 consists of standard Signal Corps forms, appropriately accomplished, and draw- 
 ings illustrating routing of cables, connections, cross connections, and special 
 circuits employed. The drawings should be made by means of waterproof ink 
 on tracing cloth. When it is impracticable to make the.se drawings at post 
 where installation is made, the data should be forwarded by person in respon- 
 sible charge of the installation to the Departmental Signal Officer of department 
 in which post is located. The Department Signal Officer will have the draw- 
 ings made, using the data furnished as a guide, if facilities are available in his 
 office. If impracticable to make the drawings in the office of the Department 
 Signal Officer, the data should be forwarded to the Chief Signal Officer of the 
 Army with request that the drawings be made. 
 
 When drawings have been approved, complete sets (prints of tracings') shall 
 be filed as follows : One in office of Chief Signal Officer of the Army ; one in 
 office of Department Signal Officer, and one or more at office of post signal offi- 
 cer. In addition, at least one copy of drawing .shown under subheading " a " 
 appearing later in this chapter shall be transmitted to the local post quarter- 
 master, that he may be familiar with location of Signal Corps cable and conduit 
 system. If there are facilities for changing the drawings (tracings) and for 
 
 (2p3)
 
 44 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 (■2-,4}
 
 Post Telephone Systems. — Chapter 6. 
 
 
 
 / 
 
 ./ 
 
 c/ 
 
 J8. 
 
 
 
 
 
 .0-.9 ■'dOff/ .. axl''^'""'^'''*nh„*«0 
 
 
 
 avi^ 
 
 
 
 
 
 5' 1 2 
 
 - S: ir -tj-^s' >f^ei/s- 
 
 Ch,e -Id-OS/ yp/r/s--»^ 
 
 'j^bSS - - - -O- - A\<"^ ''J^,MM 
 
 -a«-/ _« 
 
 (255)
 
 46 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 making prints in the office of the Department Signal Officer, tlie tracings will 
 be filed in that office, otherwise they will be filed in the office of the Chief 
 Signal Officer of the Army. 
 
 The iipkeep of these records is of utmost importance. All authorized changes, 
 regardless of their apparent insignificance, should be recorded. It is the duty of 
 post signal officers to see that all modifications of the original system are re- 
 ported to the Department Signal Officers. Upon receipt of satisfactory data, 
 showing authorized modifications of an installation, Department Signal Officers 
 will take steps to have the drawings (tracings) corrected, and each authorized 
 office furnished with corrected copy, at the same time advising all recipients 
 that the forms or drawings supersede similar ones previously furnished. 
 
 Component parts of the record are enumerated below, and the items as de- 
 scribed should be strictly adhered to in order that post signal officers ac- 
 
 
 
 Str/P */ 
 
 -. 
 
 / 
 
 3-/2 
 
 2 
 
 ^-/o 
 
 3 
 
 
 4- 
 
 ^-/2 
 
 S 
 
 3-3 
 
 6 
 
 3-4- 
 
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 7 
 
 5-/ 
 
 r3 
 
 8 
 
 3-2 
 
 9 
 
 
 V 
 
 W 
 
 
 IJ 
 
 
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 ^/>/>d *^ 
 
 i 
 
 < 
 
 / 
 
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 2 
 
 ^-5 
 
 
 5 
 
 Open 
 
 
 ^ 
 
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 cn 
 
 S 
 
 ^-// 
 
 fr> 
 
 6 
 
 
 ^ 
 
 7 
 
 
 
 8 
 
 
 9 
 
 
 1.^ 
 
 10 
 
 /-2 
 
 IW 
 
 // 
 
 2.-S 
 
 /.h< 
 
 12 
 
 /->J^ 
 
 r 
 
 <3f-n'p ^3 
 
 / 
 
 /-7 
 
 2 
 
 /-a 
 
 3 
 
 /-s 
 
 4- 
 
 /-€> 
 
 5 
 
 
 G 
 
 
 7 
 
 
 8 
 
 
 9 
 
 
 JO 
 
 
 II 
 
 
 J2 
 
 /-/ 
 
 Cable 
 3S 
 
 33 
 Cable 
 3^ 
 
 Strip ^^ 
 
 / 
 
 ^--^ 
 
 2 
 
 a-/ 
 
 3 
 
 s-s 
 
 4 
 
 
 5 
 
 
 6 
 
 
 7 
 
 
 8 
 
 
 9 
 
 
 10 
 
 
 II 
 
 
 12 
 
 
 r5t/-/p 
 
 #/ 
 
 ^U/p *^ 
 
 / 
 
 Off/cet-'i Qtn 
 
 2 
 
 Cf-ft-s Qtts 
 B/dq Si a 
 
 5 
 
 
 4 
 
 Off-i Qtf-i 
 a/at J- 3 C 
 
 5 
 
 
 G 
 
 
 7 
 
 Offrs QtrS 
 
 8 
 
 OfftS Qr/-:> 
 
 9 
 
 
 10 
 
 
 II 
 
 
 IZ 
 
 
 1 
 
 %%%%V' 
 
 a 
 
 Lau/idf)/ 
 
 3 
 
 
 4- 
 
 Off /-J on s 
 a/etg S2 
 
 5 
 
 
 6 
 
 
 7 
 
 
 8 
 
 
 9 
 
 
 /O 
 
 OttfJ iftts 
 
 // 
 
 %%'f3'i>' 
 
 12 
 
 
 Srr/A * 3 
 
 / 
 
 Oitts Oti-i 
 B/aq SI 
 
 2 
 
 OfffJ Qtr-j 
 
 5 
 
 Offi-i QtrJ 
 
 4- 
 
 OHti Qtl-S 
 3 fat 30 
 
 S 
 
 
 6 
 
 
 7 
 
 
 8 
 
 
 9 
 
 
 /O 
 
 
 // 
 
 
 12 
 
 Otfi--i OtfS 
 
 tSt/-/'p *'^ 
 
 / 
 
 %UFI^' 
 
 z 
 
 mf^' 
 
 •a 
 
 l.au/ui/f 
 
 ^ 
 
 
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 (o 
 
 
 7 
 
 
 8 
 
 
 9 
 
 
 /O 
 
 
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 Fig. 6-41. 
 
 -TELEPHONE SYSTEM, RECORD, CONNECTIONS AND CROSS CONNECTIONS 
 OF CABLE CONDUCTORS. 
 
 (266)
 
 Post Telephone Systems. — Chapter 6. 
 
 47 
 
 custonUMl to the record at (Hie pdsl will lie fainiliur as far as iiracticalile 
 with tlie records at anotlier. 
 
 manhole: No. 102. 
 
 ■Showtnc^ Location. 
 
 
 
 
 
 
 1 
 
 BARR/JCKS 
 BLDG. 248. BLDG.249. 
 
 fbunctation >vcill. 
 
 1 
 
 
 
 
 V ^H:: . 
 
 
 
 H 
 
 Manhole cover s'x inches below 
 surface, of ground 
 
 M.H. No. 102 
 Fig. 6-42.— TELEPHONE SYSTEM, RECORD. LOCATION OF MANHOLES. 
 
 (a) Drawing, map to scale, showing' routini,' of all Signal Corps cables and 
 aerial lines and the location of all substations, torniinals, and all principal 
 structures. (See fig. 6-39.) 
 
 Sfonaft i^tUry ffMn 
 
 •Fbfnr SA'hf /S~* f" 
 
 
 7i4v^S»» Sn«W ami^ Rm» 
 
 
 Fig. 6-43.~TELEPHONE SYSTEM, RECORD, ARRANGEMENT OF POWER EQUIPMENT. 
 
 (257)
 
 4£ 
 
 Signal Corps Manual No. 3.— Chapter 6. 
 
 1 
 
 y^-R»sB/lR 
 
 -ipo PkrkaC 
 
 
 =^^ 
 
 i /.//', ! 
 
 Cosfl 5 )"l'\'*'^t> *>*"■• 
 
 5oo'^J)ftoP 
 
 S.«<»-»-^' 
 
 -^ ^ 
 
 T^INO^ 
 
 Qosf(, Sti^'1a'/;o our 
 
 
 O 
 
 t^\f>iC . 
 
 ■6'p/:cifli. Ud/niivc, Di?op**JS rln Ncn/ London T/ii/Nn. 
 FoaT Ha U/f?iav>T. NlY. 
 
 TS'ei/t Bnn. Utf ofOnop PHfEt.- 
 
 ToFiiftMi'.cr Do It no 
 
 CO si\. 
 
 ^SPf^lPoM J^^'^^ 
 
 pop or SlQ.Nei,\ 
 
 ^rV3^mf\~ 
 
 -^ 
 
 T, P . -SUKi- 
 
 53 
 
 
 No or 
 
 7i-rrr>inal Beard. 
 
 Fig. 6-44.— TELEPHONE SYSTEM, RECORD, SPECIAL CIRCUITS. 
 
 (2G8I
 
 Post "1 elephone Systems. — Chapter 6. 
 
 49 
 
 (h) Drawing, diagram, not nece.ssaril.v to .scale, for each post, showing the 
 distances between all manholes and the distance between terminal manholes 
 and end of each cable terminating in adjacent stretch. This diagram should 
 show slack of each cable in each manhole, as well as location of .si»Iiees in 
 each cable. In indicating slack it may be necessary at times to have such 
 indication a minus quantity ; this is due to the fact that the amounts entered 
 should be tlu' difference between a straight line through manhole and actual 
 path taken by cable in the manhole. Diagram should also show in tabidated 
 form the number, the type, and the total length of each cMble. (See liu'. 0-40.) 
 
 1 
 
 
 > 
 
 6 
 
 O 
 
 V 
 
 Q 
 
 
 6 
 o 
 
 
 
 c +-• 
 
 +- 
 c 
 
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 t; 
 
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 ■0 
 E 
 
 ^ 
 
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 JS'. Officers 0>-a 
 
 c e ivG// 
 
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 3 
 
 
 
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 3309 
 
 
 3 
 
 4 
 
 
 A- 
 
 
 
 i'" 
 
 
 3iIZ. 
 
 
 4- 
 
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 s 
 
 
 
 j'"- 
 
 
 3XSO 
 
 
 S 
 
 <o 
 
 
 £. 
 
 
 
 Hosl^i-f-al 
 
 
 J IS/ 
 
 
 6 
 
 7 
 
 
 7 
 
 
 
 Eirct S^t 0r-s. 
 
 
 32J» 
 
 
 7 
 
 S 
 
 
 S 
 
 
 
 BaKraci^S 
 
 
 3J'3 
 
 
 8 
 
 9 
 
 
 9 
 
 
 
 Guard Avo us^ 
 
 
 J2<0 
 
 
 9 
 
 10 
 
 
 10 
 
 
 
 Pcsi Cxchancf^ 
 
 
 JiJ* 
 
 
 lO 
 
 II 
 
 
 II 
 
 
 
 
 
 
 
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 IX 
 
 
 
 1 
 
 
 Or f^oi fer Of -p. 
 
 C B Wall 
 
 3lf, 
 
 
 li. 
 
 13 
 
 
 
 2 
 
 
 Corr,m,S3^KY 
 
 
 31*1 
 
 
 ij 
 
 (4 
 
 
 
 J 
 
 
 Ord. Off- 
 
 
 3l»J 
 
 
 !*■ 
 
 IS 
 
 
 
 ■* 
 
 
 Temfo etOTocKS 
 
 Comp Vi'all 
 
 it34 
 
 
 15 
 
 16 
 
 
 
 5 
 
 
 St-y* "jr^ Ort" 
 
 C-B-^all 
 
 
 
 /*, 
 
 17 
 
 
 
 ^ 
 
 
 >lt/jJ»iir.ti Off. 
 
 C B DesK 
 
 
 
 n 
 
 It 
 
 
 
 7 
 
 
 c o o». 
 
 C B ■■ 
 
 
 
 IB 
 
 /« 
 
 
 
 S 
 
 
 A^ty f"?'. Offi 
 
 C. B IA*>// . 
 
 JJtJI 
 
 
 Fig. 6-45.— TELEPHONE SYSTEM, RECORD, CONNECTIONS, AND OTHER DATA. 
 
 If the data enumerated under this heading can be shown on map referred 
 to under heading " a "' without crowding the entries it may be done, thereby 
 eliminating additional tracing. 
 
 (c) Di-awing, not necessarily to scale, of each terminal box. submarine 
 terminal box, junction box, distributing frame, and arrester cabinet showing 
 the location of conductors of all cables terminating at that pt»int, all cross 
 connections, the use of each circuit, and all spare conductors. (See fig. 6-41.) 
 
 (d) Drawing, showing exact location of each manhole if they be of the 
 type having cover below surface. Measurements shown should be between 
 permanent substantial construction, such as nui.sonary foundations of structures, 
 if possible, and njanholes. (See fig. 6-42.) If desire*! a number of these may 
 be made on one sheet. 
 
 ((■) Drawing, not necessarily to .scale, showing arrangement of i>ower tiiuii*- 
 nieut. This is not necessary with local l)attery .sy.stems (see tig. G-43i. A 
 
 (269)
 
 50 
 
 Signal Corps Manual No. 3. — Chapter 6. 
 
 Sijinal Corps drawing of power switchlioard may he adcU'il ti> sliow cirtniits if 
 it is applicable. 
 
 (/) Drawing, not necessarily to scale, showing eacli special cin-uit if there 
 be any not shown in this manual. (See fig. 6-44.) 
 
 (g) Drawing, diagram showing post-telephone connections and other im- 
 portant data. (See fig. 6-45.) 
 
 ADMINISTRATION BUILDING 
 
 
 orricE OF COMDG. orriccp 
 
 Normol po5ihon 55 shewn* ^ 
 
 "5> 
 
 ToSriBd-Sam Nal 
 
 M 
 
 orrjCE or 
 
 StRGT MAJOR 
 
 To5w.BclSKjr. 
 
 oo 
 
 Fig. 6-46.— TELEPHONE SYSTEM, RECORD, SPECIAL ARRANGEMENT. 
 
 (70 Miscellaneous drawings and diagrams. Under this heading should be 
 included drawings or diagrams illustrating any part of the installation not 
 covered by the above and which the engineer in responsible charge of installa- 
 tion believes should be elucidated. (See fig. (3-46.) 
 
 SIGNAL CORPS FORMS. 
 
 (/.) Form No. 261 (cable record) should be accomplished in triplicate for 
 each cable of the system. 
 
 (7) Form No. 211 (report of inspection of Signal Corps equipment ) should 
 be accomplished in triplicate. As the name implies, Form No. 211 is a form 
 used in recording results of inspection. Inasnuich as this form requires a 
 great amount of information that can be nuich m(n*e readily secured at time 
 of installation of apparatus, it has been made a part of the .standard record. 
 
 (k) Form No. 209 (semiannual i-eport of post telephone e(ini])ment) slnmld 
 be accompli.shed in triplicate. This form also requires information that sliould 
 be supplied upon completion of an installation. 
 
 (/) Form No. 279 (.summary of cost of an installation) sIkhiUI be accom- 
 plislied in duplicate, one coi)y foi- ollice of Cluef Sigiuil Otlicer of the Army 
 and one for office of Department Signal Officer. 
 
 ivi) Form No. 204 (report on the progress of iiistallalioiis). During the 
 l>rf)gress of installation of a post teI(>i>hoiie system, where the work involved 
 re<iuires more than one month t<» complele. (liis form, accomi»lished in dupli- 
 cate, will be forwarded by person in i-espunsilile cliarge of woi-k lo tlie De- 
 partment Signal Officer. Th(>s(> foniis will be I'oi-warded at the end of each 
 calendar nionlii, an<l iiiion comiilcl ion of ilie work if such (■((niplflioii does not 
 occur on last <!ay of calendar monlli. < »nc of lliese forms will be filed in 
 office of Chief Signal Officer of the Army and one in office of the Department 
 Signal Officer. 
 
 (260)
 
 Post Telephone Systems. — Chapter 6. 51 
 
 (n) Form No. 210 (montlily report of einiiloyees at large). The person in 
 responsible charge of installation will collect at the end <»f each calentlar 
 month a single copy of this form, duly acconii)lishe(l, from each electrical en- 
 gineer, assistant electrical engineer, and electrical assistant engaged on the 
 work, and will forward these. forms, together with one copy of the same form 
 accomplished by himself, if he be a civilian employee of the Signal Corps, 
 to the Department Signal Officer of the department in which he is operating. 
 This form is for the hies of the office of the Chief Signal Ollicer of llw Army. 
 
 Maintk.nanck ok I'o.st Tki.ki'honk Systems. 
 
 summary of faltlts th.vr akk .most i.lkkl.y to occik a.ni) an knr.mkkatlon 
 
 of causks. 
 
 loc.\l battery ix.strl.ments. 
 
 («) L. B. station can not riiui another station. — Defective apparatus at other 
 station. Broken wire in either instrument. The coiled spring on magneto 
 driving shaft broken. Open circuit in magneto windings. Contact piece at 
 end of magneto armature shaft bent or broken. Open, crossed, or grounded 
 lines external to instrument. If any of the latter faults exist, unless line 
 is short circuited the home station should be able to ring its own ringer. 
 
 (6) L. B. station dors not receive a ring from another station. — Distant in- 
 strument defective. Home station ringer out of adjustment or permanent 
 magnet weak. Open circuit in ringer magnets or broken wire in ringer cir- 
 cuit. Failure to operate of magneto automatic cutout. Elxternal line open 
 or short circuited. 
 
 (c) L. B. station can not transmit speech to distant station. — Distant sta- 
 tion apparatus defective. Hook switch contacts out of adjustment. Local 
 battery weak or open circuit in primary circuit, including winding of induc- 
 tion coil. Open circuit in secondary winding of induction coil, receiver, re- 
 ceiver cord, or instrument wire. Packed or defective transmitter. External 
 line open or short circuited. 
 
 (d) L. B. station can not receive speech from distant station. — Distant .sta- 
 tion apparatus defective. Hook switch contacts out of adjustment or broken. 
 Defective receiver, such as open circuit in cord, windings, or diaphragm dis- 
 torted. Open circuit in secondary winding of induction coil or instrument wire. 
 External line open or short circuited. 
 
 COMMON BATTERY IXS I'RrXIENT.S. 
 
 (n) C. B. station can not sifinal siritchhoard operator. — Defective central 
 station apparatus. Common battery cut off. Hook switch contacts out of 
 adjustment or broken. Open circuit in primary winding of induction coil, 
 transmitter circuit, or instrument wiring of these circuits. Open or short 
 circuit in external line. 
 
 (6) C. B. station holds operator's signal when honk is down. — Short circuitetl 
 condenser. Hook switch contacts out of adjustment. External line short 
 circuited. 
 
 (c) C. B. station does not receive a ring. — Defective central station apiia- 
 ratus. Home station ringer out or adjustment or permanent magnet weak. 
 Open circuit in condenser. Open circuit in ringer nuignets, or broken wire in 
 ringer circuit. External line open or short circuited. 
 
 (261)
 
 52 Signal Corps Manual No. 3. — Chapter 6. 
 
 id) C. B. station can not transmit speech. — Defective central station appa- 
 ratus. Common battery cut off. Hook switch contacts out of adjustment or 
 hrolven. Open circuit in primary windin.ij of induction coil, transmitter circuit, 
 or instrument wiring of these circuits. Packed or defective tran.smitter. Ex- 
 ternal line open or short circuited. 
 
 (c) C. B. station can not receive speech from distant station. — Distant sta- 
 tion apparatus defective. Hook switch contacts out of adjustment or broken. 
 Defective receiver, such as open circuit in cord, windings, or diaphragm dis- 
 torted. Open circuit in secondary of primary winding of induction coil or 
 instrument wire. Open circuit in ti'ansmitter or transmitter cord. External 
 line open or short circuited. 
 
 (/) Speech at distant station is indistinct, scratch iiifi or firating noise in 
 receirers.—ljOOHe connections or battery too strong. (This may be noted dur- 
 ing charging of telephone storage battery.) Damaged or broken receiver cord. 
 
 Note. — In common battery transmission, if the line resistance is excessive transmis- 
 sion is weakened. Six miles of cable with conductors 36 mils diameter is considered the 
 limit of common battery supply for efficient conversnt ion. 
 
 Telephone Switchhoaru Trovbles. 
 
 summary of faults which are most common. 
 
 (a) Common batter}/ siritchhoard, visual signal is feeble. — This indicates a 
 poor adjustment in the signal armature, low battery, or high line resistance. 
 
 (b) Common battery sioitchboard, signal is irregular. — This indicates loose 
 connection either in the switchboard, switchboard cabinet, or in the external 
 circuit. May be due to defective jack contacts. 
 
 (c) Common battery switchboard, signal icill not operate. — Weak battery. 
 Broken wire in either internal or external circuit. Signal short circuited or 
 signal badly out of adjustment. 
 
 id) A grating noise noticed n-hen plug of connecting cord is in.<ierted in 
 jack. — Voltage of battery too high or partial open circuit in the connecting 
 cord. 
 
 (e) Cross talk. — If the .system is free from cross talk when installed and 
 trouble does not exi.st in the exterior sy.stem, cross talk that may develop is 
 l)robabIy due to the sticking of the listening-key contacts in switchboard, thus 
 liridging two or more lines together. ^Moisture in terminal boxes or moist wire 
 foi'ms is another condition which sometimes causes cross talk. 
 
 (/) In lamp line switchboards or in visual signal switchboards equippeil with 
 lamp supervisory signals the tirst step shoidd be to examine the relays in the 
 event of switchboard signal trouble. 
 
 With any switcliboard where it is determined that a fault exists in the central 
 station the proper procedure is to first examine tlie lieat coils pertaining to the 
 line in troui)le. Having determined that the trouble exists within the switch- 
 board, it is a simple matter to localize the fault if a person is thoroughly 
 familiar with the circuits <tf th(» .switchboard. 
 
 If the repair of a defective switchltoard circuit is urgent, it may be advisable 
 t() transfer the incoming line t<» a signal not in use, advising the switchboard 
 operator of such actif»n and reiiairing the de^fective circuit as soon as i»racticaiile 
 thereafter. 
 
 In cord switi-hltoards if the drop does not fall, test first for continuity of 
 circuit and then see if the pivots -.wi' loose. If the pivots are loo.se the arma- 
 ture will frecpiently stick and fail to release the shutter. 
 
 ( 202 1
 
 Post Telephone Systems. — Chapter 6. 5'i 
 
 Tf wlicii ;i riiiir coiiics in iikhc IIimii oiio (lrii|i lulls il niiiy lie i!iii> to ii iniss 
 ill llic lines just outside of tlif iioaid. or else on ihc li;rlitniiij: sliij) to uliidi 
 tlicse lines ;ire connected. Tins can he readily cleared liy ins]»ection. The 
 iroul)!*' may I»e due to tiie fact lliat tlie contacts on the magneto side of some 
 one of the riuf^in;; keys are not broken when tlie key is in a normal position. 
 
 WIu'ii il is discovered tliat a pair of conis <lo not jierform liieir j)roiier 
 f uuctioii they sliould be tested lor au opeu or for a " cut-out." 
 
 A frequent cause of trouble in the jacks is due to the fact tliat persons 
 will stick pens or pins in them and break off the points, short-circuit in? tlie 
 sju-inirs. Tiie only way to (li.scover this is by thorough inspection of the jacks. 
 To see whetlier the contacts in the riniiiiifr and listeniuf: keys break in the 
 liroper manner the part of the board containing; them should be placed between 
 tlie lijrlit and the eye of the inspector. By looking at tlie keys against the 
 light and opening and closing them it will be discovered whether the contacts 
 break properly or not. Trouble may frequently be removed from the cord 
 circuit l)y cleaning the ti]i and sleeve of the pbig with crocus doth. When 
 a switchboard is new and tirst placeil in service particles of metal are fre- 
 (pieutly found in the jacks, and the board can be cleaned by using a lian<l 
 bellows and blowing (mt all of the jacks thcu'oughly. 
 
 The accepted method of cleaning key contacts or mechanically testing for 
 opens is by putting a strip of hard-surfaced pafter between contacts when 
 keys are open, closing the keys, and withdrawing it. If the key does not 
 make a firm contact the paper will be easily withdrawn, and this trouble 
 can be eliminated by adjusting the key. If it does make a firm contact, 
 withdrawing the paper will clean off any dirt that may be on the contact. 
 
 Drops may be tested by using the short-circuiting key in the center of the 
 lower panel of the telephone switchboard in connection with the test jack. 
 Plug the defective drop into the test jack and press the button. If the drop 
 oiierates freely it should be considered satisfactory. 
 
 (26a
 
 ClIAPTKH 7. 
 SMALL-ARMS TARGET RANGE SIGNALING SYSTEMS. 
 
 Piiriifi^rMiiIi -(')- (if •• Small-Anns Firing Maminl. 191.'^." reads as follows: 
 
 ChiHfirii. — Tli(M-e are two classes of ranges : Class A ranges, which are more 
 or less limited in extent and which are etiuipped for known distance practice; 
 class B ranges, which are of extended area and diversified terrain, and 
 which are used for combat tiring. 
 
 The Signal Corps furnishes and installs material and apparatus for conunn- 
 nication for class A ranges referred to above. Inasmuch as the class B ranges 
 are often temporary in both arrangement and location, no fixed signaling 
 system for them can be devised. The Signal Corps has furnished apparatus 
 and material for establishing comnmnication for such ranges, the installation 
 being made by detachment of troops. 
 
 Class A ranges only are considered in the following: 
 
 The system of communications to be furnished target ranges depends on the 
 type of range, its size and importance, and upon local conditions, which vary 
 for each case. Among such local conditions may be mentioned the character of 
 the soil and the necessity for using the i-ange for other purposes, such as 
 drill, etc. 
 
 In general the systems for class A r;inges may be divided into three types, as 
 follows : 
 
 Ti/itc I. — This system is ajiplicable to all tyjies of ranges and provides for 
 telephonic communication only. The circuits of this system comprise a telephone 
 line from extreme end to end of the range with outlets at each firing line to 
 which a portable telephone may be connected by means of a flexible cord and 
 plug. The line is preferably laid underground in trench or conduit, lead- 
 covered or lead-covered and armored, rubber-insulation, single-pair cable being 
 used for this purpose. The telephone used is the standard camp telephone or 
 ob.solete field telei)hone fitted with cord and plug for attachment to outlet. 
 Where necessary, the telephone may be placed in a portable shelter box. 
 
 This type of system is used on small or unimportant ranges where the 
 expense of a more extensive system is not .iustitied, or for provisional work 
 where, on account of lack of funds or other causes, it is not possible to supply 
 a moi'e complete system. 
 
 Tjiix: ,i. — This .system of communicalioM is applicable to targets in echelon 
 only. It comprises the following connnunications: 
 
 {(i) A telephone for every group of 10 tiring points or less on line to telejihone 
 at butts. 
 
 (h) A push button at each tiring point connected to the buzzer at the corre- 
 sponding target. 
 
 (c) An ainunuiator at the butts of 2(T<)-yard. .S(X)-yard. ami .'^(KVyard ranges, 
 with a drop for each target of the respective ranges. Each drop may be actu- 
 ated by associated strap key in rear of respective target. 
 
 (d) A master switch at each annunciator, by which all target buzzers may be 
 operated simultaneously. 
 
 r2Gol I
 
 2 Signal Corps Manual No. 3. — Chapter 7. 
 
 Tliis system will he iuslalkMl lUKk'rjiniuiid in trcncli nr coiuluit, \isiii<,' iiainT 
 insulation cable for longitudinal runs, and rubber-insulation, lead-coveretl. and 
 armored cable (t.vpe 2."il) for the branches at the tirinu lines. 
 
 'I'lljic 'i. — This s.vstem is for installation at target ranges having only onegrouj> 
 of targets, the sevenil ranges being obtained by iilacing the tiring points behiml 
 each othiii". The equipment corresponds closely to the type 2, with such inoditi- 
 cations as ai*e necessary to adapt it to such arrangement. It provides the 
 following c(innnunication : 
 
 (o) A telephone for every group of 10 firing points or less on line to telephone 
 at butts. 
 
 (h) Push buttons at each tiring point connected to a buzzer at the corre- 
 sponding target. 
 
 {(■) An annunciator with a dro]) for each target, which (lro|) may be actuated 
 by a strap key at associated target. 
 
 (il) A master switch at the annunciator by which all target buzzers may be 
 oiierated sinndlaiu'ously. 
 
 I rc.'O' PcrnU-Ze <.or<J^ 
 
 COVER . 
 
 K.p Leatlicr-^ Id f;4"tli.ck 
 Dar»* Maroon colu-' 
 Close fil oil base 
 
 PLAN-ASSEMBLED-COVER REMOVED 
 
 CENTRAL -SECTION -ASSEMBLED 
 
 Grass pms Tf€\ 
 
 BASE OF PUSH BUTTON "4" -.\oC~-jt> 7^ip "^ rt"-; 
 
 Red F.ter LINING FOR 
 
 THIMBLE 
 Red Fiber .Oi5Th,i.k 
 
 m 
 
 £nd re<:/uccd inthfc^misi.^'^ ~ 
 
 '-frrp- 
 
 ■2" -■^^ rtir. 
 
 '^ U: H 
 
 ^i 
 
 -'--^i>-m % \<^ <? - -I - 
 
 '•^e^ 
 
 EfH:/ rf^(/ure<//n ff/trA/fcsa 
 
 — '-1^ 1 I- ;f - - A 
 
 Ned FiUr 0.).. Ilii( k 
 
 Fig. 7- 
 
 CONTACT SPRINGS 
 
 Uo 20( 035') Phosphor Brou/c 
 
 -S. A. TARGET RANGE PUSH BUTTON. 
 
 This system will be inslalled unih-rgronnd. using itaper insulation cable for 
 runs re(|uiring a large nnmln'r of conductors, and type 12r»l cable for distribution, 
 the same as for the type 2 system. 
 
 It will be noted that with the type 2 sysleni the 200-yard. .''.00-yard, and .500- 
 ,vard ranges are supplied with aniiuncialor, maslei' switch, and strai) ke.vs in 
 iiddilion (o llic oilier apparatus, .hkI thai I he C.oo-yard. SOO-yard. and 1.000-yard 
 I'angcs arc iiul supplied with that .-ipparat us, although a buzzer is inslalled in 
 rear of ea<-h target, making the Latter a buzzer system while the former is a 
 buzzer amnincialor .system. 
 
 (260)
 
 Small-Arms Target Range Signaling Systems. — Chapter 7. 3 
 
 The reason for this is that the annunciator, master switch, and strap key is 
 apparatus used in connection with raising; and h>\verinf; tlie targets promptly 
 and simultaneously, an operation pertaining to rapid-tire practice. Hapid-tire 
 practice is lield only on ranges up to and including ."j(M) yards. 
 
 The source of i)o\ver for operating the huzzer system and also the liuzzcr 
 amniMciator system is 20 cells of No. reserve type dry cells of hattery (fcir 
 di'scription of cell see diap. 1) installed in distrihuting box upon' two shelves 
 provided f«ir thai purpnse. The distrihiiiing hox is descrilied hiler in this 
 chapter. 
 
 Jtt K H Bmii 
 
 , Pmis plate 4''i^£, 
 
 COf^kxTtSprinq '203t^^i^ 
 
 This plug some as mOC 
 ^ Cos Marine Ouflet Mfrs 
 Cat fig ZZ323 
 
 iStandard if' P'P* tfireod 
 
 \/4- pr in 
 
 Fig. 7-2.— S. A. TARGET RANGE OUTLET BOX, ROUND PATTERN. 
 
 Each group of targets on the larger ranges is usually tniuipped with a small 
 structure in rear and in proxinuty to parapet wall. This structure is used f<»r 
 storing targets and supplies and may he used fur range olhcer's station during 
 firing. At ranges where buzzer annunciator systems are installed the annun- 
 ciator distributing box and master switch should he locatinl in this structure if 
 practicable. In some instances the Signal Corps has constructetl a small frame 
 booth in the form of a lean-to again.^t parapet wall for housing this api)aratus. 
 The booth was equipped with a slide window on eitlier side in order that range 
 
 46581°— 17- 
 
 -IS 
 
 (267)
 
 4 Signal Corps Manual No. 3.— Chapter 7. 
 
 officer might observe the actions of men at targets. It was also equippeil with a 
 tight roof and door with substantial lock in order that when range was not in 
 use contents of booth might be made secure. 
 
 PLU« CONTACTS. 
 
 Fig. 7-3.— S. A. TARGET RANGE OUTLET BOX, 1915 MODEL. 
 
 The target range outlet boxes for the push-button attaclnueuts should be 
 located approximately 10 feet in rear of each firing point, as scorers are required 
 to be seated close to and in rear of the firing-point stakes. 
 
 The push-button attachments should be removed and stored in a dry room 
 upon completion of each day's practice during inclement weather and wlien 
 target practice is suspended for a period of days. 
 
 1 I pair lead centred cobir 
 
 't 1.. 
 
 ->J 
 
 Ityrf/p/i t/7tle 
 
 \E\_ ^^_ 
 
 CuUrl «o-«J 
 
 =gl 
 
 ysr. 
 
 ^ 
 
 Pig. 7_4._S. A. TARGET RANGE, TYPE NO. 1 SYSTEMS. 
 
 (268)
 
 Small-Arms Target Range Signaling Systems. — Chapter 7. 5 
 
 The pusli-hintoii ;in;ichun'iil cniisisls nf ii i\\ n-(<iii(lii<tiii- llcxiliU' ciifd. Mpproxi- 
 niately tit>t in len^rtli. eiiuipped iit one cml wiili a si>eri:illy iU'si;:iie<l piisli 
 l)iitt(>n that can he (■(•nifortahly liehl in the liaml. At other cml tlie conl is 
 i'<liiippe(l with a suitahle piii;: adapted for altaciuucnt to peniiaiieiitly installed 
 
 FRONT OF POST AND BOX 
 
 Fig. 7-5.— S. A. TARGET RANGE. TYPE NO. 1 SYSTEM, OUTLET BOX. 
 
 target range outlet huxes. The push hutton referred to is shown in tigiuv 7-1, 
 and the round-pattern target range outlet hox with plug is shown in figure 7-2. 
 The.se boxes have been more or less unsatisfactory, due principally to the fact 
 that the screw cap covers are often not replaced when plug of push-button cord 
 is withdrawn, tliereby allowing moisture to enter the box. 
 
 Figure 7-3 shows an outlet box designed by the Signal Corps which is now 
 being given a service test. AN'itli this i)ox there is no screw cover to be remove*] 
 or replacjed in connection with the operation <tf inserting or withdrawing the 
 plug. When plug is inserted in socket on ontside of box, a thin metal iliaphragm 
 forming side of box is depressed. Two insulated contact pieces through dia- 
 phragm, which make contact with parts of plug to which ctmductors of cord 
 are attached, are made to connect with suitable terminals of cable on inside of 
 box by depression of diaphragm. It is therefore only -necessary to remove plug 
 when use of a particular outlet is c<nnpleted. Removal of plug allows dia- 
 phragm to attain normal position, thereby breaking contact between insulated 
 pieces through diaphragm and terminals of cable on inside of box. It «-an 
 readily be seen that siuface leakage of battery current, due to moisture on out- 
 side of box. is eliminated when plug is withdrawn. 
 
 For illustrating the various types of ranges and for showing the equipment 
 fin-nished and the methods of its installation, type ranges are shown in the 
 following figures. In future it will probably be found that in n«i case d<H>s 
 the range exactly conform to any one of the types shown. It may be necessary, 
 therefore, to modify the type scheme to make it applicable to any particular 
 case. 
 
 1269)
 
 6 
 
 Signal Corps Manual No. 3. — Chapter 7. 
 
 Fijiuro 7-4 shows the typi' 1 sysleni as installed on a ran,ii'e eciuiitped with 
 12 targets and as installed on a range equipped with 24 targets. Figure 7-.") 
 shows the type of outlet box and manner of coiuiecting it installed at eaeh 
 liring line, and tigure 7-G shows the construction of a portable box for pro- 
 tecting telephones used. In jireparing lists of material for installation of a 
 type 1 system, either the length of cords for ronnecting \]\o portable tele- 
 phones or width of range and luunber of targets nuisi be staled. 
 
 Fig. 7-6.— S. A. TARGET RANGE. TYPE NO. 1 SYSTEM, TELEPHONE BOX. 
 
 I'Mgure 7-7 shows a typo 2 system using one diminishing si7,(> caljle laid 
 iliagonally across the range with tajts to tlie vai'ious butts, while figure 7-8 
 shows separate cables used for each. Foi- eclielon ranges eiUier of these 
 methods or a combination of the two may l)e used, deiuMiding ui»on local con- 
 ditions: however, whenever i)i'acticable, the method shown liy tigure 7-S i.s 
 |iref('i'i-c(|. '{'he scale size of these ilhistrations is such that it is imprai'licable 
 (o show all ai»paratus. 
 
 Figure 7-9 siiows a ly|>e :> system, ^^■ith this i)articular system the 2(M)-yard 
 firing points were not ('([nipped with outlets but i)rovision for such (Mpiiitnunit 
 was made, (he necessary maidatles on line of main cabl(> having been i)rovided. 
 
 Strap l<c.\s, annunciator, and master switch are ))rovided for this type of 
 range in or(lcr tlint standard connnuiucat ion for ra)»id-tire jiractice .at (he 
 2(K)-yard. .'{OP-yanl. and .">(»( )-.\ar(l firing ])oints will be available. 
 
 Figure 7-1P shows the method employed in iiistiiHing the round ii;itterii 
 ontlet boxes. Sewer Hush jtipes uilli cover are used to house tlie outlet box 
 where is terminated the tyi>e 2."(1 c.-dile (1 i)aii- le;id covered and armored). 
 .\ wrought-iron support for oulli'l box is fastened by means of machine screws 
 1o l)e]l of sewer (lusii pi])e. Tlie ty)ie 2.">1 cable enters the outlet box through 
 a short length of I hree-fourlh inch conduit threaded tlinaigh snpiiorl sind into 
 base of outlet box. The cable is sealed by tilling the conduit, witinn which is 
 terminal(^d the sheaths of cable, with ozite or other approved moisture repellent 
 
 (J70)
 
 Small-Arms Target Range Signaling Systems. — Chapter 7. 
 
 T 
 
 rr^ M^ iSXT- \ 3! 
 
 fj^^m^f 
 
 S. A. 
 
 TARGET RANGE. TYPE NO. 2 SYSTEM. USING DIMINISHING CABLE.
 
 Signal Corps Manual No. 3.— Chapter 7. 
 
 (272)
 
 Small-Arms Target Range Signaling Systems. — Chapter 7 [) 
 
 TAROLT BUTT3 
 
 200 YARD LINC 
 
 o o@o o_ o 
 
 g 
 
 II f:r'rii points lOOl. 
 
 fQprcab^c ' ^1 prorma cable 
 
 3 •? R 
 
 tfOO YARD LINE 
 13 Q g o@0 Q 9 o o o@o 
 
 oosnts aOQYAROUNE. I2 hrir. 
 
 O O O 0©0 O O OrS)© O O O 
 
 5fj!ght J njy 5pl<C£. 
 
 ^ ^ 
 
 o o o®o o o 
 
 o otSio o o. 
 
 >®o o o 
 
 O O O^O o 
 
 LEGZNC 
 
 K^anholc Q 
 
 Distribubng box ■ 
 Spea'o/ 7^y Rr^Ju «j 5tax # 
 
 TeJcphorc % 
 
 Buzzer m 
 
 Finnj point o 
 
 o o o o@o o 
 
 Fig. 7-9.— S. A. TARGET RANGE, TYPE NO. 3 SYSTEM. 
 (273)
 
 10 
 
 Signal Corps Manual No. 3. — Chapter 7. 
 
 Scale-— 2 in=l in. 
 
 PLAN WITH COVER REMOVEJD 
 
 \ ^aV 
 
 /8 th'ds pr in. X I . i-L-i. 
 Tap ^'deep C\J «*? 
 
 Tap standard size 
 
 for -^' pipe -t4 f^rtls. pr i. 
 
 
 
 — ■ \com1rfithin0 
 — ^radiuidt^" 
 
 I 
 
 FiM corners. 
 
 ^nMilsidtstont 
 \:sy mthin 4'ptpc 
 
 SUPPORT FOR OUTLET BOX 
 
 One for eacti box — Wrot. iron 
 
 ■ y /4 t1l'ds.pr 
 
 Fig. 7-10.- 
 
 PIPE 
 
 Standard -^ inch 
 Loricated conduit 
 
 A. TARGET RANGE, TYPES 2 AND 3 SYSTEMS, OUTLET BOX, INSTALLA- 
 TION OF. 
 
 (274)
 
 Small-Arms Target Range Signaling Systems. — Chapter 7. 
 
 11 
 
 compound. Installation of 1915 model outlet box is similar, the box being 
 provided with supporting lugs. It will be noted that the sewer flush pipes are 
 equipped with a substantial removable cover. 
 
 Military drills by. various arms of the service are sometimes held on small- 
 arms ranges and with outlets installed as shown, little or no inconvenience is 
 occasioned tlie troops. When tlie soil is soft and the wheel of an artillery field- 
 piece comes in contact with one of these flush pipes it may be deflected fi-om 
 the vertical position, but no injury results as sower flush pipe, outlet box, and 
 sealing chamber are moved as a unit, the type 251 cable being flexible. The 
 pipes are easily returned to correct position after such an (x-currence. 
 
 f "■""■"r"\^^^^*v-^^'^"'^' i^ ^ 
 
 Fig. 7-11.— S. A. TARGET RANGE, TYPES 2 AND 3 SYSTEMS, MASTER SWITCH. 
 
 Figure 7-11 shows the construction of a master switch for a range having 
 IG targets. These switches have been furnished for ranges having 24 targets, 
 and while they can l)e made. for a greater capacity on the very large ranges, 
 it is believed advisable to install two switches, arranged to be operated simul- 
 taneously, if desired. 
 
 Figure 7-12 shows construction of manliole usually used in connection with 
 buzzer annunciator system. One of the.se manholes is constructed at each 
 flring line on line of each main cable witli the type 3 system. With the type 
 2 system location and number is dependent upon local conditions. 
 
 (275)
 
 12 
 
 Signal Corps Manual No. 3. — Chapter 7. 
 
 In these manholes are installed the target range junction box from which 
 tlistributiou (b.v means of type 251 cable) of circuits to outlet boxes is made. 
 It will be noted that cover of manhole is (3 inches below surface of earth so 
 that it is nnnotice<l when drills on range are held. If Artillery drills are held 
 on range it is advisable to provide extra support for boiler-plate cover. A 
 
 PLAN 
 
 Grouncf /me 
 
 
 jUJ 
 
 h- e'-H 
 
 SECTION 
 
 Fig. 7-12.— S. A. TARGET RANGE, TYPES 2 AND 3 SYSTEMS, MANHOLE. 
 
 siiiiill .".inch cycliciiiii .'icrKSs (•ciilcr of ni;iiilii>l('. su)»i)(irli'd Ity inanliolt' and 
 removable at will, is an excellent nu'tliod of providing this extra sui>p<)rt. 
 
 I'Mgwrt" 7- 1.'? sliiiws tiic cnMstrnctinn of tlic target range junction box, usually 
 installed iti nianlioics jusi desciihfd. Snilsdilc openings are provided in 
 
 C-'-Ci
 
 Small-Arms Target Range Signaling Systems. — Chapter 7. 
 
 bottom of box for oiitrjiiicc of :i lap froin maiii cable and a number of type 
 2r)1 cables. Tap from main calile enters tbroii;,'h circuhir opening and t.vpe 2~A 
 ral)le tbroujili (>loimateil oixMiin^'s on eitlier side of circular opening. Tbe box 
 will accoiiiiiutdale tliree Sijiiial Corps standard porcelain terminal strijis U) 
 wliicli conductors of cables are connected and wiiere proper cross connection 
 can be made. 
 
 Fig. 7-13.— S. A. TARGET RANGE, TYPES 2 AND 3 SYSTEMS, TARGET RANGE JUNC- 
 TION BOX. 
 
 Figure 7-14 sliows the construction and arrangement of equipment of the 
 distributing box for target ranges. This box is installed at the butts and 
 contains the 20 cells of dry battery which furnishes current for operating the 
 buzzers and aimunciator for each range. This box also contains three suitable 
 conunercial terminal strips to which are connected conductors of cal)le to 
 tiring points and rubber-covered wires to buzzers, strap keys, annunciator, 
 master switdi, and telephone at butts. Appropriate cross connections of the 
 Aarious lines are made at these terminal strips with No. lU rubber-covered 
 wire. 
 
 Figure 7-1.") shows the manner of installing the l)uzzer and strap Vcey. The 
 two pieces of apparatus are mounted on a hard maple backboard providetl 
 witli brass lugs through which pass the screws wliidi fasten it to parapet 
 wall. A sheet-metal cover is provided for protecting tlie buzzer and strap key 
 from the elements. This cover is held in position by fom- brass screws in 
 side edges of maple liackboard. Tliese screws are so inserted that the heads 
 are distant from backboard the thickness of metal cover. Slots are cut in 
 metal cover for engaging the screws, and the cover can be placed in position 
 
 (277)
 
 14 
 
 Signal Corps Manual No. 3. — Chapter 7. 
 
 or removed without removing tlie screws. The strap key can be operated with- 
 out removing metal cover, as there is an opening with slide cover for this 
 purpose. 
 
 While a number of strap keys and buzzers have been installed in this manner, 
 it is intended that in future a small metal box in the form of a condulet into 
 which the three-fourth inch conduit will be threaded will be supplied for the 
 purpose. 
 
 JNT WITH Ooon OPtN 
 
 Fig. 7-U.— S. A. TARGET RANGE, TYPES 2 AND 3 SYSTEMS, DISTRIBUTING BOX. 
 
 'riit' standiii'd iiictliod of wiriii;: he! wccii Hit' disi ribiilin::' Ixix :w\d llic bu/./,er.s 
 and strap keys is as follows: 
 
 lioricaled fotidnit from dislribuliim box to tlaiik bu/z/crs and straj) keys is 
 sccurt'ly rastciiod to ijarajicl w;ill. liic means of rasU'iiiiii;- being dependent on 
 iiiiiterlal of whieh parajiet wall is made. This line ol' conduit is below the 
 horizontal plane ()f position of the buzzers and strap koys. At each buzzer 
 
 (278)
 
 Small-Arms Target Range Signaling Systems. — Chapter 7. 
 
 15 
 
 and straji key tliis coiKluit line is j'l-ovidcd witli a piiic tee, the tap open'uv^ 
 heliiir lor three-fourth iiu-h eomluit. A piece of three-fourtii inch coiKhiit 
 endinj; on a liorizoiital level midway between buzzer and strap key is threaded 
 into tap openinj; of i)ii>e tee and the upper end of this conduit should be sealed 
 with Chatterton coniiuiund after wire mentioned later has been pulled in the 
 conduit. 
 
 A. TARGET RANGE, TYPES 2 AND 3 SYSTEMS, INSTALLATION OF STRAP 
 KEY AND BUZZER. 
 
 Rubber covered and braided wire, conductor 51 mils, i.s used for the con- 
 nections between distributinjr box and buzzer and .strap keys. This wire should 
 be pulled in the conduit simultaneously with tlie placing of conduit, as the wire 
 can not be pulled around the sharp corners of the pipe tees. 
 
 (279)
 
 16 
 
 Signal Corps Manual No. 3. — Chapter 7. 
 
 Figure 7-16 shows a diagi-am of through circuits. Referriug to this figure 
 it will be seen that one wire is common to center post of all strap keys. This 
 wire should not be tapped but should be looped to center binding post of 
 each strap key. the loop extending from pipe tee to strap key. 
 
 The size of conduit for the main rini is dependent upon the number of tar- 
 gets on the range and in some instances it may be advisable to use two or more 
 sizes, reducing the size as distant outlets are reached. If it is impracticable to 
 locate the distributing box near longitudinal center of parapet wall on a range 
 having 30 or more targets, cable should be installed between distributing box 
 
 Fig. 7-16. — S. A. TARGET RANGE, TYPES 2 AND 3 SYSTEMS, THROUGH CIRCUITS. 
 
 and one or more can terminals, appropriately located, and coinhilt lines extended 
 iioni can terminals to buzzers and strap keys. Figure 7-17 illustrates such an 
 arrangement. It is also applicable under some conditions where the miniber 
 of targets exceeds .50. regardless of whether or not distril)uting box be locatecl 
 near longitudinal center of parapet wall. 
 
 When approved in each individual case by the ('liief Signal Oflicer of the 
 Ariny, the sniall-arnis range may be connc^cted t«'lepli()nically with nearest post 
 tflei)hone system. 
 
 The wiring for annunciator and master switch is dependent upon coiulitions. 
 In some instances the master switch is mounted on the side of the distributing 
 box, In the event of which it is only necessary to make a neat form of sufficient 
 number of rubber-covered wires extending tiie wires from terminal strip 
 tlu'ough sifje of box t<» master switch. If the master switch or annunciator are 
 place<l distant from distributing box, tin! coiniecting wires should be iu iroa 
 conduit of suitable size. 
 
 (280)
 
 Small-Arms Target Range Signaling Systems. — Chapter 7. 
 
 17 
 
 As funds bocomo available for the construction of systems corresponding to 
 types 2 and 3 special plans will \h' drawn to meet the varying conditions of the 
 ranges that may bo selected. 
 
 Cal'te&sDa'r^buhn^ e<j* 
 
 Fig. 7-17.— S. A. TARGET RANGE, TYPES 2 AND 3 SYSTEMS, USE OF CAN TERMINAL. 
 
 For some of the large ritle ranges the Hignal Corps has supplied a portable, 
 direct-reading anemometer. The use of these instruments is confined to pre- 
 liminary drills for instruction in wind reading. They will not he allowed on 
 the range during the regular practice season or during competitions. (M. S. 
 O., 1201729.) 
 
 KKCOKD.S. 
 
 As previously stated in this manual, in no branch of the industrial field are 
 records of such great importance as those pertaining to electrical installations. 
 
 The Signal Corps requires that ui)on completion of a small-arms target range 
 signaling system a complete and accurate record be prepared by the person in 
 responsible cliarge of installation of the system. 
 
 This record consists of standard Signal Corps forms appropriately accom- 
 plished and drawings illustrating connections, cross connections, routing of 
 cables, and location of manholes and location of apparatus. All prints of 
 tracings and page 8 of Signal Corps Form No. 211 are submitted in triplicate if 
 range is for the United States Army and in quadruplicate if for the militia. 
 One complete copy of the record is furnished for oflice of each of the following 
 oflicials : 
 
 Chief Signal Ollicer of the Army. 
 
 Department Signal Otlicer of the department in wliich the range is located. 
 
 Commanding Officer of post to which the range is attached. 
 
 In addition at least one copy of di awing shown under subheading "a." apiiear- 
 ing later in this chapter, shall be transmitted to the local post (piartermaster 
 that he may be familiar with location of Signal Corps cable and conduit system. 
 
 If the range be for an organization of the militia, the latter copy and an 
 additional one should be forwarded to the Chief Signal Officer of the Army for 
 transmittal to the Chief, Division of Militia Affairs, General Staff, one copy 
 being for the files of his office and one for him to transmit to Adjutant Gen- 
 eral of the State militia, who will decide its custody. 
 
 The drawings should be made by means of waterproof ink on tracing cloth. 
 When installation of a system is made by the Signal Corps, United States Army, 
 and it is impracticable to make these drawings where installation of system is 
 made, the data should be forwarded by person in responsible charge of the 
 work to the Department Signal (Officer of the department in which the range 
 is located. The Department Signal Oflicer will have the tracings made, if facili- 
 ties are available in his office, using the data furnished as a guide. If im- 
 
 (281)
 
 18 Signal Corps Manual No. 3. — Chapter 7. 
 
 priK-ticable to make the drawings in tlie office of the Department Signal Officer, 
 the data should be forwarded to the Chief Signal Officer of the Army with re- 
 quest that the drawings be made. 
 
 The upkeep of these records is important and all authorized changes should 
 be recorded. It is the duty of signal officers to see that all moditications of the 
 original system are reported in order that the tracings may be revised and the 
 various offices furnished a print of the revised tracing. If the system installed 
 be for the United States Army, and there are facilities for changing the draw- 
 ings (tracings) and for making prints in the office of the Department Signal 
 Officer, the tracings will be tiled in that office, otherwise they will be tiled in the 
 office of the Chief Signal Officer of the Army. If the system installed be for 
 the militia, the custody of the tracings should be decided by the Chief, Division 
 of ^lilitia Affiairs, in each individual case. 
 
 Component parts of the recortl required are as follows : 
 
 ((/) One or more drawings, map, to scale, sliowing routing, type. Signal 
 Corps number of reel from which taki>n. and splices of all cables and routing 
 of aerial lines if there be any, location of manholes, and all apparatus installed. 
 If conduit for cables is used, the kind and size should be indicated. The dis- 
 tance between center of manholes and each of the two outlet boxes on either 
 side should be accurately shown as the surface indication of these underground 
 manholes is ofttimes obliterated. 
 
 (b) Drawing, diagram, not necessarily to scale, showing ail connections and 
 cross connections. This should include all connections and cross connections in 
 distributing boxes, all connections and cross connections in junction boxes, and 
 an outline of the circuit. A statement in the form of a note relative to average 
 insulation measurement of conductors of cable should appear on this drawing. 
 If cables contaiu any defective conductors, they should be indicated as such. 
 This drawing may l)e combined with drawing described under (a) if crowding 
 does not result. 
 
 SIGNAL COKl'S FORMS. 
 
 (r) Signal Corps Form No. 211 (report of inspection of Signal Corps equip- 
 ment). The lower half of page 8 of this form pertains to rille-range ecpiip- 
 ment and should be accomplished for each copy of the record by pers(Mi in re- 
 sponsible charge of an installation. 
 
 {(l) Signal Corps Form No. 282 (cost data of target-range system). This 
 form should be accomplished in duplicate (regardless of whether the system be 
 for United States Army or militia) by person in responsible charge of installa- 
 lion of the system. One copy is for the files of the Chief Signal Officer of the 
 Army and one for the files of the Department Signal Officer of department in 
 which range is located. 
 
 On large ranges, when sullicient funds are available, the longitudinal cables 
 slu)uld either Ik; armored or plac(>d in conduit, the former being preferable. A 
 number of systems using plain lead-covered cable trenched have been put out of 
 fonnriission by gophers gnawing through lead sheath. The same lias hai>j)ened 
 with plain lead-covered cahlc in coiiduit wlicro conduits were not sealetl at 
 manholes. Where plain lead-covered cable is used, every i>r<><-aution should \w 
 employed to prevent rodents entering the conduit system, for while this trouble 
 ajiparently is not exjM'rienced in cities and at most Army posts it has actually 
 occurre(l in the Philiintine Islands and at .some places in continental United 
 Stales. The liiteral cables from target-range junction boxes to push-button 
 outlets should invariably be type 2.'')1 (one i)air lead-covered and armored), 
 and trenched. 
 
 (281' J
 
 Chapter 8. 
 technical equipment issued by the signal corps. 
 
 This (liapttT is devoted t(» :iii eimineratioii of latest technical equiitiiiciit 
 issued, with brief description of various items. It is prepared with a view of 
 assisting in the preparation of re(iuisitions. 
 
 For description of items representing apparatus for fire-conti'ol systems at 
 seacoast defenses the reader is referred to Signal Corps Manual No. 8, revised 
 edition. 
 
 Information relative to the cost of material listed may be ol)tained from 
 the current Signal Corps price list issued annually at the beginning of the 
 fiscal year. 
 
 The technical equipment issued inclmles the following : 
 Alcohol : 
 
 Denatured. 
 
 Wood. 
 Anchor, expansion, bolt, shield | by 2 inches, screw f by 3 inches (without lag 
 
 screws). 
 Anchors, expansion, screw : 
 
 1-inch, without screws, for Xos. 9, 10, and 11 wood screws. 
 
 If-inch. without screws, for Nos. 9, 10, and 11 wood screws. 
 
 2-inch, without screws, for Nos. 9, 10, and 11 wood scx*ews. 
 Anemometers, i)ortab!e. with tripod and cups. 
 Anemometer stop watch. 
 Annunciators, target range : ' 
 
 10-signal. 
 
 20-signal. 
 
 25-signal. 
 Ardois lights, sets, complete : 
 
 Globes, tolophoto, for Ardois. Specify whether red or white and name of 
 manufacturer of set. 
 Arresters, Mason, fused : 
 
 Coils, choke, with carl)on blocks and mica insulators, in pairs. 
 Asbestos, sheet (thickness to suit requirements). 
 Axes : 
 
 Helves for. 
 Axes, hand : 
 
 Handles for. 
 r.ags, tool, .service. (See i>. (IS, this ch.-ipter.) 
 Bars, digging and tamping. 
 Barometers : 
 
 Aneroid. 
 
 Mercurial. 
 
 Box, wooden, for. 
 46581°— 17 19 
 
 (283)
 
 2 Signal Corps Manual No. 3. — Chapter 8, 
 
 Batteries : 
 Dry- 
 Miniature. 
 
 No. 4-0, Reserve type. 
 No. 6, Reserve type. 
 Tunjisten, type A (2-cell units). 
 Edison primary battery, type V — 
 Complete. 
 
 Renewals for, complete. 
 Jars for. 
 Covers for. 
 Fuller- 
 Complete. 
 Jars for. 
 Porous cups for. 
 Covers for. 
 Carbons for. 
 Zincs for. 
 Chromac for. 
 Mercury for. 
 
 Gaskets, rubber, for cover of. 
 Gravity, 5 by 7 inches, main line — 
 Bluestone. 
 Coppers for. 
 Jars for. 
 Zincs for. 
 Storage — 
 
 Type A, 1.5-cell (10-ampere rate). 
 Type K, l.^-cell (15-anipere rate). 
 Type ET, coupled (4i-anipere rate). 
 6-volt, 80 auii)ere hours (for audion detectors). 
 Maintenance parts — 
 
 Electrolyte, 1.200 S. G. (120-11). carboy). 
 Electrolyte, 1.400 S. G. (120-lb. carboy). 
 
 Carboys for (not included in the above). 
 Elements, negative (for 10-ampere rate). 
 Elements, positive (for 10-anipere rate). 
 Hydrometer. 
 
 Insulator, glass, petticoat, for tray. 
 Jars, glass. 
 
 Jars, rubber, with covers. 
 Plates, positive or negative. 
 Separators. 
 Syringe, hard-nilihiT. 
 Thermometer, lloatiiig tyi)e. 
 Trays, sand (for 10-ampere rate). 
 
 XoiE. — In requesting iiny i)arts for storage batteries, the 
 manufacturer, type, and any other relative data nnist l)e sup- 
 plitMJ, in order that the i)roper parts may be supplied. 
 P.eeswax. 
 
 I'.ellows, motor {generator. 
 P.olls, exten.sion, loud ringing, with condenser. (Set; p. 22, this chapter.) 
 
 (284)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 
 
 Belts, liiu'maM'.s tool, with rings and sulety sti'aps. 
 Bicycles, chain. 
 Blanks, telegraph : 
 Message i*eceived. 
 Message sent. 
 Blotters, small. 
 Blocks : 
 
 Connecting, W. E. — 
 
 6A (7-pair). 
 
 7A (1-pair). 
 
 6B (11-pair). 
 
 6C (IG-pair). 
 
 GD (21-pair). 
 Ternjinal, telephone. 
 Boards, letter clip. 
 Bolts : 
 
 Expansion (see Anchors). 
 
 Carriage (for securing brace to cross-arm), § by 4 inches. 
 
 Lag (for securing brace to pole). (See Screws, lag.) 
 
 Cross-arm (for securing cross-arm to pole) (give length desired) — 
 
 f by 10 inches. 
 
 f by 12 inches. 
 
 f by 14 inches. 
 
 f by 16 inches. 
 
 f by 18 inches. 
 
 I by 20 inches. 
 Machine (give length and size) — 
 
 f by 6 inches. 
 
 s by 8 inches. 
 
 § by 10 inches. 
 
 i by 12 inches. 
 Stove (give length and size) — 
 
 s by 2 inches. 
 
 i by 4 inches. 
 
 i by 6 inches. 
 
 i by 8 inches. 
 Toggle (give length and size) — 
 
 i by 3 inches. 
 
 i by 6 inches. 
 Books, field message (Form 217.\). 
 Boxes (also see p. 20, this chapter) : 
 Connecting. 
 Distributing. 
 Junction, iron. 
 Outlet, circular type — 
 
 Bases, porcelain, for. 
 
 Gaskets, for. 
 
 Plugs for, with 8-foot cord, with lignum-vit^e tips. 
 
 Supports for. 
 
 Without plugs. 
 Outlet, marine type, complete with plugs. 
 Cable pole. Sterling, complete, with tubular fuses and carbon arresters. 
 
 (285)
 
 4 Signal Corps Mzinual No. 3. — Chapter 8, 
 
 Boxes — Cou t iuued . 
 Cut-out, 2-.switch. 
 Cut-out, 3-s\vitch. 
 Junction, iron, 3-way. 
 Outlet, searclilight. 
 Switch, base line. 
 
 Terminal, fire-control type (see p. 20, this chapter) — 
 2-strip, metal, 1915 model. 
 4-strip, metal, 1915 model. 
 8-strip, metal, 1915 model. 
 Transfer, switch — 
 2-sAvitch type. 
 4-switch type. 
 Time-interval bell. 
 Terminal, submarine — 
 Type No. 1. 
 Type No. 2. 
 Type No. 3. 
 Type No. 4. 
 Braces, cross-arm (IJ inches wide, -^ inch thick; sive lenjrth desired) : 
 20-inch. 
 22-inch. 
 24-inch. 
 26-inch. 
 28-inch. 
 Brackets : 
 
 Iron, for lance poles. 
 Oak, for glass insidators. 
 Brushes, paint, all sizes (give size and whether round or flat). 
 Buckets, water, canvas. 
 Buttons : 
 Push— 
 
 Leather cover for. 
 Buzzers, Faraday type, 150-ohm: 
 
 Covers for. 
 Buzzer, service, model 1914 (the 1914 service buzzer when furrn'slied complete 
 consists of 1 buzzer with dry balleries. tools, conncH'ting cord. i)lug, tyiH' A 
 connector fWilliains's test clamp), transmitter and I'eceiver, and type I> 
 ground rod). 
 I'nzzer. service^, model 1914 — iiiaiiihMiancc iiarls; 
 Flatteries, dry. tungsten. tyi)e A. 
 
 r.lock, connecting, for condensei's, complete, assembled. 
 Buttons — 
 
 Hard nihlier. for key. 
 Transmitter switch. 
 Caps — 
 
 Receiver. 
 Transmitter. 
 Coil, complete, witji back irons and bracket, witlioiit contact screw, mount- 
 ings, and vibrator. 
 Condensers. 
 Connector, type A (see p. 89, tins cliai>ter). 
 
 (28«)
 
 Technical Equipment Issued by the Signal Corps — Chapter 8. T) 
 
 r.uzzcr. scrvico, model 1014 -< 'mil iiiuod. 
 Cords — 
 
 Main, witli it'niiiuals. 
 
 'I'l'jinsniillci- and rcccivcf (atso for rooeivor of Field Artillery tele- 
 phone ) . 
 Cups, fiber, for plugs (also for plugs of Field Arlillei-\ ti leidione). 
 iJoors. battery, eomplete. with liinges, contacts, and covers. 
 Headbands, receiver (also for I'McId Artillery telephone). 
 Key, lever, complete. 
 
 Supports and screws. 
 
 Screws, fulcrum. 
 
 Screws, platinun- contact, for key handle. 
 
 Screws, platinum contact, undei- key. auxiliary. 
 
 Screws, platinum contact, under key, main. 
 Latches, washers, and screws. 
 Nuts, hexagon, for base wiring, 4-36. 
 Plugs, complete. 
 
 Jacks, plug seat. 
 
 Springs, for .jack. 
 
 liods, steel, for plug. 
 Posts, binding. 
 Receiver, with headband and cords. 
 
 Diaphragm for. 
 
 Cap for. 
 Screws, adjusting, with platinum contact, for vibrator. 
 
 Adjusting. 
 
 Clamp, hlister head, ij-inch, 5-40. for vibrator. 
 Spring and support. 
 
 Battery contact, right. 
 
 Battery contact, left. 
 Spring and piece for condenser. 
 Spring, for key. 
 Straps, carrying, complete. 
 Switches, lever, complete, for receiver. 
 Transmitter, with cords, complete. 
 
 Diaphragm, for transmitter. 
 Vibrator, complete (11 pieces). 
 
 Washers, micanite (or mica) for back of transmitter case. 
 Wrt'nches. socket, complete, with screw driver. 
 Cabinets : 
 
 File, storekeeper's. 
 Supply. 
 Terminal. 
 Cables, all types (for complete list see p. 2:i, this chapter: for description and 
 
 detailed characteristics see chapter 4). 
 Cables, submarine, gear and supplies (see p. 30, this chapter). 
 Candles, for folding candle lantern. 
 Cans : 
 
 Gasoline, 1-gallon size. 
 Oil, steel, pint size. 
 Oil, 10-inch, bent spout, copper. 
 Cards, code, semaphore. 
 
 (287)
 
 6 Signal Corps Manual No. 3. — Chapter 8. 
 
 Carriers, wire, for buzzer wire {.see p. 87, this chapter). 
 
 Covers for. 
 Cartridges (for Very pistols). 
 
 Very — 
 Green. 
 White. 
 Red. 
 
 Smoke (for day use). 
 Carts, signal. (See p. 23, this chapter.) 
 Carts, Avire. (See p. 33, this chapter.) 
 Case: 
 
 Battery (for holding 6 type A tungsten dry batteries). 
 
 Map. 
 Case, electrical instrument, complete. (See p. 54, this chapter.) 
 Cases, reagent, for testing storage batteries. 
 Cells, dry. (See chapter 1.) 
 Cement, rubber, 2-pint cans. 
 Charges, carbide, for field acetylene lantern. 
 Chests, tool : 
 
 Aeroplane. (See p. 58, this chapter.) 
 
 Construction. (See p. 62, this chapter.) 
 
 Cable splicer's. (See p. 64, this chapter.) 
 
 Electrical engineer's. (See p. 60, this cliapter.) 
 
 Mechanic's No. 1. (See p. 55, this chapter.) 
 
 Mechanic's No. 2. (See p, 5.5, this cliapter.) 
 
 Pipe fitter's. (See p. 65, this chapter.) 
 
 Post. (See p. 66, this chapter.) 
 Chisels, cold, 6-iuch. 
 
 Circuit breaker (circuit breakers are furnished as a part of the various power 
 switchboards, and in requesting repair parts state whether single or double 
 pole, capacity, overload or underload, or reverse current, manufacturer's 
 name, type and code number, and. If practicable, catalogue number) : 
 
 Double pole, overload and reversite breaker, calibrated 35-70 amperes. 
 
 Tyi)e E. L., single pole, plain overload, rated 20 amperes. 
 Clamp, splicing. 
 Clamps : 
 
 Cable, large. 
 
 Cable, small. 
 
 Ground. 
 
 (iuy, 2-l)olt. 
 
 Guy, 3-bolt. > 
 (!leats : 
 
 Porcelain, 1-wire (for inside wiring for t('le])hones). 
 
 I'orcelain, 2-wire. 
 
 Porcelain, 3- wire. 
 
 Wood, cross-arm. 
 Climbers, willi straps, pairs. 
 Clii)s: 
 
 'i'cstliig. 
 
 <'rosl)y, 3-iii'h. 
 Clocks, alarm. 
 
 (288)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 7 
 
 Cloth : 
 
 Crocus, sheets. 
 
 Emery, No. 00 to No. 1*, sheets — 
 No. 4. 
 No. 14. 
 Coal oil. 
 Coil, repeatinfr. 
 Coil, retardation. 
 
 Compound, Cliatterton's. (See p. 4;", this chapter.) 
 Compass, pocket. 
 
 Condensers (the type of condenser, manufacturer, and type of equipment for 
 which it is required should be stated) : 
 Western Electric No. 21 F, for common l)attery telephones. 
 2-microfarad. 
 8-microfarad. 
 Conduit (also see p. 43, this chapter) : 
 Bituminized fiber — 
 2-inch. 
 2^inch. 
 3-inch. 
 
 Compound for joints. 
 Flexible, Greenfield — 
 i-inch. 
 f-inch. 
 1-inch. 
 Loricated — 
 J-inch. 
 1-inch, 
 li-inch. 
 2-inch. 
 2i-inch. 
 Elbows for — 
 1-inch. 
 14-inch. 
 2-inch. 
 2i-inch. 
 Condulets. pipe, F. P., J-inch. 
 Connectors : 
 
 Type A, main cord of st-rvice buzzer (see p. 89. this chapter) — 
 Studs for. 19-point. 
 Terminal, for cord. 
 Cord : 
 
 Antenna, 42-.strand (for radio masts). 
 Sash— 
 
 A-lnch, No. 6 ((66 feet to pound). 
 1-inch, No. 12 (20 feet to pound), 
 i-inch, No. 5 (20 feet to pound). 
 Buzzer, main (for .«;ervice buzzers). 
 Tiamp — 
 
 No. 14, reenforced. 
 No. 16, reenforced. 
 No. 18, reenforced. 
 (P'or various kinds of electrical apparatus cords see p. 35, this chapter.) 
 
 (289)
 
 8 Signal Corps Manual No. 3. — Chapter 8, 
 
 Cotton, striiis, rolls, for cable splicing. 10-yard rolls. 
 ( 'ovei's : 
 
 <':iii\as. teU'iiliiine motor generator. 
 
 Ilandholc. 
 
 Iron, manhole, 44 by 30 by g int-li (140 pounds each). 
 
 For wire carriers. 
 Crank, reel cart. 
 Cross arms : 
 
 For iron poles, complete with bolts. 
 
 Wooden, 2 to 10 pin, bored for IJ-inch pins (state number of pins re- 
 quired) — 
 2-pin. 
 C-pin. 
 10-pin. 
 
 Braces, galvanized iron, 20 to 28 inch lengths, for (state length). 
 Braces, galvanized iron, 28-inch, for. 
 Cut-out, porcelain, wall (main or branch, in sizes to suit requirements; give 
 
 carrying capacity of fuse). 
 Disks, cipher. 
 Envelopes : 
 
 Message. 
 
 Penalty. 
 Equipment, lighting, for F. C. switchboard rooms. 
 Erasers, rubber. 
 Fault-finder, Leeds & Northrup. 
 Files, property return. 
 Flashlights, electric, complete. 
 
 Batteries for (tungsten, type A). 
 
 Bulbs (lamps) for (Mazda "A"). 
 Frame, name plate. No. 2, with celluloid cover. 
 Fuses (also see p. 42, this chapter) : 
 
 For Mason arrester, 1 ampere ( type 9 ) . 
 
 Cook, type A7, 5 amperes. 
 
 Cook, type A12, 3 amperes. 
 
 Type 1. 5 amperes. 
 
 Type 1. 10 amperes. 
 
 Type 2. .^ amperes. 
 
 Type 2. 10 amperes. 
 
 Type 3, .'> amperes. 
 
 Type 3, 10 amperes. 
 
 Type 3. 1") amperes. 
 
 Type 3, 20 amperes. 
 
 Type 3, 2.^ amperes. 
 
 Type 3, 30 amperes. 
 
 Type 4. 31 amperes. 
 
 Type II. 1 aniixTc ( for Mason arrester). 
 
 For Sterling Xo. 247E i)rotectors, i") amperes. 
 
 \V. E., type 3r)r.. r* amperes. 
 
 W. E., type 7A, 3 amperes. 
 Gasoline. 
 
 (290)
 
 Technical Equipment Issued by tlie Signal Corps. — Chapter 8. 9 
 
 Glasses, field. 
 
 Type A, with case. 
 
 Case for. 
 Type B, \\ith case. 
 
 Case for. 
 Type C, with case. 
 
 f 'ase for. 
 Type D, with case. 
 
 Case for. 
 Type EE. 
 
 Case for. 
 Description of each of these field glasses will be found on pages 40 and 41, 
 this chapter. 
 Grips, Buffalo, No. 1, Willi ])nlleys. 
 Hammers, cari)enter's. 
 Hand-set switch, 1 liey. 
 Hand-set switch, 2 keys. 
 Handles, pay-out. 
 
 Hangers, cable, galvanized iron, 2-incli. with n hooks. 
 Hatchets. 
 
 Handles for. 
 Heliographs, complete, with two tripods. 
 Maintenance parts- 
 Cases — 
 
 Leather, carrying. 
 Wood, for mirror. 
 Frame and mirror, complete. 
 Heads, tripods, for mirror bar. 
 Keys with bars for screen. 
 Mirror, field. 
 Points, steel, for tripods. 
 Rods, sighting. 
 Screens, complete. 
 Screw drivers. 
 Screws — 
 
 Adjusting, with clamps, for mirror frame. 
 
 Center, for tripods. ' 
 
 Tangent, for mirror bars. 
 Shutter, complete. 
 Springs, mirror bar. 
 
 Tripods, each (2 furnished with heliograph). 
 Hoods, metal, for buzzer and strap key. 
 Hooks, message. 
 Houseline. 
 
 Ink (writing fluid), pints. 
 Insulatine. 
 
 Insulating conijjounds. (See p. 44, this chapter.) 
 Insulating materials. (See j). 44. this chapter.) 
 Insulators : 
 Chuup. 
 Pigtail, 
 
 (291^
 
 10 Signal Corps Manual No. 3. — Chapter 8. 
 
 Insulators — Continued. 
 Glass — 
 
 Double groove. 
 Double petticoat. 
 Pony. 
 
 Transposition. 
 Pony, porcelain, double groove. 
 Knobs, porcelain (give si2e) — 
 No. 4. 
 No. 5. 
 NO.-14. 
 Iron, strap. 
 Jack, wagon. 
 
 Jacks, cable reel (state lifting capacity desired) : 
 5-ton. 
 
 Axles for (give diameter and length). 
 Axles, 2 inches by 6 feet, for. 
 Keys : 
 
 Strap, with slate base. (See p. 43, this chapter.) 
 Telegraph, leg or legless, open or closed circuit. 
 Kits: 
 
 Flag- 
 Combination, standard (consisting of 1 case, canvas; 1 staff, 3-joint; 
 
 1 flag, red, white square; 1 flag, white, red square; 2 staffs, sema- 
 phore; 2 flags, semaphore, standard). 
 
 Combination, Artillery (same as " combination, standard," except that 
 
 2 flags, semaphore. Artillery, are substituted for the 2 flags, sema- 
 phore, standard). 
 
 Combination, Infantry (same as "combination, standard," except that 
 1 Infantry flag is substituted for the 2 red and white flags). 
 Maintenance parts — 
 Case, canvas. 
 'Staff, 3-joint complete — 
 Lower joint. 
 Middle joint. 
 Upper joint. 
 Staff, semaphore. 
 Flags — 
 
 Red, white square. 
 White, red squavre. 
 
 Semapliore (combinalion or Artillery). 
 Infantry (regular organization). 
 Infantry (militia). 
 Flag, 4-foot, complete. 
 Maintenance parts — 
 Case, canvas. 
 Staff, 3-j()iiit, complete, 
 liower joint. 
 Middle joint. 
 , TTppor joint. 
 
 Flags— 
 
 Ucd, white square. 
 White, red square. 
 
 (202)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 1 1 
 
 Kits— Continued. 
 
 Inspector's pocket, complete (lor full description see p. 69, tliis chapter). 
 
 ^Maintenance parts — 
 Cases, leatlier. 
 Files, 3-inch. 
 Knives, electrician's. 
 Pliers, 5-incli, side-cutting, nickeled. 
 Rules, 2-foot. 
 Scissors, electrician's. 
 Screw drivers. 
 Tweezers. 
 Knives : 
 
 Brush cutting. 
 Electrician's. 
 Lacquer, transparent, ^-pint tins. 
 Lamps, battery examining, 2()-volt, Edison base. 
 Lanterns : 
 
 Acetylene, field, complete, without tripods (tripods furnished with helio- 
 graphs are used). 
 Maintenance parts — 
 
 Base, complete, with key. 
 Burners for. 
 Bushings, water-tube. 
 Caps — 
 
 For inlet tube, with needle point. 
 For safety outlet, without holes. 
 Generator, with gooseneck. 
 Cases. 
 
 Charges, carbide. 
 Cleaners. 
 Cocks, gas. 
 
 Covers, complete, with front glass. 
 Diaphragms for carbon holder. 
 
 Gasket, rubber, for top and bottom, cartridge opening. 
 Generator, complete. 
 Glass, front, complete. 
 Hose, rubber. 
 Lead, white, tubes. 
 Lens (see Glass). 
 Mirrors, reflecting. 
 Needles, for cleaning burners. 
 Pliers, gas, 6-inch. 
 Screw driver. 
 Springs — 
 
 Key, new style. 
 Key, old style. 
 
 For holding carbide cartridge. 
 Stopper, rubber. 
 Straps, carrying. 
 Tips, lava. 
 Tripods, each (not furnished with :uetylene lantern; use one of 
 
 two with heliograph. 
 Tubes, outlet, with screw caj) and gas cock. 
 (293)
 
 12 Signal Corps Manual No. 3.— Chapter 8. 
 
 Lanterns — Continued. 
 Candle, folding. 
 Candles for. 
 Coal oil. 
 
 Globes for. 
 Wicks for. 
 Lead, red. 
 
 Leather, strips, for pot heads, 2i by 6 inches, sole. 
 Line construction tools. (See p. 01, this clinpter.) 
 Line construction materials. (See p. 45, this cliapter.) 
 Loom, 'circular (give inside diameter) : 
 f-inch. 
 f-inch. 
 Lugs, for terminals (give size of hole for conductor). 
 Magneto, testing set, lineman's. 
 Map measurers, watch style. 
 Matches, wind, boxes. 
 Megaphones. (See p. 89, this chapter.) 
 Molding, type A. ( See p. 70, this chapter. ) 
 Molding, type B. (See p. 70, Ihis chapter.) 
 Mortars. 
 Motor generators : 
 
 i-kilowatt direct-current motor (for charging a 1.5-cell telephone storage 
 
 battery ) . 
 1-kilowatt direct-current motor (for charging a lo-cell telephone storage 
 
 battery ) . 
 Ringing, direct-current motor (for use in connection witli teleplione 
 switchboards). 
 
 Note, — These machines can lie furnished Avith either direct-current or 
 alternating-current motors. When requesting alternating-current 
 equipment give voltage, frequency, and number of phases. In re- 
 questing any parts give manufacturer's name, type, serial number, 
 size, and all other data usually shown on name plate of ihe machine 
 for which the parts are required. 
 Maintenance parts — 
 Bellows for. 
 
 Brushes, generator side (give accurate dimensions). 
 Brushes, motor side (give accurate dimensions). 
 Busliings, p(trcelain, for l)rusli liolders. 
 Motor, starting l)ox. (Repair parts may l>e had for any of the motor starters 
 furnished by the Signal Corps, In re(|uesting these parts give manufacturer's 
 name, type, size, and serial number; ai.so state fully Uie part desired in order 
 to obviate mistakes.) 
 Mountings, buzzer, target range. 
 IMountings, n'tardation coil. 
 Mucilage, bottles, quarts. 
 Muslin, bh'aclicd, yards. 
 Nail puller. 
 Nails (give size and, if wirc^ nails, stale \\h('nier conunon, finishing, or brad 
 
 nails are refpiired). 
 Oil, dynamo. 
 Oiling sets, complete. 
 Ozite, 
 
 (294)
 
 Technical Equipment Issued by the Signal Corps.— Chapter 8. 
 
 Pads, hand, leather. 
 Paint : 
 
 MoKul, prc'sorvative. (See p. 71, this cliupter.; 
 
 Keady-mixed oil colors. 
 Panel : 
 
 Telephone, power, style 1. 
 
 Telephone, power, style 3. 
 
 Station switch, without mountings. ^ 
 
 Paper : 
 
 Carbon, sheets. 
 
 Legal cap, reams. 
 
 Letter, typewriter, heavy, reams. 
 
 I>etter, typewriter, light, reams. 
 I'arafHn, pounds. 
 I'asters, splicing, 2-inch. 
 Paul ins, for wire carts. 
 Pencils : 
 
 Copying. 
 
 Lead. 
 Penholders. 
 Pens, gross. 
 
 Photography. (See p. 72, this (•liai)ter.) 
 Pick, 7-pound, with handle. 
 
 Handle for. 
 Pikes, wire. (See p. 89, this chapter.) 
 
 Hooks for. 
 
 Poles for. 
 Pins, cones. 
 
 Pins, insulator, for cross arms, 11-inch. 
 Pipes, sewer flush, with cast-iron covers. 
 Pistols, A'ery. 
 
 Cartridges for. red. green, or white (see Cartridges). 
 Pliers: 
 
 .5-lnch, side cutting. 
 
 8-inch, side cutting. 
 Plow. 
 
 Plugs, insulator, for ii-oii ]H)les, oalc, 2-iMch. 
 Poles, lance. (See p. 89, this cliai)ter.) 
 
 Insulators for (clamp or pigtail). 
 I'oles, telegraph : 
 
 Steel. 
 
 Wood (state luMgiit rtMiuired). 
 I'sychromctcr, sling. 
 Kadio equipment : 
 
 Table set, i kilowatt, without generator. 
 Component parts for — 
 
 Ammetei". 0—4 amperes. 
 
 Angles, set of 8. 
 
 Blocks, wooden, set. 
 
 Box, motor starting. 
 
 Bushings, hard rubber, set of 9. 
 
 Button, push. 
 
 Buzzer, test. 
 
 (295)
 
 ]4 Signal Corps Manual No. 3. — Chapter 8. 
 
 Radio equipment — Continued. 
 
 Table set, ^ kilowatt, without generator — Continued. 
 Component parts for — Continued. 
 
 Condenser. 
 
 Cover, canvas. 
 
 Crystals, for detector. 
 
 Gaps, spark. 
 
 Key, sending. 
 
 Padlock and hasp. 
 
 Receiver, telephone, double head. 
 
 Receiving set, complete. 
 
 Rods, high resistance. 
 
 Switcb, control. 
 
 Switch, lightning. 
 
 8witcli, snap. 
 
 Table. 
 
 Tran.sfornier, oscillating. 
 
 Transformer, power. 
 Motor generator, alternating-current nuitor. 
 Motor generator, direct-cun-ent motor. 
 
 Radio pack sets, model 1915, consist of the following units: 
 1 operating chest. 
 1 hand generator. 
 1 mast , type F. 
 1 pack frames, set. 
 1 tent. 
 Each unit contains component partts as follows: 
 Operating chests — 
 
 1 chest. 
 
 1 resonance transformer. 
 
 1 condenser. 
 
 1 o.scillation transformer. 
 
 1 sending key. 
 
 1 spark gap. 
 
 1 hot-wire ammeter. 
 
 1 switch. 
 
 1 receiving set. 
 
 1 connecting cord for generator (4-conductor, witli plugs). 
 
 1 connecting cord, with plug, for antenna. 
 
 1 double-head receiver. 
 
 1 test buzzer. 
 
 1 tool kit. 
 
 1 extra section for transformer sei'ondary. 
 
 1 extra set crystals. 
 
 1 canvas case for receiver. 
 
 1 connector, 4-wire (lower half), geiicralor. 
 
 2 connectors, 2-wire (lower half), nntcnua an<l counlerpoise. 
 1 flexible comiector for antenna inductance.* 
 
 1 <'onnector, 2-wire, small, for receiving set.' 
 
 2 spring hooks.' 
 4 legs for chest.* 
 
 1 Supplied wltli 1 1 •! lOI.''. cliost only. 
 
 (296)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. If) 
 
 Radio equipment — Continued. 
 
 Each unit contains component parts a.s follows — Continued. 
 Operating chests — Continued. 
 
 1 copy '• Kadiotelegraphy " (S. O. Cir. No. 1, 1914, revised). 
 Hand generator — 
 
 1 generator. 
 
 2 cranks. 
 1 stand. 
 
 1 speedometer (carried in operating cliest). 
 1 cap for speedometer opening. 
 1 canvas hood. 
 Mast, type F. Cl'yiM' I) mast has I top, 1 h(»tl(iiii, ."> intermediate and 
 3 extra sections.) — 
 1 top section. 
 1 bottom section. 
 
 8 intermediate sections. 
 
 4 intermediate sections, extra (3 for tent). 
 1 antenna. 
 
 1 counterpoise. 
 
 9 carriers, wire. 
 4 pins, antenna. 
 
 2 hammers. 
 
 1 set adapters for tent (4 pieces). 
 1 bag, antenna, and counterpoise. 
 1 bag, accessories. 
 Pack frames, set — 
 
 3 frames (1 set). Each frame is complete with cincha, 2 straps 
 with snap hooks, and 2 plate staples. 
 
 Tent— 
 
 1 tent. 
 14 pins. 
 
 2 gny ropes. 
 
 1 insulating device. 
 
 Complete radio pack sets are designated as Rndio pnclc sets, complete 
 
 (year and serial number). Incomplete pack sets will not be designated 
 
 as such. 
 
 Units which are complete are designated under T'nit headings given above. 
 
 Units which are incomplete are designated under Crfrnponent fxirt headings 
 
 given above. 
 The model, year, and serial number will always be shown in connection 
 with operating chests and hand generators. With masts the type will 
 be noted. 
 Rectitiers. (All data upon manufacturers name iilate umst be given in re- 
 questing any parts.) 
 liectifiers, mercury arc, G. E., complete with transformer. 
 Reels : 
 
 Pay-out (Barrow type, with straps) — 
 
 Straps, shoulder, for. 
 Take-up. 
 Hand, for buzzer wire — 
 
 Cranks for, complete with pinions. 
 
 (297)
 
 16 Signal Corps Manual No. 3.— Chapter 8. 
 
 Relays : 
 
 Pocket, luU-ohm. 
 Standard, 150-ohm. 
 Box-sounding, 150-ohm. 
 Retardation coil. 
 Ribltons. typewriter. 
 Rings : 
 
 Cable (see hangers). 
 
 Bridle, enameled (see p. 71, this chai)ter, for description)- 
 Sizes § to 3 inches — 
 f-inch. 
 li-inch. 
 Rockets : 
 
 Sequence. 
 Yellow-smoke. 
 Rods, ground (see p. 71, this chapter) : 
 Terminal, for cord, type C. 
 Type A, f-inch by 5 feet. 
 Type B, ^-inch by 6 feet. 
 Guy, f-inch by 7 feet. 
 Rope, manila (all standard sizes) : 
 
 Weights, approximate, per coil of 1,200 feet — 
 |-incli diameter, 24 pounds, 
 f-incli diameter, 31 pounds, 
 ^-inch diameter, 9.5 pounds, 
 f-inch diameter, 160 pounds. 
 f-inch diameter, 200 pounds. 
 |-inch diameter, 270 pounds. 
 1-inch diameter, 325 pounds, 
 li-inch diameter, 505 pounds, 
 l^-incli diameter, 725 pounds, 
 itulilier. pure (cable splicing). 
 Sandpaper, No. 00 to No. 4. 
 Saws, crosscut, carpenter's. 28-inch. 
 Screw anchors. (See p. 72, this chapter.) 
 Screw drivers : 
 
 S-iucil. 
 
 10-inch, 
 Screws : 
 
 Lag, g by 4 iiwiu^s (lor sivuriiig brace to pole). 
 
 Lag. -i l)y 4 iiicbcs (lor scon-lug brace to pole). 
 
 Machine, assorted slz(>s and kinds. 
 
 Wood, as.sorted sizes and kinds. 
 Seats, pole. 
 Sets, switch-key. 
 Shellac, orange. 
 Shells: 
 
 Red. 
 
 Smoke. 
 
 White. 
 Shovels : 
 
 L<>ng-lian<lleii. 
 
 Short-handled, mnnd jioint. 
 
 (298)
 
 Technical Equipment Issued by the Signal Corps. — Chaolcr 8. 1 7 
 
 Sliiolils. expansion. 
 Signals, tiring;: 
 
 BiittiTV coniiiiamlcr. 
 Mortar pit. 
 Sleeves : 
 
 Melntyro, ntpiuM". spiicin:.: (ixiw size of wire) — 
 
 For No. S wire, B. ^ S. 
 
 For No. 10 wire, R. iV; S. 
 
 For No. 12 wire, li. iV: 8. 
 
 For No. 14 wire. P.. .V S. 
 Galvanized iron, sitlicin.u {.civt> si7.(> <if wire)^ 
 
 For No. S wire. B. W. G. 
 
 For No. !) wire. P.. AV. G. 
 
 l\»r No. IL' wire. 1'.. W. G. 
 
 For No. 14 wire. IV W. G. 
 Paper, splicinjr — 
 
 i by 3 inciies. 
 
 .'VlO l»y 3 inciies. 
 Lead, .splieinj: (.irive inside dinmetor ami lonsth) — 
 
 1 inch inside dinnietor (2 pounds ikm" foot) 
 
 Ij inches in.side diameter (2J pounds per foot), 
 li inches inside diameter (3* pounds per foot). 
 IJ inches inside diameter (4 pounds per foot). 
 
 2 inches inside diameter (4j pounds per foot). 
 2A inches inside diameter (4.S pounds per foot). 
 
 Slide rule, atmosphei-e. 
 
 Solder (see p. 71, this chapter, for description) : 
 
 Half and half. 
 
 Resin core. 
 
 Wiping. 
 Soldering kits. 
 
 Solderall. or Weldall, tuhc^, size No. 2. 
 Sounders, main-line. 
 Spectacles, smoked (in ca.se). 
 Splicing materials. (See p. 44. this chapter.) 
 Springs, hook-retaining. 
 Staples : 
 
 Blake, insulating. No. .". 
 
 (lalvanized iron (all standard sizes: give size required). 
 Stearine. 
 
 Steps, pole, .lialvanized iron, i; hy 10 inches. 
 Strand, messenger. (See Wire.) 
 Strajis. i>ii)e (give size required). 
 
 ^-inch (43 to the pound). 
 
 5-inch (35 to the pound). 
 
 A-inch (27 to the pound). 
 
 7-inch (20 to the pound). 
 
 1-inch (17 to the pound). 
 
 l^-inch (13 to the pound). 
 
 1^-inch (13 to the pound). 
 
 2-inch (."> to the pound). 
 
 3-inch (5 to the pound). 
 
 4G5S1°— 17 20 
 
 (299)
 
 18 Signal Corps Manual No. 3. — Chapter 8. 
 
 Strips : 
 
 Terminal, standard porcelain (12 pair). 
 Support, messenger : ■ 
 
 For iron poles. 
 For wooden pole^;. 
 Switchboard. (See p. 73, this chapter.) 
 Switchboard, camp telephone. (See p. 70, this chapter.) 
 Switches, knife : 
 
 S. P. S. T. (give voltage and amperes) — 
 
 Slate base, L'oO-volt, 25 amperes. 
 S. P. D. T. (give voltage and amperes) — 
 
 Slate base, 25U-volt, 25 amperes. 
 D. P. S. T. (give voltage and amperes) — 
 
 Slate base, 250-volt, 25 amperes. 
 
 D. P. D. T. (give voltage and amperes) — 
 
 Slate base, 250-volt, 25 amperes. 
 
 (Knife switches ai"e furnished in any number of poles and capac- 
 ities required ; also, fuse^l or unfused. In requesting switches or 
 repair parts for switches, state type and whether back or front con- 
 nected. ) 
 Switches, master: 
 For 16 targets. 
 For 24 targets. 
 Tacks, milonite, No. IS, black, brown, drab, or red. 
 Tags, cable, small. 
 Tape, insulating: 
 
 Friction (adhesive). 
 Rubber. 
 Telegraph set : 
 
 Induction, complete (1912) — 
 Key, sending, complete. 
 Box, battery. 
 Coil, induction. 
 Frame, card. 
 Knife switch. 
 Sounders, polarized. 
 Box, containing, wood (t)()X only). 
 Tulcpiu^nes. (See p. 78, this chapter.) 
 
 Telescopes (more complete description appears on p. 41, this chapter) ; 
 Type A. Warner & Swasey, 18 and 24 power. 
 Tyi)eC Warnei- <S: Swasey, 24 and 40 power. 
 Type D. Sussfeld, Lorsch & Co., 33, 35, and 40 power. 
 Type 10. Warner vV: Swasey, IS power. 
 Typ('(!. Lord P>ury type, 24, 30, and 40 power. 
 Terminals : 
 
 (.'arbons for. 
 
 Cook, can-top (fused and unfused), sizes 10 to 52, pairs — 
 10-pair, fused. 
 10-pair, unfused, M-4. 
 .52-pair, fused. 
 Fuses, type A-7, for. 
 
 (300)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 19 
 
 Thermometers : 
 
 Acid, 12-incli, unmounted. 
 
 Mercurial. 
 Thimbles, guy (state size of strand for which required), f-iuch. 
 Time interval : 
 
 Apparatus, motor-driven (1912). 
 
 Bells, large. 
 
 Bells, small. 
 
 Switch panel. 
 Torches, gasoline, small. 
 Trucks, lance. (See Wagons.) 
 Tubes, porcelain, uuglazed (give size and length desired) : 
 
 § inch b.v 4 inches. 
 
 g inch by 10 inches. 
 
 i inch by 4 inches. 
 
 i inch by 6 inches. 
 
 i inch by 10 inches. 
 
 g inch by 6 inches. 
 
 f inch by 8 inches. 
 
 g inch by 12 inches. 
 Turpentine. 
 
 Twine, lacing, Barbour's, 12-strand. 
 Typewriters. 
 Vane. wind. 
 Varnish : 
 
 Hard-oil finish. 
 
 Spar. 
 Voltammeter, portable, trii)le range, Weston, No. 280, 3-15-150 volts, 3-15-30 
 
 amperes, with case. 
 Voltmeter : 
 
 Bristol, r(K'ording. 
 
 Portable, in leather case. 
 
 Portable, .Tagabi. 
 
 Weston, model 280. 
 Voltmeters : 
 
 5-volt, Eldredge. 
 
 6-volt. 
 Wagons : 
 
 Kit (quartermaster's escort).* 
 
 Lance truck. 
 
 Repair (spring-instrument type). 
 
 Signal Corps instrument (quartermaster's escort).* 
 
 Telegraph (held wagon type).^ 
 
 Telephone (field wagon type).* 
 Washers : 
 
 Copper (all commercial sizes; give size required). 
 
 Galvanized iron, round or square (all commercial sizes; give size of bolt). 
 Waste, cotton. 
 
 1 Standard Army escort wagon. 
 
 2 Spring wagon (ambulance), instead of escort wagon, issued to the militia, when de- 
 sired, at a cost of .$199.50 each. Quartermaster's escort wagons, when required by the 
 militia, should be entered on requisition for quartermaster's supplies. 
 
 (301)
 
 20 Signal Corps Manual No. 3. — Chapter 8. 
 
 Wntrlios. wrist, willi wristlot. 
 Wristlet, for wrist watch. 
 Wheels, spare, lor wire carts. 
 Wire (see p. 81, this chapter) : 
 
 04 mils diameter, copper, iiisulali'd (No. 14 1>. & S.). 
 SI mils diameter, .lialvani/.ed iron (No. 14 K. W. (J.). 
 Twisted pair, 45 mils diameter, copper clad (No. 17 1>. vV S.). 
 Buzzer, on carriers. • 
 
 Counterpoise. 
 
 Field. 11-strand. 
 Wire : 
 
 Antenna. 7-strand, 32 mils (radio). 
 
 Antenna, 7-strand, 64 mils (radio). 
 
 Copper, hridle, 51 mils, ruhher-covered, single. No. 10 K. v^ S. 
 
 Copper, hard-drawn, 81 mils, No. 12 B. & S. 
 
 Copper clad, outside distrihuting, twisted pair. 45 mils. No. 17 1>. & S. 
 
 Galvanized iron, 144 mils (320 pounds per mile). No. .0 B. W. (J. 
 
 (Talvanized iron, 100 mils (190 potuids per mile). No. 12 B. W. U. 
 Wire : 
 
 Galvanized iron, 81 mils (9(5 pounds jier mile). No. 14 B. AN'. G. 
 
 Hou.se. twisted iiair, 36 mils, No. 19 B. tV; S. 
 
 Messen,irer strand — 
 §-inch. 
 ^-inch. 
 
 Pothead. 30 mils. No. 19 B. c^ S. 
 Wrenches : 
 
 Alligator, 8-inch. 
 
 ^lonkey, 8-iiich. 
 
 5 sets. 
 
 Zone signal equii)ment, complete: 
 
 Zone signal controller, 2-magazine. 
 
 Zone signal outlet. 
 
 Zone signal bell, 5-inch, 32-ohm. 
 
 Zone signal hell, 2i-inch, 32-ohm. 
 
 Switche.s, push, zone return signal. 
 
 Lamps, zone signal controller, Tungslen lilnmciil (1()-wall. (J-lSi). 
 
 l>amps, zone signal outlet, Tungst«'ii tilaiiienl (l(t-watl, S-17). 
 
 liOX. MKIAI,. 1 i;i!M IN \1,. 
 
 'rcrmiiial lioxcs iii'o sometimes desii'rd al disi i iiml ion puinls of an under- 
 ground cable system oi- ulicrc it is (l(>sired to terminate a limited number of 
 cables without installing the large distriliuting frame. 
 
 Wooden terminal boxes are still furnished in special instances, but the 
 latest standard terminal box is constructed of sheet metal. 
 
 Tlie first metal terminal boxes were installed in connection with llie standard 
 lire conli'ol system, <*oast defenses of Che.sapeaUtr F>ay. 'These boxes are of 
 siamped-sieel conslruciion and coiisist of two sejmrate ])arts. Ilu^ box proper 
 for containing the terminal sli-ips and cross connections and apron for pro- 
 tecting the cable ])otlieads. 'I'lie boxes are of the two-terminal strip size oidy, 
 it being the intention to install Iwo oi- more side by side if a greater terminal 
 striji cai)acity is reiiuired. 
 
 (.302)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8, 21 
 
 Fig. 8-1.— BOX, METAL, TERMINAL, 1915 MODEL. 
 
 Part 
 No. 
 
 Xame. 
 
 Box, complete (give strip capacity) . 
 
 Box, door for " . . 
 
 Box, apron door for 
 
 Reference 
 No. 
 
 TTt 
 
 [-1 
 
 m 
 
 S 
 
 -? 
 
 
 (yj\ [(7) 
 
 
 
 )^i 
 
 ^ -"4 • ^ 
 "l '.4 :A 
 
 tfc^ tfc^ 
 
 •o:^ 
 
 ^ Trl 
 
 FRONT VIEW 
 
 T^-l 
 
 i.^*'A^-^'S^^>'^ ''" l-Ja^^:^.->-]^i>"'^"''^^ 
 
 "" WLS h 
 
 fc;^-^^. 
 
 SIDt CROSS SECTION SECTION ON A-B 
 
 Fig. 8-2.— STRIP. TERMINAL, STANDARD. 
 
 (303)
 
 22 Signal Corps Manual No. 3. — Chapter 8. 
 
 A new metal terminal box has been designed. This terminal box is con- 
 structed of No. IS-gauge sheet steel, the box proper and apron for housing pot- 
 head being combined. This box will be furnished in three sizes, namely, two- 
 strip, four-strip, and eight-strip, respectively, and while it is believed that these 
 three sizes will meet the usual ueeds of the service, any one of the sizes may be 
 installed in combination with either of the other two sizes. 
 
 The two-strip size may be iised for either one or two strips, holes being pro- 
 vided for placing the terminal strip in center of box when the one-strip size is 
 desired. The principal features of the new type of box are as follows: 
 
 The cross piece supporting the lower door at bottom may be conveniently re- 
 moved and replaced. This is thought to be very desirable, especially in the larger 
 sizes, when pot heading cables is in progress. The terminal box proper is equipped 
 with a bottom with apertures for brass tubes through which the cables or pot 
 heads of cables enter the main terminal box. It is intended that these tubes shall be 
 closed by means of sealing compound, it being necessary to place a disk of 
 wood or other material in tho.se not in use, before sealing. For those in use, 
 excess space should be closed with waste or oakum before pouring the com- 
 pound. This feature is believed to be very important, inasnuich as heavy 
 leakage has previously occurred in terminal boxes not so equipped, due to the 
 warm air from duct line entering the main portion of terminal box and there 
 condensing when atmospheric changes have occurred. Entrances for the house 
 wires have been provided by means of one slot in center of top of box of the 
 one and two strip size and two or more in the other two sizes. Boxes will be 
 furnished with these slots closed by means of a small piece of metal clamped to 
 the box with machine screws, it being intended that those slots not in use will 
 remain closed by this means, and that those in use will be covered by the 
 molding through which wires are led to the box. 
 
 Figure 8-1 shows the one and two strip size, the four and the eight strip 
 size differing only in the horizontal dimension as far as size is concerned. 
 
 Figure 8-2 shows construction of the Signal Corps standard terminal strip 
 which is invariably used with the metal terminal boxes. 
 
 BELI.S, EXTENSION, I.OT'I) UINOING. 
 
 The extension bell, loud ringing, is installed as an extension to the ringer 
 (call bell) of a telei)hone when telephone is installed where noise interferes 
 with hearing of the telephone ringer or where it is desired to hear a call 
 distant from telephone. The type issued by the Signal Corps is weatherproof 
 and is equipped with 6-inch gongs and a 2 m. f. condenser. The condenser 
 is connected in series with magnet windings which are wound to a total 
 resistance of 2.500 ohms (each magnet 1,2.')0). These bells should be con- 
 nected in parallel with the telephone line circuit, the condenser preventing the 
 operation of signal at coimnon battery switchboard should the telephone be 
 comiccted to such an api)aratus. Figure S-3 illustrates tlio extension bell, loud 
 ringing. Small exttiision bells are furnished for indoor use. 
 
 (804)
 
 Technical Equipment Issued by the Signal Corps.— Chapter 8. 23 
 
 Fig. 8-3.— BELL, EXTENSION, LOUD RINGING. 
 
 Part 
 No. 
 
 Name. 
 
 Base 
 
 Cover 
 
 Gong 
 
 Gong, cuj) nut for 
 
 Permanent magnei 
 
 Electromagnet 
 
 Adjusting eccentric, with screw. 
 
 Binding post 
 
 Condenser 
 
 Reference 
 No. 
 
 1 
 
 2 
 
 3-3 
 
 4-1 
 
 5 
 
 6-6 
 
 SIGNAL CAKT. 
 
 For transportinsr in the field a large assortment of signaling equipment the 
 Signal Corps has recently designed and constructed a vehicle termed " Signal 
 cax't ". This cart is arranged to be drawn by one horse or mule and can be 
 closed to protect contents from the elements. The interior is equipped with 
 jiartitions suitalily arranged for separating . and holding rigidly iti phice the 
 following signaling equipment which forms a complement : 
 2 axes, hand lineman. 
 S batteries, tungsten, type A. 
 18 bool<s, field message. 
 •J buckets, water, canvas. 
 25 candles, lantern. 
 60 cartridges, Very, green. 
 60 cartridges. Very, red. 
 60 cartridges. Very, white. 
 2 cases, map. 
 16 charges, carbide. 
 4 compasses, pocket. 
 
 (305)
 
 24 
 
 Signal Corps Manual No. 3.— Chapter 8. 
 
 4 disks, cijilicr. 
 
 -<1<) oiivolKpi's. iiicss:mc. 
 
 y eratior.s. i-ubher. 
 
 4 flashlijihts. Ever lieaily. 
 
 6 glasse.s, field, type EE. 
 
 4 lielioiiraplis. complete. 
 
 4 kits, flag, 2-foot. 
 
 4 kits, flag. 4-foot. 
 
 i' kits, inspectors, pocket. 
 
 4 lanterns, field, acetylene. 
 
 4 lanterns, candle, foNling. 
 
 -4 matches, wind, boxes. 
 
 -4 pencils, lead. 
 
 4 pistols. Very. 
 
 11' rockets, .sequence. 
 
 12 rockets, yellow smoke. 
 
 4 spectacles, smoked, with cases. 
 
 Figure S-4 shows the arrangement ..f tlu> signal cart. 
 
 Fig. 8^.— CART, SIGNAL. 
 
 CAIV.K. 
 
 For general des.-npth.,, illus, ra. ions, ,„;,„„..,• ..r spllHng and inslallation of 
 
 -'I.-, .-MM. sysl.MMS and ud.l.-s nC .„,„ hnes, .ppn.ve.l ,yp..s. ,l,e .vader is 
 
 H.M-red ,., ( hapter 1 .,r ,„is .nanu.-d. K.,,-, ,is,s .„■ ,,,1 .-nhies „sed U, dale 
 
 should"; '"■'"•""! '"?'"■" '•'' = "•"•"■'-"<- •"• "-•>' 'yp.-, Ihe (ollowing tables 
 M. mid be ..x..u,n,H.d. I, will 1.,. ,,..,,.1 Ihal latest :,ppn,ved (vpes are als.. 
 indicated in thes,. |id)les. 
 
 (.-.Odi
 
 Technical Equipment Issued hy the Signal Corps. Chapter 8. 
 
 For <-i)iivciiicii(i' llic Siu'iiiil <'<'i'|is cMhlfs iii:iiinrii<lun'(l Id ihilc may Itf di- 
 vidt'd iiitn six classes, viz: 
 
 Kul)l)er insulation. sul)niariii(', serial I.v])c Nos. 1 to L'(mi. 
 
 Rubber insulation, subterranean, serial type Nos. 201 lo ,S(H). 
 
 Pajier insulation, arnioi-e<l, serial type Nos. 301 to 400. 
 
 I'aper Insulation, aerial, imarniored, serial type Nos. 401 to ."i(M). 
 
 Special types, serial type Nos. HOI to 000. 
 
 Power cables, serial tyi>e Nos. 0(»1 lo Ton. 
 
 Description of iiiixs of ruhhcr-iuKuUtiion submarine cables. 
 
 1 
 
 
 2 
 
 
 3 
 
 1 
 
 4 
 
 5 
 
 9 
 10 
 
 Desisiwlion. 
 
 9 
 
 ^ 
 
 10 
 
 7 
 
 11 
 
 7 
 
 12 
 
 1.3 
 
 i:i 
 
 Hi 
 
 U 
 
 1 -, 
 
 17 
 17 
 
 10 
 
 17 
 
 17 
 
 
 
 {1899 
 1900 
 {1889 
 1900 
 {1899 
 1900 
 
 l-conductor, experimental, lifiht 190' 
 
 2-conductor 190 
 
 .5-conductor, 1-pair, 3-straight 190 
 
 7-conductor, 2-pair, S-straight 
 
 9-eonductor, 3-pair, 3-straiKht 
 
 11-conductor, 4-pair, 3-straight 
 
 13-conductor, 3-straight, 5-pair 
 
 17-conductor, 7-pair, 3-straight 
 
 l-conductor 
 
 3-conductor, San Francisco 
 
 4-conductor, New London 
 
 2-conductor 
 
 l-conductor 
 
 
 
 1 
 
 Conductor. 
 
 
 
 
 
 
 
 
 
 o o 
 
 1 
 
 1 
 
 22 . 
 
 g 
 
 
 
 
 T. 
 
 — i — 
 
 p. 
 
 IS 
 
 3 
 
 19 
 
 4 
 
 20 
 
 5 
 
 21 
 
 G 
 
 22 
 
 14 
 
 23 
 
 14 
 
 24 
 
 14 
 
 2.3 
 
 14 
 
 2fi 
 
 14 
 
 27 
 
 14 
 
 28 
 
 14 
 
 29 
 
 338 
 
 30 
 
 338 
 
 31 
 
 338 
 
 32 
 
 338 
 
 33 
 
 338 
 
 34 
 
 338 
 
 190 
 
 190 
 
 190 
 
 190 
 
 190: 
 
 1902 
 
 1902 
 
 1902 
 1902 
 1902 
 
 l-conductor, Int. , Alaskan 1903 
 
 2-conductor, Int., Alaskan 1903 
 
 l-conductor, rock, Alaskan 1903 
 
 I 
 l-conductor. shore end, Alaskan ! 1903 
 
 I 
 
 l-conductor, deep-sea, Alaskan ' 1903 
 
 F. C, Portland, 4-pair ' 190:J 
 
 F. C, Portland. 4-pair. and 4-stralght '\ 1903 
 
 F. (".. Portland. 2-pair. and 4-straight. 
 F. C. Portland. 3-pair. and 3-straight . 
 4-pair. 3-straiglit 
 
 4-pair, 4-straight 
 
 2-pair 
 
 l-conductor, F. C 
 
 2-pair, F. C 
 
 3-pair, F.C 
 
 4-pair, F.C 
 
 5-pair, F. C 
 
 G-pair, F. C 
 
 1903 
 1903 
 1903 
 
 1903 
 
 1903 
 1905 
 1905 
 1905 
 1905 
 1905 
 1905 
 
 ajS 
 
 28.5 
 20.1 
 20.1 
 20.1 
 28.5 
 
 20.1 
 28.5 
 28.5 
 20.1 
 28.5 
 20.1 
 28.5 
 20.1 
 28.5 
 20.1 
 28.5 
 20.1 
 28.5 
 20.1 
 28.5 
 
 28.5 
 
 28.5 
 
 28. 5 
 
 28.5 
 
 51 
 
 22.0 
 
 51 
 
 22.0 
 
 51 
 
 22. G 
 
 51 
 
 22. 
 
 51 
 
 22. G 
 
 20.1 
 
 28. 5 
 
 20.1 
 
 2S.5 
 
 20.1 
 
 2.S. 5 
 
 20.1 
 
 28.5 
 
 20.1 
 
 28.5 
 
 20.1 
 
 20.1 
 
 28.5 
 
 20.1 
 
 20.1 
 
 20.1 
 
 20. 1 
 
 20. 1 
 
 In. 
 
 A } 
 
 81 
 81 
 162 
 162 
 102 
 91 
 51 
 182 
 
 182 
 204 
 
 2{ 
 
 
 128 
 114 
 229 
 144 
 144 
 102 
 
 102 
 325 
 162 
 
 258 
 
 91 
 
 162 
 204 
 
 114 
 
 !ti2 
 
 204 
 
 120 
 120 
 120 
 144 
 162 
 2(M 
 204 
 
 (Continui-il on noxt page.) 
 
 (307t
 
 26 Signal Corps Manual No. 3. — Chapter 8. 
 
 Description of tapes of riihher-itisulatloii suhmarine rf/6/rs— (_'oiitiiiued. 
 
 35 
 
 no 
 
 40 
 
 334 
 
 41 
 
 33S 
 
 42 
 
 374 
 
 43 
 
 375 
 
 o44 
 
 419 
 
 045 
 
 420 
 
 46 
 
 421 
 
 47 
 
 424 
 
 o.tO 
 
 431 
 
 ool 
 
 431 
 
 a52 
 
 431 
 
 ao3 
 
 431 
 
 a54 
 
 431 
 
 a5,T 
 
 431 
 
 056 
 
 431 
 
 57 
 
 431 
 
 58 
 
 431 
 
 59 
 
 431 
 
 60 
 
 431 
 
 61 
 
 431 
 
 62 
 
 431 
 
 G3 
 
 431 
 
 64 
 
 478 
 
 a66 
 
 4W 
 
 Designation. 
 
 Conductor. 
 
 1-condiu'lor. deep-sea, Alaskan 
 
 1-conductor, Int.. .Vla.skan 
 
 1-conductor, shore end. Ala.skan 
 
 1-conduetor, deep-.sea. Pliilipplnes — 
 
 1-conductor. .shore end, Plulippmes . . . 
 
 1-condnctor. .special, light 
 
 2-conductor. F. C 
 
 3-pair. special 
 
 3-pair special 
 
 1-conductor. intermediate. 
 
 1-condiictor, deep-sea 
 
 1-conductor 
 
 1-conductor, Philippines 
 
 1-conductor 
 
 2-conductor 
 
 4-conductor 
 
 (i-conductor 
 
 S-conductor 
 
 10-conductor 
 
 12-condiictor 
 
 1-conductor, douhle armor 
 
 2-conductor, double armor 
 
 4-condiictor, double armor 
 
 0-conductor, double armor 
 
 8-conductor, double armor 
 
 10-conductor. double armor .*. 
 
 12-conductor, double armor 
 
 l-conductor. small 
 
 1-conductor, .shore end. double armor 
 
 190.J 
 
 1905 
 
 1905 
 
 1905 
 
 1905 
 
 1905 
 1905 
 1905 
 
 1905 
 
 1906 
 1906 
 1906 
 1906 
 1906 
 1906 
 1906 
 1900 
 1906 
 1906 
 1906 
 
 1900 
 
 190G 
 
 1906 
 
 1906 
 
 1900 
 
 1906 
 
 1906 
 1907 
 1915 
 
 C3 O *= 
 
 51 
 
 22. 6 
 
 51 
 
 22.6 
 
 51 
 
 22.6 
 
 28.5 
 
 28.5 
 
 20.1 
 20.1 
 
 28. 5 
 
 28. 5 
 
 32 
 32 
 32 
 32 
 
 28.5 
 28.5 
 28.5 
 28.5 
 28.5 
 28.5 
 28.5 
 
 28.5 
 28. 5 
 28.5 
 28. 5 
 28.5 
 28,.-. 
 
 28. 5 
 2S. 5 
 32 
 
 s 
 
 Jn. 
 
 ■h 
 
 
 A 
 
 102 
 
 / 102 
 \ 258 
 128 
 f 128 
 \ 201 
 51 
 120 
 144 
 144 
 229 
 162 
 91 
 91,162 
 128 
 144 
 144 
 162 
 204 
 204 
 229 
 229 
 144 
 229 
 144 
 229 
 162 
 229 
 204 
 229 
 204 
 2.S9 . 
 229 
 289 
 229 
 289 
 51 
 162 
 263 
 
 " Inilicates ajjprovcd (yi)es 1o bo jiurchased in the future. 
 
 Siibmarino onhlos for deep sen ;ir(> usually <lpliverp(l in li'n,L:;tli.s oT not loss 
 than 1") miles. 
 
 The following cables are usually furnished on i-eels in the t'oilowini;- leniitlis: 
 Types. 20, 80, 41. f.d, .".1, an<l .vj in lengths of 2 miles. 
 Types .'{1. 82. .13, and ."1 in Im^llis of 1 mile. 
 Types 88, 84. ;"», ilO. and 04 In len.iitiis of one-half iinle. 
 Types ~u to 08, ineluslve. in siuvial leiijiths, 
 Deei)-sea sinjrle-conductor cable, as indicated in lyjies 8. 1(5. and 88. will 
 weiLdi a!)proxinia1cly .'i.OdO itouiids lo the mile. 
 
 (S08)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 27 
 
 The approximate weight of the following rallies per statute mile is: 
 
 Pounds. 
 
 Type 29 2, 800 
 
 Tvpe 30 10, 000 
 
 Type 31 12. 500 
 
 Type 32 15, 000 
 
 Tvpe 33 21, 000 
 
 Tvpe 34 25, 000 
 
 Type 41___-_ —-^ '- 0. 000 
 
 The o](l .MaskuH cables weififh luM- statute milo approximately as follows: 
 
 Pounds. 
 
 Type 35 3. 425 
 
 Tvpe 36 5. 450 
 
 Type 37 20. 000 
 
 I)cfirrii>tio)i of tiii'cx of ruhJtcr-insuhiiiou fnihtcrrancan rahlca. 
 
 
 d 
 
 
 Z 
 
 
 a 
 
 
 o 
 
 
 
 
 
 
 03 
 
 ^ 
 
 tC 
 
 
 
 
 s, 
 
 H 
 
 m 
 
 201 
 
 
 202 
 
 
 203 
 
 
 204 
 
 
 20.5 
 
 
 206 
 
 
 207 
 
 V2 
 
 208 
 
 12 
 
 209 
 
 12 
 
 210 
 
 12 
 
 211 
 
 13 
 
 212 
 
 13 
 
 I'm 
 
 429 
 
 0214 
 
 429 
 
 021.5 
 
 429 
 
 0210 
 
 429 
 
 a217 
 
 429 
 
 a21S 
 
 429 
 
 0251 
 
 540 
 
 Designation. 
 
 1-pair. 
 3-pair . 
 
 5-pair 
 
 6-pair, and 8-straight . 
 5-pair . 
 
 Conductor. 
 
 Q 
 
 1902 
 1902 
 1902 
 1902 
 1902 
 
 6-pair, and 8-straight 1902 
 
 1-pair 1902 
 
 3-pair 1902 
 
 1902 
 1902 
 1902 
 1902 
 1900 
 1906 
 1906 
 1906 
 1906 
 1906 
 
 ;-pair 
 
 6-pair 
 
 8-pair, and 8-straight. 
 
 6-pair . 
 
 8-pair, and 8-straight 
 
 1-pair 
 
 3-pair 
 
 6-pair 
 
 12-pair 
 
 ()-pair .' 
 
 12-pair 
 
 1-pair, armored, Greenfield type. 
 
 p'S 
 
 40 
 
 40 
 
 40 
 
 40 
 
 40 
 
 40 
 
 22.6 
 
 22.6 
 
 22.6 
 
 22.6 
 
 22.6 
 
 22.6 
 
 28.5 
 
 28.5 
 
 28.5 
 
 28.5 
 
 28.5 
 
 28.5 
 
 40 
 
 U C3 
 
 s 
 
 C3 
 
 5 
 
 Inch. 
 
 A 
 ■h 
 -h 
 
 Inch. 
 
 128 
 144 
 
 128 
 144 
 
 128 
 
 144 
 
 Steel 
 
 tape. 
 
 " Indicates approved types to be purchased in tlie future. 
 
 These ruhher-insnlatioii subterranean cables are furnished on reels, as fol- 
 lows : 
 
 Types 213 and 214 in one-half mile leiifrths. 
 Types 2in. 216, 217. and 218 in leuirths of 1.000 feel. 
 The weiirht of the standard cables per statute mile is as follows: 
 
 Pounds. 
 
 Type 213 ",000 
 
 Type 214 0, 2(X1 
 
 Type 215 H, 100 
 
 Type 216 1-*, "85 
 
 Type 217 . 18, 800 
 
 T^pe 218 - -«• 000 
 
 (309)
 
 28 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 The usual reel for the shipnieiit of these types of cable weighs 400 p(»un(ls, 
 has a length of 30 inches, a drum diameter of 34 inches, and sides 5 feet ti 
 inches high. 
 
 TupcH of pu per-inaulution annorcd cable. 
 
 Tvpe 
 No. 
 
 301 
 302 
 
 305 
 306 
 
 310 
 311 
 
 313 
 314 
 
 316 
 
 317 
 
 318 
 
 319 
 
 320 
 
 0321 
 
 322 
 
 0324 
 
 "325 
 
 "326 
 
 "327 
 
 Speci- 
 flca- 
 tion 
 No. 
 
 8 
 129 
 
 174 
 
 174 
 
 339 
 
 427 
 
 / 339 
 
 \ 427 
 
 / 339 
 
 \427 
 
 ( 339 
 
 \ 427 
 
 / 339 
 
 \ 427 
 
 j 339 
 
 \ 427 
 
 / 339 
 
 \427 
 
 f 237 
 
 \427 
 
 / 237 
 
 \427 
 
 / 237 
 
 t 427 
 
 / 237 
 
 \427 
 
 / 237 
 
 ;\ 427 
 
 / 237 
 
 427 
 
 372 
 
 373 
 
 427 
 
 427 
 
 427 
 
 427 
 
 427 
 
 427 
 
 427 
 
 ppsignation. 
 
 Date. 
 
 10-pair ' 1901 
 
 25-pair...- | 1904 
 
 20-pair, combination 1904 
 
 2.">-pair, comliination ' 1904 
 
 \, „. n905 
 
 \.„ . /1905 
 
 \,. . (1905 
 
 '20-pair /{\f^l 
 
 \„. . 1/1905 
 
 •30-pair te 
 
 .„ . • /1905 
 
 '^0-pai'" 1\1908 
 
 5-pair.. 
 10-pair. 
 
 /1905 
 \1908 
 /1905 
 \1908 
 ,, . /1905 
 
 l^P^"' ■-•,\1908 
 
 ^2->pair ,{i908 
 
 ^aopair igs 
 
 bO-pair |i9o^ 
 
 5-pair, special 1905 
 
 do 1905 
 
 5-pair 1906 
 
 10-pair 1906 
 
 15-pair 1906 
 
 20-pair ' 1906 
 
 25-pair I 1906 
 
 30-pair 1906 
 
 oO-paii- ' 1906 
 
 Conductor, 
 
 diameter of 
 
 each strand 
 
 in mils. 
 
 Insulation. 
 
 36 ' Double, paper. 
 
 36 do 
 
 (S-pair, 36 I 
 
 {l2-pair ■ do 
 
 |3-strand,28.5 I 
 j 10-pair, 36... 
 
 < 15-pair > do 
 
 l3-strand,28.5 | 
 
 ....I do 
 
 |36. 
 
 }».. 
 
 |36.. 
 }3.,.. 
 }36.. 
 I36.. 
 |36.. 
 }36.. 
 |36.. 
 
 }«.. 
 
 36.. 
 
 -do. 
 , .do. 
 
 .do. 
 ..do. 
 ..do. 
 ..do. 
 ..do. 
 ..do. 
 . .do. 
 . .do. 
 . .do. 
 
 .\rmor wire, 
 
 diameter in 
 
 mils. 
 
 144 
 144 
 
 120 
 
 120 
 120 
 120 
 144 
 144 
 144 
 204 
 
 Thick- 
 ness of 
 
 lead 
 sheath. 
 
 Inch. 
 
 -do. 
 
 .do. 
 .do. 
 .do. 
 .do. 
 -do. 
 .do. 
 .do. 
 .do. 
 .do. 
 
 J and A 
 J and A 
 J and A 
 1 and ,^ 
 ; and -h 
 ; and h 
 
 144 
 144,204 
 204 
 204 
 204 
 229 
 229 
 229 
 229 
 
 " Indicates approved types to he purcha.sed in the future. 
 
 The armored paper-insulation cables ar(> su[)pli(Ml under (H'rtnin C(»nditions for 
 submarine work. Tiiey may also \)v used for subterraiu>an work. 
 Type 303 weighs 22,()00 pounds per stalut*' mile. 
 TyjK' 304 weighs 25,000 poiiinls ]n'v slatulc nillc. 
 Types 303 and 304 when shipix'd in mile IculiIIis aro pi-ovidcd witli reels weigh- 
 ing ."i,0(M) pounds, iiaviiig a Jcngl b of 7 feci, a diameter of side of S feet, and a 
 shaft ") inches iti diameter and Ki leel bmg. 
 
 The.se cables are usually ordered in lengths to s\nt the installation for which 
 lliey are designed, so as to be inslalle(| willioul splices. 
 
 (310)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 29 
 
 Types of (louhJc jxijitr-iiisiildtioii, Icdd-covc red. iiiKiniiond cable. 
 
 Type 
 No. 
 
 "401 
 
 "402 
 
 "403 
 
 1404 
 
 ''40.'> 
 
 "40(1 
 
 "407 
 
 "40S 
 
 "409 
 
 411 
 
 412 
 
 413 
 
 414 
 
 415 
 
 41ti 
 
 417 
 
 41S 
 
 419 
 
 Designation. 
 
 10-pair. 
 1.5-pair.. 
 20-pair.. 
 2.5-pair. . 
 30-pair.. 
 40-pair.. 
 .5()-pair., 
 ".Vpair. . 
 UM»-pair 
 10-pair.. 
 l.vpair.. 
 20-pair.. 
 25-pair.. 
 3n-pair.. 
 40-pair.. 
 ."iO-pair.. 
 7.5-pair.. 
 100-pair. 
 
 Con- 
 ductor, 
 diameter 
 of each 
 strand 
 in mils. 
 
 36 
 
 36 
 
 36 
 
 36 
 
 36 
 
 36 
 
 36 
 
 36 
 
 36 
 
 2.1.3 
 
 25. 3 
 
 25. 3 
 
 25. 3 
 
 25. 3 
 
 25.3 
 
 25. 3 
 
 25.3 
 
 25.3 
 
 Thick- 
 ness of 
 
 lead 
 sheath. 
 
 .Vppro.x- 
 
 imate 
 outside 
 diameter. 
 
 Inchfs. 
 0. 722 
 .797 
 .872 
 .922 
 .982 
 1. 113 
 1.208 
 1.443 
 l.t)38 
 .607 
 .682 
 .7.37 
 .787 
 ..827 
 .943 
 1.023 
 1.193 
 1.353 
 
 Weight 
 per stat- 
 ute mile. 
 
 Pounds. 
 5, .370 
 6. 193 
 7,0.>4 
 7, 693 
 8,416 
 11,083 
 12,445 
 15, 829 
 18, 860 
 4, 229 
 4,937 
 5. .549 
 6.088 
 ii,.520 
 8,664 
 9, fi46 
 11,890 
 14, 0.50 
 
 Weight 
 
 per l,0fKi 
 
 feet of 
 
 ca1)le 
 
 and reel. 
 
 1,180 
 1.368 
 1.55S 
 1,700 
 l,8t» 
 2,448 
 2, 7.50 
 3,497 
 3,967 
 935 
 1,093 
 1,226 
 1,345 
 1.441 
 1.914 
 2.131 
 2,627 
 3,106 
 
 n Indicates approved types to be purchased in the future. 
 
 Tills cat)!*' i.s iisimlly furnished on reels in lengths of 1,000 feet; length is 
 slated in purchiisc order, ('able reels are usually 33 inches in length, and 
 diameter from .IG to 72 inches. 
 
 Types of poirer cahlcs i Siiecifiratinii 'i-ll). 
 
 Type Nos. 
 
 1 
 
 3 
 
 2 
 
 •3 
 g 
 
 a 
 
 o 
 
 ter of single wires- 
 mils. 
 
 ance of conductor 
 1,000 feet, 68° F. 
 
 — 3 
 
 Length on 
 reel. 
 
 o 
 © 
 
 s 
 a 
 
 .2 
 
 •V 
 
 2 
 
 .a 
 
 i-i 
 
 hi 
 
 
 "3 . 
 CO 
 
 ■^ a 
 
 
 a> 
 
 <B 
 
 <9 
 
 S^ 
 
 u 
 
 .a 
 
 a 
 
 
 ^ 
 
 ©CO 
 
 ■2:i-V 
 
 o 
 
 bo 
 
 Ml 
 
 P. 
 
 o. 
 
 
 '55 0< 
 
 
 so-O 
 
 ^ftg 
 
 
 y 
 
 a 
 
 g 
 
 3 
 
 a 
 
 2 
 
 3 
 
 
 s 
 
 ^ 
 
 c a 
 
 s: 
 
 an 
 
 M 
 
 ft 
 
 ft 
 
 <; 
 
 ^ 
 
 5 
 
 ei 
 
 e 
 
 in'' 
 
 ft 
 
 Eh 
 
 < 
 
 
 
 
 
 
 
 
 
 Inch. 
 
 Feet. 
 
 Feet. 
 
 Inch. 
 
 
 601 
 
 621 
 
 641 
 
 661 
 
 4,107 
 
 1 
 
 64.08 
 
 2. .521 
 
 A 
 
 2,000 
 
 1,000 
 
 ^ 
 
 120 
 
 602 
 
 o622 
 
 1642 
 
 a 662 
 
 (i, .530 
 
 1 
 
 80.81 
 
 1..586 
 
 A 
 
 2,000 
 
 1,000 
 
 ^S 
 
 120 
 
 603 
 
 1623 
 
 1643 
 
 a m-i 
 
 10, 3.^ 
 
 1 
 
 101.9 
 
 . 9972 
 
 
 1,.500 
 
 1,000 
 
 i 
 
 120 
 
 604 
 
 624 
 
 atV44 
 
 o6(>4 
 
 16, 510 
 
 7 
 
 48. 6 
 
 .6271 
 
 
 1,.500 
 
 1,000 
 
 i 
 
 120 
 
 605 
 
 a 625 
 
 atV15 
 
 o665 
 
 26, 2.50 
 
 ' 
 
 61.2 
 
 .3344 
 
 ■h 
 
 1,.500 
 
 1,(X¥) 
 
 
 144 
 
 606 
 
 a 626 
 
 <i646 
 
 a am 
 
 33.100 
 
 
 ()8.8 
 
 .3128 
 
 A 
 
 l,.50O 
 
 1,000 
 
 I 
 
 144 
 
 607 
 
 a 627 
 
 a(>47 
 
 a 667 
 
 41,740 
 
 7 
 
 77.2 
 
 .2480 
 
 A 
 
 1,.500 
 
 1,000 
 
 I 
 
 162 
 
 cm 
 
 628 
 
 648 
 
 6tV8 
 
 .52,a30 
 
 19 
 
 .52. 6 
 
 .1967 
 
 A 
 
 1..500 
 
 1,000 
 
 
 162 
 
 609 
 
 629 
 
 649 
 
 (569 
 
 $6,370 
 
 19 
 
 .59.1 
 
 . 1.560 
 
 
 1,000 
 
 1,000 
 
 J 
 
 162 
 
 610 
 
 630 
 
 6.W 
 
 670 
 
 M,f.90 
 
 19 
 
 (i6. 4 
 
 .1237 
 
 
 1,000 
 
 1,000 
 
 
 162 
 
 611 
 
 631 
 
 651 
 
 671 
 
 105,. 500 
 
 19 
 
 74.5 
 
 .09811 
 
 
 1,000 
 
 1,000 
 
 J 
 
 162 
 
 612 
 
 632 
 
 652 
 
 <i72 
 
 133, 100 
 
 19 
 
 a3.7 
 
 .07780 
 
 
 1,(X)0 
 
 1,000 
 
 i 
 
 162 
 
 613 
 
 633 
 
 653 
 
 t)73 
 
 167,800 
 
 19 
 
 94.0 
 
 .0(il70 
 
 
 1,000 
 
 1,000 
 
 
 162 
 
 614 
 
 634 
 
 654 
 
 674 
 
 211,600 
 
 19 
 
 105.5 
 
 .04893 
 
 A 
 
 1,000 
 
 1,000 
 
 * 
 
 162 
 
 1 1ndicates approved types to be purchased for stock in the future. 
 
 Special types of power cable that have I)een purchased in the iiast for special 
 purposes are as follows : 
 
 Type No. G29ff conforms to type No. (i2!). with the exception that one wire, 
 o9.1 mils in diameter, of the condmtor is reiilaced by a potential condu<-tor 
 made up as follows : Conductor to consist of 16 strands copper wire, each 10 
 
 (311)
 
 30 Signal Corps Manual No. 3. — Chapter 8. 
 
 mils in diameter, having an area of 1,600 circular mils, with a serving of cotton 
 and covered with an even layer of rubber compound to a uniform diameter of 
 one-tenth (ro) inch, the conductor being well centered in the insulation. 
 
 Type 643fl conforms to type 643, except that four conductors i02 mils in 
 diameter are supplied. 
 
 Type 663tf conforms to type 663. except that four conductors 102 mils in 
 diameter are supplied. 
 
 The reader. is referred to chapter 4 of this manual for general information 
 concerning cable, its installation and accountability. 
 
 SrBMAJUNE (ABLE GEAK AND SUPPLIES. 
 
 Anchors, mushroom, ordinary. Supplied in sizes of 1. 2, 2A. 3. 4. and ,"> 
 hundredweight. 
 
 Anchors, mushroom, patent (Johnson's patent removable shank). Supplied 
 in sizes of 1, 2, 24, 3, 4, and 5 hundredweight. 
 
 Blocks, wood or iron. Specify whether plain or snatch type, number of 
 sheaves, and length of block in inches. 
 
 Buoys, automatic whistling. Weight. 18 lunuh-edweight ; safe load, 2.1 hun- 
 dredweight. 
 
 Buoys, cablp. Specify length and diameter or carrying capacity desired, or 
 both. These can be obtained in capacities from 3 hundredweight to 6 tons. 
 Specify bridle chains for same when desired. 
 
 Boats, cable (also called cable cutters). 
 
 Blades for hacksaws ; dozen. Specify length. 
 
 Chain, bridle. Usually made uj) in lengths as desired and fitted with egg links 
 at each end. Necessary to specify size of links or state breaking strain. The 
 type is usually crane chain and size is the thickness of the link. To obtain 
 exact duplication, al.so specify the oiitside width of the link and the pitch, 
 which is the distance between similar points of successive links. 
 
 Charts. Give serial number and specify whether Coast and Geodetic Survey 
 or Hydrographic Office edition. 
 
 Chronometers, marine. 
 
 Clamjis, buoy lamp. 
 
 Coats, oilskin. 
 
 Counters, revolution. 
 
 Core, cable, feet. For test-room connections and leads. 
 
 Couplings, for chains. Specify size and kind of coupling, wlietiier with 
 swivel and egg links or simply shackles. 
 
 Crinolines, cable tank. Manufactured only according to specifications for 
 each particular case. 
 
 Cut-meter. This is a direct-reading sju'ed indicator which c;in be applied to 
 any moving surfiice. 
 
 ♦ 'utters, cal)h'. A ixirtable bolt cutter tluif may i)e nxtunted on a block with 
 b.indles. It is su]iplie(l for u.S(! about the decks of cable ships. 
 
 Dividers, i)ropftrtional. 
 
 Dividers, steel, navigator's. 
 
 Dynamometers, large size 25 tons sti-ain. sninll size strains to 10 tons. 
 
 Frames, hacksaw. Adjustable f\H"nis]ie(l unless length is st;ited. 
 
 Gauges, wire. 
 
 Grapnels, ordinary H-pntng laii be ol)tained in sizes of 1, U, 2, 2^, 24 long 
 prong, 3, and 3^ hundredweight. 
 
 (312)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 31 
 
 Grapnels, boat, weight al^out 23 pounds. 
 
 Grapnels, Janiies(ni"s rook, 2 types, one having Hal prongs and tlie otiier with 
 Itrongs forked at shank. Type with flat prongs preferred. 
 
 Grapnels, Johnson's renewable section. 
 
 Spare prongs for same, short. 
 
 Spare prongs for same. long. 
 
 Grapnels, Lucas patent cutting and holding, complete, witii knives. 
 
 (Jrapnels. centipede, can ])v (il)taiiu'd in sizes of X, li ^h 2, 2A. ;{, and Si 
 hundredweight. 
 
 Grapnels, centipede, boat, weight 30 pounds. 
 
 Grapnels, Murphy's patent centipede, in sets of 6 each, oonsisiiug of -1 grap- 
 nels and 2 spare, and including 4 shackles. Can be obtained in 4 sizes, weights 
 per section as follows : 20, 45, 5."), 85 pounds each. 
 
 Hats, oilskin. 
 
 Hose, steam, flexible copper, 1?, and 2 inch sizes. 
 
 Hose, steam. 5-pIy rubber, l™ and 2 inch sizes. 
 
 Hose, .steam, 8-pIy rubber, wire-wound, 11 and 2 inch sizes. 
 
 Hose couplings. Re(piisition for steam hose specify length of sections. 
 
 Hauling-ofC geai", steam or electric. For electric specify voltage. 
 
 Ii'ons, calking, 3 per set. 
 
 Irons, soldering, electric. Specify voltage. 
 
 Knives, cable sheath. 
 
 l.ami)s, alcohol. 
 
 Laini)s, buoy; can be obtained in various sizes. Ship's anchor-lights usually 
 supplied. Specif.v size. 
 
 Lamp frames for attachment to flagstaifs and buoy triixxls. 
 
 Lamp.s, blow. (See "Torches, blow.") 
 
 Lamps, incandescent. Specify voltage and candlepower. Edison sockets will 
 be furnished unless otherwise indicated. Straight filament lamps are supplied 
 for testing room galvanometers. Special lamps for telephoto and Ardois must 
 have voltage and maker's name specified. 
 
 Lanterns, tin. 
 
 Lead, red, pounds. Supplied for preservation of cable gear. Unmixed will 
 be supplied unless otherwise specified. 
 
 Leads, deck, several sizes and kinds of 1. 2. and 3 roller leads. 
 
 Leads, heaving, 12 and 28 pound weights. 
 
 Lead, sounding, for Thompson machine. 
 
 Leather, rigging, sides. Specify thickness and (piality. 
 
 Logs, tafliMil, with propeller and line. 
 
 Liiflvs. Specify length, whlth, and size. 
 
 ;\Iachines, cable, usually classed as "idcU-up." "'pay-out," or combined 
 •• picking-up and paying-out." To be accounted for by name of maker 
 
 -Machines, 1). S., sounding, Sig.sbee. 
 
 Machines, electric, vulcanizing. Specify voltage. 
 
 Mallets, calking. 
 
 Mallets, serving, wood. 
 
 Mallets, serving, iron. 
 
 Mushrooms. (See "Anchor, mushroom.") 
 
 Marline, spikes. 
 
 Needles, sail, dozen. 
 
 Oil, boiled linseed, gallons. 
 
 Oil, engine, barrels. 
 
 Oil, cylinder, barrels. 
 
 (313)
 
 32 Signal Corps Manual No. 3. — Chapter 8. 
 
 Padlocks. Specify make desired and size. Usually unsatisfactory when fur- 
 nished assorted. 
 
 Paint. Specify whether mixed or unmixed. 
 
 Palm.s, sailor's sewing. 
 
 Rope, grapnel, combined wire and manila, breaking strain lo tons ; weight 
 per thousand fathoms, exclusive of httings. 5o4 hundredweight. 
 
 Rope, gi-apnel and buoy, combined wire and manila, breaking strain 13i tons; 
 weight per thousand fathoms, exelusive of fittings. 49* hundredweight. 
 
 Rope, buoy, combined wire and manila, breaking strain 7A tons; weight per 
 thousand fathoms, exclusive of httings. 24 hundi-edweiglit. Specify the length 
 of sections of grapnel and buoy ropes; also that each length l)e equipped with 
 proper fittings. 
 
 Rope, manila, coils. Specify .size, inches (cireumference). Rope s\ipi»liiMl only 
 in units of coil.s. Number of feet in a roW not tixed. Three-strand will be sup- 
 plied unless 4-strand is specitied. 
 
 Rotometers, Elliot (I'evolution counters). 
 
 Scales for T.-B. sounding tubes. 
 
 Sextant. 
 
 Shackles. Specify size whether screw or pin; givc^ s\zo and also length and 
 width, as some types are unsuitalde for u.se with grapnel rope. 
 
 Sheaves. There is such a great variety of sizes and kinds that recpiisitions 
 should clearly specify type and dimensions. 
 
 Si)un yarn. 3 yarn. 
 
 Shots, .sounding. Can be obtained in weights from 40 to 00 pounds. Should 
 be purcha.sed by cable ship, as required. 
 
 Splicing tool. A disk with handles for laying on armor wire. 
 
 Swivels. Can be obtained in various sizes and with various sliaiied liidcs 
 attached. 
 
 Slip-hooks (detaching hooks). Has trigger for releasing buoys. Three sizes — 
 small, medium, and large. 
 
 Tubes, glass, sounding, for Thompson machine, 10 tubes per case. 
 
 Tubes, sounding, Tanner-Blish, for Thompson machine, frosted glass. 
 
 Tube, brass, sounding. To attach to sounding wire and contains the glass 
 tube. 
 
 Tube boxes for T.-B. sounding tubes. 
 
 Tags, cable, linen. 
 
 Telegraphs, special. Refers to pedestal dials completp ; also known as " shij)'s 
 telegraph." !{(>(piisitions for chain or i)ulleys specify exact size, and for the 
 telegrajilis fui'nisii a sketch showing liic lettering desiri'd for the dial. 
 
 ■■i'cleiilioto outfits (Ardois). To bo accounted for by luiniiier. 
 
 'J'hermometers, deei)-sea sounding. These thermometers on being revci-scd 
 when heaving in indicate the b()ttom lemiKM-ature. Negretti iV Zaniltra t,\pc will 
 be stipplied unless otherwi.se indicated. 
 
 'riicniioiiictcr cases. For reversing I licnnonielcr to obtain bottom lenipera- 
 (ure. 
 
 Tliiinldcs. Can he sui)pli('d in great variety of sizes and shapes, (ialvanized 
 iron will be sup|)lied uidess othci'wisc specified. 
 
 Torc-hes, blow. (Jasoiinc type will he rurnished unless otherwise siiecifi(>d. 
 
 Trays, vulcanizing. These are for melting parallin for vtdcanizing Joints. 
 <'an not be purchased in open market. When new one is re(|uired. old one 
 sliouhl he furnished as a sample (o maiiufaclurer. 
 
 Waste, cotton, bales, about 100 pounds per bale. 
 
 CMi)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 33 
 
 Wiro, seiziii.LT. This is :i sofi (!. 1. wire, -to mils in ilijiiiicln-, for serving; aniior 
 of 1>. S. t-altlc. 
 
 Wire, soundinf?, T-stnuHl. fm- Thoniiison luui'hiiif. Su])i(lic<l in U-nKths of 300 
 fathoms. 
 
 Wiiv, deep-sea, .soundinj;, fathoms. This is "No. 11 music wire," approxi- 
 mately 28.5 mils in diameter, breaking strain about 207 pounds. Supplied in 
 sealed tin cans containing 1,000 fathoms of wire. 
 
 Hooks supiilied on cable testing and engineering: Deep-Sea Explorations 
 (Fish Commission edition). Ehvtrical Engineer's INx-ket Book (Foster), Elec- 
 trical Testing for Telegraph Engineers (Young), Submarine ('able I^aying and 
 Kepairing (Wilkinson), Submarine Telegraphs (P>right), Submarine (.'able 
 Testing (Fisher v^ Darby). Electrical Testing (Kent). 
 
 WIKK C.VUT. 
 
 Carts, wire, type L, comph'te (Ihe type I> wire cart, when furnished com- 
 I)lete, is sui)plie(l with the following extra parts: 1 wheel, except in the 
 case of Signal Corps tield companies of the Regular Army, which are sup- 
 plied only with the number authorized by existing orders; 1 paulin ; 1 axle: 
 1' brake bands; bearings for 1 reel, complete; 1 crank, reel; 1 wrench, axle: 
 1 can, oil, steel, pint size; and 1 canvas roll containing the following tools: 
 1 chisel, cold, 6-inch ; 1 screw driver, 5-inch ; 1 screws driver, 10-inch ; 1 ham- 
 mer, claw. Hi ounces; 1 wrench, monkey, 8-inch ; 1 pliers, side cutting, 8-inch ; 
 1 wrench set, S, to fit special bolts on carts; 1 wrench, alligator, S-inch) : 
 Maintenance parts — 
 
 Axle, with nuts and pins. 
 
 Band, brake, complete. 
 
 Bearing, roller, for driving gear. 
 
 Bearings, roller, for reel. 
 
 Block, terminal. 
 
 Bolt and nut, 7A by |, for doubletree, with cotter-pin hole drilled in 
 
 same. 
 Bolt and nut, for tire, 3 by is. 
 Bolt— 
 
 For axle bracket, 7* by |, slotted-head castle nut. 
 For center axle bracket, 4* by §, slotted head castle nut. 
 For countershaft hanger, 7* by i, slotteil-head castle nut. 
 Bolts, for wheel hub. 
 Bolt, hanger, pole prop. 
 Box- 
 Center axle. 
 Outer axle. 
 Bracket— 
 
 For pole prop. 
 Plunger. 
 
 Kod, reel guide, center or side. 
 Brake, reel, with raybestos — 
 Right. 
 Left. 
 Biishing and luit, for doubletree. 
 Bushing, tiber, for reel. 
 Can, oil — 
 
 10-inch, bent spout, copper. 
 Steel, pint size. 
 46581°- 17 21 (315)
 
 34 Signal Corps Manual No. 3. — Chapter 8. 
 
 Carts, wire, type L, complete — Continued. 
 Maintenance parts — Continued. 
 Cap- 
 Hub. 
 
 Roller, antifriction. 
 Chain and ring, for doubletree. 
 Chain, pole prop. 
 Clevis, for commercial reel shaft. 
 Clutch, complete, with gear (33 teeth). 
 Conductor, terminal block. 
 Connector — 
 
 Ground, for wheel (on spoke). 
 
 Inside. 
 
 Outside. 
 Cotter pins — 
 
 For axle. 
 
 For bolt, for axle bracket. 
 Crab, pole. 
 Doubletree. 
 
 Eye, conductor, ternnnal block. 
 Gear — 
 
 Countershaft, with shaft attached (09 teeth). 
 • Driving (66 teeth). 
 
 Reel (30 teeth). 
 Handle, crank. 
 
 Holdback, for pole neck yoke. 
 Hub, wheel. 
 Insulator — 
 
 Block, for inner part of reel. 
 
 Block, for plunger bracket. 
 
 For singletrci". 
 
 Washer, on plunger bracket. 
 Lever — 
 
 Brake, foot. 
 
 Clutch. 
 
 Reel brake, foot. 
 Nut, axle — 
 
 Left. 
 
 Right. 
 
 riiuiiii. 
 
 Tin and ciiaiii. split, for conHucrcial reel shaft. 
 Pin, connecting, for foot lever. 
 Pins, pivot — 
 
 Foot lever. 
 
 Reel brake. 
 I'lunger. 
 
 I'olf. coiiiplctc', including pule pi'op and bracket. 
 Pole (wood only). 
 Prop, pole. 
 
 Raybcstos, facings, for iccl liraUc. 
 Keel, complete, without roller bearing. 
 Ring, contact, for reel. 
 
 (316)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 35 
 
 Carts, wire, type L, complete — Continued. 
 Maintenance parts — Continued. 
 Rod— 
 
 Clutcli connecting. 
 Connecting, brake lever. 
 Reel guide. 
 Roller, antifriction. 
 
 Bearing for. 
 Roll, ltK>l. canvas, complete, with tools. 
 Case, canvas. 
 Chisel, cold, 6-inch. 
 Hammer, claw, 11^ ounces. 
 Pliers, side cutting, 8-inch. 
 Screw driver — 
 5-inch. 
 10-inch. 
 Wrench — 
 
 Alligator. 8-inch. 
 Monkey, 8-inch. 
 
 Set, S, to fit special bolts on carts. 
 Screw — 
 
 For contact ring (R. H. machine. 2-inch, 20-thread, No. 14), per 
 
 gross. 
 Set, and lock nut. for center axle box. 
 Screws for reel gear. 
 Shaft reel, commercial. 
 Shaft rock- 
 Brake lever. 
 Clutch. 
 Singletree. 
 Spring, plunger. 
 Washer, fiber, for reel. 
 Wheel, complete. 
 Wrench, axle. 
 Yoke- 
 Axle, with brake-band hanger. 
 Neck. 
 
 Figures 8-5, S-6, 8-7, 8-8 illustrate cords used with various apparatus sup- 
 plied by the Signal Corps. Figure 8-9 illustrates terminals used In connection 
 with the cords. The number sho\\'n for each cord is the latest number adopteil 
 and should be used in referring to tlie cords. 
 
 (317)
 
 3() 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 (318)
 
 Technicai Equipment Issued by the Signal Corps. — Chapter 8. 
 
 (319)
 
 38 
 
 Signal Corps Manual No. 3.— Chapter 8. 
 
 3 4 
 2 
 
 V 
 
 4 
 
 \ 
 
 (320)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 39 
 
 (321)
 
 40 Signal Corps Manual No. 3. — Chapter 8. 
 
 Made, cfnickd plai&d brass orgcrman silver, except where, shown oUicrwise. 
 
 ■jS 
 
 I' ^' t ls-^_ 
 
 T 
 
 H^Qc 
 
 .(Glazed cotton 
 
 •No 21(028') 5ta:hYire 
 
 2 
 
 "^ ^ 
 
 . Condudur looped 
 
 4 
 
 S 
 
 /]j Conductor wrapped 
 g1 wi/7 //he coppcj- yrirc 
 
 •-t-^5 .TSl 3j ~^^- h 
 
 -J*] |» Na26(.OI6) -M VHa44^0m')drill p] No 22 (.025') 
 
 7a 
 
 8 
 
 , \nrappca nith 
 *~4r\ fineooppcrnire. 
 
 6 
 
 ^tfi— l^^B 
 
 » I. Z" J 
 
 nj~i ^^ 
 
 '513^ 
 
 14 ^^^ 16 
 
 Fig. 8-9.— CORDS, STANDARD, TERMINALS FOR. 
 
 Following' i.s ii liiift' (lt>sci-iplL(in t)l' Held t,'lassos and telcscojios Is.sued by the 
 Si;;iial Cnrps, 
 
 FIELD Ca-ARSER. 
 
 T\ipc .1 " i!)iO". — !\Iafrnlflcntlon npproximately .'VJ and Hi dlamoterR; rialiloaii 
 lypc; ohjcct icii.s. H inches; luterpupillary adjustment; (an heather llnlnli ; tan 
 leallier carryin;: case witli c<)nii»ass; weight of Khiss eoiiiitU^te with case, cord, 
 and straj). '2H ounces. At a distance of l.(MM) yards th»' Meld of view has a diam- 
 eter of 110 yards for the .3i-iH)wer and 70 yards foi' llie r>i-i)ower. Leni;tli of 
 jrlass closed. 4 inclie.s. This j^lass is issue<! as a i)art of tlu> vlsmd slfi'ualln^i' kit 
 to comparncs ol' Coast Artillery, Infantry, and I'liilippine Scouts, and fo t i-oops 
 of Cavalry. I'rice. .$14.0".. 
 
 7'///K' //.— MaKnitic;ilion :ippio\iiiialfly 4i and 0.\ diameters; (Jalilean tyjie ; 
 object lens, 1.? inches; iiitcrpnpillai-y adjustment ; tan leather tinisli ; tan leather 
 earryinj; ease, willi comjiass; weiL'lit of ^dass, com|ilete with case, cord, and 
 strap, .'*1 ounces; len;,dli of ,i,dass closed. 4} inches. .\l a ilistance of 1,000 yjirds 
 
 (322)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 41 
 
 the licld nl' view lias a diameter of 100 yards fur the 4^-povver and 70 yards 
 for llu' (J^iMiwer. This irhiss was foniicrly issued as a part of llic lii-c-cnni rol 
 equil)Uieiil lo i'"icld Ai-| illci-y. I'l-icc, .$17. .10. 
 
 Type V. — A liigh-jyower i)risnialic l)iiio(uhir, the present issue heinji IheTerlux 
 10-power ; object lens, 1, inches; interpui)illary adjustment; common focus lor 
 both barrels, and one barrel ecpiipijed with indeijendent focusinji device; tan 
 leather Ihiish ; sunshade; tan leather carrying case; weight of gla.ss complete 
 with case, cord, and strap, 48 ounces ; length of glass closed, 7| inches. At a 
 distance of 1,000 yards the field of view has a diameter of 70 yards. One glass 
 is issued to the commanding officer of each machine-gun company and machine- 
 gun troop. Price, $39.90. 
 
 Type D. — Prismatic binocular, the present issue being the Busch 8-po\ver 
 " Stellux ;" object lens, f inch; interpui)illary adjustment; conunon focus for 
 both barrels, and one barrel equlpiied with independent focusing device; tan 
 leather finish; tan leather carrying case; weight of glass complete, with case, 
 cord, and strap, 21 ounces ; length of glass closed, 3/e inches. At a distance of 
 1,000 yards the field of view has a diameter of 96 yards. This glass is issued to 
 field companies of tlie Signal Corps, and, on account of its excellence, light 
 weight, and small size is especially suitable for the personal field glass of an 
 officer who desires a high-power field glass. Price, $25.10. 
 
 Type EE. — Prismatic binocular, 6-power ; object lens, It^ inches ; interpupil- 
 lary adjustment ; each barrel equipped with an indeijendent focusing device ; one 
 barrel equipped with a mil scale ; tan leather finish ; sunshade ; tan leather 
 carrying case with compass ; weight of glass complete, with case, cord, and 
 strap, 41 ounces. Length of glass closed, 4ii inclies. At a distance of 1,000 
 yards the field of view has a diameter of 140 yards. This glass is the approved 
 glass for issue to Field Artillery organizations. Price, $33.75. 
 
 Officers in continental United States, Porto Rico, or Ci.ba making application 
 for the purchase of field glasses should address such aiiplication to the Chief 
 Signal Officer of the Ai*my. Officers in the Philippine Islands or China should 
 address applications to the Dei):irtnient Signal Officer, PhiliiDpine Department. 
 
 The Government does not pay transportation charges on articles sold to 
 officers. All applications to the Chief Signal Officer of the Army should be 
 accompanied by post-office money order drawn on Washington post-office or New' 
 York exchange for the amount, payable to " Disbursing officer. Signal Corps, 
 United States Army." Signal Corps form No. 240, in duplicate, should accom- 
 pany all applications. 
 
 Unless otherwise specified, field glasses will be shipped express charges collect, 
 the amount of expi-essage being deitendent on distance glasses are shiiiped. If 
 Insured parcel-i)ost shipnient is desired, the amount necessary for parcel postage 
 should be inclu<led in remittance. Shii)ments of field glasses to points in conti- 
 nental United States, Porto Uico, and Cuba are made from Fort Wood, N. Y., 
 and to points In (Mdna and the PhlUiiplne Islands from Manila, P. I. For rates 
 relative to insured parcel post, see Signal Corps Manual No. 7, revised edition. 
 
 TELESCOPES. 
 
 Type A. — Warner & Swasoy, poro-prism. complete with two eyepieces, powers 
 18 and 24, with alt-aziinutli mounting, folding tripod, and carrying case. 
 
 Type C. — Warner iV: Swasey, tei-restrial, 2-incli prism, two eyeiiieces, 24 and 
 40 power, complete with alt-azimuth mounting, folding tripod, and carrying case. 
 
 Type D. — Sussfeld, Lorsch & Co., Galilean, 33, 35, 40 iwwer, leather covered. 
 with leather caps and strap, six sections, objective, 2-inch : length closed, 9* 
 inches: open, 37 inches; weight, 2 pounds 4 ounces. 
 
 (32.'? J
 
 42 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 Tyi)C E-1S.T. — Warner & Swasey. 18 power, prisni.itic (now desijinated Artil- 
 lery type), in black leather carrying case, with heavy wooden noiifolding tripod 
 (.5 feet 2 inches), one eyepiece; enameled; objective, Ife inches; length closed, 
 12i inches ; open, 13i inches ; weight, telescope, 5 pounds 8 ounces ; leather case, 
 1 pound 8 ounces : tripod. 8 pounds. 
 
 Type G 2-'^ SO. .'lO.r. — Lord Bury type, one eyepiece, 5 sections, black leather 
 covei-ed. with leather caps and strap, without tripcnl ; gun metal. Oblective, 15 
 inches; length closed. 10* inches; open, 33 inches; weight. 2 itounds ;\ ounces; 
 tripod, S pounds. 
 
 FUSES. 
 
 The standard fuses furnished by the Signal Corps in connection with fire 
 control and post telephone systems are illustrated in figure 8-10. 
 
 With post telephone switchboards, iiiicn fuses similar to type 8 are used to 
 protect lines and cord circuits. In some instances the dimensions of these 
 fuses do not correspond with those of any of the standard Signal Corps types 
 shown in figure 8-10. This is due to manufacturers having furnished their 
 standard fuse mountings with the switchboard. 
 
 
 4 
 
 K 
 
 TYPES I &2 
 
 I 
 
 TJIT— 
 
 TYPES 3&4 
 
 Types / and 2 are special, 
 3, 4, 5 and 6 art National 
 EICC Code, Standard. 
 
 - -2-H 
 
 K-i"- 
 
 « 
 
 
 
 W U. STYLE, TELE.GRAPH 
 TYPE 7 
 
 Amperes arc Natl. Dec. Code rating 
 
 
 
 
 
 TYPE 
 
 AMPS 
 
 A- 
 
 B 
 
 C 
 
 D 
 
 E 
 
 F 
 
 G 
 
 S C 1 
 
 3-15 
 
 \k 
 
 
 
 32 
 
 % 
 
 
 
 - 2 
 
 3-15 
 
 \i 
 
 
 
 
 ^ 
 
 
 
 - 3 
 
 0-30 
 
 2 
 
 
 
 %> 
 
 2 
 
 
 
 .. 4 
 
 35-60 
 
 3 
 
 
 
 {1 
 
 ^ 
 
 
 
 •■ 5 
 
 65-100 
 
 A 
 
 
 
 Ire 
 
 5i 
 
 i 
 
 i 
 
 ■■ 6 
 
 110-200 
 
 A\ 
 
 
 
 \% 
 
 7^ 
 
 \i 
 
 I 
 
 TYPES 5&6 
 I AMP ER E M 1 CA Terminals are^ copper 
 
 POSTAL 5TYLE. TELLEPHONE. 
 TYPE 8 
 
 Z-LINK FOR. MASON ARR. 
 TYPE 9 
 
 Fig. 8-10.— FUSES, STANDARD TYPES. 
 
 Those rendering re(|uisi1ions U>r fuses should specify Ihe Signal Corps type 
 and the ampere caiJacity unless the fu.ses desired do iiol correspond with any 
 of the types. In the event of the fuse not being standanl Signal Corps -issue, 
 the api)aratus wilh which it is to be used, name of manufacturer, and, if 
 I)racticMbl<', a sample of fuse slidiild lie furnished. 
 
 (■^24)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 43 
 
 IKON CONDUIT. 
 
 Loricated iron conduit of various sizes is furnislied wliere extra protection 
 for plain lead-covered cable or rul)l>er-covered wire is desired. 
 
 FIBER CONDUIT. 
 
 Thi.s is the standard conduit furnished for underground construction and is 
 usually supplied in o-foot lengths, 8 inches inside diameter, with ends formed 
 for socket joint. Various size.s can be furnished, and conduit with screw 
 socket joints instead of ordinary socket joints will be furnished if satisfactory 
 reason be given. 
 
 KEY, STRAP. 
 
 The standard strap key of the Signal Corps is made in two sizes. They are 
 designated " key, strap, large " and " key, strap, small." The large strap key 
 has a slate base .5f by 3^ inches, and the small strap key has a slate base 4 by 2 
 inches. The principal metal parts of the two keys differ correspondingly 
 in size. 
 
 The upper, lower, and two central contacts are of platinum wire 40 mils 
 diameter, the upper contact being adjustable. Three substantial l)inding posts 
 to which are connected the external circuits connect with the upper, lower, and 
 central contacts, respectively. Referring to figure 8-11, it will be noted that 
 normally the upper contact and one of the central contacts are in electrical 
 contact, and that when the straji is depressed by means of the hard-rubber 
 handle, this contact is broken and the other central contact and lower contact 
 are brought in electrical contact. When the handle is released the ".spring 
 brass " strap restores the contacts to normal position. The two central con- 
 tacts are not insulated from each other. 
 
 Fig. 8-n.— KEY, STRAP, LARGE. 
 
 Part 
 No. 
 
 Name. 
 
 Reference 
 Xo. 
 
 Base, slate, complete 
 
 Yoke, complete 
 
 Yoke, screws for fastening 
 
 Strap 
 
 Strap, hard-rubber handle for 
 
 Contact screw, upper , complete 
 
 Contact screw, upper, lockmg nut for. 
 
 Binding post , complete 
 
 Binding post, nut for 
 
 Binding post , washer for , 
 
 Contact, lower, complete 
 
 (325)
 
 44 Signal Corps Manual No. 3.— Chapter 8. 
 
 INSLTLATING AND SPLICING MATERIALS. 
 
 [This list includes both fire-control aud general-service supplies. Ceneral specification 
 No. 569 covers insulating and splicing material.] 
 
 A1co1k)1 (jrrain. wood, or denatured) per .gallon, as ordered. 
 
 Armalac. per gallon. 
 
 Asbestos, as ordered. 
 
 Asphaltum varnish, per gallon. 
 
 Bandages, cotton, rolls 2 inches wide by 3 yards long. 
 
 Beeswax, yellow, per pound. 
 
 Compound, Chatterton's, per pound. 
 
 Cloths, wiping, Moleskin, 3, 5, and 6 inches square. 
 
 Cloth, Crocus, per quire. 
 
 Cotton, strips, i-inch wide, in rolls 5 inches in diameter. 
 
 Cotton wicking, per ball. 
 
 Instrument lacquer, blue, colorless, or yellow, per bottle. 
 
 Insulatine, per pound, in 1-pound sticks. 
 
 Muslin, strong, unbleached, 2 inches wide, 10-yard rolls. 
 
 Ozite, per gallon, in 1-gallon tin cans. No. 1 or No. 2 grade. 
 
 Paraffin, per pound, flat cakes, melting point not lower than 120° F. 
 
 Paraffin oil, per quart. 
 
 P. & B. paint. No. 2, 1-gallon cans. 
 
 Pasters, gummed, paper for wiped joints, 2 inches wide, 11 or 15 inches long, 
 sanitary, per hundred. 
 
 Rubber, pure, cut sheet, on cambric ; thickness of rul)])er aliout 0.0235 inch, per 
 pound. 
 
 Rubber, pink, 60 per cent pure Para, cut sheet, on cambric ; thickness of rubber 
 about 0.012 inch, per pound. 
 
 Rubber cement, in pint aud half pint cans as ordered, specification para- 
 graph 2 (a). 
 
 Shellac varnish, orange or white, quarts and gallons ; higli grades only. 
 
 Shellac gum, orange, per pound. 
 
 Sandpaper, per quire or dozen sheets, Nos. 0, 1, and 2. 
 
 Sleeves, paper, i or i^ by 3 inches, per 100, 
 
 Sleeves, lead, 1, Ih 2, 2J, or 3 inches diameter, 16-inch pieces or In feet, " O " 
 weight. 
 
 Sleeves, Mclntyre, give size of wire in mils. 
 
 Soft rubber tubing. tV, ^, and J-lncli bore, per foot. 
 
 Solder, i-osin core, H-pound spools, per pound. 
 
 Solder, liiUf and half, in l)ars, i)er i)oun(i (.W parts tin, 50 parts lead). 
 
 Solder, i)liiml)ei-'s wiping, in Ingots, per pound (40 i)ar1s tin, (!0 parts lend), 
 
 Stearine. in :l-pound metal cans. 
 
 Tape, friction, f inch wide, ^-pound rolls, per pound. In tin boxes. 
 
 'rape, okonite, J-i)ound rolls, per pound, in pastel)oard l)(»xes. 
 
 'I'wiiic, lacing, 1-pound l)alls, Bai'bour's "Open Hand" brand, 12 strand. 
 
 INSl 1,AIIN(; COMI'orNDS. 
 
 Tn f)rder that confusion may l)e avoide<l concerning (he use of tlie various 
 insulating compounds wliicli are ordered, tlie following should be noted : 
 
 'I'lie c(»mpounds supplied are: (Miallerton's comitound (first (piality), in- 
 sulatine, gyite, ozite, jiarallin. 
 
 (326)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 45 
 
 ClHiltcrl())i'ft cnvi pound. — Chatterton's coinpnuiid is ;i liij^li-class insulator fost- 
 in,u $1 per pound and slioidd be used only in scalin;^ ends of cable wliere they 
 are exposed to storage-battery fumes or in similar work wtiere a liigh-quality 
 insulator is required. 
 
 Tnsulntinr. — Insulatine is not a liigli-quality insulator, and it is intended for 
 use in sealing outlet boxes where a wall of rubl)er exists between the insulatine 
 and the conductor. It should never be used for insulating purposes only, and 
 is depended on more for its sealing qualities than for insulation. Tiiis material 
 is comparatively cheap, costing about 12 cents per pound. 
 
 Gyite. — Is a better grade than insulatine, but not as good as ozite. 
 
 Ozitc. — Ozite is used for sealing potheads in paper cable work. It may also 
 be used for sealing the ends of rubber cable. 
 
 No. 1 ozite is hard. No. 2 is medium soft, and No. 3 is soft, at approximately 
 60° F. In ordering state the purpose for whicli the material is d(>sired and the 
 conditions as to temperature. 
 
 Paraffin. — Paratfln is intended for use in boiling out splices in paper insula- 
 tion cable and in drying tlie ends. It should never be used in pothead work or 
 for sealing purposes. 
 
 LINK (ONSTIUrCTION MATKRIALS. 
 
 I'riiis lisl inchul.'s both tire-control and ironcTal-scrvico supplies.] 
 
 Anchors, guy, D. & T., S-incli. 
 
 Anchors, star, Ig-inch, No. 10. 
 
 Anchors, star, §-inch, composition. 
 
 Anchors, expansion, i-inch, composition. 
 
 Anchors, guy, Matthews, 6-inch or S-incli, willi rods. 
 
 Arresters, " Cook " : 
 
 Can top, type M-8, unfused. 
 
 Can top, type S-8, fused. 
 Arresters, Mason's Standard, wiili or without fust^s. 
 
 Arre.sters, "Sterling," in strips of ."i or K) pair, fused, with carbon arresters. 
 Brackets, oak. 
 Bolts, cross-arm, diameter |-inch ; suiiplied in six lengths: 1(), li^, 14, 16, 18, 
 
 and 20 inches. 
 Bolts for cross-arm braces, carriage, i indi by 4 inches long. 
 Bolts, double-arm (diameter i inch; lengtli, IL', 14, 16, or IS inches). 
 Boxes, junction, 3-way. 
 Boxes, telephone, outlet, for rifle ranges. 
 Boxes, telephone, portable, for rifle ranges. 
 Braces, cross-arm, pairs. 
 Brackets, iron, for lance-pole insulators. 
 Cable, aerial, lead-covered. (Sec table of cables.) 
 (^able, telephone, switchboard, 20-pair. 
 Clamps, strand, 2-bolt, for j-inch strand. 
 Clamps, strand, 3-bolt, for §-inch strand. 
 Clips, cable, marline. 
 Clips, Crosby. 
 Cleats, cross-arm ( wood ) . 
 Cleats, porcelain : 
 
 2-wire. 
 
 .3-wire. 
 
 1-wire. 
 
 New England telephdiic cleat with car.
 
 46 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 Conform aOict(/ tot/ro^,na i 
 
 Fig. 8-1 2.- LINE CONSTRUCTION MATERIAL. 
 
 (828)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 47 
 
 Mo//eab/e /ron orMi/dSiee/ 
 
 Fig. 8-13.— LINE CONSTRUCTION MATERIAL. MESSENGER SUPPORT. 
 
 (3:^9)
 
 48 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 Couiluit. loricated or elect rochu-t. A to 2 iuelie.s. with couplings and elbows. 
 
 Conduit, bituminized fiber. B-incli. 
 
 Conduit elbows. State kind and size. 
 
 Conduit couplings. State kintl and size. 
 
 Cross arms, iron pole. 
 
 Cross arms, wood (state number of pins), bored for li -inch pins: 
 
 Regular telephone size, 2^ by 3i inches. 
 
 Heavy telephone size, 3^ by 4i inches. 
 
 Dhncnsions of stfunhird hcitvij vroaa (tr)iis. 
 
 Length. 
 
 Number 
 of pins. 
 
 Pin spacing. 
 
 Ends. 
 
 Sides. 
 
 Centers. 
 
 Feel, 
 i 
 i 
 ti 
 
 s 
 10 
 
 2 
 4 
 6 
 8 
 10 
 
 4 
 4 
 4 
 4 
 4 
 
 
 2.S 
 16 
 16 
 16 
 16 
 
 12 
 12 
 12 
 
 12 
 
 L'orniing strips. 
 
 Fu.ses. 
 
 Hangers, cable, marline. 
 
 Hangers, cable, Locke, 2-inch. 
 
 House line, liemp. 
 
 Insulators, pigtail, galvanized. 
 
 Insulators, pony, gla.ss (No. 11, double groove). 
 
 Insulators, lance pole, pigtail, hard rubber or molded mica. 
 
 In.sulators, lance pole, clamp, hard rubl)er or molded mica. 
 
 Insulators, strain, P. and S. 
 
 Insulators, porcelain, standard knobs, as follows: 
 
 No. 4 (diameter, li inches; length, li^ inches). 
 
 No. 5 (diameter, 1 inch; length. 1^ inches). 
 
 No. 6 (diameter, ii inch; length, | inch). 
 
 No. 11 (diameter, H inches; length, Ig inch). 
 Insulators, tree, Gem or Victor. 
 Molding signs. 
 
 Molding, type A (two i by i inch grooves). 
 .Molding, type IJ (three A by i iiw li grooves). 
 Molding, type C (two M by i inch grooves). 
 Nails, 8d. bntfonlM-ad. 
 Ozite. 
 
 Paint, .Mogul, iircscrvalixc. gallons. 
 Paraflin. 
 
 I'ilii'. iron. I'-inrli. :',-iii(li, g;il\iini/.ci|. per loor. 
 Pins, insulator, iM-inch cross ;irni. 
 Plug.s, Insulator for iron iiolcs. 
 
 Poles, steel, telegrai)h, 20 feet long; wcigiii, S(i pounds. 
 Poles, lance, with tip, 14 feet long: wfiglit, s ixtund.s. 
 Poles, wooden. 
 Pole steps. 
 
 cy.m
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 
 Desired dimensions of icood poles. 
 
 49 
 
 
 Circumference in inches— 
 
 For light line. 
 
 For heavy line. 
 
 Length. 
 
 
 
 
 At 6 feet 
 
 
 At 6 feet 
 
 
 At top. 
 
 from 
 butt. 
 
 At top. 
 
 from 
 butt. 
 
 Feel. 
 
 
 
 
 
 20 
 
 1(1 
 
 24 
 
 16 
 
 25 
 
 25 
 
 20 
 
 30 
 
 22 
 
 32 
 
 30 
 
 20 
 
 33 
 
 22 
 
 36 
 
 35 
 
 20 
 
 36 
 
 22 
 
 40 
 
 40 
 
 20 
 
 40 
 
 22 
 
 43 
 
 45 
 
 20 
 
 43 
 
 22 
 
 ■ 47 
 
 50 
 
 20 
 
 46 
 
 22 
 
 .50 
 
 00 
 
 20 
 
 49 
 
 22 
 
 5:} 
 
 60 
 
 20 
 
 52 
 
 22 
 
 56 
 
 Ring.^, bridle, i-incli ; li-incli; ll-incli; or 3-inch. 
 Rods, guy, I by 60 inclies, 
 Rods, ground. 
 Sandpaper, standard. 
 Screws, state whetlier — 
 
 Brass or iron. 
 
 Maciiine or wo(k1. 
 
 Lengtli. 
 
 Flathead or roundiiead. 
 
 Commercial type number. 
 Screws, lag, state size. 
 Screws, lag, fetter drive. 
 Seats, pole. 
 
 Sumniaiy of parts : 
 
 One angle-iron framework. 
 
 Two braces. 
 
 Two three-eighths (|) inch bolts. 
 
 Three one-quarter (i) inch stove bolts. 
 
 Four one-half (*) inch lag screws. 
 
 One wooden seat. 
 Sleeves, lead — order by inside diameter. 
 Sleeves, paper, A inch by 3 inches. 
 Sleeves. Mclntyre — state diameter of wire in mils. 
 Solder, half-and-half, in bars. 
 
 Solder, plumber's wiping, in o-pound ingots, 40 per cent tin. 
 Staples, d. p., " Blake," No. 3. insulated. §-inch. 
 Strand messenger, ^-inch to f-inch. 
 
 Properties of stnnid. 
 
 Diameter. 
 
 Inch. 
 
 I 
 
 i 
 
 Diameter 
 
 of strands 
 
 in mils. 
 
 Tensile 
 strength. 
 
 162 
 120 
 114 
 72 
 
 57 
 
 Pound.t. 
 8,320 
 4,700 
 3,300 
 1,750 
 1,000 
 
 46581°— It- 
 
 (331)
 
 50 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 Strand, guy. i-ineh. 
 
 Supports, cross-arm (for attaching wood arms to iron poles). 
 
 Supports, messenger. 
 
 Tacks, " Milonite." 
 
 Tapes. (See Insulating material.) 
 
 Thimbles, guy, for :|-inch and §-inch strand. 
 
 Tags, cable. 
 
 Terminal, cable pole. (See Arresters.) 
 
 Tubes, porcelain : 
 
 Diameter of bore, rs inch ; length, li inches. 
 
 Diameter of bore, H inch ; length. 3 inches and S inches. 
 First-class wood poles should not have a sweep greater than as indicated in 
 the following table, the sweep to be measured between the 5-foot mark and 
 the top of the pole : 
 
 20-foot pole, sweep not more than 2 inches. 
 
 2.5-foot pole, sweep not more than 3 inches. 
 
 30-foot pole, sweep not more than 5 inches. 
 
 35-foot pole, sweep not more than 6 inches. 
 
 40-foot pole, sweep not more than 6 inches. 
 
 45-foot pole, sweep not more than 7 inches. 
 
 50-foot pole, sweep not more than 7 inches. 
 Guy stubs and anehor logs. — The timber used for guy stubs and anchor logs 
 shall correspond in all respects with that specified for poles. Anchor logs shall 
 not be less than 24 inches in circumference nor less than 4 feet in length. 
 Guy stubs shall not be less than 22 inches in circumference. 
 The timbers to be used for pole braces shall be of the same quality as that 
 specified for poles. No braces shall be less than 18 inches in circumference at 
 smaller end. 
 
 Cedar poles. 
 
 Size of pole. 
 
 
 
 
 
 Estimated 
 vveiglit of 
 
 Number of 
 poles per 
 
 
 
 Top 
 diam. 
 
 Leni,'lh. 
 
 eacb. 
 
 carload. 
 
 Irwhrs. 
 
 Feet. 
 
 Poundi^. 
 
 
 4 
 
 20 
 
 100 
 
 210 to 420 
 
 .5 
 
 20 
 
 130 
 
 1S5 to 325 
 
 
 
 20 
 
 175 
 
 130 to 250 
 
 7 
 
 20 
 
 210 
 
 11510 200 
 
 1 
 
 25 
 
 150 
 
 Kioto 2S0 
 
 5 
 
 25 
 
 200 
 
 120 to 210 
 
 5J 
 
 25 
 
 225 
 
 110 to 190 
 
 6 
 
 25 
 
 250 
 
 KK)((i 170 
 
 7 
 
 25 
 
 350 
 
 70 to 130 
 
 H 
 
 25 
 
 400 
 
 W to 105 
 
 f, 
 
 30 
 
 275 
 
 SO to 155 
 
 i; 
 
 30 
 
 350 
 
 70 to 120 
 
 7 
 
 30 
 
 450 
 
 .55 to 95 
 
 8 
 
 30 
 
 550 
 
 45 to SO 
 
 (i 
 
 35 
 
 450 
 
 70 to no 
 
 7 
 
 35 
 
 600 
 
 50 to 70 
 
 8 
 
 35 
 
 750 
 
 40 to (10 
 
 6 
 
 40 
 
 625 
 
 50 to (15 
 
 7 
 
 40 
 
 SOO 
 
 40 to 55 
 
 s 
 
 40 
 
 975 
 
 30 to 45 
 
 (332)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 
 Cedar poles. 
 
 51 
 
 Size of pole. 
 
 Estimate'l 
 
 weight of 
 
 each. 
 
 Number of 
 
 poles per 
 
 load (2 cars). 
 
 Top 
 diam. 
 
 Length. 
 
 Inches. 
 7 
 
 S 
 
 s 
 
 s 
 
 Feet. 
 45 
 45 
 50 
 50 
 55 
 55 
 60 
 65 
 
 Pourtd.t. 
 1,000 
 1,150 
 1,250 
 1,350 
 1,550 
 1,750 
 2,000 
 2,700 
 
 60 to 70 
 52 to 58 
 48 to 55 
 44 to 48 
 39 to 42 
 34 to 37 
 30 to 33 
 23 to 25 
 
 MARKING HAMMERS. 
 
 Wlienevpr insitoctions of f'onsi(lera])le quantities of poles, wooden conduits, 
 cross arms, or otlier rouRli woodwork are required, the inspector will be sup- 
 plied with a niarkinjr hammer showing the crossed flags of the Signal Corps 
 and a letter indicating the office from w^hich the inspection was made. 
 
 These marking hammers will be supplied by Department Signal Officer or 
 signal otfice, Washington, when needed. 
 
 LINE CONSTRUCTION TOOLS. 
 
 [Standard construction tools as described in specification No. 360.] 
 
 Adz. house carpenter's full head, 4-inch blade, Fayette R. Plumb's or American 
 
 Axe & Tool Co. 
 Ax. hand (specified as broad hatchets), o-inch blade. Plumb's. Germantown. or 
 
 Keen Kutter. • 
 
 Axes, handles for. to be hickory, clear, straight-grained. 
 Ax. lineman's 5-pound, long-handle, all steel, Plumb's. Germantown, or Keen 
 
 Kutter. 
 Bags, lineman's best canvas, with leather bottom, 20-in<li. letters " U. S. S. C," 
 
 1 inch high, in indelible ink stenciled thereon, W. E. No. 15201. 
 Bars : 
 
 Crow, wedge i)oint, 17 p(miids, best tool steel. 
 
 Digging, 1 inch round. S feet long, weight 17 pounds, and Is in<-hos romnl, 
 
 8 feet long, weight 2S pounds; both to be of solid steel. 
 Di.uging and tamping, 1 inch round tool steel. 7 feet long, weight 1!) pounds; 
 
 1 inch octagonal tool steel, 8 feet long, weight 2.") poiuids. 
 Digging (electric spud), steel tubing, with cast blade and t.iniix'r. 
 Belts, lineman's, for tools, with loops, rings, and safety strait, as iii-r drawing, 
 
 paragraph 3 (ft). 
 Bits: 
 
 Auger, Irwin, sizes 1-inch, i^^-incli. s-i'i<'l>. s-incli, s-inch. 4-iiuli. all S iuclies 
 
 long. 
 ExpaTision. s inch to '.i inches, C. E. .Tennings's. 
 Pole, Irwin, 12 inches by § inch, and 16 inches by | inch. 
 Blades, hack-saw, 10-inch, Milford. 
 
 (333)
 
 52 Signal Corps Manual No. 3. ^Chapter 8. 
 
 Blocks : 
 
 Pulley, Star braiul. Boston <& Lockport Block Co., galvanized malleable 
 iron, as follows (all blocks with one hook and one becket) : Single or 
 double. 3-incb block for §-iuch rope. 15-inch sheave ; double or triple, 
 6-inch block for |-inch rope, Si-inch sheave; double or triple, 10-inch 
 block. 6:J-inch sheave. 
 
 Roller for cable. 
 Braces, ratchet, 8-inch sweep, IMillers Falls Co. or Bai'ber's Inijiroved. 
 Buffalo grip with pullej's No. 1 size, W. E. Co., for wires up to No. 1G2 mils 
 
 diameter. 
 Chain, cow, 4 feet, with rings. 
 Chisels, cold, f-inch to 1-inch, tool steel. 
 Chisels : 
 
 Socket-framing, 1^ inches to 2 inches. 
 
 Socket-framing, handles for, ring-topped, best ([uality hickory. 
 Clamps, combination splicing, for wires 04 to 204 mils diameter, iron ; for 04 to 
 
 128 mils diameter, copper (for Mclntyre coiuiecters). 
 Climbers : 
 
 Klein's Eastern, 16 inches and IS inches, with straps and pads. 
 
 Straps and pads, for Klein's Eastern, to be of best (piality leathei'. 
 Coppers : 
 
 Soldering, with handles, 1 pound. 2 pounds, and 4 pounds. 
 
 Soldering, handles for, with ring fei-rules. 
 Cord, Sampson spot, waterproof, three-eiglitlis (§) inch diameter, in coils (»f 
 
 100 feet. 
 Drill, rock, made of best tool steel, large and small sizes. 
 Files : 
 
 Nicholson or Disston ; dentist tile; .'j-incli triangular; 8-inch round; Hat; 
 bastard ; half-round ; S-inch. 
 
 Handles for, wood. 
 Frames, hack-saw, Star No. 10. 
 Furnace, gasoline, with 0-inch pot and S-inch ladle, Whilte's or Clayton & 
 
 Lambert's No. 10, galvanized tank. 
 Globes, plain or ruby. 
 Hammers : 
 
 Claw, 18-ounce, Maydole, Atha, or Keen Kutter. 
 
 Machinists, 2-pound, Maydole. Atha, or Keen Kutter. 
 
 And hatchets, handles for. best grade Inckory. 
 Handles with tools. No. ."). Millers Fjills Co. 
 Hooks : 
 
 Cant, 4-foot, with handl(>, Dickie Tool Co. 
 
 Carrying, 4-foot ban<IIe, Dickie Tool Co. 
 Jack strap. comj)lete, with hook an<l No. 1 P.ulTalo grip, W. E. Catalogue, 
 
 No. 2667. 
 Kit, tool, inspector's ]»ocket. 
 Knives : 
 
 Draw, lelcgi'iiph pattern. 12-inch and 14-inch bl:id(\ .lennings'. 
 
 Electrician's, Empire Knife Co., No. 1018. 
 Lanterns, excavation, ruby gl(»b('. Dietz, or Ham's tubular. 
 Pick liandles. straight-grained hickory. :{(! inches long. 
 Picks, Iron City or Klein & Logan's, 7 pounds to S i)onnds. 
 Pike, guarded or raising, 14-foot. 
 
 (:5:;4)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. .53 
 
 Pliers : 
 
 LineniaiTs, O-incIi sidi- ciiltin;,'. V. 1). F. i^ T. i'o.. Sn. ."ifj. or I'. S. & W., 
 No. 40. 
 
 Lineman's, .S-indi side cull in;;, L'. 1). i<\ ifc T. Co., No. .'"lO. or I'. S. & W., 
 No. 40. 
 
 6-inch diagonal, F. Unstroni. 
 Poles, pike, 12-foot. lO-foot, and IS-foot, 2 inches in dianicler, strai^lit liv(> ash, 
 
 or white or yellow iiiiic lo suit locality. 
 Pole support : 
 
 Jenny, 7-foot. 
 
 Mule, 6-foot. 
 Post-hole augers, 12-inch, 5 feet lonu'. Hercules. 
 Post-hole diggers, O-foot or 7-foot handles. 
 Reels : 
 
 Pay-out, with or without slioulder straps, as ordered. 
 
 Take-up. 
 Reel jacks: 
 
 Klein's or King's, for 2J-inch shaft, capacity 10 tons ])er pair. 
 
 Axes for, steel, 1-inch, 1 J-inch, 2-inch, and 2i-indi. 
 Rope, pure manila hemp : 
 
 |-inch, in coils of 1.000 feet. 
 
 2-inch, in coils of 1,000 feet. 
 
 §-inch, in coils of 500 feet. 
 
 f-inch, in coils of 000 feet. 
 
 1-inch, in coils of 500 feet. 
 Rules : 
 
 2-foot, folding, boxwood, brass bound, No. 62^, C. S. Co. 
 
 Zigzag, 4-foot, Stanley liule & Level Go. 
 Saws : 
 
 Crosscut, Disston's, .5-foot, willi handles. 
 
 Hand, 2G-inch, No. 7. .S-])oint. Disston's. 
 
 Rip, 2G-inch, 5^-point, Disston's. 
 Screw drivers. Perfect, .3 inches, 4 inches, inches, and 12 inches. 
 Shovels : 
 
 6-foot and 8-foot handles, with IS-lnch straps. Ames's or (Jriflith's. 
 
 Handles for. 
 Spades : 
 
 Grading, roxmd and square pointed. D handles. 
 
 Handles for. 
 Spoons, 6-foot and S-foot bundles. IS-inch sti-ap. Ames's or Oritllth's, 
 Straps, safety, for lineman's belts. 
 
 Tape line, metallic, Lufkin, 100 feet and 50 feet. In feet and inches, leather case. 
 Torches, blow, hot blast, Clayton & Lamlierfs, No. P>2. 
 Tree trimmers : 
 
 Large size, without saws. 
 
 Large size, with saws. 
 
 Handles for, IS feet, with ferrule joint. 
 Wrench, combination lag screw and init, Klein's. 
 Wrenches, monkey, Coe's. 10-inch and 12-inch, or P. S. & W., No. 100. 
 
 Following is a brief descrii)tion and enumeration of contents of the various 
 instrument and tool kits which have been devised by the Signal Corps for 
 
 (335)
 
 54 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 issue to construction parties, inspectors and for use in maintenance of elec- 
 trical systems. It is specified that all tools furnished shall be of the best of 
 their kind and type. 
 
 ELECTKICAL INSTRUMENT CASE. 
 
 [This electrical case is manufactured under specification No. 145.] 
 
 The electrical instrument case is issued wherever an extensive cable system 
 is installed or whenever exhaustive and accurate tests of cable aiv desii-cd. 
 The case is of oak, reinforced at corners with metal. Fiiiure S-14 illustrates 
 this case. For description and use of instruments containtMl in the electrical 
 instrument case, see chapter 4 of this IManual. 
 
 CtlXTENTS. 
 
 1 insidation and capacity test set, consisting of the following: 
 
 1 portable galvanometer «»f the D'Arsonval typts coiil'onniiig to drawing 
 
 No. nsb. 
 
 1 telescope and scale for above galvanometer. 
 
 1 100,000-ohm box. 
 
 1 combined shunt and switch. 
 
 ] condenser set. 
 
 1 ohnnneter. 
 
 1 iripod (external to case). 
 
 1 service testing batlery, drawing No. 109, specification No. ISH. 
 
 1 micrometei' calijter, V>. tSc S.. NH. S, withoiil rntcliet slop, with morocco- 
 carrying case. 
 
 1 ins])ector's ])ock('t tool kit, as jicr drawing \o. 1104, specilicat ion No. ISO. 
 
 1 testing telei)hone, to be furnished by tlic Tnited States Signal ('ori)S, 
 space to Ite ]>rovided by the contractoi', as per drawing. 
 
 ] space for foi-ms and rei>orts. 
 
 1 si»ace for books. 
 
 .MI.S(HI,I,.\NEOI-S PARTS AND SITPLIES. 
 
 1 galvanometer coil and mii-ror. 
 4 round-head plugs. 
 
 6 lower suspensions. 
 6 upi)er suspensions. 
 
 2 milled-head screws. 
 ] piece felt. 
 
 4 screws for glass. 
 ] ohnnneter card. 
 ] jtiece chamois. 
 1 bottle vaseline. 
 1 bottle tyjH'writer f>ll. 
 
 ](HI feet No. 22 bare copper wire 
 
 ]00 feet advance wire, No. 28. 
 
 25 feet No. 22 manganin wire. 
 
 3.50 feet No. 34 manganin wire., 
 
 300 feet No. 40 manganin wir(>. 
 
 GO feet No. 28 manganin wire 
 
 1 glass window. 
 
 4 paper scales. 
 
 feet battery cord. 
 
 10 feet okonite wire. 
 
 N ounces solder. 
 
 REPAIR KIT. 
 
 Tlic r('i>air kit <'ontains the following instruments: 
 
 ."' lower susjiensions for galvanometer. 
 4 npiK-r susi»snions for galvanomet«'r. 
 
 1 nickel-plated screw driver. 
 
 2 jiairs tweezers, nickeled. 
 
 (.^.".0)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 55 
 
 ilKCIIANICS' TOOL CHKSTS. 
 
 [These chests are manufactured under specification Xo. 562.] 
 
 Mechanics' tool chests are for issue to Signal Corps field companies for use 
 in connection with the repair of apparatus. There are two chests, differing 
 slightly in dimensions and equipment, and are designated " Mechanic's tool chest 
 No. 1 " and " Mechanic's tool chest No. 2." They are constructed of heavy, 
 
 straight-graiiuHl oak, substantially reinforced at corners with metal corner 
 braces. 
 
 Fig. 8-14.— CASE, ELECTRICAL INSTRUMENT. 
 
 Name plate. 
 
 For Chest No. 1— 
 
 Mechanic's Tool Chest, 
 
 Number One, 
 
 Field Company, 
 
 Signal Corps, U. S. Army. 
 
 Serial No. . 
 
 For Chest No. 2— 
 
 Mechanic's Tool Chest, 
 
 Number Two, 
 
 Field Company, 
 
 Signal Corps, U. S. Army. 
 
 Serial No. . 
 
 The chests are fitted with Corbin padlock No. 2882, or equal, no two of which 
 have keys alike, except the two locks for No. 2 chest, which shall be opened by 
 the same key. A duplicate set of keys is furnished for each lock. 
 
 With the exception of items marked (*) each tool is stamped with the numlier 
 assigned to it in the following list. 
 
 The chests are equipped and tools distributed as follows: 
 
 Chest No. 1. 
 
 Lid. 
 
 1. 1 frame, hack-saw, Star, No. 10. 
 
 (337)
 
 56 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 Top of chest. 
 
 2. 1 pliers, side-cuttinfr, 6 inches. U. D. F. & T. Co., No. 50. or P. S. & W., 
 
 No. 40. 
 
 3. 1 pliers, diagonal, 6 inches, F. Linstrom, No. 842. 
 
 4. 1 pliers, long-nose, 5* inches, U. D. F. & T. Co., No. 654. 
 
 5. 1 shears, metal, AV. H. Compton, " Reliance," No. 10. 
 
 6. 1 hammer, riveting, 4 ounces, Maydole, cast steel. 
 
 7. 1 oil can, bicycle or pocket type, 24 inches diameter, 3 -inch thick, curved, 
 
 spout with screw cap. 
 
 8. 1 drill, hand, Goodell Pratt Co., No. 54. 
 
 9. 1 vise, adjustable jaw, swivel base, 2-inch jaws. No. 37, Prentiss. 
 10. 1 screw-driver set, Yankee, No. 100, 
 
 *11. 1 drills, twist, set of 60, straight shank, ]\Iorse, Nos. 1 to 60. 
 
 Fig. 8-15.— CHEST, TOOL. MECHANICS NO. 2. 
 
 End of (licit. 
 
 12. 1 torch, gasolene, Clayton & Lanilicrt. No. IV2. 
 
 13. 1 grinder, hand, with 1 hy 5 indi Norton gi-inding wln'cl, .\iiierican, No. 2. 
 
 Draiocr Xo. J. 
 
 14. 1 screw-plate .set. Little (Jiant, No. A A 4. 
 
 15. 1 square, conil)lnation, 0-inch blade without cciilcr licad. Alliol, No. 4. 
 
 16. 1 oilstone, mounted, 8-inch .soft, Arkansas, Pike's. 
 
 17. 1 screw driver, machinist's, swivel head, 5 inclics. .-j^-incli blade, I'ii-iiich 
 
 handle, Syracuse. 
 IS. 1 chisel, cold, ^-incli, (I inches hnig, "Diamond I'dge." 
 19. 2 center punches, straiglit-shanlc, Syracuse, No. 16. 
 *20. 4 file.s, 4-lnch, round. 
 *21. 4 tiles, 4-incli, square. 
 *22. 6 liles, O-inch. rounil. 
 
 (338)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 57 
 
 23. 1 handle, file, malleable iron. 1. X. L. 
 
 24. 1 iron, soldering, i pound. 
 
 25. 1 iron, soldering, 1* pounds. 
 
 Draicer No. 2. 
 
 26. 6 files, 8-inch, flat, bastard, "Arcade U. S. A." 
 
 27. 1 file cleaner. Col ton's No. 10 or similar. 
 
 *28. 2 hack-saw blades, dozen, 12 inches, Disston's. 
 
 . Chest No. 2. 
 Cover. 
 
 1. 1 saw, hand, 10-point, Disston's, 26-inch. 
 
 2. 1 saw, rip, 6-point. Disston's, 28-inch. 
 
 3. 1 square, 24-inch, Russell iK: Erwin, No. 14 (short end cut to 14 inches). 
 
 4. 1 rule, Stanley. No. 104. 
 
 Top of chest. 
 
 5. 1 wrench, monkey, l.'i-inch. 1'. S. i^ W. 
 
 6. 1 wrench, monkey, 6-inch. P. S. & W. 
 
 7. 1 wrench, Stillson, 14-incli. 
 
 8. 1 screw driver, 7-inch, " Champion." 
 
 9. 1 screw driver, 5-inch, " Champion." 
 
 10. 1 nail puller, " Little Giant." 
 
 11. 1 knife, draw, 8-inch, A. J. Wilkinson & Co., Boston, fohlinc: type. 
 
 12. 1 hannner, riveting, 8-ounce, Maydole, cast steel. 
 
 13. 1 hammer, claw, Maydole, Hi. 
 
 14. 1 tape, steel, 100-foot, Lufkin's "The Itival." 
 
 15. 1 brace, 10-inch, Millers Falls Co. 
 
 16. 1 chisel, set of 5, If, li, |, f, and ^ inches. .Tennings's No. 70. 
 
 17. 1 calipers, pair, 4-inch. 
 
 18. 1 dividers, pair. 6-inch, V. S. tJc W.. wing or eciual. 
 
 Loin r (Iraircr. 
 
 10. 1 screw plate, .set. Conant iV: Donaldson ( 'o.'s "Reliable." No. 3.^. 
 
 20. 1 plane, jack. 2-inch bit, Stanley. 
 
 21. 1 plane, block, Ig-inch bit, Stanley. 
 
 22. 1 oilstone. Pike, .soft Arkansas, o-inch. mounted. 
 
 23. 1 saw, set, Morrill's, No. 11. 
 
 I'pper draicer. 
 
 24. 1 file holder. I. X. I.., malleable iron. 
 
 25. 1 file cleaner, Colton's No. 10, or similar, metal back. 
 
 '■26. 1 drill, twist, bit stock, set of 9, 3 each of ^, t^, and i inch diameter. 
 *27. 1 files, set of 14, Nicholson, three 8-incli, half-round, smooth ; three 8-inch. 
 
 half-round bastard ; two 8-inch, flat bastard ; six 6-inch saw files. 
 *28. 1 bits, set of 14; 13 Irwin's i-inch to 1-inch by i^-inch. and 1 bit, C. E. 
 
 Jennings's expansive, J to 3 inches. 
 The last three items will be incased in canvas rolls. Theso canvas rolls are 
 to be neatly and strongly made of 10-ounce Idiaki canvas, leather bound, with 
 flap and 1-inch strap and buckle. The roll for the twist drills shall be 19 
 
 (339)
 
 58 Signal Corps Manual No. 3. — Chapter 8. 
 
 inches long when opened out. The roll for the files shall be 27 inches long 
 when opened out. The roll for the bits shall be 36 inches long and shall have 
 a small leather pocket securely sewed on the inside for the extra cutters of the 
 expansive bit. 
 29. 1 hatchet, half, with handle, Germantown No. 2, thin blade. 
 
 AEROPLANE TOOL CHEST. 
 
 [These chests are luanufactiire'l under specification Xo. .^62.] 
 
 The aeroplane tool chest is for issue to aeronautical companies or detach- 
 ments detailed in connection with aeronautical woi-k. The chests are identical 
 with mechanic's tool chest No. 2, except that certain partitions are omitted. 
 
 Name plate. 
 
 Aeroplane Tool Chest. 
 
 Signal Corps, U. S. Army. 
 
 Serial No. . 
 
 contk;xts. 
 Colder. 
 
 1. 1 saw, hand, lO-point, Disston's, 2G-inch. 
 
 2. 1 hammer, riveting, S-ounce, Maydole. 
 
 3. 1 combination square, lievel and level, 12-iiich, Athol. 
 
 4. 1 rule, Stanley, No. 104. 
 
 5. 1 hack saw frame. Millers Falls C(»., No. 6. 
 
 6. 1 dividers, pair, (i-iucli, I'. S, & W. 
 
 Top II f Clteat. 
 
 7. 1 wrench, Stillson, 14-inch. 
 
 8. 1 screw driver, 7-incli, Perfect. 
 
 9. 1 screw driver, 5-inch, Perfect. 
 
 10. 1 nail puUei-, Little Giant. 
 
 11. 1 knife, draw, 8-inch, A. J. Wilkinson & Co., Boston, folding type. 
 
 12. 1 hammer, tinsmith, 1-pound, Atha. 
 
 13. 1 hammer, claw, Maydole. 
 
 14. 1 tape, 100-foot, steel, Lufkins " The Rival." 
 
 15. 1 brace, 10-inch, Millers Falls Co., No. 32. 
 
 16. 1 iron, soldering, 14-pounds; 1 iron, soldering, jeweler's. No. 1; 2 center 
 
 punches, 4-inch, Syracuse; 24 blades, hack saw, 10-inch, coarse. Star; 
 12 blades, hack saw, 10-inch, Star, No. 20; 1 chisel, cold, 4-incli, Village 
 Blacksmith; 1 chisel, cold, i-inch, Village Blacksmith. 
 
 17. 1 screw driver, 8-inch, Perfect. 
 
 18. 1 calipers, double, 6-inch, Starrett, No. 44. 
 10. 1 wrench, monkey, 6-inch, P. S. & W. 
 
 lljiixr Draivcr. 
 
 20. 1 bit, (). Vj. .Icnning's expansive, I iricli to ',i inch, with leat^iiM* pocket for 
 
 cutter. 
 
 21. 1 pliers, round nose, 6-incii. I'.crniird. 
 
 22. 1 pliers, stni)e n(»se, l-iiicli, I'.crinrd. 
 
 (.".40)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 59 
 
 23. 1 pliers, adjustable, S-inch, Danielson. 
 
 24. 1 pliers, side cutting, 8-incii, Utica, No. 50. 
 
 25. 1 pliers, adjustable, 6-inch, Danielson. 
 
 2G. 1 pliers, Auto, 6-inch, combination, cutting, Kraeuter & Co. 
 
 27. 1 pliers, Auto, 8-inch, combination, cutting, Kraeuter & (Jo. 
 
 28. 1 nipper-cut. No. 1, Starrett, 7-inch M. 
 
 20. 1 pliers, G-inch, diagonal. No. 842, Linstroiu. 
 
 30. 1 pliers, 6-inch, diagonal. No. 842, Linstroni. 
 
 31. 1 pliers, compound, S-inch, side cutting. No. 502, Vulcan. 
 
 32. 1 file holder, I. X. L. ' . 
 
 33. 1 pliers, S-inch, adjustable, Danielson. 
 
 34. 1 spoke shave, 3-inch, No. 80, Sargent ; and 1 file cleaner, Colton's No. 10. 
 
 35. 2 files, smooth, S-inch, half-round; 1 file, bastard, 8-inch, half-round; 2 files, 
 
 bastard, 8-inch, flat ; 2 files, saw, 6-inch ; 1 file, bastard, 10-inch ; 1 file, 
 round, G-inch; 1 file, bastard, S-inch, square (all Nicholson files) ; to be 
 contained in a roll 27 inches long and 13^ inches wide, consisting of 10 
 pockets 7 inches deep with a flap 9 inches wide and 20 inches long, 
 pockets extending over 20 inches to take the files specified. This roll and 
 the rolls for items 42 and 43 shall be made of 10-ounce cotton duck, 
 khaki shade, all edges leather bound, to be fastened with straj) and buckle. 
 
 30. 1 screw driver, 4-in(h, Perfect. 
 
 37. 1 wrench, bicycle, 5-inch, Billings & Spencer. 
 
 .38. 1 wrench, bicycle. .5-incli, Billings & Spencer. 
 
 39. 1 palm, sewing; two 4-incli sailmaker's needles; six 4-inch, one-quarter 
 
 curve, needles; 1 ball Irish flax, Barbour's No. 3, 2-ounce; 1 ball wax. 
 
 l.oircr (Iraircr. 
 
 40. 1 stone, 5-inch Carborundum, combination. No. Ill, in wood case. 
 
 41. 1 torch, gasoline, flat, Clayton Lambert No. 48 (fastened by strap with 
 
 buckle). 
 
 42. 1 .set thin open-end wrenches, set of 4 Ronson I to if and 1 J. P. Williams 
 
 No. 30. to be contained in a roll 27 inches by 11 inches, consisting of eight 
 pockets 4J inches deep, extending over 20 inches to take the wrenches 
 specified, with a flap to cover the pockets 20 inches by 9 inches, the ma- 
 terial to be as described in item 35. 
 
 43. 1 set drills, Morse, straight shank, Nos. 1 to 45, inclusive ; 1 drill, f -inch ; 1 
 
 drill, |-inch ; and 1 drill, ^fij-inch ; to be contained in a roll 27 inches by 
 8 inches, consisting of 11 pockets to take large drills, extending over 15 
 inches, with a flap 21 inches with a piece on under side for pockets to 
 take drills Nos. 1 to 4.5, the material to be as described in item 35. 
 
 44. 1 plane, block, If-inch, Stanley No. 110. 
 
 45. 1 drill, hand, Yankee No. 1545. 
 
 46. 1 wrench. 7-inch. Billings & Spencer. 
 
 47. 3 reamers, taper, bit stock, Wiley Russell " Lightning." one 1-inch ; one 
 
 ^-inch ; one f-inch. 
 
 48. 1 hatchet, half. No. 2, thin blade. Germantown No. 316. 
 
 49. 1 snips, tinner's. Reliance No. 10. 
 
 The following list enumerates the tool kits furni.shed by the Signal Corps 
 for use in the installation of fire control, telephone, and small-arms signaling 
 systems, or for any construction work where its magnitud(» warrants such an 
 issue. When used for such purposes they should invariably be returned to a 
 
 (341)
 
 60 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 Signal Corps supply depot when they have served the purpose, unless specific 
 authority for their retention has heen issued. Some of these kits are also 
 issued for use in connection with maintenance of systems : 
 
 Electrical engineer's tool chest. 
 Construction tool chest. 
 Cahle splicer's chest. 
 Pipe fitter's chest. 
 
 Post tool chest. 
 Service tool hag. 
 Inspector's pocket kit. 
 
 The electrical engineer's, construction, and post tool chests are constructed 
 of the hest selected oak or ash lumber, thoroughly seasoned. The ends and 
 sides of these chests are joined by dovetailed joints, and the chests are fitted 
 with steel or malleable-iron corner irons, wrought-ii'on hinges, heavy brass 
 hasps, and heavy brass drop handles. 
 
 The cal)le splicer's and pipe fitter's tool chests are coiistructcil of sheet ste(>l, 
 reinfoi'ced with hardwood strips and nialleablc-iron fittings. 
 
 KI.ECTKICAT. EXOT^'EER S TOOT. CHEST. 
 
 [This i-hest is inauufactiiri'd uuilcr siicrifications X< 
 
 192] 
 
 This chest, shown in figure 8-lG, is issued to electrical experts of the Signal 
 Corps, or to any person in responsible charge of fire-control or post-telephone 
 construction work. 
 
 Fig. 8-16.— CHEST, TOOL, ELECTRICAL ENGINEERS. 
 (342)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 61 
 
 Upon appi'oval of the Chief Signal OfHcer of the Army tliis c-liest is also 
 issued to coast defense Artillerj- Engineers of large coast-defense commands 
 for use in maintaining the fire-control and post-telephone systems. 
 
 The chest contains a full complement of tools necessary for the installation 
 of apparatus. 
 
 Xante ijlutc. 
 
 El.ECTlIIC Al. KXGINEKU'S ToOL < 'HEST. 
 
 U. 8. Signal ("okps. 
 
 No. . 
 
 The tools are distributed as follows: 
 
 C'orcr. 
 
 1. 1 Itacksaw, l(t inches. Xo. 1, Di.sston's. 
 12. 1 rule, 4-foot. S-fold, Stanley. No. 404. 
 
 3. 1 crosscut saw, 20 inches, 9 teeth per inch, Disston. No. 7. 
 
 4. 1 ripsaw, 22 inches, 6 teeth per inch, Disston, No. 7. 
 
 5. 1 hack-saw frame, Star, No. 10. 
 
 G. 1 tape, metallic, 50 feet, Lufkiii Uulc ('o.. No. .jU3. 
 
 First trinj. 
 
 7. 1 .spirit level, pocket, 3-inch, No. 31, Stanley's. 
 
 8. 1 polarity indicator, Manhattan, M. E. S. Co., No. 3321. 
 
 9. 1 wrench, Athol ^Manufacturing Co., " Rapid Transit," G inches, black, No. 
 
 541. 
 
 10. 1 hammer, riveting, 15 ounces, " Atha." No. 234. 
 
 11. 1 hanuner, claw, 1 pound, " Atha," No. 41*. 
 
 12. 1 jackknife, "Empire," AVinsted, Conn., No. 1013. 
 
 13. 1 screw driver, 5 inches, " Perfect." 
 
 14. 1 screw driver, 10 inches, " Perfect." 
 
 l."i. 1 chisel, socket, 1-inch, "Jennings," No. 70. 
 IG. 1 chisel, socket, i-inch, " Jennings," No. 70. 
 
 17. 3 tiles; two 8-inch flat bastard, one 8-inch clear edge, hand, bastard. "Arcade, 
 U. S. A." 
 
 15. 1 chisel, cold, i-inch, G inches long. 
 
 19. 1 screw driver, 2 inches. Tucks Giant. 
 
 20. 1 screw driver. 2^ inches. No. 825. O. W. Bullock & Co. 
 
 21. 1 tool holder with tools. Millers Falls Co., No. 5. 
 
 - Second tiaii. 
 
 22. 1 dividers, pair. 6-inch, P. S. & W. wing, or eciual. 
 
 23. 1 ratchet brace. Millers Falls Co.. 8-inch throw. No. 33. 
 
 24. 2 buffalo grips, with pulleys, one each. Nos. 1 and 2. W. E. Co. 
 
 25. 1 scale, 12-inch, combination square (Athol). No. 500. 12-inch set. complete. 
 2G. 1 center head, combination .square (Athol). No. 5(K). 12-inch set, complete. 
 
 27. 1 square and bevel, combination square (Athol), No. 500, 12-inch set, com- 
 
 plete. 
 
 28. 1 vise, hand (Atlutl). No. .549, H inches. 
 
 29. 1 plane, block, Stanley. No. 130. 
 
 (343)
 
 62 Signal Corps Manual No. 3. — Chapter 8. 
 
 30. 1 shears, pair, metal, W. H. Compton " Reliance," No. 10. 
 
 31. 1 soldering copper, jeweler's, No. 2. 
 
 32. 1 soldering copper. 1 pound. 
 
 33. 1 soldering iron, electric. No. 10, American EU;clric Heater Co., with Edison 
 
 attachment plug. 
 
 Tlilnl tray. 
 
 34. 1 oilstone, " Pike," soft Arkansas, 5-inch, mounted. 
 
 35. 1 pliers, pair, 8-inch, side-cutting, U. D. ¥. & T. Co. No. 30. or P. S. & W. 
 
 No. 40. 
 
 36. 1 ladle. 3-inch, wrought-iron handle. 
 
 37. 1 pliers, pair. 5i-inch. long nose, side-cutting. U. D. F. & T. Co. No. o54. 
 
 38. 1 monkey wrench, Coe's 12-inch, or Bemis & Call's No. 54, or P. S. & W. 
 
 No. 100. 
 
 39. 1 nail puller. Little Giant. 
 
 40. 1 wrench, Stillson, 14-inch. 
 
 41. 1 pliers, pair, 6-inch, side-cutting, U. D. F. & T. Co. No. 50. or P. S. & W. 
 
 No, 40. 
 
 42. 1 i)liers, pair, diagonal cutting, 6-inch, No, 842. F. Linstrom. 
 
 43. 2 clami^s, combination splicing, Klein, No. 309. 
 
 Fourth tray. 
 
 44. 1 countersink, wood, C. E. Jennings, No. 001. 
 
 4.5. 9 drills, steel twist, i-inch, A-inch, §-inch, ilj-inch, 1-inch; Nos. 2, 12, 22, 
 and 30, and 1 center punch, No. 16 Syracuse; straight shank, standard. 
 
 46. 1 punches, set, alphabet, ^-inch. 
 
 47. 1 plumber's kettle, 5 inches. 
 
 48. 1 drill, breast, Millers Falls, No. 18. 
 
 49. 2 shields for fire pot. 
 
 50. 1 figures, set, steel, J-inch. 
 
 51. 1 bit, expansion, 2 cutters, |-inch to 3 inches, Clarke's. 
 
 52. 1 plane, rabbet, ^-inch. 
 
 53. 1 knife, cable sheath, 4i-inch bhuUs " Vilhig(> Blacksmith," IMilwaukee. 
 
 54. 1 bits, set of Irwin auger, with 4-iuch triangular tile, fc-inch to 1-iuch 
 
 by sixteenths. 
 
 IU\(l of chcHt. 
 
 .55. 1 riiniiice, Chiyloii i\: Lanihci-I's, No. 1(t, gai\aiii/,e(l t;mk. 
 
 .56, 1 liii»'nian"s magneto lesting s(M ( rurnislicd by V. S. Signal Corps). 
 
 57. 1 hack-saw blades, dozen, all liard, 10 inches, Milford. 
 
 (•oNsri;r( rioN rooi, ( iii:si'. 
 I'l'liis chrsl is miimifncliii-cil iindiT spcciliciliiiti Ni>. loo. | 
 
 The eonslniction tool chest, figure 8-17, is issued lo any jterson in resixmsi- 
 ble ciiarge of lii-e-conl rol or i)ost-leh'i)hone construclion work, and upon ap- 
 jtroval of the ("liief Signal ( XlictM" of (he .\rmy is issued for use in connection 
 with maintenance. 
 
 While this cJiest is larger in size than the electric.nl engineer's tool cli(>st, 
 it does not contain so great an assortment of tools. 
 
 It is iiarticularly adapted for use where construction or mainteniince of 
 aerial lines is concerned. 
 
 (344)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 63 
 
 Fig. 8-17.— CHEST, TOOL, CONSTRUCTION. 
 
 Name plate. 
 
 Construction Tool Chest. 
 
 U. S. Signal Cokps. 
 
 Xo. . 
 
 This chest shall be proviileil with Corbiu lock Nu. 2882, or equal, and dupli- 
 cate set of keys. 
 
 2 axes, hand, 4J inches, Germantown. 
 1 bag, tool, service, empty. 
 
 1 bit, bellhanger's, 24 by f inches, Syracuse, style E. 
 
 2 bits, sets, Irwin, in boxes (25A), quarters. 
 
 3 blades, hack saw, 10-inch, Milford, dozen. 
 
 1 box, miter. Perfection. 
 
 2 braces, Millers F'alls, No. 33. 
 
 2 chisels, wood, 1-inch, .Tenniiigs, No. 70, socket. 
 
 2 coppers, soldering, with handles, 2i pounds. . 
 
 1 copper, soldering, with handle, jeweler's. No. 1. 
 
 1 dies, marking, steel, figures, ^-inch, hand cut, sot. 
 
 1 dies, marking, steel, letters, i-inch, hand cut, set. 
 
 1 drill, breast, Jlillers Falls, size No. 18. 
 12 drills, rock, t\;-inch, Star. 
 
 12 drills, rock, tk-inch. Star. 
 
 7 drills, twist, straight .<hank, ^ to i inch in sixteenths, standard. 
 
 8 files, assorted, with handles; 2 bastard, half-round, 10-inch; 2 hand, safe 
 edge, 6-inch; 2 slim taper saw tiles, oj-inch ; 1 round file, 6-inch; 1 rasp, 
 cabinet, 10-inch, Genuine McCaffrey ; 2 frames, hack saw, Star, No. 10. 
 
 2 gouges, f-inch, Jennings, No. 91, socket. 
 
 2 grips, buffalo, one each Nos. 1 and 2, W. E. Co., with pulleys. 
 
 (.345)
 
 64 Signal Corps Manual No. 3. — Chapter 8. 
 
 6 hammers, claw, carpenter's, 15-ounce, No. 41i, Atha. 
 
 6 holders, tool, with tools, Millers Falls Co., No. 5. 
 
 1 indicator, polarity, M. E. S. Co., No. 3321. 
 
 2 kits, tool, inspector's pocket. 
 
 1 knife, cable, sheath, 4i-inch blade, " Village Blacksmith." Milwaukee. 
 
 6 knives, P^mpire, No. 1013. 
 
 1 mallet, serving, metal. 
 
 1 mallet, wooden. 
 
 1 oilstone. Pike, soft, Arkansas, 5-incli, mounted. 
 
 1 plane, block, li-inch blade, Stanley, No. 220. 
 
 1 plane, fore, 2i-inch blade, Union Manufacturing Co.'s No. 28. 
 
 1 plane, jack, 2-inch blade. Union Manufacturing Co.'s No. 26. 
 
 1 plane, rabbet, J-inch blade. Union Manufacturing Co.'s No. 157. 
 
 2 pliers, diagonal, cutting, 6-inch, pairs, F. I^instrom, No. 842. 
 
 1 pliers, gas, S-inch, P. S. & W., pair. 
 
 2 pliers, side-cutting. 6-inch, U. D. F. & T. Co. No. 50. or P. S. & W. No. 40. 
 2 pliers, side-cutting, 8-inch, U. D. F. & T. Co. No. 50, or P. S. & W. No. 40. 
 2 pliers, long-nose, 5i-inch, U. D. F. & T. Co. No. 654, pairs. 
 
 1 punch, center, Syracuse, No. 16. 
 
 2 saws, back, 10-inch, Disston's. 
 
 1 saw, compass, 12-inch, Disston's. 
 
 1 saw, crosscut, carpenter's, 20-inch, Disston's. points. No. 7. 
 
 1 saw, rip, carpenter's, 22-incli, Disston's, 6 points, No. 7. 
 
 2 screw drivers, 12-inch, Perfect. 
 
 1 shears, 8-inch, pair, straight trinnners. Compton. 
 1 snips, pair, No. 10, Compton. 
 
 1 tape, 50-foot, metallic, Uufkin, No. 503. 
 
 2 torches, gasoline, Clayton & Lambert, No. 32. 
 1 try-square, steel, 6-inch, Stanley, No. 12. 
 
 1 wrench, screw, 12-inch, Coe's or Bemis & Call's, No. 54. 
 1 wrench. Stillson, 14-inch. 
 
 CABLE splicer's CHEST. 
 
 I This clii'sl is manufactured undor sp(^cilication No. .S18.] 
 
 Tliis cliest. shown in figure 8-18, includes nil lools necessary for Ihc splicing 
 of cal)i(^, together with one-(iuartor pound stearino, 1 pound of ginmned paper, 
 250 i)ai)er sU'cvos three-sixteenths inch by 3 inches, and two cotton strips one- 
 fourth inch, in rolls 5 inches in diameter. De))endence can not be placed in 
 the cliest containing the expendable articles listed above unless it is supplied 
 directly from a Signal Corps supply depot. 
 
 Name pidtc. 
 
 Caiu.e Siujcek's Chest, 
 
 U. S. Si(i.\.\i. ( 'oiu's. 
 
 No. . 
 
 Equipment. 
 
 1 plumber's furna<e, wilh two <liinuieys. No. 1(» ('. iV L. Mfg. Co. (galvanized 
 
 tank ) . 
 1 ladle, 3 indies, W. T., with wrought-iron handle. 
 1 inspector's pocket kit. 
 
 (.•!46)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 65 
 
 Fig. 8-18.— CHEST, TOOL, CABLE SPLICERS. 
 
 1 hotik shave, No. 949, oval, A. S. Morse Co. 
 
 1 plumber's kettle, 5 inches. 
 
 2 soklerins coppers, 2i and 4 ixiunds. with haiidk'.s. 
 
 1 knife, cable, sheath, 4i-incli blade, " Villa,u.e Blacksiniih." Milwaukee. 
 
 1 saw, plumber's, Disston's, 14 inches. 
 
 1 hack-saw frame, " Star." adju.stable. No. It). 
 
 2 hack-saw blades, 10 inclies, dozen, Milford. 
 1 cable dresser, dogwood. 
 
 1 stearine, i pound, in metal" can. 
 
 1 paper, gummed, li inclies wide ("Paster's'"), iioiuids. 
 
 1 luunmer, claw, with handle, Atha, No. 414. 
 
 1 hanmier, plumber'.s, 18 ounces, with handle. No. 24(»(/ Atha. 
 
 1 tool bag, canvas, leather bottom, 20 inches, \V. E. Co.. No. l.">201. 
 2.'>0 paper sleeves, -us inch by 3 inches. 
 
 2 cotton strijts, 1-incli, in rolls, 5 inches diameter. 
 
 () cloths, wiping, moleskin, two 6 inches .square; two 3 inches s(iuare; and two 
 
 5 inches square. 
 1 file, hand, smooth, 6 inches, with handle. 
 1 tile, half-round, bastard, 6 inches, witli liaiidli'. 
 1 rasp. 12 inches, with handle, cabinet. 
 
 1 rule, 2-foot, folding, boxwood, brass bound. No. (ViJ. C S. Co. 
 1 i>lit'rs, pair. S inches, X\ D. F. & T. Co., No. 50. or 1'. S. & W.. No. 40. 
 1 snips. No. 10. Comptou. 
 
 3 drift pins, 1] inches, 14 inches, 2 inches. 
 
 1 torch, gasoline. Clayton & Lambert, No. 32. 
 
 rii'K kittkr's chest. 
 
 [This chest is niainffactiireil imdcr specification No. 276.] 
 
 The pipe fitter's chest is issued whenever work in connection with fire-control 
 or post-telephone systems require the installation of iron conduit. Tools neces- 
 sary in cutting and threading iron conduit from one-half to 2 inch sizes are in- 
 cluded in the equipment f)f this chest. The chest also contains a pipe former, 
 for use in bending iron conduit in sizes from one-eighth inch to IJ inches. 
 This chest is shown in figure 8-19. 
 
 465S1°— 17 23 (347)
 
 66 Signal Corps Manual No. 3. — Chapter 8. 
 
 Fig. 8-19.— CHEST, TOOL, PIPE FITTER'S. 
 
 Naiiic plate. 
 
 Pipe Fitter's Chest, 
 
 U. S. Signal Coups. 
 
 No. . 
 
 Eilitipiiiciil. 
 
 2 pipe wrenches, " Trimo," IS inches. 
 
 1 pipe vise, combination, Prentiss, swivel base, Sl-inch reversible jaws. 
 
 1 pipe cutter, " Trimo," No. 2, i inch to 2 inclies. 
 
 1 stock for dies. Duplex or Oster, No. 3i, l inch to 2 inches, adjustable, witli 
 
 quiclv-opening and self-centering dies and guides. 
 1 set of dies for above stock, I incli to 2 iuclies. 
 1 oil can, malleable iron, 5 ounces. 
 1 burring reamer, for brace, " Lightning," 1| inches. 
 1 pipe former, J inch to 1^ inches, Vanderman, No. 1. 
 1 file, half-round, bastard, 6 inches. 
 1 rasp, smooth, 10 inches. 
 1 tile, hand, smooth, 10 inches. 
 
 POST I'OOI, < IIKST. 
 
 |Tht' i)i)!<t (oi)l clii'sl is inatiiir:i(l iircd niHlcr spci'itii'iil ion No. .".'•O.I 
 
 The post tool chest is for general us(\ II may l»e issikmI to coasl defense 
 artillery engineers, for use in maintenance of fire-control and post-telephone 
 systems. The ('(luipment consists of tools most frequently used in inuintainiug 
 electrical installations. Figure S-20 illusti-ates the post tool chest. 
 
 Niiiiic jtldlf. 
 
 I'osr 'i'ooi, CiiKsf. 
 
 SicNAi, ('oiii's, r. S. Akmv. 
 
 No. . 
 
 3 bite, |§-inch, ^"j-i"^^^ '^'^^^ ,''g-in(li, Irwiu. 
 
 T brace, ratchet, ball-bearing, 8-in<li throw, Milleis l-'alls Co., No. 33. 
 1 chisel, socket, 3-i'i<h, beveletl edge, .leiming.s, No. 70. 
 1 chisel, cold, J-inch. 
 
 (348)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 67 
 
 Fig. 8-20.— CHEST, TOOL. POST. 
 
 1 file, " Arcade," with handle, 6-inch round, bastard. 
 1 file, saw, with handle, 8-inch D. E., " Arcade." 
 1 file, 8-inch, clear edge, " Arcade," with handle, hand, bastard. 
 1 hammer, claw, " Atha," No. 41*. 
 
 1 holder, tool, Millers Falls, No. 5, containing the following: 
 1 4-inch saw. 
 
 1 8-inch saw. 
 
 2 screw drivers. 
 1 chisel. 
 
 1 gouge. 
 
 2 awls. 
 
 1 gimlet. 
 
 1 three-cornered file. 
 
 1 reamer. 
 1 hatchet, claw. 4J-incli blade, "Keen Kutter," A. C. 3. 
 1 knife, draw, 14-inch blade. " Keen Kutter," telegraph pattern. 
 1 oil stone. " Pike." soft, Arkansas. 5 inches, mounted. 
 1 plane, iron, "Keen Kutter," No. 4c. 
 
 1 pliers, pair, 6-inch side-cutting, U. D. F. & T. Co.. No. 50, or P. S. & W.. No. 40. 
 1 rule, 2-foot, fourfold, boxwood, brass bound, C. S. Co., No. 62^. 
 1 saw, 20-inch, crosscut. 9 Pts., Disston's. 
 1 saw, 24-inch, crosscut, S Pts., Disston's. 
 1 screw driver, " Perfect." 6-inch. 
 1 sgnai'e, graduated, 9-inch. " Stanley," No. 20. 
 
 (349)
 
 68 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 1 tape, metallic. " Lufkin." 50-foot. No. 503. 
 
 1 wrench, screw: 10-inch (opening in jaws l\i inches), Coe's or Bemis & Call's, 
 No. 54. 
 
 SERVICE TOOL BAG. 
 
 [The service tool bag is manufactured under specification No. mi!.] 
 
 The service tool bag is constructed of fair leather, not less than three thirty- 
 seconds inch in thickness. It is equipped with suitable carrying strap and lock. 
 Cleats for holding a limited number of tools are sewed to the leather on inside 
 of back, ami consitlerable room for small miscellaneous supplies is available 
 within the bag. ' 
 
 The service tool bag is issued with oi- without tools and may be furnished 
 any Signal Corps construction jiarties. It is also issued for use in mainte- 
 nance of tire-control and post-telephone? systems. Figure S-'21 illustrates the 
 service tool bag. 
 
 Fig. 8-21.— BAG, TOOL, SERVICE. 
 
 Fj qui 1)111 vnl. 
 
 1 try -.square, steel. 4-inch blade. Stanley, No. 12. 
 
 I chisel, cold, A-iucIi. 
 
 1 chisel, wood, ^-inch .socket i)Iade. iron, ring-toi'pcd handle, .Icnning.s, No. 15. 
 
 1 hammer, claw, 16-ounce, Atha, No. 41i. 
 
 1 handle with tools. No. 5, MilhM-s Falls Co. 
 
 1 knife, Em])ire Knife Co.'s No. 1013. 
 
 1 level, pocket, spirit, 3-inch, No. 31, Stanley's. 
 
 1 plane, block, Stanley, 6-inc'h, No. 18. 
 
 1 plier.s, pair, G-inch, side cutting, U. D. F. & T. Co., No. 50, or I'. S. iV: W., No. 40. 
 
 1 plier.s, pair, 8-incli, side cutting, U. D. F. & T. (>>.. No. 50, or W S. iV W., No. 40. 
 
 14-foot rule, folding, l)ox\vood, 8 parts. Stanley, No. 404. 
 
 1 saw, back, lO-iridi, Disston's. 
 
 (360)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 
 
 69 
 
 1 screw driver, Terfect, II. D. S. Co., (i-incli. 
 
 ] .screw driver, Perfect, H. I). S. Co., 10-incli. 
 
 1 solder, resin core, pound. 
 
 1 wrench, screw, Coe's forged, 6-inch monlcey wrencii. or P.einis & Call's No. 54. 
 
 1 wrench, socket, for telephone apparatus, 4-inch. 
 
 1 ratchet hrace. Millers Falls, S-inch throw. No. 33. 
 
 1 i-inch. 
 
 1 g-incli, 
 
 1 ^-inch. \ Irwin aimer bit.s. 
 
 1 g-inch, 
 
 1 1-inch. 
 
 1 polarity indicator, M. K. S. Co., No. 3321. 
 
 I.NSPKCTOK S I'OCKKT KIT. 
 
 [The Inspector's pocket kit is manufactured under specification No. 186.1 
 
 As the name implies, the inspector's pocket kit is of such size that it may 
 he conveniently placed in a pocket of clothing. Tlie tools furnished with this 
 kit are only tho.v;e which may l)e required for tlie repair of an instrument or 
 inside line. 
 
 Fig. &-22.— KIT, TOOL, INSPECTOR'S POCKET. 
 (351)
 
 70 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 The case is made of leather which folds in such a manner that when closed 
 it is impossible for the contents to become dislodged from the case. The 
 inspector's pocket kit is shown in figure 8-22. 
 
 Marking. 
 
 The carrj-ing case has stamped into the leather the following: 
 
 Inspector's Pocket Kit, 
 
 U. S. Signal Corps. 
 
 No. . 
 
 Equipment. 
 
 1 screw driver and skinning knife, combined, with safety spring, Empire, 
 
 No. 372. 
 1 scissors, electrician's, 5-inch, nickeled, J. Wiss & Sons. 
 1 pliers, 5-inch, side cutting, nickeled, pair, U. D. F. & T. Co., No. 12.50, or 
 
 P. S. & W., No. 1240. 
 1 file, bastard, 3-inch, half round, with handle 
 1 tweezers, 4i-inch, nickeled, pair. 
 1 screw driver, 2-inch, Tuck's Giant. 
 1 rule, 2-foot, narrow, fourfold, boxwood, brass bound. C. S. Co., No. 02*. 
 
 Electric drills, spring hammers, and other special tools are kept in stock 
 at Signal Corps general supply depots, and are issued to construction parties 
 when the magnitude of the work involved warrants such action. These special 
 tools should be invariably returned to supply depot from which received, upon 
 completion of the work for which they are issued, unless instructions for 
 different action are issued by the Chief Signal Officer of the Army. 
 
 MOLDINGS. 
 
 Three types of wooden molding are supplied by the Signal Corps where it is 
 desired to conceal inside wiring by this means. The sizes of these three types, 
 winch are designated A, B, and C, respectively, are shown in figure 8-23. 
 
 TYPE -A 
 
 TYPE - B 
 
 Fig. 8-23. — MOLDING, STANDARD TYPES. 
 
 (:i52)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 71 
 
 GROUND KOUS. 
 
 Three types of ground rods are now issued l)y the Signal Corps, type A, type 
 D, and type K. Otlier types liave been issued in tlie past but are now considered 
 obsolete. Tlie type A ground rod consi.sts of a f inch by 5 feet heavily gal- 
 vanized iron rod, pointed at one end and equipped at other end with a short 
 piece of C(tpper wire, soldered to the rod. They are supplied for making gi'ound 
 connections for post telephone .systems employing aerial line construction where 
 it is impi-acticable to connect to a water pipe or wherever it is desired to estab- 
 lish a iicrmanent groiuul connection. Where ground connecticms are obtained by 
 attachment to water pipes, suitai)le clamps for the purpose are furnished. 
 
 The tyi>e D ground rod is 9 inches in length, made of hexagonal .steel one- 
 fourth inch diameter (across flats), pointed at one end and bent into circu- 
 lar form at the other. The circular end is equipped with a machine screw for 
 connection. This ground rod is i^sed almost exclusively for making gi-ound 
 (•(innection for the service buzzer and forms a part of the "ground rod and 
 connector" which is furnished as a part of the service buzzei*. 
 
 The type E ground rod consists of a round galvanized iron rod 24 inches long, 
 liolnted at one end and equipped with a loose iron ring at other. The rod is 
 slightly flattened appi'oximately three-fourths inch below where ring is at- 
 tached and a machine screw for making line connection is threaded through 
 the rod. The loose ring is used for withdrawing the ground rod. This type is 
 for use in connection with cam]) telephone systems or wherever a temporary or 
 semipermanent ground connection Is desired. 
 
 KNIFE SWITCHES. 
 
 Knife switches of various types and sizes are furnished upon receipt of 
 requisition, when approved by the Chief Signal Officer of the Army. 
 
 MOOri. PAINT. 
 
 This paint is similar to black asphaltum paint, and is used on the exterior of 
 conduits, junction boxes, and other surfaces exposed to the weather. Storage 
 battery stands, when constructed, should be given at least two coats of this 
 paint. 
 
 SOLDER. 
 
 Resin core solder consists of a round wire of solder, with aperture through 
 center filled with powdered resin, q'lie resin acts as a flux, and no injurious 
 effects result from its use. Resin-core solder should always be used in solder- 
 ing splices and connections where small wire is involved. 
 
 H(ilf-(ni(t-JifiIf solder is supplied for soldering on lugs and similar work. 
 
 Plumbers' solder is supplied for wiping joints. 
 
 BBIDLE KINGS. 
 
 Bridle rings of various sizes are furnished for supporting bridle wires be- 
 tween aerial lines and cable pole boxes. They are also used where it is desired 
 to support one or more twisted pair wires for a considerable distance along the 
 side or under the cornice of a building. 
 
 The approved bridle ring is of iron, coated with enamel. Figure 8-24 illus- 
 trates the bridle ring. 
 
 (353)
 
 72 Signal Corps Manual No. 3. — Chapter 8. 
 
 Fig. 8-24— RINGS, BRIDLE. ENAMEL COATED. 
 I'HOTOGKAIMIY. 
 
 For service in the field, where :i plioto.uraphic outfit is required, the Signal 
 Corps will supply a high-grade camera and holders, of a type intended for the 
 use of film packs or film rolls, and taking a picture SI by 4^ inches. Film packs 
 or rolls will also be supplied, but no developing or printing equipment will be 
 furnished with them except under special circumstances. ^Yhen all the films in 
 the pack or roll have been exposeil they should be put in strong opaque wrapper 
 and mailed immediately to the Chief Signal Officer of the Army, stating that they 
 are exposed films to be developed and inclosing a statement of the subjects. 
 These will be developed in the signal office, Wasiiington, by an expert photog- 
 rapher, and the person sending them will be furnished one unmounted print 
 of each, enlarged or of size of negative. Pictures which are of special interest 
 and value will be enlarged from tlie negatives to S! by 10 size and plac<»d in 
 the oflicial album. 
 
 All photographic negatives (»f instruments. e(piiiimen(. etc.. known as "techni- 
 cal negatives," will be filed in the ollice of the Cliief Signal Officer of the Army. 
 
 When forwarding photographic pi-ints to the office of the Chief Signal Officer 
 of the Army for file, they should be sent, as far as practicable, unmounted. 
 
 It is not intended tliat iiliotograiili ]>la(cs. fihus, choinicals, or other materials 
 liable to deterioration )k' kept in sfock at general supply dei)ots of tlie Signal 
 Corps. 
 
 SCKKW ANCIIOItS. , 
 
 Screw anchors are used where it is dcsii-cd to C.-isicn tclcpliones, other appa- 
 ratus, conduit, etc., to walls of conci-i'lt" or brick. In using these anchors it is 
 ,nH-essary to first drill a hole of correct dianu'ter j)y means of drills furnished 
 with tool kits. After hole has been drilled proper depth, the screw anchor is 
 insertt'd and wood screw or lag screw of proiier dimensions is screwed into the 
 intei'ior of the anchor. The anchor is of such shape that as the wood screw 
 passes into the anclioi- Ibe lalfei- is (>xpande(l. 
 
 .^opSc/etv ^FH \\codJcreiY H H. Wood Screw 
 
 Composition 
 
 Fig. 8-25.— ANCHORS, SCREW. COMPOSITION. 
 
 (:!r.4i
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 73 
 
 The strength of Ihcsc mikIuh's is jmiiilc for use in ihe iiistallalion of telei)liones 
 and siniihir lifiiil aiti)ai'alus. It iiiusi he uihIci-s|<mm|, liowevcr, that tlie holding 
 IMiwcr of Ihciii is liiiiilcd to the strcnglii of thread in tiie lead or composition, 
 consequently liu-y are not as strong as a lag holt properly cemented into the wall. 
 
 The holes drilled for the anchor should he ahout one-fourth inch deeper than 
 the length of the anchor and of such size as to provide an easy driving 
 fit. Great care should be exercised in installing the anchor in order to iirevent 
 the screw from passing entirely through, therehy coming in contact with bottom 
 of the liole in wall. The anchors are furnished in various sizes, those most 
 conunonly used being for Nos. 1(», 11. oi- \1 wood screws, and for a three-eighths- 
 incli lag screw. 
 
 77/c cutter toijfilc is siipi)lied for use in the installation of conduit, cables, etc., 
 on tiled walls. It has been found to t)e a very satisfactory device for the in- 
 stallation of signal and similar appaialus on wails which are lined with tiling. 
 
 SWITCIIItOARDS. 
 
 Switchboards : 
 Telegraph — 
 2-line. 
 S-Mne. 
 
 .lacks, spring, 
 rings— 
 
 With cord, for Jack si)ring. 
 Switchboard, post telephone, common battery: 
 
 nO-line, visual signals, fully e(iui))jied ami complete with arrester cabinet. 
 KKI-line, visual signals, fully e(nii]i]K'(l and comjjlete with arrester cabinet. 
 l(»(»-line, lamp signals, fully (-(luipiied nnd complete with ;M-rester cabinet. 
 2(K)-line, lamp signals, fully (H|uiiiiied and complete with arrester cabinet. 
 300-line, himp signals, fully ecpiipped ;ind complete with arrester cabinet. 
 GOO-line, lamp signals, multiple, fully ('(piipped and complete with arrester 
 
 cabinet. 
 Repair parts for — 
 Bell, night. 
 Buzzer, complete. 
 Cabinet arrester — 
 
 For 50-line common battery switchboard. 
 For 100-line common battery switchboard. 
 For 200-line common battery switchbo;u-d. 
 Repair parts for — 
 
 IJne terminal, strips of ]0 jiair. 
 Protector — 
 
 Carbon, pairs for. 
 
 Complete, in strips of number of pairs recpiired, W. E. 
 
 No. 84. 
 Heat coils, for. 
 Micas for 
 Strips, wood — 
 
 For mounting line terminals (give length of strip). 
 For m()unting protector (give length of strip). 
 Coils, impedence or retardation, for operator's set. 
 
 (355)
 
 74 Signal Corps Manual No. 3. — Chapter 8. 
 
 Switchboard, post telephone, common battery — Continued. 
 Condenser — 
 
 1-microfarad, cord circuit. 
 2-microfarad, for magneto line. 
 
 2-microfarad, for operator's set (for either primary or secondary 
 circuit). 
 Cord, connecting — 
 
 2 or 3 conductor (give length of cord and style of terminals)— 
 2-conductor, 72-inch. 
 3-conductor, 72-inch. 
 Fuses — 
 
 Baby, 5-ampere. 
 Mica, 1-anipere. 
 Generator^ 
 Complete. 
 Crank for. 
 Handle, hard rubber, for ringing and listening keys. 
 Induction coil for operator's set. 
 Jack, line — 
 
 Common battery, cduiplele (single or in strips of 10). 
 Magneto, coinplete. 
 Jack, operator. 
 Key — 
 
 Night bell. 
 
 Kinging and listening. 
 Lamp — 
 Pilot— 
 
 24 or 30 volt. 
 Cap for. 
 Socket for. 
 Supervisory — 
 24 or 30 volt. 
 Cap for. 
 Socket for. 
 Plug— 
 
 For connecting cord. 
 Operator. 
 Receiver — 
 Cap for. 
 Cord for (give length and style of terminals) — 
 
 Cord, 72-inch, no plugs, 2-i)iii and 2-\vasher terminals, for. 
 Diaphragm for (give diameter). 
 Single head. 
 Relay — 
 Cord — 
 
 Complete. 
 Coils for. 
 Pilot 
 
 ('oil for. 
 
 (.•?56)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 75 
 
 Switchboard, post telephone, common battery — Continued. 
 Relay — Continued. 
 Signal — 
 Line — 
 
 Common battery, complete. 
 Coil for common battery. 
 Magneto, complete with nittimting. 
 Magneto, coil for 
 Supervisory — 
 Coil for. 
 
 Complete with UKiunting. 
 Terminals — 
 Cord, shelf. 
 Lint". 
 Transmitter — 
 Comi)lete. 
 Cords lor (give length, style of terminals, and state whether 1 or 
 
 2 conductor). 
 Mouthpiece for. 
 
 Note. — In requesting repair parts of switchboards and pro- 
 tector cabinet, give manufacturer's name, type, and, if prac- 
 ticable, Signal Corps serial or order number. 
 Switchboard, post telephone, local battery, IHO-line. 
 Switchboard. i)ost telephone, L. K., r>()-drop. 
 Bell, night. 
 
 Bell, night, switch for. 
 Cabinet, arrester, 50-line. 
 Coil, induction, operator's. 
 Cord, connecting (72-inch), without plugs. 
 Generator, hand. 
 Generator, hand, crank for. 
 Jacks, line, complete. 
 Key, ringing and listening, complete. 
 Plug, for connecting cord. 
 Receiver, single head — 
 Complete. 
 
 Cord for, without plug. 
 Diaphragm for. 
 Signals, line — 
 Complete. 
 Coils for. 
 Signal, supervisory — 
 Complete. 
 Coils for. 
 Transmitter — 
 Complete. 
 Cord for. 
 Mouthpiece for. 
 
 (357)
 
 76 Signal Corps Manual No. 3. — Chapter 8. 
 
 Switchboards, niiscelljineoiis : 
 
 20-line, telephone, portable, niauneto tyi)e. 
 Power — 
 
 Complete, for use with motor generator. 
 Type 2. 
 Type 4. 
 
 With (listrilmtini;- frame, for tire-eontrol swilchboui-d room. 
 Frame, (li.stributin.ii, tor. 
 Switchboards, telephone, chargini;- panel, types 1 to 5: 
 Type 1. 
 Type 2. 
 Type 5. 
 
 (In requesting repair parts for any of the instruments mounted on 
 this board, the data shown on name plate of that particular instrument 
 shouhl be entered.) 
 
 <A.\n> TKKEl'HOXK SWITCHHOARl). 
 
 This portable telephone switchboard was desiuned by the Signal Corps and 
 is the result of a development which has been in process a nmnber of years. 
 It is installed at camps in connection with administration telephone systems 
 and has a capacity of 40 lines. 
 
 The ca.se whicli contains the switchboard jtroper is of basswood, lined inside 
 and out with tiber. All of the conii)onent parts of the switchboard proper are 
 moiuited upon an iron frame, which may be withdrawn from case by removing 
 four screws. When this switchboard is set up for oi)eration, it is supi»orted by 
 f(»ur legs, which are tele.scoi)ic and consequently ad.ju.stable. l>y an oitening in 
 the bottom, the cord weights and cords are allowed to protrude through bot- 
 tom, assmning the usual ])osition of the coi'ds of the ordinary conunercial 
 switchboard. The rear of the switchboard case is hinged, and when opened 
 access may lie had to a vei\v compact form of telei)hone-line ])rotectors. Lines 
 may lie very (juickly coiniected to tlu'se protectors, as each comiection is made 
 by means of a Fahnestock clip, it being merely necessary to depress a spring, 
 insert wire, and relea.se spring to make connection. Each protector consists of 
 two carbon blocks and dielectric and a suitai)l(> fuse, all of whii-li is considered 
 an efficient telephone-line ])rotector. 
 
 On tiic front of the switchboard is mounted a clock. No key is required to 
 wind it. it being merely necessary to revolve a disk in order to wind. The 
 Ir.Miismitter is of suspended type and is suiiiiorted by a mtMal arm which folds 
 back and locks when the switchboard is not in use. 
 
 When this switchbo.-ird is iJi-ejiai-ed lor 1ransi)ortation or for sti>rage, the 
 legs which su])port the switchboard are ti'lescoped to their shortest length 
 and ai"e placed in rear of case, suitable mooring for them being provided 
 therein. The upiu-r part of the case, which is detachabli>, is jdacivl into position 
 and fastened. The cord weights and cords are jtlaced in a <'onq)ai"tment pro- 
 vided for that puri)ose. ;iihI the switchboard closely res«Mnl)les a small chest. 
 The accoiiqianying illustration shows the switchboard ready for ()peratlon and 
 ready lor (ransjMirtat ion or storage. 
 
 (358)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 77 
 
 Fig. 8-26.— SWITCHBOARD, CAMP TELEPHONE. 
 
 Part 
 
 No. 
 
 Name. 
 
 Case complete 
 
 Case, handle for 
 
 Case, name plate 
 
 Case, Irimk catch for 
 
 Case, rear cover, complete 
 
 Case, rear cover, hinge for 
 
 Case, front cover for 
 
 Case, les socket for 
 
 T^eg, telescopic 
 
 l>eg, telescopic, upper section 
 
 Leg, telescopic, lower sect ion 
 
 l/cg, telescopic, clamp complete 
 
 l/Cg, telescopic, clampscrcw for 
 
 Leg, telescopic, wing nut and screw. 
 
 Single head receiver 
 
 Single head receiver, headband for. . 
 
 Single head receiver, cord for 
 
 Receiver, cap for 
 
 Transmitter bracket complete 
 
 Transmitter bracket, catch for 
 
 Transmitter bracket, hinge for 
 
 Transmiltcr complete 
 
 Transmit t er, cap for 
 
 Transmit t er , cord for 
 
 Clock. 
 
 Reference 
 
 No. 
 
 Line signals and moimting (strips of 10), give numbers. .. 
 
 Line signal coil 
 
 Line signal shutter 
 
 Line jack and mounting (strips of 10), give numbers 
 
 Receiver jack ( 1 ) 
 
 Receiver j ack plug 
 
 Transmit t er jack ( 1 ) 
 
 Transmit t er jack plug 
 
 Kev, night alarm 
 
 Key, night alarm, handle for 
 
 Key, ringing complete 
 
 (Continued on next page.) 
 (350) 
 
 31
 
 78 
 
 Signal Corps Mcinual No. 3. — Chapter 8= 
 (Parts list— Continued.) 
 
 Part 
 No. 
 
 Name. 
 
 Reference 
 No. 
 
 Key, ringing, handle for 
 
 Key, ringing and listening 
 
 Key, ringing and listening, handle for. 
 
 Cord, connecting 
 
 Cord, connecting plug complete 
 
 Cord, connecting, weight 
 
 Tool kit complete 
 
 Tool kit, snipe nose pliers 
 
 Tool kit , diagonal pliers 
 
 Tool kit, screw driver, large 
 
 Tool kit , screw driver, small 
 
 Tool kit , wrench 
 
 Tool kit , case for 
 
 Magnet o complete 
 
 Magnet o, crank handle 
 
 Magnet o , gear 
 
 Magneto, pinion 
 
 Magneto, contacts 
 
 Magneto, armature 
 
 Lightning arrester complete 
 
 Fahens t ock clip 
 
 Carbons and dielectrics 
 
 Fuses, line 
 
 B uzzer, ringing 
 
 Battery (2 No. 6 dry cells per set) 
 
 33 
 34 
 35 
 36 
 37 
 38 
 39 
 40 
 41 
 42 
 
 TELEPHONES. 
 
 Wall, common battery (uulo pay station). 
 
 Field. 
 
 Common battery : 
 
 Desli set, complete. 
 Repair parts for — 
 Bell set, complete. 
 Binding posts, locknut. 
 Condenser, 2-microfarad, complete. 
 Cord, main (state whether 2 or 3 conductor). 
 Cord, receiver. 
 Desk stand, complete. 
 Induction coil, complete, 
 lieceivei- — 
 Cap for. 
 
 Diaidn-agiii for (give diaiiieler). 
 lliiiid, coinplclt'. 
 Sliell lor. 
 Ringer — 
 
 Coils for. 
 
 ('onipleic Willi g(»iig.s. 
 (Jongs for. 
 Transmit I or — 
 
 ( 'nniplclr. 
 Kmicklc joinl lor. 
 Mouthpiece for. 
 Wall set, complete, wooden case. 
 Wall set, metal case. 
 Repair parts for — 
 
 Binding posts, lockiuit. 
 (!oil, induction, complete. 
 Condenser, 2-microfa»ad, complete. 
 (360)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 79 
 
 Common battery telephones. 
 
 Wall set, metal case — Continued. 
 Repair parts for — Continued. 
 Hook, switch — 
 
 Complete, hut without hook lever. 
 Hook lever for. 
 Receiver, hand — 
 Cap for. 
 Complete. 
 Cord for. 
 
 Diaphragni for {fiivr diameter). 
 Shell for. 
 Ringer — 
 
 Coils for. 
 
 Complete, with gong. 
 Gongs for. 
 Transmitter — 
 Complete. 
 Arm and base. 
 Mouthpiece for. 
 Telephone, local battery : 
 Desk set, complete. 
 
 Repair parts for — 
 
 Bell sets, complete. 
 Binding posts, locknut. 
 Cord for receiver. 
 
 Cord, main (state whether 3 or 4 conductor), 
 Desk stand, complete. 
 Generator — 
 Complete. 
 Handle for. 
 Induction coil, complete. 
 Receiver, hand — 
 Cap for. 
 Complete. 
 
 Diaphragm for (give diameter). 
 Shell for. 
 Ringer — 
 
 Coils for. 
 
 Complete, with gongs. 
 Gongs for. 
 Transmitter — 
 Complete. 
 
 Heads (knuckle joint). 
 Mouthpiece for. 
 ^^"all siM. complete. 
 
 Repair parts for — 
 
 Binding posts, locknut. 
 Hook switch — • 
 
 Complete, but without hook lever. 
 Lever for. 
 Induction coil, complete. 
 
 (361)
 
 80 Signal Corps Manual No. 3. — Chapter 8. 
 
 Local battery telephones: 
 
 Wall set, complete — Continued. 
 Repair parts for — Continued. 
 Magneto generator — 
 Complete. 
 Crank for. 
 Receiver, hand — 
 Cap for. 
 Complete. 
 Cord for. 
 
 niaphragm for (give diameter), 
 t^hell for. 
 Ringer — 
 
 Coils for. 
 
 Complete, with gongs. 
 Gongs for. 
 • Tran.smitter — 
 
 Arm and base. 
 Complete. 
 Mouthpiece for. 
 Common battery, fire control (metal case) : 
 Gun, C. B. F. C. 
 Hand set. 
 Head set. 
 
 Plotter's set, C. B. F. C. 
 Wall, C. B. F. C. 
 Battery commander's, C. B. F. C. 
 Camp : 
 
 Maintenance parts — 
 Hand set, complete. 
 Kinger. 
 Generator. 
 Cord, for hand set. 
 Field (now issued for target ranges oiilyi. in.iinltMiauce parts; 
 Blocks, hard rubber — 
 Receiver ternunal. 
 TransmitttM" tenuinnl. 
 Cases, wtMid. 
 
 Clips, Itrass, inductinii coil ifrmiiuu. 
 Coii.s — 
 
 Induction. 
 Receiver. 
 Ringer, ."lOO-ohm. 
 Cords, telephone, connector, 
 ('orners, metal. 
 
 Cover, generator crank opeiuiig. 
 Cranks, generator, 
 ♦"'ups, electrode, complete. 
 Diagram, wiring. 
 Diaphragm — 
 Receiver. 
 Transmitter. 
 Disks, mica, transmitter. 
 
 (302)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 
 
 SI 
 
 Fit'ld telephone (now issued for target ranges only), maintenance parts — Contd. 
 Fastener for cover. 
 Gasket, soft rubber — 
 
 Switch opening. 
 
 Transmitter diaphragm. 
 Generators, 3-l)ar, with cranks. 
 Gongs, bell, with screws and brackets. 
 Hand sets. 
 Hinges, strap. 
 Post, binding — 
 
 Line. 
 
 Lock nut. 
 
 Receiver terminal. 
 
 Transmitter term i tin 1. 
 
 Wing nut. 
 Ringer, l,0()0-ohm. 
 Rings, swivel, and jilates. 
 Shells, liard rubber, for liand receivers. 
 Springs — 
 
 Switch, with platinum contact. 
 
 Transmitter, dampening. 
 Strni)s. carrying, black leather, complete with buckles and rings. 
 Terminals, coil. 
 
 WIRE. 
 
 A great percentage of all wire purchased by the Signal Corps is manufac- 
 tured in accordance with Signal Corps specifications and is thoroughly tested 
 by a competent inspector before being accepted. 
 
 DESIGXATIOX OF WIUE IX MILS. 
 
 Hereafter in all specifications, purchase orders, contracts, requisitions, and 
 other communications concerning the purchase, inspection, and issue of all 
 types of solid wires by the Signal Corps, reference will be made to the sizes of 
 wires by stating the diameter in thousandths of an inch (mils) in accordance 
 with the table of mils shown below. 
 
 1 
 
 2 
 
 3 
 
 1 
 
 2 
 
 3 
 
 1 
 
 2 
 
 3 
 
 1 
 
 2 
 
 3 
 
 Mils. 
 
 B.W.G. 
 
 B.&S. 
 
 Mils. 
 
 B.W.G. 
 
 B.&S. 
 
 Mils. 
 
 B.W.G. 
 
 B.&S. 
 
 Mils. 
 
 B.W.G. 
 
 B.&S: 
 
 460 
 410 
 
 365 
 
 325 
 289 
 258 
 229 
 204 
 
 182 
 
 162 
 144 
 
 0000 
 000 
 
 00 
 
 Oandl 
 2 
 3 
 
 4 and 5 
 6 
 
 7 
 
 8 
 9 
 
 0000 
 000 
 
 00 
 
 
 
 1 
 
 2 
 3 
 4 
 
 5 
 
 6 
 
 128 
 114 
 
 102 
 
 91 
 81 
 72 
 64 
 57 
 
 51 
 
 45 
 40 
 
 10 
 12 
 
 13 
 14 
 15 
 16 
 17 
 
 18 
 
 i9 
 
 8 
 9 
 
 10 
 
 11 
 12 
 13 
 14 
 15 
 
 16 
 
 17 
 18 
 
 36 
 32 
 
 28.5 
 
 25.3 
 22.6 
 20.1 
 17.9 
 15.9 
 
 14.2 
 
 12.6 
 11.3 
 
 20 
 21 
 
 22 
 
 23 
 
 24 
 
 25 
 
 26 
 
 27 
 
 f 28 
 
 { and 
 
 I 29 
 
 30 
 
 31 
 
 19 
 
 20 
 
 21 
 
 22 
 23 
 24 
 25 
 26 
 
 } '^ 
 
 28 
 29 
 
 10.0 
 8.9 
 
 8.0 
 
 7.1 
 6.3 
 5.6 
 5.0 
 4.5 
 
 4.0 
 
 3.5 
 3.1 
 
 33 
 34 
 35 
 and 
 36 
 37 
 38 
 
 39' 
 
 40 
 
 
 
 30 
 31 
 
 1 32 
 
 33 
 34 
 35 
 36 
 37 
 
 38 
 
 39 
 40 
 
 Note. — The standard sizos in mils indicated are the sizes in the American wi 
 gauge (B. & S.) rounded oflf to about the usual limits of commercial accuracy. 
 
 (See next page.) 
 
 4(mS1°— 17 24 
 
 (.%.^)
 
 82 Signal Corps Manual No. 3. — Chapter 8. 
 
 The table shows (column 1) the War Department standard sizes, diameter 
 in mils; and (column 2) the nearest commercial Birmingham wire gauge; 
 and (column 3) Brown & Sharpe, or American wire gauge, for approximately 
 the same size wire. 
 
 The difference between successive sizes is approximately a constant per cent 
 of the size. 
 
 The following wires are supplied by the Signal Corps for radio-telegraph in- 
 stallations only and, inasnmch as they are special in character, will not be de- 
 scribed herein. For detailed information concerning them. Signal Corps specifi- 
 cation No. 416 should be perused. 
 
 High tension (one size only). Antenna cord (one size only). 
 
 Low tension (five sizes). Counterpoise (one size only). 
 
 Antenna (two sizes). Silicon bronze (one size only). 
 
 Wires supplied liy the Signal Corps in connection with installation of fire- 
 control systems, jiost-telephone systems, small-arms target-range signaling sys- 
 tems, and lines of security and information are as follows : 
 
 Inside twisted pair (one size only). 
 
 Inside twisted triple conductor (one size only). 
 
 House (one size only). 
 
 Pot head (one size only). 
 
 Cross-connecting (two sizes 25.3 and 30 mils, respectively). 
 
 Rubber-covered (various sizes). 
 
 Fixture (two sizes, 40 and 51 mils, respectively). 
 
 Weatherproof (various sizes). 
 
 Bridle (one size only). 
 
 Outside twisted pair (two sizes, 64 and 81 mils, respectively). 
 
 Outside distributing, copper-clad (one size only). 
 
 Hard-drawn copper (various sizes). 
 
 Galvanized iron (various sizes). 
 
 Buzzer (one size only). 
 
 Field (one size only). 
 
 Office (two sizes, 36 and 51 mils, respectively). 
 
 A brief description of these wires in the order listed follows: 
 
 INSIDE TWISTED PAIR. 
 
 This wire consists of two separately insulated conductors twisted together. 
 Each conductor is 40 mils diameter, soft cojipor, and is insulated with rubber 
 compound and cotton braid. The braid of one conductor is red and of the other 
 black. 
 
 This wire should invariably be used for the inside wiring of fire-control 
 stations, and may be used for inside post-telephone system work at points where 
 wire having unusually high insulation is desired. 
 
 INSIDE TWISTED TltlPI.E COXDUrTOR. 
 
 This wire consists of three separately iiisulated conductors twisted together. 
 Two conductors are exactly in accordan<v with those described under " Wire, 
 Inside twisted pair," iinmedlately preceding. The third conductor is also similar 
 except that it is supplied with a yellow braid. 
 
 This wire is used in fire-control stations where the head or hand set of a tele- 
 phone is used at some distance from telephone instrument proper and connects 
 the telephone with telephone terminal block lo which is connected the head or 
 
 (364)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 83 
 
 liiiiid set. It is also used between telephones proper and terniiiuil boxes in tire- 
 control stations when it is desired to use the earth as one side of the rin^inj; 
 (calling) circuit. It may also l)e used in connection with post telephone .systems 
 where a triple conductor wire having unusually high insulation is desired. 
 
 This wire consists of two separately insulated conductors twisted together. 
 Each conductor is 36 mils diameter, soft copper, and is insulated with rubber 
 compound and cotton braid. Braids of conductors are furnished in various 
 colors, but invariably one braid contains a tracer w-hich consists of a thread of 
 different color woven in the braid. 
 
 This wire should be used for inside wiring at post telephone substations, 
 except substations which are tire-control stations. 
 
 POT HEAD. 
 
 This wire consists of two separately insulated conductors twisted together. 
 Each conductor is 36 mils diameter, soft copper, and is insulated with rubber 
 compound only, there being no braid supplied. A conductor may be traced by 
 means of two ridges formed of the rubber compound of one conductor. 
 
 Formerly pot-head wire, with one conductor black (natural compound color) 
 and the other red, was furnished. The colored compound becomes porous in a 
 comparatively short time ; consequently only pot-head wire with natural color 
 compound should be used under any circumstances for permanent construction. 
 
 Pot-head wire is used in the construction of pot heads of all paper-insulation 
 cable and may be used as cross-connecting wire in terminal boxes. 
 
 A special pot-head wire is furnished for use in the Tropics. 
 
 CROSS CONNECTING. 
 
 This wire consists of two separately insulated conductors twisted togetlier. 
 Each conductor is of soft copper, insulated with rubber compound and a flame- 
 proof cotton braid. It is a commercial product and replaces the large wire with 
 yellow and black braid formerly furnished as cross-connecting wire. 
 
 This wire should ordinarily be used for cross connecting in all station ter- 
 minal boxes, but not in submarine cable terminal boxes. Cross connecting in 
 submarine cable terminal boxes should be accomplished with fixture wire, 
 described later. 
 
 RUBBER COVERED. 
 
 This wire consists of a single soft-copper conductor insulated with rubber 
 compound and cotton braid impregnated with a waterproof compound. The 
 sizes of the conductors most commonly used are 64 mils and 81 mils, respec- 
 tively. Any commercial size of conductor can be furnished. This wire is used 
 principally in fire-control switchboard rooms for power leads and in A\iro forms 
 for power switchboards ; also in the 51-mil size for wiring to apparatus at 
 butts of small-arms target ranges. 
 
 This wire consists of a single soft-copper conductor insulated with a thin 
 wall of rubber compound and a cotton braid impregnated with waterproof com- 
 pound. It is furnished in two sizes, the conductor being 40 mils or .")! mils 
 diameter. Fixture wire is used in wire forms for power or distril)uting switch- 
 boards and in cross connectiiffe in submarine cable terminal boxes. 
 
 (365)
 
 84 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 WEATHERPROOF. 
 
 This wire consists of a single hard-drawn copper conductor insulated with a 
 triple cotton braid impregnated with a waterproof compound. It is used for 
 extending aerial lines through the foliage of trees. It is also used in wire 
 forms for power switchboards. Weatherproof wire is more rigid than " wire, 
 rubber-covered," and for this reason only is it preferable for wire forms. 
 
 This wire consists of a single soft-copper wire 51 mils in diameter, insulated 
 with rubber compound to an outside diameter of five-thirty-seconds inch, and 
 covered with a closely woven braid impregnated with a weatherproof com- 
 pound. 
 
 This "wire can be furnished with two conductors, twisted together, if desired. 
 
 Bridle wire is used for connecting aerial lines with arresters in pole boxes, 
 or wherever a 51-mil diameter wire with heavy insulation is necessary. 
 
 It differs from fixture wire in tlmt the over-all dimension is greater. 
 
 OUTSIDE TWISTED PAIR. 
 
 This wire consists of two separately insulated conductors twisted together. 
 Each conductor is insulated with rubber compound am! a cotton braid impreg- 
 nated with moisture-proof compound. 
 
 Two sizes of this wire have been furnished, the conductors being 81 mils and 
 64 mils in diameter, respectively. 
 
 Outside twisted pair is useil in connecting aerial lines witii substations and 
 under certain conditions it may be used as aerial line, also for temporary work 
 of viirious characters. 
 
 OUTSIDE DISTRIBUTING, COPPER CLAD. 
 
 This wire consists of two separately insulated conductors twisted together. 
 Each conductor consists of a steel core upon which is welded a copper coat of 
 uniform thickne.ss. Each conductor is 4^ mils diameter and is insulated witli 
 rubber compound and a closely woven cotton braid impregnated with moisture- 
 proof compound. 
 
 Outside <listributing copper-clad wire in a great measure supersedes the out- 
 side twisted pair de.scribed in the preceding item, it is smaller and lighter, but 
 used for the same purposes. 
 
 HARD-DRAWN COPPER. 
 
 This wire consists of one noninsulated conductor of hard-drawn copper. It 
 can be furnished in an.v of the commercial sizes, but smaller than 81 mils 
 diameter should not be used for permanent lines. The 81 mils diameter size is 
 suitable for practically all aerial lines constructed by the Signal Corps. 
 
 
 Coppci 
 
 line icirc, lianl 
 
 Innni ( hare). 
 
 
 
 Weight 
 
 Weight 
 
 Resistance 
 
 Resistance 
 
 Tensile 
 strength. 
 
 Coil 
 lengths. 
 
 Diameter. 
 
 per 1,000 
 feet. 
 
 per 
 mile. 
 
 perl ,000 
 feet at 68°. 
 
 per mile 
 at 68°. 
 
 Mils. 
 
 Pounds. 
 
 PounJ.t. 
 
 Ohms. 
 
 Ohms. 
 
 Pounds. 
 
 Feet. 
 
 182 
 
 100 
 
 529 
 
 0. 323 
 
 1.71 
 
 l,,'j,')0 
 
 1,000 
 
 102 
 
 79 
 
 419 
 
 .407 
 
 2.15 
 
 1,235 
 
 1,000 
 
 144 
 
 03 
 
 331 
 
 . Til 3 
 
 2.71 
 
 980 
 
 2,040 
 
 128 
 
 '.JO 
 
 2l'>2 
 
 .(i40 
 
 3.41 
 
 778 
 
 2,040 
 
 114 
 
 39 
 
 208 
 
 .815 
 
 4.30 
 
 017 
 
 2, 040 
 
 102 
 
 32 
 
 1(16 
 
 1.028 
 
 r,. 43 
 
 489 
 
 2,640 
 
 91 
 
 2T, 
 
 132 
 
 1 . 29(i 
 
 0.S4 
 
 388 
 
 5,280 
 
 SI 
 
 20 
 
 10,'i 
 
 1.0.35 
 
 8. 03 
 
 307 
 
 5,280 
 
 72 
 
 l.-).7 
 
 83 
 
 2.001 
 
 10.88 
 
 244 
 
 6,280 
 
 M 
 
 12.4 
 
 fi.") 
 
 2.699 
 
 13. 72 
 
 193 
 
 5,280 
 
 (.".06}
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 85 
 
 i;A1,\ AMZKll iltO.V. 
 
 This wire consists of oni' noniiisulated coiKluctor of iron wire, lieavily fral- 
 vanized. It can ho furnislied in any of the commercial sizes, hut is usually 
 supplied in the 81 or SO mils diameter size for provisional fire-control or post 
 telephone system lines, and is always furnished in this size for field lance-pole 
 lines ; 144 or 148 mils diameter size is usually furnished for permanent tele- 
 graph " lonji: lines." There are three connuercial grades of this wire, which 
 are designated as follows: B, BB, and EBB. The EBB grade Is supplie<l by 
 the Signal Corps unless tensile strength is more important tlian conductivity 
 for a given size. 
 
 In connection witli tire control and post telephone systems, g-.dvanized-iron 
 wire should be used for aerial lines for piT)visional or temporary installation 
 only. 
 
 Galvanised-iron wire. 
 
 Diame- 
 
 Area. 
 
 ■Weight 
 
 per 1 ,000 
 
 feet. 
 
 Weight 
 
 Breaking 
 
 Resist- 
 ance per 
 
 Length 
 
 ter. 
 
 per inile. 
 
 strength. 
 
 mile at 
 68° F. 
 
 of coil. 
 
 Mih. 
 
 dr. mils. 
 
 Pounds. 
 
 Pounds. 
 
 Pounds. 
 
 Ohms. 
 
 Feet. 
 
 2S9 
 
 83, 521 
 
 219 
 
 1, 160 
 
 3,480 
 
 4.05 
 
 1,000 
 
 258 
 
 66, 564 
 
 175 
 
 920 
 
 2,760 
 
 5.08 
 
 1,000 
 
 229 
 
 52, 441 
 
 138 
 
 726 
 
 2,178 
 
 6.44 
 
 1,000 
 
 204 
 
 41,616 
 
 108 
 
 576 
 
 1,728 
 
 8.12 
 
 1,320 
 
 1S2 
 
 3.3, 124 
 
 87 
 
 458 
 
 1,424 
 
 10.19 
 
 2; 000 
 
 162 
 
 26, 244 
 
 69 
 
 363 
 
 1,089 
 
 12.87 
 
 2,000 
 
 144 
 
 20,736 
 
 54 
 
 287 
 
 861 
 
 16.28 
 
 2, 640 
 
 128 
 
 16. 384 
 
 43 
 
 227 
 
 681 
 
 21.21 
 
 2,640 
 
 114 
 
 12,996 
 
 34 
 
 179 
 
 537 
 
 25.98 
 
 2,640 
 
 102 
 
 10,404 
 
 27 
 
 144 
 
 432 
 
 32.46 
 
 2,640 
 
 91 
 
 8, 281 
 
 22 
 
 115 
 
 345 
 
 40.80 
 
 2,640 
 
 81 
 
 6,561 
 
 17 
 
 91 
 
 271 
 
 51.56 
 
 2,640 
 
 This wire consists of a single insulated conductor composed of two steel and 
 one soft copper wires, each having a diameter of 12 mils before tinning. The 
 insulation consists of a doul)le wrap of cotton impregnated with an insulating 
 compound. The finished wire has a diameter between 0.0.35 and 0.004 inch, iind 
 is furnished by manufacturers on metal spools which contain one-half mile of 
 the wire. Buzzer wire is used exclusively in the field in hurriedly establishing 
 communication with a given location. If practicable it should be recovered 
 when it lias served its purpose. 
 
 FIELD. 
 
 Field wire is a single insulated conductor made up of 10 steel wires and 1 
 soft copper wire. The copper wire is 28.;") niils diameter and each of tlie steel 
 wires 12 mils diameter before tinning, diameter of conductor 54 mils. 
 
 The conductor is insulated as follows : First, with a serving of cotton, then 
 a seamless rubber compound having a thickness of 0.024 inch. Tlie rubber- 
 covered wire is then covered with a smooth, closely-woven braid of cotton, 
 saturated with a moisture repellent compound and given a wax polish finish. It 
 is furnished in half-mile lengths on small wooden reel.s. 
 
 Field wire is used exclusively in the field in hurriedly establishing communi- 
 cation with a given location and is usually paid out from a wire cart designed 
 for the purpose. It is also used in semipermanent linework where it may be 
 supported by means of lance poles. 
 
 /S'p/ir/j!/; field tcire. — When field wire has been broken or cut. it will neces- 
 sarily have to be spliced. Splices in field wires may be either temporary or 
 
 (367)
 
 86 Signal Corps Manual No. 3. — Chapter 8. 
 
 permanent in character. If the wire is severed while in use, the lineman should 
 locate the fault and complete the splice as quickly as possible. A temporary 
 splice may be made as follows : The two ends of the severed wire having been 
 cauglit up the ends are scraped of insulation (skinned) after a square knot has 
 first been tied by knotting the two ends of the wire together. This knot is made 
 to take the strain off of the splice. Care in making the square knot should be 
 observed, so that a granny knot may not result. After knotting the wire the 
 skinned ends are then twisted tightly together. 
 
 As soon as convenient the wire should be gone over, the bad lengths cut out, 
 and permanent splices made in place of the temporary ones. To make a per- 
 manent splice, skin off the insulation for about 4 inches on each end and sepa- 
 rate the steel and copper strands, so that the two copper strands may first be 
 wound tightly together. The copper may be distinguished from the steel by 
 its greater pliability. The steel strands are now wound together, making the 
 joint mechanically secure. Snap off the loose ends and solder the joint. Wind 
 insulating tape tightly over the splice. 
 
 This wire has a single soft copper conductor of either 36 or 51 mils diameter, 
 insulated with a vulcanized rubber compound, covered with a close-filled 
 polished cotton braid, and is furnished in 500-foot coils. It is used principally 
 for inside wiring in connecting up telegraph instruments, electrc bells, etc. 
 
 MISCELLANEOUS WIKES. 
 
 In connection with making electrical measurements and for various pur- 
 poses, the following wires are supplied under special approval : 
 
 Magnet ; specify mils in diameter, supplied in single or double cotton or 
 
 silk insulation. 
 Resistance ; finished as follows — 
 
 Single cotton covered. 
 
 Double cotton covered. 
 
 Single silk covered. 
 
 Double silk covered. 
 
 Bare. 
 Silicon, bronze, bare, 28.5 mils in diameter ; supplied in ^-mile spools. 
 German-silver, 30 per cent alloy; see note under table below. 
 Climax ; see note under table below. 
 S. B., bare, 32.6 mils in diameter (Driver-Harris). 
 (Jernian-silver, 18 per cent alloy; see table below. 
 
 To secure uniformity in units relative to i)(>nis of wire, llu> following will be 
 observed : 
 
 All galvanized iron wire to be in miles. (Fractions less lliaii a half mile may 
 be disregarded.) 
 
 All bare copper wire in feet. 
 
 All insulated cop))(>r wire in feet. (This iiK-ludcs outs'de :iiid inside twisted 
 pair, bridle, potliead, and office wire.) 
 
 Huzzer wire, in sjhioIs. ( Kacli standard spool liolds ono-lialt' mile.) 
 
 Fuse wire, in pounds. 
 
 Field wire, in miles. 
 
 Magnet wire, in pt)unds. 
 
 Messenger strand wire, in feet. 
 
 Uesistance wire, in ixnmds. 
 
 Deep-sea .sounding wire, in fathoms. 
 
 (368)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 87 
 
 Seizing wire, in ixmnds. (This is a .soft (1. I. wire, 40 mils in diameter, for 
 serving armor wires of D. S. cable.) 
 
 Annunciator wire, in pounds. (This is copper wire of about 30 or 4(J mils in 
 diameter, cotton and paraflin insulation.) 
 
 Tabic of lengths and resistances of standard spools "18 per cent " German-silver 
 
 alloy resistance wire. 
 
 M 
 
 i 
 
 Feet per 
 
 ounce, appro.vimate. 
 
 Ohms per 
 
 ounce, approximate 
 
 
 1 . 
 
 6 
 
 0-3 
 
 
 
 
 
 
 
 
 
 
 ^3 
 
 
 
 
 
 
 
 
 
 
 
 a 
 
 
 ^ 
 
 ♦J 
 
 
 
 
 J^ 
 
 ■*-> 
 
 
 
 
 
 ^ 
 
 l^ 
 
 8 
 
 8 
 
 ^ 
 
 ^ 
 
 
 
 
 
 8 
 
 
 M 
 
 
 g 
 
 
 
 0) a 
 
 <C 
 
 
 Wl 
 
 
 c a 
 
 <B a 
 
 01 
 
 « 
 
 
 
 a 
 
 •fi 2. 
 
 
 ■^:i 
 
 ^ 
 
 <D 
 
 
 S2 
 
 u2 
 
 3 
 
 a) 
 
 • 
 
 p 
 
 03 
 
 5 
 
 ^ 
 
 
 
 a 
 
 3 
 
 
 q 
 
 ^ 
 
 § 
 
 a 
 
 3 
 
 
 a" 
 
 
 2; 
 
 ft 
 
 m 
 
 ft 
 
 M 
 
 « 
 
 fi 
 
 CO 
 
 
 
 au 
 
 n 
 
 
 
 32 
 
 4 
 
 19 
 
 19 
 
 20 
 
 20 
 
 20 
 
 3.5 
 
 3.5 
 
 3.5 
 
 3.6 
 
 4.0 
 
 18.4 
 
 25.3 
 
 4 
 
 29 30 
 
 30 
 
 31 
 
 32 
 
 8.7 
 
 9.0 
 
 9.0 
 
 9.1 
 
 10.2 
 
 30.0 
 
 20.1 
 
 4 
 
 45 
 
 48 
 
 49 
 
 50 
 
 51 
 
 21.0 
 
 22.0 
 
 22.0 
 
 23.0 
 
 20. 
 
 47.0 
 
 12.6 
 
 2 
 
 ino 
 
 115 
 
 120 
 
 125 
 
 130 
 
 120.0 
 
 135.0 
 
 139.0 
 
 145.0 
 
 165.0 
 
 119.0 
 
 10.0 
 
 7. 
 
 150 
 
 175 
 
 185 
 
 195 
 
 200 
 
 286.0 
 
 332. 
 
 345.0 
 
 362.0 
 
 416.0 
 
 189.0 
 
 8.9 
 
 1 
 
 ISO 
 
 220 
 
 /230 
 
 245 
 
 260 
 
 432.0 
 
 519.0 
 
 537.0 
 
 524.0 
 
 662.0 
 
 239. 
 
 8.0 
 
 1 
 
 220 
 
 270 
 
 285 
 
 300 
 
 325 
 
 658.0 
 
 807.0 
 
 840.0 
 
 904.0 
 
 1,050.0 
 
 295.0 
 
 7.1 
 
 1 
 
 270 
 
 340 
 
 350 
 
 383 
 
 410 
 
 992.0 
 
 1,250.0 
 
 1,310.0 
 
 1, 420. 
 
 1,680.0 
 
 374.0 
 
 6.3 
 
 1 
 
 320 
 
 410 
 
 440 
 
 480 
 
 520 
 
 1,490.0 
 
 1,930.0 
 
 2,030.0 
 
 3, 530. 
 
 4,2.30.0 
 
 476.0 
 
 5.6 
 
 1 
 
 370 
 
 500 
 
 540 
 
 600 
 
 650 
 
 2, 200. 
 
 2,970.0 
 
 3, ISO. 
 
 3, 532. 
 
 4,230.0 
 
 602.0 
 
 5.0 
 
 1 
 
 440 
 
 610 
 
 650 
 
 740 
 
 825 
 
 3, 260. 
 
 4, 580. 
 
 4,880.0 
 
 5,500.0 
 
 6, 730. 
 
 756.0 
 
 4.5 
 
 1 
 
 500 
 
 740 
 
 800 
 
 920 
 
 1,040 
 
 4,770.0 
 
 6, 950. 
 
 8,080.0 
 
 8,410.0 
 
 10, 700. 
 
 955.0 
 
 4.0 
 3.5 
 3.1 
 
 1 
 1 
 
 1 
 
 
 
 970 
 1,150 
 1,400 
 
 1,150 
 1,400 
 1,730 
 
 1,310 
 1,650 
 2 090 
 
 
 
 12, 500. 
 21, 600. 
 29,700.0 
 
 14,100.0 
 22,000.0 
 34, 700. 
 
 16,900.0 
 26,800.0 
 42, 700. 
 
 1,200.0 
 1,530.0 
 1,930.0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 These values are approximate. 
 
 When '' Climai" resistance wire is ordered, it should have a resistance approximately 2.777+times that 
 of table. The other vahies for Climax wire are the same as above. 
 
 When 30 per cent German-silver wire is ordered, it should be estimated that its resistance is approxi- 
 mately 1.55 times that of 18percent wire. 
 
 l?are wire will be supplied in packages as above. Its resistance, etc., may readily be determined from 
 data above. 
 
 Bare S. B. wire 12.6 mils in diameter, supplied in ounce spools (about 150 feet). Resistance, 2.1 ohms 
 per foot. 
 
 MISCELLANEOUS FIELD EQUIPMENT. 
 
 WniE CARRIER. 
 
 The wire carrier shown in figure 8-27 is used for paying out or recovering 
 buzzer wire. It is also used for carrying the antenna and counterpoise of 
 the Signal Corps portable radio sets. A carrier will hold one-half mile (same 
 as metal reel) of buzzer wire, and canvas covers for them are supplied when 
 needed. Wire can be conveniently paid out and recovered by means of these 
 reels. 
 
 Fig. 8-27.— CARRIER, WIRE. 
 (369)
 
 88 
 
 Signal Corps Manual No. 3. — Chapter 8. 
 
 HAND REEL. 
 
 This apparatus may be iised for paying out and recovering buzzer wire. 
 It is so proportioned that the metal spool \ipon ^A'hich buzzer wire is furnished 
 tits the trunnions, and by means of a crank handle the spool can bo revolved. 
 Figure S-28 shows the construction of this apparatus. 
 
 3' ^ 
 
 Fig. 8-28.— REEL, HAND. 
 (370)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 89 
 
 m/ZEli CONNECTUK. 
 
 Type A. — This form of connector is made of nickeled steel, and should be 
 used for " clippinj; " on the buzzer wire and the 11-strand field wire. Extra 
 studs should be kept on hand for repairs. These studs screw into the con- 
 nector and may be removed If necessary. The flexible cord should not be 
 knotted up or twisted, as this tends to break it. A type A connector is shown in 
 figure S-29. 
 
 Fig. 8-29.— CONNECTOR, BUZZER, TYPE "A." 
 PIKES, WIRE. 
 
 The wire pike with model 1910 hook is shown in figure 8-30. This hook 
 is made of malleable cast iron. The upper point is bent out three-fourths inch 
 to facilitate picking up wire by mounted men. The hook proper is about one- 
 half foot in length and is carried on a staff of straight-grained hickory. The 
 complete pike is 9 feet in length. 
 
 A hook with roller is n(»w being tested, as continual use of a solid hook results 
 in the wire wearing a deep groove in the metal. 
 
 MEGAI'IIO.VE.S, FIHEIt. IS-IXCH. 
 
 The latest type of Signal Corps field megaphone is made of fiber, with 
 aluminum mouthpiece and leather handle. Tliese megaphones are IS inches 
 long and 9 inches in diameter at large end. 
 
 POLE.S. LANCE, AND IXSCLATORS. 
 
 These poles are usually made of well-seasoned, straight-grained pine or 
 cypress, and are 13 feet 11 inches from tip to tip. The diameter of the pole 
 at the butt is 2 inches, tapering to 1* inches where it enters the head. The 
 butt of the pole is shaped to a blunt point 3 inches long. The top is 
 tapered to fit in a galvanized-iron head 3f inches long. This head is threaded 
 externally to fit the ordinary glass or porcelain insulator. The end of the head 
 
 (371)
 
 90 
 
 Signal Corps Manual No. 3.— Chapter 8. 
 
 Figs. &-30.— WIRE PIKE- 
 (372)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 91 
 
 is threaded internally to receive a corresijondingly tlireaded galvanized-iron 
 rod upon which is molded a special mica composition insulator. These special 
 insulators are of two types, the only difference in them being in the type of 
 device for securing the wire. One is equipped with a bent galvanized-iron wire 
 appliance called fr<»m its shape a "pig-tail insulator." The .second is a U-shaped 
 device similarly mounted, called a " clamp insulator." The clamp insulator is 
 employed on about every tifth pole of a lance line, to prevent a longitudinal move- 
 ment of the wire, while the pig-tail insulator is used upon the other poles. The 
 lance pole weighs about 7 pounds and the galvanized-iron head with insulator 
 about 3 pounds. 
 
 STANDARD SPECIFICATIONS. 
 
 The following index to standard specifications is correct to August 1, 191G. 
 New specifications are added and old ones corrected from time to time. Those 
 marked (*) are not intended for general distribution and are not in jirinted 
 form : 
 
 A. 
 
 ♦Aeroplane tent (handmade) 527 
 
 ♦Ambulance, improved, Quartermaster specification for 446 
 
 Analysis, chemical, of rubber insulating compound 581 
 
 Anemometer 159 
 
 Apparatus, zone signal 302 
 
 ^ms, cross, wooden 177 
 
 Arresters, lightning : 229 
 
 B. 
 
 Bag, service, tool 312 
 
 ♦Balloons, captive, power winch wagon for 541 
 
 Balloons, dirigible 483 
 
 Batteries, dry, standard 221 
 
 Battery, telephone, storage 280 
 
 Battery, testing, service 185 
 
 ♦Binding posts and connectors 231 
 
 Block, terminal, telephone 438 
 
 Box, baseline, switch 455 
 
 Box, cable terminal, weatherproof ; 245 
 
 Box, outlet, for target ranges 471 
 
 Box, searchlight, outlet 297 
 
 Box, submarine cal)le terminal, unit type 533 
 
 Box, terminal, type D 441 
 
 Bracket, handset 209 
 
 Breast reel 412 
 
 Buzzers, service '. 5.55 
 
 ♦Buzzer system equipment, target range 496 
 
 Buzzer wire and sjwol for buzzer wire 387 
 
 Box, transfer switch 582 
 
 Box, standard junction . 584 
 
 C. 
 
 Cabinet, supply : 193 
 
 Cable, aerial, paper insulation, type 401 to 419 197 
 
 Cable and wire to be used in wireless telegraph work 416 
 
 1373)
 
 92 Signal Corps Manual No. 3. — Chapter 8. 
 
 Cable, deep-sea, singlt^ conductor 419 
 
 Cable, double armor, sinjile conductor, light-i , 41!) 
 
 Cable, general requirements for 554 
 
 Cable, intermediate, single conductor 419 
 
 Cable, lead-covered, rubber insulation, multiple conductor 429 
 
 Cable, multiple and single conductor, rubber insulation, submarine, F. C. 
 
 (single and double armor) 431 
 
 Cable, one pair, rubber insulation, lead sbeath, galvanized flexible steel 
 
 armor 54(5 
 
 Cable, paper insulation, submarine . 427 
 
 *Cable, Philippine, single conductor, submai'ine 424 
 
 Cable, power, rubber insulation 432 
 
 Cable, single and multiple conductor, for data transmission circuits 580 
 
 Cable splicer's chest 318 
 
 Cable, submarine, terminal box, iinit type 538 
 
 *Cable, submarine, three-conductor, armored 558 
 
 Cable, switchboard, twenty pair 290 
 
 Cable terminals, standard, submarine 386 
 
 Cable terminal box, weatherproof 245 
 
 *Cart, wire, model 1911, type H .5.52 
 
 *Cart, wire, model 1911, type I 563 
 
 *Cart, wire, model 1913, type K 573 
 
 Case, electrical instrument 145 
 
 Case, reagent, for testing electrolyte 315 
 
 Cement, Portland 391 
 
 Charging panel, storage battery , 1 .572 
 
 Chest, cable splicer's 318 
 
 Chest, construction, tool ^ 400 
 
 Chest, electrical engineer's, tool 192 
 
 Chest, mechanic's, tool 562 
 
 Chest, pipe fitter's 1 276 
 
 Chest, post tool 3.50 
 
 Compound, 30 per cent rubber insulation ^ 430 
 
 Compound, 40 per cent rul)ber insulation .583 
 
 ('om])ound, rubber liisulatioii, method of chciiiical analysis 581 
 
 Condenser, panel and bus bar 436 
 
 Conduit ^ 238 
 
 ♦Connectors, and binding posts 231 
 
 Construction material, line standard 272 
 
 Construction tools, line ! 360 
 
 Covers for motor generators and boosters 442 
 
 Cross arms, iron jxiU'S, and fittings 226 
 
 Cross arms, wooden 177 
 
 Cylinders, gas 494 
 
 D. 
 
 Distribuling frame anil jiower switclil)o;iril lor lire-control swilcliboiwd room. .571 
 
 i:. 
 
 Electrical engineer's tool chest 192 
 
 Klecfrical instrument case 145 
 
 Electrolyte, reagent case lor testing 1_ 315 
 
 (374)
 
 Technical Equipment Issued by the Signal Corps. Chapter 8. 93 
 
 Equipinont, tiivwDrks ^ 553 
 
 Equipment, pack frame, for i)ortal)le wireless telegrapli sets 561 
 
 Equipment, wireless lelegi-apli station 566 
 
 F. 
 
 Field induction telejrrapli set 370 
 
 Field telephone, artillery type, model 1912 535 
 
 *Field wireless set, waf?on, (luenclied spark type 540 
 
 Fireworks equipment 553 
 
 Firing signals 409 
 
 Fittings, iK)le line 469 
 
 Fixtures, lighting, for switchboard rooms 393 
 
 Flag kits, li-foot, 4-foot, and infantry 283 
 
 Frame, distributing, ami power switchboard for fire-control switchboartl 
 
 rr>om 571 
 
 Frame, pack equiinnent. for portable wirel(>ss t(>l('gra])h s(>ts- 561 
 
 G. 
 
 Galvanized-iron wire 82 
 
 (Jalvanizing 96 
 
 (Jalvanometers 2~H 
 
 Gas cylinder 494 
 
 (Jas-cylimler wagon 467 
 
 Geni'i'al ic(|uirciueiits for Signal Corps cable specitication 554 
 
 General requiremenl s])eciticati()n . 560 
 
 Generator, motor, for charging telephone storage battery 285 
 
 Glasses, field, Signal Corps types 263 
 
 H. 
 
 *Hangars. coiisi met ion _ 585 
 
 IlaiKllc. pay-oiil 413 
 
 Ilaiid-sci liracket : 209 
 
 Hand-reel, wire 323 
 
 Heliograph, held 246 
 
 *Hydrogen plant 449 
 
 Induction telegraph set, field 370 
 
 Inspector's pocket kit '. 186 
 
 Instrument case, electrical 145 
 
 *Insti-umciit wagon. 1907 iiatlei-n 452 
 
 Insiilaliim' coiiipouiKl. niblHT. ."id i)rr cent 430 
 
 Insulating compouiKJ. rubber. 40 iier cent 583 
 
 liisulaling conqxtund. rubber, chemical analysis of 581 
 
 J. 
 
 Junction box, standard 584 
 
 K. 
 
 Key .«;et, switch : 491 
 
 Kits, tlag, 2-foot, 4-foot, and infantry 283 
 
 Kits, inspector's, pocket : -l 186 
 
 Knife switches • ^ 368 
 
 ( :'.7o I
 
 94 Signal Corps Manual No. 3. — Chapter 8. 
 
 L. 
 
 Lance pole 376 
 
 *Lance truck. 1908 pattern 538 
 
 Lanterns, field acetylene 265 
 
 Lighting fixtures for switchboard rooms 393 
 
 Line construction material, standard 272 
 
 Line construction tools 360 
 
 Lineman's magneto testing set 306 
 
 M. 
 
 Magneto testing set, lineman's 306 
 
 Masts, 180 and 130 foot, for wireless telegraphy 530 
 
 *Mast, 80-foot, hollow sectional, type E 550 
 
 Mast, 40-foot, hollow sectional, type D 551 
 
 Material, splicing and tape 569 
 
 Material, standard line construction- __ 272 
 
 Megaphones 136 
 
 Motor generator for charging storage battery '.- 285 
 
 Molding, wood 294 
 
 O. 
 
 Ohmeter 173 
 
 Oil set and accessories 407 
 
 Outlet box for target ranges 471 
 
 Outlet box, searchlight - 297 
 
 P. 
 
 E'ack frame equipment for portable wireless teU'grai)h sets 561 
 
 Panel and bus bar condenser 436 
 
 Panel, charging, storage battery 572 
 
 Panel, station switch l 415 
 
 Panel, time-interval, switch 568 
 
 Pay-out handle 413 
 
 Pay-out reel . 91 
 
 Pipe fitter's chest - 276 
 
 ♦Plant, hydrogen 449 
 
 Pocket kit, inspector's 186 
 
 Pole line fittings -- 469 
 
 Poles, iron, iron cross arms and fittings 226 
 
 Poles, lance 376 
 
 Pole seat 377 
 
 Portland cement 391 
 
 ♦Posts, binding and (:'onnectors 231 
 
 Post tool chest 350 
 
 Preservatives, wood 570 
 
 I'rlmary battery supplies 341 
 
 R. 
 
 Ftcagent (iisc fur testing electrolyte 315 
 
 Keel, breast 412 
 
 I{eel, hand, wire 323 
 
 (376)
 
 Technical Equipment Issued by the Signal Corps. — Chapter 8. 95 
 
 Reel, pay-out 91 
 
 Keel, take-up 95 
 
 Requirements, preneral specification 560 
 
 Kuljher-insulatiiif^ conipouiul. 3t> per cent 430 
 
 Hul)l»er-insulatiny compound, 40 per cent 583 
 
 Rubber-insulating compound, method of chemical analysis of 581 
 
 S. 
 
 Seat, pole 377 
 
 Service testing battery 185 
 
 Service tool bag 312 
 
 *Set, field wireless wagon, quenched spark type 540 
 
 Set, induction, field telegraph 370 
 
 Set, portable wireless, pack frame equipment for 561 
 
 Sets, lineman's magneto testing ^ 306 
 
 Signal apparatus, zone 302 
 
 Signals, firing 409 
 
 Splicer's chest, cable 318 
 
 Spool for' buzzer wire, and buzzer wire 1 387 
 
 Station switch panel ^ 415 
 
 Storage battery, telephone 280 
 
 Storage battery, charging panel 572 
 
 Supplies, primary battery 341 
 
 Supply cabinet 193 
 
 Switches, knife 368 
 
 Switchboard, camp telephone 578 
 
 Switchboard, power, and distributing frame, for fire control switchboard 
 
 room J 571 
 
 Switchboard rooms, lighting fixtures for/ 393 
 
 Switchboard, telephone, common battery type 321 
 
 Switchboard, telephone, power 519 
 
 Switch box, base line 455 
 
 Switch key set 491 
 
 Switch boxes, transfer 582 
 
 T. 
 
 Take-up reel 95 
 
 Tape, and splicing material 569 
 
 *Target range buzzer system equipment 496 
 
 Target ranges, outlet box for 471 
 
 Telegraph set, induction, field 370 
 
 Telephone, artillery type, composite 401 
 
 Telephone, camp 577 
 
 Telephone, common battery 320 
 
 Telephone, common battery, artillery type 575 
 
 Telephone, Field Artillery 535 
 
 Telephone, local battery 361 
 
 Telephone, storage battery •_ 280 
 
 Telephone switchboard, common battery 321 
 
 *Tent, aeroplane, handmade 527 
 
 *Tent for housing dirigible balloon 497 
 
 Terminal block, telei)hone 438 
 
 (377)
 
 96 * Signal Corps Manual No. 3. — Chapter 8. 
 
 Terminal box, type D 441 
 
 Terminal boxes, cable, submarine, unit type 533 
 
 Terminal boxes, cable, weatherproof-^ 245 
 
 Terminals, cable, standard, submarine 386 
 
 Testing battery, service 185 
 
 Testing set, lineman's, magneto 306 
 
 Test, tinning, for copper wire 403 
 
 Test, tinning, for iron or steel wire 414 
 
 Thermometers, mercurial 144 
 
 Time interval switch panel 568 
 
 Tinning test for copper wire 403 
 
 Tinning test for iron or steel wire 414 
 
 Tool bag, service 312 
 
 Tool chest, construction 400 
 
 Tool chest, electrical engineer's _ 192 
 
 Tool chest, mechanic's 562 
 
 Tool chest, post 350 
 
 Tools, line construction 360 
 
 Tower, steel, for wireless telegraph station 510 
 
 ♦Transformer, testing . — 476 
 
 *Truck, lance 538 
 
 Transfer switch box 582 
 
 V. 
 
 Vane, wind 256 
 
 Vulcanizer, electric : 524 
 
 W. 
 
 ♦Wagon, gas cylinder 467 
 
 *Wagon, instrument 452 
 
 *Wagon, power winch, for captive balloons 541 
 
 *Wagon, 2-horse and 4-horse or mule (Quartermaster specification) 445 
 
 *Watch, stop 308 
 
 Watch, wrist 579 
 
 Wind vane 256 
 
 Wires and cables to be used in wireless telegraph work 416 
 
 Wire, buzzer, and spool for buzzer wire 387 
 
 Wire, copper, line 79 
 
 Wire, field, 11-strand 408 
 
 Wire, field, twin conductor, mountain artillery type 548 
 
 Wire, galvanized iron 82 
 
 *Wire, hard drawn, weatherproof, copper _ 307 
 
 Wire, inside twisted pair, pot-head and bridle 340 
 
 Wire, No. 17 gauge, copper clad steel, twisted pair, outside distributing-. 557 
 
 Wire, oflice, single, inside 418 
 
 Wire, outside twisted pair, copper conductors 396 
 
 Wire, pot-head, inside twisted pair and bridle 340 
 
 Wire, single, inside, office 418 
 
 Wire, single, rubber covered and braided 474 
 
 ♦Wire, standard electrical condu<'tors 576 
 
 ♦Wire, weatherproof, hard-drawn copper 307 
 
 (378)
 
 Technical Equipment Issued by tlic Signal Corps. Chapter 8. 97 
 
 Wire, zone signal ^ 351 
 
 "■Wireless set, Held wnfxoii, quenched sjiark type 540 
 
 *Wireless sets, portal)le i)ack Iraiiic eciuipment for 561 
 
 Wireless lolc.ixrapli station e»iuii»iiient 566 
 
 Wireless telegraph station, steel tower for 510 
 
 Wireless work, wire and cable to be used 416 
 
 Wooden (;ross arms 177 
 
 Wood molding 294 
 
 Wood preservatives 570 
 
 Z. 
 
 /one signal apparatus 302 
 
 Zone signal wire 351 
 
 An enumeration of all Signal Corps blank forms may be found in Signal 
 Corps Manual No. 7, latest edition. 
 
 40581"— 17 25 (379)
 
 Chapter 9. 
 MISCELLANEOUS TESTS AND GENERAL INFORMATION. 
 
 MISCELLANEOUS TESTS. 
 
 The importance of testinjr, hoth for regularly ascertaining the condition of the 
 lines with a view to anticipating breakdowns and as a means of locating faults 
 when they occur, is something that should he recognized by all ofticers and 
 enlisted men on duty in connection with maintenance of Signal Corps installa- 
 tions. 
 
 The following notes on cable testing and the location of faults where accurate 
 instrumeids are not availal)le will be found of great value where apparatus must 
 be improvised. 
 
 The extensive use of short subterranean and submarine cables for tire-control, 
 post-telephone, and submarine-mine systems generally, makes some method 
 of easy testing desirable. A'ery often testing sets are not on hand. If on 
 hand, they may be out of order or there may be nobody available who is sufTi- 
 ciently skilled in their use for location of faults. By far the most common class 
 of faults is that due to defects in insulation. It is desirable to locate these in 
 submarine cables, and very necessary in case of multiple-core cables buried in 
 trenches or drawn into conduits, which, of course, prevents their being readily 
 taken up for examination. 
 
 In the absence of better instruments, a fairly good idea of the insulation re- 
 sistance of a cable may be arrived at by means of a battery and telephone 
 receiver, as follows : 
 
 A telephone receiver (T) (tig. 9-1) is connected with the battery (B) of a 
 few cells, the latter being connected with the cable armor at C. A well-insu- 
 lated wire (/) is connected with the other terminal of the telephone. The ends 
 of the conductor are prepared and insulated as above described. When the end 
 of / is touched on the cable conductor a click is heard in the receiver. If after 
 about one second it is touched again and no click is heard in the receiver, the 
 insulation resistance, if one cell of battery is used, is above about 50 megohms ; 
 if two cells of battery, 100 megohms, ami so on, for about the proportion of cells. 
 
 The click produce*! on first contact is due to the current rushing in to charge 
 the cable ; and if the insulation is good, in one second so small an amount of 
 this charge will be lost by leakage that little or no sound will be produced 
 by subsequent contacts, as cable will still be charged. Care should be taken 
 that wire / and telephone terminal attached to it are well insulated, other- 
 wise leakage from them may give false indications. 
 
 Having found the faulty conductors, the location of these faults may then 
 he proceeded with by the method suggested below (figs. 9-2 and 9-3). It is 
 applicable to cables having two or more similar conductors, or to a single- 
 conductor cable when both ends are available, as when it is coiled in a tank or 
 on a reel. It is the ^Murray loop test with a " slide wire " in which simple 
 relations of resistance to lengths exist, owing to the uniformity of resistance 
 along the wires in the cable conductors and slide wires, respectively. It is, 
 in fact, a combination of several well-known instrument methods, 
 
 (381) 1
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 Fig. 9-1.— TEST, EMERGENCY, INSULATION. 
 
 To prevent serious errors care must be taken that oih> of tlie conductors in 
 this test has sound insulation. 
 
 No resistance measurements are involved, and the only apparatus required 
 is a few cells of battery, a telephone receiver, and from 10 to 50 feet of bare 
 resistance wire. Of this latter about No. 28 " Climax " or " S. B." wire is 
 suitable. However, if resistance wire is not to be had, fair results may be 
 obtained by using No. 36 bare copinn- wire. 
 
 ■Y- 
 
 Flg. 9-2.— TEST, LOCATION OF FAULTS WITH IMPROVISED APPARATUS, USING A 
 
 TELEPHONE RECEIVER. 
 
 I''ii-st taking liic case of a nniltiple-conductor cable, say .'?,()()<) yards l(»ng. in 
 whicli tiicrc arc one or more (-(inductors witli delVctive insulalidii and at least 
 one good one. .loin tlic (Idcil ivc imc tn be Icslcd Willi liic gdiKl inic .-it th(> 
 djslani ciKJ. Di-ivc two sni;ill liriglil nails (.1 and (' in lig. 1» "J) (•(.nvcMiciil to 
 (lie terminals ol' the ( (•ndudors ;il the testing end and stretch froni tlie.se a 
 
 (382)
 
 Miscellaneous Tests and General Information. — Chapter 9. 3 
 
 piece of the resistance wire aiduiid another nail (D) and bade, malving each 
 equal branch of tlie wire A I) and C D of sucli a lengtli as to be some exact 
 subnuiltiple of tlie length of the cable being tested. For example, have each 
 branch of the wire in this case three thousand thirty-seconds of an inch long, 
 or ^^ (93.7")) inches. Join one of the two nails at the end of the cable termi- 
 nals to the defective cable conductor, the other nail to the good conductor. 
 Join one terminal of the telephone receiver li to the ground and the other 
 terminal to a short wire, which will be used as a " searcher." Connect a few 
 cells of battery B across the nails to which the cable terminals are attached. 
 Now, putting the telephone receiver to the ear, feel along the resistance wire, 
 which is attached to the defective conductor, with the searcher wire attached 
 to the telephone. A point G will be found where the frying sound produced in 
 the telephone will cease, and if the searcher wire be moved either way from 
 this it will again become audible. Mark this point on the resistance wire, re- 
 verse the connections of the battery, and again find the point of silence. If it 
 is not coincident with the first, take the mean position between them. 
 
 The distance of this point G, in thirty-seconds of an inch, from the nail C 
 to which the defective cable terminal is attached, is the distance in yards from 
 the cable terminal to the fault. 
 
 It is evident that for short cables greater accuracy is .secured by taking 
 larger representative units in proportion for the resistance wires. For ex- 
 ample, if the cable were 1.250 yards long, the units on the resistance wires 
 could be sixteenths, and the wires be convenient in length: ^[f|^=TSJ inche.s. 
 
 Care should be taken to stretch the resistance wires evenly and not wrap the 
 loose ends back on the stretched portion, as that would destroy the uniformity 
 of resistances throughout the length on which the assumed proportion depends. 
 
 In testing a defective single-conductor cable the two ends are joined to the 
 resistance wire, as just stated, the tchole length of the resistance wire being 
 in some simple proportion to the length of the cable. 
 
 For example, if the cable is 1,980 yards long, the whole length of the re- 
 sistance wire would be ^f-f^ or ^^ inches, as desii'ed — the greater length 
 giving tlie result with greater accuracy. It will be readily seen that this and 
 the former case are identical, as the " loop " formed by joining the distant 
 ends of two multiple conductors is in this case replaced by the " loop " of the 
 single conductor. 
 
 The method of securing ends of wires by nails is given to show with what 
 ease and simplicity the necessary parts for the test may be set up. But even 
 roughly and hastily set up, the test will locate faults with surprising accu- 
 racy if a sufficient length of resistance wire be used to eliminate small acci- 
 dental irregularities in attachments of wires. 
 
 The test is a simple application of the Wheatstone bridge principle. It 
 may be of interest to trace this out (fig. 9-2). 
 
 A K and C K are the two cable conductors joined at the distant end K. 
 The lower one is defective at some unknown point H. The resistance wire 
 A D C is joined np as shown with the cable conductors and battery B. The 
 point of silence in the telephone is found at G. The Wheatstone bridge rela- 
 tion of resistances then exists in the lengths of the wire, X :Y : -.E -.F. And 
 since these resistances are along uniform wires the same relations exist be- 
 tween IcniitJis as between resistanrcs. Consequently E can be read off di- 
 rectly in the terms of A' if the lengths .1 D and C D are laid off numerically 
 equal to A K and C K. 
 
 The foregoing method involves no computation. It is evident from the 
 above proportion that if the entire length of resistance wire were made 
 
 (383)
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 some even number of any convenient nnit (say sixteenths of an inch) that 
 a substitution of values in the proportion would give the distances. For 
 example, if the resistance wire had a length of 1,000 and balance were found 
 at 432 from the end to which the faulty conductor was attached, the distance 
 to the fault would be 432/1,000 of the entire length of the conductors, or 
 432/1,000X2 of the length of the eable from the testing point. 
 
 By this method, involving simple computations, the same wire stretched on 
 a convenient board may be iised for all measurements. It becomes in effect 
 an ohmmeter. 
 
 If more than one faulty place exists in the conductor, the test will give 
 approximately the mean position. So, having made the test and cut the cable 
 at the indicated place, test both ways to ascertain if both parts are not de- 
 fective. If sound toward either station, the fault should be relocated in the 
 defective part. 
 
 It will probably be found near the position of the tirst cut and, having allowed 
 a reasonable percentage error, on the second cut it is highly probable the faulty 
 section will be cut otf. It has been found that generally the error of determi- 
 nation will fall within 1 per cent. 
 
 ■O 
 
 Fig. 9-3.— TEST, LOCATION OF FAULTS WITH IMPROVISED APPARATUS, USING A 
 
 GALVANOMETER. 
 
 A word may be said regarding the telephone receiver as a detector of feeble 
 currents. It is much more .sensitive than the average pivoted galvanometer and 
 will stand infinitely more abuse. However, in noisy places Uie galvanometer 
 may be substituted for the telephone in this test. 
 
 If the fault has a high resistance, so that the four or five cells of battery 
 perimssible in tlie manner of connecting .shown in diagram can not send .sufR- 
 <-ient current through, then some form of rather sensitive galvanometer becomes 
 necessary with the increased battery and change of connections recpiired. In 
 place of the battery in figure 9-2, connect the galvanometer. In i)lace of the 
 telephone receiver, connect a battery of from 20 to 100 cells in series. Then 
 proceed as with the telei)hone receiver, noting that for each break or irregularity 
 of contact of the searcher wire there may be n kick of the galvanometer, due 
 to capacity or inductance, and that l)alance is obtained only when the galvanom- 
 eter .shows no deflection when the searcher wire is at rest. (Fig. 9-3.) 
 
 A fault in a single conductor cable, or one involving all the conductors of a 
 multiple cable, may be located if two additional wires of sound insulation 
 between the p«>ints connected by the faulty cable are available. 
 
 As the lengths and resistances of these wires are immaterial, temporary or 
 roundabout wires may be utilized. 
 
 (384)
 
 Miscellaneous Tests and General Information. — Chapter 9. 5 
 
 Tlic nicdiod of jirocodurc is ;is follows: Strotfli a sinj:;U' piece of resistance 
 wire y\ li ( fi^riires 9-4 aiul \)-~>) wliose leiifrth is some even number of parts, say. 
 1,000 sixteenths of an incli. Tlie two sound outside wires / and A' and flie d«'- 
 fective one /> are c(»nnected at tlie distant end. The fjalvanometer, i)attery. and 
 searcher are connected, as sliown in fij^ure 9—1, and tlie point of balance ob- 
 tained. Call the reading A from the point C. 
 
 Fig. 9-4.— TEST, LOCATION OF FAULTS WITH IMPROVISED APPARATUS, ALL CON- 
 DUCTORS FAULTY. 
 
 Then connect up as in figure 9-5, joining the battery to earth -or to tlie cable 
 sheath. If the fault appears as a leak between two adjacent wires of the 
 multiple cable, the lower end of the battery should be joined to the other faulty 
 wire instead of the cable sheath or ground. 
 
 Fig. 9-5.— TEST, LOCATION OF FAULTS WITH IMPROVISED APPARATUS, ALL CON- 
 DUCTORS FAULTY. 
 
 (385)
 
 6 Signal Corps Manual No. 3. — Chapter 9. 
 
 WIkmi hMliUici' is (il>t:iiiU'(l. note llic leading on tlic rcsisliincc wire from i)()iiit 
 
 ('. Call it A'. Then if lenjrtli of rauity roiiductor is J. ftvt, tlic distant' of the 
 
 A' L 
 fault from C is — r— feet. 
 A 
 
 This method is particularly applicable to paper cables where a leak has iimile 
 
 the insulation of all the conductors faulty. 
 
 Location of break in conductor. — The method applicable when the wire is 
 broken inside the insulation, leaving the latter intact, is given below. This is 
 the character of the fault generally produced when a conductor parts in a 
 paper-insulation cable. Owing to the small capat-ity of this kind of cable 
 the method is useful because of the practical difficulty in getting correct 
 capacity values by galvanometer methods in small lengths of this cable. 
 
 The connections for the test are the same as that described in figure 9-3, 
 except the telephone receiver is used in place of the galvanometer. The point 
 H, instead of representing a fault in insulation, in this case represents the 
 location of a break in the wire. It is best to use quite a number of cells, say 20 
 or 30, if available. The battery circuit is reversed and interrupted rapidly while 
 a point is sought with the searcher along the resistance wire where the clicks 
 are no longer heard in the receiver. When this point of balance is reached the 
 distance to the break is then read off on the scale along the resistance wire 
 from C to the point 6', as explained in locating insulation faults.' In this case 
 the point G is in the corresponding position on the upper wire. The reason for 
 this is that this wire having the greater capacity is charged lln-ough the bridge 
 arm having the lower resistance. 
 
 Fig. 9-6.— TEST, LOCATION OF FAULTS WITH IMPROVISED APPARATUS, CON DUCTOR 
 
 PARTED. 
 
 In the last-named test an interru])led current of rather high voltage is re- 
 quired. A method of getting this with only two (h-y cells is to take a local bat- 
 tery telephone induction coil (/ in the ligure) and allach it to a wooden base, 
 together with an ordinary small nu^tal buzzer " />'." 
 
 The connections ai-e as shown in tigure D-C). When I lie battery is connected 
 tlie buzzer sends a vibratory current through the piiniary coll. .\ vibrat(»ry 
 iiiiTcnt of nnich higher voltage is induced in the secondary, and this is utilized 
 in place of the ballery cun-eiils. as shown in the ror-egoiiig tests. 
 
 IIIK \(>I.I'.MK'1KK AM) A M M K I'Ki:. 
 
 On land telegrai»li lines and the aiii>aratus connected therewith the electrical 
 
 uruls with wbicli we are usually concei-ned in nieasureinenls an<l tests are those 
 
 given in Ohm's law — the current in amperes (Miuals the electromotive force in 
 
 volts divided by the resistance of the circuit in ohms; expre.ssed algebraically, 
 
 E 
 ^—jy The galvanometer, in one or the other of its foiMus, measures current. 
 
 When of low resi.stance and graduated properly, it is called an amju'remeter or 
 annneler. When of high resistance, since the current llowing through it is prac- 
 tically indejiendent of I he relatively small variations of outsiile I'esislunce, Ww
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 Kalviiiiuiiu'ter n'Mdinjis arc dii'cctly iiroiHirtioiiiil lo llic ck-rtruiiiDl ivc! force E. 
 And when properly f^raduated it becomes a voltmeter. The ammeter and volt- 
 meter, on account of portability and quickness and accuracy with which read- 
 
 Pig. 9_7._TEST, measuring OHMIC RESISTANCE BY MEANS OF VOLTMETER AND 
 
 MILLIAMMETER. 
 
 ings are taken, are very satisfactory Instruments for telegraph testing. It is 
 evident if / and E are measured by an ammeter and voltmeter, respectively, 
 
 that It becomes known — for according to Ohm's law R= j. For example, if we 
 
 connect the ammeter A, battery B, and a resistance coil C together, as in figure 
 9-7, we may read the current flowing. The small current commonly used in 
 telegraphy is conveniently expressed in milliamperes, and the ammeter grad- 
 uated for these is called the milli- or mil-ammeter. If we attach a voltmeter V 
 to the terminals <»f the resistance coil C\ it will give the difference of potential 
 (E. M. F. ) produced at these two points l)y the current flowing between them. 
 
 .Suppose the milliammeter reads 28 milliamperes (0.()2S ampere) and the volt- 
 meter 4.23 volt.>^ 
 
 JP 4 OQ 
 
 Substituting in /? == , /? = --^=151 ohms. The general rule 
 1 . U2o 
 
 in connecting up the annneler and voltmeter for such measurements is to put the 
 annn«>ter in the circuit, and the voltmeter shunting the part of the circuit whose 
 resistance is desired. The lU'actical use of the instruments in testing telegraph 
 lines is given below. 
 
 The theoreticid connections are shown in figure 9-S, the voltmeter being c«»n- 
 nected in shunt to line and ground, and the milliaunneter in series in tlie circuit. 
 
 HA/£ 
 
 -y^if&^fs» 
 
 '^fffl^- " 
 
 Fig. 9-8.— TEST, MEASURING OHMIC RESISTANCE OF TELEGRAPH LINE BY MEANS 
 OF VOLTMETER AND MILLIAMMETER. 
 
 (387)
 
 8 
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 The correspondence of this with figure 9-7 will he noted. Tlie practical con- 
 nections are shown in figure 9-9. 
 
 A portable voltmeter I'eading to 200 volts (D. aiid luillianinieler reading to 
 150 millianiperes (-1), are mounted on a Ijoard and connected with tlie regular 
 switchboard cord and wedge, as shown, the other terminal of the voltmeter 
 being connected with the ground. 
 
 When the wedge is inserted in any line spring jack, the ammeter is con- 
 nected in the circuit and the voltmeter slumted to the groiind, as shown in 
 figure 9-9. The deflections of tlie ammeter and the voltmeter thus give / and E 
 
 in the formula R =y and the resistance becomes Icnown. 
 
 TO GJfOC/^O 
 
 Pig. 9_9. —TEST, MEASURING OHMIC RESISTANCE OF TELEGRAPH LINE BY MEANS 
 OF VOLTMETER AND M I LLIAM M ETER, PRACTICAL CONNECTIONS. 
 
 To test, cut off battery at most distant station, ground line, and take read- 
 ings. Now open the key for a few seconds and take a second set of readings. 
 Repeat this process with all stations up to the nearest one. The readings 
 with stations grtmnded give resistance of line (including relay) to each, while 
 readings with tlie keys opened would give the insulation resistance to each. 
 
 The following shows some methods of using the voltmeter alone for various 
 measurements when the ammeter is not available: 
 
 THH VOl.T.METER (O-'i, 0-150 VOI.TS P.^TTKRN). 
 
 This instrument is a galvanometer of the D'Arsonval class, in which a pivoted 
 coil, controlled by a spiral spring turning in jeweled bearings, carries a light 
 nluminnm pointer moving over an equally divided scale. 
 
 Fig. 9-10.— TEST, WITH VOLTMETER, VOLTAGE OF A BATTERY. 
 
 This coil turns, when a current passes llirougli it, in llie strong field between 
 the poles of a powerful permanent magnet. In the base are two resistance 
 coils, one or the other of which is always in .series with the movable coil, 
 dejtending ui)on which scale is used — the IHO or 5 volt .scale. 
 
 Ciiiition. — To i>revent l)ending the i)ointer by violeid action, always test first 
 with the l.^iO-volt scale. If the jioinfer indicates less llian .^> volts, use the other 
 binding iiost and take advantage of the greater accuracy of the 5-volt scale. 
 
 (388)
 
 Miscellaneous Tests and General Information. — Chapter 9. 9 
 
 TO TEST TUE VOLTAGE OF A BAT'lERY oF A NUMBER OF CELLS. 
 
 Use the 150-v()lt scale and connect up as shown (fig. 9-10). 
 For not more than .'} sal aiiiiiioiiiac, 4 l)hH'slone. or 2 storajic colls in .series 
 use the 5-voIt scale. 
 
 Fig. 9-n.— TEST, WITH VOLTMETER, DIFFERENCE OF POTENTIAL BETWEEN TWO 
 
 POINTS ON WIRE. 
 
 TO MEASrRE THE DIFFERENCE OF POTENTIAL (PRESSURE) BETWEEN ANY TWO POINTS OF A 
 WIRE OR EXTREMITIES OF A COIL CARRYING A CURRENT. 
 
 The connections indicated in figures 9-11 and 9-12 would give the differences 
 of potential at the two points on the wire, or at the extremities of the coil, 
 respectively. 
 
 Fig. 9-12.— TEST, WITH VOLTMETER, DIFFERENCE OF POTENTIAL AT EXTREMITIES 
 
 OF A COIL. 
 
 TO MEASURE A RESISTANCE. 
 
 To measure a resistance less than 3.000 ohms use two or three dry or Gonda 
 cells in series, get their voltage, using the o-volt scale. Call this V. Then con- 
 nect up with the unknown resi.stance X (fig. 9-13), as shown, and call this 
 scale reading V. 
 
 The resistance of the volmetcr, using .Vvolr .scale, is given in the sliding cover 
 of box. Call this R. 
 
 Then 
 
 R(V-n 
 V 
 
 This is very inaccurate for resistances of only a few ohms unless the resist- 
 ance of the battery is taken into account. 
 
 (389)
 
 10 
 
 signal Corps Meinual No. 3. — Chapter 9. 
 
 In measuring resistances from 3,000 to 1250,(KH) olnns use tlie 150 scale, noting 
 tlie value of R given on tlie cover for tliis. The same connections and formula 
 are applicable. 
 
 imii-. 
 
 Fig. 9-13.— TEST, WITH VOLTMETER, TO MEASURE OHMIC RESISTANCE. 
 
 To secure greater acciiracy in either of above cases, tlie battery should have 
 sufficient E M F to bring the value of V as near 5 or 150 as practicable. 
 
 Example. — (1) Using 5- volt scale. Resistance to be measured (A') is an 
 ordinary telegraph relay magnet. 
 
 Suppo.se i?=520. Three cells dry battei-y in series give T=4.35 volts. When 
 X is connected in. T^'=3.40. 
 
 Then 
 
 ^ 520(4.35-3.40) ^^^ „„ , 
 X= ^^^0 =145. 29 ohms. 
 
 (2) Using 150-volt scale. Determine the insulation resistance of 110-volt 
 storage battery (leakage from either pole of battery, or its connections, to 
 earth ) . 
 
 Suppose 7»' for this scale=15,o00 ohms. Voltage across terminals, V=110 
 volts; voltage between (tne of the terminals and eartli (T')=12 volts. 
 
 „ 15.500(110-12) ,„„,„„ , 
 A= ^j2 ^=126,583 ohms. 
 
 This would indicate a slight leak, probably at or neai- llu' negative end of 
 battery if the tests were made at the positive terminal. 
 
 If some coils of known re.sistance ai-e available, rcsistamcs (-m lie measured 
 more accurately as follows : 
 
 The known coil and the resistance to be measured, marked respectively 
 r and x, are connected with each other and a battery, as shown (tig. 9-14). 
 The voltmeter is connected first as indicated by the full and then as by the 
 broken lines. If the voltage indicated in the first ca.se is /■-' and in the second 
 it is /■;', 
 
 E'r 
 
 E.T<y ■.-.r-.x. :.x = - 
 
 E 
 
 I'se enough battery to make a good rcadnlile dellection, and if several known 
 coils are available use the one which is somewhere near the resistance to be 
 measured. 
 
 Example. — Known coil, 10 ohms. \'olt meter shunt iiig this gave 3.2 volts, and 
 shunting the unknown gave 4.7 volts. Hence 
 
 x='^'^><}^.=14,7 ohm.s. 
 3.2 
 
 (390)
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 11 
 
 Fig. 9-14.— TEST, WITH VOLTMETER, TO MEASURE OHMIC RESISTANCE, USING A 
 
 KNOWN RESISTANCE. 
 
 TO MEASURE CIRKE.NT WITH THK VuLTMETEK. 
 
 If we know the resistance of a wire or foil, and liave a steady current flowing 
 through it, tlie voltmeter wires applied at tlu' terminals of the wire or coil will 
 
 give a certain deliection, E. Hence, since ■-^=r,. if \v« substitute for /v and It 
 
 the known values we get /. (Connections shown in figs. 9-11 and 0-12.) 
 
 Example. — A certain current is flowing through a 4-ohm telegraph .sounder. 
 
 When the wires from the voltmeter (5-volt scale) arei connected at sounder 
 
 binding jiosts, the voltmeter indicates 0.8 volt. 
 Substituting as above, 
 
 c 
 
 /=— =.2 ampere. 
 
 TO RIEASIIIE THE INTEUXAL I.ESISTAXCE OF A BATTERY. 
 
 Using the H-volt scale, first take the voltage of the cell. Then take the 
 voltage at the terminals of a coil of rather low resistance (a 4-ohm sounder, 
 for instance), in circuit with the cell (fig. I)-12). being careful not to close 
 battery circuit until ready to read the voltmeter. Multiply the voltage of the 
 cell by the resistance of the coil and divide by the voltage at terminals of 
 coil. From the result subtract the resistance of the coil. The remainder is 
 ihe internal resistance sought. 
 
 Example. — The voltage of a dry cell is' 1.41, and the voltage at terminals of 
 4-ohm sounder in circuit with the cell is 1.24. 
 
 1.41X4h-1.24=4.5. 
 
 4..") — !=..") ohm, internal resistance of cell. Care must be tr.ken to read 
 voltmeter quickly after closing the circuit through coil, or the result will be 
 vitiated by the polarization of the cell. 
 
 The internal resistance of a dry cell can al.so be determined by the use of 
 the voltammeter previously descrii)ed. The method of yroceilure in this test 
 is as follows : 
 
 (391)
 
 12 
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 Never connect with more than one storage cell or more than three of other 
 kinds. Too large a current or high voltage will bend the indicator or burn 
 out the coils. 
 
 Dry batteries and sal-ammoniac batteries (such as Leclanche, donda. etc.) 
 should have voltages between 1.4 and 1.5. This is obtained by connecting 
 with binding posts V, P being positive. Then, by connecting with A instead 
 of T. the current is indicated on the ampere scale. Since the resistance of the 
 ampere coils is 0..5 ohm. the internal resistance of the cell is given by the for- 
 mula :^^ where £'=voltage of the cell and /=current in amperes. The 
 
 deterioration of a dry or sal-ammoniac battery is shown by a fall in voltage 
 much below 1.4 and a rise in its internal resistance. This latter should not 
 exceed a few ohms. 
 
 The voltage of a bluestone cell is ordinarily about 1. Its internal resistance 
 after it is in good working order should not exceed 3 ohms. 
 
 The voltage of a storage cell varies between l.S when al)out discharged to 
 2.5 when being charged fully. After charge it is about '1. Tlie internal 
 resistance should be very small. 
 
 Edison primary type V and Gordon cells have about 0.7.") volt E. M. F. and 
 internal resistances from .06 to .25 ohm. 
 
 Fuller cells (with electropoion fluid) have from LS to 2 volts E. M. F. and 
 an internal resistance varying from one-fourth to one-half ohm. A table of 
 internal resistances should be made out for the class of batteries to be tested 
 to save computations in making the round of inspections. 
 
 In this connection the following table of internal resistance is supplied : 
 
 Type of cell. Ohms. 
 
 Leclanche and Gonda 1. 50 
 
 Samson . 25 
 
 Gravity 3. 00 
 
 Edison primary type V and Gor- 
 don . 10 
 
 Type of cell. Ohms. 
 
 4-0 dry 0.25 
 
 4 dry___ 
 
 5 dry___ 
 
 6 dry._^ 
 
 7 dry 
 
 8 dry___ 
 
 25 
 20 
 20 
 12 
 10 
 
 Storage cell .005 
 
 Fuller , 25 
 
 THE WHEATSTONE KKIDGE. 
 
 This has long maintained its position as the best means for measuring resist- 
 ances, and in one or the other of its various forms can be used for a great range 
 of measurements. 
 
 Fig. 9-15.— TEST, OHMIC RESISTANCE, FALL OF POTENTIAL. 
 (392)
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 13 
 
 The " fall-of-potoutial " principle is applied, wiiicli may be illustrated as 
 follows (fig. 9-15) : 
 
 If a current is tlowing alonj; a wire in the direction ol' .1 B, and the ter- 
 minals of a voltmeter V are applied at -l and li, a certain potential difference 
 between these points will be indicated; that is, there will be a fall of potential 
 from A to B, which will be miiform if the wire is of uniform resistance. This 
 may be represented jiraphically, for if the height of A C represents the total 
 difference of potential, and the line C li represents the fall of this to B along 
 the uniform wire, then at any point, say at E, the height J> E will represent 
 the potential difference between H and E, which is proportional to the length 
 of wire or resistance remaining. 
 
 If we take a circuit divided at A (fig. 9-16), the fall of potential along the 
 wire .1 E B is equal to that along the wire .1 G' B, and having passed over a 
 certain proportion of the total resistance A E B we reach a point E which will 
 be of the same potential as some jxtint (!', of A C!' B. If E and G' be connected 
 through a giilvanometi'r no current will flow through the galvanometer. It can 
 be proven that when the resistances of the divided circuit bear the proportion — 
 A E:A G' : : E B:G' B — the points E and G' are at the same potential with 
 respect to each other, and the galvanometer will not be deflected. 
 
 Fig. 9-16.— TEST, PRINCIPLE EMPLOYED IN WHEATSTONE BRIDGE. 
 
 The relation of parts in the conventional diagram of the Wheatstone bridge 
 (fig. 9-17) will now be apparent. If the resistance in the coils of .1 and B are 
 equal or bear any other simple numerical relation, then the same numerical rela- 
 tion exists between R and -Y, and if /? be a box of known resistance coils, 
 X, the unknown resistance, becomes known from the above-stated relation 
 A:B: : R: X. 
 
 Fig. 9-17.— TEST, WHEATSTONE BRIDGE, CONVENTIONAL DIAGRAM. 
 
 (393)
 
 14 
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 If we straighten out A and B and bend up A' into compact form, insert keys 
 into tlie galvanometer and battery circuits, we shall have, the diagram of the or- 
 dinary or "post-office" form of the bridge (fig. 9-18). The resistance in the 
 " balance arm " A and B, and in R are short-circuited ))y inserting the plugs, 
 and they are introduced by withdrawing the plugs. The galvanometer now most 
 usually employed is some sensitive form of the suspended-coil type. 
 
 Fig. 9-18.— TEST, WHEATSTONE BRIDGE, CIRCUITS, DIAGRAMMATIC. 
 
 The simplest measurement is made with A and B equal. Start out with, say, 
 A and B 100 ohms each. Then connect up the terminals of the unknown re- 
 sistance X ("line" and "ground"), and closing the battery key, tap the gal- 
 vanometer key. There being no resistance unplugged in R, the galvanometer 
 needle will be deflected to the side indicating " too small" for R. Now unplug in 
 R and test until the right amount is unplugged in R to get a balance or no de- 
 flection, then, since A=B, R—X. If fractional ohms are to be obtained, A 
 must be 10 or 100 times greater than B; then R is 10 or 100 times greater than 
 
 Fig. 9-19. -TEST, WHEATSTONE BRIDGE, POST-OFFICE FORM. 
 
 .V. Likewise, if X is greater liiaii ciin \iv (>l)l:iiii(Ml by inipliigging in A', tiien 
 make !{ llie greater and it r(>verses (lie nniltipiier. Practice and care are 
 r('<niisit»' to obtain acfurate results. Always close battery key befor<' galvanom- 
 eter key Mild njien galvanometer key first. / 
 
 (.394)
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 15 
 
 In nieasurlnfr resistances of n tele.uraph line be certain all line batteries are 
 disconnected before inaliinji tlie measurement. The line is connected with one of 
 the X binding posts, tlie ground to the otiier. (See tig. li-lS. ) 
 
 Many motlifications of tliis form of bridge are in u.se. Some are arranged so 
 the plugs are in.serted at the points where the introduction of resistance 
 marked Is desired. 
 
 One of the familiar forms in which the bridge is made for laboratory use is 
 shown in figure 9-19. In this the resistances are introduced by taking out 
 plugs. The further row of strips are for the .1 and It arms, the other rows 
 constituting the R arm. The keys are for introducing battery and galvanometer 
 into circuit. 
 
 The following gra])hical demonstration of the stated i)roportiunality of the 
 resistances in the four arms of the Wheatstone bridge when balance is obtained 
 is of interest in connection with the foregoing: 
 
 /o/fs 
 
 k 
 
 x^ 
 
 
 
 
 ■ \ 
 
 V 
 
 ^XZ7 
 
 ' 
 
 
 - 
 
 |\ 
 
 \ 
 
 
 
 A 
 
 . :^ , 
 
 \l, 
 
 \ 
 
 /^ 
 
 O^^nS 
 
 Fig. 9-20.— TEST, WHEATSTONE BRIDGE. GRAPHICAL DEMONSTRATION. 
 
 Lay off .1 U to represent the resistance in the upper lirancli of the lu'idge 
 (fig. 9-20) and A F to repi'Psent resistances in the lower. Let A C represent 
 the difference in potential bet\\"een the two ends of the bridge, and draw lines 
 C B and C F. These are the " fall of potential " lines along the upper and 
 lower branches I'esix'Ctlvely. 
 
 A horizontal line H I) touches points // and D at the same potential. These 
 l»ro.iected on lower lines represent the points of galvanometer connection. The 
 resistances passed over in lower and upper branches to reach these points of 
 equal potential, measured on the lower line, are .1 G and A E. 
 
 Similar triangles give these proportions : 
 
 r D:D B: 
 V H:H F. 
 
 c n-.n B: 
 
 A E:E B: 
 A E:A G: 
 
 : .1 /;: /; n 
 
 .A G: G F 
 C H:H F 
 A G:G F 
 E B:G F 
 
 F and li being at the same point in the convenrional diagram of the bridge 
 (fig. 9-16). the last proportion will be seen to be identical with that accom- 
 pijnying that figure. 
 
 46581°— IT 26 (395)
 
 16 Signal Corps Manual No. 3. — Chapter 9. 
 
 The wide range of resistances tlaat can be measured witli a Wlieatstone 
 bridge has caused it to be liliened to a pair of scales whicli may be converted 
 from hay scales to a chemical balance. It has been noted that when the 
 " balance arms " are equal the resistances of standard coils and measured re- 
 .sistances are equal ; and by changing the ratio of these balance arms, which 
 correspond to shifting the fulcrum in the steelyard, the standard resistance may 
 be made to bear any desired ratio to the measured i-esistance. 
 
 VOLTAMMETER, PORTABLE. 
 
 Figure 9-21 shows the Weston model 280 voltaunueter which is issued by the 
 Signal Corps. The instrument is furnished in a noat leather case with carrying 
 strap and is triple range, both as an anuneter and as a voltmeter. The scale 
 reading as an annneter being 0-3, O-l-^, and 0-30, the scale readings as a 
 voltmeter are 0-3, 0-15, and 0-150. One binding post is conunon for l)oth 
 ammeter and voltmeter connection, and the various scale connections are ob- 
 tained by connecting other lead to proper one of six other binding posts 
 mounted on base of instrument. All binding posts are appropriately marked. 
 
 Fig. 9-21. ^VOLTAMMETER, PORTABLE. 
 
 JlETIIOl) OF LOCATING lAll.T.S IN Mri.Tll'I.K COA'DITTOK CAIU.KS Wmi JlODKl, ItlOt 
 
 OHM METER. 
 
 Arrange to have the dislnni (>nd of (lie faulty conductor connected to n sound 
 conductor in tlic same cable. Attach tlie faulty conductor to i)ost .\ , on the 
 (thmmetcr and the sctund conductor to post Q. See that the varial)lt' plug is 
 not inserted at either 10 or 100. Attach a ground wire to X-. Find a balance 
 as in testing for copper resistance. If the reading, in scale parts, is A and the 
 length of the cable, in feet, is L, the distance to the fault will be Ij nniltii)lied 
 by 2.1 divided by 1,000. These values hold for any size cal)ie but assume that 
 tiie conduct(trs used are of tlic same gauge. Tlic connections ;irc shown in 
 ligure !) 22. 
 
 The following cxaniplc will indicate llie method of maUing this test : 
 Supi)ose connections have been made as above and the stylus is at l.'K) on the 
 scale when a bulauce has l)een obtained. Suppo.se the cable to be G,000 feet 
 
 (.396)
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 17 
 
 long; 6,000 multiplied by 300 will equal 1,800,(K)0, wliich divided by 1,000 
 equals 1,800 feet, the distance from the observer to the fault. 
 
 Fig. 9-22.— TEST, OHMMETER, LOCATION OF GROUNDS. 
 LOCATION OF A CROSS BY MEANS OF THE VOLTMETER. 
 
 In general the resistance of the wire to the cross and through the point of 
 contact (the cross) of the two wires is small compared with the resistance of 
 the voltmeter itself. The following method depends upon the approximate 
 correctness of this assumption. The connections are shown in figure 9-23. 
 
 Cross 
 
 
 ''E 
 
 
 Fig. 9-23.— TEST, VOLTMETER, LOCATION OF CROSSES. 
 (397)
 
 18 
 
 Signal Corps Manual No. 3.— Chapter 9. 
 
 One of the wires is grounded at some station E beyond the cross, the otlier 
 being opened there. The line battery being connected iip througli a Ivuown 
 resistance, R (a 150-ohm relay, for instance), as shown, readings are taken 
 of the voltmeter T' connected as shown first by the full lines and second as 
 shown by dotted lines. 
 
 Calling the first reading ^'^ and the second T' and R l.")0 ohms, the resistance 
 
 of the wire X to the cross is given by the formula X=~y2XR.' and if the 
 
 resistance of the wire per mile is A ohms, the number of miles to the cross is 
 
 X * 
 
 given by 2^- 
 
 The quick readings that can be made with the voltmeter make this a useful 
 method of locating swinging crosses. 
 
 The importance in all these tests, excepting ohmmeter, model 1904, of having 
 some standard known resistances available is apparent. Spare relays and 
 sounders, if not already measured up accurately, should be so measured up 
 and marked at the first opportunity or request made for such standardized 
 coils. So-called 150-ohm relays and 4-ohm sounders frequently vary 5 per cent 
 from their stated resistance and would make considerable error in the calcu- 
 lated positions of faults if used as standards. 
 
 EXPLORING COIL. 
 
 It is oftentimes necessary to locate a ground or cross in cables installed in 
 trenches or underground conduit where standard instruments are not available. 
 The u.se of an exploring coil in such cases may avoid the necessity of taking 
 up considerable lengths of cable and opening unnecessary test points. 
 
 I yeifphone fUceiver 
 
 Surfoce.qt. . earlfi 
 
 ^ 
 
 >=i 
 
 Cither duct or trench 
 
 ^tmc/- — I 
 
 \ean 
 
 pH' 
 
 c-onaucra- Wvtzar 
 
 Fig. 9-24.— TEST, EXPLORING COIL, LOCATION OF GROUND. 
 
 The exploring coil may be nuide as follows: Take a 1-inch thick pine board 
 of rectangular shape, 1 foot by 2 feet, and wind around its out(>r edge as 
 many turns of insulated wire as convenient. This wire may be ccHton-covered 
 magnet wire, N(». 18 gauge, or smaller. In jtlace of this board a rectangular 
 frame, with cliannel cross .sections, nuiy be made. To use the exi>loring coil, a 
 source of alternating (»r pulsating current is Mpi)lied lo the grounded conductor. 
 Tills source may be from a buzzer and imluclion coil connected to a battery of 
 dry cells, a 30-volt telephone storage ballery, or a 110-volt power circuit. 
 The exploring coil, with terminals connected to ;i telei)hone receiver, is now 
 carried along the route of the cable, being held as \w,\r the ground as possible 
 with the plane of the coil pnr;illel with the ciihle and the long side of the coil 
 next to the ground. The buzzer should he licnrd in the telephone receiver 
 
 (;i98)
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 19 
 
 until the f,n(>umled point in the cable has been passed, when the sound should 
 cease entirely or becon)e much weaker. Tlie exploring coil may also be used 
 for identifying cables where a inunber of them are laid in a common trench. 
 A variable current is sent through the cable to be identified and is picked up 
 by the exploring coil, one side of which should be held close to or parallel 
 witii the cable. The sh(»rt end of the coil may be used for this i)urpose. 
 
 MIIKKAY AM) VAKLEY LOOP TESTS. 
 
 The preceding sections of this chapter have de.scribed certain methods of 
 testing, entirely qualitative in character, as well as standard methods for 
 measuring conductor resistance, electro.static capacity, and insulation i-esistance. 
 In addition to these there are certain quantitative measurements necessary for 
 the location of faults in conductors, which will now be briefly described. 
 
 These tests for fault location consist essentially of cases of the application 
 of the simple methods of measurements previously described, requiring special 
 connections and a certain amount of computation from observations. It should 
 be esi)ecially noted, however, that the methods of fault location connnonly used 
 do not necessitate special ami ciynipliculed ajjparatus, but rather the appiicatidii 
 
 Fig. 9-25.— TEST, MURRAY LOOP, LOCATION OF GROUNDS. 
 
 of simple methods to special circuits and the solution of elementary formul??. 
 Two tests most generally used and of wide application are the Murray loop 
 test and the Varley loop test. The Murray loop test is the more easily made, 
 but is of less general ai)plication than the Varley. 
 
 The Murray loop circuit is shown in figure 9-2."), in which A is one of the 
 arms of a Wheatstone bridge and R the adjustable resistance. G is a gal- 
 vanometer or other current indicater. C (" the leads from bridge to conductors 
 under test, b the faulty wire, a a good wire of the same length and resistance. 
 The resi.stance of the faulty conductor, from the point of test to the fault is 
 denoted as x; a and b are connected at distant end as shown ,the leads € C 
 should be carefully measured, if their length and resistance are not negligible 
 as compareil with those of the wires a and b and the values recorded for use 
 
 (399)
 
 20 
 
 Signal Corps Mainual No. 3. — Chapter 9. 
 
 in correcting readings. Wlien the resistance R is so adjusted that the gal- 
 vanometer is not deflected the distance to tlie fault is — 
 
 _AL 
 
 where L is the combined length of a and h. The above formula assumes that 
 the leads are negligible. If such is not the case, the formula becomes — 
 
 A+R 
 
 -C. 
 
 It will usually be practicable to make the leads negligible or at least to 
 have C=C'. It is to be particularly noted that this method assumes that the 
 good and bad wires are of equal resistance. It is advisable in each case to 
 
 Fig. 9-26.— TEST, MURRAY LOOP, LOCATION OF CROSSES. 
 
 check the fault location obtained by the above circuit by reversing the wires 
 a and b and making a second location. In the above formula A and R are in 
 ohm,s, all other quantities in units of length. 
 
 For locating crossed wires the circuit of figure 9-26 should be used. It will 
 be noted that the connections are the same as for locating grounds, except that 
 the battery is connected to one of the pair of crossed wires. 
 
 The Varley loop test, while not so simple and quickly made as the Murray 
 test described above, is of more general application and can be made in situ- 
 ations where the Murray test can not. The coniurtious for this test are shown 
 in figure 9-27. The various i)arts of the circuit are given the same letter desig- 
 nations as for the Murray test of figures 9-25 and 9-26. 
 
 With the circuit of figure 9-27 adjust the variable resistance arm R of the 
 Wheatstone bridge until the galvanometer is not deflected, record the values 
 «)f A, li, and R. Now disconnect the ground from battery and connect as 
 shown by dotted line and measure the combined resistance of the leads C C 
 and the two conductors a h in series; call this value r. Combining the results 
 of the two nieiisui'ciiieiits taken above, the resistance of the conductor from 
 the point of test to the fault is — 
 
 Br- A R 
 '' A-^B 
 
 (400) 
 
 -c.
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 21 
 
 Check the iiieiisureineiits aii<l caleiilations obtained by the alxivt- profess 
 by reversiiifj the coiiiieetions of tlie bridse to the conductors at either end 
 of the leads and obtain a socoiid set of I'eadings. If the new values of bridge 
 
 Fig. 9-27.— TEST, VARLEY LOOP, LOCATION OF GROUNDS. 
 
 readings be designated as A', B' , and /?', the new value of the resistance to 
 the fault is — 
 
 If C equal the total resistance of the bad wire the distance to the fault 
 
 is j;,L, where /. is the total length of the wire. The check measurements 
 
 should always be made when using either the Varley or the Murray loop test, 
 as the time and labor required are inconsiderable and the certainty of location 
 is much increased. 
 
 For crossed wires the method of figure 9-28 should be used. The circuit, it 
 will be noted, is the same as on figure 9-27, except that one wire of the crossed 
 pair is used to replace the earth connection. 
 
 r.OCATTOX OF F.VT^T.TS IX TELEGRAPH LINE;S. 
 
 " In order to secure the best possible result in the working of telegraph line.? 
 we nmst keep down the resistance of the conductor in the circuit and increase 
 the resistance of the insulator to the greatest possible extent. In other words, 
 the resistance must be as small as jiossible in the route we wish the electric cur- 
 rent to travel and as great as possible in every other direction. The practical 
 working value of a telegraph line is the margin lietween the joint resistance of 
 the conductor and the insulator and that of the insulation alone. The tension 
 of the retracting spring of the relay armature when upon a ' working adjust- 
 ment ' is the measure of this margin or ililference. It is evident that this margin 
 may be increased in two ways, viz : (1) By increasing the insulation resistance : 
 (2) by decreasing the resistance of the conductor." — Pope's Modern Practice of 
 Electric Telegraph. 
 
 (401)
 
 90 
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 Faults causing departure from normal working conditions are due to partial 
 or complete contacts of the line wire, directly or indirectly with the ground, 
 
 
 Fig. 9-28.— TEST, VARLEY LOOP, LOCATION OF CROSSES. 
 
 usually called i>y telegraphers " escapes " and " grounds " ; crosses, caused by 
 two or more wires coming together ; and partial or complete disconnections, 
 causing abnormally high resistance, or complete interruption. 
 
 " Escapes " mean imperfect insulation, due to defective insulators, contact of 
 foliage with the wire, or defective office wiring. " Grounds " are often brought 
 about by the wire being down on the ground, to its being detached from an 
 insulator and lying against an iron pole, or defective office wiring. 
 
 Abnormally high resistance is due to defective and corroded joints in the line 
 wire or to bad connections in the office wiring, instruments, batteries, or grounds. 
 
 When stations are not very far apart, especially where they are along a rail- 
 road or good road, the location of the fault between two stations by calling up 
 each station in succession is usually sufficient. 
 
 In case of escapes it is evident that opening the key beyond the escape will 
 not entirely open the circuit at the testing office where the main-line battery 
 Is located. So by opening in succes.sion, beginning at distant stations, until we 
 come to a station where practically all current cea.ses when the key is opened, 
 will indicate that we have pas.sed the escape. 
 
 The inability to work beyoml a given station indicates a "dead gr<mn<l." 
 
 Total breaks are located by stations successively grounding, beginning :it the 
 nearest oflice to the testing office. 
 
 High resistances due to imperfect connections are located by successive 
 grounding In a .similar way, a sudden marked falling off in strength of current 
 indicating that the high resistance has just been passed. 
 
 In the case of crosses an intermediate ollice is asked to open No. 1 of the 
 crossed wires and work on No. 2. If upon ()p(Mnng No. 2 at the testing office 
 tlu' cro.ss remains, as shown by distant stations' sending coming in on N(». 1. 
 it is evident that the cross is Ix'tween the testing oflice iind the intcnnediiitc one. 
 If tiic cross li:id dis.-iitpcnred upon oi)ening No. 1 at the interniediMtc office it is 
 lieyotid tlic intermediate office 
 
 In llie first case the office next nearest the testing oflice is called and the test 
 repeated tliere. In the second case we should proceed outward from the in 
 
 (402)
 
 Miscellaneous Tests and General information.— Chapter 9. 
 
 23 
 
 terinediato otfico. A iin'tallic cross may he distinguished from a leakage or 
 "weather cross" i)y the sending through the cross in the first case coming 
 nearly as strong as it does on its own wire. 
 
 If a high resistance fault is due to hatl ofhce connection it can he detected hy 
 cutting out the odices in succession nntil an evident improvement is noted in 
 working. If due to bad joints in the line it can generally he detected hy ground- 
 ing at each station in succession ; hut these can best be located by measurements 
 of resistances from point to point. 
 
 Faulty ground plates often introduce very large resistance in the line. Con- 
 nections with the.se should he very carefully made. Only soldere<l joints should 
 he permitted, if possible, and a good-sized rod. plate, or a good length of coiled 
 wire buried in thoroughly damp ground should he used. It has often been 
 found that the resistance of the ground connection was as much as all the rest 
 of the circuit. 
 
 Two lines connected with a bad ground jilate will behave as if crossed. 
 
 T.OCATTON OF CKOSSKS OK TEAKS TX TKI.KC.KAPIT LINES BY MKANS OF THK WIKK RRIDOF,. 
 
 For crofmoi (see fig. 9-29) : Tall crossed lines No. 1 and No. 2. Request 
 rerniinal station or any station beyond cross to open No. 1 and ground No. 2 
 as in diagram. The distance to this station is L miles. Connect to bridge 
 consisting of a resistance wire stretched over a scale of 100 equal parts, 
 galvanometer and battery as shown. Call divisions of wire when balance is 
 
 obtained A and B. 
 
 T> 
 
 Tlie distance to cross X=— —L. 
 100 
 
 Fig. 9-29.— TEST, IMPROVISED BRIDGE, LOCATION OF CROSSES. 
 
 Proof: A:B::L-X:X 
 AX=BL-BX 
 
 X(A+B)=BL; X= 
 
 A+B=100 .-. X=Al 
 100 
 
 A-fB 
 
 For leaks (see fig. 9-30) : Suppose No. 1 has an escape (leak) at point indi- 
 cated. Terminal or station beyond leak connects No. 1 and No. 2, and the 
 ronnections are made as shown, for wires of same gauge and material. 
 
 T— €V 
 
 I I I H I I I I I 
 
 I 
 
 T 
 
 Fig. 9-30.— TEST, IMPROVISED BRIDGE, LOCATION OF GROUNDS. 
 
 (403)
 
 24 Signal Corps Manual No. 3. — Chapter 9. 
 
 Then if terminal station is L miles the distance to the leak X when balance 
 
 A 
 
 IS obtained is — -L miles. 
 60 
 
 Proof: A:B::X:L+(L-X) 
 2AL-AX=BX 
 
 X(A+B)=2AL; X=^^A^L. 
 
 A+B=100 .•.X=4l 
 
 50 
 
 Intermittent or swinging escapes, grounds, and crosses are exceedingly 
 troublesome to locate. They often require accurate and prompt measure- 
 ments. The Weston voltmeter and milammeter set described, being capable 
 of almost instantaneous readings, is particularly useful in this kind of meas- 
 urement. The ohmmeter measures resistances directly and almost as quickly. 
 The Wheatstone bridge gives the most accurate results, but considerable skill 
 and experience are necessary in its use. 
 
 The ohmmeter and Weston set will, it is believed, give greatest satisfaction 
 in ordinary office measurements of resistance. The voltammeter has the ad- 
 ditional advantage of giving means for measurements of voltage and current 
 as well. 
 
 The ohmmeter furnishes not only a ready means of measuring resistance, 
 hut lends itself to loop tests as well. 
 
 Where only one wire connects the stations, grounds or escapes may he ap- 
 proximately located by the ammeter or voltmeter as previously stated. 
 
 No very satisfactory simple methods exist for locating escapes when only 
 the faulty wire is available, and the tests can be made at one end only. 
 
 The simplest one is the Blavier test. This consists of making measurements 
 of resistance, first with the distant end grounded and next with the distant 
 end open. The resistance of the entire line, when in good condition, must be 
 known. (See fig. 9-31.) 
 
 Suppose measurements are made from A, B is asked to open, and measure- 
 ment is made from A through wire to fault and through fault. Call the re- 
 sistance ilA ohms. B then closes and another measurement is made. Call this 
 
 Fig. 9-31.— TEST, BLAVIER, LOCATION OF GROUNDS. 
 
 A' ohms. If the resistance of llic line is /> when in good condition, the resist- 
 ance ill (ihiiis A III ilic Caull will then be given by the formula: 
 
 X = N- ^(T^N) (M-N). 
 
 A number of jiairs nf n>jidings, using each «'iid of the battery, if possible, 
 shouhl be made, and the mean of tho.se pairs that agree most nearly should 
 be taken. 
 
 (404)
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 25 
 
 Tha ohmmeter or Weston sot may ho iisod to advantage in these measure- 
 ments and readings <tl)tained as quiclviy as possible when tlie l)atlory oiirront 
 is tlirown on, as the resistance may vary rapidly, due to the polarization at 
 the fault. It is an advantage to have tlie current through the escape 'A 
 the same when measuring .1/ and 'N . As a rough compensation in land line 
 moasuromont, use double tho battery in measuring .V as when J/ is measured. 
 
 KAUI.TKINDEH. 
 
 An instrument termed by its manuracturor " Faulttinder " is issued in special 
 instances by the Signal Corps. 
 
 Tho following is an extract from a catalogue relating to the faultfinder : 
 
 This instrument has lioon designed with a view of reducing to a minimum, cal- 
 culations coniioctod with fault location, also to simplify manipidation as much 
 as possible. It may l)o used to me.isuro conductor resistance, to measure fault 
 resistance, to locate faults by four different tests, and when used with a buzzer 
 and telephone, to locale opens. 
 
 Full directions concerning the use of this instrument are framed on the 
 inside of cover. A special battery wliich Is supported in boiiom oi c'ase is 
 necessary for its operation. 
 
 Figure 9-32 shows tbi' faidttinder with cover raised. 
 
 Fig. 9-32.— FAULTFINDER. 
 
 LINES OK INFORMATION. 
 
 This general term has been adopted to apply to the means by which military 
 messages are transmitted between two or more stations. 
 
 Under modern conditions lines of information are nearly always operated 
 electrically. On account of its certainty, secrecy, and speed, telegraphy over 
 wire lines is to-day without a rival for use on military as well as connnercial 
 lines. 
 
 As an army advances into conquered territory it will utilize as far as pos- 
 sible existing commercial lines to connect it with its base. If lines are con- 
 
 (405)
 
 26 Signal Corps Manual No. 3. — Chapter 9. 
 
 structed, they will generally at first consist of the insulated wires laid on the 
 ground which follow the advance. Such of these as are needed will subse- 
 quently be put up as light lines on lances, afterward to be converted into perma- 
 nent pole lines where necessary. Lines of a temporary character will be con- 
 structed or laid connecting the camps. When the army goes into action, an 
 important series of lines are required connecting the commanding general, the 
 corps, division, and brigade commanders, the artillery, and probably important 
 points of observation and control at other places on the line. 
 
 Classified as to their construction, lines of information are permanent, semi- 
 permanent, or field lines. 
 
 Permanent lines are those similar in construction to the standard telegraph 
 lines, and usually consist of heavy, bare copper or galvanized iron wire. No. 9 
 galvanized wire is the standard in our service. These wires are supported on 
 substantial insulators and strong poles. Such lines are generally operated with 
 the standard relays and sounders familiar in commercial offices. 
 
 Semipermanent lines consist of lighter bare wires, usually No. 14 galvanized, 
 supported on lighter poles called lances, or on light tubular steel poles. These 
 lances are fitted with hard rubber or composition insulators. Lines such as 
 these were formerly the standard military construction, and telegraph trains, 
 consisting of wire wagons, battery wagons, and lance trucks, could construct 
 from 7 to 15 miles of these lines a day, depending on conditions. These lines 
 were generally operated with ])o\ relays, but in modern use the telephone would 
 frequently be the instrument employed. 
 
 Field lines are those laid hastily for temporary use, and usually consist of 
 insulated wire paid out from reels on carts or wagons or in the smaller size 
 wire from hand reels or wire carriers. Sometimes bare wire is used, in which 
 ca.se only the " buzzer " will operate satisfactorily over them. This buzzer 
 is generally used on all field lines, although the field induction telegraph set 
 may be substituted for it under some conditions. 
 
 Classified in regard to their use, lines of infonuation may be considered as 
 either strategical or tactical lines. 
 
 Strategical lines are usually of the permanent or semipermanent character, 
 and may be part of the commercial system of the country. They are " base 
 lines " in general, as they lie behind the advancing army and maintain com- 
 nmnication with the base and thence to the seat of government. On account 
 of their importance they would frequently be duplicated, and in general over 
 different routes, to insure connnunication imder all conditions. They would 
 in some cases include important subiiuirine cables.' or even large wireless 
 stations. 
 
 Tactical lines are generally of the field line class and are rapidly laid or 
 taken up to follow the movements of the units they, connect. Tiieir name 
 indicates llieir uses. Tliey are the " c(tiiiltal liu«'s" wliicli late improvements 
 in wire, Iransjiortiit ioii, .-ind instrumenls liave made jtossible. 
 
 Ill: 1,1) IKAXSeoHTAI'IOX. 
 
 Til additifni to wagons and j)acks for ordinary transportation, the Signal 
 Toips lias found it necessary to devise some special veliicles for transporting 
 and laying wire and carrying sucii einiiimieiil as wireless sets, lances, etc. 
 
 Tlie Army is now e(|uipped witii a imiuitei- of etlicienl wire carts. This type 
 of cart is drawn by two liorses and sui»iMirts two spools which are rotated by 
 means of a sfirockel wheel iiiid cliaiii retaled by the wheels of the cart. Each 
 
 (400)
 
 Miscellaneous Tests and General Information. — Chapter 9. 27 
 
 of the reel-s of this cart will hold i^i luilcs of held wire and a lino fan ho laid 
 as rapidly as the horses are made to travel. The line is paid out from the 
 reel on the j^round and is laid to one side of the road by a man on horseback 
 in rear, by means of the wire inkv. descripetl in chapter 8. 
 
 In case a wire cart is not available, held wire lines may be laid and recov- 
 ered by means of quartermaster escort wagons and ordinary take-uj) or 
 pay-out reels. 
 
 For handling the small insulated buzzer wire, which is furnished on one- 
 iialf mile spools, the wire carriei- and iiand reel answer every purpose either 
 on foot or mounted. 
 
 The instrument wagons are either spring wagons, or the regular Army 
 escort wagon, provided with paulins or wagon covers, in which instruments, 
 light tools, repair parts, etc., may be transpoi-ted. 
 
 The lance truck is a wagon with a high seat and long reafh, sailed for the 
 transportation of lance poles. I'our mules suffice for this load uiidt-r ordinary 
 conditions. 
 
 Special pack chests ai'e provided for the Signal Corps supplies, and the 
 present field wireless pack set, which is carried on three mules, requires 
 special fittings for the aparejos. 
 
 WIKE USED IN FIELD OPERATION'S. 
 
 For the permanent military lines, No. 9 galvanized wire, weighing 820 pounds 
 to the mile, is the standard. 
 
 For semipermanent lines, such as lance lines, No. 14 galvanized wire, weigh- 
 ing about 100 pounds per mile, is used. 
 
 The two kinrls of wire used in field lines are known, respectively, as " field 
 wire " and " buzzer wire." The former corresponds with the " field cable " used 
 abroad. Our field wire, described in chapter 8 of this manual, has a tensile 
 strength of over 300 pounds and weighs 70 pounds per mile. Five miles of it 
 may be carried on the drums of the latest type wire cart. Its strength and 
 insulation are little impaired by wagons and troops passing over it. It is very 
 pliable and lies flat on irregular ground. As it is laid, mounted men follow 
 the reel cart with pikes or lances luiving hooks on the ends, either placing the 
 wire out of the way on the road, or if need be, hooking it up on trees. It is 
 difficult to break or injure this wire unintentionally. If found broken, a tem- 
 porary splice should be made. This is done by tying the ends together with 
 a hard knot, leaving about a foot of each free. The insulation is then removed 
 from the ends for several inches and the bare wires twisted together. 
 
 Buzzers or camp telephones may be quickly connected to field wire by means 
 of " Type A buzzer connectors." These connectors are furnished with sharp 
 teeth that pierce the insulation readily and, when withdrawn, damage the 
 wire very little. 
 
 In every way this type of wire seems eminently suited for field lines, the 
 only objection being its cost, which is about $75 per mile. 
 
 A small wire of this class, suitable for laying from a hand reel, is called 
 " buzzer wire," described in chapter 8 of this manual. This wire weighs 
 about 10 pounds per mile and is put up on half-mile spools. This permits 
 [laying out tlu' wire from a sinqile holder from horseback and its recovery by 
 means of a hand reel. This wire is used for short lines or for emergency lines 
 over rough ground where the heavier lield wire can not be carried. 
 
 (407)
 
 28 Signal Corps Manual No. 3.— Chapter 9. 
 
 It may be useful to remember that since buzzers will operate over long 
 stretches of bare wire laid on the ground even in wet weather, field lines of 
 any kind of wire available may be laid in emergencies. 
 
 INSTRUMENTS FOR ELECTRICAL LINES OF INFORMATION. 
 
 Base lines and other permanent telegraph lines will, of course, make use of 
 the familiar commercial apparatus. Morse instruments of various portable 
 forms, such as the box relay, main-line sounder, or pocket relay, >vill be used 
 on semipermanent lines wherever practicable. These require, however, large 
 battery equipment and well-insulated lines, and in bad weather the instruments 
 are difficult to keep in adjustment. 
 
 THE BUZZER. 
 
 On our field lines the buzzer in one of its forms is almost universally used. 
 This instrument was introduced into our service about 1890 and first showed its 
 capabilities in the Pliilippine and China campaigns. In its present form of 
 " service buzzer " it combines a complete telegraph and telephone station, includ- 
 ing the necessary batteries. Its capacity for working over circuits impossible 
 for any other telegraph instruments, such as bare-wire lines laid on the ground, 
 through wire of wire fences, or railroad rails, or, more incredible still, through 
 consideralile breaks in tlie line wlien the ends lie on the ground, makes it the 
 ideal instrument for field lines. 
 
 To open a station it is only necessary to fasten the buzzer connector with 
 flexible cord from one binding post to the field wire, and from the other binding 
 post a flexible wire leads to a small ground rod or metal peg driven into the 
 ground. 
 
 By working the key an interrupter is operated giving a higli singing note, 
 which is i)roken up into the dots and dashes of the Morse alphabet. These 
 correspond to vil)ratory electrical impulses which go out on the line and are 
 heard in the teloplione receiver at the distant station. The efficiency of the 
 buzzer under the difficult conditions stated is due to the marvelous sensitiveness 
 of the telephone receiver to these rapidly pulsiiting currents. In practically the 
 same circuit as the interrupter is a telephone transmitter, and when the button 
 switch on this is depressed the instrument becomes at once converted into a 
 very efficient telephone set. 
 
 THE CAMI- TELEI'HONE. 
 
 This instrument described in chapter 3 lias all the component parts of the 
 most complete telephone. The box is very strong and weatherproof and has a 
 strap for convenience in carrying. The connections are very simple and easily 
 rej)aired when deranged. If can hv connected to field lines and the ground in 
 the same way as the b\r/>zer. Its common use, however, is for cami) lines where, 
 with its generator and call bell, it is .specially suited for connection with the 
 camp switchboard described in chapter 8. 
 
 KIEI.l) INDIICTION TELEfJK.MMI. 
 
 On semipermanent lines, especially where business over them is heavy, the 
 continual use of (lie bnz/er is very fatigin'ng to Morse operators. The induction 
 telegraph sv\ desc riixMl in ciiiipler 'J li.-is l)eeii devised especially for this class 
 of lines, operating the key of this instrument .sends out impulses of high volt- 
 age over the line and relays. These relays are very sensitive and operate with 
 
 (408)
 
 Miscellaneous Tests and General Information. — Chapter 9. 29 
 
 a remarkably small ruriiMit. As a result of the voltaRO increase and relay 
 sensibility, three dry cells of battery will work the sets over Inindreds of miles 
 of iron wire, over ordinary circuits where the insulation Icnkaw permits the 
 escape of On per cent of the current. Doing away, as it does, with carryint; large 
 amounts of battery, it is believed to be a useful intermediate instrument be- 
 tween the buzzer and the regular telegraph installation. 
 
 SKLECTION OF INSTRUMENTS. 
 
 The buzzer, the telephone, and telegraph each has fairly well defined roles in 
 operating electrical lines of information. The buzzer is the pioneer which clears 
 the way, follows up the fighting line, and can operate over any kind of a line. 
 Its function as a telegraph instrument is the paramount one on account of its 
 reliability, although, as stated, it is a good telephone when the wire is in proper 
 condition. The camp teleplione is most useful in camp administration lines or 
 over semipermanent lines in general where telephone service seems desirable. 
 
 The telegraph is standard where lines are established and where the volume 
 and importance of business become great. To the trained operator there is 
 nothing to equal the clearness and certainty with which a message on a Morse 
 sounder is delivered, and such operation is the ultimate excellence toward which 
 military lines aim. 
 
 The decision as to when the telephone or telegraph should be installed or used 
 is governed by the following considerations : 
 
 The telephone does not require trained operators. 
 
 The telephone may be used for direct, and consequently confident inl. com- 
 munication between officers. 
 
 Time is saved, compared with telegraphy, especially when the users are accus- 
 tomed to the telephone. 
 
 The telegraph is superior to the telephone in the following ways : 
 
 Accuracy. — A written message, spelled out by telegraphy, written and de- 
 livered, has an obvious advantage over one delivered by word of mouth. 
 
 licUnhiUfy. — In the field, especially when the wind is blowing in the ears and 
 viirious other noises tend to confuse, it is very hard to distinguish in the tel- 
 ephone words which sound alike. This is especially confusing to an enlisted 
 man unused to expressions conunon in military messages. The sharp signals on 
 the buzzer or sounder are nmch more reliable. 
 
 Speed. — It is found in the case of written messages transmitted by buzzer and 
 telephone that, owing to frequent repetitions required by telephone, the buzzer 
 will generally exceed it in speed. 
 
 From the foregoing considerations it is evident that officers should, when 
 time permits, always write out their messages in proper form. The use of the 
 telephone- should be restricted to conminnication between officers. The direction 
 to an operator verbally to send messages liy telegraph is inadvisable. Sending 
 messages by dictation through the telephone invites almost certain errors. 
 
 Miscellaneous Tables and Information. 
 
 t'nits of resistance. 
 
 Th<> unit of n>sistan«t' now universally used is the international ohm. Tlie 
 following multiples of this unit are sometimes employed: 
 
 Ohms. 
 Megohm =1,000,000. 
 Microhm =0.000,001. 
 
 (409)
 
 30 
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 The following table gives the value of the principal practical units of resist- 
 ance which existed previous to the establishment of the international iniits; 
 
 Unit. 
 
 Interna- 
 tional ohm. 
 
 B.A.ohm. 
 
 Legal ohm, 
 
 1884. 
 
 Siemens' 
 ohm. 
 
 
 1.000 
 .9866 
 .9972 
 .9407 
 
 1.0136 
 1.000 
 1.0107 
 .9535 
 
 1.0028 
 
 .9894 
 1.000 
 .9434 
 
 1.06.30 
 
 B. A.ohm 
 
 1.0488 
 
 
 1.0600 
 
 
 1.000 
 
 
 
 Then 
 
 Thus, to reduce British Association ohms to international ohms we divide 
 by 1.0136, or multiply by 0.9866; and to reduce legal ohms to international 
 ohms we divide by 1.0028, or multiply by 0.0972, etc. 
 
 SPECIFIC RESISTANCE. 
 
 Let Z=length of the conductor. 
 
 J.^cro.«:s section of the conductdr. 
 i?=resistance of the conductor. 
 /)=specific resistance of the conductor. 
 
 I 
 
 'a' 
 
 or p=R^. 
 
 If I is measured in centimeters and -1 in square centimeters, p is the resist- 
 ance of a centimeter cube of the conductor. If / is measured in inches and A 
 is .square inches, p is the resistance of an inch cube of the conductor. 
 
 In telegraph and telephone practice, specific resistance is .sometimes ex- 
 pressed as the ivcifiht per mile-ohm, which is the weight in pounds of a con- 
 ductor 1 mile long having a resistance of 1 ohm. 
 
 Another common way of expressing specific resistance is in terms of ohms 
 per mil- foot, i. e.. the resistance of a round wire 1 foot long nnd 0.001 inch 
 in diameter; / is then measure<l in feet and A in circular mils. 
 Microhms i)er inch cu]ie=0.r{!t;{7X microhms per ('(MUimeter cube. 
 Pounds iier mil(>-ohm = r)7.07X microhms i)er centimeter cul)eX.si)ecitic gravity. 
 Ohms per mi]-foot=6.01.1X microhms i»er centimeter cul)o. 
 Specific conductivity is the reciprocal of specific resistance. If r=specific 
 condutivity, 
 
 / 
 
 -cA' 
 
 J_ 
 
 '-RA' 
 
 R= 
 
 1 
 
 I'.y relative or pcrcontiige conductivity of :i siiiniil(> is inc.-int 100 times the 
 ratio of tiic condnctivity of the sample ;it standard tenqu'rat ur*' to the con- 
 ductivity of a conductor of the same dimensions made of the standard ma- 
 terial and at standard tenq)erat\u-e. If p„ is the specific resistance of the 
 sample at standard temperature and /)., is the sijccific resistance of the 
 standard at stand;ird lenqieriitiire, then 
 
 Percentage! conducl ivitv=100'''. 
 
 Po 
 
 (410)
 
 Miscellaneous Tests and General Information. — Chapter 9. 31 
 
 In coniparinj,' different materials, the specific resistance sliould always in; 
 determined at the standard temperature, whicli is usually talien as 0° cen- 
 tigrade. If it is inconvenient to measure the resistance of the sample at 
 the standard temperature, this may he readily calculated if tlie temperature 
 coelHcient n of the sample is linown, i. e., 
 
 Avliere pt is the specihc resistance at teujperature /. 
 
 ^latthiessen's standard of conductivity, winch is the commercial standard, 
 is a copper wire haviiii: the followinir properties at the standard temperature 
 of 0° centigrade : 
 
 SpeciHc gravity 8.89. 
 
 Length ^ 1 meter. 
 
 Weight 1 gram. 
 
 Resistance 0. 1-11720 ohms. 
 
 Specific resistance l.oiM microhms per cubic centimeter. 
 
 Relative conductivity KTd per cent. 
 
 i^pccific rcsistuncv, ninlirc rrsit^finirr. (iiid rrldlirc conductivity of coiirJurtors. 
 [Roferred to Mattliicsseu's standard.] 
 
 Metals. 
 
 Silver, anne^nled 
 
 Copper, auiicalod 
 
 Copper ( Matthiessen's standard) 
 
 Gold (i)9.9 per cent pure) 
 
 Aluminum (99 per cent pure). . . 
 
 Zinc 
 
 Platinum, aruiealed 
 
 Iron 
 
 Nickel 
 
 Tin 
 
 licad 
 
 Antimony 
 
 Mercury 
 
 Bismuth 
 
 Carbon (graphitic) 
 
 Carbon (arc light) 
 
 Selenium 
 
 Resistance in microhms 
 at 0° C. 
 
 Centimeter 
 cube. 
 
 1.47 
 1.5.5 
 1.594 
 2.20 
 2. .56 
 5. 75 
 8.98 
 9.07 
 12. .3 
 13.1 
 20.4 
 .^5.2 
 94.3 
 130. 
 2,400-42,000 
 about 4,000 
 6X10>» 
 
 Inch cube. 
 
 0.579 
 .610 
 . 6276 
 .865 
 1.01 
 2.26 
 3.53 
 3.57 
 4.&5 
 5. 16 
 8.04 
 13.9 
 37.1 
 51.2 
 950-16, 700 
 about 1,.590 
 2.38X1010 
 
 Relative , Relative 
 
 resist- 
 ance. 
 
 Per cent. 
 92.5 
 97.5 
 
 100 
 
 138 
 
 161 
 
 362 
 
 .565 
 
 570 
 
 778 
 
 S2S 
 1.280 
 2.210 
 5. 930 
 8,220 
 
 conduc- 
 tivity. 
 
 Per cnt. 
 108.2 
 102.6 
 100. 
 72.5 
 62.1 
 27.6 
 17.7 
 17.6 
 12.9 
 12.1 
 7.82 
 4. .53 
 1.69 
 1.22 
 
 Resistances of liquid conductors. 
 
 Liquids at 18° C. 
 
 Pure water 
 
 Sea water 
 
 Sulphuric acid: 
 
 5 percent 
 
 30 per cent 
 
 SO per cent 
 
 Nitric acid, 30 percent .. . 
 Zinc sulphate, 24 per cent 
 
 Ohms per 
 
 centimeter 
 
 cube. 
 
 2,650. 
 30. 
 
 4.86 
 1.37 
 9.18 
 1.29 
 21.4 
 
 Ohms per 
 inch cube. 
 
 1,050. 
 11.8 
 
 1.93 
 .544 
 
 3.64 
 .512 
 
 8.54 
 
 46581°— 17- 
 
 (411)
 
 32 
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 TEMPERATURE COEFFICIENT. 
 
 The i-esistauce of ii conductor varies with the temperature of the couductor. 
 
 Let i?o=resistance at 0°. 
 R = resistance at i°. 
 Then 7? =Ro (1+fl O- 
 
 a is called the temperature coefficient of the conductor; 100 a is the percentage 
 change in resistance per degree change in temperature. 
 
 The following values of temperature coefficients have been found for l(Mnpera- 
 tures measured in degrees Centigrade and in degrees Fahrenheit. It is to be 
 noted that the coefficients vary considerably with the purity of the conductor. 
 
 Pure metals. 
 
 Silver, annealed 
 
 Copper, armealed 
 
 Gold (99.9 per cent) 
 
 Aluminum (99 per cent) 
 
 Zinc 
 
 Platinum, annealed 
 
 Iron 
 
 Nickel 
 
 Tin 
 
 Lead 
 
 Antimony 
 
 Mercury 
 
 Bismuth 
 
 Centi- 
 
 Fahren- 
 
 grade.i 
 
 heit. n 
 
 0.00400 
 
 0.00222 
 
 .00428 
 
 .00242 
 
 . 00377 
 
 .00210 
 
 . (XM23 
 
 .00235 
 
 . 00406 
 
 .00226 
 
 .00247 
 
 .00137 
 
 .00625 
 
 .00347 
 
 .0062 
 
 .00345 
 
 .00440 
 
 .00245 
 
 .00411 
 
 .00228 
 
 . 00389 
 
 .00216 
 
 .00072 
 
 .00044 
 
 .00354 
 
 .00197 
 
 Matthiessen's formula for soft copper wire R=Ro (l+.00387*+.00000597f=). 
 
 The wire used by Matthiessen was as pure as could be obtained at the time 
 (1860), but in reality contained considerable impurities; the above formula, 
 therefore, is not generally applicable. Later experiments have shown that for 
 all practical work the above equation for copper wire may be written R=Ro 
 (1+.0042O for t in ° C. 
 
 WIRE GAUGES. 
 
 The sizes of wires are ordinarily expressed by an arbitrary series of numbers. 
 Unfortunately there are several independent numbering methods, so that it is 
 always necessary to specify the method or wire gauge used. The following table 
 gives the numbers and diameters in decimal parts of an inch for the various 
 wire gauges used iu this country and England: 
 
 (412)
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 33 
 
 Number 
 of wire 
 gauge. 
 
 Roebling 
 or Wash- 
 burn & 
 Moens. 
 
 Bro\TO & 
 Sharpe. 
 
 BirminR- 
 ham or 
 Stubs 
 
 English le- 
 gal stand- 
 ard. 
 
 Old Eng- 
 lish or 
 London. 
 
 
 Inch. 
 
 Inch. 
 
 Inch. 
 
 Inch. 
 
 Inch. 
 
 6-0 
 5-0 
 4-0 
 
 0. 460 
 .430 
 .393 
 
 
 
 0.464 
 .4.32 
 .400 
 
 
 
 
 
 ""6.'4606"' 
 
 6.' 454" 
 
 '"o.ihAo" 
 
 3-0 
 
 .362 
 
 .4096 
 
 .425 
 
 .372 
 
 .42.50 
 
 2-0 
 
 .331 
 
 .3648 
 
 .380 
 
 .348 
 
 .3800 
 
 
 
 .307 
 
 .3249 
 
 .340 
 
 .324 
 
 ..3400 
 
 1 
 
 .283 
 
 . 2893 
 
 .300 
 
 .300 
 
 .3000 
 
 2 
 
 .263 
 
 . 2576 
 
 .284 
 
 .276 
 
 .2840 
 
 3 
 
 .244 
 
 .2294 
 
 .259 
 
 .252 
 
 .2.590 
 
 i 
 
 .225 
 
 . 2043 
 
 .2.38 
 
 .232 
 
 .2380 
 
 5 
 
 .207 
 
 .1819 
 
 .220 
 
 .212 
 
 .2200 
 
 6 
 
 .192 
 
 .1620 
 
 .203 
 
 .192 
 
 . 2030 
 
 7 
 
 .177 
 
 .1443 
 
 .180 
 
 .176 
 
 .1800 
 
 S 
 
 . 162 
 
 .128,5 
 
 .165 
 
 .160 
 
 . 16.50 
 
 9 
 
 .118 
 
 .1144 
 
 .148 
 
 .144 
 
 .1480 
 
 10 
 
 . 1M5 
 
 .1019 
 
 .134 
 
 .128 
 
 .1340 
 
 11 
 
 .120 
 
 .00074 
 
 .120 
 
 .116 
 
 .1200 
 
 12 
 
 .105 
 
 . 08081 
 
 .109 
 
 .104 
 
 .1090 
 
 13 
 
 .092 
 
 .07196 
 
 .095 
 
 .092 
 
 .09.50 
 
 14 
 
 .080 
 
 . 06408 
 
 .083 
 
 .080 
 
 .08.30 
 
 15 
 
 .072 
 
 . 05706 
 
 .072 
 
 .072 
 
 .0720 
 
 16 
 
 .063 
 
 .05082 
 
 .065 
 
 .064 
 
 .06.50 
 
 17 
 
 .054 
 
 .04525 
 
 .058 
 
 .056 
 
 .0.580 
 
 18 
 
 .047 
 
 .04a30 
 
 .049 
 
 .048 
 
 .0490 
 
 19 
 
 .041 
 
 . 03589 
 
 .042 
 
 .040 
 
 .0400 
 
 20 
 
 . 035 
 
 . 03196 
 
 .035 
 
 .036 
 
 . 03.50 
 
 21 
 
 .032 
 
 .02846 
 
 .032 
 
 .032 
 
 .a315 
 
 22 
 
 .028 
 
 . 02.534 
 
 .028 
 
 .028 
 
 . 0295 
 
 23 
 
 .025 
 
 . 02257 
 
 .025 
 
 .024 
 
 .0270 
 
 24 
 
 .023 
 
 . 02010 
 
 .022 
 
 .022 
 
 . 02.50 
 
 25 
 
 .020 
 
 .01790 
 
 .020 
 
 .020 
 
 .0230 
 
 26 
 
 .018 
 
 .01594 
 
 .018 
 
 .018 
 
 . 0205 
 
 27 
 
 .017 
 
 .01419 
 
 .016 
 
 .0164 
 
 . 01875 
 
 2S 
 
 .016 
 
 .01264 
 
 .014 
 
 .0148 
 
 . 016.50 
 
 29 
 
 .015 
 
 .01125 
 
 .013 
 
 .0136 
 
 .015.50 
 
 30 
 
 .014 
 
 . 01002 
 
 .012 
 
 .0124 
 
 . 01375 
 
 31 
 
 . 0135 
 
 . 00893 
 
 .010 
 
 .0116 
 
 . 01225 
 
 32 
 
 .0130 
 
 . 00795 
 
 .009 
 
 .0108 
 
 .01125 
 
 33 
 
 .0110 
 
 .00708 
 
 .008 
 
 .0100 
 
 .01025 
 
 34 
 
 .0100 
 
 .00630 
 
 .007 
 
 .0092 
 
 .0095 
 
 35 
 
 .0095 
 
 . 00561 
 
 .005 
 
 .0084 
 
 .0090 
 
 36 
 
 .0090 
 
 .00500 
 
 .om 
 
 .0076 
 
 . 0075 
 
 37 
 38 
 39 
 40 
 
 .0085 
 .0080 
 .0075 
 .0070 
 
 . 00445 
 .00397 
 . 00353 
 .00314 
 
 
 .0068 
 .0060 
 .0052 
 .0048 
 
 .0065 
 .0057 
 .0050 
 .0045 
 
 
 
 
 
 Roehling gauge. — Used in this country for iron and steel wire. 
 
 Broum d Sharpe gauge. — The American standard for copper wires for elec- 
 trical purposes. 
 
 Birmingham gauge. — Used lariiel.v in England and also in this country for 
 iron and steel wires for electrical purposes. 
 
 LAW OF THE BROWX & SHARPE GAUGE. 
 
 The diameters of wires on the B. & S. gauge are obtained from the geometric 
 series in which No. 0000=0.4600 inch and No. 36=0.005 inch, the nearest fourth 
 significant figure being retained in the areas and diameters so deduced. 
 
 Let n = gauge number (0000 =—3; 000 = — 2; 00=-l). 
 d = diameter of wire in inches. 
 
 Then d-- 
 
 0.3249 
 '1.123"* 
 
 (413)
 
 34 
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 Sheathing core. — The number (N) of sheathing wires having a tliauieter (d) 
 which will cover a core having a diameter (/>) is 
 
 iV=7r 
 
 D+d 
 
 Tensile strength of copper irire. 
 
 COMMERCIAL STANDARDS. 
 
 Kumbers, 
 B. &S. 
 gauge. 
 
 Breaking weight. 
 
 Numbers, 
 B. &S. 
 gauge. 
 
 Breaking weight. 
 
 Hard- 
 drawn. 
 
 Annealed. 
 
 Hard- 
 drawn. 
 
 Annealed. 
 
 (MKX) 
 000 
 00 
 
 1 
 2 
 3 
 4 
 5 
 6 
 
 8 
 
 Poundn. 
 8.310 
 6. 580 
 5.226 
 4.. 558 
 3,746 
 3,127 
 2,480 
 1,967 
 1.559 
 1.2.37 
 980 
 778 
 
 Pounds. 
 
 5, 6.50 
 
 4.480 
 
 3. ,553 
 
 2, 818 
 
 2,234 
 
 1,772 
 
 1,405 
 
 1,114 
 
 8.83 
 
 700 
 
 555 
 
 440 
 
 9 
 10 
 11 
 12 
 13 
 14 
 15 
 16 
 17 
 18 
 19 
 20 
 
 Pounds. 
 
 617 
 
 4S9 
 
 388 
 
 307 
 
 244 
 
 193 
 
 153 
 
 133 
 
 97 
 
 77 
 
 61 
 
 48 
 
 Pounds. 
 
 349 
 
 277 
 
 219 
 
 174 
 
 138 
 
 109 
 
 87 
 
 69 
 
 55 
 
 43 
 
 34 
 
 27 
 
 The stnnigth of soft copper wire varie.s from ;«.0()0 to ;}6,()00 pounds per 
 square inch, and of hard coi)i)er wire from 45,0tl() to 6S,(KK) pounds per square 
 inch, according to the degree of hardness. 
 
 The above table is calculated for 34,00t) pounds for soft wire and (JO.OOO 
 pounds for hard wire, except for some of the larger sizes, where the breaking 
 weight per scjuare inch is taken at 50,000 pounds for 0000, 000, and 00; 55,000 
 for ; and 57,000 pounds for 1. 
 
 Hard-draini copper telephone and teleyrapli ivire. 
 
 COMMERCIAL VALUES. 
 
 Size 
 B. &S. 
 
 guage. 
 
 Kesistaiipe 
 per mile. 
 
 Breaking 
 
 utrenjjth. 
 
 Weight 
 per mile. 
 
 Furnished 
 
 in coils as 
 
 follows. 
 
 Approximate size 
 Vj. R. H. iron wire 
 equal to copper. 
 
 
 Ohw.i. 
 
 Poundn. 
 
 Pounds. 
 
 Miles. 
 
 
 '.) 
 
 4.30 
 
 625 
 
 209 
 
 1 
 
 2 
 
 10 
 
 .5.40 
 
 525 
 
 166 
 
 1.2 
 
 3 
 
 
 11 
 
 6.00 
 
 420 
 
 131 
 
 ..52 
 
 4 
 
 
 12 
 
 8.70 
 
 330 
 
 104 
 
 .65 
 
 6 
 
 Iron - wire 
 
 13 
 
 10.90 
 
 270 
 
 83 
 
 1.20 
 
 61 
 
 gua,i;e. 
 
 14 
 
 13. 70 
 
 213 
 
 66 
 
 1.50 
 
 8 
 
 
 15 
 
 17.40 
 
 170 
 
 52 
 
 2.(X) 
 
 9 
 
 
 16 
 
 22.10 
 
 130 
 
 41 
 
 1.20 
 
 10 
 
 ill liMiidling this wire t]i<' greatest r;\rv siiould lie oliserved to avoid kinks, 
 i)ends, scratclies, or cuts. .loiiits should he made only with copiier s])]icing 
 sleeves and connect oi-s. 
 
 On account of its conductivity being about live times that of Ex. B. B. iron 
 wire, and Its l)reaking strength over three times its weight per mile, copper 
 may be used of which the section is smaller and the weight less than an 
 ('((uivalent iron wire, allowing a greater minilier of wires to lie strung on the 
 poles. 
 
 (414)
 
 Miscellaneous Tests and General Information. — Chapter 9. 
 
 35 
 
 Besides this advantage, tlie reduction of section materially decreases tlie 
 electrostatic capacity, while its nonmagnetic character lessens the self-induction 
 of the line, Ixttli of which features tend to increase the possible si)eed of sig- 
 naling in tek'graphing, and to give greater clearness of enunciation over 
 telephone lines, especially those of great lengtli. 
 
 Standard copper strands. 
 
 rOMMKUCIAT. STANUAKUS. 
 
 
 Wires. 
 
 
 1 
 
 C. M. 
 
 
 Outside 
 
 Weight per 
 1,000 feet. 
 
 
 
 diameter. 
 
 
 Xumber. 
 
 Size. 
 
 
 
 
 
 Inch. 
 
 Inches. 
 
 Pounds. 
 
 2,000,000 
 
 127 
 
 0. 1255 
 
 1.632 
 
 6,100 
 
 1,950,000 
 
 127 
 
 . 1239 
 
 1.611 
 
 5,948 
 
 1,900,000 
 
 127 
 
 .1223 
 
 1.590 
 
 5, 795 
 
 1,8.')0,(K)0 
 
 127 
 
 . 1207 
 
 1. .569 
 
 5,643 
 
 1,SOO,IM)() 
 
 127 
 
 .1191 
 
 1.548 
 
 5,490 
 
 1,7.')0,IXH) 
 
 127 
 
 .1174 
 
 1. 526 
 
 5,338 
 
 1,7U0,0(_K) 
 
 91 
 
 .1367 
 
 1.504 
 
 5, 185 
 
 l,f):>l),lKK) 
 
 91 
 
 . 1347 
 
 1.482 
 
 .5,033 
 
 1,000,000 
 
 91 
 
 . 1326 
 
 1.459 
 
 4,8M) 
 
 1,0.30,000 
 
 91 
 
 . 1305 
 
 1.436 
 
 4,728 
 
 1,500,000 
 
 91 
 
 .1284 
 
 1.412 
 
 4,575 
 
 1,4.")0,000 
 
 91 
 
 . 1262 
 
 1.388 
 
 4,423 
 
 1,400,000 
 
 91 
 
 .1240 
 
 1.364 
 
 4,270 
 
 1,350,000 
 
 91 
 
 . 1218 
 
 1.340 
 
 4,118 
 
 1,300,0(X) 
 
 91 
 
 . 1195 
 
 1.315 
 
 3,965 
 
 1,2.')(),0(X) 
 
 91 
 
 .1172 
 
 1.289 
 
 3, 813 
 
 1,200,(X)0 
 
 61 
 
 .1403 
 
 1.263 
 
 3,660 
 
 1,1.50,000 
 
 61 
 
 .1373 
 
 1. 236 
 
 3,508 
 
 1,100,000 
 
 61 
 
 . 1343 
 
 1.209 
 
 3,3.55 
 
 1,0.50,00(J 
 
 61 
 
 . 1312 
 
 1.181 
 
 3,203 
 
 i,m)o,i)oo 
 
 61 
 
 .1280 
 
 1.152 
 
 3,050 
 
 9.50, iKK) 
 
 61 
 
 .1247 
 
 1.122 
 
 2,898 
 
 91H), 000 
 
 61 
 
 . 1214 
 
 1.093 
 
 2,745 
 
 S.50,0(_)0 
 
 61 
 
 .1180 
 
 1.062 
 
 2,593 
 
 800,000 
 
 61 
 
 .1145 
 
 1.031 
 
 2,440 
 
 7.50, (XK) 
 
 61 
 
 . 1108 
 
 .997 
 
 2,288 
 
 700, ax) 
 
 61 
 
 .1071 
 
 .964 
 
 2, 135 
 
 6.50, (KK) 
 
 61 
 
 .1032 
 
 .929 
 
 1,983 
 
 600,000 
 
 61 
 
 .0991 
 
 .892 
 
 1,830 
 
 5.50, 000 
 
 61 
 
 .0949 
 
 .854 
 
 1,678 
 
 ■500, (KM) 
 
 61 
 
 .0905 
 
 .815 
 
 1,525 
 
 4.50, (HR) 
 
 37 
 
 .1103 
 
 .772 
 
 1,373 
 
 4CW,000 
 
 37 
 
 .1039 
 
 .727 
 
 1,220 
 
 3.50,000 
 
 37 
 
 .0972 
 
 .680 
 
 1,068 
 
 300, (HK) 
 
 37 
 
 .0900 
 
 .630 
 
 915 
 
 2.50, 000 
 
 37 
 
 .0821 
 
 .575 
 
 763 
 
 
 
 Wires. 
 
 
 
 Size, 
 
 
 
 Outside 
 
 Weight 
 
 
 
 B. & .S. 
 
 Num- 
 ber. 
 
 Size. 
 
 diameter. 
 
 per 
 1,000 feet. 
 
 
 
 Inch. 
 
 Inch. 
 
 Pounds. 
 
 0000 
 
 19 
 
 0. 1055 
 
 0. 528 
 
 645 
 
 000 
 
 19 
 
 .0941 
 
 .471 
 
 513 
 
 00 
 
 19 
 
 .0837 
 
 .419 
 
 406 
 
 
 
 19 
 
 .0746 
 
 .373 
 
 322 
 
 1 
 
 19 
 
 .0663 
 
 .332 
 
 2.55 
 
 
 
 
 .0975 
 
 .293 
 
 203 
 
 3 
 
 
 
 .0866 
 
 .260 
 
 160 
 
 4 
 
 
 
 .0771 
 
 .231 
 
 127 
 
 .') 
 
 
 
 .0688 
 
 .206 
 
 101 
 
 6 
 
 
 
 .0612 
 
 .184 
 
 80 
 
 8 
 
 
 
 .0484 
 
 .145 
 
 50 
 
 10 
 
 
 
 .0386 
 
 .116 
 
 32 
 
 12 
 
 
 
 .0306 
 
 .092 
 
 20 
 
 14 
 
 
 
 . 0242 
 
 .073 
 
 12 
 
 16 
 
 
 
 .0193 
 
 .058 
 
 8 
 
 18 
 
 
 
 .0151 
 
 .045 
 
 5 
 
 (415)
 
 36 Signal Corps Manual No. 3. — Chapter 9. 
 
 Carrying capacity of insulated copper tvires for interior wiring. 
 
 NATIONAL ELKCTRICAL CODE. 
 
 B. & S. 
 Co 
 
 
 Rubber- 
 
 Weather- 
 
 
 Rubber- 
 
 Weather- 
 
 Area. 
 
 covered 
 
 proof 
 
 Area. 
 
 covereil 
 
 proof 
 
 
 
 wires. 
 
 wires. 
 
 
 wires. 
 
 wires. 
 
 
 Cir. viih. 
 
 Amperes. 
 
 Amperes. 
 
 Cir. mils. 
 
 A mperes. 
 
 Amperes. 
 
 IS 
 
 1,624 
 
 3 
 
 5 
 
 200,000 
 
 200 
 
 300 
 
 16 
 
 2,583 
 
 6 
 
 S 
 
 300,000 
 
 270 
 
 400 
 
 14 
 
 4,107 
 
 12 
 
 16 
 
 4(K), 0(K) 
 
 330 
 
 500 
 
 12 
 
 6,530 
 
 17 
 
 Zi 
 
 .500, WKl 
 
 390 
 
 590 
 
 10 
 
 10, 380 
 
 24 
 
 32 
 
 60(),IK)0 
 
 450 
 
 680 
 
 s 
 
 16,510 
 
 33 
 
 46 
 
 700, IMK) 
 
 .500 
 
 760 
 
 6 
 
 26, 250 
 
 46 
 
 65 
 
 8U0, 000 
 
 550 
 
 840 
 
 
 
 33, 1(X) 
 
 54 
 
 77 
 
 900, (KK) 
 
 600 
 
 920 
 
 4 
 
 '11,740 
 
 65 
 
 92 
 
 1,(HK),IKK) 
 
 650 
 
 1,000 
 
 3 
 
 .52,6.30 
 
 76 
 
 110 
 
 1,1IK),(K)0 
 
 690 
 
 1,080 
 
 2 
 
 66, 370 
 
 90 
 
 131 
 
 1,2(K),(H)0 
 
 730 
 
 1,150 
 
 1 
 
 .S3, 690 
 
 107 
 
 156 
 
 1,3(K),(X)0 
 
 770 
 
 1,220 
 
 
 
 105, .500 
 
 127 
 
 185 
 
 1,400,000 
 
 810 
 
 1,290 
 
 00 
 
 133, 1(X) 
 
 150 
 
 220 
 
 1,,')00,0(X) 
 
 850 
 
 1,360 
 
 0(W 
 
 167, 800 
 
 177 
 
 262 
 
 1,600, (XX) 
 
 890 
 
 1,430 
 
 0000 
 
 211,600 
 
 210 
 
 312 
 
 1,700,000 
 1,800.000 
 
 930 
 970 
 
 1,490 
 1 550 
 
 
 
 
 
 1,9(X),(X)0 
 
 1,010 
 
 1,610 
 
 
 
 
 2,000,000 
 
 1,050 
 
 1,670 
 
 
 ' 
 
 1 
 
 Carrying capacity of stranded copper conductors for interior tviring. 
 NATIONAL ELECTRICAL CODE. 
 
 B. &S. 
 gauge. 
 
 Area actu- 
 al C. M. 
 
 Number of 
 strands. 
 
 Size of 
 strand, B. 
 & S. gauge. 
 
 Amperes. 
 
 19 
 18 
 17 
 16 
 15 
 14 
 12 
 
 1,288 
 
 1,624 
 
 2,048 
 
 2,583 
 
 3,257 
 
 4,107 
 
 6,530 
 
 9,016 
 
 11, .368 
 
 14,336 
 
 18,081 
 
 22,799 
 
 30, 856 
 
 38, 912 
 
 49,077 
 
 60,088 
 
 75, 776 
 
 99,064 
 
 124,928 
 
 1,57, .5(5.3 
 
 198, 677 
 
 2.50, 527 
 
 29(5, 387 
 
 373, 737 
 
 413,639 
 
 
 
 
 
 
 
 
 
 
 
 
 6 
 
 
 
 
 
 12 
 
 17 
 
 21 
 
 25 
 
 30 
 
 35 
 
 40 
 
 50 
 
 60 
 
 70 
 
 85 
 
 1(X) 
 
 120 
 
 145 
 
 170 
 
 200 
 
 235 
 
 270 
 
 320 
 
 340 
 
 
 
 7 
 7 
 7 
 7 
 7 
 
 19 
 19 
 19 
 37 
 37 
 61 
 61 
 61 
 61 
 61 
 91 
 91 
 127 
 
 19 
 18 
 17 
 16 
 15 
 18 
 17 
 16 
 18 
 17 
 18 
 17 
 16 
 15 
 14 
 15 
 14 
 . 15 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 For aluminuin wire the carryiiifi capacily of any jiiven size is to bo taken as 
 84 per cent of the value given in tiie above table. 
 
 (416)
 
 Miscellaneous Tests and General Information, — Chapter 9. 
 
 us SIGNAL CORPS 
 
 TABLES OF TEMPERATURE COEFFICIENTS 
 
 FOR REDUCING CONDUCTOR AND INSULATION RESISTANCE! 
 TO STANDARD TEMPERATURE 
 
 Fig. 9-33.— TEMPERATURE COEFFICIENTS. 
 (417)
 
 38 Signal Corps Manual No. 3. — Chapter 9. 
 
 USEFUL CONSTANTS ANU FORMULA. 
 
 I From Electrical Tables and FormuliP. Clark and Sahinc. ] 
 
 coppEi:. 
 
 The specific gravity of copper wire, according to tlie best autliorities, is 
 about 8.899. 
 
 One cubic foot weighs about 550 pounds. 
 
 One cubic incli weighs 0.32 pound. 
 
 The ordinai-y breaking weigiit of copper wire is about 17 tons per square 
 inch, varying greatly, however, according to the size and degree of hardness. 
 
 The weight per nautical mile of any copper wire is about .. pounds, d being the 
 diameter in mils. 
 
 The weight per nautical mile of a copper strand is about — -— pounds. 
 
 /0.4 
 
 (P 
 The weight per statute mile of any copper wire is — pounds. A mile of 64 mils 
 
 diameter, wire weighs in practice from 63 to 66 pounds. 
 
 Tlie diameter of any copper wire weighing lo pounds per nautical mile is 7.4 
 \/io mils. 
 
 Tlie diameter of any copper wire weighing iv pounds per statute mile is 7.94 
 ^/w mils. 
 
 The diameter of a copper strand weighing w pounds per nautical mile is 
 about 8.4 y/w mils. 
 
 The approximate resistance of a nautical mile of pure copper weighing 1 
 pound is, at 32° F., 1,091.22 ohms; at 60° F.. 1,155.48 ohms; at 75° F., 1,192.45 
 ohms. 
 
 The resistance per nautical mile of any pure copper wire or strand weighing tt' 
 
 poundsi8^^^'^at75°F. 
 
 w 
 
 The resistance per nautical mile of any pure copper wire d mils in diameter 
 
 is ^^^?^ ohms at 75 F. 
 d^ 
 
 The resistance per statute mile of any pure copper wire is —-„- ohms at 60° F. 
 
 The resistance per nautical mile of any pure copper strand is — -— dims at 75° F. 
 
 Tiio resistance per nautical mile of a cable conductor is equal to 120,000 
 divided l)y the itroduct of the [lercentage conductivity of the copper and its 
 weight per nautical mile in pounds. 
 
 The resistance of a statute nnle of pure copper weighing 1 ixmnd is 1002.4 
 ohms at 00" K. 51 mils diiimeter copper wire of good quality has a resistance 
 of about 19 (iliiiis. 
 
 The rcHislaiici- of a Htatntc mile of pure cojjpcr weigliing ■?/' pounds is — — olxms 
 
 at 60° V. 
 
 Tho resistance of any pure cojjijcr wire L iii<'lu« in length, weighing n grains, is 
 
 .001516 X L"^ , 
 
 olims. 
 n 
 
 (418)
 
 Miscellaneous Tests and General Information. — Chapter 9. 39 
 
 The weight of any iron wire per nautical mile is — — pounds, f/ being its diameter in 
 
 mils. 
 The weight of any iron w-ire per statute mile is - - pounds. 
 
 The diameter of ;iny iron wire weiglung ic ])ouii(ls per stiitute mile=8.49V'(r 
 mils. 
 
 'Die tlianiett'r of any iron wirt' weigiiini;' ic pounds pel' naulieai iiiile=7.91 V'<c 
 mils. 
 
 Tiie conductivity of ordinary galvanized-ir()n wire averages at)out one-seventh 
 that of pure copper. 
 
 The resistance per statute mile of a galvanized-iron wire is about - ^^ — ohms, 
 at 00° F. 
 
 C.\B1.K TANKS. 
 
 To find the capacity of a circular tank : 
 
 Let r=radi\is in inches of eye. 
 
 /v'^^radius in inches of the tank. 
 d= diameter in inciies of the cable. 
 /(=lieis;lit in inclies of tank. 
 7r=3.1416. 
 
 Total length of cable in feet -^ (R^-r^) -f- 12. 
 
 DISTANCE SOUND, 
 
 Distance from shoi'e — Menfiurcment by sound. — It sometimes happens that 
 the distance of the ship from sliore is required to be known, and a measure- 
 ment l)y sound may be resorted to. For this purpose a gun is hred and the 
 interval between the flash and the sound noted.- 
 
 Let /)=distance in nautical miles. 
 
 T=temperature of air in degree Centigrade; 
 )S=interval in seconds ; 
 then 
 
 7)=0.179 SV1+().(X)374 T. 
 
 Example: A ship fired a cannon, and the sound was heard six and one-half 
 seconds after the flash was seen. The teniperature of the air was 1."" C. 
 Required, tlic distance (/)) of tlie ship. 
 
 /) =0. 179 XGiV 1+0.00374X1") =1.2 nautical miles. 
 
 For converting statute miles to nautical miles, nuiltiply by 1.1528. Nautical 
 ndle and knot are .synonymous, but nautical mile is used to express distance and 
 knot is used to express speed. 
 
 (419)
 
 40 Signal Corps Manual No. 3.— Chapter 9. 
 
 List of Installed Signal Cokps Submarine Cables, September 2. 1915. 
 
 This list is subject to change, however when a submarine cable is replaced a 
 new number is assigned. 
 
 CABLES IN THE UNITED STATES. 
 
 No. 
 
 267 
 311 
 257 
 345 
 256 
 306 
 349 
 266 
 309 
 264 
 350 
 260 
 261 
 346 
 128 
 265 
 
 352 
 348 
 131 
 332 
 351 
 
 135 
 252 
 
 138 
 236 
 237 
 327 
 220 
 307 
 231 
 232 
 274 
 275 
 2:J8 
 239 
 2.W 
 328 
 136 
 320 
 321 
 
 277 
 141 
 279 
 280 
 
 298 
 344 
 299 
 273 
 3 13 
 272 
 312 
 305 
 220 
 3.30 
 Z51 
 295 
 329 
 35;J 
 
 T-ocation. 
 
 Fort Williams— Fort Levett . . . 
 
 ....do 
 
 House Island— Fort Levett 
 
 ...do 
 
 House Island— Fort Preble 
 
 ....do 
 
 ....do 
 
 Fort McKinley — Long Island. . 
 Fort McKinley — Peaks Island. 
 
 do 
 
 ...do 
 
 Fort Levett — Peaks Island 
 
 ....do 
 
 ...do 
 
 Fort McKinley — Fort Lyon . . . 
 do 
 
 NEW HAMPSHIRE 
 
 Fort Constitution — New Reservation. . 
 
 Fort Constitution — Fort Stark 
 
 Fort Stark— Fort Foster 
 
 ....do 
 
 F. C. Station— Cable Pole, Fort Foster. 
 
 M.\SS.\CHUSETTS. 
 
 Long Island — Moon Head 
 
 Long Island— Moon Head (North Cable) . 
 
 Fort Andrews— Fort Revere 
 
 ...do 
 
 . ...do 
 
 Deer Island— Fort Standi-sh 
 
 Fort Heath— Nahant 
 
 Fort Heath— Deer Island 
 
 Fort Standish— Fort Warren • 
 
 do 
 
 Fort Warren— Fort Andrews 
 
 ....do 
 
 Fort Revere — Point AUerton 
 
 Point Allerton— Strawberry Hill 
 
 Fort Strong — Fort Standish 
 
 do 
 
 Fort Strong— Fort Warren * 
 
 Fort Rodman— Richt'lson Point 
 
 do 
 
 RHODE ISL.VND. 
 
 Fort Adams— Fort Wetherill 
 
 Fort Wetherill — Head of Mackerel Cove. 
 
 Fort Greble — Fort Kearney 
 
 Fort (Jetty — Fort tireble 
 
 NEW YORK. 
 
 Fort Terry— Fort Micliie 
 
 Fort Michie— Fort H. (i. Wright 
 
 Fortir. ('.. Wright— iMirtMausfieid, U. I 
 
 Fort H. <i. Wriglu— .Vverys Point, Conn 
 
 ....do 
 
 Fort Slocuin— New Rochelle (Q. M. C. cable) 
 
 Fort Slocura — New Rochelle 
 
 Fort Tolton— Fort Schuyler 
 
 (loveruors Island— Barge oilice (Q. M. ('.cable). 
 
 Kort Wood— Kills Island 
 
 Fori Hunillton — Fort Wadsworth 
 
 do 
 
 Fort Wadsworth— Fort Hancock, N.J 
 
 F.llis Island— Barge Ollico 
 
 (420)
 
 Miscellaneous Tests and General Information. — Chapter 9. 41 
 
 CABLES IN THE UNITED STATES— Continued. 
 
 Location. 
 
 Con- 
 duct- 
 ors. 
 
 Date 
 laid. 
 
 DELAWARE. 
 
 Fort Du Pont — Fort Delaware. . 
 Fort Delaware— Fort Mott, N.J. 
 do 
 
 MARYL.\ND. 
 
 Fort Howard— Fort Smalhvood . . . 
 
 Fort Carroll — Fort Armislead 
 
 Fort \Va.shinglon— Fort Hunt, \'a. 
 Fort Howard— Fort Carroll 
 
 Fort Monroe — Fort Wool 
 
 Around McGinnis I^and (Fort Monroe) . 
 
 NORTH CAROUNA. 
 
 Fort Caswell— Southport . 
 
 SOUTH CAROUNA. 
 
 Fort Moultrie — Fort Sumpter . 
 do 
 
 Fort Dade— Fort De Soto 
 
 Fort Dade — Shaws Point 
 
 Fort De Solo, main base line . . 
 Fort Barrancas — Fort Pickens. 
 
 ....do 
 
 ....do 
 
 Fort McRefr— Fort Pickens 
 
 ....do 
 
 ....do 
 
 Fort McRee — Fort Barrancas.. 
 Fort Taylor— Martello Tower. . 
 
 Fort Morgan — Fort Gaines 
 
 Fort St. Philip — Fort Jackson. .. 
 Fort Crockett— Fort San Jacinto. 
 
 LOUISIANA. 
 
 CALIFORNIA. 
 
 Presidio — Fort Baker 
 
 Fort Baker— Fort McDowell. 
 ....do 
 
 Alcalraz Island — Angel Island 
 
 Fort Barry— Fort Miley 
 
 Fort Rosecrans— Fort i'io Pico 
 
 Fort Baker— Presidio San Francisco. 
 
 WA.SHINGTON. 
 
 ....do... 
 
 Fort Flagler— Fort Casey . . 
 
 Fort Casev — Fort Worden . 
 
 .do. 
 
 44 
 
 44 
 
 6 
 
 Fort Lawton — Fort Ward 1 
 
 Fort Lawton— Fort Flagler 1 
 
 Discovery Bay— Between station (2) and end of aerial line 22 
 
 Discoverv Bav— Between stations (2) and (3) 22 
 
 Fort Columbia— Fort Stevens, Oreg 44 
 
 Fort Columbia — Fort Canby. 24 
 
 Fort Flagler— Fort Worden. •' 10 
 
 44 
 
 (421)
 
 42 
 
 Signal Corps Manual No. 3. — Chapter 9. 
 
 CABLES IN PANAMA. 
 
 No. 
 
 I-ocation. 
 
 Date 
 laid. 
 
 371 
 372 
 373 
 374 
 375 
 376 
 377 
 378 
 379 
 380 
 
 PANAMA. 
 
 Fort Sherman — Fort De Lesseps 
 
 Fort De Lesseps— Crist ol>al Mole 
 
 Fort De Lesseps — Fort Randolph 
 
 Galeta Point — Largo Remo I'oint 
 
 Fort Aniatlor — Naos Island, Fort Grant 
 
 Xaos Island, Fort Grant — Paitillo Point 
 
 Xaos Island, Fort Grant— Batelle Point , 
 
 Naos Island, Fort Grant — Perico Island, Fort Grant 
 
 Perico Island, Fort Grant — Flamenco Island, Fort Grant 
 Flamenco Island, Fort Grant— San Jose Rock , 
 
 CABLES IN THE PHILIPPINE ISLANDS. 
 
 343 
 339 
 340 
 324 
 356 
 
 Malinta Cove— Bavakaguin Point 2 1913 
 
 Fort Mills— Cal.allo Island 20 1913 
 
 CabaUo Island— El Fraile Island 20 i 1913 
 
 Manila— Fort Mills 1 1913 
 
 Fort Frank— Fort Drum 50 1914 
 
 CABLES IN ALASKA. 
 
 Safety— St. Michael (abandoned; partly recovered Aug. 15, 1905) 
 
 Juneau — Skag:\vay (changed to cables Nos. 45 and 46) 
 
 J uneau — Haines ' 
 
 Haines— Skagway ' 
 
 Sitka— Juneau (via Cape Fanshaw) 
 
 Seattle — Sitka 
 
 Sitka — Valdez 
 
 Valdez— Liscum 
 
 Valdez — Seward (changed to cables Nos. 59 and 60) 
 
 Fanshaw— Wrangell 
 
 Wrangell— Hadle y 
 
 Hadley — Ketchikan 
 
 Sitka— Japonski Island 
 
 Seward— Montague Island -' 
 
 \'aldez — Montague Island - 
 
 Cordova— Montague Island 
 
 Juneau — Douglas City 
 
 Cordova — Cape Whiteshed 
 
 1901 
 1901 
 1903 
 1903 
 1903 
 1901 
 1904 
 1905 
 1905 
 1906 
 190(> 
 1906 
 1907 
 1908 
 1908 
 1908 
 1910 
 1908 
 
 » Formed by dividing the Juneau-Skagway cable, No. 44, at Fort William H. Seward and replacing 
 portions near Skagway. 
 ■■! Formed by dividing the Valdez-Seward cable, No. 51, at Montague Island. 
 
 (422)
 
 Chapter 10. 
 requisitions and general-maintenance regulations. 
 
 KKQUISITION.S FOK MAINTENANCK SUPPLIES. 
 
 Except in emergency, all property shipped Iroin any of tlio Sijxnal Corps 
 general supply depots, except the one at Manila, 1'. I., and liic one at Seattle, 
 Wash., is directed shipped by the Chief Signal Ofhcer of the Army. The amount 
 of stock on hand at each of the supply depots is continually and directly under 
 the observation of one oflice. This results in efficiency and economy in the 
 purchase and issue of property. With one office handling all requisitions for 
 fire-control and Signal Service property from all Army posts in continental 
 United States, Hawaii, Porto Rico, United States territory in Cuba, and the 
 Canal Zone, together with all requisitions from the various State militia organi- 
 zations and the voluminous stock requisitions from the various property officers 
 of the different supply depots, it is not difficult to .see that the efficient and 
 expeditious handling of papers and subsequent furnishing of supplies devolves 
 in a great measure upon those authorized to submit requisitions. 
 
 An effort should be made to submit these requisitions semiannually only. 
 However, it is not intended that any restriction whatever be placed regarding 
 the number of requisitions to be submitted. First consideration should be given 
 to having necessary supplies on hand. 
 
 A little care exercised by those who prepare requisitions is the greatest means 
 of assisting those concerned in supplying the desired articles. The great multi- 
 plicity of Signal Corps apparatus throughout the United States and its posses- 
 sions, which of necessity was invariably purchased from the lowest bidder, has 
 been manufactured by various companies and individuals, some of whom are 
 still in business, while others have ceased to manufacture. 
 
 Hereafter post requisitions for Signal Corps supplies will be serially num- 
 bered by means of pen and red ink. The number should be aflixed in the upper 
 left-hand corner of the front sheet and should start with No. 1 at the beginning 
 of each fiscal year. 
 
 All post requisitions for Signal Corps supplies, except those from militia 
 organizations and pi-operty officers of Signal Corps supply depots, should be 
 forwarded to the Department Signal Officer of the department in which the fort 
 for which the supplies are desired is located. The Department Signal Officer 
 will have the requisitions examined, make such revisions as in his opinion 
 should be made, check the .serial numbers, and be sure that all provisions 
 relating to requisitions contained in this manual have been complied with before 
 forwarding them to the Chief Signal Officer of the Army. 
 
 All requisitions from the various State militia organizations will be serially 
 numbered, starting with No. 1 at the beginning of each fiscal year. These 
 requisitions will be forwarded as directed to the Chief. Division of Militia 
 Affairs, War Department. Washington, D. C. who will carry out the provisions 
 relative to examination contained in the preceding paragraph. 
 
 All requisitions from property officers of Signal Corps supply depots should 
 be forwarded direct to the Chief Signal Officer of the Army when such requisi- 
 tions are in accordance with all regulations contained herein. 
 
 (423) 1
 
 2 Signal Corps Manual No. 3. — Chapter 10. 
 
 All requisitions from Signal Corps tield companies should be forwarded to 
 Department Signal Officer, under whose control the company is operating unless 
 by special assignment the company is controlled by another official, in the event 
 of which the requisition should be forwarded to such official who will see that 
 the provisions of this manual have been complied with, and then forward the 
 requisition to the Chief Signal Officer of the Army. Field company requisitions 
 forwarded to department signal officers shall be acted upon by that officer in 
 a manner similar to that prescribed above for post requisitions. 
 
 The following instructions relative to items of property appearing in requisi- 
 tions should be observed : 
 
 («) To aid in furnishing repair parts, a number of tigures illustrating appara- 
 tus in this manual are followed by a list of parts of the apparatus shown in the 
 figure, and in most instances the part may be found in the figure by means of 
 a reference number placed opposite name of the part. In rendering requisitions, 
 where a part is desired, the name of the part exactly as it appears in the list, 
 followed by the letters " P. N.," should be given, immediately succeeded by the 
 part number in the list relating to that particular figure ; also figure number 
 should be entered. In addition, the numeral "3" in parenthesis should appear at 
 end of item in order to distinguish between figures similarly numbered in Signal 
 Corps Manual No. S. It is unnnecessary to name the apparatus unless some 
 doubt exists as to whether the part shown in the list is what is wanted or if 
 the part desired is not listed. AMiere such a condition exists, a full descrip- 
 tion of the part should be furnished. 
 
 It is important to note that in listing parts of some of the apparatus it is 
 absolutely necessary that, in addition to the above, either the manufacturer, or 
 the size, or both be entered. As, for instance : A set of elements for a storage 
 battery could not be intelligently furnished unless the size and the manufac- 
 turer's name are known. This also applies to the jars and sand trays for 
 storage batteries. Bolt connectors and electrolyte for telephone storage bat- 
 teries can be furnished without knowing either the size of the battery or the 
 name of the manufacturer. 
 
 Example : 
 
 8 mica insulators for choke coil, P. N. 7, fig. 6-1 (3). 
 
 4 screws, binding, with nuts, P. N. 8, fig. 6-1 (3). 
 6 nuts and washers for P. N. 7, fig. 6-2 (3). 
 
 1 scale, P. N. 36, fig. 4-30 (3). 
 
 (ft) In listing wood screws, type of head, metal employed, length, and 
 gauge size should be entered in the order named after the word " screws." The 
 word " bright " should not be used to indicate plain iron. Example : 
 
 li screws, H. H. i)rass, lA", No. 30, gross. (R. H. means round head.) 
 '.i screws, F. H. iron, 1", No. 8. gross. (F. H. means flat head.) 
 {(■) In listing machine screws the word "machine" should follow the word 
 ".screws" and the type of head. iii('t;il employed, length, gauge size, and num- 
 ber of threads per iiicii should follow in the order named. 
 Example: 
 
 2 screws, niiicliine, F. II. iron, lA", 8-32, gross. 
 6 screws, nuidiine, H. H. brass, 1", 10-24, gross. 
 
 5 screws, machine. Fillister, Hd. iron, 1", 12-24, gross. 
 
 Whore screws having a si)eciMl finish such as dull nickel are desired the name 
 of finish should follow the name of metal and wiiere dimensions (other than 
 number of Ihrejids per inch) are not of connnercial standard a sketch illus- 
 trating such dimensions should accompimy the requisition. 
 
 (424)
 
 Requisitions and General-Maintenance Regulations. — Chapter 10. 3 
 
 (d) Tho (liinonsions iuid inatorial of hrushos for motors and generators 
 should be furnished, and if flexible wire lead forms a part of the brush desired, 
 the word " brushes " in the item should be followed by the iihrase •' with pit: 
 tails." The name of the manufacturer of the apparatus with which the brush 
 is to be used should be given, also the size and niaimfacturer's serial number 
 of tlie apparatus with which the brush is to be used. 
 
 Example: 
 
 4 brushes (one set), carbon, i\" x 1" x 2", for motor end of B. C, \ kw., 
 
 motor generator No. 3421. 
 2 brushes, with pig tail (one set), carbon, \" xl" xli", for generator 
 end of N, G., i kw., motor generator No. 6415. 
 (r) A full description of all wire furnished by the Signal Corps, together 
 with proper designation of each of the various types will be found in Chapter 
 VIII of this Manual. 
 Example: 
 
 2 wire, buzzer, miles. 
 3(W wire, fixture, 40 mils. feet. 
 200 wire, weather-proof, 128 mils. feet. 
 (/) In listing fuses, the Signal Corps type number and the ampere rating 
 should be given. The Signal Corps type mnnber may be determined by referring 
 to Chapter VIII of this Manual. If fuses desired do not cin-respond with any 
 of the Signal Corps types, the name of manufacturer of apparatus with which 
 it is to be used, the ampere rating desired, and if practicable, a sample shf)uld 
 be furnished. 
 Example: 
 
 10 fus(>s. type 3. 20 ampere. 
 20 fuses, type 9. 1 ampere. 
 
 50 fuses. 1 ampere, for C W. conimon baity, telephone switchboard, sam- 
 ple attached. 
 20 fuses, 5 amp., for Coke 5-S can terminal. 
 (p) In entering items of screw anchors, the gauge size of the screw to be used 
 with the anchor and the length of anchors desired should be shown. 
 Example: 
 
 100 screw anchors for No. 10 screws, 1". 
 (/() Either a sketch or principal dimensions of toggles requisitioned should 
 be submitted. 
 Example: 
 
 50 toggles, bolt,=i" X approx. 3"; cross piece 24" long. 
 (0 Items of switches should show type (knife or snap) and ampere rating. 
 Items of snap switches should also show whether double pole, single pole, or 
 three way. Items of knife switches should also show whether double pole, 
 single pole, or triple pole, and whether double or single throw. If fused 
 switches ai'e desired it should be so stated. 
 Example: 
 
 2 switches, snap, 10 ampere, D. V. 
 1 switch, knife, 15 ampere, S. P. D. T. 
 When knife switches, without bases, for mounting on switchboards, are 
 desired, reference should be made to either Signal Corps drawing 381 E-1 
 or Signal Corps drawing 382 E-1. 
 
 (425)
 
 4 Signal Corps Manual No. 3. — Chapter 10. 
 
 ij) Where heat coils are listed, the name of the manufacturer or a sample 
 should be furnished. 
 
 Example: 
 
 50 heat coils, W. R. Growler. 
 100 heat coils, sample attached. 
 
 (/.•) The great variety of cords used with apparatus supplied by the Sipiial 
 Corps makes furnishing of satisfactory renewals an extremely difficult one. 
 An effort has recently been made to standardize all cords and cord terminals, 
 and it is believed that those entering renewals on requisitions will find the Sig- 
 nal Corps number of cord desired by referring to chapter 8. It is intended that 
 in the future purchase of apparatus utilizing cords, that manufacturers will 
 be required to select cords to be furnished from drawings in accordance with 
 (••ird illustrations shown in chapter 8. If possilile, cords should be designated 
 by mmiber only. If this is impossible a sample should bo submitted. 
 
 Example: 
 
 6 cords, No. 4. 
 4 cords, No. 5. 
 
 8 cords for obsolete distributing switchboard, as per sample inclosed. 
 (/) In submitting requisition for cable to be used in extension of systems 
 it is desirable to have the necessary lengths entered, as a record of short 
 lengths of serviceable cable is kept in the office of the Chief Signal Officer of 
 the Array and such information results In the issue of lengths that otherwise 
 take up valuable room at supply depots. If the cable is to be trenched it 
 should be so stated. 
 Example: 
 
 800 feet cable, type 213, lengths 350-220-230. 
 325 feet cable, type 401, length 325. 
 1,200 feet cable, type 217, trenched. 
 
 CAKK OF POST TELEPHONE AND SMALL ARMS TARGET RANGE SIGNALING SYSTEMS. 
 
 General Orders No. 90, 1910, which pertain lo the maintenance of post 
 telephone and small arms target range signaling systems, is entered below 
 for the guidance of all concerned. 
 
 Tiie following instructions for the operation, maintenance, and care of post- 
 telephone systems and the buzzer and connnunication systems of target ranges 
 installed by the Signal Corps are publish(>d : 
 
 1. The route and location of duct lin(>s and troncluMl cabk>s on posts and 
 fither military reservations will be carefully recorded, and copies of these 
 records furnished to the respective post quartermasters. Officers in charge 
 of construction will in all cases see llinl no excavating or trenching is <lone 
 on any post, or oth(>r military reservation, without jinniously ascertaining 
 the location of the cables and ducts installed thereat and determining that 
 these will not be injured by the contemplated work. 
 
 2. It will be the duty of the officer resi)onsible Cor Signal Corps property 
 to see that the cables are projierly trenched and that the manholes and outlets 
 sire at all times properly covered with soil to the extent intended. Heavy 
 rains or other cau.ses nuiy expo.se any of these, and thereby subject them to 
 damage. The outlet case pipes will be kept in their original position by 
 maintaining ilic soil about them in m tirni coinlit ion. 'Die manholes are to be 
 c-oVered with (5 inches of soil, and no cable or conduit is intended to be nearer 
 tlutn 18 inches to the surface. If any cables are injured by exposure, immedi- 
 
 (426)
 
 Requisitions and General-Maintenance Regulations. — Chapter 10. 5 
 
 ate steps will be taken to repair them, (tr if it is Impossible to do this, tempo- 
 rary steps will be taken to i)revent further injury, ami report made through 
 proper chaiuiels to the Department Signal Olliccr. 
 
 3. The greatest care will be exercised in handling lead-covered cables, as 
 tlie paper which forms the insulation of the core takes up moisture very readily, 
 in which event the cable rapidly becomes unserviceable. 
 
 4. Underground conduit systems at posts will be connected when practicable 
 to the post drainage system, and underground conduit systems on target ranges 
 will also be provided with adeipiate drainage. It is necessary to keep surface 
 water from draining into outlet case pipes, as the outlet itself is not intended 
 to withstand constant submerging. 
 
 5. To insure that the target range equipment is complete and in a condition 
 to give satisfactory service for the target season, the officer re.sponsible for 
 this equipment will see that the material is reinstalled and connected and a 
 thorough test made of all the equipment one month or more before the com- 
 mencement of the target-practice season. If any material proves defective an 
 iiinnediate report will be made fo the Department Signal Odicer, in which the 
 nature of any defect will be fully stated, so that the material and labor neces- 
 sary for its correction may be provided before the opening of the practice 
 season. 
 
 6. At the end of the practice season all buzzers, strap keys, annunciators, 
 master switches, and telephones which might be stolen or become damaged by 
 exposure will be removed from their points of installation to the storehouse. 
 
 7. Doors of cable or distributing boxes placed outside of buildings or on poles 
 will be kept closed at all times when not in use. 
 
 8. All aerial cables will be jirotected by fuses so that lightning or other 
 foreign electrical currents may not enter the cable under any circumstances. 
 Particular care will be taken that these fuses are in serviceable condition at 
 all times. 
 
 INSPECTION OF POST TELEPHONE AND SMALL AKMS TARGET KANGE SIGNALING 
 
 SYSTEMS. 
 
 An extract of G. (). 5, W. D., 1913, follows : 
 
 The systems at interior posts will be inspected twice annually by a competent 
 inspector having technical knowledge of nuigneto and conunon battery systems, 
 these inspections to be made, if practicable, during the two months prior to 
 July 1 and .January 1 of each year. 
 
 The report covering these inspections will be prepared in triplicate on Signal 
 Corps forms Nos. L'Ul) and 211. one copy to be retained for the files of the 
 signal officer of the post, and the other two forwarded, through military 
 channels, for the files of the department signal officer of the Territorial division 
 concerned and tlie Chief Signal Officer of the Army. 
 
 Department signal officers of the Territorial divisions will apply for the 
 necessary orders to have the above-mentioned inspections made. 
 
 MAINTENANCE TEST. 
 
 In the maintenance of any electrical system, especially where underground 
 or aerial cable is involved, it is advisable to occasionally ascertain the insula- 
 tion resistance of the circuits. 
 
 With the important fire-control .systems at our seacoast defenses, it is re- 
 quired that this action be taken once a month, and, although it is not required 
 for post-telephone and small-arms tai-get-range systems at interior posts, it is 
 .advisable to make an occasional test incident to the general maintenance of 
 
 46581°— 17 28 (427)
 
 6 Signal Corps Manual No. 3. — Chapter 10. 
 
 the systems. By this means a partial fault, which in time might result in 
 several circuits becominc; inoperative, may be detected. 
 
 There are several methods of making the test, the quickest and simplest being 
 with an instrument termed " megger." The Signal Corps has a limited number 
 of these instruments, and, although they are not regularly issued for the 
 purpose, department signal ofiicers usually have one that can be furnished 
 temporarily. 
 
 Prior to making this test, the lines should be tested by operating the appara- 
 tus connected thereto, and any defects, however trilling, should l)e noted. 
 
 Tlie megger. — The megger shown in figure 10-1 is a direct reading instru- 
 ment, the type usually furnished having a scale 0-.5 megohms. 
 
 Current for its operation is obtained by means of a hand-driven generator 
 forming a part of the instrument. In revolving the armature the revolutions 
 per minute should be increased until the crank tends to slip. The slipping 
 effect is caused by a mechanical governor which is intended to maintain a 
 constant speed. 
 
 
 I 
 
 
 Fn 
 
 M 
 
 xJ4 
 
 ^ '■ 
 
 CIRCUITS 
 
 Fig. 10-1.— MEGGER. 
 
 The lest consists of measuring, to limit fixed by instrument used, the ins»i- 
 hiiioM between each conductor of tin; system and ground. It is not intended 
 liiat the iiiu^s shall be disconnected either at instruments or at cable terminals. 
 An exception to this is made in testing lines of a post-telephone system. These; 
 line.s are ordinarily tested at the lightning-arrester strip, where, by insertion of 
 a .special plug, circuit to teleplione switchboard is disconnected and outgoing 
 line is coiin<?cted to ground tlirougli the testing instrument. 
 
 ('are should be taken not to be mish>d into believing lini; wire or cable is 
 defective when low insulation is due to leakage between carbons of lightning 
 
 (428)
 
 Requisitions and General-Maintenance Regulations. — Chapter 10. 7 
 
 arresters. When power lines are tested, switches l),v which the circuits are 
 controlled should be openeil. 
 
 In niakinj^ the tests with me}:;rer attacii a wire to binding post of megger 
 marked "ground," connecting other end of wire securely to sheath of cable 
 being tested. Attach a well-insulated wire to the remaining binding post of 
 the megger for connection to lines to be tested, and be sure that the instrument 
 is well insulated from earth. 
 
 Revolve generator crank handle, increasing speed of rotation until crank 
 tends to slip, and with test wire make contact with lines to be tested. With 
 lines in good condition, rapid progress, can be made, as it is only necessai-y to 
 touch forcibly each line, going from one to another in rapid succession. 
 
 The maintenance test can be made with a voltmeter. Sufficient number of 
 dry cells should be used to obtain nearly maximum scale reading. A .special 
 voltmeter having a 100,000 ohm coil was originally furnished for making main- 
 tenance tests. This voltmeter is termed " post testing voltmeter " and is shown 
 in figure 10-2. It will be noted that specific value of Insulation can not be 
 
 I 
 
 Fig. 10-2— VOLTMETER, POST TESTING. 
 
 obtained unless resistance of voltmeter coil is known and that the higher the 
 resistance of this coil, the higher the value of insulation that can be measured. 
 If a voltmeter is used in making maintenance test, proceed as follows: 
 (1 ) Try the line, for actual operation, and note any and all defects, however 
 trifling. 
 
 (2) Connect the + terminal from the battery to the ground, utilizing the 
 sheaths of cable being testetl. 
 
 Be sure that you have a good ground. 
 
 (3) Connect the other outside terminal of the battery to one side of the 
 voltmeter. 
 
 (4) Connect a well-insulated testing lead to the remaining terminal of the 
 voltmeter, and see that both the voltmeter and Ilic liattery are w(>l! insulated 
 from the ground. 
 
 (5) Apply the free end of the testing lead to the grounded end of the battery 
 and note the reading, which will be called V and should cover n(virly the whole 
 scale of the voltmeter. 
 
 (6) Remove the testing lead referred to in ."> from the grounded battery 
 terminal and apply successively to the terminals of the line which is to be 
 tested, the reading being noted. These readings are called V,. 
 
 (7) The actual insulation resistance of this circuit may be determined by the 
 formula ; 
 
 •T'l) 
 
 
 V. 
 
 (429)
 
 8 Signal Corps Manual No. 3. — Chapter 10. 
 
 Rx is the insulation resistance, and lig is tlie resistance of tlie voltmeter coil 
 and circuit, which will be found inside the lid of the case and which varies 
 slightly with individual instruments. 
 
 Should any of the short lines employed show an insulation to ground of less 
 than 1 megohm, steps should be taken to ascertain the cause of such condition. 
 
 The maintenance test may be applied at any point in a circuit. 
 
 Moist atmosphere will cause low reading of the megger and high reading of 
 a post-testing voltmeter, due to increased surface leakage, and tests will ordi- 
 narily be made when the atmosphere is comparatively free of moisture. 
 
 If it is thought that serious leakage occurs when atmosphere is comparatively 
 moist, the difficulty should be remedied and special tests should be made during 
 the damp period to determine this question. 
 
 If condition cited in preceding paragraph is found to exist, disconnection 
 of instruments or terminal boxes will usually locate the leak ; but it is neces- 
 sary that any leakage which may develop be corrected whether it be in cable, 
 outlet boxes, switchboard, or in the instruments. 
 
 Leakage in the conductors of cables is obviously more serious than any 
 other form of fault and great care should be taken in order to be sure whether 
 faulty conductors exist by eliminating every other source of trouble before 
 reporting the cable defective. It will frequently be found that faulty insula- 
 tion develops gradually, and that readings from month to month will change 
 in such a way as to make it possible to forecast the working life of a con- 
 ductor. Arrangements should be made for the correction of such a condition 
 as soon as practicable after it is positively known to exist. 
 
 If the foregoing instructions are faithfully followed no absolute interrup- 
 tions of important lines of communication should occur except from unusual 
 accidents, due to inadvertence. 
 
 MAINTENANCE INSPECTION. 
 
 At least once a year a maintenance inspection should be made of all appa- 
 ratus of post telephone and small arms signaling systems, by person or persons 
 designated by local post signal officer. 
 
 This inspection, consists of an examination of all ai)])aratus of (he systems. 
 
 Contacts should be examined and made positive, defective telephone nioutli- 
 pieces replaced, and inefficient instrument circuits repairetl before trouble 
 actually occurs. 
 
 All external connections to appai*atus sliould be examined for possible cor- 
 rosion. A strip of j)aper should l)e drawn between platinum contacts for the 
 ]»urpose of cleaning them and to make sure the contact is properly made. 
 Only hard-surfaced pajjcr should be used, otherwise paper lint may collect 
 and cause jioor or open contact. 
 
 ( (rdiiiarily, telcplione-traiisiiiitlcr shells should not be oiieiied. If trouhU' 
 arises due |o defeciive butloiis the Irniismitter so alfecled shoidd be "tui'iied 
 ill" to a Signal Corps snpjily depot for i-ei)air and return aUvv having re- 
 ceived |>io|per antliorily for such action. Thos(> making this inspection sliould 
 be provided with an inspector's pock«>t kit. described in chapter S; a telephone 
 receiver; a jiiece of ehainois skin; a jutrtable voltmeter, or portable voltam- 
 nieter ; atid a couple of tiexible testing cords to wiiicli standard si»ring clips 
 have f>een attached. ( >ne or two dry cells of battery will t'recpieiilly be foiuid 
 a c(tnv<'nient adjuiK-t lor use in testing for identification. 
 
 The inspection described above is a matter of conmiercial routine which is 
 I»racticed by all commercial eoiii]»anies alteniiiling to give .satisfactory service 
 
 (430;
 
 Requisitions and General-Maintenance Regulations. — Chapter 10. 9 
 
 and is al)S()liit('ly lu'ccssiiry for tlu' prevention of tlie various serious evils to 
 which tile hesi of electrical installations are liable. 
 
 MONTHLY STORAGE-BATTEUY REPORT. 
 
 This report is forwarded to the Department Signal otficer at the end of each 
 month by the post signal otlicer. 
 
 The report consists of one copy of Signal Corps form 260 dtily acconiplislied 
 for each Signal Corps storage battery attached to the post. Full instructions 
 relative to readings to be taken and recorded are printed on back of the form. 
 
 MAINTEN.XNCE OF MOTOR GENERATORS. 
 
 The motor generator should be kept covered when not in use. Care in this 
 particular will save the machine from damage by du.st. The pneumatic duster, 
 which is supplied to keep the windings clear of copper particles which may be 
 thrown off by the commutators, should be frequently used. Inspect the machine 
 each time before .starting, to make sure that it is clean. 
 
 Bcarhif/.s. — The bearings should be filled with tlie highest grade of dynamo 
 oil to such a height that the surface of the oil comes above the lowest point of 
 the oil rings. If the bearings are too full, oil will be throun out along the shaft 
 and get into the armature windings and commutator, eventually causing trouble. 
 The oil shotild be renewed semiannually, and in all cases should be filtered 
 before using again. It is preferred that oil should not be used more than once. 
 
 Keep dry and clean. — Keep the machine dry and clean. An accumulation of 
 dust or the dripping of water on any part of it should not be i>ermitted, as it 
 will cause serious trouble in a very short time. The carbon dust from the 
 brushes should not be allowed to accumulate on the brush holders, commutator, 
 or other parts. 
 
 By means of a bellows or air blast the set should be thoroughly and frequently 
 blown out, inspection being made each time to determine that all the dust and 
 dirt has been removed. Satisfactory results can not be expected if it is not 
 properly cared for and given attention at frequent intervals. The life of any 
 machine is increased in direct proportion to the attention it receives. 
 
 Starting. — Before starting the motor generator set see that all oil wells have 
 a proper amount of oil and that the brushes are properly adjusted. With motor 
 generator set having a direct-current motor, see that the handle of the auto- 
 matic starting box is in the "stop" position before closing the motor main 
 switch. 
 
 After being sure that everything is in readiness-, close the motor main switch 
 and start the machine slowly by moving the handle of the automatic starting 
 box step by step toward the " start " position. Be sure that all oil rings revolve 
 freely. The lever of the motor starting box should never be stopped for any 
 length of time until the last step has been reached. When this step has been 
 reached the magnetic holder, the windings of which are in the field circuit, 
 should hold the lever at the last stop. If for any reason the magnetic holder 
 fails to hold the lever, or shoidd it l)e desired to stop the set before the last 
 .step has been reached, the motor main switch should be opened befoiv tdlowing 
 the starting-box lever to i-eturn to the " stop " position. 
 
 Regulate the voltage of generator bj; means of the generator field rheostat. 
 
 .\fter imtting the generator in circuit, feel all the connections of both machines; 
 if any one is warmer than the other the connection is imperfect ami should be 
 cleaned ami tightened. 
 
 (4.S])
 
 10 Signal Corps Manual No. 3. — Chapter 10. 
 
 Cnro slioukl be taken that the field cireuit t»L a motor is not oiK^ned. as there 
 is (laiitrer of the field coils iieinu' punctured. If it becomes necessary to break 
 the lield circuit, it sh(»uld be accomplished slowly, allowing the arc to die out 
 trradually. 
 
 Stopping o motor-generator set having a direct-current motor. — The follow- 
 ing points should be observed in shutting down the motor-generator set : 
 
 Disconnect the leads to the generator by means of switches and circuit 
 breaker on power switchboard ; move the generator field rheostat handle to the 
 position showing the lowest voltage o])tainable ; open motor main switch ; be 
 sure that magnetic holder on motor starting box releases the lever and that It 
 returns to the " stop " position. The latter will not occur until the motor gen- 
 erator .set slows down perceptibly. This is due to the counter-electro motive 
 force of the set, which continues to energize the magnetic holder after the 
 current is " cut off " from motor. 
 
 Never stop the set by releasing the lever of the aiitomatic starting box before 
 opening the main switch, as it is apt to burn the contacts on the starting box and 
 may punctiu'e the insulation of the field windings. 
 
 After the set has been stopped, wipe off all oil and dust, and if set is not to be 
 again operated within a reasona)>le period of time, the canvas case should be 
 placed over it so as to protect the machine from dampness and dust. 
 
 Care and attention of commutators. — The commutator surface should be kept 
 clean and smooth. A cloth with a little vaseline may be nsed to lubricate and 
 clean it, care being taken that it be wiped clean after every treatment. 
 
 A rough commutator may be smoothed by tising No. 00 sandpaper held against 
 it midway between the brushes while the armature is rotating slowly. Before 
 applying the sandpaper, the brushes should be raised. Never apply emery cloth 
 to a comnuitator. 
 
 A commutator that is eccentric or that has high spots should be turned true. 
 As the turning tool does not leave a sufficiently smooth surface for proper ojiera- 
 tion, No. 00 sandpaper, mounted on a wooden block fitted to the conunutator, 
 should be applied until the surface is perfectly smooth. Inspect the surface to 
 see that the coi)per has not been burred over from segment to segment, and 
 remove by a scraper any particles of copper which might be found between the 
 segments. 
 
 Not infrequently flat spots on the comnuitator are started by a flash-over 
 developing from an open circuit in windings, or are caused by a dirty conunu- 
 tator. These flat spots passing under the brushes give rise to loud noise and 
 objectionalile sparking. They can not be removed properly by sandpaper, and 
 when they develop the commutator should be turned, as described above. The 
 hinsh holders should be so located on the brush studs that the rings of contact 
 ma<le by the carlmns of one set of brush holders overlap those made by the next 
 adjacent set. 
 
 Jirnshes. — The copper plating on th(> brushes should be kept cut back, so as 
 not to come in contact with the connnulator. A siiinll amount of conunutator 
 wear will be compensated for in the brush holder by the brush slipi)ing througli 
 the holder. Large conunutator wear should be compensated for as follows: 
 
 Reset the brushes in the following mannei- : ri;ice a narrow strip of paper 
 around the commutator, having the two ends meet. After I'cnioving this paper 
 di\i(l(' It in as many i»arts as there are jioles. marking e;icii division, then place 
 the strip around the (■<tiinnutator, sticking it on willi a lilllr siicllac ;it several 
 points. In this way (lie i»r(tper spacing of liir hrnshcs is ohiained. 
 
 Throw the tension spring back as far as possible. Turn the brush h(»lders on 
 the studs until the brushes are I'adial. Then claniji the brush holders in this 
 
 (432)
 
 Requisitions and General-Maintenance Regulations. — Chapter 10. 11 
 
 po.sition. Tlic distance between the holders and the commutator surface in all 
 ras«'s sliduld he approximately the same, and should in no case be nearer th»* 
 (•(•niniutator than three-sixteenths of an inch. If for any reason the brushes 
 of any stuil do not come on the lines of the strip of paper wrapped around the 
 connuutator, move that stud so that the brush will come on the line. Now 
 si)rinfj; the tension sprinj^ Inick into place and ai)ply the proi)er tension. In all 
 cases such a pressure should be applied as to jrive appntxiniately 1 pound per 
 S(|uare inch of brush contact. 
 
 By using a tine jii'ade of sandpaper, the brushes sliould be sanded to the curv- 
 ature of the commutator. Cut the sandpaper into strips a trifle wider than one 
 l»rush. Place this under the brush with the smooth side next to the commutator, 
 then draw the sandpaper back and forth imder the brush, keeping it against 
 the commutator, so that the brush will have the curvature of the comunitator. 
 End the sanding process by drawing the paper under the brush holder several 
 times in the direction of rotation only. Blow out all carbon dust and wipe off 
 the connections, special care being taken to .see that the connuutator is cleaned. 
 
 Spai-kirif/ may be caused by — 
 
 (a) Brushes not being set at the proper place. 
 
 ( b ) The brushes not being fitted to the commutator. 
 
 ((■) The bru.shes not having the proper pressure on the commutator. 
 ((/) S(tme brushes having excessive pressure, and thus taking more than their 
 share of the current. 
 
 (c) The brushes being burned on the ends, due to excessive overloads having 
 occurred. 
 
 (/) A rough connuutator. 
 
 ((/) A high, low, or loose connuutator bar. 
 
 (/O High mica. 
 
 (0 Oily or dirty connuutator. 
 
 (j) Open circuit in the armature winding or loose connections between the 
 armature conductors and the comniutat(jr tangs. 
 
 Hot or glowing bru.shes are due to excessive current density at the brush 
 contact surface, caused by (jverloads, incorrect brush position, dirty commutator, 
 or the picking up of copper. The picking up of copper embeds in the surface 
 of the brush small particles of copper, thus causing a low resistance path 
 between the brush and the commutator, and permitting a heavy flow of current 
 at this point, thus developing glowing brushes. This difficulty may be removed 
 by drawing a piece of fine sandpaper across the contact surface of the brush. 
 
 OverJuathif/ of the commutalor may be due to — 
 
 (a) Overloads. 
 
 (6) Excessive brush pressure. 
 
 (c) Sparking. (See general subject "Sparking.") 
 
 Overheating of beariiu/s may be due to — 
 
 («) Defective alignment. 
 
 (b) Failure of oil rings to revolve. 
 {(■) Rough bearing surfaces. 
 
 {(I) Bent shaft. 
 
 (c) Not enough oil. 
 (/) Poor grade of oil. 
 
 (f/) End thru.st. due to improper leveling. 
 
 (h) Large unbalaneed magnetic pull, due to the armature not being central 
 with the frame: generally resiUting from excessive journal wear. 
 
 (433)
 
 12 Signal Corps Manual No. 3.— Chapter 10. 
 
 Throwing or leaking of oil is frequently caused by — 
 
 (a) The oil being too high in the bearings. 
 
 (b) The plug which is screwed into the oil well drain not being tight. 
 
 (c) Shaft not being level. 
 
 Excessive field heating. — If one of the field coils is warmer than the others the 
 trouble will usually be found to be a short circuit. This may be detected by 
 taking the voltage drop across the terminals of each individual coil. 
 
 An unloaded motor generator should start when the lever of the motor starting 
 box is in contact with the second or third segment. If this does not happen, the 
 trouble may be due to an open circuit in the field or armature windings, in the 
 starting box, or imdue friction in the set. 
 
 While the foregoing pertains principally to motor generator sets with direct- 
 current motors, it applies to motor generator set having alternating-current 
 motors, except that with the sizes usually installed by the Signal Corps the 
 motor is started by merely closing a D. P. S. T. knife switch, no auxiliary 
 starting apparatus being necessary. 
 
 POWER SWITCHBOARD MAINTENANCE. 
 
 All switch parts should be kept bright and clean, and care should be taken to 
 see that all nuts are tight and that no corrosion exists at the contacts. 
 
 The voltmeter switch should be inspected frequently, to see that all con- 
 tacts are positive. Particular attention is invited to the necessity for regu- 
 lar inspection of all connections in the rear of these switchboards, in order 
 that trouble which might arise from loosening of parts or similar causes may 
 be anticipated. While particular care is taken by the Signal Corps to avoid 
 the possibility of the corrosion of terminals, (hie to the use of .soldering salts 
 and to other causes, it is well to examine the lugs frequently during the 
 first year's operation, since trouble from this cause may occur. It is pointed 
 out that a high resistance, such as might be caused by a defective lug in tlie 
 circuit of the telephone storage battery, may be the cause of cross-talk. 
 
 Separate fuses for all circuits should be kept on hand in ample quantity, and 
 if at any time, through a series of accidents, a number of fuses have been 
 blown and the reserve supply becomes low, special requisition should be 
 sent in without delay, since only under conditions of grave emergency should 
 inclosed fuse terminals be bridged by an open wire link. If this must be 
 done, connection should be made in the rear of the board. When such a 
 fuse is blown, the switchboard is likely to be defaced in a manner which is 
 beyond remedy, aside from the possible damage to the terminals. It is intended 
 that the .supply of fuses should be of sufficient magnitude to make such a 
 contingency extremely unlikely. 
 
 DRY BATTERIES. 
 
 As stated iti chapter 1, all cells furnished by the Signal Corps bear the 
 date of manufacture, and no cell except the reserve typ<> should he installed 
 for .serious work that is more than 18 months old, unless test with the am- 
 meter and voltmeter shows that it has a voltage of at least 1 or that the 
 ampere reading will he at least 2. 
 
 The cells should be stored where the temperature is moderate, dry, and 
 oven. When installed, care should be taken to keep the cardboard covers 
 as (hy as possilile; also to keep the cells separated from each other by a 
 slight air space. 
 
 (434)
 
 Requisitions and General-Maintenance Regulations. — Chapter 10. 13 
 
 TOOLS FOK MAINTENANCE PURPOSES. 
 
 Tool kits and line construction tools appropriate with size and nature of 
 systems will be issued for nialiitenance of post telephone aii<i sniall-ariiis 
 target range signaling systems at interior posts. 
 
 Signal officers should use carefid .judgment in the assortment of tools held 
 at a post for this puri)ose and should take steps to have " turned in " to a 
 Signal Corps supply depot tools' that appear to be superfluous. 
 
 MAINTENANCE OF FIELD EQUIPMENT. 
 
 liicszer tvhen in constant use. — As soon as possible after the daily drill, each 
 chief of section should examine his service buzzers and test them out for 
 trouble, whether or not they have been in satisfactory condition at the morning 
 drill or not. This must be done to avoid any minor faults, such as loose key, 
 key short-circuiting, broken connections in line and ground circuits, loose con- 
 nections to receiver and transmitter, etc. This test should be made in con- 
 junction with the circuit through cart, by plugging in one buzzer on the cart, 
 the other to ground through field wire on drums, making certain that the 
 brushes on each drum make good connections to their commutators. 
 
 Learn how to attach reserve cells, which may be necessary when Ever Ready 
 cells can not be obtained. 
 
 The receiver and transmitter compartment of buzzers issued in the post 
 should be lined with sheepskin by company mechanics. Buzzers manufactured 
 in future will be provided for in this respect. 
 
 Wire carts. — When on march lubricate axles daily. When in garrison lubri- 
 cate twice weekly. 
 
 Cart chains and clutches should be thoroughly cleaned at least once per 
 week. When cleaning chains replace loose or broken cotter pins. 
 
 Annually, or semiannually, the wire carts should be taken apart, thoroughly 
 cleaned, and examined for minor faults that will develop. They should be 
 repainted while taken down, and spare parts should be substituted for those 
 badly worn. 
 
 In gflrrison the carts should be parked in sheds such as Field Artillery use. 
 If it is impossible to shelter the carts in the field, the cart paulins should be 
 spread over carts and secured to tongue, mogul springs, and wheels. 
 
 If. due to any cause, the field wire has been reeled up on the drums in poor 
 shape, it should be rewound in a shipshape manner, as otherwise it may be so 
 loose as to wrap itself around the cart axle at the next drill. 
 
 Cart chains of obsolete type wire carts. — When in constant use wipe off 
 chains with a rag and then apply graphite preparation at least every third day 
 and oftener if the chains are covered with mud. 
 
 The sprocket chains on wire carts should be removed and thoroughly cleaned 
 at least once in three months and more often if constantly in use at maneuvers. 
 After removing the chain, wash off all old grease and accumulated sand, using 
 a stiff brush and gasoline or kerosene. When apparently clean, coil the chain 
 in a pan or bucket, covering it with kerosene or gasoline and allow it to stand 
 for several hours if time will pernnt. If the chain has been cleaned in kero- 
 sene, it should finally be rinsed with gasoline, which will then evaporate in a 
 few minutes, leaving the chain clean and dry. Next prepare a lubricant con- 
 sisting of the following ingredients: Ten parts of the best beef tallow, two 
 parts of heavy oil, and one part of powdered graphite ; these ingredients to be 
 heated in a heavy pan sufficiently for the lubricant to flow freely, but not enough 
 heat to draw the temper of the steel. The chain should be coiled in the pan and 
 
 (435)
 
 14 Signal Corps Manual No. 3. — Chapter 10. 
 
 allowed to remain in the warm lubricant for at least half an hour. This process 
 insures that the lubrit-ant will penetrate every part of the chain, includiufi the 
 inside hearinjj; surfaces of the bushings and rollers. 
 
 When the chain has been removed for any reason it should be replaced with 
 the same side toward the sprocket, so that it will run in the same direction as 
 before removal. 
 
 Keep pairs of sprockets in perfect alignment. 
 
 Wire pikes. — Examine daily the hooks on wire pikes in use and replace those 
 badly worn. Worn hooks tear insulation from field wire, and are frequently 
 jerked from the hand. 
 
 Field irire. — When field wire on which the insulation is defective is used on 
 damp ground, moisture causes the wire to rust and break easily. Keep the 
 insulation repaired daily by use of tape. 
 
 Leather. — Do not experiment with the preservation of leather. Obtain and 
 follow strictly the instructions issued by the Ordnance Department for clean- 
 ing and preserving leather. Leather is often ruined by use of too much oil. 
 
 (i43aj
 
 Chapter 1 1 . 
 
 LONG SUBMARINE CABLES; SUBMARINE TELEGRAPHY; TESTS OF 
 SUBMARINE CABLES. 
 
 The oonstniction, characteristics, and manner of splicing submarine cable 
 employing Iiidia-rubber compound as an insulating medium, are descrii)ed 
 in chapter 4 of this manual, consequently it will not be repeated in this 
 chapter because what has been stated in this connection ai)plies also to long 
 submarine cables. 
 
 It is believed that the Signal Corps laid the first long submarine cable that 
 had rubber compcanul for insulation instead of gutta-perrha. The cables re- 
 ferred to are the submarine cables of the Washington-Alaska Military Cable 
 and Telegraph System, the longest single stretch of which is between Seattle 
 and Sitka, approximately 1,()S5 miles. This cable has been in use over 11 
 years, the service it has rendered being satisfactory. 
 
 With the long trans-Atlantic cables gutta-percha is employed as the in- 
 sulating medium instead of rubber compound described in chapter 4. (Jutta- 
 percha has two important characteristics which reconunend it for such cables, 
 one is that the deteriorating effect is less than rubber compound provided it 
 is kept constantly submerged, and the other is that it will better withstand the 
 enormous pressure to which a cable is sul)jected in very deep water. With 
 some of these cables each insulated conductor is wrapped with a brass ribbon, 
 the gutta-percha being first covered with a serving of tape or spun thread. 
 In other respects the cable is constructed' in accordance with description in 
 chapter 4. The brass ribbon has proved effective where trouble has been 
 occasioned by the toredo, a submarine boring animal. This little pest, which 
 exists in the Atlantic Ocean and eastern seas, forces itself between the steel 
 armor wires and bores through insulation to conductor, thereby causing a 
 ground or at least a heavy leak. 
 
 SPLICING GUTTA-PEUCHA INSULATION CABLE. 
 
 In splicing cable with gutta-porcha insulation, the armor and conductor are 
 treated as described in chapter 4, but the gutta-percha is treated quite dif- 
 ferently. Gutta-percha is the sap of the gutta tree, a different si)ecies of tree 
 from that from which India rubber is i)rocured. In splicing cable the gutta- 
 percha conductor c-overing is treated as follows: 
 
 The ends of the core should be pared off after the conductor has been 
 spliced and soldered, as the exposed surfaces are apt to be affected by the 
 heat used in soldering joint in conductor. Next clean gutta-percha ends and 
 exposed conductor by wiping with a clean rag soaked in naphtha. Oently 
 warm conductor by means of llame of spirit lanqi, great care being taken 
 to not burn or injure the gutta-percha. A stick of Chatterton compound which 
 has been warmed while the above operation was in process is now rubbed 
 over the conductor and that which adheres to conductor is smootheil over 
 to a thin layer by means of a warmed iron. The spirit lamp is then used 
 to warm evenly and slowly the gutta-iiercha for about 2 inches on each 
 
 (437) 1
 
 2 Signal Corps Manual No. 3. — Chapter 1 1 . 
 
 side of the jointed coiKluotiir. When sufficiently warmed tlie two ends are 
 gradually drawn toward each other (by means of the fingers, which should 
 he slightly moistened to prevent sticking) until about one-half inch apart. By 
 the same i^rocess one end is then drawn down to a thin tilm and the other 
 drawn over so as to lap over the former. In drawing the gutta-percha the 
 conductor should be revolved backwards and forwards between the fingers to 
 insure drawing evenly. 
 
 The joint in the gutta-percha is then kneaded together with the finger and 
 thumb and smoothed down with a warm iron. The joint thus far completed is 
 then allowed to cool. After cooling it is roughened with a knife and then 
 slightly warmed with a spirit lamp preparatory to treating lightly with Chat- 
 terton compound for adhesive purposes. After treating with Chatterton com- 
 pound the joint is covered with a thin sheet of gutta-percha which has been 
 warmed. This covering is kneaded into place with finger and thumb and 
 smoothed with warm iron. Another layer of sheet gutta-percha is similarly 
 placed after first layer has been treated with Chatterton compound. The latter 
 layer should extend approximately 1 inch beyond the first layer on each end of 
 joint. In applying the sheet gutta-percha great care should be exercised to 
 work out all air between layers. The gutta-percha joint completed, it should 
 be thoroughly cooled l)y pouring cold water over it and then allowing it to stand 
 in cool air for a reasonable period of time. The joint should then be tested, and 
 if satisfactory, jute or thread servings and armor replaced, as described in 
 chapter 4 of this manual. 
 
 LAYING SUBMARINE CABLE. 
 
 In laying a long submarine cable it is ordinarily paid out over a sheave at 
 Stern of vessel, but in swift currents of coast waters the Signal Corps has found 
 it more satisfactory to pay the cable out over sheaves located in the bow. In 
 deep water where the cable will sink without danger of coming in contact with 
 the propellers it is paid out over the " bow sheaves." These sheaves are per- 
 manently located in extreme bow of vessel and are 15 inches in diameter (at 
 bottom of groove) on the cable ship Cyrus W. Field. If the water is quite 
 shallow so that cable will extend more or less horizontally, it is run from reel 
 over a sheave 20 inches in diameter, located at end of a boom, the boom being 
 at right angles to ship's length and extending over ship's side from the fore- 
 mast. With the boom and (-able on upper side of current, the ship will .swing 
 away instead of into cable and the course of ship can easily be controlled. 
 
 The advantage of paying the cable out over the "bow sheave" or sheave at 
 end of boom is that .stern of boat can always be turned in order to head in right 
 direction against any tide or current ; and while, no doubt, the cable is bent at a 
 .shorter radius than when it is paid out over stern .sheave.s, in some harbors 
 and coastal waters perfect control of cable ship is of paramount importance. 
 A cable paying out over stern has an effect similar to an anchor made fast to 
 vessel at that point, as a tight cable in this position prevents the stern of vessel 
 from .swinging freely in answer to rudder, thus i»n'venting accurate steering. 
 On the open si-a on long lines (his is not so important, as no swift currents are 
 encountered and sliarj) (urns do not have to be made. 
 
 When cable is being laid, electrical measuring insli-unients are so coiniected 
 III the ciihle IhnI sIkiuIiI a fauil develoii il could he detecled immediately. Cable 
 ship pay-out iiiiichinery is fitted with (»ne uy more suitahle friction brakes in 
 onh-r th;it lahle or grajtnel drag line will not pay out too rapidly and that strain 
 on t hem nia.\ he eont I'olled. 
 
 (4.38)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 3 
 
 When laying long suhniarine <'jil)los more elaborate apparatus is necessary, 
 because in very deep water the cable is subjected to severe strain when being 
 laid or taken up for repairs and the cable ship should be capable of storing in 
 its tanks or hold many miles of cable. The reader can form an idea of the 
 strain on cable to be encountered when consideration is given the fact that not 
 infrequently cable is located and raised in water 2..5()0 fathoms (1.^.0()0 feet) 
 deep. 
 
 In view of the fact that the Signal Corps is sometimes called upon to lay 
 short cables in shallow waters by improvised means, an account of method 
 employed in laying a cable in Laguna de Bay, near Manila, P. I., may prove 
 useful. The cable was coiled in a large casco, or lighter, the coil being oblong 
 (about 24 by 16 feet). Starting on the outside, it was coiled snugly inward to a 
 diameter of about 4 feet, the man guiding it going around in a left-handed 
 direction, the helpers squatted around keeping the coil closed in tightly together 
 as the cable came down from above. A wooden cone was erected in the center 
 to the height the pile was to reach, the edges and corners being well rounded 
 off to prevent the cable catching as it paid out. In coiling inward the cable 
 coils were carried up snugly against each other, and then the cable was carried 
 radially across the lower layer (flake, it is called) and another flake begun at 
 the outer edge. If much cable is to be put on, narrow strips of wood (called 
 feathers) are laid along the piece of cable carried straight across. Close and 
 careful coiling, especially in the lower flakes, is necessary. 
 
 Sheaves were lashed in proper places to carry the cable up. first over the 
 center of the cone and then aft. Near the stern the cable passed under a hori- 
 zontal roller, or '" fair lead," and means were provided to press a timber against 
 the cable here to pinch it and put on the necessary friction to prevent its paying 
 out too rapidly. The necessary testing apparatus was installed, and the casco 
 towed by one of the gunboats used on the lake. The end of the cable was 
 carried ashore in two small boats, one buoying it between the casco and the 
 boat nearest shore. 
 
 This can be done when distance to shore is short, but where the distance is 
 considerable it is necessary to lash two or more boats together forming a raft, 
 on which suflicient cable is coiled to reach the siiore. The raft is towed to the 
 shore by a small steam or gasoline launch, paying out the cable from the raft as 
 it is towed. 
 
 Care must be exercised to avoid kinks in the cable. This can always be 
 avoided by placing sufficient strain on the cal)le to prevent its being perpen- 
 dicular in the water. 
 
 The end ashore having been properly trenched and anchored, paying out 
 was begun. Several helpers were on the cable coils, handing the cable up as it 
 started to rise and looking out that no kinks went up. An average speed of 
 2^ miles an hour was attained, the water being not over 40 or .50 feet deep. 
 When the end was Tanded the cable was trenched about 3 feet deep, down to 
 low water. Above high, water a short cross trench was dug. a heavy log was 
 buried therein, and a chain lashed to it and the cable. This constituted a 
 " sand anchor " to prevent the end of the cable from being pulled out to sea. 
 
 The best way to electrically secure the land end of the cable is to run it into 
 the office and connect the conductor directly with the office switchboard. The 
 next best is to splice the submarine cable to lead-covered underground cable, 
 the latter going to the office. 
 
 If the cable landing is far from the office, and the cable must be coiuiected 
 with a land line, the end of the cable should go into a cable hut. This is a 
 small structure in which the cable comes up out of the trench and is secured 
 
 (439)
 
 4 Signal Corps Manual No. 3. — Chapter 1 1 . 
 
 to the lightning arrester, tlie hind line leading out from there. Great care 
 should be taken in properly securing the cable terminal either in the office or 
 cable hut. Bad insulation or poor connections are too often left there, inter- 
 fering with the work of the line or vitiating the tests. 
 
 GRAPNELS. 
 
 In locating cable in deep water an apparatus termed a "grapnel" is employed. 
 These grapnels are of various forms, but all types are equipped with arms 
 projecting from a common spindle. The grapnel, or a series of them, is made 
 fast to a strong line and dragged over the ocean bottom at right angle to 
 route of cable. About 5 fathoms of chain is made fast to end of grapnel and 
 dragged in rear of grapnel, as a means of making it follow a straight course 
 on uneven bottom. In addition a length of chain between grapnel and dragging 
 line is used to prevent chafing of line in advance of grapnel. In deep water a 
 considerable amount of dragging line is in contact with ocean bottom. 
 
 DYNAMOMETER. 
 
 In deep-sea cable work a most-important apparatus termed " dynamometer " 
 is used for measuring the strain imposed on a cable or a lii\e. While the 
 operation of the instrument is comparatively simple, experience in its use is 
 required before one becomes proficient in determining what is taking place 
 many fathoms below the cable ship. 
 
 In dragging a grapnel in connection with bringing a submarine cable to the 
 surface, the dynamometer is used to determine when the cable has been caught 
 by the grapnel. Of course, if the grapnel catches on a coral reef or ledge, the 
 effect is almost the same, but the experienced operator will readily detect 
 that the cable has not been caught. On imeven ocean bottom, where the 
 grapnel leaves a high place, taking some time to again reach bottom, the 
 dynamometer quickly transmits to the experienced operator what is taking 
 place, and more line is rapidly paid out or the ship slowed down. 
 
 If the breaking strain of cable is known, it is highly advantageous to know 
 to what strain the cable is being subjected when either the operation of laying 
 or recovering is in progress. The dynamoiuet(M' furnislies this information 
 continuously. 
 
 A few of I lie most iiniioi-lniit features of laying and recovering long sub- 
 marine cables have been entered in the foregoing, but the ground to be covered 
 in any stiuly of this subject is very wide and interesting, and justice can not 
 be rendered it in the limited si)ace available here. For further information the 
 reader is i-el'erred to "Submarine Cahle Laying and Repairing," by H. D. 
 Wilkinson, M. I. K. E., and " Sulmiaiine Telegrai)hs," by Charles Bright, 
 F. n. S. E. 
 
 SUBMARINE TELEGRAPHY. 
 
 Due to electrostatic capacity and indiictive effect of rubber-insulation cable, 
 apj)roximately 2.1 miles is the limit of length over wliicli audible conversation 
 can he ordinarily transmitted teleplKniically. This distanc(> can be greatly in- 
 creased by what is termed "loading," which means that inductance is assimi- 
 lated in the circuit at one or more points. While the latter lias been accom- 
 plished in medium length submarine cables, to dale it is inii)racl icable on ex- 
 tremely long cables such as those used for trans-.\tlanl ic connnunication. 
 
 On all cables over 1!(M) miles in length the retardation of the signals becomes sd 
 great that M(»rse ajtparatus is at a serious disadvantage; consiM|uently some 
 
 (440J
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 5 
 
 inor(» (lolicatc form of receiving,' iippiirjitus is iiocossary. That almost univer- 
 sally adopted is tlie sipJion recorder. 
 
 A description will first be jriven of tlie operation of submarine cables wbere 
 the ordinary Morse telegraph ajiparatus is employed. This des<'ription will ho 
 followed by a description of the operation of submarine cables where the more 
 sensitive siphon recorder is employed. 
 
 SWITCIIROAIinS. 
 
 If practicable the cable should be terminated at the switchboard. 
 
 A .special hlRh-insulation .switchboard for cable station.s is fiirnislied by the 
 Signal Corps and is shown diafrranmiatically in figure 11-1. 
 
 The cable conductor or line to cable hut is connected to the upper left bind- 
 ing post. A revolving copper strip is attached thereto and the bas(> is marked 
 "Instruments," "Free," or "Earth," corresponding to positions of the strip. 
 
 Fig. 11-1.— LONG SUBMARINE CABLE, SWITCHBOARD. 
 (441)
 
 6 Signal Corps Manual No. 3. ^Chapter 1 1. 
 
 This is a laseful arrangement in making tests, to conform to instructions from 
 tlie ship or distant station. 
 
 The wire to ground or to cable leading to the other station (in case this sta- 
 tion is a way office) leads to upper right-hand binding post. A disk lightning 
 arrester is connected with a binding post leading to groimd wire. Tlie other 
 binding posts are connected with ii>strument leads in the usual way, and cir- 
 cuits are pegged in as on the land-line switchboards. All openings in the 
 wooden case not occupied by wires sliould be securely pegged up. The wooden 
 case and glass cover protect the hard-rubber base against dust and moisture. 
 During tests, when insulation must be carefully guarded, a small cup of 
 chloride of calcium may be set in the closed case to absorb all moisture. 
 
 LIGHTNING ARKESTERS. 
 
 The disk, plate, point, and spiral arresters are all " jump " arresters, when 
 the lightning jumps from plates of metal or carbon, or from points or spiral 
 connected with the line to a carbon or metal plate connected with the ground 
 wire. The metal ones are liable to be fused by a flash and should always be 
 carefully examined to see if the line is accidentally grounded by them. Carbon 
 dust is liable to cause similar trouble in those made of carbon plates separated 
 by thin perforated mica. The fuse lightning arresters, in which a short piece 
 of fusible wire is in circuit with the line, arrest the flash by melting off. This, 
 of course, opens the line, and spare ones should always be ready to replace the 
 burned ones. The delicate ones mounted on mica strips with metal ends need 
 to be especially watched. When the line becomes open or is grounded, the 
 lightning arresters should at once be carefully inspected. 
 
 GROUND CONNECTIONS. . 
 
 These should be made with special care at cable stations. 
 
 Where practicable this connection should be made by securely soldering to 
 at least three or four of the armor wires of the cable a coi)per conductor. 102 
 mils diameter or larger, leading it in a neat and permanent manner to switch- 
 board. Whore plate ground connections are used, the plate should be copper, of 
 at least 5 S(iuare feet surface, with the ground wire solderetl securely to it. 
 
 OFFICE WIHIXC. 
 
 In tropiia! ciinialcs it has been found that the ordinary iiarafilnod office wire 
 is worthless for gtxtd insulation. In cable stations nothing should be used hut 
 heavily rubber-covered wire. The cable core itself is a type of the insulation 
 which the wire should have. It will pay to put up the wire with extra care, 
 using porcelain cleats and knobs; never fasten a wire with any of the ordinary 
 staples, whicli in a majority of instances will be bangiMl down on the insula- 
 tion, cutting into it and causing Iiad leaks, which are most baffiing to find. 
 
 INSTRUMENTS lOK CAIU.E WORKING. 
 
 < Ml cables up to KK) miles in length the conditions for successful working do 
 not (Icpiirt sudicienlly fi-oin those ol' land lines to i>revent the use of ordinary 
 .Morse inslrunients. The ordinjiry closed-circuit Morse^ may be used as long as 
 no incipient faidt exists. I'.ut with the current constantly on, the least faidt 
 in the insulafion is rapidly made greater by electrolytic action, and a br<>ak- 
 down soon occurs, l^'or this reason the Signal Corps uses the open-circuit 
 .system of Morse telegraph. 
 
 (442)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 7 
 
 A .«!implifie<I diapram of the open-circuit connections at a station is jriven in 
 figure 11-2. 
 
 As will he seen in diafrrani, the line oome.s to the relay, thence to ho<ly of key, 
 thence to back contact of key, and to the ground. This is the receiving posi- 
 
 LoobI Bdtfery 
 
 r 
 
 O 0^^ 
 
 ^oundeK 
 
 Cdb/e 
 
 -ff 
 
 Relay 
 
 \ y /Tey 
 
 _=_ Mziin BBffer-y 
 
 Fig. 11-2.— SUBMARINE CABLES, MORSE OPEN CIRCUIT TELEGRAPH Y, CONNECTIONS. 
 
 tion. and the current from distant stations will operate the relay. When key is 
 depres.sed, the back contact is broken and the front contact made; this will 
 cause the home battery to be in the circuit and operate the relays. 
 
 Special care must be taken not to screw key so close that both front and hack 
 contacts touch. This would short-circuit the battery and speedily ruin it. 
 
 The polarized relay has two bobbins or pairs of magnets facing each other, 
 with the armature between them. A permanent magnet supporting the bobbins 
 or in the base gives the cores of the magnets polarity opposite to that of the 
 armature, so that the current coming in one direction tends to send the relay 
 tongue to the front contact, and coming in the other to the back contact. Ad- 
 justment is made with top screw, as the relay tongue tends to be more or less 
 strongly held by the permanent magnet on the back contact, corresponding to 
 spring adjustment of the ordinary relay. The screws controlling the magnets 
 seldom need any adjustment. Care should be taken that the armature does 
 not jam against the ends of magnets. 
 
 A polarized relay is u.sed for two reasons: First, it is more sensitive and can 
 be worked on less cm-rent; second, on account of the large capacity of cables 
 as compared with land lines, the current first charges the cable when the key 
 is depressed, the cable then discharges when key is released, and a momentary 
 current rushes back through the relay. An ordinary relay would give a " kick "' 
 corresponding to this, but the polarized relay, responding to the direct current 
 only, is not affected by this momentary discharge current in the opposite direc- 
 tion, and the signals are not " chopped." 
 
 46581°— 17- 
 
 -29 
 
 (443)
 
 8 
 
 Signal Corps Manual No. 3. — Chapter I 
 
 The key has a back, middle, and front contact, as sliown. (lie battery being 
 put to line only wlien key is depressed. The battery used is some form of good 
 open-circuit battery like the Gonda, or large-sized dry batteries. 
 
 DOLTBLE-CIRRENT WOKKINll. 
 
 Wlien the cable apprei-ial)ly exceeds 1»>0 iiiilcs in lengdi it begins to work 
 lieavily on account of the appreciable length of time it takes for the cable to 
 tharge and discharge. A modification of the simple open-circuit method of 
 working, just described, must be made. This is called the double-current 
 method, and in principle consists in connecting an additional main-line battery 
 to the back contact of the key with polarity opposite to the main-line battery 
 connected to front contact. These batteries, by alternately connecting opposite 
 poles to line as the key is up or down, serve to discharge the line much more 
 
 'Sounder 
 
 BscH ConfdO^ _=_ 
 
 _ fronf Conf-acf 
 
 Fig. 11-3. 
 
 -SUBMARINE CABLES, MORSE DOUBLE CURRENT TELEGRAPHY, CONNEC- 
 TIONS. 
 
 I'aiiidiy and gi'cally increase the speed of working. A simplified diagram of tlie 
 connections is given in figure 11-3. 
 
 The simple change to make it a plain open-circuit s(>t appears when the 
 switch is thrown to A. AN'ilh the key tm tlie back coiitncl. a current flows 
 to line from the -f pole of l)ack contact battery. When key is depressed tlie — 
 pole of llie front contact battery is connected to line. The polarized relays 
 are so connected lliat they close the local circuit with tronl contact battery 
 to line. Connections fui- a three-station line for double-current working are 
 shown in figure 11^. 
 
 Without a switch t\w back contact batteries would soon be run down. As 
 oiterators are accustomed to closing the key with the ordinary circuit-closer 
 lever, a key is issued by the Signal (!orps obviating the use of a separate 
 switch. The connections are so arranged thiil llic customary movements of 
 the switch lever will make the correct connections for the double-current 
 system. (Hher combinations can be made with this key which is shown in 
 figure 11-5. 
 
 (444)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 9 
 
 fxoM Station 6 rv Statiom C. 
 
 Fig. 11-4.— SUBMARINE CABLES, MORSE DOUBLE CURRENT TELEGRAPHY, 3-STATION 
 
 CONNECTIONS. 
 
 STtCl TRUimiOW- ALL OTHtH 
 PIDTS SRAtJ 01 PnOS. CKCIUL 
 
 ALL MEJAl rouuiLO. 
 
 SIO£ ELEVATION 
 
 Fig. 11-5.— SUBMARINE CABLES, MORSE DOUBLE CURRENT TELEGRAPHY, KEY USED 
 
 BY SIGNAL CORPS. 
 (445)
 
 10 Signal Corps Manual No. 3. — Chapter 11. 
 
 SINGLE-CURKEXT OPEN-CIRCUIT REPEATER SETS. 
 [See fig. 11-G. Fig. 11-7 is a simplified diagram.] 
 
 Mountoil (Ml a small table top are the following; instnimenti=i : Two polarized 
 relays, -1.1; two soimilers, BB; two open-circuit keys, CC ; two transmitters. 
 I)D : one double switch, E. 
 
 The main line and local batteries for each of the lines, the lines themselves, 
 and the earth are connected to the binding posts marked on the table. These 
 connections, especially those of lines and earth, should be made through the 
 switchboard, lightning arresters, etc. 
 
 POLARIZED RELAYS. 
 
 These are v«m\v similar in relation of ]iarts and construction to the square 
 Western Union pattern used heretofore on the Philippine cables, with the 
 addition of a small switch F (fig. 11-6) on each, which permits the local to 
 work on either front or back stroke. If the sending comes reversed, throw 
 the switch to the other button. 
 
 AdjiLstmcnt. — The lower adjusting screws on each side should be turned 
 until the magnets are fairly close to the armature, care being taken not to 
 jam them against the armature. The relay tongue can then be caused to 
 fall over to one side or the other, as desired, by the top adjusting screw. The 
 magnetic retraction corresponding to relay spring can thus be made strong 
 t»r weak, as desired. For repeating, tlie set works better if the relay tongue has 
 a barely perceptible play. 
 
 Before substituting the repeater set for the two office sets find out from each 
 operator at distant ends of both Nos. 1 and 2 lines whether zinc or carbon 
 is connected to the front contact of his key. Suppose No. 1 says zinc. Connect 
 up several cells of battery, put wire from carbon in " earth " binding post of 
 repeater set. Connect two cells at local binding posts of No. 1. Then tapping 
 with wire from zinc on line No. 1 binding post, note if it works the relay No. 1. 
 If not, move the upper adjusting screw until relay tongue just falls over on 
 the other contact, and it should then work it. If your sending conies reversed 
 on the sounder, throw the relay switch F (fig. 11-6) onto the other contact. 
 
 Proceed in the same way with No. 2, being- sure to tap on line No. 2 binding 
 post with the wire coming from same pole of ycmr experimental battery, as 
 reported by distant end of No. 2 as going to line through front contact of key. 
 
 Now, having placed the table in position and run the wires from switchboard, 
 batt:eries, etc., to the proper binding posts, place the switch at " cut " and 
 try to work on, say, No. 1. If you do not succeed, reverse the wires leading 
 lo main battery No. 1 binding posts, and this will probably send the current 
 in the right direction to work both your own and the distant relay. 
 
 Proceed in the siime way with No. 2 before attempting to uune the main 
 switcli to the " repeat " position. 
 
 SOUNDERS. 
 
 These sliouM bo adjusted with as little play in the lever as is consistent with 
 sullicicnt loudness. 
 
 (446)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 
 
 11 
 
 5? 
 
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 rr, 
 
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 <\J 
 
 ^ 
 
 
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 Qq! 
 
 lO-v^^ 
 
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 <447)
 
 12 
 
 Signal Corps Manual No. 3. — Chapter 11, 
 
 wto A Line 
 
 Msat ffepeajii <j 
 
 Weet Mam -=■ 
 Dattsry -^ 
 
 As shown battery at terminus of East line is connected to line. This closes AVest polar relay 
 which connects " West main battery" in circuit with West line. 
 
 Fig. 11-7.— SUBMARINE CABLES, MORSE TELEGRAPHY, SINGLE CURRENT OPEN 
 CIRCUIT REPEATER SETS, SIMPLIFIED DIAGRAM OF CONNECTIONS, 
 
 TR.VN.SMITTEUS. 
 
 Earli of tlipsp lias a front and liaok contact, like the keys; in fact, it is an 
 open-circuit key worked by its electro-magnet in the local circuit with the 
 sounder. For s<>f>(l repeating, the lever should have barely a perceptible play. 
 Be careful that the armature does not strike the masnet ; this would prevent 
 the " front contact " from being made at the contact points nearest the magnets. 
 
 Having made the various adjustments, throw the double switch from " cut "" 
 to " repeat." The two lines should then work into each other. 
 
 Note that when distant station or key of repeater set is working, say, on line 
 No. 1, only that side of repeater .set should be working, and similarly for No. 2. 
 
 If operators at distant ends conii)lain that signals are imperfect, note if 
 repeater, relay, and transmitter levers are set to work extremely close, or if 
 the adjustment is not too strong on the relays. Al.so if the si)rings in the trans- 
 mitters jirc iKil loo strong. 
 
 Senders on lines tied logcthcr iiy rciiciiters should be cautioned (bat light, 
 jfi-ky sending is paiiicularly iiard to gel tlu-ougb reiu'aters well. 
 
 DKSCIUI'TIOX OK OI'KK.\TIO\ OK OI'KX-CllU'nT .SI NMiK-crUUKXl" UKl'E.VTlNd SET. 
 
 I Sec liK. 11 -(•..] 
 
 First, supiHise distant station on line No. 1 is working, the double switch 
 set to "rejiciil." The current comes in line No. 1 biinliiig posl, thence to \\ and 
 4 to right bar (tf switch, through contact H to 7 and S on left transmitter. 
 Ihrougb lever of Iransmitler to back contact VI and 18. through 14 to rel;iy 
 at l."t. tinuiigii reliiv cdils operating (be r(4ay tongue, (hen out at 1(5 through 
 17 on key. tlirougb budy ul' key (<» l.S. 1!», ;iiid lid lo earth, 'riie local circuit 
 being closed at rel.-iy, tlie lociil biittery sends in a current tlirougb binding 
 posl.s lociil .No, 1. Ilu'iice lo magnet of t r.-msMiitlei' through 10, out at 11, tin-ougb 
 
 (44S)
 
 I 
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 13 
 
 SdUiHlcr at 42 and 43, tliroiisli relay local imiiils at 44 and 4.", thonr-o l)ack to 
 Icical No. 1 battery. When the local current passes throufih transmitter magnet 
 it closes the front contact. This permits the current of main-line battery No. 2, 
 starting,' at i)in(linj^ post, cominj; to transmitter on 40, to front contact 30 and 38 
 tln-oufih lever of transmitter to 20, then to 2;"). to switch contact 23, throujrh 24 
 to left bar of .switch, to 22, 21, and to line No. 2 binding,' i)ost, ont to line, 
 working the instruments in that line. An exactly similar thinj; happens when 
 an operator in line No. 2 sends a current tlirough his side of the repeater set. 
 
 When the repeater station works his key on the No. 1 side, a current comes 
 from No. 1 main-line battery left binding post to the front contact of his key 
 throuKli 47. thence through key lever to body of key, then to relay No. 1 through 
 17. through relay and out to line No. 1 through 16, 15, 14, 13, 12, 8, 7, G, 5, 4, 3, 
 to " line No. 1 " binding post, and out to line. 
 
 Relay No. 1 works its local circuit, causing the transmitter to repeat into line 
 No. 2, as before explained. 
 
 When switch is turned to " cut," each key, relay, and the transmitter and 
 sounder in local circuits work independently as two ordinary open-circuit sets. 
 
 Two small resistance coils under the binird are arranged t(t shunt the sounder 
 and tiansuutter magnets of each set. This prevents sparking and sticking at 
 the local relay points. 
 
 Notes on Efficient JIorse Wobkixg of Si'bmarixe Cables. 
 
 The battery power used in working Morse over a submarine cable should 
 be as low as possible, for the protection of the cable itself, as w-ell as for the 
 reduction of the retardation effect of the static capacity of the cable. 
 
 The batteries at each station shoiUd be inspected frequently and care taken 
 that there is no corrosion at their connections and no creeping of salts and 
 that every connection is good and tight. If possible they should frequently be 
 tested for voltage. 
 
 RELAYS. 
 
 Whatever may be the type of relay in use, great care should bo taken 
 in making the adjustment that there shall be no stitfness at the pivots or 
 trouble from dirty contacts. Trouble frequently occurs through rust or cor- 
 rosion at the pivots which makes the sensitiveness of the relay very irregular, 
 requiring more current to operate it at times than the normal amount. 
 
 In general, polarized relays are more sensitive than the ordinary 150-ohm 
 relay and should be used wherever possible. In these relays the magnets are 
 drawn back by screws attached to each pair. The sensitlvenesss of the relay 
 of this type is increased by drawing back the magnets, but at the same time 
 the strength of the action of the armature is made more feeble. The adjusting 
 screws on top should be so arranged that the armature tt)ngue naturally falls 
 slightly to back contact, the arriving signal pulling it to front contact. In the 
 polarized relay it should be remembered that magnetic action is substituted 
 for the .spring, and consequently the amcmnt of bias, as it is called, is i-egu- 
 lated by the adjustment of the top adjusting screw. 
 
 In general, when the two lower screws controlling the magnets are once 
 set to regulate the required amount of .sensitiveness they should seldom be 
 changed, the ordinary adjustment for changes in line conditions being made 
 entirely with the top screw. 
 
 (449)
 
 14 
 
 Signal Corps Manual No. 3. — Chapter 11. 
 
 When the line is worljed through condensers at the receiving end (fig. 
 11-8) the top screw is then so regulated that the armature tends to fall 
 either way indifferently, the motion of the tongue to-and-fro being determined 
 by the positive and negative discharges from condensers produced by the 
 action of the distant key. 
 
 The object of placing a condenser in the receiving circuit in this latter method 
 of working is to cut off the action of earth currents, whicli in the ordinary open- 
 circuit system in some cases make constant changes necessary in the adjust- 
 ment of the relays. The sliunt placed around the condenser sliould be adjusted 
 as near infinity as is consistent with firm signals, to prevent troubles from 
 earth currents mentioned above. Except at infinity, the use of the shunt per- 
 mits of giving more or less bias to the relay tongue. 
 
 HADLEY 
 
 WRANGEIL 
 
 Wrongel-Hadley Coble 
 
 6OOohmi-30mf. 
 
 
 fblahzai Rela/ 
 Coble Set 
 
 Fig. 11-8.— SUBMARINE CABLES, POLARIZED RELAY SET, CONNECTIONS. 
 
 The magnets of the receiving relay, if of the ordinary 1.50-ohm type, should 
 be adjusted well up, close to the armature, without actually touching it, and 
 the battery gradually reduced until there is no sticking of the signals noticed, 
 with no battery on the line. The spring should be " turned down " completely 
 until the armature falls forward against the front contact, and then again 
 "turned up" until the armature falls against the back contact, and then again 
 " turned up " the least bit more to allow a margin for adjustmeiit. If a relay 
 of the Frier self-polarizing tyi)e is used, the attracting magnet should be kept 
 close to the armature, and the other magnet adjusted to get the best effect. 
 
 In an o])en-cir(uit Morse system on cables when it becomes necessary to pull 
 the magnets of the relay away from the armature, it shows that more battery 
 is being used tlcin is reciuired. This battery, therefore, should be inunediately 
 cut down iinil ihe magnets adjusted close to the armature, as above mentioned. 
 
 I'UOrEIt TOt'CII TO KEV. 
 
 Morse working (Ui cables re(|uires a different touch froTU that needed on siiort 
 land lines. Many o)»erators broiight n|» to work on short land lines are inclined 
 to use a nervous, light, and jerky style. This when ai)plied to cable worldng 
 causes nnich trouble. The dots come very weak or fail altogether, while the 
 dashes stick, making it extremely difficult to adjhst. At times it would seem 
 as if the line or battery were giving ti'ouble, while in reality the fault is in the 
 sending. 
 
 (450)
 
 r 
 r 
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 15 
 
 Ttie cable operator needs a swinging, .solid style, with not a very great differ- 
 ence between the dots and dashes, but with a uniform contact. With such style 
 no (llfTiculty will be experienceil in keeping the relay adjusted. The greater 
 static capacity of a cable the greater the otTect of irreguhirities in sending. 
 
 The time of charge of a cal>le should always be taken into cousidei-ation, and 
 the sending regulated accordingly. 
 
 ItEPEATEK.S. 
 
 Wherever possible repeaters sliould be inserted between a land line and a 
 cable instead of working directly through, as the battery is increased on land 
 lines from time to time through various cau.ses, such as weather conditions, bad 
 joints, and connections, etc. By the insertion of repeaters the amount of 
 battery going into the cable is always the same, and the adjustments of the 
 instruments on the cable side will vary but little, if any. The operator at the 
 repeater station should keep his instruments well adjusted to the conditions of 
 the line, making the relay work the repeater heavy or light according to the 
 requirements. Very often the signals seem clear to him, but do not reach the 
 other station properly. The trouble will probably be due to (iii-ty contacts in 
 the repeater. Dust accumulating at the contact points of the sending key, or 
 at the contact points of the reijeater. is a common cause of high resistance in a 
 circuit. These points should always be cleaned with crocus cloth, or if very 
 dirty or corroded with a very fine tile. 
 
 GENERAL NOTES. 
 
 If a jar, or rattle, is noticed on the receiving relay it will generally be caused 
 by a loo.se connection somewhere, unless there is a land line in circuit that is 
 swinging against something. 
 
 Bef<ire increasing the amount of battery on any cable, the chief operators at 
 each end should consult and try to get at the exact cause of the trouble and 
 report immediately to the officer in charge. The minimum number of cells of 
 main-line battery which will operate a cable efficiently will be determined. 
 After the numbcn- is determined, all operators are forl)idden to increase the 
 number of cells except by authority of the chief operator, who will report the 
 matter to the officer in charge, so that innnediate steps may be taken to remove 
 the cause of the trouble. 
 
 A good operator will always know by the "feel" of his relay the condition 
 of the circuit. If the circuit is grounded between stations his home relay will 
 work stronger than usual ; the nearer the ground is to his end the stronger the 
 relay will work. If the line is open at the distant end, and an ordinary relay 
 is used, he will get two inductive kicks from the " static " of the cable, one on 
 closing the key and one on opening it. These kicks will be lighter the nearer 
 the disconnection is to his station, as there will be less " static." If he gets 
 no kick the disconnection nuist be near home. With a polarized relay he 
 will get the click on his relay only when closing his circuit. It should be the 
 duty of every operator to get familiar with this " feeling " of his line by 
 getting the operator at the other end to free the line for a few minutes and 
 then ground it direct without the distant relay being in circuit for a few 
 minutes ; he can then put his home relay at a certain adjustment, which he can 
 use for these tests, and note the effect with the distant end open and distant 
 end grounded without the distant relay being in circuit and also with the dis- 
 tant relay in circuit, as it is normally. 
 
 (451)
 
 16 Signal Corps Manual No. 3. — Chapter 11. 
 
 Whenever a lightning arrester is used, it should be frequently examined for 
 a " gi'ound " or loose connection. A piece of paper moved back and forth 
 between the ground plate and the line connection will generally remove any 
 dust or foreign substances which may have accumulated there. 
 
 In a plug switchboartl care should be taken that the plugs are clean and fit 
 snugly in the holes. The holes should be cleaned out frecpiently, as in certain 
 climates insects find it convenient to nest thei'ein. Sometimes the holes and 
 plugs become corroded or worn irregularly, with the result that the circuit 
 becomes partially oi* totally disconnected. If a trouble like this occurs it 
 would be well to bridge across with a small piece of wire the connections made 
 by the plugs. 
 
 In moving offices from one building to another in isolated places the wiring 
 is often crude and in time causes trouble, and new men make changes from 
 time to time to meet the emergencies that may arise. The operator in charge 
 should make a diagram of the office connections, .showing the location of each 
 wire and post it in a prominent place in the oflice and, when relieved, explain 
 it all in detail to his successor. 
 
 The electrical engineer or a thoroughly competent man should visit all 
 stations from time to time and remedy any deficiencies in the conditions. 
 Instruments should be overhauled and properly adjusted, and batteries and 
 wiring gone over thoroughly. 
 
 OPERATION OF LONG SUBMARINE CABLES. 
 
 As previously stated in this chapter, Morse apparatus is at a serious dis- 
 advantage on cables over approximately 200 miles in length, due to retardation 
 of signals occasioned l)y large electrostatic capacity of such cables, and the 
 siphon recorder, a more delicate form of receiving apparatus, is almost mii- 
 versally used in such instances. 
 
 What has been stated relative to wiring at cable stations where Morse 
 apparatus is used applies also to stations where tlie siphon recorder is in- 
 stalled, and great care should be tiikeii to obtain a high insulation of all 
 wiring and between all app:ii-atus and ciuiii. 
 
 SIPHON KICCOKUEKS. 
 
 The siphon recorder may be brielly described as a moving coil galvanometer, 
 with a delicate glass siphon attached to the coil in such a way that the mo- 
 tions of the coil are ti'ansmitted, very nuich magnified, to the point of the 
 siphon. One end of this si])lion dips into a small ink well, the other end, 
 where the motion is greatest, touching the moving paper tai)e. This tape is 
 kept moving steadily by means of a small electric, .spring, or weight-driven 
 motor. Every motion of the coil is i-ecorded as a deviation in the straight 
 line being drawn on the tape, :ind signals produced by sending quick impulst's 
 from either the posilive or negative side of the battery will be recorded as 
 short waves above or lidow I his straight line. To render the siphon more 
 sensitive by reducing its friction agiiinsi llic tape, it is kept in constant and 
 rajiid vibration by electromagnetic means. 
 
 The construction of the recorder is shown in (igures 11-f> and 11-11. 
 
 Figure 11-10 shows a simplilied diagram of I lie coiniections. 
 
 Figure 11-J» is the large sii)lion recorder used generally oii (lie long cables. 
 In the held of the |>ermanenl magnet I! the Hat rectangular coil .1 of line 
 insidiited wire is susjieiided by tine threads above and below. Fine wires 
 eonnecl llie recoi'dei- cdil with llie cable circuil. 
 
 (4.M')
 
 Lcr.g Submarine Cables, Telegraphy, and Tests. — Chapter I 1 
 
 17 
 
 AMicri riirrctii iiii|iiilscs ;in-i\c, tlicy (Icllccl tlic cnil. (lie (lirt'clioii (l('[icinlin« 
 iiIiDii llit> poliirit.v <>r tlic rccciviiiji iiiiinilsc. 'I'licsc motions iirc yononilly very 
 small. Tlu' coil i.s aKMclicil l)y two line sill< tin-eads to a sinjill piece of alunii- 
 nnni. to which is attached I lie ;,'lass .sii)hon ('. The aluminum piece Is itself 
 susiiended liy a tine lioiizoiiial wire. The .silk threads from the coil being 
 near the point of suspension of tlie siplion, every motion of the coil and 
 tln-eads is thus maj^nitied at the lower end of the siphon. The .siphon dips 
 at the upper end into the ink well I) a;id at its lower end lijjhtly touches the 
 niovinj,' tape /•>'. This tape is moved forward steadily by the gear wheels ./, 
 which are driv(>n l»y a shaft extending hack and carrying a indley which 
 is driven by the nictni- // through a tiexiltle bell. 
 
 F.g. 11-9.— LONG SUBIVIARINE CABLES, LARGE SIPHON RECORDER. 
 
 (453)
 
 18 
 
 Signal Corps Manual No. 3. — Chapter 11. 
 
 To eliminate friction of tlie siphon on the paper tape, the siphon is kept in 
 vibration hy means of a small electromagnet /•'. to the armature of which is 
 attached the horizontal wire carrying the piece of aluminum and the siphon. 
 Through the electromagnet F rapid pulsations are sent from the interrupter G, 
 which is similar to a small vibrating bell mechanism. 
 
 V.liat.r Cor.httt.onS 
 
 THE APPARATUS MAY BE IDENTIFIED 
 BY MEANS OF LETTERS HEREON AND 
 REFERENCE TO FiG^ ll-9. 
 
 Fig. 11-10.— LONG SUBMARINE CABLES, LARGE SIPHON RECORDER, CONNECTIONS. 
 
 The interrupter and vibrator are controlled l)y a small rheostat L being 
 included in their circuit. The speed of the motor is regulated by a rheostat A". 
 On the other side of the recorder is an adjustable shunt coil which regulates 
 the proportion of current through the coil .1, coming from the cable. 
 
 The small recorder (tig. 11-11) is u.sed on the shorter cables. It is only about 
 one-fourth as sensitive as the large one .lust described. In its essential parts it 
 is very similar to the lai"ge <tne. tin* si])hon suspension lu'ing somewhat simjtler 
 and more compactly arranged. 
 
 Tbe permanent magnets of both these recorders have coils wound around 
 them foi' the ])\n'i»ose of strengthening their magnetism, in case it is weakened, 
 by sending a imnncnlary direct ciu'reiit d'om some KHI-volt source through 
 tliciii. <'ar<' iiiusi lie I liken llial llie current is direct (not. jdternating) and 
 that il is sciil in llic proper direclion. 
 
 Tlie (iilhiw ing, iin adjusi nieiil of I he recorder, the vibra(<u', and motor, is 
 (li-iiwii ill pari li-Mui I'.eginners' iMainiai of Submarim> (^able Testing and 
 \\ Diking, by <!. M. I'.aines: 
 
 (454)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 19 
 
 Fig. 11-11.— LONG SUBMARINE CABLES, SMALL SIPHON RECORDER. 
 
 AliJCSTMENT OF RECORDEK. 
 
 The present form of recorder, known as the " Hylirid," is of the permanent 
 magnet type. As it has heen found, however, that the magnets lo.se a propor- 
 tion of their strength in tropical climates, a winding of insulated copper wire, 
 with a resistance of about 8 ohms, has been provided for them. This arrange- 
 ment, whence the instrument derives its name, permits of the restoration of 
 the magnetic field strength when it falls below its normal value. 
 
 On the supposition, then, that the magnetometer proves the magnetic field to 
 have fallen below 10 Cuff units, a current from an E. M. F. of 100 volts should 
 he applied to the aforementioned coils. For this purpose the ends of the coils 
 have been conveniently brought to terminals on the instrument which are 
 marked, respectively, with the positive and negative signs. 
 
 The operation of strengthening the magnetic field is carried out in the fol- 
 lowing manner : 
 
 The positive pole of the battery — iireferably secondary cells or dynamo, 
 l)ecause for the desired effect a large momentary current is required, therefore 
 the internal resistance nuist be inconsideraijle — is connected to the terminal 
 marked +. To the other terminal should be joined a short, thick wire. The 
 current is applied by three or four momentary contacts between this wire 
 and the negative pole of the battery or dynamo, due care being observed that 
 tile operator does not include himself in the circuit. 
 
 The " Hybrid " may also be used as an electromagnet recorder by maintaining 
 a battery on the magnet coils. It is intended, however, that it should be em- 
 ployed as a permanent magnet instrument, its field strength being kept at its 
 normal value in the manner indicated. 
 
 (455)
 
 20 Signal Corps Manual No. 3.— Chapter 1 1, 
 
 The double liber between the signnlinj; et)il ami the siphon cradle is an im- 
 provement upon the old single-tiber attachment. By this new arrangement the 
 full movement of the coil is imparted to the siphon. 
 
 The renewal of the double tiber, when necessary, is effected in the following 
 manner : 
 
 1. Set the coil square and tix it. 
 
 2. Place the bridge piece in its central position. 
 
 3. Turn the milled head at the right-hand extremity of the bridge until the 
 siphon cradle hangs perpendicularly. 
 
 4. Attach one end of the fiber to the right side of the top of the coil ; fix it 
 with the shellac supplied for the purpose ; pass it round, or through, the siphon 
 cradle; fix it there and lead it back to the top of the left side of the coil, 
 where it will also be secured. 
 
 Great importance is attached to the preservation of the following equidis- 
 tances : 
 
 1. Between the attachment of the fiber ends and the coil center. 
 
 2. The two points where the fiber passes through the siphon cradle and the 
 cradle wire. 
 
 To obtain the most suitable adjustment of the fibers, fir.st slacken them and 
 set the siphon in an upright position by turning the milled head which holds the 
 cradle wire. Next, tighten the coil fillers, and if the siphon be defiected from 
 the perpendicular bring it back by a slight turn of the nulled head carrying the 
 coil suspension. This will square the coil and bring back the siphon to the per- 
 pendicular at the same time. 
 
 If. on again tightening the coil fil)ers, the siphon deviates, it will be found 
 that the aforementioned equidistances have not been preserved. 
 
 A broken coil suspension admits of easy repair. 
 
 Thread a piece of silk through the aluminum attachment at the top of the 
 coil, tie the ends in a loop, and pass them up through the coil cap over the small 
 pulley above it. 
 
 A proper adjustment of the signal c(»il is a matter of utmost importance for 
 securing the double result of maximum signal speefl and definition. Experiment 
 has demonstrated that for rapid speeds better defined signals are obtained by 
 discarding the shunt and tightening the coil suspension. By this means a 
 quicker periodic movement is given to the coil. The shunt exercises a damping 
 ('ffect on the coil, rounding the signals in such a manner as to render them 
 unreadable at high .speeds. 
 
 This ju'i-iodic movement of the C(til would also re(iuire attention if. lor in- 
 stance, it were (ouiid neces.sary to change over an electrically long cable to an 
 instrument adjusted for a short one, or vice versa. Vov the long cable, with 
 a slower signaling speed, a larger periodic movement of the coil would be 
 r('(|uire(I to give a sufhcient ami)litn(I(' lo I lie signals. 
 
 With r<'gard lo Hie adjusliiicnt ot the vibrator, the screw and weight on the 
 interrupter (1, figure 11-12, is the most important factor, and should claim tirst 
 attention if a failure of ink occur. For the vibration of a long, fine siphon the 
 weight will need a higher position on the make-and-break j-od than would b(> 
 required for a coarse tube. The movement of the vibrator armature should b«' 
 so regidated as to be nearly invisible. Variation in the thickness of the ink fiow 
 may often be obtained by altering the rheostat resistance L. 
 
 (4r.(i)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 21 
 
 MUIUUEAD'.S VlBKATOIl. 
 
 Figure 11-12 explains the connections of tliis apparatus. A battery of from 
 3 to 5 volts, with low inti'rnal resistance, is rciiiiiriMl to jtroperly operate it. 
 Four Edison primary cells, tyjie V or their ('([uivalent. will suflice. Uesistanct; 
 L permits the retrulation of the current as desired. The action and use of the 
 instrument are too weU known to need a lenythy descriiition. It will he found 
 
 mmom 
 
 '^ -^ 
 
 Fig. 11-12.— LONG SUBMARINE CABLES, SIPHON RECORDER, MUIRHEAD VIBRATOR. 
 
 CIRCUITS. 
 
 that the best result is obtained when the interrupter (1 works almost silently. 
 Fine siphons are also recommended as bein^ susceptible of greater vibration 
 than coarse ones, with a consequent reduction of friction between the siphon 
 point and the paper. The spark coil connected between the make-and-break 
 contacts is indicated as J/ in the plan below. The resistances of the interrupter 
 G and vibrator F coils are about 10 ohms per pair. 
 
 THE MOTOR. 
 
 The present form of recorder motor is a development of the orig:inal type intro- 
 duced by Lord Kelvin. A cam is suitably adjusted to allow the current from the 
 driving battery to pass at the proper points, in sequence, through the coils of 
 the fixed electromagnet below the revolving drum. A set of resistances K, figure 
 11-9, on the motor base can be introduced into the circuit of the battery and the 
 electromagnet coils for the regulation of the speed. 
 
 (457)
 
 9-2 
 
 Signal Corps Mcinual No. 3. — Chapter 11. 
 
 Soft-iron bars, disposed :u equal distances from each otlier, are fixed longi- 
 tudinally on the surface of the rotating brass cylinder, through the center of 
 which passes the axle upon which the whole revolves. 
 
 At the instant a bar. attracted by the electromagnet, arrives opposite the core 
 of the latter the battery is cut off by the cam. The momentum carries the bar 
 past and brings the next near the core of the electromagnet. The cam again 
 closes the current, giving another impulse to the drum, and so on. The result 
 of this series of operations is a continuous revolution of the drum. 
 
 For operating the recorder motor a battery of from 6 to 12 volts with low in- 
 ternal resistance and a large ampere-hour output is required. Six to twelve Edi- 
 son primary type V cells or their equivalent will prove satisfactory. 
 
 OrER.iTION OF MOTOR BY ELECTRIC-LIGHT CURRENT. 
 
 Where the office is provided with electric lights fed by direct current from 
 110-volt circuits the table-lamp circuit can be utilized in place of a battery, as 
 shown in figure 11-13 for operating the motor. 
 
 Fig. 11-13.— LONG SUBMARINE CABLES, SIPHON RECORDER. TO OPERATE MOTOR 
 FROM ELECTRIC LIGHTING CIRCUIT. • 
 
 The 8-ohm resistance coil, made up of sufficiently large wire not to heat witli 
 ] ampere, is in circuit with the 32-candlepower table lamp. This coil is shunted 
 by wires from the motor, as shown. An E. M. F. of approximately 8 is obtained 
 at the motor terminals by this arrangement. 
 
 -120 vol Is-* 
 
 2-32 0.P Lamp3^C\ i\ 
 65ohm 5W V 
 
 E^l ectric Ughf-hsads 
 
 Marble slab, 
 /6"x^"x. 7" 
 
 Nol7 Oerrnan 
 silver vans 
 
 ^*~fusGs:^Amp. 
 
 Fig. 11-14.- 
 
 -LONG SUBMARINE CABLES, CURRENT SUPPLY AT SEATTLE TERMINUS 
 OF SEATTLE-SITKA CABLE. 
 
 (458)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 23 
 
 Figure 11-14 .shows another method. The latter is now being used in the 
 Signal Corps cable othoe at Seattle, and res^ults are entirely satisfactory. The 
 coil may be extended to supply additional instruments, such as cable trans- 
 mitters, with current. 
 
 The motor and vibrator should not be driven by the same battery on account 
 of the constant variation in the potential of the latter. Say the motor battery 
 has an.E. M. F. of 4 volts and an internal resistance of 1 ohm. The motor coils 
 have, also, a resistance of about 1 ohm each. The potential, therefore, outside 
 the battery constantly varies, by the make-and-hreak, between '2 and 4 volts. 
 This variation would disturb the regularity of the vibrations. 
 
 fAUK OF RECORDER SIPHONS, INK, ETC. 
 
 Recorder fiipJtons. — The punk furnished with tool boxes makes the best mate- 
 rial ft)r bending siphons. A lighted paper spill made of recorder tape is also 
 a handy means of bending siphon tulies. A small spirit lamp is berter. Tilt 
 the lamp forward ; the tubes must not be thrust into flame ; a slight contact with 
 the blue flame underneath will bend the tubes without melting and closing the 
 tube. By using a spirit lamp both hands are available. 
 
 The best way of breaking off the surplus tube is by pressing it betSveen the 
 thumb nail and the forefinger. This usually leaves a clean, level break, requir- 
 ing a very little grinding. A medium fine carborundum stone or a fine emery 
 sti^^'k may be used to smooth the siphon point. Another method is by means of 
 the miniature battery motor fitted with a small emery wheel. 
 
 Recorder ink is made by dissolving some of the more soluble aniline dyes in 
 water, to which is added alcohol. In general, about one-fifth alcohol is correct, 
 but the amount of alcohol depends upon the quality of the tape and dryness of 
 the air. " Soluble-blue " aniline is good, and some of the " Diamond dyes " 
 make good ink. It is best to use boiled water. After the aniline is thoroughly 
 dissolved the ink should be run through a filtering paper. The bottle should be 
 kept corked and care taken to exclude dust and lint from the ink well. 
 
 If siphon gets choked, heat the was soldering strip used for putting siphons 
 on and gently rub along siphon. This will force the ink out and remove the 
 obstruction. 
 
 \\hen recorders are not in \ise for some time the siphons should be inunersed 
 in water instead of ink. Empty ink well, fill with water, letting paper tape run 
 till all ink is drawn out. Bettor still is the use of alcohol instead of water. 
 When ink is drawn out of siphons, the alcohol filling tube, the alcohol can be 
 returned to bottle and siphon left dry. On starting recorder again the ink will 
 flow freely without assistance; the alcohol having evaporated leaves tube dry. 
 
 Ground connections. — In no case should the recorders be connected with the 
 same ground as land lines or even to the same cable sheath that connect to 
 instnnnents where Morse is used. Owing to the great delicacy of the recorder, 
 this will cause the Morse working to disturb the recorder signals. (See remark.s 
 pertaining to ground connections appearing later in this chapter.) 
 
 AUXILIARY APPARATUS FOR SIPHOX RECORDER WORKING. 
 
 Double keys are used similar to, those shown in figure 11-15. The battery 
 binding posts are on the sides, while the earth and line posts are at the back. 
 Connections and switch used are shown in figure 11-15. 
 
 The signaling condensers may be either in the transmitting circuit, in the re- 
 ceiving circuit, or both. In the Alaskan cable offices the condenser is inserted 
 
 46581°— 17 30 (459)
 
 24 
 
 Signal Corps Manual No. 3. — Chapter 1 1 
 
 in the receiving circuit only as sliown in figures 11-15, 11-16. and 11-17. These 
 condensers should be very solidly made and having ample thickness of dielectric 
 to prevent short-circuiting by puncturing or rough handling. 
 
 Hlljlllllllllllllp 
 
 Battery 
 
 Fig. 11-15.— LONG SUBMARINE CABLES, SIPHON RECORDER SET, SIMPLIFIED CON- 
 NECTIONS. 
 
 At the offices on the longer cables is provided a large coil forming an induc- 
 tance shunt to the cable. (Figs. 11-16 and 11-17.) This coil has resistance in 
 series with it mounted in the same case with the condenser shunt. 
 
 The battery required to operate long cables with siphon recorder is small 
 when compared with the operation of land lines. For example, the Seattle- 
 Sitka cable, 1,085 miles, is operated with 10 ordinary dry cells; the A'aldez- 
 Sitka cable, approximately 600 miles, with 2 dry cells; the Juneau-Sitka cable, 
 approximately 300 miles, with 1 dry cell. During extreme low insulation the 
 Seattle-Sitka cable has been operated when less tlinn one-tenfli of one mili- 
 arapere came through from the di.stant end. The trallic on tii(> Seattie-Sitka 
 cable is practically continuous for 15 or more hours each day, and it has been 
 found that dry cells are entirely satisfactory. The dry cells for this service lasi 
 from six to eight months. The condition of these cells should be frequently 
 ascertained. 
 
 .\RR.\.N(iKMENT OK IXSTRUMKNTS lOK OI'KK.VTINC r.ONC CAHLES. 
 
 .\s siphon recorders iire now alniosl niiiv<>rsally usimI on long cables, office 
 .sols of this kiiwl only will he (Icscrihed. Th(» siini>l(^st arrangement of the 
 siphon recorder set is shown in tignrc 11-15. With the switch in sending ])osi- 
 tion it is seen that the negative end of battery is ])ul to line wIkmi the left Icey 
 lever (dot) is depressed, and the positive when the i-iglit (dash) is depressed. 
 
 IGO)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 1 I . 
 
 25 
 
 I 
 
 Witli swifcli set ;it rcceiviii};. the iiu-oiiiiiif; currents pass tliroufih condenser 
 and ret-order to earth. < >n the longer cables Muirhead's arrangement of the 
 circuit is shown in figure 31-16. 
 
 Cable 
 
 / 
 
 Switch 
 Senoing ^ ^Receivimj 
 
 M-ey 
 
 H Q 
 
 'h|i|i|i|i|i|i|i|i|--' 
 
 Battery 
 
 I 
 
 Condenser 
 
 Seconder 
 
 Fig. 11-16.— LONG SUBMARINE CABLES, SIPHON RECORDER, MUIRHEAD'S ARRANGE- 
 MENT OF CIRCUIT. 
 
 SWITCH 
 
 To lef-t-Sendinq po^hon 
 To right- Rxei ving « 
 
 Fig. 11-17. 
 
 -LONG SUBMARINE CABLES, ACTUAL CONNECTIONS AT ALASKAN CABLE 
 OFFICES. 
 
 In the receiving circuit the inconiing currents are first partly shunteil to 
 earth through the adjustable resistance and inductive resistance coil. This, 
 while reducing the signals somewhat in amplitude, tends to make them squarer 
 and more sharply defined. The unshunted portion of currents then pass on, 
 part of them going directly to recorder and earth through the condenser shunt 
 
 (461)
 
 26 
 
 Signal Corps Manual No. 3. — Chapter II. 
 
 adjustable resistance, and the other through the condenser and recorder. By 
 adjusting the resistances and condenser the signals can be leveled off to the 
 most legible shape. 
 
 The actual circuit arrangement just described is shown in figure 11-17. 
 
 The inductance coil shown in diagrams is not used on short cables lilje 
 Valdez-Seward-Cordova cables, about 264 statute miles. 
 
 Figure 11-18 is a diagram of circuits of a duplex and simplex system. 
 
 gmsm rfT^V I'ailt ^.'P^ 
 
 AMERICAN TELG. MAVER,ie99 EOlTION.r 277 
 
 Fig. 11-18.— LONG SUBMARINE CABLES, SIPHON RECORDER, DUPLEX AND SIMPLEX 
 
 SYSTEMS, CONNECTIONS. 
 
 AUTOMATIC TKANSMITTEKS. 
 
 WIkm'c Mie traflic is lic^avy enougli lo warrani tlic expense of installation the 
 auloinatic transmitter sliouhl be u.sed. The maximum signaling speed of the 
 caliie may thus be maintained; the signals are uniform, and, in the words 
 of a superintendent of a conmiercial cable company, "it does not stop to talk." 
 'I'lic Cuttriss aut<»matic transmitter, hereafter described, lias proved very sat- 
 isfactory on th<> Seatt]e-Sitl<a cal)le. 
 
 The apparatus uses a iierl'orated tape automatically f<'(l througli liic instru- 
 ment liy means of a smalPeh'ctric motor. The perforations are previously 
 made on a machine similar to a typewriter and by means of them the dot- 
 and-dash cliaracHTs arc li-anslVrrcd electrically to the caljle conductor. 
 
 TMK (TTTRISS ATTOMATK' TRANSMITTKU. 
 
 'i'lic uii-jiig of the Cuttriss automatic transmitter, figure 11-10, illustrates 
 I lie method of operation of the instrumcMit. It is the i)i'actice to connect, as 
 auxiliary, transmitters of the ordinary telegraph type with the Cuttriss trans- 
 mitter. The drive of tlie Cuttriss transmitter is a motor with permanent 
 field magnets. The speed is governed by a make-and-break contact, which is 
 adjusted by a knurled screw jtrotruding through the end of the instrument 
 case. The more continuous the " make," or, in other words, the closer the 
 adjustment of governor contacts, the faster should be the speed. Each revo- 
 
 (4GJ)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 27 
 
 lutlon of the armature .shaft of motor turns the star wheel one-tentli of an 
 iiu-ti. The outside star wlieel contains two sols of lioles iiitn which the pins 
 of liic piclxers fall when oi»posite the holes in Hit- ta|ic. The outside holes 
 control the "dash" inipui.ses. Inside the case is a master contact at which 
 the make and break of the local circuits are made. The adjustment should 
 
 Fig. 11-19. 
 
 -LONG SUBMARINE CABLES, CUTTRISS AUTOMATIC TRANSMITTERS, CON- 
 NECTIONS. 
 
 be such that the picker contacts are closed before the make is made on the 
 master contact ; also the picker contacts should be opened after the break 
 of the master contact. Improi)er adjustment will be indicated by the pickers 
 sparking. When sent out the instrument is carefully adjusted, but shoidd 
 later adjustment lie necessary the following; procedure is su.i^fiested : 
 
 See that the inside steel cam is fast on the shaft. Itevolve the armature 
 shaft until the slot in the steel cam is on top. At this point the pickers should 
 drop exactly in the center of the holes of tlu> outside star wheel. The pins 
 of the two star wheels should always be exactly opposite each other. With 
 the slot of the steel cam upward, it should be possible to revolve the armature 
 shaft a portion of a turn without moving the star-wheel shaft. The screw on 
 the master contact arm should then he adjusted for maximum period of con- 
 tact per revolution. As the armature shaft is revolved the master contact 
 should be broken just before the star wheel beirins to move. The pickers 
 should have very small play, just enoufrh to maintain the " open " in the 
 circuit. The make and break of the master contact should be properly timed. 
 This is adjusted when necessary by rotating the vulcanite eccentric cam on 
 the armature shaft so that the high point comes at the proper part of the 
 cycle. 
 
 "(46S)
 
 28 Signal Corps Manual No. 3.— Chapter 11. 
 
 TRANSXriTTER-TAPE PERFORATORS. 
 
 Tlic iicrforitfor iiKinufactnred liy the Kleinsclunidt Elet'tric Co., New York, 
 li.-i.s tlie aiiiH'ariiiici' ot a typewrilcr ; the (lei)rt'.s.sion of any one key makes all 
 perforation necessary for the corresponding; character. It is usually manu- 
 factured to operate on 110-volt direct current, but can be manufactured to 
 operate on hijrher or lower voltages. 
 
 This perforator requires no special skill for its operation, and has the 
 ailvantaije of being about three times as rapid as the familiar INIuirhead 
 type. One extra set of pimches and dies should be kept on hand. Specifica- 
 tions for maintaining, cleaning, and adjusting the Kleinschniidt perforator 
 may be obtained from the manufacturer. 
 
 NOTES ox THE EFFICIENT WORKINC OF A CAHLK STATION AND ON TROT'RLES THAT 
 
 OCCUR. 
 
 See that the batteries are kept in good condition and well insulated from each 
 other and outside damp or metallic surfaces. 
 
 All office leads should be well insulated. It is better not to bunch them 
 together or bend sharply at an angle. Whenever binding posts or switches are 
 used they should be frequently overhauled and cleaned. A high resistance 
 at a connection is a very common source of trouble. 
 
 Light, snappy sending over a long cable will produce weak and distorted 
 signals at the distant end. All contacts should be uniformly made and with a 
 cushiony or springy style. See that the levers of key spring back well 
 against the back contact, which becomes a part of the line circuit when the 
 opposite key is used. This contact also permits the cable to discharge to earth. 
 
 The amount of sending and receiving condensers to be used can best be regu- 
 lated by experiment, the resistance and capacity of the cable and the amount 
 of battery used being the chief basis to .ludge by (from 20 to GO micTofarads 
 gives a range sufliclent for all general conditions). Where no sending con- 
 densers are used it is well to interpose an- inductance coil between the line 
 and ground parallel with the receiving condenser and recorder. This in- 
 ductance coil is to have a resistance in series with it for adjustment. The con- 
 denser is to be shuntetl by an adjustal)le resistance. With this inductance leak 
 in circuit it will be necessary to increase the sending battery, as it acts 
 as a shunt on the recorder. With a ])ro])er adjustment of the resistance in 
 series with the liidnctance coil and of the resistance shunting the condenser. 
 tlie signals can be made of uniform defiection and will lose that irregular 
 rising and railing off which is a bad featmv in long cables. 
 
 If the (lislanl station coinidaiiis of signals being small or \V(>ak it is well to 
 lest the battei-y for voltage at the cable terminals, and if the voltage shows 
 normal the trouble is due to a high resistance caused either by bad contact 
 of llie key or other bad connections in the circuit. If there is a spare set in 
 the ollice. switch over iind ask if signals are any better. If the reply is 
 negative the trouble must be in some coimections which nvv coimnon to both 
 sets, which can be seen in the ollice diagram of connections. This is on the 
 assumption that there is no trouble at the other station. If the distant station 
 complains of key failing and states he gets no " dots " or only occasional " dots " 
 from yon the lionhle will invariably b(> found in a flirty point either at the 
 front contact of the "dot key" or the IkicI: cofitact of the "dash key." If 
 (lie complaint is of " daslu'S " failing the positions are reversed — that is, at the 
 
 (4r,\)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 29 
 
 front contact of tlie " dasli key" ami the back contact of the "dot key." A 
 li.ti;ht touch with a very fino file will clean the key contacts. The receiving 
 station shouhl overhaul and (itMii his connections in the switch and see that 
 Ills condenser and shunt coinjections and contacts are all right. A juniper 
 or hridge of a small i)iece of wire can be put across the different connections 
 in the switch to prove that tiie contacts are all right. A variable resistance 
 in the inductance coil circuit, or condenser shunt circuit, or a faulty condenser 
 will produce variable signals. After .seeing that the connections are properly 
 made and contacts clean, and the signals still varj' from large round signals 
 to small shai'p signals and at times come normal, the condenser should be tested 
 for insulation. 
 
 A faulty condenser will give the above effect. In case communication is lost 
 with distant station, cut out switch and office connections and run wires to line 
 and earth direct where they enter office and connect up as in diagram 
 (fig. 11-15). After calling for a sufficient time and no answer received, short- 
 circuit condenser by putting a wire across from plate "A" to plate " B " and call 
 again. This will prove if trouble is local or otherwise. 
 
 After both stations have overhauled their office connections and the trouble 
 still remains, tests should be made of the main cable and earth cable. In 
 the case of long underground cables it very often happens that joints become 
 corroded and eaten away. This is ijarticularly the case where there are electric 
 railways in the vicinity. 
 
 By keeping the field magnets adjusted close to the signal coil the trouble from 
 small, quick extraneous currents will be very much lessened. If the earth cur- 
 rents are very strong the shimt on the receiving condenser should be greatly 
 increased or set to infinity. When the earth currents interfere Avith operation 
 and the insulation of the cable will permit, the sending batteries may be 
 increased. 
 
 The signals can be regulated by the recorder shunt to the required size. One 
 of the principal things in maintaining good signals is the syphon and its vibra- 
 tiim. The point of the syphon should be uniformly ground and bent so as the 
 l)est flow of ink is obtainable. If the nose is bent too abruptly or not far 
 enough a very poor line is the result. It will be found when a new syphon is 
 put on that perhaps the period of vibration Is different from what it was for 
 the old syphon. It will then be necessary to adjust the interrupter by turning 
 back and forth and sliding the weight on the armature lever up and down \mtil 
 the proper period is obtained. Also, the rheostat in the battery circuit can be 
 changed to give desired effect. If the syphon is not properly mounted it will 
 be ditticult to get proper vibration. If blots of ink form rapidly on the nose of 
 the syphon it is better to change it and substitute one better ground. By heat- 
 ing a .small iron and putting a little wax on the nose of syphon a rough line can 
 be improved. Once the kind of syphon that gives best results is established a 
 dozen or so similar ones properly ground should be made ready for use so the 
 one can be readily mounted when necessary. Keep the bearings of the motor 
 well oiled and the battery contact maker cleaned and free from sparking. If 
 the contacts are too close and an arc forms, the battery will be run down 
 quickly and motor run irregularly. 
 
 (iltOUNUS FOR SIBMAKINE CABLES IN OR NEAR LARGE CITIES. 
 
 The earth in large cities and vicinity is charged with positive electricity 
 from electric-car lines and leakage from electric-light circuits. This positively 
 charged earth causes currents to flow into the surrounding country and espe- 
 
 (465)
 
 30 Signal Corps Manual No. 3.— Chapter 11. 
 
 cially on any conductor leading away from the cities, such as the armor of a 
 submarine cable which lands in the cities. 
 
 The delicate current used in submarine telegraphy is much disturbed by 
 these varying earth currents when the ground is made to the earth or cable 
 armor in or near the large cities. For this purpose an extra cable is run some 
 distance into the sea, its length depending on the amount of the disturbance 
 caused by the above-mentioned earth charge. 
 
 The single copper conductor of this earth cable should not be grounded 
 directly to the armor or other metallic body at the extremity of the earth cable, 
 for local galvanic action will occur between the two dissimilar metals, and 
 trouble from this cause will ensue. The copper core of the single-conductor 
 ground cable should be spliced to an iron wire, and all of the copper core and 
 the joint carefully insulated, to entirely exclude moisture, and this iron wire 
 carefully soldered to a mass of iron and then sunk in the bottom of the sea. 
 
 A better method is to use a two-conductor cable from cable landing to several 
 miles out to sea, splicing one conductor of the two-conductor cable to the 
 conductor of the long single-conductor cable and grounding the other conductor 
 in the following manner : 
 
 To connect the second conductor of the twin core to the sheathing wires of 
 the cable, proceed by preparing the armor wires for an overlapping splice in 
 the usual manner for joining two. single-core cables, except that on the end 
 that usually has all the wires cut off at the splice (the single-conductor cable 
 in this instance) five or six of the armor wires are made 7 or S inches longer 
 than the rest, so as to provide a convenient surface for making the groiind con- 
 nection. On the other cable end (two-conductor cable) the armor wires will, of 
 course, be left 20 or 30 feet long. The regular cable conductor is then spliced in 
 the same manner as when joining single-conductor cables together. After this 
 joint is completed and served with tape or spun yarn, mill (wrap) the copper 
 strands of the extra or ground conductor around the five or six armor wires that 
 were left longer for that purpose, making a joint 4 or 5 inches in length, which, 
 if possible, should be carefully wiped with solder. Both the copper and iron 
 wires should be thoroughly cleaned before the joint is made, and these joints 
 thoroughly insulated with i)ure rubber or Kerite tape, applied warm. It is 
 highly important that moisture does not come in contact with the joints between 
 the copper and galvanized-steel armor wires. After serving this joint and the 
 core splice with tape or spun yarn as a bed for the armor wires, you have a con- 
 dition that does not differ greatly from the joint of a two-conductor cable, the 
 splice being completed with the long ends of armor wires and served in the ordi- 
 nary manner. 
 
 In these methods there are no dissimilar metals exi)os(>d lo the wiiter to 
 cause trouble. 
 
 By soldering the grounds to the armor at the end of the two-conductor cable 
 the continuation of the armor to the distant end of the cable makes one of the 
 best grounds. 
 
 This method is employed by the Conunercial Cable Co. at New York City. 
 The two-conductor cable extends 10 miles to sea from the beach on which the 
 commercial cable lands near New York. The copper core to the ground con- 
 nection is joined to six different iron wires to insure a good ground connection, 
 each joint and all copper carefnlly insulated, and each of the six iron wires 
 wrapped around the armor and soldered. 
 
 (466)
 
 I 
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 31 
 
 CABLE TESTING. 
 
 The remarks appearing in this manual concerning the general necessity for 
 testing cable regularly, apply with added force in the case of long submarine 
 cables. 
 
 By applying regular tests incipient faults will frequently disclose themselves 
 long before they become sufficiently serious to interfere with the working, giv- 
 ing ample time to notify the repair ship, if the faults are out at sea. Further- 
 more, it is absolutely necessary in case of cables to locate them accurately by 
 tests, though this part in its refinements belongs in general to the cable-ship 
 experts. The subject of cable testing is extensively entered into by Kempe in 
 his Handbook of Electrical Testing. 
 
 The works already cited by Wilkinson and Bright also describe various 
 methods. Students' Guide to Submarine Cable Testing (Fisher & Darby), 
 Electrical Testing for Telegraph Engineers (J. Elton Young), Beginners' Manual 
 of Submarine Cable Testing and Working (G. M. Baines), and Testing of In- 
 sulated Wires and Cables (Webb) are recommended treatises on testing. The 
 Students' Guide and the three latter are compact treatises which are quite 
 elementary and easily understood. 
 
 It is proposed to describe such tests as are usually desirable at cable stations. 
 
 In making tests using delicate testing instruments such as the galvanometer, 
 let the rule be to begin with large fraction of shunt and small value of battery, 
 gradually decreasing fraction of shunt and increasing battery. This will pre- 
 vent damage to instruments due to excessive current strength. 
 
 In making the approximate measurements at stations the Weston milllam- 
 meter and voltmeter set may be used. These, of course, will not'give sufiiciently 
 accurate results when high-resistance faults exist. The Wheatstone bridge may 
 be used whenever measuring the ordinary resistances, and the ohmmeter will 
 answer for approximations. The Fisher cable-testing set, described later in 
 this chapter, combining, as it does, so many necessary instruments is con- 
 venient for Morse stations. 
 
 The reflecting galvanometer is a necessity in accurate cable measurements. 
 Not only does it give better results than any other form with Wheatstone bridge 
 measurements, but it is a necessity in insulation resistance and capacity meas- 
 urements, both of which are very important in cable work. Before considering 
 them the reflecting or mirror galvanometer will be described. 
 
 BEFLECTING GALVANOMETERS. 
 
 Any pointer or indicator attached to the movable coil or needle of the galva- 
 nometer increases the mass to be moved and decreases the sensitiveness. A 
 delicate mirror being attached to the coil or needle may be used to reflect a 
 beam of light onto a scale, thus giving a weightless pointer or indicator as 
 long as may be desired and consequently great sensitiveness. Another way of 
 utilizing the reflecting principle is to view the reflected image of the scale with 
 a small telescope, noting the number on the scale intersected by a vertical 
 thread in the telescope. Formerly the Thomson reflecting galvanometer (fig. 
 11-20) was exclusively used for any case requiring great sensitiveness. 
 
 The beam of light from the lamp L shining through the slit in the shield Is 
 reflected from the mirror attached to the suspended magnetic needle N and 
 projected on some point of the scale S. 
 
 (467)
 
 32 
 
 Signal Corps Manual No. 3. — Chapter 1 1 . 
 
 The needle swings in a small space in the middle of the coils, and the direc- 
 tion and stfenpth of the controllinj; force is given by the bar iiiauiH-t .1/. P>y 
 (his arrangement it is seen that a very small movciiicnt of the nccdU' ;iiid ihe 
 atiaclied nnrror will ho greatly niagnilied hi the niDNciiieiit of the s|)ot of light 
 on the scale. 
 
 Fig. 11-20.— LONG SUBMARINE CABLES, TESTING, THOMPSON REFLECTING GAL- 
 VANOMETER. 
 
 The Thomson galvanometer is well adapted to laboratory work, l)ut. for 
 testing cables after they are laid, where there are always some disturbing 
 (•urrents, it has been found that the Sullivan Universal galvanometer gives 
 better results; it is not so sensitive as the Thomson but is more "dead beat" 
 and manageable. The coil is suspended in the field of a i)ermanent magnet 
 and is dampened with a fine brush. 
 
 Fig. 11-21.— LONG SUBMARINE CABLES, TESTING, D'ARSONVAL REFLECTING GAL- 
 VANOMETER. 
 
 (KiS)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 1 I . 
 
 33 
 
 Galvanometers of tlio D'Arsouval class, witli a suspended coil turning in the 
 field of Ji p«'rmanciil iiia.iiiict. arc in ^'cncral use for all kinds of iiu'iisiirciiicnts. 
 While usually iml <>r such a liiirh dc;:i-cc n\' scnsitivoiU'ss as I he Thouisoii, they 
 are much more "dead heat" and niana.Lreahle. These are (luite pMierally used 
 as mirror galvanometers. 
 
 An excellent form for cable-station use is shown in figure 11-21. As will be 
 noted, these use the small telescope to view the .scale and should be so mounted 
 tliat the liyht from the window or lamp will fall on the .scale. 
 
 It will also be noted that this instrument is practically a duplicate of the 
 one described in chapter 4 of this manual, except that it is de.signed for mount- 
 in?? permanently or semipermanently on a wall while the one described in 
 chapter 4 is equipped with a tripod in order that the instrument can be con- 
 veniently set up in the field. 
 
 As explained in chapter 4 of this manual, any delicate galvanometers like 
 the above can not be used in most cases with the whole current involved in 
 the measurement, as even through a very great resistance a single cell will 
 cau.se the reflected image to move comiiletely off the scale, (consequently 
 shunts are provided which allow certain definite portions of the current 
 (usually i'o. -nnr- "i" r^^ t<» P^i^^^ through the shunt, and tu, tto. »n<l roW) 
 respectively, to go through the galvanometer. 
 
 m 
 
 999 
 
 o rMijlimrifTvis 
 
 • o 
 
 Fig. 11-22.— LONG SUBMARINE CABLES, TESTING, SHUNT, SIMPLIFIED DIAGRAM. 
 
 The simplified diagram is shown in figure 11-22. 
 
 By placing the plug at one or the other of the points a divided circuit is 
 formed, and a certain part of the current will flow through the shunl and the 
 other through the galvanometer. For example, ^ has ^ as much resistance 
 as the galvanometer. So -^ of the current will flow through this and yj^j 
 through the galvanometer. Hence, the deflection with this shunt will be only 
 YSTS as much as it woidd be if no plug were i)Ut in the shunt to bring the 
 deflection within readable limits. 
 
 (4G0)
 
 34 
 
 Signal Corps Manual No. 3. — Chapter 11, 
 Remarks on the shunt. 
 
 Resistance of shunt compared to 
 resistance of galvanometer. 
 
 Current through— 
 
 Whole 
 
 current. 
 
 Multi- 
 plying 
 power of 
 shunt. 
 
 Shimt. 
 
 Galva- 
 nometer. 
 
 1 
 
 999 
 
 1 
 99 
 
 1 
 
 9 
 
 No shunt 
 
 ^ + -^- = 1 
 1000 KHM) 
 
 ^ + i- = 1 
 100 100 
 
 1 + 1 = 1 
 
 10 ^ HI 
 
 + 1=1 
 
 1,0(K) 
 100 
 
 10 
 
 1 
 
 ^Multiply the deflection of the galvanometer hy the multiply in.a: power of the 
 shunt to obtain what the true deflection woidd he with lut shunt, wlien all cur- 
 i-ent passes through the pilvanometer. 
 
 Let fi=Resistance of jj'ilvanonieter, 
 K=Resistance of shunt, 
 .l/=]\rultiplying power of shunt, 
 
 Then .V=' 
 
 -S 
 
 S= 
 
 SM=G+S 
 
 G 
 
 "J7-1 
 
 Example: Let S=l and G=99 
 
 Q9 + 1 
 Then J/=^^ =100 
 
 ^' = 1X(10()— 1)=99 
 99 
 
 JS= 
 
 100-1 
 
 r=l 
 
 Fig. 11-23.— LONG SUBMARINE CABLES, TESTING, AYRTON UNIVERSAL SHUNT. 
 
 (-47(1)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 35 
 
 I 
 
 Goiv 920co 
 
 Fig. 11-24.— LONG SUBMARINE CABLES, TESTING, AYRTON SHUNT, CONNECTIONS 
 
 Tlio Ayrton universal shunt (figs. 11-23 and 11-24) is now frequently 
 u.-ied witli galvanometers of moderate resistances. One of these can be used 
 with any galvanometer regardless of their relative resistances, and it has the 
 advantage of being accurate for condenser and capacity measurements as well. 
 In this the shunts are more conveniently marked rwisui tsttj Ti> t- 
 
 The principle of the Ayrton universal shunt is that where the resistance of 
 the galvanometer is small in comparison with the total resistance of the shunt 
 the resistance of the galvanometer is ignored. 
 
 J/=Multiplying power of shunt. 
 G=Resistance of the galvanometer. 
 /S=Resistance of the shunt. 
 
 M= 
 
 G+S 
 
 Consider that resistance of the galvanometer itself is zero and that the pluj 
 is in the xTjVff *^'i^i"t, where the nudtiplying power is 1,000, then: 
 
 1000= 
 
 G+S 
 S 
 
 Call that part of the shunt in series with the galvanometer, the resistance 
 of the galvanometer, or 3.600+360+36=3,996 ohms, and the resistance of 
 the actual shunt A'. 
 
 Then ]00n=^^A+ ^ or 1000 A'=3996+A' or 999 A'=3996, where A' or the shunt 
 
 equals 4 ohmi5. 
 
 Substituting 4 ohms for S and 3996 for (i: 
 
 T.I • , .1 ^r 3996+4 4000 ,, , „„„ 
 
 Plug in rrhn^ tlien J/= .-^- or — — or J/=1,000 
 
 T>i • 1 +t ^f 3960+40 4000 ,, i,,„ 
 
 Plug in -i^js, then M= — ^~- or ~— or J/=100 
 
 T>i • 1 *i, ^r 3600+400 4000 ,, ,(, 
 Plug in A, then .1/= ^^^ or-^- or .V=10 
 
 111 • 1 *v, 1^ 0+4000 
 Plug in 1, then -V=-^^^^ 
 
 4000 „ , 
 "'•4000«'^-^^=^ 
 
 (471)
 
 36 Signal Corps Manual No. 3. — Chapter 11. 
 
 The miiltiplyinj; power is proved in eacli case, and it can also be seen that 
 the following rule in the Sullivan marine galvanometer shunt is proved, i. e. — 
 
 To obtain the multiplying power of the shunt, divide the total resistance 
 in the shunt by the amount of the shunt cut in. 
 
 As an actual fact, though, the galvanometer in the Fisher's set at Seattle 
 has 920 ohms resistance, adding that also to the G resistance used in the 
 examples above, the following results are obtained, showing that even 920 
 ohms in the galvanometer itself can be ignored, and the Sullivan rule is 
 again proved : 
 
 ■D, • 1 .1 If 3996+920+4 4920 ,, ,.,.,^ 
 
 Plug in xTnnr. "len J/= -i- '— or -— - or J/=1230 
 
 T>i- • • ,41 ^f 3960+920+40 4920 „ ,, ,.,., 
 
 Plug m -j^, then M= '—- — ■ — or — — or J/=123 
 
 1,1 ■ 1 ,1 If 3600+920+400 „ 4920 ,, ,., ^ 
 
 1 lug in ■^, then M— -r?.-^ or -^-^ or M=12. 3 
 
 ^' 400 400 
 
 -Di • 1 ♦!, If 0+920+4000 4920 ,, , .,^ 
 
 Plug in 1, then M= — ■ — -— !- or — -- or Ji=1.23 
 
 4000 4000 
 
 From the last set of examples, where the galvanometer has an actual re- 
 sistance, nearly one-fourth that of the shunt, it is found that though M is 1, 
 it should really be 1.23 ; yet the multiplying power of 10, 100, and 1000 is 
 exact, considering the M for 1 as the unit whatever it may be. Therefore, 
 the relation is the same as in the first set of values, where the galvanometer 
 itself had no resistance. 
 For— 1 times 1.23=1.23 
 
 10 times 1.23=12.3 
 100 times 1.23=123 
 1000 times 1.23=1230 
 
 and the multiplying power is unchanged by counting or not counting the 
 resistance of the galvanometer. 
 
 Another form of Ayrton shunt is shown in chapter 4 and is siiecially adapted 
 for portable testing sets. With the latter type the circuit key is made a part 
 of the apparatus. It will be noted that with these shunts the fractional di- 
 visions are 1, 0.1, 0.01, 0.001, 0.0001. The latter fractional division is a con- 
 venient addition when observing galvanometer constant, using one-tenth megohm 
 as known resistance, as by its use the full voltage of testing battery can be 
 used with De Arsonval galvanometers having a sensibility approximate to 
 those usually furnished. 
 
 The method of making lueasurements of insulation, capacity, and oliiuic re- 
 sistance, using instruments furnished with the Signal Corps electrical-instru- 
 ment case, are fully described in chapter 4 of this manual. Inasmuch as tests 
 on lonjj submarine cables using the same type instruments would be similarly 
 made, a repetition of the description would bo superfluous. However, with long 
 subinarin(> calilcs great care must be exercised to avoid doing anything that 
 will impair the insulation. The voltage used in making tests nnist be kept as 
 low as is j)osslble to attain desired results. Readings should be taken with 
 positive pole of battery to ground and IIkmi with negative pole to ground. 
 Should there be a variation in these readings, Ihe mean of the two should be 
 nccei)(e(l as true reading. 
 
 When tlie cable exceeds 100 miles in length, caparity measurements should be 
 made by Thomson's or Gott's methods. Descriptions of these are found in the 
 books of references. 
 
 (472)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 1 I , 
 
 37 
 
 I'M.mirc 11-25 sliows soiiio of llio specnal instrunn'nts used in .sul»iii;iriiie-cal)lu 
 testing at (•al)lo oflicos of the NN'asliington-AUiska Military, Cable and Tele^'rapli 
 System. 
 
 Discharge Key for measuring capacity 
 
 High-insulation Binding Posts Double Plug Switch 
 
 Fig. 11-25.— LONG SUBMARINE CABLES, TESTING, SPECIAL INSTRUMENTS USED. 
 
 If the piece of cable to be measured i.s short, its insulation resistance will 
 probably be very hij,'h, and a battery of from 50 to 100 cells in series will 
 be required. These may be the smallest-size dry cells, or one of the resrular 
 boxes of testing batteries. The regular testing battery is composed of chloride 
 of silver cells. On account of their first cost and liability to be ruined by even a 
 brief short circuiting, it is advisable 1o reserve this type of liattery for insula- 
 tion measurements onlv. 
 
 (473)
 
 38 
 
 Signal Corps Manual No. 3. — Chapter 11. 
 
 CONDUCTOB KESISTANCE. 
 
 This is usually called "copper resistance" (C. R.) in books on cable testing. 
 
 To measure the resistance of sound cable when it is coiled in the tanks, when 
 both ends are available the methods before given and cited in reference books 
 may be followed. Of course, the most satisfactor-y and accurate method is with 
 some form of Wheatstone bridge and mirror galvanometer when these instru- 
 ments may be had. Good approximations may be made with the ohmmeter, or 
 the combination of voltmeter and milliammeter, as stated in land-line testing. 
 It is evident that if we know the resistance of the cable per mile, and find the 
 total resistance of the cable, the length of it is equal to the total resistance 
 divided by the resistance per mile. This method is called to attention because 
 of its constant use in determining the lengths of pieces of single conductor 
 cable. Of course, the temperature must be taken into account, and the resist- 
 ance measured must be reduced to that at the temperature at which the resist- 
 ance per mile is stated. A table of temperature coefficients is given below. 
 
 Temperature coefficients for copper resistance. 
 
 Difference in 
 
 
 Difference in 
 
 
 degrees— 
 
 Coeffi- 
 cient. 
 
 degrees— 
 
 Coeffi- 
 cient. 
 
 Faliren- 
 
 Centi- 
 
 Faliren- 
 
 Centi- 
 
 heit. 
 
 grade. 
 
 
 lieit. 
 
 grade. 
 
 
 1 
 
 0.5 
 
 1.002 
 
 16 
 
 8.9 
 
 1.034 
 
 2 
 
 1.1 
 
 1.004 
 
 17 
 
 9.4 
 
 1.036 
 
 3 
 
 1.7 
 
 1.006 
 
 18 
 
 10 
 
 1.0385 
 
 4 
 
 2.2 
 
 1.008 
 
 19 
 
 10.5 
 
 1.041 
 
 5 
 
 2.8 
 
 1.010 
 
 20 
 
 11.1 
 
 1.043 
 
 6 
 
 3.3 
 
 1.013 
 
 21 
 
 11.6 
 
 1.045 
 
 7 
 
 3.9 
 
 1.015 
 
 22 
 
 12.2 
 
 1.047 
 
 8 
 
 4.4 
 
 1.017 
 
 23 
 
 12.7 
 
 1.049 
 
 
 
 5 
 
 1.019 
 
 24 
 
 13.3 
 
 1.051 
 
 10 
 
 5.5 
 
 1.021 
 
 25 
 
 13.8 
 
 1.054 
 
 11 
 
 6.1 
 
 1.023 
 
 26 
 
 14.4 
 
 1.056 
 
 12 
 
 6.6 
 
 1.025 
 
 27 
 
 15 
 
 1.058 
 
 13 
 
 7.2 
 
 1.0275 
 
 28 
 
 15. 5 
 
 1.060 
 
 14 
 
 7.7 
 
 1.030 
 
 2!) 
 
 16 
 
 1.062 
 
 15 
 
 8.3 
 
 1.032 
 
 30 
 
 16.6 
 
 1.065 
 
 In using this table note that in passing from a higher to a lower tempera tur(> 
 divide the observed resistance by the number opposite the degrees of difference 
 of temperature, and in passing from lower to higher multiply the same. 
 
 Example: A piece of cable is measured at 8")° F. and has a resistance of 1(K» 
 ohms. Tilt! resistance per mile (9.5 ohms) is giv(>ii at 7.5° F. The difference is 
 10° F. higher than the standard. 
 
 100-^1.021^97.94 ohms a 1 7.5° F. 
 
 and the length of the piece is 97.94-^-9.5 — 10.31 miles. 
 
 While tlie length of single-conductor cable can be ascertain(\l accurately by 
 this iiicIIkmI, it has been the author's experience that with nuiltiple-conductor 
 twiste(l-j)air cable only an approximation of the length can be obtained, because 
 on account of the twists and lay the conductors are actually longer than cable. 
 Not only are pairs twisted together, bill llie i»airs are wound spirally around 
 -the longitudinal center. 
 
 After laying the cable, in attempting to measure its resistance* through (he 
 ground cotmections at each end the simplicity vani.shes of measuring with the 
 Wheatslf>ne bridge and balancing until the galvanometer is at zero. It will be 
 found that after making connections and before depressing the battery key 
 
 (•174)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 1 I 
 
 39 
 
 tlinf if we depress the short-eircuit key a tleflectioii will generally be noted. 
 This is largely due to earth current (called K. C. in reference books). If it 
 were steady it could easily be dealt with. Unfortunately, it is not, and it is 
 constantly varying in direction as well. 
 
 Two ways of measuring to eliminate earth-current effects are de.scribed in 
 works on cable testing called, respectively, "Quick reversals " and "False 
 zero." (See pp. 59-62, 3d ed.. Students' Guide to Submarine Cable Testing, 
 Fisher & Darby.) A brief additional description of these may be useful. 
 
 r 
 
 Fig. 11-26.— LONG SUBMARINE CABLES, TESTING, COPPER RESISTANCE, CONNEC- 
 TIONS. 
 
 Tonnections for measuring coiijier resistance are shown in tigure 11-116. 
 A Ji is the reversing key, C is the Wheatstone bridge, G is the galvanometer, S 
 the universal shunt, A' the short-circuit key, F the testing battery. The bridge 
 is connected with the cable conductor E, prepared as shown, and A and the 
 bridge are connected to a brightened place on the cable armor wires for 
 ground connections, as explained under " Capacity measurements." Of course 
 in this case the distant end of conductor is connected with the armor wires 
 or ground. As will be seen, by depressing B the copper (or carbon) end of 
 the battery will remain connected with the ground, while the zinc goes to 
 cable conductor through the bridge. Due to tlie fact that the " zinc current," 
 as it is called, tends to clear away corrosion 'when measuring to locate a fault, 
 measurements made with it usmUly show lower resistances than when carbon 
 or copper is put to line by depressing ^1. However, as little effect of this 
 kind will be noted in sound cable with distant end well connected with ground 
 as stated, we shall assume disturbances due only to earth currents in 
 measuring. 
 
 The method by quick reversals will lirst be described. Depress Ji, wait a 
 second or two, and depress K. Balance as rapidly as possible, noting re- 
 sistance. Release 7?, then depress .1 and A', and again balance quickly. The 
 mean of these resistances will give the one approximately correct, unless there 
 is too great a difference between them, in which case the correction on page 
 56, 3d ed., Fisher & Darby, should be applied. 
 
 Balancing to false zero (F. Z.) is the usual method of providing for earth 
 currents in measurements of conductor (copper) resistances of cable. 
 
 46581^—17- 
 
 -31 
 
 (475)
 
 40 
 
 Signal Corps Manual No. 3. — Chapter 1 I. 
 
 Before depressing A or B, if we depress tlie sliort-circuit key we shall gener- 
 ally note a deflection. This is due to the earth current. Suppose it to be fairly 
 steady, its direction and amount should be noted. If variable, its mean in the 
 time usually occupied by balancing should be noted. This is the false-zero posi- 
 tion to which we balance, instead of the true or instrumental zero we have 
 heretofore considered. If the earth current or false zero is constantly varying, 
 it should be noted just before and just after taking a measurement, and the 
 false-zero position taken as the mean. Several measurements should be made 
 until several successive results are obtained which accord fairly well. A good 
 measurement of the copper resistance of the sound cable is an absolutely nei'es- 
 sary preliminary lo the location of faults when they occur. 
 
 The usual form t)f Wheatstone bridge used at Alaskan cable stations is shown 
 in figure 11-27. 
 
 The form of report below illustrates the manner of tabulating tlata pertain- 
 ing to long submarine cables. 
 
 The data which follows illustrates the character of report turned in on com- 
 pletion of cable. 
 
 BECOKD OF CABLK TESTS. 
 
 U. S. SIGNAL CORPS. 
 
 Date 
 
 Tests made by 
 
 Submarine calile num.ber- 
 
 Place. 
 
 -between and. 
 
 Gfilvanonieter constant. 
 (Through 100,000 ohms.) 
 
 Kind of galvanometer Voltage of battery. 
 
 fRight- 
 
 Shunt Deflection i Left__. 
 
 [Mean-. 
 Constant per volt. 
 
 INSULATION. 
 
 Cable current: Deflection (right or left), with shunt. 
 
 Voltage of battery Shunt 
 
 Deflections. 
 
 1st min. 
 2d min.. 
 3d min.. 
 •1th min. 
 otb min . 
 
 Zinc. 
 
 Carbon. 
 
 Mean. 
 
 -Vb.soluto insulaliun cud of throe minutes. 
 
 COPPKR RESISTANCE. 
 
 Deneclion 
 
 Earth current with .shimt 
 
 VoltaRo of battery JJridge ratios 
 
 Kcsistanoo, zinc to line 
 
 K<isi.st;uice, carbon to line 
 
 Meiin 
 
 The records show that the resistance should lie - - ohms. 
 Capacity measurements mu<ie when directeii. 
 
 \OTE.— Connect Ralvanometer .so that with zinc to line in insulation test the deflection will be to left. 
 One copy of this record will be retained and three mailed to the oflicer in charge. 
 
 (47t;>
 
 Long Submarine Cables, Telegraphy, and Tests. — ^Chapter 
 
 41 
 
 DATA PERTAIXING TO THE SITKA-SEATTLE CABLE WHEX IT WAS LAID. 
 
 (This data is sho^vn as an e.xample to be followed.) 
 
 i 
 
 Type. 
 
 Nautical 
 miles. 
 
 C. K. 60°. 
 
 C. R. tem- 
 perature 
 at bottom. 
 
 Sitka- 
 Seattle. 
 
 Seattle- 
 Sitka. 
 
 Temper- 
 ature at 
 bottom. 
 
 S. E. Sitka, 1903 
 
 1.987 
 
 6.533 
 
 9.040 
 
 11.672 
 
 6.768 
 
 7.800 
 
 4.914 
 
 43.365 
 
 61.264 
 
 40. 179 
 
 19.378 
 
 59.298 
 
 50. 172 
 
 5.050 
 
 21.780 
 
 63.370 
 
 14.860 
 
 6.770 
 
 2.470 
 
 54.470 
 
 17.000 
 
 91.170 
 
 12.900 
 
 13.060 
 
 2.800 
 
 17.440 
 
 .968 
 
 1.832 
 
 20.650 
 
 20.310 
 
 22.200 
 
 21.540 
 
 8.910 
 
 3.718 
 
 32.230 
 
 14. 702 
 
 24.386 
 
 9.800 
 
 11.020 
 
 10. 970 
 
 10.950 
 
 11.370 
 
 4.660 
 
 1.110 
 
 16. 420 
 
 5.760 
 
 14.020 
 
 8.000 
 
 7.700 
 
 2.600 
 
 Ohms. 
 
 16.92 
 
 55.66 
 
 77.02 
 
 99.44 
 
 57.66 
 
 66.45 
 
 41.86 
 
 369. 46 
 
 521.97 
 
 342. 33 
 
 165.10 
 
 505.22 
 
 427. 46 
 
 43.03 
 
 185.56 
 
 539.91 
 
 126.60 
 
 57.68 
 
 21.04 
 
 464.08 
 
 144.84 
 
 776. 77 
 
 109.90 
 
 111.27 
 
 23.85 
 
 148.59 
 
 8.25 
 
 15.60 
 
 175.94 
 
 173.04 
 
 189. 14 
 
 183.52 
 
 75.91 
 
 31.67 
 
 274. 60 
 
 125.26 
 
 207.77 
 
 83.50 
 
 93.89 
 
 93.46 
 
 93.29 
 
 96.87 
 
 39.-70 
 
 9.45 
 
 139.90 
 
 49.07 
 
 119.45 
 
 68.16 
 
 65.60 
 
 22.15 
 
 Ohms. 
 
 16.38 
 
 53.89 
 
 74.57 
 
 96.28 
 
 55.82 
 
 64.33 
 
 40.17 
 
 354.60 
 
 496.59 
 
 325.68 
 
 157.07 
 
 480.65 
 
 406.67 
 
 40.93 
 
 176.53 
 
 513.66 
 
 120.44 
 
 54.87 
 
 20.01 
 
 441.51 
 
 137. 79 
 
 739.00 
 
 104.55 
 
 105.86 
 
 22.69 
 
 141.36 
 
 7.85 
 
 14.83 
 
 167.38 
 
 164.62 
 
 181.53 
 
 176. 14 
 
 73.50 
 
 30.66 
 
 265.87 
 
 121.28 
 
 201.17 
 
 80.84 
 
 90.91 
 
 90.49 
 
 90.32 
 
 93.79 
 
 38.44 
 
 9.15 
 
 135.45 
 
 47.51 
 
 115.66 
 
 66.00 
 
 63.52 
 
 21.45 
 
 Ohms. 
 16.38 
 
 70.27 
 144.84 
 241.12 
 296.94 
 361. 27 
 401.44 
 756.04 
 1,252. 63" 
 1,578.31 
 1,735.38 
 2, 216. 03 
 2,622.70 
 2,663.63 
 2,840.16 
 3,353.82 
 3,474.26 
 3,529.13 
 3,549.14 
 3,990.65 
 4,128.44 
 4,867.44 
 4,971.99 
 5,077.85 
 5,100.54 
 5,241.90 
 5, 249. 75 
 5,264.58 
 5,431.96 
 5,596.58 
 5, 778. 11 
 5,954.25 
 6,027.75 
 6, 058. 41 
 6,324.28 
 6,445.56 
 6, 646. 73 
 6, 727. 57 
 6,818.48 
 6,908.97 
 6,999.29 
 7,093.08 
 7,131.52 
 7,140.67 
 7,276.12 
 7,323.63 
 7,439.29 
 7, 505. 29 
 7,568.81 
 7,590.26 
 
 Ohms. 
 
 7,590.26 
 
 7,573.88 
 
 7,520.49 
 
 7, 445. 42 
 
 7,349.14 
 
 7,293.32 
 
 7,228.90 
 
 7,188.80 
 
 6,834.22 
 
 6,337.60 
 
 6,011.90 
 
 5,854.88 
 
 5,374.23 
 
 4,967.56 
 
 4,926.63 
 
 4, 750. 10 
 
 4,236.44 
 
 4,116.00 
 
 4,061.13 
 
 4,041.12 
 
 3,599.61 
 
 3,461.82 
 
 2,722.82 
 
 2,618.27 
 
 2,513.41 
 
 2,489.72 
 
 2,348.36 
 
 2,340.51 
 
 2,325.68 
 
 2,158.30 
 
 1, 993. 68 
 
 1,812.15 
 
 1,636.01 
 
 1,562.51 
 
 1,531.85 
 
 1,26.1.98 
 
 1,144.70 
 
 943.53 
 
 862. 69 
 
 771. 7S 
 
 681.29 
 
 590.97 
 
 497. 18 
 
 458.74 
 
 449.59 
 
 314.14 
 
 266.63 
 
 150.97 
 
 84.97 
 
 21.45 
 
 'F. 
 45 
 
 Inter., 1903 
 
 45 
 
 Do 
 
 45 
 
 Do 
 
 45 
 
 Deep-sea, 1903 
 
 45 
 
 Do 
 
 45 
 
 Do 
 
 41 
 
 Do 
 
 41 
 
 Do 
 
 37 
 
 Do 
 
 37 
 
 Do 
 
 37 
 
 Do 
 
 Do 
 
 Do 
 
 Deep-sea, 1904 
 
 Deep-sea, 1903 
 
 Do!;;;!!;!!;;;:;!;;;;;;;;;;!;; 
 
 Deep-sea, 1904 
 
 Deep-sea, 1903 
 
 Do 
 
 Do 
 
 Do 
 
 37 
 37 
 37 
 37 
 37 
 37 
 37 
 37 
 37 
 37 
 37 
 37 
 
 Do 
 
 Do 
 
 37 
 37 
 
 
 37 
 
 Deep-sea, 1904 
 
 37 
 
 Do 
 
 37 
 
 Do 
 
 Do 
 
 37 
 37 
 
 Do 
 
 41 
 
 
 41 
 
 Do 
 
 45 
 
 Inter., 1903 
 
 45 
 
 Do 
 
 Do 
 
 Do 
 
 45 
 45 
 45 
 
 
 45 
 
 Do 
 
 45 
 
 Do 
 
 45 
 
 Do 
 
 45 
 
 Do 
 
 45 
 
 Inter., 1903 
 
 45 
 
 Inter., 1901 
 
 45 
 
 Inter., 1903 
 
 45 
 
 Do 
 
 45 
 
 Do 
 
 45 
 
 Deep-sea, 1904 
 
 45 
 
 Inter., 1903 
 
 45 
 
 S. E. Seattle, 1903 . . . 
 
 45 
 
 
 
 Total 
 
 931.336 
 4.477 
 
 7,934.96 
 40.43 
 
 7,590.26 
 39.26 
 
 
 
 
 Earth Seattle 
 
 
 
 
 
 
 
 
 Total 
 
 935. 813 
 
 7,975.39 
 
 7,629.52 
 
 
 
 
 
 
 
 
 Ohms. 
 K . from buov to Sitka 7,496. 000 
 
 C. K . from buoy to Seattle through office to dock. 
 
 Total 7, 590. 617 
 
 C". K . of Seattle ground end 39. 265 
 
 Total 7,629.882 
 
 Average D. R., absolute 2.25 megohms; 2,104 megohms pernautical mile. 
 
 rapacity "1903 type" 737.ir.fi nautical miles, at 0.593=437 microfarads. 
 
 Capacity " 1904 1 vpe" , . lS:3.s^>0 nautical miles, at 0.472= 87 microfarads. 
 
 Seattle shore end to dock 6 microfarads. 
 
 Total capacity by r.ott's method from Arlington Dock to Sitka, Alaska 530 microfarads. 
 
 Average temperature, Seattle to Sitka, 39.1° F. 
 Distance on charts, Seattle to Sitka, 856 nautical miles. 
 
 (477)
 
 42 
 
 Signal Corps Meinual No. 3. — Chapter 11. 
 
 Fig. 11-27.— LONG SUBMARINE CABLES, TESTING, WHEATSTONE BRIDGE. 
 
 DESCRIPTIOX OF FISHER CABLE-TESTING SET NO. 2. 
 
 Note. — In all measurements, with this set, let the rule be to begin with large fractional value of shunt 
 and small battery, gradually decreasing the shunt and increasing the battery. 
 
 This set .shown in figure 11-28 was originally designed by Mr. H. W. Fisher. 
 It is intended for work where a strictly portable set is required. 
 
 As it will frequentl}' be used for locating trouble, a special arrangement of the 
 bridge has been adopted so as to greatly facilitate Murray & Varley loop tests 
 
 Fig. 11-28.— LONG SUBMARINE CABLES, TESTING. FISHER CABLE TESTING SET NO 2. 
 
 (47S)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 1 1 . 43 
 
 for faults. Mr. Fisher lias also inlroduccd a method new to portahle eable 
 icstiiif; sets for locating; hi'caks in cables wiiere tlie conductor has parted; and, 
 ill addition to the usual one, a new method for measuring; capacity in which 
 no j,'alvanometer is i-(H|uired, a teh'plione Itein^ \isfd in phice of it. 
 
 Tlie i)arts are moimted on corrugated liard-rul»l)er pillars, which extend above 
 and below the base. 
 
 This tirrangement gives ii very good insulation, and one that will be found 
 entirely satisfactory, except under the most trying condition of moisture. The 
 changes from one test to another are acconiplished very easily and without the 
 use of inconvenient flexible cords. They are effected by double-throw switches 
 whicii are plainly marked so that it is not necessary to memorize a complicated 
 sclieme of connections. 
 
 Tlic standard of capacity has a single value of ttj microfanid. 
 
 The standard high resistance is 1( ){),(»( K) ohms, and is also a single value, not 
 subdivided. 
 
 In the Wheatstone bridge u marked variation from the usual commercial 
 type has been made. The change is introduced to facilitate measurements for 
 the location of faults. It is an extension of the Kelvin-Varley slides, and, since 
 
 lo , S> 3 * S 6 7 a * I 
 
 OvvwvQvvvvvOwv^OvvvvviOwvvvvQ^^^^ 
 
 \ O / » 3 ^ £ 6 7 e 
 
 iQwvmO^wvvOvvmvO^v 
 
 T£-/VS 
 
 
 Fig. 11-29.— LONG SUBMARINE CABLES, TESTING, FISHER CABLE TESTING SET NO. 2. 
 WHEATSTONE BRIDGE ARRANGEMENT. 
 
 it may not be generally known, the following description is given. It is a form of 
 Wheatstone's bridge resembling those having a slide wii'e in which the values 
 of the rheostat are fixed and the two arms of the bridge are varied until a 
 lialance is effected. The arrangement is represented in diagram in figure 11-29. 
 The points marked G and B are the points of attachment for the galvano- 
 meter and battery, i*espectively. At R are represented the four coils of the 
 rheostat, any one of which may be used, and at .Y the unknown resistance. 
 Between M and 2V are eleven coils of equal value, which form the bridge wire. 
 There is a contact point between each coil and the one next to it. The other 
 coils shown in the series marked " Tens " and " Units " are used to subdivide 
 the coils of the bridge. They constitute what may be called an electrical vernier, 
 by means of which the bridge wirie is subdivided to thousandths of its total 
 value. The two arrows in contact with the points marked 1 and 3 in the " Hun- 
 dreds " row and with the 2 and 4 in the " Tens " row represent contact arms 
 which can be moved along to make contact at any of the contact points, but are 
 always at the same distance apart, so that they have two coils between them, 
 
 (479)
 
 44 
 
 Signal Corps Manual No. 3.— Chapter 11. 
 
 IhCn 
 
 •;'7fftc 
 
 felD^c^^^^g© 
 
 J 78^0 
 
 ^ 
 
 
 
 ^ ^ ^ o 
 
 =c3 
 
 050 
 
 
 G-(D 
 
 iPq! 
 
 o .^^^o 
 
 050 
 
 o 
 
 Q 
 
 0.0 ©,® 
 
 @)^(§)<vi@>(g)«o(6) 
 
 (480)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 45 
 
 Tlioy are cnnnefted t<» tlio ends of the row of coils below them, so that these 
 Iwfi coils arc slniiited with the entire row of coils below. Consider now the 
 i-esull of lliis sliuntinn in the case of the "Tens" and "Units" colls. The 
 ti'ns are, for example, 11 coils of 80 ohms each. The units are 10 coils 
 of 16 ohms each. The two 8()-ohm coils l)etween the points 2 and 4 ar«' 
 shunted with the 10 IG-ohm coils; 160 ohms is shunted with 160 ohms, and 
 the resistance lietween the points' 2 and 4 becomes 80 instead of 100 ohms. 
 There are in the "Tens" series, for any posiiion of tlie double arms, actually 
 10 resistances of 80 ohms each. The point of galvanometer contact may be 
 placed at any position in the "Units" series, thus subdividing the shunted 
 coils in the " Tens " series to tentlis. The coils in the " Hundreds " series 
 are 400 oluns each, and are subdivided in tlie same way by tliose in the " Tens " 
 
 Q a33G^ 
 
 MUNOfieOS. 
 
 BA ¥ \ 6 A " '" '"'I 
 
 Fig. 11-31.— LONG SUBMARINE CABLES, TESTING, FISHER CABLE TESTING SET NO. 2 
 
 CONNECTIONS. 
 
 series. An example will make tlu^ use of the bridge clear. Assume that a 
 balance is obtained with 100 unplugged in the rheostat and the contacts in 
 the position shown. The bridge reading is then 287. Call this value .4. Then 
 
 X:R::A:\,m)-A, and X=i?-— ^ j=100|H=31.06. 
 
 l,UtX) — A. 
 
 The calculation of the fraction ff^ would take considerable time and might lead 
 to errors. To overqome the necessity for this we furnish, conveniently fastened into 
 
 for all values of A between 
 
 the lid of each set, a table giving the values of 
 
 1,000-^ 
 
 and 1,000. Reference to the table shows -~^ — -=0.3106 for ^=237. We have, 
 
 1,000 — .4 
 
 (481)
 
 46 
 
 Signal Corps Manual No. 3. — Chapter 11. 
 
 consequently, simply to multiply the value taken from the table by the re- 
 tsistante luiplugged in the rheostat to determine the value of X. From this 
 it will be seen the Wheatstone bridge measurements may be made and cal- 
 culated very rapidly. 
 
 In the actual construction the coils are arranged in three dials. The contact 
 arms and points are constructed so as to insure good contacts. 
 
 From the plan (fig. 11-30) and the diagram (fig. 11-31) the arrangement 
 and connection of the different instruments making up the set will be evident. 
 Complete information in regard to the measurements for whicli the set may l)e 
 used can be ol)tained from the following directions: 
 
 MEASIREMENTS OF ELECTROSTATIC CAPACITY. 
 
 In making tests of this nature a reflecting galvanometer should be em- 
 ployed, because the galvanometer of the testing set is not suthciently accurate, 
 nor has it a long enough scale to give good results. A reflecting galvanometer 
 should therefore be connected to the posts marked Ga. (Figs. 11-30 and 11-31.) 
 
 A few cells of battery can be connected to the posts Ba by means of the 
 flexible cords which come out through the hard rubber opposite said posts. 
 If a larger battery is required the flexible cords should be disconnected from 
 the battery of the set and connection from any other battery made to the 
 
 <x o-<=oi^^SH7: 
 
 Standard Conden 
 
 I 
 
 Fig. 11-32.— LONG SUBMARINE CABLES, TESTING, MEASURING ELECTROSTATIC 
 CAPACITY, SIMPLIFIED DIAGRAM. 
 
 posts marked Ba. ('onnect the two leading wires running from the conductor 
 of the cable and from the ground to " cable posts " and insert a plug in the 
 hole marked 1 of the shunt. Place the handles of the two double-throw 
 swilclies in the direction of the letters marked " C or / ", In this test the key 
 marked Ba serves to close the battery circuit, the contact point being held 
 in ithice by the linger or by i)ressing down the cam lever at the side of the 
 key. The key marked Ga serves as a short-circuit key in this test, and the 
 short circuit is reuK^ved from the galvanometer by pressing the key down or 
 by the u.se of the cam lever. Insert two plugs in the holes marked C, and be 
 sure that no plugs are inserted in the holes marked / nor in the hole marked G. 
 The test can now be made in the ordinary mniiner, as follows: 
 I'ress down the key marked Ba for about 10 seconds, or whatever the 
 required time of charging may be, and tiie instant before releasing it press 
 down tiie key marked da to remove the short circuit from the galvanometer. 
 Then tiie Ba key <'an bo released and the discharge deflection of the gal- 
 vanometer read. If it is too small, api)ly more battery until a sufficiently 
 large detlecticHi is oIjImIiumI, wliicii record. Next disconnect the cable lead 
 wire.s from the conductor and in like manner measure the. discharge deflec- 
 tion due to the leading wires. Then, -without in any way changing or dis- 
 <-onne<'liiig the leading wires, insert a |ilug at // to coniUM-t the 0..'{ microfarad 
 rondciiscr across tlH- cable jxists, and in like manner read the (liscliarge de- 
 
 (482)
 
 f 
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 47 
 
 flection of the condenser. It is not necessary to jam the plug too tightly in 
 place, because in doing so the hard-rubber posts may be strained. 
 
 To obtain the true discharge deflection of cable and condenser, siiiitnict 
 the dischargi! (h-fiection due t<> the leading wires from the oi)served discharge 
 deflection of cal)le and condenser. 
 
 Deflections are proportional to the capacities ; the proportion is direct. Then 
 letting 
 
 l//*'=Microfards. 
 A'^= Number of cells. 
 i1/=Multlplying power of shunt. 
 
 X=Cnpacity and D=Deflection of Icnown capacity discharge. 
 Z=Capacity and /)'— Deflection of uniinown capacity discharge. 
 7j=Length of cable in feet. 
 Then—K:X::D:D' 
 
 Hence X, the absolute capacity =— w- 
 
 L feet : — — - : : 5,280 feet, or 1 mile : X capacity per mile 
 
 Hence capacity per mi\e=^^^^^'-^^ 
 ^ ^ ^ DXL 
 
 In order to prevent the E. M. F. of the battery from changing in case of a 
 test being made when the leading wires were accidentally crossed or the cable 
 grounded, the cable or condenser is normally charged through the A megohm 
 box, but, if desirable, said resistance can l)e cut out of circuit by inserting a plug 
 in the hole marked tV megohm. This, however, is not recommended, as expe- 
 rience shows thnt on short cables it has little or no etTect. However, in meas- 
 uring the capacity of long cables, the ttj megohm should l)e removed, as it 
 has a retarding elTect on the charge and ilischarge of the comparatively large 
 current involved. 
 
 NOTES ox CAPACrrV MKASTREMENTS FROM STANDARD UNDERGROXTxi) CABLE CO.'s 
 HANDBOOK NO. XVI.I, 1900. 
 
 With telephone cables there are two methods of making the connection ior 
 tests of electrostatic capacity : 
 
 (1) The regular or old trade standard method of testing to ground, with the 
 connections made in the same maimer as for a test of insulation resistance, 
 namely, one wire against the remaining wires grounded to the sheath. 
 
 (2) An entirely different test for mutual electrostatic capacit.v, in which one 
 wire is measured against its mate, the remaining wires being grounded to the 
 sheath. 
 
 The electrostatic capacity by the last method of connections is the least, being 
 about two-thirds the capacity by the former method of connections. 
 
 The use of the shunt has already been thoroughly explained, and if neces- 
 sary can be used in this work, but for very accurate determinations, unless it is 
 calibrated especially for capacity tests, it can not be relied upon, because the 
 self-induction of the shunt does not generally bear the right relation to the 
 self-induction of the galvanometer, so that the sudden discharge current will 
 not divide in both circuits in the same ratio that it would for steady currents. 
 If the condenser capacity is limited so that it can not be made comparatively 
 near the capacity of the cable, good results can be obtained by subdividing the 
 battery for whichever has the largest capacity. For instance, let us suppose 
 
 (48?.)
 
 48 
 
 Signal Corps Manual No. 3. — Chapter 1 1 , 
 
 that the condenser has four times the capacity of the cable, then we sliouUT 
 divide the l)atter.v into about four equal parts and take the discharjie detlection 
 t>f the condenser for each of these, use the sum of the above, which rei)resents 
 the discharge deflection that would have been obtained had the full battery 
 been used and were the galvanometer scale long enough to read the detlection. 
 The full battery should then be used to obtain the discharge detlection of the 
 cable. If the cable has the larger capacity, the operation should be reversed. 
 
 MEASUREMENTS OF INSULATION RESISTANCE. 
 
 In making the measurements of insulation resistance a reflecting galvanom- 
 eter can be used by connecting it to the posts marked Ga (tigs. ll-30.and 11-31) 
 and disconnecting the flexible leads adjacent thereto which run to the horizontal 
 galvanometer, or when approximate tests have to be made the galvanometer of 
 the set can be employed by connecting the above-mentioned flexible leads to 
 the post marked Ga. In like manner an auxiliary battery can be connected 
 to the posts marked Ba, or the battery of the testing set can be employed by 
 connecting the number of cells required to the flexible cords adjacent to Ba. 
 Use small battery at first and gradually increase it until a suitable detlection is 
 obtained. After making the connections indicated above the handles of the two 
 
 SIMPLIFIE.D INSULATION RESISTANCE DIAGFIAM 
 
 SIMPLIFIED DIAGRAM 
 OFTHE FISHER TESTING SET 
 
 FOR CAPACITY AND INSULATION TEISTS 
 
 Fig. 11-33.— LONG SUBMARINE CABLES. TESTING, MEASURING INSULATION RESIST- 
 ANCE, SIMPLIFIED DIAGRAMS. 
 
 (484)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 40 
 
 double-pole double-throw switche,s are placed in the direction of tlie letters " C 
 or / ". The two leadinj? wires from the cable conductor and from the ground are 
 connected to " cable posts." Insert plugs into the two holes marked / and .see 
 that no plugs are inserted in the holes inarkeil C, (J, and //. The test can now 
 be niaile in the ordinary manner, as follows : 
 
 Close the battery circuit by means <»f the key Ba and its accompanying 
 holding-down cam. Shortly before the period of electrification, which is gen- 
 erally one minute, has elapsed, press down the key marked Ga to remove the 
 short circuit from the galvanometer, when tlie ('.ellcction can be read. Tlicn dis- 
 connect the leading wires from the cable conductor and in like manner measure 
 the deflection due to the leading wires, which must be subtracted from the 
 observed deflection first read to give the true deflection due to the cable. 
 
 At first use j^Vs shunt, gradually decreasing the shunt to 1. 
 
 In taking the constant with Fisher's set the presumption is that the same num- 
 ber of cells is used both in taking the constant and in measuring the unknown 
 insulation; consequently tiie number of cells is not considered in the formula. 
 Where it is necessary to vary the number of cells, the voltage in each case must 
 be taken into consideration. This is thoroughly explained in chapter 4 of 
 this manual. 
 
 The insulation constant of the galvanometer is next determined, as follows: 
 
 The deflection is taken through 100,000 ohms or yV of a megohm, therefore remove 
 the plug from the hole marked x'cr megohm and insert a plug at G. Use whate^ er 
 shunt will give the best readable deflection, which we will call D. Then the insula- 
 tion constant of galvanometer =—- t=G 
 
 lOXshuntused 
 
 G=Galvanometer constant, or deflection through 1 megohm. 
 Z)= Deflection through t^s meghom. 
 il/=Multiplying power of shunt. 
 Large deflection : Small deflection : : Large resistance : Small resistance. 
 DXM : G : : 1 megohm : its megolim. 
 
 G=DXMX^. 
 Let /)'=Deflection due to the cable. 
 L = Length of cable in feet. 
 
 Q 
 
 Absolute insulation resistance of the cable=^— -— ^. 
 
 For: Large resistance : Small resistance : : Large deflection : Small deflection. 
 
 Absolute resistance : 1 megohm : : G : D''XM. 
 
 If absolute resistance is less than 1 megohm, the words " Large " and 
 " Small " in above proportion should be reversed. 
 Insulation inverse to distance — 
 Large distance : Small distance : : Large per mile : Small absolute 
 
 insulation insulation 
 
 Q 
 
 L feet : 5,280 feet :: per mile insulation : jyj^ 
 
 GL 
 
 Insulation per mile=-- — — — — — — 
 
 ^ Z>XJ/X5,280 
 
 It is best to make the regular insulation resistance test with the i^ 
 megohm in series, and this is done by removing the plug from the hole 
 marked ^ luegohm. This is advised so that the battery can never be short- 
 circuited. Where great accuracy is desired the t^ megohm can be subtracted 
 from the calculated absolute insulation resistance to get the true insulation 
 resistance. 
 
 (485 »
 
 50 
 
 Signal Corps Manual No. 3. — Chapter 1 1 . 
 
 MEASITJEMENTS OF CONDUCTOR RESISTANCE. 
 
 Place the handles of the two douhle-pole douhle-throw switches in the dii-ec- 
 tiou "R or M or V ", figure 11-31, insert a plug in the hole marked R, and at the 
 same time see that no plugs are in the holes marked M or V. It will be noted 
 that there are four resistances, viz, 1, 10, 100, 1,000 ohms. Any one of these can 
 be used in the test by removing its corresponding plug and inserting plugs in 
 llie other three holes. Before connuencing the test a resistance near to the 
 probable resistiince to be measui-ed should be loft unplugged. For instance, 
 if 5 oluns or less have to be measured the 1 ohiii resistance sliould be left 
 
 GCNEIRAL SIMPLIFIED DIAGPAM FOR FPCSlSTANCE MCASURCMENT 
 L 
 
 R=lcrlOotlOOorlOOO 
 
 Simplified Diagram of the Fishef-S Testing Set 
 
 for Resistance, Murray Loop and Varley Loop Testj 
 
 >■ 10 Coils of fOOu •oth - looo • 
 10 Coils o/aou eoch-soo. 
 *■>■ to Coi Is of IfrM •och - 160 ». 
 
 Fl?;. 11-34.— LONG SUBMARINE CABLES, TESTING, COPPER RESISTANCE, MURRAY 
 AND VARLEY LOOP, SIMPLIFIED DIAGRAM. 
 
 unplugged. If lilt' jirobablc icsislaiicc In lu' iiu'usiircd lies l)elwoen .'"> and HO 
 olims the 10 oiinis resistance siioidd l)e h'ft uiiphigged ; if tlie resislance to 
 be measured is over ilO ohms the 100 (»hms resistance sliouid be left unplugged. 
 (!<iniiect in Ihe resistance in be measured to the posts L and A'. By means 
 nf liic licxiide cords opimsitc llic posts marked ftii connect a few cells of 
 biillcry al lirsl, and if necessary tlic wlmlc IL* cells latei-. ('onnect tlie llexible 
 
 (48(!)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 1 1 , 
 
 cords opitosile llie itosts nmrketl (la lo said posts. For tlie coniiuencement of 
 the test use Tiym! shmit, decreasinj? shunt by steps to 1. 
 
 The test can now be made by first placing the arms of the " Tens " and 
 " Units " dials at zero and moving the " Hundreds " dial to J. Press down 
 tirst the battery key and instantly thereafter the galvanometer key, and note 
 tlie direction in which the galvanometer pointer moves. If the battery flexi])l(' 
 cords have been connected as indicated by the corresponding plus and niiiuis 
 signs, a deflection of the galvanometer toward the plus sign indicates that 
 the dial i-esistance must be increased, while if the deflection is in the opposite 
 direction, the dial resistance must be decrea.sed. With this information in 
 mind an instant only is required to determine between which two sets of 
 " Hundreds " the balance point lies. Having found this, place the pointer at 
 the lowest of the two, and in like manner determine between which two sets of 
 " Tens " the balance point lies, placing the switch at the lowest of these. The 
 final balance can then be found by rotating the " Units " switch until a point is 
 i-eached when there is no deflection of the galvanometer. With the " Tens " 
 and "Hundreds" switches the reading is tid<en between the two contact arms, 
 while with the " Units " switch the reading is taken at the segment with 
 which the rotating arms is in contact. 
 
 Note. — In using Fisher's Set, for Resistances, or Murray &; Varely loop test, 
 it is always best to keep the simplified diagram before the tester's eyes, as it 
 facilitates thorough understanding. This diagram can be roughly drawn in less 
 than one minute. 
 
 B=IOOO-A 
 
 R = l, 10. lOOorlOOO 
 
 Letting R = the implugged resi-stance to the right of the double switches. 
 I-etting A = the reading of the dial switches arranged in the order of 
 hundreds, tens, units, 
 
 A:X ..1,000— A.R :.X=-^--^^ - ohms the resistance to be measured. 
 1,000— J. 
 
 Tlic value of tlie teiui J - can be found in the aceompaiiyiiig table, when it 
 is only necessary to multiply said value by t'.ie amount of resistance unplugged. 
 
 iirUUAY LOOP MKTHOI) OF LOCATING CKOr.NDKD OK IHOSSKI) WlKKS. 
 
 This is the simplest method of locating grounds or crosses, and is cliierly 
 applicable when the faulty and good wire are of the same size and length; 
 hence it can be used to locate such faults In telephone and telegraph cables 
 where all the conductors seldom become faulty before the method can be applied. 
 It can also be used in the case of an electric cable where the outgoing and 
 incoming cable are the same size and length and where one of them is not 
 faulty. To apply this method, join the faulty and good conductor at the distant 
 end of the cable and connect the faulty conductor to L and the good conductor 
 to K. Place the two double-throw doul)le-pole switches in the direction of "R or 
 21 or V ", insert plugs in the two holes marked J/, and be sure that no plugs 
 
 i4S7)
 
 52 
 
 Signal Corps Manual No. 3. — Chapter 1 1 . 
 
 are in the two holes marked, respectively, V and R. The resistances 1, 10, and 
 100 can be either plugged or unpluggetl without affecting the test. Connect the 
 ground, or in the case of a cross the wire crossed with the ono used in the 
 test, to the post marked Gr. The galvanometer and battery are connected in 
 the same manner described under " Measurements of conductor resistance." 
 The description there giving the operating of dial switches is exactly the same 
 as must be followed in this case. 
 
 B = lOOO-A 
 
 Part : WTiole : : Part : Whole 
 
 yl: 1,000 
 
 A' : L or whole loop .". X=- 
 
 4Il 
 
 .000 
 
 Letting .4 = the reading of the dials which gives a balance of the galvanom- 
 eter. 
 2v=the total length of the circuit=twice the length of the cable 
 if the good and bad wires are in the same cable. The 
 length can be in inches, feet, yards, miles, or ohms, and X, 
 the result, will be in the denomination used. 
 
 Then, 
 
 The distance to the fault from the post L= 
 
 AXL 
 1000" 
 
 The check method can now be applied by connecting the faulty conductor to 
 
 ^and the good conductor to L. 
 Letting J.^= the reading of the dials, which gives a balance. 1,000 — J.' should 
 
 =A, which substitute in the above equation for A, which gives 
 
 — — X L the distance to the fault by the check method, which 
 1000 ^ 
 
 should be the same as before. 
 
 Another mctliod of cliecking the accuracy of thc^ rc'sult is lliat in every case 
 .1.1' siiould e(|ual 1.000. 
 
 When dealing witli faulls of higii resistance, .lO or more ci'lls of battery 
 iiiiiy have to he us(>(I. The l)a(tery should be connected to the posts Bo, and 
 the corresponding llexilile cords sliould be disconnected from the battery of 
 the set. 
 
 Tlie Murray looji may lie used where the two wires conslituling (he loop 
 are of different kinds and resistances. First measure resistance of looj), then 
 take a Murray loop test, when .V will be found in ohms; convert .V into dis- 
 tance by reference to wire tables. 
 
 VARI.KY I.OOI' MKTIIOI) OK I.OCATINC CatOt'NDEI) OR CUOSSKn WIKKS. 
 
 Tlie Murray loop irietlmd Is jireferable to the Varley loo)) nielho<l with the 
 Fisher's set, for with tlie Murray loop no e.xlra resistance If is added, nor is 
 it re<piired ; while the Varley looj) test calls for extra resistance A' and its 
 elimination, with no increase in edicMMicy to roiiip(>nsate for the extra labor. 
 
 (488) 
 
 I
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 53 
 
 Join the faulty and jiond condurtor at the distant end of the cahle, and at 
 the near end of tiie calile connect the former to the post marked L and tlie 
 latter to the post marked K. Then measure the resistance of the circuit as 
 described under " Measurements of conductor resistance." 
 
 Let r=said resistance. 
 
 Place the handles of the two double-throw double-pole switches in the direc- 
 tion of "iiJ or .17 or V ". Insert plui^s in the two holes marked V, and see that no 
 plugs are in the two holes marked, respectively, M and R. Join the faulty and 
 good wires at the distant end of the cable and connect the former to L and 
 the latter to K ; connect the ground or, in the case of a cross, the wire crossed 
 with the one used in the test, to the post marked Gr ; unplug the resistance 
 marked 100 and plug the resistance marked 1 and 10, connect the battery and 
 galvanometer and operate the dial switches in the same manner described 
 under " Measurements of conductor resistance." If the balance can not 
 readily be obtained, it may be necessary to unplug the 10-ohni or perhaps the 
 1-ohm ; the other two resistances must, of course, be plugged. The dial 
 switches are now operated, as described under "Measurements of conductor 
 resistance," until a balance is obtained, when the reading is I'ecorded. 
 
 B = IOOO-A 
 
 Let R—the resistance unplugged in the rheostat, 
 Let r=the resistance of the faulty and good wires, 
 
 Lfet A=the reading of the dials which gives a balance of the galvanometer, 
 and. 
 
 Let 5 = 1.000—1, 
 
 Let a=the resistance to the fault from L, 
 
 A :1, 000 :: a ohms: r+ E(o]\m^).- A .000(1= ArXAr.\a=^^^'^^:^ ohms 
 
 1,000 
 
 CHECK MKTHOl). 
 
 Connect now the faulty wire to A' and the good wire to L, and proceed in flic 
 same manner to timl the new values ^1, B, A", and a, which for the check method 
 we will call A', B', A', and a'. 
 
 B'=IOOO-A' '-^"'^ 
 
 (489)
 
 54 Signal Corps Manual No. 3. — Chapter 11. 
 
 The resistance to the fault from ; 
 
 B':1.000::(R'-\-a'):iR'+r) 
 
 l,000a'+l,000R'=B'Ji'+B'r:.1.000a'=B'r+B'R'-l,000R' 
 As B'=l.OOO-A' substitute it for B' 
 Hence: 1.000a'=jB'r+l,000i?^-^^i?^-l,000A'^ 
 
 D/ 4^ R^ 
 
 a'= ~ — - ohms. Answer, which should be the same as found iox "a" above. 
 
 1,000 
 
 Let ?) = the resistance of tlie faulty \vire=one.-halC the resistance of the loop 
 where good and bad wires are of the same size and are in one cable. 
 
 Let L=the length of cable. 
 
 Then, 
 a ohms as found above : b ohms : : A', the distance to the fault by first method : L 
 Hence — 
 
 a' ohms as found above : b ohms : : X the distance to the fault by check method : L 
 
 Hence: X=^;— which should equal ^— 
 b 
 
 a ohms should equal a' ohms. 
 
 ARRANGEMENT OF TESTII^JG SET. 
 
 The convenient arrangement of the testing set at the cable office is of great 
 importance. Not only does this make tests easy, but it tends to accuracy as 
 well, since troubles are easily traced in sets where the wiring is well laid 
 out and all parts of instruments easy of access. 
 
 The wiring should invariably be done with best rubber-covered wire or, better, 
 cable core, supported on porcelain cleats or knobs. The layout of the instru- 
 ments on the table is shown in figure 11-8."). Tlie galvanometer should be on a 
 .separate shelf not connected with the table. It should be about the height of 
 the shoulder from the floor. On the opposite end of the table the lamp and 
 scale are supported at the same height on a shelf or stand separate from the 
 table. By this arrangement of the galvanometer, lamp, and scale, the scale is 
 in full view while the Wheatstone bridges or keys are being manipulated. 
 
 The galvanometer lamp is usually an electric lamp, with a straight filament, 
 placed behind the slit in the scale, and the concave galvanometer mirror rotU'cts 
 an imag(; of the filament as a brilliant vertical line on the scale, when the scale 
 and galvanimieter are the proper distance aiiart for correct focusing. If electric 
 light is not available, an oil lamp may be used. 
 
 EXCESSIVE E. M. V. NOT TO HE I'SEO. 
 
 After a vnhlo is laid, the E. M. V. used in testing sho\dd not exceed 40 volts, 
 ex(«>pt when necessary to obtain the recpiired current in IcK'ating breaks, when 
 a rea.sonable increased voltage may be u.sed, but should be applied to the cable 
 the shortest time i)ossible to obtain desired results. 
 
 (400)
 
 Long Submarine Cables, Telegraphy, and Tests.— Chapter 11. 55 
 
 46581°— 17- 
 
 (491)
 
 56 
 
 Signal Corps Manual No. 3. — Chapter 1 1. 
 
 The resistance box. adjustable from 2 to 11,220 ohms, sliowu in tisure 11-35, 
 is used in the battery circuit when making bridge measurements, and readily 
 permits adjustment to the proper current strength as shown on the milli- 
 ammeter. 
 
 For locating high resistance leaks, when sufficient variation of the current 
 by using reasonable voltage can not be obtained, recourse must be had to 
 Clark's potential test, or Jordan & Schonau's modification of the earth overlap 
 test appearing later in this chapter. 
 
 ©BINDING POST 
 
 1666661 
 
 ^ AFTER 
 3TAN>\^ 
 
 OOQ 
 
 O 
 
 o 
 o 
 o 
 
 o 
 
 F?ESISTANCE 
 
 i-k>vwvvO 
 
 GROUND (^ArE 
 
 'fJote-Connections from binding posts otsparkinqset 
 to cable are made by flexible ivires wth tnps 
 on the ends, via the bow leads 
 
 REICORDER" 
 
 Q 
 
 r^ 
 
 rO 
 
 Pi 
 
 |i|i|i|*U 
 
 DIAGRAM or SPEAKING CONNECTIONS, U.S. A.T. BURNSIDE. 
 
 ^ C-S» DATA 
 
 / \ I* \ Camtantpluiittt'roijIiibanjnrcoffatjhayKjii'^ Ruri7, 
 
 
 MUaTJMUAx] 
 
 ^^^Jfff!lJ^Z^t::^^ 
 
 Fig. 11-36.— LONG SUBMARINE CABLES, TESTING. TEST ROOM CONNECTIONS, U. S. 
 
 A. T. BURNSIDE. 
 
 (jarc iiuist be taken in 11h> insulation t(>st not to dopross short-circuit key until 
 cable has been charged U>v It) or l."i seconds. 
 
 To get capacity indications on gMlvanometer the amount of "throw" of 
 galvanometer on oi»eidng or closing nncrsing key irit]i the Hhort-circuit 
 key (hprcHHcil will give the capacity, i)rovided the amoinit of this tlirow is 
 compared witii that given by a condenser of known capacity connected in 
 place of line and earth, when l>;ittei\v and sliiinl ai'e Ihe same in both ca.sc's. 
 
 (492)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 57 
 
 It imisl he understood that tliis method gives reliuhle indiralions only with 
 comparatively short cables. For long cables Gott's test, described at length 
 in the books of reference, should be employed. 
 
 In all measurements let the rule be to begin with a large shunt and small 
 battery, gradually increasing the battery and gradually decreasing the shunt. 
 This method will prevent damage to the instrument. 
 
 LOCATION OF FAULTS IN SIIJMAKINK CABLES. 
 
 The application of the measurements just described in the local i<)?i of faults 
 may now be dealt with. The more complete exposition of the subject in the 
 books of reference cited is recommended to those wlio desire to go into the 
 matter more deeply. 
 
 Faults on cables are similar in iiattirc to llmsc on land lines. AN'licii tli(> 
 cable is comi)letely I'uptured faults may be dcscrilu'd under the folUjwing 
 headings of Chuss I : 
 
 Class I: First. The conductor is in coiitacl witii liie metal slu^athiiig and is 
 " dead grounded." 
 
 Second. The conductor is considerably exposed hy nnicli ot" the insulation at 
 and near the end being broken away. 
 
 Third. When the end of the conductor is only partially exposed or deeply 
 buried in nuid and sand. 
 
 Fourth. AN'hen the insulating material is di-awri well oxer the broken end of 
 the c<»ndi:ctor almost completely insidating it. 
 
 Class II: Conductor ru])tured ; insulation remainiui; iiitacl. 
 
 Class III: Break or abrasion of the insulating mateiial. causing either a 
 high-resistance leak (escape) or one approximating to a "dead ground," de- 
 l»ending upon the amoiuit of exposure of the conductor. 
 
 The behavior of the fault inider working conditions oi; test will usually de- 
 termine to which class it belongs. 
 
 Rupture of the cable is attended, of course, with total cessation of signals 
 fnmi the distant end, and this iisually occurs su<ldeidy. The end of the con- 
 ductor is generally left more or less exposed. If left much exi)osed, or grounded 
 on the cable armor, the galvanometer will indicate a comparatively steady cur- 
 rent when moderate battery power is applied. If the exposure is small, or the 
 end is buried in mud, great fluctuations in tlie current will be produced, and 
 greatly different when different ends of the battery are placed to line. If the 
 conductor is well drawn back into the insulation, or the conductor is ruptured 
 inside the insulating covering, of course notliing but the transitory current of 
 charge and discharge will be observed. 
 
 Damage to the insulation, exposing more or less of the conductor, very 
 frequently is first noted as a "leak," which bi'comes worse and worse, until 
 connnunication is interrupted. Unless the damage is extensive, the reception 
 of feeble signals from the distant station will disclose that the fault belongs 
 to Class III and that the cable is not ruptured. 
 
 In locaing the first of Class I it is evident that it requires only the measure- 
 ment of the copper resistance. This divided by the resistance per mile will 
 locate the fault. In No. 4 of Class I and in Class II a measurement of capacity 
 is required. This divided by capacity per mile gives the distance. 
 
 In all the others where partial exposure of the conductor is involved and 
 only one end is available at the testiug room, localization is difficult, owing to 
 the polarization at the fault and its consequent change of resistance with dif- 
 ferent sti-engths and directions of current, \\hea faults are minute this polari- 
 
 (493)
 
 58 
 
 Signal Corps Manual No. 3. — Chapter 1 1, 
 
 zation changes resistances from a few ohms to thousands, and vice versa, with 
 such rapidity as to require the greatest sliill and judgment in testing. In 
 general, by putting zinc to line, the generation of hydrogen and consequent 
 cleansing from metallic salts at the fault tends to open it up ; while putting 
 carbon or copper to line, by coating the fault with chloride of copper, will cause 
 the resistance to rise by sealing up the fault. 
 
 If the defect in insulation is small it is sometimes difficult to detect which 
 pole causes the most rapid polarization. 
 
 When the cable is coiled in the tanks, where both ends are available, or when 
 two cables have been laid between two points permitting their looping at the 
 far end, or when the cable has multiple cores one or more of which remain 
 uninjured, faults in the insulation of a cable, where the conductor is not broken, 
 may be quite accurately and easily located by the " loop test." This being the 
 simplest method of locating these faults in cable, it will be dealt with first. 
 
 First measure the resistance of the loop which we will call Tj with the two 
 ends of the conductor connected to the Wheatstone bridge. Then change the 
 connection, as shown in figure 11-37. 
 
 fl I I I I I I 
 
 m - 16 used to tahe copper resistance of' the loop, 
 g - is used to balance for the loop lust ^hen one 
 IS used the other is not used. 
 
 Fig. 11_37._LONG SUBMARINE CABLES, TESTING, LOCATION OF GROUND, 
 LOOP TEST, CONNECTIONS. 
 
 SIMPLE 
 
 It will be noted that the end with small resistance between it and the fault Y 
 must i»e connected with A', otherwise no balance can be obtained. When this is 
 found to be the case transpose the ends. When balance is obtained call the 
 values in balance arms a and h and anu)unt unplugged in resistance R, as noted 
 in diagram. 
 
 a : « + /> :: A'' : L-\-R or Tart : Whole; " !t*arf : AMiole, which is similar to the loop 
 proportiona for the Fisher's set previously shown, 
 
 (404)
 
 Lx)ng Submarine Cables, Telegraphy, and Tests. — Chapter 11. HP 
 
 Hence — 
 
 a+b 
 Wlien— 
 
 a=b we have X=«(^+^) or X=ldrli 
 2a 2 
 
 To find the value of Y, use this proportion, i.e., 
 6: b+a :: Y+R: L+R 
 or Part :\\liole:: Part :\\liole 
 Hence — 
 
 b Y+bR+a Y+aR=bL+bR 
 
 Y{(i+b)=bL+bR-aR-bR: -bR and +bR canca], 
 Then— 
 
 Y{a-\-b)=bL-aR -Mid Y=^^~^^ 
 a -\- b 
 
 Wlien— 
 
 a=b, then Y=a ^^~^^ hence Y=^~^ 
 2a 2 
 
 A simple inspection of the preceding diagram show.s these formulae to be 
 correct. 
 
 Wlien tlie break is of tlie .second or tliird Ivind, under Class I, it is usually 
 indicated by more or less rapid polarization wlien the copper or carbon pole 
 is put to line ; that is, by a rise of resistance. The fact that it is a break is 
 indicated by the cessation of even feeble signals from tlie distant station. 
 Sudden variations or jumps of resistance when the battery is applied indicates 
 that the conductor is only partially exposed, or that it is deeply buried in mud 
 or sand, thus preventing free escape of the gases liberated by electrolysis. 
 
 One of the successful methods of testing through tlie exposed end of the 
 conductor at a total break and obtaining the copper resistance up to the break 
 is that devised by Prof. Kennelly. This method of eliminating the resistance 
 of the exposed end itself depends upon the fact that the resistance of the fault 
 varies inversely as the square root of the current strength passing through it, 
 provided the exposure is not less than half of a square centimeter. 
 
 Supposing the current througli the break be increased four times, the apparent 
 resistance will be decreased one-half, for V4=2 and inversely is 1/2. The 
 strength of the current should in no case, however, exceed 25 milliamperes. 
 The measurements should be made by the false zero metliod, using zinc (nega- 
 tive current) to line. 
 
 The usual arrangement of the Wheatstone bridge for copper resistance is 
 made. See simplitied diagram for conductor resistance measurements, figure 
 11-38, and diagram of test sets at cable ofhces, Washington-Alaska system, tigure 
 11-35. If X be tlie resistance up to the break, A the resistance obtained by meas- 
 urement with, say, 4 milliamperes, B with IG milliamperes being four times as 
 many as with A, then, using Kennelly two-current false zero formula, 
 Let X=resistance of the cable to the break, 
 Let y'=resistance of tlie fault. 
 Then— 
 
 A=X+Y, 
 
 B=X+1/2T (multiply both memliers by 2). 
 
 We have- 
 
 2B=2X-\-Y, subtracting first equation. 
 
 A=X+Y. 
 
 2B — A^=X, the reistance of the cable to the break. 
 
 (495)
 
 60 
 
 Signal Corps Manual No. 3. — Chapter 11. 
 
 For example, if the measurement with 4 milliamperes gave 1.650 ohms, and 
 with 16 milliamperes 1,560 ohms, the resistance up to the break is 1,560X2 — 
 1.650=1,470 t)lims. Greater exactness can be secured by taking the exact ratio 
 of currents going to line by inserting a milliammeter between the bridge and the 
 cable. These ratios can be inserted in the general formuhx. For this fornmla 
 and the general discussion of the method, reference is made to tlie works cited 
 at the beginning of this chapter. 
 
 ig. 11-38. — LONG SUBMARINE CABLES, TESTING, LOCATION OF GROUND, PROFES- 
 SOR KENNELLY'S METHOD, COPPER RESISTANCE CONNECTIONS. 
 
 Simplicity is a large factor in tlie rapid work necessax\v on a cable sliip, and 
 it has been found by experience that tests based on a variation of currents, with 
 resultant effects on the resistance of the fault, are the best. The Jona curve 
 is based on variations of current ; the regularity of the curve shows tlie depend- 
 ence to be placed on the tests; the tests have the advantage of scale zero; 
 besides, data are furnished for solving a number of other scale-zero fornuilje if it 
 is .so desired. 
 
 Testing in a jar of sea water on a desk, with every advantage and no earth 
 currents, will show how difficult it is to locate faults with absolute accuracy. 
 
 Ab.solutely accurate locations of faults also can not be made on account of the 
 following: Errors made in location of cabl(> when it is originally laid in the open 
 sea ; didiculty in calculating for the extra slack cable i)ai<l out when the cable is 
 in process of laying. 
 
 In general, the location of faults of Class III presents the greatest diffi- 
 culty. Of course, if a second and .sound cable or another sound core in same 
 cable joining the two places is available, the distant ends are looited, and 
 the reliable " h>op test " may be used. 
 
 And when the exposure of the conductor is considerable, making the fault 
 resistance so low that not any or barely perceptible signals can be obtained 
 from the distant stiition, .Tonsi curve and forninl:r, based on Jona curve, scale 
 zi'i-d diita may he niijilicd, tlic distiiiit end being insulated. 
 
 (490)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 
 
 01 
 
 No other very sat isfju'tory inetliod exists of locating leaks (escapes) on 
 cables when facilities exist for taking; measurements at one end only. 
 
 CLAUK S I'OTKNTIAr. TEST. 
 
 [Sep Haines" Manual.] 
 
 This depends on the principle that in any circuit with resistance.s in series 
 tlie fall of potential at any point is proportional to the resistance passed 
 over, befrinninj; at, the hifih potential terminal. The instruments required at 
 the main station are a delicate galvanometer, high resistance Tip to 1(X),OUO 
 ohms, a Weston voltmeter, and a box of standard coils. The Wheatstoiie 
 bridge will answer for the latter. 
 
 Cable 
 
 — <HjmmHUHnmuh 
 
 HR 
 
 Fig. n-39.— LONG SUBMARINE CABLES, TESTING, LOCATION OF GROUND. 
 CLARK'S POTENTIAL TEST, CONNECTIONS. 
 
 At the far station the box of standard coils is not required. However, it 
 is better for each to be the main station in turn and compare results. 
 The comiections at the main station are as shown in figure 11-39. 
 The connections at the distant station are as shown in figure 11^0. 
 
 Coble 
 
 ^ 
 
 o 
 
 HR 
 
 1 T 
 
 Fig. 11-40.— LONG SUBMARINE CABLES, TESTING, LOCATION OF GROUND, CLARK'S 
 POTENTIAL TEST, CONNECTIONS AT DISTANT STATION. 
 
 Before closing the circuit the voltage of the battery B is determined with 
 the Weston voltmeter, cell by cell, so the low reading scale may be used and 
 the sum of these voltages taken. ^C is the box of standard coils, which should 
 be at first unplugged to a resistance approximately equal to one-half that 
 of the cable. 
 
 The galvanometer G and high resistance ER are connected in series, as shown. 
 The number of cells and UR should be proportioned as to give nearly a full scale 
 
 (497j
 
 62 Signal Corps Manual No. 3.— Chapter II. 
 
 reading when the galvanometer is connected with J.. First take a reading at both 
 stations with G connected ^^ith A and line open at C. This deflection will corre- 
 spond to the total battery voltage as shown by the sum of readings of the voltmeter. 
 
 Suppose the total number of volts is P and the deflection is D; then — will give the 
 
 number of divisions of the scale corresponding to one volt. 
 
 Now, disconnect batteries and connect the galvanometer.s with the line at 
 each station and observe the deflections due to eartli current (E. C), both in 
 directiwi and amount. 
 
 The main station then connects battery, standard coils, and cable, as shown 
 in figure 11-39, and, having arranged time with distant station, they talie the 
 following readings, as nearly together as possible: 
 
 Main station takes readings, first, with G connected with A, and then with 
 G connected with C. Distant station witli switch turned to C simply reads 
 deflection and reports it to main station. All readings are reduced to volts. 
 
 These readings are designated as V, v. and v', respectively, v and v' are 
 then corrected for earth-current readings, adding the value of earth current if 
 it is against and subtracting if it is nnth the battery current. 
 
 The distant station then sends the corrected result to main station. The 
 formula for the solution is as follows : 
 
 a?=resistance from main station to fault. 
 ■i?=number of ohms unplugged at AC. 
 
 R:V—r::X:v—v'. 
 
 For example, suppose the total voltage of battery in figure 11-39 were 11.2, and 
 that the galvanometer through the high resistance gave a deflection of 273, then 
 
 ^= =24.4 scale divisions per volt. In like manner distant station determines 
 
 the value of his deflections. Suppose it is 27 divisions per volt. Earth current gives 
 18 divisions against direction of testing current at both stations. 
 
 Now, suppose V is 265 divisions, v 193 divisions, and v' 65 divisions. 
 
 i2=800 ohms. 
 
 These would correspond, respectively, to 
 
 18 
 -: — =.74 E.G. volts at main station 
 24.4 
 
 1 Q 
 
 i^=.67 E.G. volts at distant station 
 27 
 
 |?^=10.9 volts V 
 24.4 
 
 —=7.9 volts V 
 24.4 
 
 — =1.4 volts v' 
 27 
 
 7.9+.74=8.64 corrected v 
 1.4-f .67=2.07 corrected v' 
 
 Substituting in formula 
 
 ^^ 800(8.64-2 ^7)^5256^^3^, ,,,^^^ 
 10.9-8.64 2.26 
 
 2325 
 
 If the rcsiHtance of tlu; cable is 8.5 ohms |)cr nautical mile, the fault is -——=273.5 
 
 8.5 
 
 tnilea distant from main station. 
 
 (498)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 63 
 
 More accuracy would probably be reached by repeating the test, using a -new 
 value of R approximating to x, as found above. 
 
 One great advantage of the Clark test is that, as readings at the two ends 
 may be made practically simultaneously, errors due to irregular polarization 
 and earth currents are eliminated. 
 
 EARTH OVERLAP TEST. 
 
 Where both stations are equi]»iied with full sets of instruments one of the 
 best metho'ls of localizing faults due to defects in insulation is called the earth 
 overlap test. It is particularly applicable to high-resistance faults. 
 
 In effect the measurements are made with a view to determining how nmch 
 resistance should be put in at the station nearest to the fault in order to 
 make the resistances on each side of the fault ccjual. 
 
 A y X B r C 
 
 Fig. 11-41.— LONG SUBMARINE CABLES, TESTING. LOCATION OF GROUND, EARTH 
 OVERLAP TEST, DIAGRAMMATIC. 
 
 The measurements are made by the observers alternating in measuring line 
 resistance with distant station earthed, each allowing a specified number of 
 minutes, say three, for each station's tests. Both should measure in the same 
 way — that is, either with the false zero with zinc to line or with reversals. 
 Both use the same number of cells testing battery. 
 
 Let AB be a cable with a fault in it at z (tig. 11-41). Suppose the copper 
 resistance of the cable when sound to be known having a value, L, and the 
 fault occurs at distance x from B. 
 
 If tests are made at the end B, it is evident that when a resistance r is in- 
 serted, making a'+r=y, then the following equations result: 
 
 x-\-y=^L; x-\-r=y 
 y=L—x 
 
 1 T L—r 
 
 :.oc-\-r=L — x;x=^—- 
 
 L — r 
 
 or substitute first value of y in first equation; when x-\-x-Tr=L :.2x=L — r; 3^=— ., > 
 
 same as before. 
 
 The routine is as follows: B tests first and gets, say. 2.500 ohms, then .1 
 gets 3,000 ohms. They exchange results. B now inserts a resistance which 
 should be greater at first than the difference between the results, owing to 
 resistance at the fault. 
 
 For example, B inserts 1,000 ohms and tests three minutes with .1 earthed. 
 He then earths through the inserted resistance for three minutes and -1 tests. 
 
 They then compare results, the last at B and first at A being considered 
 most reliable. 
 
 B now gets 3.800 ohms and .1 3.500, so 1.000 ohms is too much. B inserts 
 600, 800. 650. 7tK), and 670 ohms in succession, going alternately too low or too 
 high until at 670 both B and .1 get a mean result practically identical or about 
 3,500 ohms. 
 
 (499)
 
 64 Signal Corps Manual No. 3. — Chapter 1 1 . 
 
 It is found better to go alternately too low and too high rather than twice on 
 the same side. Also it is recommended that when nearly the same at both ends 
 measurements should be repeated to check errors. 
 
 Supposing the resistance of the cable when sound (L) to be 4,500 ohms, then by 
 
 L — r 
 the formula — tt^—^ 
 
 ^555^1^=1,915 ohms from B to the fault. 
 
 For further information concerning this test refer to Jordan's and Schonau's 
 inoditication of Keuneley's and Anderson's earth-overlap test in " Handy For- 
 mulae for Testing Submarine Cable for Breaks, Dead Grounds and Earth Over- 
 lap," appearing later in this chapter. Also see " Beginners' Manual of Sub- 
 marine (Jal)le," by Baines, page 132. 
 
 The advantage of testing by varying the current is that there need be no 
 cooperation between distant stations ; the testing is done by one man, while 
 Clark's potential test and the earth-overlap tests require cooperation between 
 stations, with possibility of delay and disagreement, unless well arranged for 
 before undertaken. 
 
 However, the Clark's potential and the earth-overlap tests are particularly 
 applicable to locating high-resistance faults, through which it would be im- 
 possible or impracticable to force enough current to vary sutticiently to form a 
 Jona curve, or ai»ply to formuhe using .similar data. 
 
 Should the cable have more than one fault, the result foinid will lie somewhere 
 between the t\V(» actual faults and nearer Id the fault wilh Ihe least resistance. 
 This remark applies to all tests. 
 
 HAXDY t'OKMULAE FOR TIOSTING Sl'BMARINE CABLE 1 Oli BREAKS, DEAD GROUNDS, 
 
 AND EARTH OVERLAP. 
 
 Location of cable faults can not be definitely made where there is not a 
 metallic circuit. Where part of the testing cm-rent passes through water, de- 
 composition takes place at the fault and the resistance of the fault is con- 
 stantly chiinging. 
 
 It has been found by practice that the resistance of such a fault varies 
 inversely as the square root of the testing current, provided the exposed 
 surface of tlie contluctor be not less than one-half of a square centimeter, 
 and the testing current does not exceed 24 milliamperes. 
 
 SCALE ZERO. 
 
 [Not metallic circuit.] 
 
 No. 1, Jona curve (see curve sheet fig. 11-42). Preferable to use exact num- 
 ber milliamperes, as printed on left-hand edge of sheet. 
 
 Tln' .Jona curve is based on variations of current; the regularity of the 
 curve shows tlie dependence to be placed on the tests. The scale zero is 
 u.sed. The data may also be used for solving other scale zero fornmlse. The 
 regularity of the curve is very imi)ortant. I'sually the other formuliie using 
 this data means nnich increased work, witii little additional advantage. (See 
 the actual test shown below.) 
 
 From the measurements for the above Jona curve, scale zero, 2 to 24 
 milliamperes, the following formulae can be worked out and used for check- 
 ing puri)oses, (tr in deriving a mean result. 
 
 For nrdformity, tlie designations below of (7— current and i2= resistance, 
 and tlieir relations to each othei- should he maintained. 
 
 (500)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 1 1 . 
 
 65 
 
 I 
 
 ('i = lo\vest current=hiKlu'st resistance=/23 
 
 C2= intermediate ourreut=iiiteriMeiliate resistance— II2 
 
 C3=liif?liest i-urrent=lo\vest resistance=72i 
 
 No. 2. (Mann's trii)U>-tost (p. 00, Barkers Hanrlbook, 1903) : 
 
 r, C, Cz 
 
 Current ratio : 1:2:4 — Scale zero. 
 
 Hi Hi R\ 
 
 X=Ri-\-R—IU 
 
 Note. — Can iret six ciiiculMlifins Irom .Toiia measurements for \\w i)racti('al 
 
 (ests ai)pen(le(I iiereto. 
 
 Usin.u- Ma Ma. Ma 
 
 2, 4 juul S 
 
 3, 6 and 12 
 
 4, 8 and 16 
 
 5, 10 and 20 
 
 6, 12 and 24 
 
 8, IG and 82 approximating: for 32. 
 
 No. 3. Rynier-.Toncs dual test, modification of Cann's (p. 01, liarker's Hand- 
 l)ook, 1003). 
 
 Turrent ratio: 1 : 2 —scale zero. 
 R, R, 
 A'=2.5576 i?i-1.5576 R^ 
 Note. — Can ,iret eiijlit calculations, hut tlie two lowest are too small ; po.ssibly 
 only one lowest too snuill. See practical test annexed. 
 
 Jsin,^ Ma. Ma 
 
 
 Using Ma. Ma. 
 
 
 2 and 4 
 
 
 6 and 12 
 
 
 3 and G 
 
 
 8 and 16 
 
 
 4 and 8 
 
 
 10 and 20 
 
 
 5 and 10 
 
 
 12 and 24 
 
 
 For 
 
 tise in Rymer-.I 
 
 mes dual cable test. 
 
 
 1X15,576 equals 
 
 15.576 
 
 1X25.576 equals 
 
 25.576 
 
 2X15.576 equals 
 
 31,152 
 
 2X25.576 equals 
 
 51.152 
 
 3X15.576 equals 
 
 46,728 
 
 3X25,576 equals 
 
 76.728 
 
 4X15.576 equals 
 
 62.304 
 
 4X25,576 equals 
 
 102,304 
 
 5X15,576 equals 
 
 77,880 
 
 5X25,576 equals 
 
 127,880 
 
 6X15,576 equals 
 
 93.4r.(i 
 
 6X25,576 equals 
 
 153,456 
 
 7X15,576 equals 
 
 109,032 
 
 7X25,576 equals 
 
 179.032 
 
 8X15,576 equals 
 
 124,608 
 
 8X25,576 equals 
 
 204,CR)8 
 
 9X15.576 equals 
 
 140,184 
 
 9X25.576 equals 
 
 230,184 
 
 No. 4. Kennelly (p. (il, I'.arker's Handbook, 1903). 
 
 (\ c, c. 
 
 Current radio: 1: 4:9 —scale zero. 
 
 Rs ^2 lii 
 
 A'=:?i±^'-4(/?3-i?,) 
 
 Note. — Two calculalion.s, approximate for 27 and 18 milliamperes. 
 
 (^3 ma. : 12 ma. : 27 ma.-i 
 
 [2 ma, : 8 ma.' : IS ma.j 
 See practical tests appended hereto. 
 
 (501)
 
 66 
 
 Signal Corps Manual No. 3. — Chapter II. 
 
 No. 
 
 5. Keunelly. Ps 
 
 ge 62, 
 
 Barker's Handbook, 1903. 
 
 Cy 
 
 C, 
 
 Cs 
 
 Current ratio: 1 
 
 : 4 : 
 
 16 —scale zero. 
 
 Rz 
 
 i?2 
 
 ^1 
 
 Note. — This test not limited to 25 milliamperes, according to Kennelly. 
 Note. — Two calculations, approximate for 32 and 48 milliamperes. 
 
 2 ma. : 3 ma. : 32 ma.) o t^- i 4- < i 
 
 ^ > See practical tests annexed. 
 
 3 ma. : 12 ma. : 43 ma. J 
 
 Note for approximating.— It is noticed that the difference between readings 
 grows less as ma. increases; also that 12, 16, 20, 24 differ by 4; hence, 32 
 greater by two periods of 4 than 24 which is measured. 
 
 Also, that 48 is greater by 6 periods of 4 than 24 which is measured. 
 
 Diminish the difference between fours as they increase, being guitled by the 
 differences measured between 12 and 24. 
 
 Heavy solid black curve shows estimated 96 ohms; heavy dotted black curve 
 shows that it should have been 103 ohms. Fine solid curve shows estimated 
 curve, 196 ohms ; tine dotted curve shows that it should have been 203 ohms. 
 
 708090100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 
 
 OOQOOOOOOOQOOOOQ 
 
 OHMS O 
 
 S Ig 
 
 Fig. 11-42.— LONG SUBMARINE CABLES, TESTING, CURVE SHEET FOR JONA AND 
 
 OTHER GRAPHS. 
 
 (602)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 67 
 
 Two Actual Laboratory Tests, One With 103 Ohms in CiBcmT, the Other 
 With 202 Ohms in Circuit, Ends Terminating in Glass Jar Filled With 
 Sea Water, Exposure ok Ends Being : 102 Ohms, J Inch ; and 203 Ohms, 
 Copper Flush With Insulation. 
 
 [100 ohms in rheostat — 2 milameters 3 ohms^l03 ohms in circuit.] 
 
 Measnrements. 
 
 [One-half inch core exposure. Scale zero.] 
 
 actual test. 
 
 Milliamperes. 
 
 Ohms. 
 
 24 
 
 
 
 144 
 
 20 
 
 
 
 1.50 
 
 10 
 
 
 
 158 
 
 12 
 
 
 
 171 
 
 10 
 
 
 
 164 
 
 8 
 
 
 
 193 
 
 6 
 
 
 
 21.5 
 
 5 
 
 
 
 233 
 
 4 
 
 
 
 2.55 
 
 3 
 
 
 
 299 
 
 o 
 
 
 
 384 
 
 
 C 
 
 atriit 
 
 \ fit ions. 
 
 CANN S TRIPLE TEST. 
 Scale zero. 
 109 
 110 
 112 
 109 
 105 
 80 
 
 6)631 
 
 Average- 105.2 ohms. 
 
 RYMER-.IONES DUAL TEST. 
 Scale zero. 
 
 102 
 
 97.1 
 103.5 
 102.5 
 107.5 
 
 96.4 
 
 (84) excluikHl 
 (54) excluded 
 
 kennelly's. 
 
 Scale zero. 
 
 1:4:9 milliamperes, ratio of. 
 Can get 2 calculations. 
 3 ma. : 12 ma. : 27 ma.=100 ohms. 
 2 ma. : 8 ma. : 18 ma. = 108.5 ohms. 
 
 2)208.5 ohms. 
 Average 104.2 ohms. 
 
 0)409.0 
 Average- 101.5 oliins. 
 
 Highest. 
 Lowest-. 
 
 112 
 
 ohms. Highest - 107.5 ohms, 
 ohms. 1^0 west 96.4 ohms. 
 
 2) 203.9 ohms. 
 
 2)198 ohms. 
 Average- 99 ohms. Average- 101.9 ohms. 
 
 Note. — See curve slieel lor ,Jona curve. 
 
 kennelly's. 
 Scale zero. 
 
 1 : 4 : 16 milliamperes, ratio of. 
 Get two calculations. 
 2ma. : 8 ma. : 32 ma. = 110 ohms. 
 3 ma. : 12 ma. : 48 ma. =106 ohms. 
 
 Average 
 
 2)210 
 . 108 
 
 ohms. 
 
 (503)
 
 68 Signal Corps Manual No. 3. — Chapter II. 
 
 General average of all the lOS-ohin test, scale zero. 
 
 105.2 
 
 99.0 
 101.5 
 101.9 
 104.2 
 108.0 
 
 96.0 Joua curve. 
 
 7)715.8 
 General average- 102.2 ohms. 
 
 Second test : 200 ohms in rheostat— 2 milliamperes 3 uhms=203 ohms in 
 circuit. 
 
 
 Mcusurcimnt 
 
 s. 
 
 [Core flush. 
 
 Scale 
 
 zero.] 
 
 
 ACTUAL 
 
 TEST. 
 
 Milliamperes. 
 
 
 Ohms. 
 
 24 
 
 
 
 270.6 
 
 20 
 
 
 
 278.6 
 
 16 
 
 
 
 292.6 
 
 12 
 
 
 
 316.8 
 
 10 
 
 
 
 330.0 
 
 8 
 
 
 
 350.0 
 
 6 
 
 
 
 388.3 
 
 5 
 
 
 
 420.5 
 
 4 
 
 
 
 455.6 
 
 3 
 
 
 
 512.4 
 
 2 
 
 
 
 640.0 
 
 Calculations. 
 [liOo ohms circuit.] 
 
 CANN S TRIPLE TEST. 
 
 UYMEK-.IONES DUAL TEST. 
 
 Scali' zero. 
 
 
 ■5cali" zero. 
 
 215 
 
 
 199 
 
 203 
 
 
 199.5 
 
 211 
 
 
 206.7 
 
 216 
 
 
 206.4 
 
 204 
 
 
 190 
 
 209 
 
 
 185 
 
 6)1,2.58 
 Average- 209.7 ohms. 
 
 195 
 (169.4) excluded 
 
 IIiRhest-216 
 
 7)1.381.6 
 
 Lowest— 203 
 
 Average 
 
 . 197.4 ohms. 
 
 2)419 
 
 Highest 
 
 .206.7 
 
 Avernpo- 209.5 f>hnis. 
 
 Lowest - 
 
 2 
 
 _185 
 
 
 )391.7 
 
 
 Average 
 
 . 195.8 ohms. 
 
 Note. — See curve 
 
 ■^liccl for 
 
 .Tona curve, 196 
 (504) 
 
 KENNELEYS. 
 
 Scale '/.( ro. 
 
 1:4:9: millianiperos. ratio of. 
 Can get 2 calculations only. 
 3 ma. : 12 ma. : 27 ma. =181.5 ohms. 
 2 ma. : 8 ma. : 18 ma. =202.5 ohms. 
 
 2)384 
 Average 192 ohms. 
 
 KENNELEYS. 
 Scale zero. 
 1 : 4 : 16 : milliamperes. ratio of. 
 Can get 2 calculations only. 
 2ma. : 8 ma. : 32 ma. =207 ohms. 
 3 ma. : 12 ma. : 48 ma. =213.2 ohms. 
 
 2) 420.2 
 
 Average 210.1 ohms. 
 
 ohms.
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter 11. 69 
 
 General average of all the .iOJ-ohin test. 
 
 209. 7 
 
 209.5 
 
 197.4 
 
 . 195.8 
 
 196.0 Jona curve. 
 
 192.0 
 
 210.1 
 
 7)1,410..- 
 
 201.5 ;j;t'iK'rul average. 
 203.0 uhnis exact. 
 Krror, 2.5 olinis. 
 
 Refer to the .Tona curve sheet, where IG mil amperes are used: Then V16=4; 
 iiiv<M-s(>I.v 1=0.25, whicli will he found opposite 10 on right-hand side (tf curve 
 sheet, indicating that tlie resistance of tlie fault lias heen reduced to xVo <^i itself. 
 
 Again, where 4 mil amperes are used: v'4=2; inversely 2=0.50, which will 
 be found on right-hand side of the curve sheet opposite 4, which shows the 
 resistance of tlie fault has been reduced to Ts^oi. itself. 
 
 It will again he observed by noting the curve that as the tests approach 24 
 mil amperes tlic resistance which is .sought is reduced. 
 
 Solicitude for the safety of the instruments and cable, together with exjie- 
 rience. has shown that 24 mil amperes should not be exceeded. 
 
 Casual observation of the fine current lines on the .lona curve sheet, together 
 with knowledge of tlie direction of the curve, shows that after 24 mil amperes 
 are jiassed the line solid and dotted lines are close together, even though the 
 differences are 8, as comiiared with differences of 4 between 24 and 12, and 2 
 between 12 and 6, and 1 between 6 and 2, while the curve itself is more perpen- 
 dicular, with a consequent decrease in the rate at which the resistance is being 
 reduced. 
 
 The above shows that after passing 24 very great increase in current is neces- 
 sary to produce a small decrease in resistance. Hence, the curve below 24 on 
 the sheet is approximated as being the most practicable. 
 
 Referring to the numbers on the right-hand side of the curve sheet, which 
 are the results of 1 divided by the square root of milliamperes used, it will be 
 found that they Increase from the bottom to the top of the page, and that the 
 distance apart is regular, while the distance apart of the tine current lines is 
 irregular. 
 
 To eliminate all resistance in the fjuilt would require an infinitely large cur- 
 rent, as the resistance of the fault is proportional to the numliers on right-hand 
 side of the curve sheet, i. e., no resistance on the bottom line, increasing to 0.70 
 of the full resistance of the fault at 2 milliamperes. 
 
 (505»
 
 70 Signal Corps Manual No. 3.— Chapter 11. 
 
 Taking the two examples noted above and deducing from percentage of fault 
 to mil amperes necessary — 
 
 Let A'=milliamperes necessary. 
 
 Then: .50=i ••• -50 V^=l -•• V^=4t=2 
 ■yjx -50 
 
 -^ X =2, squaring both members^ x=4 agreeing with numbers as printed on curve 
 sheet. 
 
 Again: .25=-7= .". .2b^jx=\ :. V ^ ~~9K~'^ 
 
 ■y/x=4, then by squaring both members .r=16. 
 
 Using the experience thus gained we know that .00=-^ or the milliamperes would 
 
 have to be infinitely great to produce no resistance in the fault. 
 
 By way of comparison, however, we can find out the milliamperes necessary to 
 reduce the resistance of fault to a very low finite quantity. 
 
 Question : Ho\\' much current is necessary to reduce resistance of fault to .001 
 of itself V 
 
 .001= , .-. . 001-^^=1 .-. ^/^= =1000 
 
 ■s/x " ^ .001 
 
 Va-=1000, .1 = 1,000,000 milliamperes, which is, of course, impracticable. 
 
 Tlie above calculations in practice would be considerably upset, for a strong 
 negative current, which is the current mostly used, would insulate or tend to 
 insulate the exposed surface by covering it with liydrogen gas, for the stronger 
 tbe current the more hydrogen is released. If positive current is used tlie 
 copper is decomposed and the exposed end is covered with a cuprous or copper 
 powder which, as well as the hydrogen, has an insulating effect; hydrogen gas, 
 however, being more volatile escapes more easily except when formed in a very 
 small aperture sealing it, in which ca.se it is sometimes necessary to use the 
 positive current to clear off the hydrogen. 
 
 Very small exposures sometimes are highly insulated by globules of hydrogen 
 gas, using the negative current. In such a case, a very strong current would 
 burn out the fault, after which a weaker current could be used for testing. 
 
 Current used should not exceed 24 milliamperes and in case of higli resistance 
 faults this could be obtained M'ith the limit of 40 volts. These limitations are 
 necessary for the safety of the cable. 
 
 HANDY FORMULA FOR TESTING SUBMARINE CAHLK FOR 1U5FAKS OR np;AI) GROUNDS. 
 
 [Not metallic circuit.] 
 
 No. C. I'age i;?2 Raines Begiinier's Manual, second edition; page 145 
 Fislier & Darby, tliird edition, for Jordan and Sclionau's modification, of 
 Kenneley's and Anderson's earth overlap test. 
 
 The plain earth overlap test lias been i)reviously (>xi)lMin(Ml in (bis chapter. 
 
 Tests are taken by each station under similar conditions or bridge ratio, 
 battery power, etc., until preconcerted number of observatioius have been 
 completed. 
 
 (506)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 71 
 
 atationH Nioiihrrcd 1 and 2. 
 
 [First operation — I'roliminary tost.] 
 
 Station 2 cable ffroundod. 
 Station 1 nieasun' rosistancc (R). 
 Station 1 ciihle firounded. 
 Station 2 measure resistance (li'). 
 
 I Second operation.] 
 
 Stalioii 1 niipliii,' in liridtje R + R\ 
 
 Station 2 uiii)hm in l)ridKe R + R^. 
 
 Station 1 in.sert resistance=A'' Ijetwccn liri(l;:(' jiiid calilc — call i1 (?•). 
 
 Station 2 insert resistance^A' l)et\V(-en i)ri(i;:(" and cable— call it (r'). 
 
 I'I'liird operation — I-'or test, j 
 
 Stalion 2 ground cal)le, leaving; /•' in circuit. 
 
 Station 1 obtain balance in bridge by increasing or decreasinu tlic value of r. 
 
 Station 1 ground cable, leaving r in circuit. 
 
 Station 2 obtain balance in bridge by increasing or decreasing the value of i-'. 
 
 This operation to be repeated alternately by stations ] and 2 until balance 
 is obtained without having to make furl her changes in resistance r or /•'. 
 Then the resistance to the fault from station 1 is — 
 
 L+r^-r 
 
 and from station 2: 
 
 L+r-r' 
 
 =ohms to fault. 
 
 =ohms to fault. 
 
 2 
 
 />=length of perfect cable in ohms. 
 
 The sum of these two results should equal the C. R. of the perfect cable. 
 
 For the purpo.se of checking the battery, which should be the same at both 
 ends of the cable, a milliamineter should be inserted in the cable and the read- 
 ings taken, and when the fault has been electrically placed in the center of 
 the cable the readings of the milliammeters at both ends of the cable should 
 be the same. 
 
 JORDAN AND SCHONAU'S MODIFICATION. 
 
 For a continuation of the foregiting tests, another series was taken to a 
 diminished resistance in C. The inserted resistance r at station 1 being the 
 lowest, viz, 4.124 ohms, each end could be reduced 4,000 ohms in C (arm of 
 bridge, .see diagram). The amount therefore in (', at both stations, to which 
 balance would be obtained by the respective adjustments of r and /•* was 
 made 5,810 ohms. 
 
 It will be seen from the following res\dts that r and /•' were proportionately 
 diminished! 
 
 Station 1. Station 2. 
 
 1st test, r IfiG r', 1..3.34 
 
 2d test, r 162 r', 1,334 
 
 3d test, r 162 rK 1,3.34 
 
 4th test, r 162 r', 1,334 
 
 46581°— 17 33 (507)
 
 72 Signal Corps Manual No. 3. — Chapter 11, 
 
 The resistance to the fault from station 1 is: 
 
 and from station 2: 
 
 8800+1334- 162 _^ 986 
 2 
 
 8,800+162- 1,334 _3 g^^ 
 
 which results are the same as those obtained wdth 9,810 ohms in C, for the first series 
 of tests. 
 
 4,986+3,814= ohms total 8,800 
 
 EIXAMPLE OF JORDAN ANDSCHONAU5 MODIFICATION 
 
 Ahnjltdevdapedinacahkcf 88CO ohms when perfecl-. Per ttshcalnabon 20 LccJandK cfJi^ ■ 
 
 FIRST OPERATION 
 
 Preliminary Test 
 
 i at ojcS staOon and a badge rata of tCOO/lOOO 
 
 H>i f^n 
 
 STATION 2 T T 
 
 I Ground \_ J^, 
 
 SECOND OPERATION 
 
 neifihurb'imcoppemsjsianc^s.a^urifa ttbt i&iO ohm\^¥i^s unplugged m hofh bndaf i) 
 
 jgr-FTCi 
 
 Fig. 11-43.— LONG SUBMARINE CABLES, TESTING, JORDAN AND SCHONAU'S MODI- 
 FICATION OF EARTH OVERLAP TEST, DIAGRAM OF CONNECTIONS. 
 
 INSTRUCTIONS FOR SHORE STATIONS DX'RING LAYING OR KEP.MR OF CABLE. 
 
 Instructions will be given to look out for .ship's call at a specified time. 
 CJonnect up for receiving, and keep close watch in order to answer promptly. 
 
 Ship will give instructions regarding nece.ssary connections. These instruc- 
 tions must he implicitly obeyed, and with rigid accuracy as to time. 
 
 Timer)ieces are to be set according to ship's instructions, and frequent com- 
 parisons with ship's time made in case timepiece is not regular. 
 
 Instructions to " free the end of the cable for so many minutes " would be 
 
 abbreviated " Free min." During this period especial care must be taken 
 
 that the end is well insulated, and on no account must the c(mductor Vie per- 
 mitted to touch anything. 
 
 Instructions t<i " Karth (ground) the ciililc for so many niiiuitcs " will be 
 
 al)brcviated " Karth min." The end of the conductor, or its binding screw, 
 
 will then Im' directly and secuicly connected to the cable armor for the time 
 specified. 
 
 (508)
 
 Long Submarine Cables, Telegraphy, and Tests. — Chapter II. 73 
 
 After each orcter is executed for the time .specified, connect up for receiving 
 jind await next order. Should no communication come from the ship after 
 15 minutes, begi^i at the hour and free the cable for 15 minutes, then earth 
 f<»r 15 minutes, then connect up U>v receiving during the remaining half hour. 
 (Continue this routine every hmii- until connnunlcation is restored, or twelve 
 hours has elapsed. If there is still no communication, connect up for receiving 
 and keep close watch for ship's call. 
 
 In a book at the station will be kept a complete record of all changes in 
 connections made and instructions received during laying and repairs and 
 the exact time each was made. This record must be signeil by the man on duty, 
 with note of time he has been relieved. He will at the same time call atten- 
 tion of the one relieving him to any written note of instructions he has received 
 from the ship. 
 
 Strict obedience to the foregoing instructions is enjoined. 
 
 Ahifskan cnblc data. 
 [Weight of 1903 tjTe.] 
 
 AMiole cable in air (per knot ) .• 
 
 Whole cable in air (per mile ) 
 
 Whole cable in water (per knot) 
 
 Whole cable in water (per mile) 
 
 MATERI.\LS. 
 
 Iron wire (per knot ) 
 
 Iron wire (per mile) 
 
 Jute and compound (per knot) 
 
 Jute and compound (per mile) 
 
 Tape (per knol ) 
 
 Tape (per mile) 
 
 Rul)ber (per knot) 
 
 Rubber (per mile) 
 
 Copper (per knot ) 
 
 Copper (per mile) 
 
 Diameters inch . . 
 
 C. R. at60° F. (per mile) ohms.. 
 
 D. R. at 60° F. (per mile) megs.. 
 
 Capacity (per mne) m. f . . 
 
 C. R . at 60° F. (per knot ) ohms. . 
 
 D. R. at 60° F. (per knot) megs. . 
 
 Capacity (per knot) m. f . . 
 
 Breaking strain 
 
 Elastic strain 
 
 Deep 
 sea. 
 
 Interme- 
 diate. 
 
 S. E. 
 
 Pounds. 
 3,605 
 3,127 
 2,328 
 2,019 
 
 2,359 
 
 2,046 
 
 888 
 
 770 
 
 66 
 
 Pounds. 
 
 6,787 
 5,887 
 4,812 
 4,174 
 
 5,083 
 4,409 
 1,341 
 1,163 
 
 Pounds 
 21,620 
 
 18,800 
 
 57 
 
 
 
 177 
 
 
 
 153 
 
 
 
 132 
 
 
 
 115 
 
 
 
 .81 
 7.39 
 
 .98 
 
 1.75 
 
 1,418 
 
 
 
 .428 
 
 
 
 8.52 
 
 
 
 1,230 
 
 
 
 .493 
 
 
 
 14, 570 
 11,000 
 
 19,790 
 13,000 
 
 
 Note. — Alaskan tj-pe of 1904 has 215 pounds of rubber per knot. 
 
 Shore end is intermediate (11 No. 8 B. \V. G. wires) withanoulerarmorof 13No. SB. W. G. wires. 
 
 (509)
 
 74 Signal Corps Manual No. 3. — Chapter 11. 
 
 Weights (in pounds) siibnidrinc cable, Alaskan ti/pr, 1905. 
 
 Per mile. 
 
 Per naut. 
 mile. 
 
 Core: 
 
 Conductor 
 
 Pure Para 
 
 40 per cent compound. 
 Tape 
 
 Total. 
 
 Deep-sea cable: 
 
 Core 
 
 Armor (16 No. i;3 B. W. G. wires). 
 Jute, tar compound, and cutch 
 
 Total 
 
 Weight in water. 
 
 Intermediate cable: 
 
 Core 
 
 Armor (11 No. 8 B. W. G. wires). 
 Jute, tar compound, and cutch. . . 
 
 Total 
 
 Weight in water . 
 
 Shore-end cable: 
 
 Core 
 
 Armor(flrst, 11 No. 8B. W. G.)... 
 Armor (second, 14 No. .3 B. W. G.). 
 Jute, tar compound, and cutch 
 
 Total 
 
 AVeightin water. 
 
 Specific gravity: 
 
 Pure Para 
 
 40 per cent compound. 
 
 Pounds. 
 122. 48 
 
 11.38 
 193. 31 
 
 71.00 
 
 39S. 17 
 
 398. 17 
 
 2, 232. 00 
 
 656. 00 
 
 3,286.17 
 2,098.00 
 
 398. 17 
 4,690.00 
 1, l:JS. 00 
 
 6,226.17 
 3,948.00 
 
 .398.17 
 4,690.00 
 13, 002. (X) 
 3,430.00 
 
 21,520.17 
 15, 192. 00 
 
 Pounds. 
 
 141.18 
 
 13.10 
 
 222.60 
 
 81.75 
 
 458. 63 
 
 458. 63 
 
 2,570.00 
 
 755. 40 
 
 3,784.03 
 2,416.00 
 
 458.63 
 5, 400. 20 
 1,310.30 
 
 7, 169. 13 
 4,546.00 
 
 458. 63 
 5, 400. 20 
 14,972.00 
 3,949.00 
 
 24, 779. 83 
 17,495.00 
 
 .9250 
 1.5903 
 
 (510)
 
 INDEX. 
 
 REMARKS. 
 
 All those to whom this manual is issued are recjuested to observe that the index consists of three parts, 
 namely: Chapters, subjects, and ilUislrulions; and that to find a subject or illustration it is first necessary 
 to locate the chapter. This can be readily accomplished, as chapter numbers appear on each leaf of the 
 manual. 
 
 An alphaljetically arranged list of all Signal Corps apparatus and supplies appears in chapter 8, begin- 
 ning on page 1. 
 
 CHAPTER INDEX. 
 
 CHAPTER 1. 
 
 The Voltaic Cell, Ohms Law, and Primary anu Secondary Batteries. 
 
 CHAPTER 2. 
 
 Telegraphy' and the Induction Telegraph Set. 
 
 CHAPTER 3. 
 
 Telephony, the Camp Telephone, and the Buzzbr. 
 
 . CHAPTER 4. 
 
 Cable and Cable Systems. 
 
 CHAPTER 5. 
 
 Aerial Line Construction. 
 
 CHAPTER 6. 
 
 Post Telephone Systems. 
 
 chapter 7. 
 
 Small Arms Target Range Signaling Systems. 
 
 chapter 8. 
 
 Technical Equipment Issued by the Signal Corps. 
 
 CHAPTER 9. 
 
 Miscellaneous Tests and General Information. 
 
 CHAPTER 10. 
 
 Requisitions and General Maintenance Regulations. 
 
 chapter 11. 
 
 Long Submarine Cables; Submarine Telegraphy; Tests op Submarine Cables. 
 
 (511) 1
 
 I 
 
 SUBJECT INDEX. 
 
 Subjects. 
 
 A. 
 
 Accuraulation of sediment in storage batteries 
 
 Action of buzzer interrupter , 
 
 Adjustment of telegraph apparatus , 
 
 Aerial cal>le, installation of , 
 
 Aerial line construction: 
 
 Amounts of sag of aerial wires , 
 
 At crossings 
 
 Attaching guys to rook 
 
 Attaching guys to trees 
 
 Bracket lines 
 
 Cable box 
 
 Cable box ground, lapping for splices and sealing cable ends 
 
 Cable terminals, fused and unf used 
 
 Connect aerial line through fuses and Lightning arresters 
 
 Connecting aerial wires to cable 
 
 Crossing a road 
 
 Dimensions of cross-arms 
 
 Double arms 
 
 Drip loops 
 
 Employed at Front Royal, Va., Remount Depot 
 
 Erection of line, method of procediu^e 
 
 Fence post lines 
 
 Galvanized-iron wire, for guying light lines 
 
 Guard wires 
 
 Guy rods, deadman, thimbles 
 
 Guys and anchors 
 
 Guy stubs and anchor logs 
 
 Guy terminal cross-arm 
 
 Handling and hanging cable to messenger 
 
 Handling hard-drawn copper wire 
 
 In rolling country 
 
 Insulators 
 
 Lightning rods 
 
 Linemen not to use climbers on stepped poles 
 
 Long spans 
 
 Construction of saddles 
 
 River crossing at Ruby, Alaska 
 
 Terminating supports 
 
 Wire used 
 
 Yukon River crossings 
 
 Messenger strand — ■ 
 
 Amount of sag 
 
 Ending 
 
 Grading 
 
 Guying 
 
 Installing 
 
 Metal shims for 
 
 Properties of various sizes 
 
 Supports 
 
 Terminating 
 
 To splice 
 
 Turning a corner with 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (518) 8
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 Aerial line construction— Continued. 
 
 Poles, concrete, construction and dimensions 
 
 Poles, steel, use of 
 
 Poles, wood — 
 
 Delivery of 
 
 Depth to set in ground 
 
 Desired dimensions 
 
 Digging holes 
 
 In Alaska 
 
 Effect of treating 
 
 Framing 
 
 Location of gains 
 
 Grading 
 
 Line for aerial cable 
 
 Preparation of 
 
 Principal factor in treating 
 
 Setting 
 
 Sides to use for cross-arms 
 
 Species, etc 
 
 The pole brace and guy stub 
 
 Turning a right angle corner with two poles 
 
 Use of short stout poles 
 
 Porcelain-coated bridle rings for supporting bridle wire 
 
 Protection of aerial cable 
 
 River crossings 
 
 Self-supporting tripods 
 
 Size of guys to use 
 
 Splicing bridle wire to copper line wire 
 
 Stringing wire 
 
 Terminal or office pole ■. 
 
 Termination of line at buildings other than residences 
 
 Termination of line at residences 
 
 Test station 
 
 Transposition of metallic circuit 
 
 Tripod lines .- 
 
 Poles for, and erecting the tripods 
 
 Two methods of stringing wire • 
 
 Tying in copper, iron, and steel wire 
 
 Wire used for post telephone systems 
 
 Aeroplane tool chests and contents 
 
 Alaskan cable data 
 
 Alaskan lines: 
 
 Diggi iig pole holes 
 
 lioag spans 
 
 At Rul)y, Alaska 
 
 Construction of saddles 
 
 Terminating supports 
 
 Wire used 
 
 Yukon River crossing 
 
 ReIf-Hui)|)ort!ng tripods 
 
 Tri|)od lines 
 
 Alternating ( inrtMit 
 
 Cycles 
 
 Produced in telephony 
 
 Alphabeti<ally arranged enumeration of technical equipment issued 
 
 l)y the Signal Clorps 
 
 Ainpcrc, d<'fin<'d 
 
 Anchors, screw 
 
 Anemometer, portable, for small-armfl target ranges 
 
 Apjjaratus, tel<;grapli, adjustincmt for maximum strength. 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (014)
 
 Subject Index. 
 
 Sul)jt'cts. 
 
 Armor (sheathing) wires, to determine number required. 
 
 Artificial line, duplex telegraphy 
 
 Automatic transmitter for use on long submarine cables. 
 
 B. 
 
 Bag, tool service, and contents 8 68 
 
 Batteries: 
 
 Comparative merits ascertained 
 
 Closed circuit 
 
 Closed circuit, service used for 
 
 Closed circuit, t>'pes used by the Signal Corps 
 
 Dry cells, internal resistance and weights 
 
 Dry cells, testing 
 
 Dry, maintenance of 10 
 
 Dry, t>^es used with various apparatus 
 
 To reju\'enate 
 
 Duplex telegraphy 
 
 Edison primary, type ^ 
 
 Fuller 
 
 Fuller, deterioration with age 
 
 Gravity cell 
 
 Gravity cell, internal resistance and voltage 
 
 Number and kind required for various Signal Corps apparatus. 
 
 Open circuit 
 
 Oi)en circuit, service used for 
 
 Primary 
 
 Reserve type 
 
 To place in service 
 
 To rejuvenate 
 
 Secondary, general 
 
 Secondary, how known 
 
 Service testing 
 
 Storage — 
 
 Accumulation of sediment 
 
 Additional instructions for erecting 
 
 Care of 
 
 Coimecting the charging circuit 
 
 Construction of racks 
 
 Edison 
 
 Electric Storage Battery Co.'s table of ratings 
 
 General 
 
 General data concerning 
 
 Height of electrolyte 
 
 Impmities in electrolyte 
 
 Initial charge — 
 
 Chloride accumulator 
 
 For various makes 
 
 Gould 
 
 Willard 
 
 Instructions relative to installing and initial charge 
 
 Location of 
 
 Makes in use by the Signal (^orps 
 
 Number of cells supplied for C. B. post telephone systems 
 
 Overcharge 
 
 Pilot cell 
 
 Power requii-ed for initial charge 
 
 Placing out of service 
 
 Placing in service after being out of service 
 
 Preparing electrolyte 
 
 Purposes for wliich supplied 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (ol5) 
 
 ("liap- 
 tcr 
 .No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 34 
 17 
 26
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 
 No. 
 
 Batteries — Continued. 
 Storage — Continued . 
 
 Regular charge. 
 
 Report, monthly 
 
 Table showing sizes and ratings 
 
 Temperature effects 
 
 Tests of electrolyte 
 
 To raise specific gravity of electrol>i;e 
 
 Treatment of, when battery is to stand idle 
 
 \Miy they should not remain in a discharged condition. 
 
 Supplied by the Signal Corps 
 
 The dry battery 
 
 To determine how to connect 
 
 Tungsten, type A 
 
 Voltage and internal resistance of various types 
 
 Voltage used for cormnon battery post telephone systems. . . 
 Bells, extension: 
 
 How to connect » 
 
 Loud ringing and indoor type 
 
 Blank forms of Signal Corps, where enumeration may be found . 
 
 Bolts, toggle 
 
 Box: 
 
 Cable, use of 
 
 Distributing, for target ranges 
 
 Junction, target range 
 
 Terminal — 
 
 General 
 
 Metal — 
 
 First model 
 
 Terminal strip used 
 
 1915 model 
 
 Box, 100,000 ohm, standard. 
 
 Bridge type of duplex telegraphy 
 
 Bridge, Wheatstone: 
 
 Graphical demonstration 
 
 Post-office type 
 
 Precautions in operating 
 
 Principle explained 
 
 Simplest measurement 
 
 Used at Alaskan cable offices 
 
 Bridle rings 
 
 Bridle wire 
 
 Buzzer connectors 
 
 Buzzer, service 
 
 Action of interrupter 
 
 Circuits classified and traced 
 
 Construction described 
 
 Cord, plug, line connector, and ground rod 
 
 Instruments it replaces 
 
 Interrupter and transmitter circuits combined 
 
 Its use 
 
 Mutual and self-induction defined 
 
 Operation defined 
 
 Signals exchanged with line open 
 
 Simplified "through circuits" when sending Morse signals. 
 
 Theory of ol)Holete field buzzer 
 
 To operate on existing telegraph lines 
 
 Used as a telephone or telegraph instrument 
 
 Weight of, comjjlete 
 
 Buzzer wire 
 
 1 
 10 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 9 
 G 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (510)
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 Cable: ^• 
 
 And cable systems 
 
 Books supplied on cable testing 
 
 Capacity measurements when cable exceeds 100 miles in length ... 11 
 
 Classified 4 
 
 Determination of number of sheathing (armor) wires required .... 9 
 
 Electrolysis and remedy 4 
 
 Grapnels ut?ed in recovering submarine cable ' H 
 
 Gutta-percha insulation 11 
 
 Handhng and hanging to aerial messenger 5 
 
 Installation of — 
 
 Aerial cable 4 
 
 General 4 
 
 Submarine 4 
 
 Precautions to avoid rupture 4 
 
 Underground- 
 Avoiding pulling a second cable in conduit 4 
 
 Branching conduit 4 
 
 Characteristics of fiber conduit 4 
 
 Connection to aerial cable 4 
 
 Conduit construction 4 
 
 Construction of manholes 4 
 
 Handholes 4 
 
 Manholes 4 
 
 Formula for mixing concrete 4 
 
 Method of mixing concrete 4 
 
 Procedure 4 
 
 Pulling cable in conduit 4 
 
 Racking, tagging, and recording 4 
 
 Trenching 4 
 
 Two methods 4 
 
 Ty^pes of conduit 4 
 
 Lapping for splice and sealing ends 5 
 
 Paper insulation — 
 Armored — 
 
 Detailed characteristics of all types •. 
 
 Dimensions and weights of shipping reel 8 
 
 Weights and lengths 8 
 
 Lead-covered, unarmored — 
 
 Detailed characteristics of all types 
 
 Lengths and reels 
 
 Power 
 
 Detailed characteristics of all types 
 
 Special types that have been purchased 
 
 Usually in Signal Corps stock 
 
 Protection of aerial installations 
 
 Reels, and their numbers 
 
 Collect a quantity before return 
 
 Return lagging to reels 
 
 Relative to all cable used by Signal Corps 
 
 Rubber insulation — ! 
 
 Submarine — I 
 
 Detailed characteristics of all types 
 
 Lengths 
 
 Weights ■ 
 
 Subterranean — ; 
 
 Detailed characteristics of all types ! 
 
 Lengths | 
 
 Weights 
 
 Splicer's tool chest and contents 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (517) 
 
 8 
 4 
 
 29 
 
 7 
 
 5 
 
 27 
 
 4 
 
 7 
 
 4 
 
 8 
 
 4 
 
 8 
 
 8 
 
 24 
 
 8 
 
 25 
 
 8 
 
 26 
 
 8 
 
 27 
 
 8 
 
 27 
 
 8 
 
 27 
 
 8 
 
 27 
 
 8 
 
 64
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 Cable — Continued. 
 Splicing— 
 
 General 
 
 Gummed ])aper to limit wiped joint 
 
 Gutta-percha insulation 
 
 Lead sleeves for various sizes of, splices 
 
 Paper insulation cables 
 
 Material required for 
 
 Boiling out a splice 
 
 Complete splice day begun, if possible 
 
 Connecting the conductors 
 
 Detecting presence of moisture 
 
 Paper insulation — 
 
 Direction for setting up pothead 
 
 Filling pothead with compound 
 
 Method of making pothead 
 
 Placing paper sleeves 
 
 Pot head, determining dimensions of lead sleeves 
 
 Preparation for lead sleeves 
 
 Seal cable ends 
 
 Submarine 
 
 Transpose circuits 
 
 Wrap splice with muslin 
 
 Rubber insulation — 
 
 Lead covered and armored 
 
 Materials and tools required 
 
 Plain lead-covered cable 
 
 Materials and tools required 
 
 Pot heads for 
 
 S. C. type 251 cable 
 
 Using manufactured sleeve 
 
 Submarine 
 
 Materials required 
 
 Raw joint described 
 
 Relative to acid soldering flux 
 
 Various vulcanizers 
 
 Vulcanized joint 
 
 Solder used 
 
 Suggestions concerning 
 
 Three way or " Y " splices 
 
 Placing split lead sleeve 
 
 Submarine^ 
 
 Cal)le gear and supplies 
 
 General 
 
 Gutta-percha and rubber compound insulation, general. . . 
 Long- 
 Alaska cable data 
 
 Arrangement of instruments for operating 
 
 Arrangement of testing set 
 
 Automatic transmitters 
 
 Cable testing 
 
 Capacity measurements when cable exceeds 
 
 miles in length 
 
 Conductor resistance 
 
 ])(!scrii)tion of Fisher cal)le testing set, No. 2 
 
 Elimination of earth current effects 
 
 Fisher cable-lesting set, special Wheatstone bridge. 
 
 M(ui.sining capacity with Fisher set 
 
 Mea.suring length of single conductor cable 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 100 
 
 4 
 4 
 11 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 
 (B18)
 
 Subject Index. 
 
 Subjects. 
 
 laid 
 
 Cable — Continued . 
 
 Submarine — Continued. 
 Long — Continued. 
 
 Cable testing — rontinued. 
 
 Notes on capacity measurements 
 
 Recommended treatises 
 
 Sample tost sheet 
 
 Special instruments used 
 
 Wheatstone bridge used at Alaskan offices . . 
 Cuttriss automatic transmitter 
 
 Adjustment 
 
 Data pertaining to the Sitka-Seattle cable when 
 
 Excessive voltage not to be used 
 
 Faults classified 
 
 General 
 
 Ground connections for Morse operation 
 
 Grapnels used in recovering 
 
 Gutta-percha insulation 
 
 Instruments for Morse operation 
 
 Instructions for shore stations during laying or repair of 
 
 cable 
 
 Laying 
 
 Laying by improvised means 
 
 Paying out the cable , 
 
 Lightning arrester, office wiring , 
 
 Location of faults , 
 
 Clark's potential test , 
 
 Classes i and 2 
 
 Class 3 
 
 Examples of Jordon and Schonaus modification 
 
 Formula for testing for breaks or grounds, nonmetallic 
 circuit 
 
 Handy formulae for testing for breaks and grounds. . . . 
 
 Jordon and Schonaus modification , 
 
 Prof. Keunelly's method 
 
 Two laboratory tests explained 
 
 Measin-ing conductor resistance Ti-ith Fisher testing set 
 
 Measuring insulation with Fisher testing set 
 
 Method of obtaining ground near large cities 
 
 Morse telegi-aph, double-current operation 
 
 Murray loop test -n-ith Fisher testing set , 
 
 Notes on efficient Morse working 
 
 Proper touch to key 
 
 Relays 
 
 Repeaters 
 
 Notes on efficient working of a station and on common 
 
 troubles 
 
 Operation of 
 
 Single-current open-circuit repeater set 
 
 Using Morse telegi-aphic apparatus 
 
 Operation of, using siphon recorders 
 
 Reflecting galvanometer — 
 
 A\Tton universal shunt 
 
 D'Arsonval 
 
 Remarks on the shunt 
 
 Shunts 
 
 Sullivan 
 
 Thomi)son 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and 
 
 11 
 11 
 11 
 11 
 11 
 11 
 
 n 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 
 11 
 11 
 11 
 11 
 11 
 
 11 
 11 
 11 
 11 
 n 
 11 
 
 supplies. 
 
 (519.1
 
 10 
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 Cable — Continued. 
 
 Submarine — Continued . 
 Long — Continued . 
 
 Single-current open-circuit repeater sets — 
 
 Adjustment of sounders 
 
 Transmitters 
 
 With polarized relays 
 
 Siphon recorders 
 
 Adjustment : 
 
 Auxiliary apparatus 
 
 Care of 
 
 Hybrid type 
 
 Large and small 
 
 Motor 
 
 Operated by electric-light current 
 
 MuLrhead vibrator 
 
 Splicing gutta-percha insulation cable 
 
 Switchboards used 
 
 Termination of cable 
 
 Transmitter tape perforator 
 
 Use of dynamometer 
 
 Varley loop test with Fisher set 
 
 Wrapping of brass ribon 
 
 Number and location of those installed 
 
 Paper insulation 
 
 Latest approved types 
 
 Laying in emergency 
 
 Reserve 
 
 Rubber insulation latest approved types 
 
 Rubber insulation — 
 
 Manner of applying insulation 
 
 Multiple conductor 
 
 Single and double armor 
 
 Telegraphy. (See Cable submarine, Long.) 
 
 Subterranean 
 
 Armored when trenched 
 
 Double lead covered for marshes 
 
 Subterranean, paper insulation, latest approved types 
 
 Paperinsulation, double lead covered, latest approved types. , 
 
 Rubber insulation, latest approved types 
 
 System of assigning type numbers 
 
 Tank, circular, to determine capacity , 
 
 Terminals, fused and unfuscd , 
 
 Testing. (See "Tests,ca ble," for ordinary te.sts of cable. Sec 
 " Cable, submarine, long," for tests of long submarine cables.) 
 
 Transfer from one reel to another 
 
 Where connected to aerial wire 
 
 Camp telephones. (iSfc Telephone, camp.) 
 
 Capacity measurements 
 
 Care of storage batteries 
 
 Cart, signal 
 
 E()uipraent 
 
 Carrier, wire 
 
 (Jart, Avire: 
 
 Description, and how used 
 
 Type L, (^xtra and maintenance parts 
 
 Case, electrical instrument and contents 
 
 Cedar poles: 
 
 Dimensions and weights 
 
 Dimensions and weiirhlfl 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 31 
 
 11 
 
 U 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 9 
 
 4 
 
 4 
 
 4 
 
 4 
 
 4 
 
 4 
 4 
 4 
 
 4 
 4 
 4 
 4 
 4 
 4 
 8 
 9 
 5 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (520)
 
 Subject Index. 
 
 11 
 
 Subjects. 
 
 Cell: 
 
 Battery, determining how to connect 
 
 Dry bat tery 
 
 Reserve type 
 
 Edison, primary battery, type V 
 
 Fuller battery 
 
 Effect of age 
 
 Gravity battery. 
 
 Internal resistance and voltage 
 
 Voltaic 
 
 Polarity 
 
 Cells, battery, number and kind required for various Signal Corps 
 
 apparatus 
 
 Chatterton's compound 
 
 Chests : 
 
 Pack, how used 
 
 Tool- 
 Aeroplane and contents 
 
 Cable splicer's and contents 
 
 (Construction and contents 
 
 Electrical engineers and contents 
 
 Mechanic's and contents 
 
 Pipe fitter's and contents 
 
 Post and contents 
 
 Clamp and pigtail insulators 
 
 Closed circuit: 
 
 Batteries 
 
 Ser^•ice used for 
 
 Type supplied by Signal Corps 
 
 Telegraph system 
 
 Coefficient temperature 
 
 Of various metals 
 
 Coil, exploring: 
 
 To identify cable in trench 
 
 To locate a ground 
 
 Common batterv telephone : 
 Desk— 
 
 Garford circuits 
 
 North Electric Co. circuits 
 
 General 
 
 Operation explained 
 
 Siunter, wall, circuits 
 
 Systems, number of cells of storage batteries used 
 
 Transmission 
 
 Wall- 
 Circuits traced 
 
 North Electric Co. circuits 
 
 Western Electric Co. circuits 
 
 Compound : 
 
 ('hatterton's 
 
 Gyite.. 
 
 Insulutine 
 
 Insulating 
 
 Ozite, three grades 
 
 Concrete: 
 
 Formula for mixing 
 
 Method of mixing 
 
 Condenser: 
 
 Defined 
 
 Standard, for cable testing 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (521)
 
 12 
 
 Subject Index.- 
 
 Subjects. 
 
 Chap- 
 ter 
 
 No. 
 
 Chap- 
 ter 
 page 
 
 No. 
 
 ConductiAdty, Matthiessen's standard 
 
 Conductor resistance 
 
 Conduit: 
 
 Construction 
 
 Characteristics of fiber conduit 
 
 Types of conduit 
 
 Fiber* 
 
 Iron 
 
 Connecting up the charging circuit of storage batteries. 
 
 Connector, buzzer 
 
 Construction: 
 
 Line tools 
 
 Of manholes 
 
 Tool chest and contents 
 
 Copper vrire (sec Wire). 
 
 Conts, Signal Corps, standard for all apparat us 
 
 Cross arms, dimensions 
 
 Cross-connecting wire - 
 
 Current, alternating 
 
 Cycles 
 
 Produced in telephony. 
 Current: 
 
 Direct 
 
 Pulsating, defined 
 
 D. 
 
 Data relative to Kerite compound 
 
 Data relative to Safety compound 
 
 Difference of potential 
 
 Differential telegraph relay, requirements 
 
 Direct current 
 
 Distance computed by means of sound 
 
 Double current duplex telegraphy 
 
 Dry batteries: 
 
 Construction of 
 
 Internal resistance and weights 
 
 To rejuvenate 
 
 Used with various apparatus 
 
 Duplex telegraphy '. 
 
 Dynamometer used in laying and recovering submarine cables. 
 
 E. 
 
 Edison primary battery, type V 
 
 rOdison storage battery 
 
 F'^Ieclrifal ensnuecr's tool chest and contents 
 
 F'jlcctrical instrument case, contents 
 
 Elect rical instrument case and contents 
 
 Electric drills and f)ther special tools 
 
 Electrolysis and remedy 
 
 Electromagnetism 
 
 Electrostatic capacity measurements 
 
 F'^Iectrostatic induction 
 
 Elenieiit.s of dnjilex )elegrai)]iy 
 
 I'^leinenls of j)olar duplex telegraphy 
 Ivjuipment issued by the Signal <'o 
 ni<!ration... 
 
 See Chap. 8 
 
 by the Signal ('orps, alphabetically arranged enu 
 p. I, Tor ulphabetical list or all Signal Corps apparatus and 
 
 52 
 
 14 
 18 
 
 8 
 supplies. 
 
 (522)
 
 Subject Index. 
 
 13 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 Exploring roil: 
 
 To identify cable-s in trench. . . 
 
 To locale a ground 
 
 Extension bells: 
 
 How to connect 
 
 Loud ringing and indoor type. 
 
 Factory tests: 
 
 Of' cable 
 
 Sample of record 
 
 Faultfinder 
 
 Fence-post lines for aerial construction 
 
 Fiber conduit 
 
 Field buzzer, theory 
 
 Field equipment: 
 
 Maintenance of 
 
 Miscellaneous 
 
 Field glasses, description of each type supplied by the Signal Corps.. 
 
 Field-induction telegraph, its u.se 
 
 Field operations: 
 
 Instruments for lines of information 
 
 Selection of instruments 
 
 Wire used, description 
 
 Wire used in emergencies 
 
 Field transportation 
 
 Field wire 
 
 To splice 
 
 Fisher cable testing set No. 2, description 
 
 Fixture Avire 
 
 Formulae: 
 
 For converting statute miles to nautical miles 
 
 For logarithmic law for reducing insulation resistance to 60° F. . . 
 
 For mixing concrete 
 
 For reducing copper resistance to 60° F 
 
 For testing cables for breaks and grounds, not metallic circuit. . . 
 
 For testing cables, for breaks, grounds, and earth overlap 
 
 For testing cables for breaks, Jordan and Schonau's modification. 
 
 Matthiessen's, for soft copper wire 
 
 Miscellaneous, relative to vnres 
 
 Reducing resistance to a given temperature 
 
 Specific conducti\'ity 
 
 Specific resistance 
 
 Specific resistance at various temperatures 
 
 To compute distance by means of sound 
 
 To compute value of insulation when testing with a voltmeter. . . 
 
 To determine capacity of circular tank 
 
 To determine number of sheathing (armor) ^vires required 
 
 L'sed in locating faults in cable 
 
 Used in locating faults, Prof. Kennelly's method . 
 
 Front Royal, Va., remount depot: 
 
 Aerial line construction employed 
 
 Post telephone system 
 
 Fuller battery cell 
 
 Effect of age *. 
 
 Fuses; furnish sample if other than standard desired 
 
 Standard 
 
 11 
 
 9 
 
 4 
 
 4 
 
 4 
 
 11 
 
 11 
 
 11 
 
 9 
 
 9 
 
 9 
 
 9 
 
 9 
 
 9 
 
 9 
 
 10 
 
 9 
 
 9 
 
 11 
 
 11 
 
 5 
 6 
 1 
 1 
 
 19 
 
 18 
 
 22 
 22 
 
 6.=) 
 70 
 25 
 31 
 4.3 
 27 
 
 13 
 
 87 
 40 
 
 28 
 28 
 27 
 28 
 26 
 85 
 85 
 42 
 83 
 
 39 
 68 
 12 
 59 
 70 
 64 
 71 
 32 
 38 
 32 
 30 
 30 
 31 
 39 
 
 39 
 34 
 58 
 59 
 
 29 
 25 
 9 
 10 
 42 
 42 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 46581°— 17 34 
 
 (523)
 
 14 
 
 Subject Index. 
 
 Subjects. 
 
 G. 
 
 Galvanized iron wire 
 
 Characteristics 
 
 Galvanometers, reflecting: 
 
 Ayrton universal shunt used 
 
 D" Arson val 
 
 Do 
 
 Remarks on shunts 
 
 Shunts 
 
 Sullivan 
 
 Thompson 
 
 Gauges, wire 
 
 Comparison of various types 
 
 Commonly used 
 
 Law of the Brown & Sharpe gauge 
 
 General data concerning the storage battery 
 
 General information, lines of information i . . 
 
 Lines of information classified 
 
 General Order, War Department, relative to post telephone systems. 
 
 Glas.ses, field, types, description, etc. 
 
 Gravity battery cell 
 
 Internal resistance and voltage 
 
 Ground for signaling over long submarine cables 
 
 Ground rods 
 
 Gyite-. 
 
 H. 
 
 Hammers, marking 
 
 Handholes, for underground cable systems 
 
 Hand reel 
 
 And wire carrier, how used 
 
 Hard-drawn copper wire 
 
 Characteristics 
 
 Heat coils: 
 
 And protectors. Western Electric and Cook . 
 
 For switchboard protectors 
 
 House wire 
 
 Tdontifiration of cable conductors 
 
 Impurities in storage battery electrolyte 
 
 Induction coil 
 
 Induction: 
 
 Electromagnetic 
 
 Electrostatic 
 
 Magnetic 
 
 Mutual and self-defined 
 
 Induction telegraph set 
 
 Duplex operation 
 
 Instructions for operating 
 
 It« use 
 
 Theory 
 
 To u.se as a closed-circuit telegraph set. 
 Initial charge of storage batteries: 
 
 Chloride accumulator 
 
 (iouid 
 
 < )f various makes 
 
 Willard 
 
 11 
 
 11 
 
 4 
 
 11 
 
 11 
 
 11 
 
 11 
 
 9 
 
 9 
 
 9 
 
 9 
 
 1 
 
 9 
 
 9 
 
 (i 
 
 8 
 
 1 
 
 1 
 
 11 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (524)
 
 Subject Index. 
 
 15 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 tor 
 
 Inside twistcnl pair wire 
 
 Inside twi.sted triple conductor wire 
 
 In.=!pection, maintenance 
 
 In.spector's pocket tool kit and contents 
 
 Installation of cable: 
 
 Aerial cable 
 
 (leneral 
 
 Submarine cable 
 
 Submarine cable, precautions to avoid rupture. 
 
 I'nderground cable 
 
 Instrument case, electrical, contents 
 
 Instruments for field lines: 
 
 The camp telephone, its use 
 
 The buzzer, its use 
 
 The field induction telegraph, its use 
 
 Instruments, selection of. for u.se in the field 
 
 Instrument wagon, how ii.sed 
 
 Insulatine 
 
 Insulating and splicing materials 
 
 Insulating compounds 
 
 Insulation measurements: 
 
 Explanation of principle involved 
 
 To determine galvanometer constant 
 
 Insulation test 
 
 To compute values 
 
 With telephone receiver 
 
 Iron conduit 
 
 Junction box, target range. . 
 
 K. 
 Keys: 
 
 Employed in telegraphy 
 
 Strap." 
 
 Kit, tool, in.spector's pocket, and contents. 
 Knife switches 
 
 L. 
 
 Lance poles, and insulators 
 
 Lance trtick, how used 
 
 Law of magnetic induction 
 
 Law of Brown & Sharpe gauge 
 
 Lead sleeves for cable splices 
 
 To determine size 
 
 Lightning arresters: 
 
 For protecting telephones 
 
 Mason 
 
 Moisture-proof tA-pe 
 
 Principle of operation 
 
 Protective feature 
 
 Telegraph 
 
 Line construction. (See Aerial line construction.) 
 
 Lines of force defined 
 
 Lines of information 
 
 Classified 
 
 Selection of instruments 
 
 Liquid conductors, resistance of 
 
 10 
 
 See Chap. 8, p. 1, for alphabetical list of ail Signal Corps apparatus and supplies. 
 
 (525)
 
 16 
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Local batteiy telei^hono: 
 
 Desk 8et 
 
 Garford, and circuits 
 
 Garford circuits 
 
 Sumter and circuits 
 
 Transmission 
 
 Typical circuit traced 
 
 Locat ion of storage battery 
 
 Location of faults in telegraph lines 
 
 Logarithmic law, variations of insulation resistance with temperature 
 changes 
 
 M. 
 
 Magnetic force 3 
 
 Magnetic induction 3 
 
 Governing laws 3 
 
 Magnet, to construct 3 
 
 Magnetism 3 
 
 Electro 3 
 
 Polarity of a magnet 3 
 
 Magneto, telephone 3 
 
 Action explained , 3 
 
 Automatic circuit opener 3 
 
 Sizes furnished by the Signal Corps 3 
 
 Magneto telephone switchboards: 
 
 15-line size G 
 
 50-line size | 6 
 
 50-line size, rewire ringing power key 6 
 
 Cordless type 6 
 
 To stop magneto handle unscrewing 6 
 
 Maintenance: 
 
 Inspection of post telephone systems 10 
 
 Of common battery telephones, faults likely to occur 6 
 
 Of dry l)atteries. .'. • 10 
 
 ( )f local battery telephones, faults likely to occur 6 
 
 Of motor generators. {See "Motor generators. ") 
 
 Of post telephone systems 6 
 
 ( )f power switchboards 10 
 
 Of telephone switchboards, faults likely to occur 6 
 
 ( )f various field e(|uipment 10 
 
 Storage-battery reports 10 
 
 Tools for the purpose 10 
 
 Manholes: 
 
 Construction of 4 
 
 Formula for mixing concrete 4 
 
 [•"or underground conduit system 4 
 
 Mclliod of mixing concrete 4 
 
 Support for boiler-plate cover 7 
 
 Manner of listing amounts of various tyi)es of wire 8 
 
 Marking hammers 8 
 
 Materials: 
 
 f nsidating and splicing ." 8 
 
 biiH- ron.struct ion 8 
 
 MaltiiicsHcn's standard of conductivity 9 
 
 Mattliiessen 's formula for soft copper wire 9 
 
 Measurements: 
 
 Capacity 4 
 
 Insulation 4 
 
 Mecliiinic 'h tool chest, and contisnts 8 
 
 Megaphones, (iber, 18-inch 8 
 
 Sec Chap. 8, p. 1, Tor alphabetical list or all Signal Corps apparatus and supplies. 
 
 (526)
 
 Subject Index. 
 
 17 
 
 .Siibjpots. 
 
 Megger, tests with 
 
 Messenger strand (see Aerial line construetion ), properties of . 
 
 Meter, watt-hour, installed in connection with common battery 
 
 telephone systems 
 
 ^^etaI terminal boxes 
 
 I !) 1 5 model 
 
 Miscellaneous: 
 
 Field equipment 
 
 Tests 
 
 post 
 
 Wires 
 
 Miles- to convert statute miles to nautical miles. 
 
 Mogul paint 
 
 Moldings, three tj'pes of 
 
 ^^onthly storage-batterj^ report 
 
 Morse telegraphy. (^S'ee Telegraphy, Aforse.) 
 Motor generator: 
 
 Brushes 
 
 Care of commutator 
 
 Cause of overheating of — 
 
 Bearings 
 
 Commutator : 
 
 Cause of sparking 
 
 Excessive field heating 
 
 Maintenance of 
 
 Maintenance, bearings 
 
 Starting 
 
 Stopping 
 
 Throwing or leaking of oil 
 
 Murray and Varley loop tests - 
 
 Mutual and self-iuduction defined 
 
 O. 
 
 OfTice equipment, telegraph offices 
 
 Office wire 
 
 Ohm defined 
 
 Ohms law 
 
 Applied to alternating current 
 
 Applied to a part of a circuit 
 
 Applied to circuit containing ball cry 
 
 Ohmmeter: 
 
 Description 
 
 Directions for tising 
 
 Location of faults in multiple conductor cable 
 
 Model 1 904 -. 
 
 Open-circuit batteries 
 
 Service used for 
 
 Open-circuit telegraph system 
 
 Operation of buzzer defined 
 
 < )peration oi' telephone transmitter 
 
 Operation of long submarine c-ables (See Cables, submarine, long). 
 
 ( )utside distributing wire, copper clad 
 
 Outside twisted pair wire 
 
 Overcharge of storage batteries 
 
 Ozite, tluee grades 
 
 Pack chests, how used. 
 
 Paint, Mogul 
 
 Paraffiiic 
 
 10 
 
 8 
 
 t; 
 8 
 
 8 
 
 8 
 9 
 8 
 9 
 8 
 8 
 10 
 
 10 
 10 
 
 10 
 10 
 10 
 10 
 10 
 10 
 10 
 10 
 10 
 9 
 3 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (r.27)
 
 18 
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 Perforators, transmitter tape 11 
 
 Photography 8 
 
 Pigtail and clamp insulators 
 
 Pikes, wire 
 
 Pilot cell of storage battery 
 
 Pipe fitter's tool chest and contents 
 
 Placing storage batteries in service after being out of service 
 
 Placing storage batteries out of service 
 
 Points for cable testers 
 
 Polar duplex telegraphy: 
 
 Balancing 
 
 Operation , 
 
 Polar relay 
 
 Polarity of a magnet 
 
 Pole changer, for polar duplex telegraphy 
 
 Poles: 
 
 Telegi^aph and telephone {See also Aerial line construction") — 
 
 Ceclar, dimension and weights 
 
 Steel and iron 
 
 Tripod : 
 
 Wooden, dimensions 
 
 Lance, and insulators 
 
 Portable anemometer for small-arms target ranges 
 
 Portable voltameter issued by the Signal Corps 
 
 Post telephone system: 
 
 Care of 
 
 Common battery power equipment 
 
 Arrangement of 
 
 Battery feed where battery is remote from switchboard 
 
 Bridge battery feed with condenser .■ . 
 
 Current consumed chargeable to Signal Corps 
 
 Leads from electric lighting main 
 
 Motor generator and mercury arc rectifier 
 
 One battery only to be installed when charged by a generator. 
 
 Power switchboards 
 
 Two batteries, when charged through lamps 
 
 WTiere charging current is alternating 
 
 AMiere watt-hour meter is installed 
 
 Common battery switchboards — 
 
 Battery voltage 
 
 Connections to commercial telephone exchange 
 
 Connections to protectors 
 
 Description of 
 
 Lamp line and lamp supervisory signals, type 
 
 Multiple type 
 
 Principal circuits of all above 200-line size 
 
 Principal circuits of lamp line and lamp supervisory signals 
 
 type 
 
 Sizes 
 
 Type now furnished in the 50, 100, and L'OO line size 
 
 Types defined 
 
 Visual line and lamp supervisory si^'iials 
 
 Visual line; and visual supervisory signals 
 
 Connections to telephones remote from posts 
 
 General order relative to post telephone systems 
 
 (ieneral 
 
 I list allat ion of telephone switchboard 
 
 I.iglitning arresters for telephones 
 
 Lightning arnater, protective features 
 
 Local liiitterv 
 
 See Chap. 8, p. 1, for alphabelical list uf all Signal Corps apparatus and supplies. 
 
 10 
 
 4 
 
 6 
 
 35 
 
 6 
 
 36 
 
 6 
 
 35 
 
 6 
 
 36 
 
 6 
 
 39 
 
 6 
 
 39 
 
 6 
 
 38 
 
 6 
 
 37 
 
 6 
 
 39 
 
 6 
 
 38 
 
 6 
 
 38 
 
 6 
 
 39 
 
 6 
 
 6 
 
 6 
 
 18 
 
 6 
 
 33 
 
 6 
 
 9 
 
 6 
 
 16 
 
 6 
 
 16 
 
 C 
 
 17 
 
 () 
 
 19 
 
 6 
 
 9 
 
 
 
 16 
 
 G 
 
 6 
 
 
 15 
 
 
 6 
 
 
 o 
 
 
 I 
 
 
 1 
 
 
 26 
 
 
 2 
 
 
 3 
 
 () 
 
 21 
 
 (528)
 
 Subject Index. 
 
 19 
 
 Subjects. 
 
 Post telephone system — Continued. 
 
 Local battery (magneto) switchboards. {See Switchboard.) 
 
 Location of switchboards 
 
 Maintenance 
 
 Comnion battery installations, faults likely to occur 
 
 Dry batteries 
 
 Inspections 
 
 Local battery instruments, faults likely to occur 
 
 Motor generators. (See "Motor generators. ") 
 
 Power switchboards 
 
 Telephone switchboards, faults likely to occur 
 
 Tests 
 
 With megger 
 
 \\'ith post testing voltmeter 
 
 Mason lightning arrester 
 
 Moisture proof type protector (lightning arrester) 
 
 Monthly storage battery report 
 
 Never ' ' boil out " rubber-covered wire 
 
 Operation of common battery switchboards — 
 
 Switchboard, 200-line size, night bell 
 
 Switchboard, night bell 
 
 Use of the generator call drops 
 
 \'isual line and ^■isual supervisory signals 
 
 Principle of operation of lightning arrester 
 
 Procedure in ''laying out" a system 
 
 Records — 
 
 Cable lengths, slack cable, and splices 
 
 Component parts of a record 
 
 General 
 
 Location of duct lines and trenched cable 
 
 Location of manholes 
 
 Miscellaneous 
 
 Necessary Signal Corps forms enumerated 
 
 Post telephone connections and other data 
 
 Record all modifications 
 
 Routing of cables and aerial lines and location of structures. 
 
 Show ing arrangement of power equipment 
 
 Special circuits 
 
 Terminals, cross connections, and spare pairs and circuits... 
 Requisitions for maintenance supplies. (See "Requisitions.") 
 
 Ringing (calling ) apparatus 
 
 Semiannual inspection 
 
 Switchboard cable — 
 
 Color scheme ' 
 
 Installation of 
 
 Use of 
 
 Switchboards — 
 
 Cable forms 
 
 Connecting up 
 
 Construction of 
 
 To expel moisture 
 
 Where a temporary construction form can not be used . . 
 
 Locations 
 
 Location of condensers 
 
 Protector apparatus, general 
 
 Protector frames and protectors 
 
 Protector heat coils 
 
 Relative to unpacking 
 
 To test connecting cords 
 
 Tools for maintenance purposes 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and 
 
 Chap- 
 ter 
 
 No. 
 
 Chap- 
 ter 
 
 
 
 C 
 
 G 
 10 
 10 
 
 G 
 
 10 
 
 G 
 
 10 
 10 
 10 
 
 G 
 
 G 
 10 
 
 G 
 
 6 
 6 
 6 
 6 
 6 
 6 
 
 6 
 6 
 6 
 10 
 6 
 6 
 6 
 6 
 6 
 6 
 6 
 6 
 6 
 
 G 
 10 
 
 6 
 6 
 6 
 
 6 
 6 
 G 
 G 
 G 
 6 
 6 
 G 
 6 
 6 
 6 
 6 
 10 
 
 supplies. 
 
 (529)
 
 20 
 
 Subject Index. 
 
 Subjects. 
 
 Chai>- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 Post telephone system — Continued. 
 
 Western Electric and Cook heat coils and protectors 
 
 Where one room only is available for central station equipment . 
 
 Post testing voltmeter 
 
 Post tool chest and contents 
 
 Potential difference 
 
 Potheads: 
 
 For paper insulation cable 
 
 Directions for setting up 
 
 Filling pothead with compound 
 
 To determine dimensions of lead sleeves 
 
 For rubber insulation cable 
 
 Pothead wire 
 
 Power cables 
 
 Usually in Signal Corps stock 
 
 Power for operating telegraph systems 
 
 Power required for initial charge of storage batteries 
 
 Power switchboards 
 
 ^laintenance of 
 
 Preparing electrolyte for storage batteries 
 
 Primary batteries 
 
 Properties of strand 
 
 Pulling cable in conduits 
 
 Fa-stening rope to cable 
 
 Pulsating currents defined 
 
 Pinposes for which storage batteries are supplied 
 
 R. 
 
 Racking cables in manholes 
 
 Racks for storage batteries, construction of 
 
 Receiver, telephone 
 
 Recorder, siphon 
 
 Adjustment of 
 
 Auxiliary apparatus 
 
 Care of 
 
 Hybrid type 
 
 Motor .• 
 
 Motor operated by electric light current 
 
 Miurhead vibrator 
 
 Recording cable lengths installed 
 
 Records of a post telephone system: 
 
 Arrangement of power equipment 
 
 Cable length, slack cable, and splices 
 
 Component parts 
 
 General 
 
 Location of manholes 
 
 Miscellaneous 
 
 Post telephone connections and other data 
 
 Record all modifications 
 
 Routing of ca})le and aerial lines and location of structures. 
 
 Signal ( 'orps forma enumerated 
 
 Special circuits 
 
 Tenninals, cross connections, spare pairs, and circuits 
 
 Records of a small anna target range signaling system 
 
 Component parta listed 
 
 How prepared 
 
 Oflicesfnrnibhed 
 
 Signal Corps forma used 
 
 Upkeep of 
 
 6 
 
 6 
 
 10 
 
 10 
 1 
 1 
 
 8 
 4 
 4 
 1 
 1 
 
 4 
 
 1 
 
 3 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 11 
 
 4 
 
 6 
 6 
 6 
 6 
 6 
 6 
 6 
 C 
 G 
 6 
 6 
 6 
 7 
 7 
 7 
 7 
 7 
 7 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (530)
 
 Subject Index. 
 
 21 
 
 Subjects. 
 
 Keels, cable: 
 
 Collect a quantity before returning them 
 
 Return lagging with reels 
 
 To be numbered 
 
 Transfer of cable from one reel to another 
 
 Reels, hand 
 
 Reflecting galvanometer: 
 
 A>Tton universal shunt 
 
 D'Arsohval 
 
 Do.. 
 
 Remarks on shunt 
 
 Shunts 
 
 Sullivan 
 
 Thompson 
 
 Regular charge of storage battery 
 
 Regulations concerning requisitions . (See " Requisitions.") 
 
 Relay, polar, for Morse telegraph 
 
 Relays, telegraph 
 
 Repeaters, telegraph 
 
 Mlliken 
 
 Weiny 
 
 Closed circuit repeating open circuit signals and vice versa 
 
 Requisitions: 
 
 Department signal officers, regulations concerning 
 
 For maintenance supplies 
 
 From State militia organizations 
 
 Items, regulations concerning 
 
 Property officers, regulations concerning 
 
 Sample items 
 
 Do!;!!!;;;!!!!;;!!!;_;!!!!!!!!!!!;;;!!;;;;j;;;^^;;^^;;!^!^! 
 
 Signal Corps field companies, regulations concerning 
 
 Those who prepare them, regulations concerning 
 
 To be serially numbered 
 
 With some items necessarv to show either manufacturer or size, or 
 
 both " 
 
 Reserve tj^e of dry cells 
 
 Internal resistance and weights 
 
 Testing 
 
 To rejuvenate 
 
 To place in service 
 
 Resistance: 
 
 Of conductors 
 
 Of liquid conductors 
 
 Specific 
 
 Specific and relative conductivity of conductors 
 
 Units of 
 
 Ringer, telephone 
 
 Operation 
 
 Resistance of windings 
 
 Rings, bridle 
 
 Rods, ground, types 
 
 Rubber covered wire 
 
 4 
 4 
 4 
 4 
 
 8 
 
 11 
 11 
 
 4 
 11 
 11 
 11 
 11 
 
 1 
 
 10 
 10 
 10 
 10 
 10 
 10 
 10 
 10 
 10 
 10 
 10 
 
 10 
 
 1 
 1 
 1 
 
 1 
 1 
 
 1 
 
 9 
 9 
 9 
 9 
 3 
 3 
 3 
 8 
 8 
 8 
 
 S. 
 
 Screw, anchor 
 
 Secondary batteries. (See Batteries, storage.) 
 Ser\-ice buzzer. [See Buzzer.) 
 
 Service testing battery for cable testing 
 
 Service tool hag; and contents 
 
 43 
 
 G8 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (531)
 
 09 
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 
 Set. induction, telegraph 
 
 Instructions for operating 
 
 Duplex operation 
 
 Theory 
 
 To use as a closed -circuit telegraph set 
 
 Shunt and key for cable testing 
 
 Signal cart 
 
 Equipment 
 
 Signal Corps: 
 
 Blank forms, reference 
 
 Specifications enumerated 
 
 Standard cords for all apparatus 
 
 Single current or Steams duplex telegraphy. . . 
 Siphon recorder 
 
 Adjustment 
 
 Auxiliary apparatus 
 
 Care of 
 
 Hybrid type 
 
 T>arge and Small 
 
 Motor > 
 
 ^lotor operated by electric-light current. . . 
 
 Muirhead vibrator 
 
 Sleeves, lead: 
 
 To determine size for cable splicing 
 
 Various sizes, for cable splicing 
 
 Small arms target ranges. (See Target range.) 
 Solder 
 
 "Wiping, used in cable splicing 
 
 Soimders, telegraph - . 
 
 Adju.=!tment of 
 
 Special tools 
 
 Specifications, Signal Corps, enumerated 
 
 Specific and relative resistance and relative conductivity of conductors. 
 
 S])ecific resistance 
 
 Speech, transmission of, telephonically 
 
 Splicing and insulating materials 
 
 Splicing cables. (See Cable splicing.) 
 
 Spring hammers and other special tools 
 
 Storage battery. (See Batteries, storage.) 
 
 Storage liattery report, monthly 
 
 Strand , properties of 
 
 Strap keys 
 
 Strip, standard porcelain 
 
 Submarine cable. (See Cable, submarine.) 
 Sul)terranean cable. (See Cable, subterranean.) 
 S^^^t<■hlx)ard: 
 
 Power 
 
 Maintenance of 
 
 Telegraph 
 
 And repair parts 
 
 Terminal and battery arrangement 
 
 Teleplioiie, r<'la1ive to — 
 
 " Boiling out " rublx;r-covered wire 
 
 Cable, color scheme 
 
 Cable forms 
 
 Connecting uj) 
 
 Construction of 
 
 A\ hen! temporary const ruction form can notlx' uh<'<I 
 
 10 
 
 See Chap. 8, p. 1, fur alphabetical list of all Signal Curp.s apparatus and supplies. 
 
 (r..rj)
 
 Subject Index. 
 
 23 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 Switchboard — Continued . 
 
 Telephone, relative to — Continued. 
 
 Cable, installation of , 
 
 tlse of 
 
 To expel moisture froia cable 
 
 Camp, description of 
 
 Common buttery, and repair parts 
 
 Description 
 
 Connection to commercial exchange 
 
 Connections to protectors 
 
 T.amp line and lamp supersdsory signal type. 
 
 Multiple t^'pe 
 
 Operation of night bell 
 
 Power equipment 
 
 Arrangement of 
 
 Battery feed when battery is remote from switchboard 
 
 Bridge battery feed with condenst^r 
 
 Current consumed chargeable to Signal Corps; 
 
 Leads from electric lighting mains 
 
 Motor generator and mercurj^ arc rectifiers 
 
 One batterv^only when charged by a generator 
 
 Power switchboards 
 
 Two batteries when charged through lamps 
 
 When watt-hour meter is installed 
 
 Where charging ciu'rent is alternating 
 
 Principal circuits of lamp line and lamp supervisory signal 
 
 type 
 
 Sizes 
 
 Tvpes, defined 
 
 200-line size— 
 
 Night bell , 
 
 Principal circuits of sizes above 
 
 Use of generator call drop 
 
 Visual line and lamp supervisor}' signals 
 
 Now furnished in 50, 100, and 200 line boards 
 
 Visual line and ^isual supervisory signals 
 
 Operation of - . j 
 
 Voltage used | 
 
 Installation of I 
 
 Local battery (magneto), and repair parts ^ | 
 
 Connections to protectors * 
 
 Cordless type 
 
 15-line size 
 
 50-line size 
 
 50-line size, rewire ringing power key 
 
 To prevent magneto handle from unscrewing 
 
 Location — 
 
 General 
 
 Specific ' 
 
 Of condensers 
 
 Protective apparatus, general 
 
 Protector frame and protectors 
 
 Heat coils 
 
 Testing connecting cords 
 
 L'npacking 
 
 Ringing apjiaratiis '. . 
 
 Western Electric and Cook heat coils and protectors 
 
 Where one room only is available for central station eqidpment 
 Switches, knife 
 
 See Chap. 8. p. 1. for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (533)
 
 24 
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 Tables: 
 
 Alaskan cable data 11 
 
 Amounts of sag of messenger strand 5 
 
 Amounts of sag of aerial wires at various temperatures 5 
 
 Approved types of double lead-covered, paper insulation subter- 
 ranean cable 4 
 
 Approved types of paper insulation — 
 
 Submarine cable '4 
 
 Subterranean cable 4 
 
 Approved types of rubber insulation — 
 
 Submarine cable 4 
 
 Subterranean cable 4 
 
 Cable- 
 Paper insulation — 
 Armored — 
 
 . Detailed characteristics of all types 8 
 
 Weights and lengths S 
 
 Lead covered, unarmored — 
 
 Lengths and reels , S 
 
 Detailed characteristics of all t j-pes S 
 
 Cable power — 
 
 Usually in stock at supply depots 4 
 
 Special types that have been purchased 8 
 
 Rubber insulation, submarine — 
 
 Detailed characteristics of all types 8 
 
 Lengths ". 8 
 
 Weights 8 
 
 Subterranean — 
 
 Detailed characteristics of all types 8 
 
 Lengths jl 8 
 
 Weights 8 
 
 Color scheme of switchboard cable G 
 
 Commercial value of copper strands 9 
 
 Commercial value of hard drawn copper wii'e 9 
 
 Comparison of various wire gauges 9 
 
 Conductors and insulation, temperature coefficients 9 
 
 Conversion, statute miles, nautical miles, kilometers 4 
 
 Copper wire — 
 
 Carrying capacities for int(>rior wiring 9 
 
 Feet per ohm at various temperatures 4 
 
 Strands, carrying capacity for interior wiring 9 
 
 Ohmic resistance — 
 
 32° F. , 59° F. , G8° F 4 
 
 77° F., 122° F., 167° F 4 
 
 Resistance per pound, various sizes 4 
 
 Data pertaining to Seattle-Si tka caltle when laid 11 
 
 Depth to set aerial line poles in- ground 5 
 
 Desired dimension of wooden poles 5 
 
 Do 8 
 
 Dimensions and weights of cedar poles 8 
 
 Do 8 
 
 Dimension of standard cross arms 5 
 
 Do 8 
 
 Dimension, weight, and length of ])ure c()|>]K'r wire 4 
 
 Faetora for logaritliinic law for rc(hi(iiig compounds to ()((° F 4 
 
 Gal vani/.ed -iron wire, circular mils, area, weight, resistance, break- 
 ing strength, lengths 8 
 
 Ilarfl-drawn c()p|)er wire, weight, resistance, tensile etrengtli, 
 
 lengths 8 I 8 1 
 
 See Chap. 8, p. 1, for alphabetical UnI o( all Signal Corps apparatus and supplies. 
 
 (534)
 
 Subject Index. 
 
 25 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Cliap- 
 
 ter 
 page 
 
 No. 
 
 lablos — Continued. 
 
 Internal resistance of various typ>e8 of batteries f) 
 
 Lead sleeves for cable splicing I 4 
 
 Logarlt hmic law, temperature coeflicients i 4 
 
 Mils diameter of sizes in B. & S. , and B. W. G . gauges i 8 
 
 Miscellaneous in format ion 9 
 
 Number and location of submarine cables installed 9 
 
 Nimaber of cable pairs required for battery feed, common battery ! 
 
 telephone systems 6 
 
 Power cable usually in stock at supply depots 4 
 
 Properties of mcsenger st rand 8 
 
 Properties of various sizes of messenger strand o 
 
 Ratings of chloride accumulators 1 
 
 Resistance of li(juid conductors 9 
 
 Resistance of pure copper wire at 75° F 4 
 
 Sizes and ratings of storage batteries 1 
 
 Specific and relative resistance and relative conductivity of con- 
 ductors 9 
 
 Temperature coefficients — 
 
 For copper, difference in degrees 11 
 
 Of various metals .* 9 
 
 Okonite, Halurshaw, Safety and Bishop compounds 4 
 
 Standard Underground rubber " D " and Kerite 4 
 
 To reduce copper to 60° F 4 
 
 Tensile strength of copper wire 9 
 
 Units of resistance 9 
 
 Weights and resistance of 18 per cent German silver wire 8 
 
 Tagging cables in manholes. 4 
 
 Tank, circular, to determine capacity 9 
 
 Target range signaling systems: 
 
 Buzzer and buzzer-annunciator systems 7 
 
 ,Care of 10 
 
 Classes defined 7 
 
 Distribution boxes 7 
 
 General 7 
 
 .Installation of outlet boxes, types 2 and 3 systems 
 
 Latest installation of buzzer and strap keys 
 
 Location of annunciator, master switch, and distributing box 7 
 
 Location of outlet boxes 7 
 
 Maintenance inspection 10 
 
 Maintenance of dry batteries 10 
 
 Maintenance test 10 
 
 Manhole cover support 
 
 Manhole Tisually used 
 
 Master switches 
 
 Military drills on range 
 
 Original installation of buzzer and strap key 
 
 Portable anemometer 
 
 Protect cable from rodents 7 
 
 Push button and outlet boxes 7 
 
 Range officer's station - 
 
 Requisitions for maintenance supplies. {See " Requisitions.") 
 Records — 
 
 Component parts listed 7 
 
 How prepared 7 
 
 Location of duct line and trenched cable 10 
 
 Offices furnished 
 
 Required 
 
 Signal Corps forms used 
 
 Upkeep of 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (535)
 
 26 
 
 Subject Index. 
 
 Subjects. 
 
 -Continued. 
 
 Target range .signaling system- 
 Semiannual inspection 10 
 
 Separate and d iminishing cable? 7 
 
 Source of power for operating buzzor and buzzer-annunciator 
 
 systems 7 
 
 Target range junction box 7 
 
 Through circuits 7 
 
 Tools for maintenance purposes 10 
 
 Type 1 range, telephone box - . . 7 
 
 Tj'pea defined - 7 
 
 Use of can terminal 7 
 
 Use of sewer flush pipes 7 
 
 WTien range is telephonically connected to post telephone system . 7 
 
 Wiring at butts 7 
 
 Technical equipment issued by the Signal Corps, alphabetically ar- 
 ranged enumeration 8 
 
 Telegraph induction set 2 
 
 Duplex operation 2 
 
 Instructions for operating 2 
 
 Theory of 2 
 
 To use as a closed-circuit telegraph set 2 
 
 Telegraph lines: 
 
 Blavier test for location of leaks ! . . 9 
 
 Common faults encountered 9 
 
 Effect of poor ground connection 9 
 
 Instniments for locating faults 9 
 
 Location of faults 9 
 
 To determine nature of fault and approximately locate 9 
 
 To increase the working value.-. 9 
 
 Telegraph switchboards and repair parts 8 
 
 Telegraphy, Morse 2 
 
 Adjustment — 
 
 Feeling for a distant station : 2 
 
 For maximiun strength 2 
 
 Of apparatus I 2 
 
 Of sounders ! 2 
 
 Closed circuit system 2 
 
 Duplex — 
 
 Artificial line 2 
 
 Balancing the polar duplex 2 
 
 Battery type 2 
 
 Bridge type 2 
 
 Differential relay, requirements 2 
 
 Double current 2 
 
 Essential elements 2 
 
 Polar- 
 Essential elements 2 
 
 Operation of 2 
 
 The pole changer 2 
 
 Single current , or Steams 2 
 
 Telegraphy 2 
 
 The polar relay 2 
 
 Transmitter 2 
 
 W. U . pole changer 2 
 
 Keys employed 2 
 
 Lightning arresters 2 
 
 Office equipment 2 
 
 Office Hwil ch 2 
 
 On short submarine cables 2 
 
 Open circuit system 2 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (530) 
 
 trr 
 page 
 No.
 
 Subject Index. 
 
 27 
 
 Subjects. 
 
 Telegraphy, Morse — Continued. 
 
 Over submarine rabies. {See Cables, submarine.) 
 
 Power for operating system 
 
 Relays 
 
 Repeaters 
 
 Closed circuit repeating open circuit signals and vice versa. 
 
 Milliken 
 
 Test for operation 
 
 Weiny 
 
 Weiny , operation described 
 
 Sounders 
 
 Switchboards 
 
 Terminal switchboard and battery arrangement .' 
 
 Wet-weather effects 
 
 Telephones: 
 
 Cable testing 
 
 Camp 
 
 And repair parts for 
 
 Battery employed 
 
 First and later models, to di.stingui,<^h 
 
 Hand-set 
 
 Hook switch 
 
 How constructed 
 
 Its use 
 
 Do.. 
 
 Screw driver with each instrument 
 
 Common batterj' — 
 
 And repair parts for 
 
 Dean, Wheatstone bridge circuit described 
 
 General 
 
 Desk 
 
 Common batterj- — 
 
 Garford circuits 
 
 North Electric circtuts 
 
 Local batter}^ 
 
 Garford circuits 
 
 Field, and repair parts for 
 
 Local battery — 
 
 And repair parts for 
 
 Typical circuit t raced 
 
 Switchboard location 
 
 Theory of 
 
 Types of instruments 
 
 Various types and repair parts for 
 
 Wall 
 
 Common battery — 
 
 Circuits traced 
 
 North Electric circuits 
 
 Siunter circuits 
 
 Western Electric circuits 
 
 Local batten.'^ 
 
 Garford circuits 
 
 Sumter circuits 
 
 Telephone ."switchboards. (See Switchboards, telephone.) 
 Telephone systems. (See Post telephone systems.) 
 Telephony : 
 
 Common battery operation explained 
 
 Common battery transmission 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and 
 
 2 
 
 4 
 
 2 
 
 o 
 
 2 
 
 7 
 
 2 
 
 25 
 
 4 
 
 45 
 
 3 
 
 23 
 
 8 
 
 80 
 
 3 
 
 24 
 
 3 
 
 24 
 
 3 
 
 26 
 
 3 
 
 26 
 
 3 
 
 24 
 
 3 
 
 23 
 
 9 
 
 28 
 
 3 
 
 26 
 
 8 
 
 78 
 
 G 
 
 8 
 
 3 
 
 17 
 
 3 
 
 20 
 
 3 
 
 23 
 
 3 
 
 23 
 
 3 
 
 16 
 
 3 
 
 16 
 
 8 
 
 80 
 
 8 
 
 79 
 
 3 
 
 13 
 
 6 
 
 1 
 
 3 
 
 4 
 
 3 
 
 12 
 
 8 
 
 78 
 
 3 
 
 21 
 
 3 
 
 19 
 
 3 
 
 22 
 
 3 
 
 . 19 
 
 3 
 
 18 
 
 3 
 
 1 
 
 3 
 
 14 
 
 3 
 
 6 
 
 3 
 
 6 
 
 supplies. 
 
 (537)
 
 28 
 
 Subject Index. 
 
 Subjects- 
 
 page 
 
 No. 
 
 Telephony — Continued. 
 
 Condenser defined 
 
 Difference between local and common battery transmission 
 
 Electromagnetic induction 
 
 Electromagnetism 
 
 Electrostatic induction 
 
 How articulate speech is transmitted 
 
 Laws of magnetic induction 
 
 Local battery transmission 
 
 Lines of force defined 
 
 Magnetic force 
 
 Magnetic induction 
 
 Magnetism 
 
 Operation explained 
 
 Automatic circuit opener 
 
 Sizes furnished by the Signal Corps 
 
 Receiver 
 
 Ringer 
 
 Operation 
 
 Resistance of windings 
 
 The induction coil 
 
 The magneto 
 
 Theory of 
 
 The transformer 
 
 To make a magnet 
 
 Transmitter 
 
 Telephone 
 
 Telescopes, description of each type supplied by the Signal Corps. . . 
 
 Temperature coefficient , 
 
 Conductor and insulation 
 
 Of various metals 
 
 Temperature effects on storage batteries 
 
 Terminal boxes: 
 
 First metal ones 
 
 General 
 
 Metal, terminal strips used 
 
 Metal, 1915 model 
 
 Terminal strips, standard 
 
 Terminals, for cable, fused and unfused 
 
 Tests, cable: 
 
 After cables installed, duties of tester 
 
 After installation and being spliced 
 
 After installation, correction for leads to instruments 
 
 Blavier, for locating leaks and grounds 
 
 Cable-t4?sting telephone 
 
 Capacity measurements when cable exceeds 100 miles in length. 
 
 ComV)ined shunt and key 
 
 CondenwT, standard 
 
 Cond uctor resisfance 
 
 Conversion table, statute miles, nautical miles, kilometers 
 
 Copper wire — 
 
 Feet yxjr ohm at various temperatures 
 
 Ohmic re.sistance — 
 
 32° F.,50° F., 68°F 
 
 77° F., 122° F., 167° F 
 
 Ohms per pound — 
 
 32*" F., 59° F., 68° F 
 
 77° F., 122° F., 167° F 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and 
 
 supplies. 
 
 (538)
 
 Subject Index. 
 
 29 
 
 Subjects. 
 
 Tests, cable — Continued. 
 
 Data relative to oompouiul — 
 
 Kerite 
 
 Safety 
 
 Dimensioji, weight, and length of piire copper wire 
 
 Electrical instrument case, contents 
 
 Electrolysis, to detect 
 
 Electrostatic capacity 
 
 Factor used to change statute miles to nautical miles 
 
 Factory tests 
 
 Sample of record 
 
 Do 
 
 Fisher cable testing set, No. 2 — 
 
 Description of , 
 
 Measuring capacity wath 
 
 Measuring conductor resistance with 
 
 Measiuing insulation with 
 
 Murray loop test with 
 
 Special Wheatstone bridge used with 
 
 Varley loop test with 
 
 Formula for reducing copper resistance to 60° F 
 
 Identification of conductors 
 
 Insulation — 
 
 Measurements, author's explanation of principle involved . . 
 
 Resistance 
 
 To compute values 
 
 To determine galvanometer constant 
 
 With telephone receiver 
 
 LocatioTi of — 
 
 Break in conductor, using improvised apparatus 
 
 Cross by means of the voltmeter 
 
 Fault with ohmeter, in multiple conductor cable 
 
 Ground — 
 
 HaAing a high resistance, with improvised apparatus 
 
 Single conductor cable, with improvised apparatus. ... 
 
 With exploring coil 
 
 With improvised apparatus , 
 
 All conductors grounded , 
 
 Conductor grounded at two places 
 
 Explanation of principle 
 
 Logarithmic law — 
 
 Factors for reducing compounds to 60° F , 
 
 P'or reducing insulation resistance to 60° F., formula 
 
 Temperature coefficients , 
 
 Variation of insulation resistance with temperature change. . 
 Long submarine cables. (See '"Cables, submarine, long.'') 
 
 Method of making testing after installation 
 
 Murray and Varley loop tests 
 
 Notes on capacity measurements 
 
 Ohmeter, model 1904 
 
 Ohmic resistance — 
 
 Comparison of ohmeter with WTieatstone bridge 
 
 Directions for using ohmeter 
 
 With voltmeter and ammeter 
 
 One hundred thousand ohm box, standard 
 
 Points for the cable tester 
 
 Recommended treatises on tests 
 
 Record readings obtained on leads 
 
 Reflecting D'Arsonval galvanometer 
 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 4 
 
 11 
 11 
 11 
 11 
 11 
 11 
 11 
 4 
 4 
 
 4 
 4 
 4 
 4 
 9 
 
 9 
 9 
 9 
 
 9 
 9 
 9 
 9 
 9 
 9 
 9 
 
 4 
 
 4 
 4 
 4 
 
 4 
 
 9 
 
 11 
 
 4 
 
 4 
 4 
 9 
 4 
 -1 
 11 
 4 
 4 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 46581°— 17 
 
 -35 
 
 (539)
 
 30 
 
 Subject Index. 
 
 Subjects. 
 
 Chap- 
 ter 
 
 ^l 
 
 Tests, cable — Continued. 
 
 Resistance of pure copper wire at 75° F 
 
 Service testing battery 
 
 Special instruments used 
 
 Specimen of record 
 
 Standard cable constants 
 
 Temperature coefficients — 
 
 Kerite and Standard Underground Co. 's rubber '" D " 
 
 Okonite, Habirshaw, Safety, and Bishop compounds 
 
 The double scale voltmeter 
 
 The faultfinder 
 
 To eliminate earth current effects 
 
 To identify cable in trench by means of an exploring coil 
 
 To measure length of single conductor cable 
 
 To reduce copper to 60° F 
 
 Voltammeter, portable, issued by the Signal Corps 
 
 With improvised apparatus 
 
 With post-testing voltmeter , 
 
 With the megger 
 
 With WTieatstone bridge — 
 
 Graphical demonstration 
 
 Post-office form of instrument 
 
 Precautions in operating 
 
 Principle of instrimient explained 
 
 Simplest measurement 
 
 Tests, miscellaneous: 
 
 For operation of telegraph repeaters 
 
 Instruments for locating faults in telegraph lines 
 
 Location of crosses or leaks in telegraph Lines with the wire bridge . 
 
 Location of faults in telegraph lines 
 
 Of electrolyte for storage batteries 
 
 Ohmic resistance of telegraph line — 
 
 Practical connections 
 
 With voltmeter and ammeter 
 
 To approximately locate faults in telegraph linos 
 
 With voltammeter — 
 
 To measure internal resistance of a battery 
 
 W'ith voltmeter — 
 
 Difference of potential 
 
 Resistance of 3,000 to 250,000 ohms 
 
 Resistance less than 3,000 ohms 
 
 Resistance, using a known resistance 
 
 To measure ciu-rent 
 
 To measure internal resistance of a battery 
 
 Voltage of a number of cells of a battery, connected in series. . 
 With Wheatstone bridge, to measure resistance of telegraph line. . . 
 
 Toggle bolts 
 
 Tool chests: 
 
 Aeroplane, and contents 
 
 Cable splicer's, and contents 
 
 Construction, and contents 
 
 Electrical engineer's, and contents 
 
 Mechanic's, and contents .^ 
 
 Pipe fitter's, and contents 
 
 Post, and contents 
 
 Tool bag, service, and contents 
 
 Tool kit, inspector's pocket, and contents 
 
 Tools: 
 
 For maintenance purposes 
 
 Special 
 
 Transfer of cable from one reel to another 
 
 4 
 4 
 11 
 4 
 4 
 
 4 
 4 
 9 
 9 
 
 11 
 9 
 
 11 
 4 
 9 
 9 
 
 10 
 
 10 
 
 9 
 9 
 9 
 
 9 
 9 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (540)
 
 Subject Index. 
 
 31 
 
 Subjects. 
 
 Chap- 
 ter 
 
 Transformer, principle of 
 
 Transmitter: 
 
 Automatic, for use on long submarine cables 
 
 Duplex telegraphy 
 
 Tape perforators 
 
 Telephone 
 
 Telephone, operation 
 
 Transportation in the field 
 
 Treatment of storage batteries when they are to stand idle. 
 
 Tripod aerial line construction 
 
 Trucks, lance, how used 
 
 Tungsten type A battery 
 
 Internal resistance and weight 
 
 Type numbers for cable, system of assigning 
 
 Types of conduit for underground cable systems 
 
 Types of telephones 
 
 U. 
 
 Underground installation of cable: 
 
 Conduit construction 
 
 Procedure 
 
 Trenching 
 
 Two methods 
 
 Units of resistance 
 
 V. 
 
 \'arley and Murray loop tests 
 
 Voltaic cell 
 
 Voltammeter, portable, issued by the Signal Corps. 
 ^'oltmeter: 
 
 Post testing 
 
 To locate a cross 
 
 ''Volt drops," defined 
 
 Volt defined 
 
 9 
 1 
 9 
 
 10 
 9 
 1 
 1 
 
 W. 
 
 "Wagon, instrument, how used 
 
 Watt-hour meter, installed in connection with post telephone systems. . 
 
 Weatherproof wire '. 
 
 Weiuey telegraph repeaters 
 
 Operation described 
 
 Wheatstone bridge: 
 
 Graphical demonstration 
 
 Post-otfice form of instrument 
 
 Precautions in operating 
 
 Principle explained 
 
 Simplest measurement 
 
 Used at Alaskan cable offices 
 
 Wire (sec also Tables, tests, etc.): 
 
 Aluminum, carrj-ing capacities 
 
 And insulation , temperature coefficients 
 
 Bridle. 
 
 Buzzer 
 
 Copper — 
 
 Carrying capacities for interior wiring 
 
 Hard dra\\ni — 
 
 Advantages for line construction 
 
 Commercial values ! 
 
 See Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 9 
 9 
 9 
 c 
 
 9 
 11 
 
 9 
 9 
 
 (541^
 
 32 
 
 Subject Index, 
 
 Subjects. 
 
 Chap- 
 ter 
 No. 
 
 Chap- 
 ter 
 
 page 
 No. 
 
 Wire — Continued . 
 
 Copper — Continued . 
 
 Soft, Matthiessen 's formula 
 
 Strands — • 
 
 Carrying capacities for interior wiring 
 
 Commercial standards 
 
 Tensile strength 
 
 Cross connecting 
 
 Designate size in mils 
 
 Field 
 
 To splice 
 
 Fixture 
 
 P'or all purposes, enumeration 
 
 For radio telegraph installations 
 
 Galvanized iron 
 
 Characteristics 
 
 Hard-drawn copper 
 
 Characteristics 
 
 House 
 
 Inside twisted pair 
 
 Inside twisted triple conductor 
 
 Lengths and resistance of 18 per cent German silver. 
 
 Manner of listing amounts of various types 
 
 Miscellaneous 
 
 Office 
 
 Outside distributing, copper clad 
 
 Outside twisted pair 
 
 Pot head 
 
 Relative to manufacture , 
 
 Rubber-covered 
 
 Used in field operations — 
 
 Description 
 
 In emergencies 
 
 Useful constants and formulae 
 
 Weatherproof 
 
 Wire carrier 
 
 Wire carrier and hand reel, how used 
 
 Wire carts, description and how used 
 
 Type " L, " extra and maintenance parts 
 
 Wire gauges 
 
 Commonly used 
 
 Comparison of various types 
 
 Law of the Brown & Sharpe gauge 
 
 Wire pike 
 
 Wooden poles, dimensions 
 
 32 
 
 9 
 
 36 
 
 9 
 
 35 
 
 9 
 
 34 
 
 8 
 
 83 
 
 8 
 
 81 
 
 8 
 
 85 
 
 8 
 
 85 
 
 8 
 
 83 
 
 8 
 
 82 
 
 8 
 
 82 
 
 8 
 
 85 
 
 8 
 
 85 
 
 8 
 
 84 
 
 8 
 
 84 
 
 8 
 
 83 
 
 8 
 
 82 
 
 8 
 
 82 
 
 8 
 
 87 
 
 8 
 
 86 
 
 8 
 
 86 
 
 8 
 
 86 
 
 8 
 
 84 
 
 8 
 
 84 
 
 8 
 
 83 
 
 8 
 
 81 
 
 8 
 
 83 
 
 9 
 
 27 
 
 9 
 
 28 
 
 9 
 
 38 
 
 8 
 
 84 
 
 8 
 
 87 
 
 9 
 
 27 
 
 9 
 
 26 
 
 8 
 
 33 
 
 9 
 
 32 
 
 9 
 
 33 
 
 9 
 
 33 
 
 9 
 
 33 
 
 8 
 
 89 
 
 8 
 
 49 
 
 Sec Chap. 8, p. 1, for alphabetical list of all Signal Corps apparatus and supplies. 
 
 (542)
 
 ILLUSTRATION INDEX. 
 
 niustmtioDs. 
 
 No. 
 
 Aerial line construction: 
 
 Arrangement of tackle 
 
 Attaching brackets to poles 
 
 Cable box 
 
 Changing direction of messenger 
 
 Deadman and anchor rod 
 
 Double arming poles 
 
 Fence post lines 
 
 Gale crossing 
 
 Guard wires 
 
 Guying— 
 
 Across road 
 
 At comers 
 
 At curves 
 
 At road crossings 
 
 Installation effused can terminal 
 
 Line transposition 
 
 Long Spans — 
 
 Construction of saddles 
 
 Methods of terminating 
 
 Additional 
 
 Messenger strand — 
 
 Deadending 
 
 Guying 
 
 Supports 
 
 Through bolt type 
 
 Method of guying to rock 
 
 Pole brace 
 
 Pole steps 
 
 Preparation of poles 
 
 Shims and clamps 
 
 Splicing messenger strand 
 
 Terminal — 
 
 Can — 
 
 Fused 
 
 Unfused 
 
 Pole 
 
 Unfused — 
 
 Installed 
 
 Installation of 
 
 Test station 
 
 Tripod lines 
 
 Over ice 
 
 Tying hard-drawn copper wire to insulators 
 Tying and splicing iron and steel wires . . 
 Wires on insulators 
 
 Corner pole 
 
 Alaskan tripod lines 
 
 Over ice 
 
 Anchors, screw, composition 
 
 Arresters, lightning, telephone 
 
 Moisture-proof type 
 
 5-27 
 5-- 3 
 5-4 
 5-28 
 5-10 
 5-2 
 5-34 
 5-35 
 5-14 
 
 5-13 
 5-7 
 5-9 
 5-8 
 5-29 
 5-19 
 
 5-39 
 5-38 
 5-40 
 
 5-21 
 5-22 
 5-25 
 5-26 
 5-11 
 5-12 
 5-6 
 5-1 
 5-23 
 5-24 
 
 5-30 
 5-31 
 5-5 
 
 5-33 
 5-32 
 5-20 
 5-36 
 5-37 
 5-17 
 5-18 
 5-15 
 5-16 
 5-36 
 5-37 
 8-25 
 6-1 
 6-2 
 
 P.L. 
 P.L. 
 
 P.L 
 P.L. 
 
 (543) 
 
 83
 
 34 
 
 Illustration Index. 
 
 No. 
 
 Illustrations. 
 
 C^ 
 
 B. 
 
 Bag, tool, service 
 
 Battery cells connected: 
 
 In multiple 
 
 In series 
 
 Battery cells: 
 
 Edison primary type V 
 
 Fuller .' 
 
 Gravity 
 
 Battery dry cells, standard sizes 
 
 Battery reserve dry cells, standard sizes 
 
 Battery: 
 
 Service, testing, used in cable testing 
 
 Storage — ■ 
 
 Assembly of parts 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Charging for telegraph systems 
 
 Oiloride 
 
 Gould 
 
 Stand for 
 
 Do 
 
 Willard 
 
 1 cell, for relays and sounders of telegraph systems . . 
 
 Bell, extension, loud ringing 
 
 Blavier test, location of grounds 
 
 Bridge, Wheatstone: 
 
 Graphical demonstration 
 
 Post-office form 
 
 Bridle rings, enamel coaled 
 
 Box: 
 
 Cable . . 
 
 Metal, terminal, 1915 model 
 
 100,000 ohm, standard, used in cable testing 
 
 Buzzers connected to a telegraph line 
 
 Buzzer, connector, type A 
 
 Buzzer: 
 
 Field, simplified circuit 
 
 With interrupter 
 
 With transmitter 
 
 With transmitter and interrupter 
 
 Service 
 
 Circuits 
 
 Dismantled 
 
 Sending and receiving Morse signals, circuits employed 
 
 8--21 
 
 1--8 
 1-7 
 
 1--6 
 1-5 
 1--4 
 1--2 
 1--3 
 
 4--34 
 
 1-A 
 1--B 
 1-C 
 
 1--D 
 1--E 
 1--F 
 2--25 
 1--10 
 1-12 
 1-13 
 1-14 
 1-11 
 2-26 
 8-3 
 9-31 
 
 9-20 
 9-19 
 8-24 
 
 5-4 
 8-1 
 4-31 
 3-29 
 8-29 
 
 3-25 
 3-26 
 3-27 
 3-28 
 3-31 
 3-30 
 3-32 
 3-33 
 
 68 
 
 13 
 13 
 
 11 
 9 
 8 
 5 
 6 
 
 43 
 
 20 
 20 
 20 
 20 
 20 
 20 
 30 
 22 
 24 
 26 
 27 
 23 
 30 
 23 
 24 
 
 15 
 14 
 72 
 
 9 
 21 
 41 
 29 
 
 P.L. 
 P.L. 
 P.L. 
 
 P.L 
 
 P.L 
 
 P.L 
 
 Cable: 
 
 Box 
 
 Grips, improvised and manufactured 
 Long submarine, switchboard used . 
 
 Power 
 
 Pulling, position of reel 
 
 Racking in manholes 
 
 Reel, with lagging 
 
 5-4 
 4-15 
 11-1 
 4-5 
 
 4.-14 
 
 4-16 
 4-6 
 
 (644)
 
 Illustration Index. 
 
 35 
 
 Illustrations. 
 
 No. 
 
 .S 
 
 Cable — Continued. 
 Splicing — 
 
 Paper insulation cable 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Construction of pothead 
 
 Rubber insulation, submarine 
 
 Sleeve used in splicing type 251 cable 
 
 Submarine — 
 
 Paper insulation 
 
 Rubber insulation 
 
 Subterranean — 
 
 Paper insulation 
 
 Rubber insulation 
 
 System — 
 
 Conduit ends 
 
 Connecting underground to aerial cable 
 
 Diagrammatic 
 
 Distribution 
 
 Manhole 
 
 Removable forms 
 
 With concrete top 
 
 Testing {Also see Tests) — 
 
 Capacity 
 
 Coefficients for reducing insulation resistance to 60° F 
 
 Copper resistance — 
 
 Murray and Varley loop, simplified diagram 
 
 Connections 
 
 Curve sheets for Jona and other graphs 
 
 D'Arsonval reflecting galvanometer, wall type 
 
 Electrostatic capacity, simplified diagram 
 
 Fisher cable testing set, No. 2 
 
 Arrangement of apparatus 
 
 Connections 
 
 Wheatstone bridge arrangement 
 
 Galvanometer constant 
 
 Insulation 
 
 Insulation resistance, simplified diagram 
 
 Jordan and Schonau's modification of earth overlap test, diagram of connections 
 Location of grounds 
 
 Clark's potential tests- 
 Connections 
 
 Connections at distant station 
 
 Earth overlap test, diagrammatic 
 
 Prof. Kennelly's method, copper resistance connections 
 
 Simple loop test, connections 
 
 Ohmeler, theory of 
 
 Plan of testing table, Seattle cable office 
 
 Resistance measurement with ohmeter 
 
 Shunt, Ayrlon, universal 
 
 Connections 
 
 4--18 
 4--19 
 4--20 
 4--21 
 4-22 
 4--23 
 4--24 
 4--25 
 4-26 
 4-27 
 4--28 
 4--17 
 4--29 
 
 4-- 4 
 4-- 3 
 
 4-40 
 4-43 
 
 1-34 
 1-26 
 1-42 
 1-21 
 1-32 
 1-28 
 1-30 
 1-31 
 1-29 
 4-38 
 4-39 
 1-33 
 1-43 
 
 1-39 
 
 1-40 
 1-41 
 1-38 
 1-37 
 4-41 
 1-35 
 4-42 
 1-23 
 1-24 
 
 4-2 3 
 4-1 2 
 
 4-8 
 4-13 
 4-7 
 4-12 15 
 4-9 12 
 4-11 14 
 4-10 13 
 
 (545)
 
 36 
 
 Illustration Index. 
 
 Illustrations. 
 
 Cable — Continued. 
 Testing — Continued. 
 
 Shunt, simplified diagram 
 
 Special instruments used 
 
 Telephone 
 
 Circuits 
 
 Test room connections, U. S. A. T. Bumside .... 
 
 Thompson reflecting galvanometer 
 
 Wheatstone bridge, for measuring conductor resistance 
 Camp telephone: 
 
 And circuits 
 
 Dismantled 
 
 Switchboard 
 
 Can, terminal, fused 
 
 Installation of 
 
 Unfused 
 
 Unfused, installed 
 
 Unfused, installation of 
 
 Carrier, wire 
 
 Cart, signal 
 
 Case: 
 
 Electrical instrument 
 
 Reagent 
 
 Cells, battery: 
 
 Connected in multiple 
 
 Connected in series 
 
 Dry- 
 Standard sizes 
 
 Reserve, standard sizes 
 
 Edison primary, type V 
 
 Fuller 
 
 Gravity 
 
 Chests, tool: 
 
 Cable splicer's 
 
 Construction 
 
 Eleclrical engineer's 
 
 Mechanic's, No. 2 
 
 Pipe fitter's 
 
 Post • 
 
 Closed circuit telegraph system 
 
 Coefficients for reducing insulation resistance lo 60° F 
 
 Condenser, standard, used in cable testing 
 
 Connector, buzzer, type A 
 
 Cook protector, details 
 
 Cords, standard: 
 
 Field equipment 
 
 Switchboard — 
 
 Connecting 
 
 Transmitter and receiver 
 
 Telephone, post and Artillery type 
 
 Terminals for 
 
 Conduit ends 
 
 D'Arsonvai reflecting galvanometer, wall type 
 
 Distributing frame 
 
 Duplex telegraphy. (See Telegraphy.) 
 Dynamolor, ringing 
 
 No. 
 
 1--8 
 1--7 
 
 1- 
 
 . 1- 
 . 1- 
 
 :■ 1- 
 1- 
 
 -2 
 -3 
 
 -6 
 -5 
 -4 
 
 8--18 
 8--17 
 8--16 
 8--15 
 8--19 
 8--20 
 2--1 
 4-43 
 4-33 
 8-29 
 6-- 8 
 
 8-- 6 
 
 37 
 
 8-- 5 
 
 36 
 
 8-- 7 
 
 38 
 
 8-- 9 
 
 40 
 
 4-- 8 
 
 11 
 
 11--21 
 
 32 
 
 6-- 3 
 
 5 
 
 6--38 
 
 -.a 
 5;= 
 
 ..ft 
 
 P.L 
 
 P.L 
 P.L 
 P.L 
 P.L 
 
 P.L 
 
 P.L 
 
 42 
 
 P.L 
 P.L 
 P.L 
 
 P.L 
 
 (546)
 
 Illustration Index. 
 
 37 
 
 Illastrations. 
 
 No. 
 
 & "3 2 
 
 E. 
 
 Electricalinslniment case 
 
 Exploring coil, test to locate ground 
 Extension bell, loud ringing .... 
 
 F. 
 
 8--14 
 9--24 
 8-- 3 
 
 9--32 
 
 Faultfinder 
 
 Fence post lines: 
 
 Aerial lines 
 
 Gate crossing 
 
 Field buzzers: 
 
 Connected to a telegraph line . 
 
 Simplified circuits 3-25 
 
 With interrupter 3--26 
 
 With transmitter 
 
 With transmitter and interrupter 
 
 Frame, distributing 
 
 Front Royal Remount Depot: 
 
 Cordless switchboard 
 
 Circuits 
 
 Open 
 
 Fuses, standard types 
 
 G. 
 
 Galvanometers: 
 
 Connections for — 
 
 Capacity 4-40 
 
 Insulation 4-39 
 
 Obtaining constant 4-38 
 
 D'Arsonval, reflecting, wall type 11-21 
 
 Reflecting, D'Arsonval type 4-30 
 
 Thompson, reflecting 11-20 
 
 5-34 
 5-35 
 
 3-29 
 
 3-27 
 3-28 
 6-3 
 
 6-24 
 6-26 
 6-25 
 8-10 
 
 H. 
 
 Hand receiver, telephone 
 
 3-8 
 
 Hand reel 8-28 
 
 I. 
 
 Induction telegraph set 
 
 Circuits 
 
 Theory of operation 
 
 Inspector's pocket tool kit 
 
 Instrument case, electrical 
 
 Instruments, special, used in testing cable 
 
 Key and shuni used in cable testing 
 
 Key, strap, large 
 
 Key, telegraph. ( See Telegraph. ) 
 Kit, tool, inspector's pocket .... 
 
 Lightning arrester, telephone 
 
 Moisture-proof type 
 
 Lioe construction. ( See Aerial line constniclion.) 
 
 2-27 
 2-29 
 2-28 
 8-22 
 8-14 
 11-25 
 
 4-32 
 8-11 
 
 8-22 
 
 6-1 
 6-2 
 
 P.L 
 
 P.L 
 
 P.L 
 
 f.L 
 
 P.L 
 P.L 
 
 (547)
 
 38 
 
 Illustration Index. 
 
 Illustrations. 
 
 Ohmeter: 
 
 Model 1904 
 
 Resistance measurement 
 
 Test, to locate grounds 
 
 Theory of 
 
 Ohms, 100,000, standard, used in cable testing 
 Open circuit telegraph system 
 
 Fike, wire 
 
 Plug switch and lightning arrester, telegraph 
 
 Portable voltammeler 
 
 Post testing voitmeler 
 
 Polhead for paper insulation cable 
 
 Power cable 
 
 Protector cabinets, for telephone switchboards 
 Protectors: 
 
 Cook, details 
 
 Western Electric, details 
 
 R. 
 
 Reagent case 
 
 Receiver, hand, telephone 
 
 Record of telephone system. (See Telephone systems, record. ) 
 
 Rectifier, mercury arc 
 
 Reel: 
 
 Cable, with lagging 
 
 Hand 
 
 Reflecting galvanometer, D'Arsonval type 
 
 No. 
 
 Line construction material 
 
 Messenger supports 
 
 Long spans in aerial lines: 
 
 Construction of saddles 
 
 Method of terminating 
 
 Method of terminating, additional 
 
 Long submarine-cable testing. {See Cable testing and tests.) 
 Long submarine-cable telegraphy. {See Telegraphy.) 
 
 M. 
 
 Magneto generator, telephone 
 
 Theory of 
 
 Voltage curve 
 
 Manholes: 
 
 For cable system 
 
 Removable forms 
 
 With concrete top 
 
 Material, line construction 
 
 Messenger supports 
 
 Megger 
 
 Mercury arc rectifier 
 
 Morse telegraphy. (See Telegraphy and telegraph systems.) 
 
 Motor generator 
 
 Molding, standard types 
 
 i^i=; 
 
 8-12 
 8-13 
 
 5-39 
 5-38 
 5-40 
 
 3-7 
 3- 5 
 3" 6 
 
 4-9 
 4-11 
 4-10 
 8-12 
 8-13 
 10-1 
 6-35 
 
 6-34 
 8-23 
 
 4-35 
 
 4-42 
 9-22 
 4-41 
 4-31 
 2-2 
 
 8-30 
 2-11 
 9-21 
 10-2 
 4-28 
 4-5 
 6-7 
 
 6-8 
 6-9 
 
 1-9 
 3-8 
 
 6-35 
 
 4-6 
 
 8-28 
 4-30 
 
 40 
 
 P.L. 
 P.L. 
 
 P.L. 
 
 (548)
 
 Illustration Index. 
 
 39 
 
 Illustrations. 
 
 Relay: 
 
 Box, telegraph 
 
 Telegraph, main line 
 
 Ringer, telephone 
 
 Ringing dynamotor 
 
 Rings, bridle, enamel coated 
 
 Repeater, telegraph: 
 
 Circuits for 0. C. and C. C. operation 
 
 Milliken, theory of 
 
 Weiny, theory of 
 
 No. 
 
 zr 
 « s 
 
 S. 
 
 Screw anchor, composition 
 
 Service buzzer 
 
 Circuits 
 
 Dismantled 
 
 Sending and receiving Morse signals, circuits employed . . 
 
 Service testing battery used in cable testing 
 
 Shunt and key used in cable testing 
 
 Shunt, Ayrton, universal 
 
 Connections 
 
 Shunt used in cable testing, simplified diagram 
 
 Signal cart 
 
 Sleeve used in splicing type 251 cable 
 
 Small arms target range signaling systems. (See Target Range.) 
 Sounder, telegraph: 
 
 Mainline 
 
 4-ohm 
 
 Splicing cable. (See Cable splicing.) 
 Standard cords. (See Cords, standard.) 
 
 Standard type of fuses 
 
 Storage battery: 
 
 Assembly of parts 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Chloride 
 
 Gould 
 
 Stand for 
 
 Do 
 
 Willard 
 
 Strap key, large 
 
 Strip, terminal, standard 
 
 Submarine cable. (See Cable, submarine.) 
 Subterranean cable. (See Cable, subterranenan.) 
 Switchboard: 
 
 Cable. (See Switchboard, telephone, forming cable conductors.) 
 
 Camp telephone 
 
 Telegraph — 
 
 Intermediate 
 
 Power connections 
 
 Terminal type 
 
 Telephone — 
 
 Common battery, 50-line visual 
 
 Distributing frame 
 
 2-7 
 2-- 6 
 3--10 
 6--38 
 8-24 
 
 2-16 
 2-14 
 2~1S 
 
 8-25 
 3-31 
 3--30 
 3-32 
 3-33 
 4-34 
 4-32 
 11-23 
 11-24 
 11-22 
 8-4 
 4-29 
 
 2-8 
 2-9 
 
 8-10 
 
 1-A 
 1-B 
 1-C 
 1-D 
 1-E 
 1-F 
 1-10 
 1-12 
 1-13. 
 1-14 
 1-11 
 8-11 
 8-2 
 
 2-10 
 2-13 
 2-12 
 
 8-26 77 
 
 5 
 8 
 
 7 
 
 6-6 
 6-3 
 
 (549)
 
 40 
 
 Illustration Index. 
 
 Illustrations. 
 
 No. 
 
 Switchboard — Continued. 
 Telephone — Continued. 
 
 Forming cable conductors 
 
 Do 
 
 Do 
 
 Do 
 
 Do 
 
 Lamp line and lamp supervisory signals — 
 
 Circuits 
 
 Inoperation 
 
 Principal circuits 
 
 Test circuits 
 
 Local battery type, cordless 
 
 Circuits 
 
 Open 
 
 Local battery type — 
 
 15 line 
 
 15 line, circuits 
 
 50 line 
 
 50 line, circuits 
 
 Locking relays, circuits 
 
 Power type No. 1 
 
 Power type No. 4 
 
 Protector cabinet 
 
 Visual, circuits 
 
 Visual line signal, lamp supervisory cord circuit 
 
 Visual night bell circuit 
 
 50-100 line, and protector cabinet 
 
 200 line night bell circuit 
 
 200-line, generator drop circuit 
 
 Switchboard used with long submarine cable 
 
 System, cable. (See Cable system.) 
 
 6-28 
 6-27 
 6-29 
 6-30 
 6-31 
 
 6-15 
 6-17 
 6-19 
 6-16 
 6-24 
 6-26 
 6-25 
 
 6-20 
 6-21 
 6-22 
 6-23 
 6-18 
 6-36 
 6-37 
 6-7 
 6-10 
 6-14 
 6-11 
 6-32 
 6-12 
 6-13 
 11-1 
 
 29 
 28 
 29 
 30 
 31 
 
 16 
 17 
 19 
 17 
 25 
 26 
 26 
 
 20 
 21 
 23 
 24 
 18 
 40 
 41 
 11 
 13 
 15 
 13 
 34 
 14 
 14 
 5 
 
 P.L. 
 
 Target range: 
 
 Outlet box, round pattern 
 
 Outlet box, 1915 model 
 
 Pushbutton 
 
 Type No. 1 system 
 
 Outlet box 
 
 Telephone box 
 
 Type No. 2 system — - 
 
 Using diminishing cable 
 
 Using separate cables to butts . . . 
 
 Type No. 3 system 
 
 Types Nos. 2 and 3 systems — 
 
 Distributing box 
 
 Installation of strap key and buzzer 
 
 Manhole 
 
 Master switch 
 
 Outlet box, installation of 
 
 Through circuits 
 
 Target range junction box ... . 
 
 Use of can terminal 
 
 Telegraph induction set 
 
 Circuits 
 
 Theory of operation 
 
 7-- 2 
 7-3 
 7-1 
 7-4 
 7-5 
 7-6 
 
 7-7 
 7-8 
 7-9 
 
 7-14 
 7-15 
 7-12 
 7-11 
 7-10 
 7-16 
 7-13 
 7-17 
 2-27 
 2-29 
 2-28 
 
 P.L 
 
 (660)
 
 Illustration Index. 
 
 41 
 
 No. 
 
 Illustrations. 
 
 
 Telegraph systems: 
 
 Closed circuit 
 
 Key, closed circuit — 
 
 Legless type 
 
 Leg type 
 
 Key, open circuit, leg type 
 
 Main line sounder 
 
 Opencircuit 
 
 Plug switch and lightning arrester 
 
 Relay- 
 Box 
 
 Mainline 
 
 Repeater - 
 
 Circuits for 0. C. and C. C. operation 
 
 Milliken, theory of 
 
 Weiny, theory of 
 
 Switchboard — 
 
 Intermediate 
 
 Power, connections 
 
 Terminal type 
 
 4-ohm sounder 
 
 Telegraphy, duplex: 
 
 Battery, duplex 
 
 Bridge, theoretical connections 
 
 Polar, circuits 
 
 Polarized relay, theoretical connections 
 
 Pole changer 
 
 Single current — 
 
 Theoretical connections 
 
 Do 
 
 Do 
 
 Telegraphy over submarine cables: 
 
 Actual connections at Alaskan cable offices 
 
 Current supply at Seattle terminus of Seattle-Sitka cable 
 
 Cuttriss automatic transmitter, connections 
 
 Double-current telegraphy 
 
 Key used by the Signal Corps 
 
 3-station connections 
 
 large siphon recorder 
 
 Connections 
 
 Morse open circuit connections 
 
 Polarized relay set, connections 
 
 Single current, open circuit, repeater sets 
 
 Simplified diagram of connections 
 
 Siphon recorder - 
 
 Duplex and simplex systems, connections 
 
 Muirhead's, arrangement of circuit 
 
 Siphon recorder set, simplified connections 
 
 Siphon recorder — 
 
 Muirhead, vibrator circuits 
 
 To operate motor from electric lighting circuit . . . 
 
 Small siphon recorder 
 
 Telegraphy, power: 
 
 Charging storage battery 
 
 Current for relay and sounders 
 
 Telephone: 
 
 Cable testing 
 
 Circuits 
 
 2-1 
 
 2-4 
 2-3 
 
 2-5 
 2-8 
 2-2 
 2-11 
 
 2-7 
 2-6 
 
 2-16 
 2-14 
 2-15 
 
 2-10 
 2-13 
 2-12 
 2-9 
 
 2-22 
 2-23 
 2-21 
 2-20 
 2-24 
 
 2-17 
 2-18 
 2-19 
 
 11-17 
 11-14 
 11-19 
 11-3 
 11-5 
 11-4 
 11-9 
 11-10 
 11-2 
 11-8 
 11-6 
 11-7 
 
 11-18 
 11-16 
 11-15 
 
 11-12 
 11-13 
 11-11 
 
 2-25 
 2-26 
 
 4-36 
 4-37 
 
 7 
 5 
 
 22 
 23 
 20 
 19 
 25 
 
 14 
 15 
 16 
 
 25 
 22 
 27 
 
 8 
 
 9 
 
 9 
 17 
 18 
 
 7 
 
 14 
 11 
 12 
 
 26 
 25 
 24 
 
 21 
 
 22 
 19 
 
 30 
 30 
 
 45 P.L 
 46 
 
 (551)
 
 42 
 
 Illustration Index. 
 
 No. 
 
 Illustrations. 
 
 SF= 
 
 Telephone — Continued. 
 
 Camp, and circuits 
 
 Camp, dismantled 
 
 Circuits — 
 
 Common battery, simplified 
 
 Local battery, simplified 
 
 Simplified — 
 
 Using four telephone receivers • . 
 
 two telephone receivers . , 
 
 Desk, common battery 
 
 Garford Manufacturing Co., circuits as installed 
 
 North Electric Co., circuits as installed 
 
 Desk, local battery — 
 
 Garford Manufacturing Co 
 
 Sumter Manufacturing Co., circuits 
 
 Hand receiver 
 
 Local battery, circuits 
 
 Magneto-generator 
 
 Theory of 
 
 Voltage curve 
 
 Power switchboards. (See Switchboards, telephone, power.) 
 
 Ringer 
 
 Switchboards. (See Switchboards, telephones.) 
 
 Switchboard, camp 
 
 Systems — 
 
 C. B., motor generator 
 
 C. B., power equipment in switchboard room 
 
 C. B., power switchboard — 
 
 Type No. 1 
 
 Type No. 4 
 
 C. B., rectifier, mercury arc 
 
 C. B., simpHfied diagram of circuits 
 
 C. B., visual line signal operation 
 
 Dynamotor, ringing 
 
 Record - 
 
 Arrangement of power equipment 
 
 Cable splices and lengths 
 
 Connections and cross-connections of cable conductors 
 
 Connections and other data 
 
 Location of manhole 
 
 Routing of lines and location of structures 
 
 Special arrangement 
 
 Special circuits 
 
 Transmitter 
 
 Wall, common battery 
 
 North Electric Co., circuits as installed 
 
 Sumter Manufacturing Co., circuits 
 
 Western Electric Co., circuits 
 
 Wall, local battery 
 
 Garford Manufacturing Co., circuits 
 
 Sumter Manufacturing Co., and circuits 
 
 Terminal box, metal, 1915 model 
 
 Terminal can: 
 
 Fused 
 
 Installation of 
 
 23 
 •24 
 
 4 
 3 
 
 2 
 1 
 
 18 
 22 
 21 
 
 15 
 13 
 ■8 
 11 
 ■7 
 ■5 
 ■6 
 
 -10 
 
 -26 
 
 34 
 33 
 
 36 
 
 •37 
 35 
 •4 
 •5 
 38 
 
 43 
 40 
 41 
 •45 
 •42 
 -39 
 46 
 44 
 9 
 -19 
 20 
 17 
 16 
 
 -14 
 -12 
 -1 
 
 -30 
 -29 
 
 12 
 
 77 
 
 37 
 36 
 
 40 
 41 
 38 
 7 
 7 
 42 
 
 47 
 45 
 46 
 49 
 47 
 44 
 50 
 48 
 11 
 21 
 22 
 19 
 18 
 
 16 
 14 
 
 21 
 
 27 
 26 
 
 P.L 
 P.l. 
 
 P.L. 
 
 P.L. 
 
 P.L. 
 P.L 
 
 P.L. 
 
 P.L 
 
 P.L 
 P.L 
 
 P.L 
 
 (052)
 
 Illustration Index. 
 
 43 
 
 UlustrdtioDs. 
 
 Terminal can — Continued. 
 
 Unfused 
 
 Installed 
 
 Installation of 
 
 Terminal strip, standard 
 
 Tests: 
 
 Blavier, location of grounds 
 
 Emergency insulation 
 
 Improvised bridge — 
 
 Location of crosses 
 
 Location of grounds 
 
 Location of faults — 
 Murray loop — 
 
 Location of crosses 
 
 Location of grounds 
 
 The faultfinder 
 
 Varley loop — 
 
 Location of crosses 
 
 Location of grounds 
 
 With exploring coil, location of grounds 
 
 With improvised apparatus — 
 
 All conductors faulty 
 
 Do 
 
 Conductor parted 
 
 Using a galvanometer 
 
 Using a telephone receiver 
 
 With ohmeter, location of grounds 
 
 Measuring ohmic resistance — 
 
 By means of voltmeter and milliammeter 
 
 Of telegraph line by means of voltmeter and milliammeter 
 
 Of telegraph line by means of voltmeter and milliammeter, practical connections 
 
 Ohmic resistance, fall of potential 
 
 Wheatstone bridge - 
 
 Circuits, diagrammatic 
 
 Conventional diagrams 
 
 Graphical demonstration 
 
 Post-office form 
 
 Principle employed 
 
 With voltmeter — 
 
 Difference of potential — 
 
 At extremities of a coil 
 
 Between two points on a wire 
 
 Location of crosses , 
 
 To measure ohmic resistance 
 
 Using a known resistance 
 
 Voltage of a battery 
 
 Thompson reflecting galvanometer 
 
 Tool bag, service 
 
 Tool chests: 
 
 Cable splicer's 
 
 Construction 
 
 Electrical engineer's 
 
 Mechanic's No. 2 
 
 Pipe filler's 
 
 Post 
 
 Tool kit, inspector's pocket 
 
 No. 
 
 til 
 
 8- 
 
 P.L 
 
 (553)
 
 44 
 
 Illustration Index. 
 
 Illustrations. 
 
 No. 
 
 6 
 
 q 
 
 ;2; 
 
 6 
 
 f5 
 
 ?', 
 
 
 
 c 
 
 ^ 
 
 
 
 .c 
 
 
 u 
 
 '1 
 
 SF! 
 
 Transmitter, telephone 
 
 Tripod lines 
 
 Over ice .... 
 
 Voltaic cell 
 
 Voltamineter, portable . . 
 Voltmeter: 
 
 Post testing 
 
 Test, to locate crosses 
 
 W. 
 
 Western Electric protector . 
 Wheatstone bridge: 
 
 Post-office form .... 
 
 Graphical demonstration 
 
 Wirecarrier 
 
 Wirepike 
 
 3-- 9 
 5-36 
 5--37 
 
 9--21 
 
 10-- 2 
 9-23 
 
 6-9 
 
 9-19 
 9-20 
 8-27 
 8-30 
 
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