AUTOMATIC BLOCK SIGNALS 
 
 AND 
 
 SIGNAL CIRCUITS 
 
 AMERICAN PRACTICE IN THE INSTALLATION AND 
 
 MAINTENANCE OF SIGNALS ELECTRICALLY 
 
 CONTROLLED, AND OPERATED BY 
 
 ELECTRIC OR OTHER POWER 
 
 WITH DESCRIPTIONS OF THE ACCESSORIES NOW 
 REGARDED AS STANDARD 
 
 BY 
 RALPH SCOTT 
 
 FIRST EDITION 
 THIRD 
 
 McGRAW-HILL BOOK COMPANY, INC, 
 239 WEST 39TH STREET. NEW YORK 
 
 LONDON: HILL PUBLISHING CO., LTD. 
 
 648 BOUVERIE ST., E. C. 
 1908 
 
COPYRIGHTED, 1908, 
 
 BY 
 McGRAW PUBLISHING COMPANY 
 
 NEW YORK 
 
an Hij 
 
 BELOVED BBOTHEB 
 HUGH EMMOTT SCOTT 
 
 43863G 
 
PREFACE. 
 
 THE evolution of a mechanical art results in the simplification 
 of its apparatus. The less the number of subsidiary devices 
 employed, and consequently the greater the number of their 
 independent functions, the higher the state of this art. Signal- 
 ing accessories, although of rapid development, have not as yet 
 undergone the usage test that is the prerequisite to standardiza- 
 tion and the elimination of impracticable differentiated struc- 
 tures. In surveying the heterogeneous types of construction 
 employed in the signal equipment of a representative rail- 
 road system, the difficulty of selection and representation, 
 with respect to relative significance, becomes apparent. 
 
 In a book of this character, it is extremely difficult to intelligi- 
 bly exhibit continuous circuits of any great complication, owing 
 to the restricted space available for illustrations, insets not 
 having been resorted to. The history of signaling is not touched 
 upon, as it is irrelevant to the character of the present work. 
 Railroad terms have also been omitted, as they are meaningless 
 to the average reader. 
 
 All-electric interlocking, a natural development of the older 
 mechanical and electro-pneumatic interlocking, is given the 
 attention that its importance merits. Electric railway signals 
 are described as fully as seems advisable, since they are in a 
 transitory state of rapid progress. Electro-gas and three-posi- 
 tion signals, representing the highest development of the art 
 in America, have been treated not only from an electrical stand- 
 point, but also from a structural point of view. 
 
 This book is intended for the signal and railway engineer, the 
 electrician, and the layman; and it is modestly hoped that it 
 will appeal to all in any way concerned with signaling. 
 
 iii 
 
iv PREFACE 
 
 The old argument of normal danger vs. normal clear is not 
 taken up ; nevertheless, data on both these systems of indication 
 is given throughout the book, the reader being left to his own 
 conclusions as to their relative merits. 
 
 The writer wishes to acknowledge several courtesies received 
 from the signal companies whose products have of necessity 
 been described, and also to Messrs. H. S. Balliet, J. C. Jones, 
 B. H. Mann, M. E. Smith, W. W. Slater, and A. J. Wilson. 
 
 Criticisms are respectfully invited. 
 
 R. S. 
 
 WlLKESBARRE, PA. 
 
CONTENTS. 
 
 CHAPTER. PAGE. 
 
 I. PRELIMINARY CONSIDERATIONS 1 
 
 II. SIMPLE CIRCUITS 15 
 
 III. NORMAL DANGER CIRCUITS 30 
 
 IV. NORMAL CLEAR CIRCUITS 50 
 
 V. SEMI-AUTOMATIC CIRCUITS 68 
 
 VI. BATTERIES 84 
 
 VII. THB TRACK CIRCUIT 95 
 
 VIII. CONTROLLED MANUAL SYSTEMS 105 
 
 IX. MOTORS, RELAYS, ETC 119 
 
 X. HALL APPARATUS 131 
 
 XI. UNION APPARATUS 147 
 
 XII. ELECTRO-PNEUMATIC AND ELECTRO-GAS SIGNALS 160 
 
 XIII. ELECTRIC LOCKING 171 
 
 XIV. ALL-ELECTRIC INTERLOCKING 179 
 
 XV. THRBE-POSITION SIGNALS 201 
 
 XVI. ELECTRIC RAILWAY SIGNALS 215 
 
 XVII. MAINTENANCE.. ..226 
 
AUTOMATIC BLOCK SIGNALS. 
 
 CHAPTER I. 
 PRELIMINARY CONSIDERATIONS. 
 
 A block is a length of railroad track of defined limits, the use 
 of which by trains is under the control of one or more block 
 signals. 
 
 A block signal is a fixed arrangement controlling the use of a 
 block. 
 
 An automatic block signal is one automatically operated by 
 electrical or other energy, this agency being controlled by the 
 passage of trams along the track, or by conditions which interfere 
 with such movement. 
 
 A block system is a series of consecutive blocks controlled by 
 block signals. 
 
 A home signal shows the condition of the block directly in 
 front of a moving train; and a distant signal the condition of the 
 second block in front, or the block in the rear of the home block. 
 
 An advance signal shows the condition of a block in conjunc- 
 tion with the home signal of that block. It is placed in advance 
 of the home signal. 
 
 In Fig. 1 two signals, having home and distant semaphores, 
 blades, or boards, are shown, with the track protected by each; 
 train movement being in the direction of the arrows. The en- 
 tire home block, consisting of two sections of the first signal, is 
 represented; and one section of the home block of signal 2, 
 which latter is also the first section of the distant block of 
 signal 1. 
 
 A block is usually made about one mile long, although a large 
 amount of traffic, the presence of an interlocking plant, numer- 
 ous switches, or the necessity of slow-speed movements may 
 
 l 
 
t ' 2's f- * * * i TTmV"*'i>r A mrsv 
 
 AUTOMATIC BLOCK SIGNALS 
 
 require less length. On the other hand, blocks in a sparsely 
 settled district, with thin traffic, can be of greater length. These 
 blocks are protected in automatic visual systems by a disk, 
 semaphore, or revolving member by day, and by colored lights 
 at night; these giving warning of the presence of a train, broken 
 rail, open switch, car outside the clearance point at sidings, an 
 open drawbridge, hand car on the track, or defect in the appa- 
 ratus. 
 
 There are several w r ays of indicating a danger, caution, or 
 clear condition, among which are: (1) color systems; (2) position 
 systems; (3) motion systems. A type of the first is a colored 
 disk moving before a white surface, either the former or the latter 
 being visible; of the second, a blade or semaphore which is held 
 at various angles to the track; when horizontal, " danger " or 
 
 rails 
 
 
 \< cut section b cut section-^ 
 
 Ho. i. Wo.z. 
 
 \t home iloch [of signal i] >| 
 
 FIG. 1 
 
 " stop " being indicated, and when nearly vertical, " proceed " 
 or " clear." Semaphores may be colored also, and thus become 
 of the first type. The third or motion signal utilizes a revolving 
 member, whose motion indicates that an approaching train may 
 continue to move, and when stationary that the engine must 
 come to a stop. At night a light is flashed intermittently by 
 this member. Such systems, and also illuminated semaphores, 
 have been abandoned, and therefore will not be described. 
 
 Usually, signals are numbered in such manner that these 
 numerals will indicate the number of miles and tenths of a mile 
 that the signal is distant from the chosen terminal. Thus on 
 the Lehigh Valley, signal No. 1773 is 177.3 miles from New York 
 City. On this road, odd numbers designate west bound signals 
 and the even numbers the east bound signals. Thus it is evident 
 that 1773 is the west bound signal 177.3 miles from New York 
 
PRELIMINARY CONSIDERATIONS 
 
 3 
 
 City (the nearest odd number to the actual tenth of a mile being 
 chosen). 
 Fig. 2 shows four separate main tracks intersecting at right 
 
 wetbound 
 
 fe 
 
 easoun 
 
 FIG. 2 
 
 angles, with their respective signals. If these are automatic, 
 
 track relays, properly interconnected, can be readily arranged 
 
 to give the protection de- 
 
 sired. If they are semi- 
 
 automatic, electric inter- 
 
 locking will be introduced red- 
 
 to prevent conflicting of 
 
 routes. Thus, when signal 
 
 3 is at clear, to allow a 
 
 south bound train to pass, 
 
 1, 2, and 4 must be locked 
 
 in the normal or stop posi- 
 
 tion when electric locking 
 
 or interlocking is used, and 
 
 prevented from moving to 
 
 clear if the ordinary auto- 
 
 matic system is employed. 
 
 A standard sixty-degree home and distant semaphore arrange- 
 ment is shown in Fig. 3. Until either blade has reached a po- 
 
 Tiome semaphore 
 
 I 
 
 white or Hack 
 yettow 
 
 distant semaphore 
 
 FlG 3 
 
4 AUTOMATIC BLOCK SIGNALS 
 
 sition approximating thirty degrees from the vertical it will 
 indicate the same as though at the full horizontal position. This 
 is effected by using several spectacles, each held in place by in- 
 dependent bezel rings, or by so-called continuous light spectacles. 
 Semaphores vary in length from four to five feet, about four and 
 one-half being regarded as standard. 
 
 FIG. 4 
 
 FIG. 5 
 
 A self-contained standard home and distant, three-spectacle, 
 semaphore signal (electro-gas or motor ), is shown in Fig. 4, the 
 motor, mechanism and battery housings being at the base. 
 This represents the highest development in external design 
 that such signals have reached, unless exception be made of 
 the top post arrangement. 
 
 A three-spectacle, automatic, double-route, home and distant 
 semaphore signal is illustrated in Fig. 5. The post, B, consists 
 
PRELIMINARY CONSIDERATIONS 
 
 of two lengths of channel iron strengthened by a lattice structure, 
 the base being bolted to, or incorporated with, a foundation of 
 concrete, A. The top consists of a platform, G, and railing, E, 
 semaphores, F, being pivoted to short posts and operated by 
 motors and accessories housed in the waterproof base boxes, 
 C-D. This arrangement represents the latest order of con- 
 struction for the protection of two tracks having trains running 
 hi the same direction. 
 
 In Fig. 6 A is a short mast distant semaphore signal with an 
 automatic mechanism housing at the base; B is a high home 
 signal; C a short mast two-arm or double-route, D a high mast 
 two-route, and E a three-arm or triple-route arrangement. The 
 
 T - 
 
 ?- - 
 
 
 
 
 
 s 
 
 
 
 mm 
 
 -M 
 
 S 
 
 ( 
 
 i 
 
 
 
 V 
 
 A 
 
 5 
 
 k i 
 
 Z7 
 
 \ 
 
 
 
 FIG. 6 
 
 standard heights of each are also given, and although this latter 
 may vary somewhat, it represents the usual practice. 
 
 Bridge signals, which are of more substantial design than 
 mast signals, are shown hi Fig. 7. The letters designate types 
 similar to those in the preceding figure. The tracks pass be- 
 neath the bridge at G. Most lines having four main tracks or 
 over use this disposition of semaphores. 
 
 Fig. 8 shows two forms of motor-operated high signals, A 
 being a single arm, and B a two-route arrangement. The cir- 
 cuit breakers, H, are operated by the rods, Or, connected to the 
 semaphore castings. The cast iron box, A, contains the motor 
 and gearing constituting the signal movement (see Fig. 119), 
 and part of the sheave, B, which carries the chains, C, projecting 
 
6 
 
 AUTOMATIC BLOCK SIGNALS 
 
 from below. The blades are connected to the counter-weighted 
 levers, E, resilient members, D, being introduced to prevent in- 
 jury to the parts when they fall, or should the motor wind up 
 too high. Reversal of the motor on B is effected by a ground 
 selector, described in Chapter XIV. 
 
 The electric-motor semaphore signal has several advantages, 
 among which may be mentioned: (1) localization, it being self- 
 contained, and therefore independent of all other signals; (2) 
 comparatively large reserve power; (3) an isolated plant is not 
 required for its operation; (4) economy of installation and opera- 
 tion; (5) working and control functions are unified; (6) external 
 simplicity of design. 
 
 xx>too< 
 
 B 
 
 KX>*<X>f<X>Q<X 
 
 FIG. 7 
 
 The motor and control mechanism is somewhat complicated, 
 and numerous factors of failure have been necessarily intro- 
 duced. A clumsy structure is used to transform the high-speed 
 rotary armature movement into a slow, direct reciprocating 
 motion, while the motor itself is not a perfectly reliable device 
 under the restrictions that must be imposed upon it. Frost may 
 accumulate upon the commutator, the lubricant may gum, or the 
 mica cause an open circuit, thus resulting in inoperation. The 
 clutch or slot magnet armatures may also freeze in the clear 
 position, as they are not acted upon by a powerful force. 
 
 The generic purpose of the electric circuits applied to devices 
 
PRELIMINARY CONSIDERATIONS 1 
 
 whose electrical operation establishes the right of train move- 
 ment, is to prevent conducting continuity when a conflicting or 
 non-clear condition exists. Thus imagine a home-signal recep- 
 tive device whose energization cannot occur until twenty-four 
 independent contacts have been closed, each having a function 
 
 D 
 
 
 
 ff 
 
 n 
 
 FIG. 8 
 
 which determines the right to proceed; then the opening of any 
 one or more of these prevents the flow of current which is 
 obviously the concomitant of a clear condition. It is the 
 comprehension of this principle which will render evident the 
 application of signal circuits and their close approach to being 
 an ideal selective intermediary. 
 
8 AUTOMATIC BLOCK SIGNALS 
 
 Commercial signal circuits may be divided into two parts, 
 which are more or less generic according to the system 
 employed. These are respectively control circuits and working 
 circuits. 
 
 Usually a control circuit has a relatively low impressed vol- 
 tage, and the circuit wires are not of great length. The most 
 common type of control circuit is that constituting what is ordi- 
 narily termed the "track circuit/' which includes the rails of the 
 section to which it is applied, with the requisite track battery, 
 relay, and interconnecting wires. The primary purpose of the 
 control circuit is to close and open another circuit, the latter 
 delivering considerable energy and actuating the devices 
 included in the direct operation of the signal banner or 
 semaphore. 
 
 This latter constitutes the working circuit. The main bat- 
 tery, which is in this circuit, cannot be short-circuited, owing to 
 
 FIG. 9 
 
 the loss of energy which would result, the deleterious effect upon 
 the cells, and the excessive sparking at the shunt contact, 
 which latter would necessitate the use of unusually heavy or 
 special circuit breakers. With a resistance in series, such as 
 the line wire, motor, slot magnets, or other accessories, these 
 precautions do not apply. 
 
 Considering the arrangement in Fig. 9, with a normally clear 
 signal, S, whose current is obtained from a battery in shunt with 
 the rails of the insulated track section, A-B, it is evident that 
 as soon as a car, train, or locomotive passes along this section in 
 the direction of the arrow, the resulting short-circuiting of the 
 battery will deprive the signal of current, and thus throw the 
 semaphore to the danger position. A train which is on any 
 other section of the rails will not affect this signal, which there- 
 fore indicates only the condition of the section it immediately 
 precedes. Such a circuit, while readily comprehended, is not 
 commercially practicable for the following reasons: 
 
PRELIMINARY CONSIDERATIONS 9 
 
 (1) Too great a length of line wire is required. 
 
 (2) Unnecessary waste of energy, due to the short-circuiting 
 of the battery. 
 
 (3) Adequate protection is not afforded (for reasons that will 
 be clearer later). 
 
 (4) Too great a current loss will occur, due to the high differ- 
 ence of potential between the rails. 
 
 The principle of introducing series switch-contacts to throw a 
 signal at danger when track switches in its block are opened into 
 the home circuit of a signal is set forth in Fig. 10. In the block 
 of S are three switches, C, E, and G, having three switch in- 
 struments, A, D, and K. Battery B energizes the operating 
 mechanism of the home semaphore, H, through the successive 
 relay points and the single pole contacts at A, D, and F. There- 
 fore, should either of these switches be thrown open, the signal 
 
 FIG. 10 
 
 circuit will be broken and the signal held at danger, regardless 
 of the condition of the relay contacts. 
 
 In general, it is better to place the dependence of a safety 
 condition or a danger indication upon the opening of a circuit 
 rather than its closing. In the low-voltage circuits used in 
 signaling, there is greater certainty in opening than in closing a 
 contact. This is because a poor connection (or particles of dirt 
 preventing the intimate metallic contact which is the prerequisite 
 of a closed circuit) may introduce a sufficient resistance or air- 
 gap to oppose the desired flow of current. As an example, the 
 closed-circuit and open-circuit types of switch instruments may 
 be cited. In the former, with an open switch, the track must 
 be short-circuited; in the latter, the signal circuit must be opened 
 to hold the signal at danger. The latter is obviously the most 
 reliable, as a poor contact will merely mean a false danger 
 
10 AUTOMATIC BLOCK SIGNALS 
 
 condition, while in the former, it will set up a false clear 
 signal. 
 
 Nearly all existing types of automatic signals may be used in 
 a semi-automatic sense; for example, placed at an outlying 
 switch or interlocking scheme, and controlled by a line or track 
 circuit from the nearest tower. Such a provision eliminates the 
 use of cumbersome and costly mechanical interconnection, and 
 involves no appreciable labor on the part of the operator in 
 clearing or releasing. When the track circuit is used, the oper- 
 ation of this signal is taken from the immediate control of the 
 tower operator, although the conditions required to be set up 
 by train movement may class the signal as not purely auto- 
 matic. The extension of these principles will be considered in 
 Chapter V. 
 
 The conditions that may set up a false or dangerous condi- 
 tion in a signal system are manifold ; but their actual occurrences 
 few. The failures at danger can only wrongly delay a train; 
 but failures at clear, by giving the engineer a proceed indication 
 when such may not be safe, are the only ones that can really be 
 termed dangerous. Such failures have in practice occurred on 
 an average of one in a million movements. On a normal clear 
 system, an average of one in about six hundred thousand has 
 often been reported. Many such failures occur from inability 
 of the moving system to move from its normal position. It is 
 not, primarily, the external parts which are sensitive to such 
 checks to movement, as they are thrown by a powerful force, 
 and with sufficient inertia to remove a retardation ; but the light 
 control parts, whose motion is due to the expenditure of energy 
 measured in thousandths of a watt. 
 
 Among the causes of false clear conditions are, fusing of con- 
 trol contacts, improperly counterweighted banner or semaphore, 
 breaking of the color spectacles, rusting of sliding parts, foreign 
 currents, residual magnetism in relays, imperfect contacts, dust 
 or insects in relay boxes, crossing or grounding of wires, inter- 
 connection of wires with common, poor armature pivots, failure 
 of clutches or locks to return, breaking of mechanical connec- 
 tions, and poorly insulated circuit wires. 
 
 The use of white as a clear indication is meeting with dis- 
 favor. This is due to the liability of a spectacle's breaking, or 
 the chipping off of its color film. The adoption of green or red 
 
PRELIMINARY CONSIDERATIONS 11 
 
 for clear has many advantages, among which are the normal 
 danger indication of a white light, except when a color spectacle 
 is actually and properly before it, and the restricted conditions 
 under which safety indications are given. 
 
 Failures at danger may be caused by a broken rail, bond wires 
 rusted off or broken, rusty channel pin, high-current leakage 
 between the tracks, broken wires in the relay, polarity reverser, 
 track battery or signal circuit, exhausted track or main batter- 
 ies, poor connections, unsoldered joints, broken battery jar, 
 useless or poor connection in switch boxes or controllers, blowing 
 of the protective fuses, failure of an arrester, broken line wires, 
 short-circuiting of an individual or series of batteries, open cir- 
 cuit at motor commutator, failure of electric slots or locks, 
 poor insulation, short-circuits in relays, and the depredations of 
 mischievous persons. 
 
 As far as visual indication is concerned, the normal danger 
 position is undoubtedly the best, and has been so recognized 
 since the inception of mechanically operated semaphores; while 
 argumentative opinion, from a purely electrical standpoint, 
 also favors such a disposition. Formerly, standard normal 
 clear circuits were more economical in initial installation, but 
 this consideration no longer obtains. 
 
 Various signal engineers and others have from time to time 
 regarded a certain modification or departure as ideal. Such 
 arrangements, when actually applied, have frequently an ephe- 
 meral existence. In no specific instance has such unproductive 
 effort been expended as in rail bonding. Railroad accessories 
 undergo hard usage, and are subjected to extremes of weather, 
 so that a scheme which seems temporarily of a revolutionary 
 character is found hopeless after a few years of service. The 
 greater part of the accessories introduced since automatic sig- 
 naling began have been abandoned for this reason, so that 
 standardization appears distant when viewed from the present. 
 
 Numerous attempts have been made to introduce protective 
 arrangements supplementary to a visual system, in which the 
 control of a train is taken temporarily from the engineman 
 in case a danger signal is ignored or unapprehended. Fig. 11 
 shows an impracticable, though a generic form of such an ac- 
 cessory. When the home semaphore is in the danger position, 
 it raises a finger or projection which engages with a pivoted 
 
12 
 
 AUTOMATIC BLOCK SIGNALS 
 
 lever secured to one of the trucks of a train. This lever, B, is 
 fastened to a valve, A, which is connected to the train pipe, T, 
 of the air brake equipment by a flexible tube, C, the travel of 
 this lever being limited by the quadrant D. Obvious reasons 
 can be advanced against the application of such a device. We 
 will take up in Chapter XVI a development of this principle, 
 which has the merit of being in use. 
 
 The normal danger system admits of the employment of nor- 
 mally open-track circuits. This condition allows the use of 
 open-circuit batteries (gravity cells cannot be employed) with 
 consequent economy of operation. Instead of the customary 
 
 FIG. 11 
 
 two weeks' intervals between patching and renewing, it is pos- 
 sible to run six months. The circuits are closed in the preced- 
 ing two blocks by the approaching train, and should anything 
 be wrong in the block, the track relays will receive no energiza- 
 tion. The continual heavy demand upon track batteries by 
 the low-resistance track relays under a clear track condition has 
 been heretofore one of the greatest disadvantages of signal 
 installation. 
 
 In Fig. 12 a diagrammatic representation of relays and con- 
 tacts, such as is used throughout this book, is given. A has 
 one front (upper) and one back (lower) contact, each being 
 a single-pole break, and so disposed that both cannot be in 
 
PRELIMINARY CONSIDERATIONS 13 
 
 simultaneous contact with the armature. B is a single front 
 contact, and is more frequently applied than any other combina- 
 tion. C has two front contacts, with independent armatures; 
 D two front and one back; E three front with common arma- 
 ture; F two front and two back; G three front with independent 
 armatures; and H four front and four back, each having a 
 double simultaneous break. In reality, these connections are 
 usually effected by a single armature on each relay, but a more 
 definite conception is afforded by representing as shown. 
 
 The application of automatic signals, by giving to trainmen 
 the right to shift their trains at all reasonable times, renders im- 
 perative a positive knowledge of the condition of the track to 
 which they are to proceed. Should a train be approaching this 
 
 block or is already within it, there must be some means of warn- 
 ing the trainmen not to open the switch. Should such a switch 
 be opened, the main line signal must be held at danger, and in- 
 formation be conveyed to the trainmen that it has, and that 
 the opening of the switch was the cause of such movement. 
 This is now accomplished by means of a polarized indicator, as 
 the neutral type cannot be thus applied; for, if a train enters 
 the main block in question at the moment the switch has been 
 thrown, the trainman will necessarily assume that he has been 
 the cause of such indicator's movement, and unconsciously pro- 
 ceed to the main line without expectation of danger. Thereby 
 delay would result to the train passing the main signal, if the 
 latter's indication were understood by the engineman, but 
 should the latter fail to note the condition of the block, a colli- 
 sion might result. 
 
14 AUTOMATIC BLOCK SIGNALS 
 
 Primary cells are employed almost exclusively for the opera- 
 tion of automatic signals, because of their peculiar adaptability 
 to the requirements of these devices. Although not nearly so 
 economical as other methods of setting up currents of electric- 
 ity, yet, when a small amount of energy is to be delivered con- 
 tinuously, or for long periods of time with extreme reliability, 
 the question becomes not economy, but constancy of operation. 
 
 Thermoelectric devices, in which currents have been set up 
 directly from heat, have been tried, but as yet have been found 
 wanting, owing to their multiplicity of parts and the necessity 
 of maintaining a flame continuously. Improvements along this 
 line are anticipated, but may be hopelessly remote. 
 
CHAPTER II. 
 SIMPLE CIRCUITS. 
 
 SIGNAL circuits admit of innumerable variations; and nearly 
 every installation requires a special scheme of interconnection. 
 There are, however, certain generic features adhered to which 
 obtain in most cases. It is their differentiation which produces 
 the seeming complexity when viewed as a whole. A number of 
 simple circuits and their modifications will now be taken up. 
 
 The circuit diagram for an old style of disk signal is shown in 
 Fig. 13. The main battery 11 is connected to the track, 15, 
 
 train 
 
 FIG. 13 
 
 and through the latter to two relays at signals, 14 and 12, in 
 series with the line wires, 1 and 2. The signal connections are 
 similar, and consist of a clearing electromagnet, 6, and a stop 
 magnet, 5, whch are connected respectively to the connects, 9 
 and 10, of the armature of 3, the latter being pivoted at 8, and 
 weighted at 13. With a train in the block, 11 is short-circuited, 
 hence the relays are deenergized, their armatures touching the 
 upper contacts, and closing the local circuit of 4 through 6, as 
 shown. Thus, when the block is occupied, 6 is energized; 
 when not, 5 is energized. A disadvantage of this method of 
 connection is the great waste of energy when 11 is short-cir- 
 
 15 
 
16 
 
 AUTOMATIC BLOCK SIGNALS 
 
 cuited, and the dangerous effects of a connection between line 
 wires 1 and 2. 
 
 It frequently becomes advisable to control a distant signal 
 from a manually or automatically operated home signal through 
 the interposition of a circuit controller. Such an arrangement 
 of circuits is given in Fig. 14, and provides for a power-operated 
 
 5U 
 
 FIG. 14 
 
 distant signal. The latter, shown at D, is governed by the cir- 
 cuit controller, G. When the latter is closed (which will occur 
 when the home signal, B, is thrown to the clear position by the 
 operator at the signal tower, T) the line battery, A, sends current 
 through the relay, (7, at the other end of the line, which raises the 
 armature, F, of the latter, closing the motor circuit of the local 
 battery, E, and thereby throws D to the clear position. 
 
 o 
 
 D 
 
 FIG. 15 
 
 If the above arrangement does not include sufficient precau- 
 tionary measures, other functions are included which will pre- 
 vent, in various ways, the conflicting of routes, false indications, 
 and delay in train movement. It is the proper recognition of 
 these factors, and their successful elimination, which produces 
 the complexity often met with in signal circuits. In Fig. 15, 
 
SIMPLE CIRCUITS 
 
 17 
 
 a switch, K, is introduced in the simple-control circuit given 
 above, which requires operation by the tower attendant before 
 the distant signal will assume the clear position. This condi- 
 tion is effected by including it in series with the line battery and 
 relay governing the distant signal's motor circuit. 
 In Fig. 16 is shown a circuit arrangement which employs a 
 
 " 
 
 FIG. 16 
 
 vibrating bell, (7, to communicate the desired announcement of 
 the motion of a distant signal blade, D, to the tower operator. 
 Motion of the semaphore produces a movement of the contact 
 arm of the special controller, A, and consequently closes the 
 circuit of the battery, B, in which C is included. This controller 
 
 
 PI 
 
 if -1 
 
 uZ m 
 
 ^ 
 1 i i 
 
 1 
 
 f\ 
 
 "U 
 
 r 
 
 FIG. 17 
 
 is so arranged that when the blade is in either the extreme cau- 
 tion or clear position the circuit is opened. While the blade is 
 moving, on the other hand, the circuit is closed. C may be a 
 combination bell and indicator, or it may include a setting device. 
 A visual indication of the clear or caution position of a distant 
 signal requires the use of an indicator, as shown in Fig. 17, at E. 
 
18 
 
 AUTOMATIC BLOCK SIGNALS 
 
 When C is closed by the motion of the semaphore of D, the 
 battery circuit is completed and the armature of E will be raised, 
 in the type of indicator illustrated. Another type is used, how- 
 ever, which will indicate clear when its armature falls, requiring 
 the use of a controller whose make and break is in the opposite 
 sense to that shown. 
 
 FIG. 18 
 
 In Fig. 18 we have a semi-automatic arrangement of circuits 
 in which the circuit controller, D, is operated by the representa- 
 tive lever, A, of an interlocking machine. This lever controls 
 by its mechanical movement a certain function, the electrical 
 adjuncts being for another and distinct purpose, but of a con- 
 comitant nature, in the scheme of protection. When A is 
 thrown in the direction of the arrow, the circuit of the line bat- 
 tery, B, is closed, thus energizing the distant relay, E, which, 
 through its armature, H, sends a clearing current from the local 
 battery, G, through the distant signal, F. 
 
 kL* 
 
 
 FIG. 19 
 
 In Fig. 19 the same principle is contemplated, but in addition 
 a circuit controller, M, is employed, which thus prevents the dis- 
 tant signal from being cleared until the function the controller 
 protects has been properly manipulated. This function, as will 
 
SIMPLE CIRCUITS 
 
 19 
 
 be shown throughout this book, may have any desired applica- 
 tion or complexity. 
 
 In Fig. 20 we have another semi-automatic scheme of connec- 
 tion for a distant signal; the bonded track circuit being used 
 instead of line wires. The track battery, T, maintains a differ- 
 ence of potential across the section, S, and normally, by energiz- 
 
 n: 
 
 FIG. 20 
 
 ing the track relay, R, causes a current to pass from the local 
 main battery, B, to the distant signal, Z), through the armature, 
 C. When H is cleared, the controller, A, is closed, and the 
 reverse condition of affairs to that given in the figure obtains. 
 Such an arrangement is more desirable, and less complicated 
 than a line-wire system. 
 
 FIG. 21 
 
 The above distant signal cannot be controlled otherwise than 
 through the movement of the home board. It sometimes is advis- 
 able to give the signalman authority to throw the distant board 
 to caution without altering the clear position of the home signal. 
 This is effected as shown in Fig. 21. When H is cleared, B will 
 be closed as before. In addition, the hand switch, A, must be 
 closed, or the track relay, E, cannot be energized due to the 
 
20 
 
 AUTOMATIC BLOCK SIGNALS 
 
 position of the armature of C, and its connection with track 
 battery, D. Thus, when both A and B are closed, the distant 
 signal can be cleared. The armature of C, by short-circuiting 
 the track, thereby performs the same function that a train in the 
 section would. 
 
 In Fig. 22, H and F are normally clear home signals protect- 
 ing the respective insulated track sections, 5, 4, 3, 2, and 1. The 
 reason for such a division of a block is to increase the reliability 
 of the track circuits by decreasing the effect of the track-circuit 
 current leakage from rail to rail. The track batteries, G, are 
 connected to the west or extreme end of each section, so that a 
 train moving in the direction of the arrows will shunt the relays, 
 the batteries discharging their current through the entire length 
 of the rails. This protects against broken rails or open bonds, 
 
 by depriving the relays, such as J, E, C, A, and Z), of current 
 when such an open circuit occurs. 
 
 Under normal conditions, when neither of the sections is occu- 
 pied by a train, the main batteries, as R, are in closed circuit 
 with the signal mechanism, thus holding the discs in the clear 
 position. When a train is approaching a signal, it is not affected, 
 as the control functions remain the same. After entering the 
 block, however, the relay, J, at the first section is deenergized, 
 thus allowing its armature to fall, and open-circuiting the 
 signal or working circuit and throwing the disc (or sema- 
 phore) to stop. This will occur on any section within the block, 
 as the armatures and contacts are in series. 
 
 The functions introduced in a normal danger system, which 
 clears the semaphore when the train enters the preceding block 
 and causes it to remain clear until the train has left the block, 
 irrespective of the number of sections it contains, are set forth 
 in the diagram, Fig. 23. When the lower or back-contact 
 armatures or points of relays, M , W, or T, drop, the home sema- 
 
SIMPLE CIRCUITS 
 
 21 
 
 phore, V, will move to clear, providing the front contacts of K 
 and L are closed. This occurs by reason of the back contacts 
 of the relays, M, W, and T, at sections 3, 4, and 5 being connected 
 in multiple, so that if one back contact closes, the same electrical 
 condition is set up that would be the case if all or any other one 
 of these contacts were closed. The front contacts of these relays 
 
 ft^lL A 
 
 -2J 
 
 t 
 
 M 
 
 a 
 
 H'I'K 
 
 r? 
 
 FIG. 23 
 
 are in series with the main battery, 7, which operates signal 
 P, so that if either be open, the signal will remain at danger; a 
 condition occurring when a train occupies either section. These 
 relays thus become double functioned; and it frequently is pos- 
 sible to have all the contacts at a section box controlled by one 
 relay. A modification or extension of this arrangement is used 
 in all normal danger non-polarized line-wire systems. 
 
 In Fig. 24, 1 and 2 are two independent normal danger home 
 signals, giving indications for trains bound west. The cut sec- 
 
 FIG. 24 
 
 tions, 7, 8, 9, 10, and 12, are connected to the respective relays, 
 S, V, R, P, and Q, whose armatures, with one exception, close 
 the circuits to which they are connected when the relays are 
 energized. The lower, or back contact, armature prong on R is 
 normally open, and consequently keeps the main battery in open 
 circuit. Its purpose is to hold the semaphore at stop when R 
 is energized, and to clear the blade when R is deenergized. This 
 
22 
 
 AUTOMATIC BLOCK SIGNALS 
 
 latter will occur only when a train occupies section 9, which may 
 thus be termed a setting action. This clearing of the sema- 
 phore takes place under restricted conditions. If a train or 
 broken rail occur in sections 7 or 8, 1 cannot be cleared by this 
 armature falling, since the front contacts of either S or V will 
 be open. Thus, if a train occupy section 8, the circuit will be 
 opened at the armature of relay, V. The line wires, Y, are placed 
 upon poles, and pass from one relay to the others. This arrange- 
 ment is somewhat similar to the preceding, with the exception 
 that the home signal is cleared only at the setting section. 
 
 Another simple, normal, clear home and distant (on the same 
 mast) scheme of connection is shown in Fig. 25. The signals, 
 T and P, each protect the track for two blocks, and are operated 
 by the relays, Q, W, B, 0, and M, each having two armature 
 
 contacts, the lower of which are connected to the distant 
 blades, and the upper to the home blades. The home sema- 
 phore at P is controlled through the armatures of relays, B, W, 
 and Q, which are connected to sections 3, 4, and 5. The dis- 
 tant is in series with the normally closed armatures of and M 
 at sections 1 and 2. These relays and semaphores are inter- 
 connected by line wires, as 7 and 8. It will be noted that 
 the relays and track batteries are connected to opposite ends 
 of each section, thus requiring the relay energizing current to 
 pass along the rails, neutralizing the effect of fall in potential, 
 and assuring the positive shunting of the relay by the train; at 
 the same time guarding against broken rails. 
 
 The two general methods of throwing a signal member to 
 danger when there is an open switch in the block are shown in 
 Fig. 26. At sections 8 and 10 we have two switches, at which are 
 placed the switch instruments, B and F. When the switch at 
 
SIMPLE CIRCUITS 
 
 23 
 
 8 is opened, B short-circuits the track, and consequently the 
 relay and track battery, thus setting up a condition analogous 
 to that of a train in the section, the signal, K, being thrown to 
 
 to signal 
 
 main track 
 
 FIG. 26 
 
 stop in this case by the deenergization of D. This is effected 
 by contacts within the switch instrument box which are con- 
 nected to the rails of the track, so that when a revolving or 
 rocking member is operated by a switch point, the rails become 
 connected electrically. 
 
24 
 
 AUTOMATIC BLOCK SIGNALS 
 
 At section 10, another arrangement is employed. F is a 
 normally closed contact-spring, which is in series with the main 
 battery, H, contacts of E, G, and /, and the home line of N. 
 When the switch is thrown, F is opened, thus causing N to 
 assume the danger position. Such a device is used only in line- 
 wire systems, and particularly on normal danger circuits. 
 
 At P, the switch instruments, T, are applied to a cross- 
 over; or from one main track to the other (trains moving in 
 opposite directions), V and X are indicators, whose functions 
 will be described later. Battery C supplies current to relay J, 
 which current is cut off and the track rails short-circuited, when 
 the switch is thrown. At F, the same arrangement is applied 
 to a siding, S and U being switch instruments, and W an 
 indicator. 
 
 FIG. 27 
 
 A simple arrangement of overlap circuits in which distant 
 signals are not used is shown in Fig. 27. Overlap was used in 
 most early systems, to give an indication of a block's condition 
 prior to the arrival of a train at the entrance of this block, thus 
 eliminating the speed reduction that would be otherwise neces- 
 sary in case a fog or other obscure condition prevented a clear 
 view of the signal. The block, L-N, consists of two sections, 
 L-M and M-N; in the latter an open switch, K, being present. 
 Signal 71 protects this block, and is placed between signals 61 
 and 81. 
 
 The signal electromagnet, S, is in series with the armatures, 
 H and 7, of relays, F and G; main battery, E; and switch instru- 
 ment, J, at switch, K. Since the latter is open, E cannot dis- 
 charge current into S, because of the open circuit at the switch 
 
SIMPLE CIRCUITS 25 
 
 instrument. Due to the rails at K short-circuiting the section, 
 M-N, G is also short-circuited, and its armature is in the lower 
 position. F, however, is still energized by the track battery, D, 
 but does not affect S. As H, E, and A are in series, the arma- 
 ture, B, of the latter closes its contact and allows the track bat- 
 tery, C t to maintain a difference of potential across the rails of 
 the section before L-M, or the second section of signal 61. 
 
 If a train were to occupy L-M, A would be deenergized, thus 
 holding 61 at danger. Also, if M-N is occupied, 71 will be at 
 danger, while 61 is at clear. Signal 81 is unaffected by train or 
 switch movement in the block protected by 71, but operations 
 in the block of 81 would affect 71 in the manner above 
 shown. 
 
 Overlaps may have application equally well to normal clear 
 or normal danger systems. Figs. 28 and 29 show the circuits 
 used in a line-wire system for overlap on a single track for the 
 former, with home signals only. Should a train occupy the sec- 
 tion between 161 and 162, track relay, C, will be deenergized, 
 and its armature contacts consequently opened. This open- 
 circuits the clearing magnet or slot, H, and moves 162 to danger. 
 The middle armature of C also open-circuits the operating mag- 
 net of 161, moving the latter to danger; 160 remains cleared, 
 however, as A receives current from the battery at the next 
 signal in its rear (in the same direction) through the line. 
 
 E and F are circuit breakers operated by the moving to stop 
 of 163, and / is an indicator placed at the switch, K, in series 
 with F. Hence, when F is closed, / should be at clear, since 
 it receives battery current from B (through J" and K). L is 
 another switch indicator in series with circuit breaker, M, of 161. 
 The remainder of the circuit is a repetition of the above. 
 
 At 1, in Fig. 30, L is a switch indicator placed at the main-line 
 switch, D, which will indicate clear to a brakeman only when the 
 home signals in the two preceding blocks, A and B, are at clear. 
 This is effected through the use of circuit controllers or relay- 
 armature front contacts at these signals, as shown. At 2, G is 
 a polarized instrument which consequently has two (or three) 
 indication positions. The controller at signal E determines the 
 setting up of current in G, and the pole changers at F, the 
 polarity of this current. In this fashion, the banner of G may 
 either be in a central or side position, the language to the 
 
26 
 
 AUTOMATIC BLOCK SIGNALS 
 
 brakeman being effected by its moving before one or more 
 apertures in the mechanism housing. 
 
 =B 
 
 i 
 
 *5 
 
 1 
 
 Crossing signals are employed to warn pedestrians or teams 
 at a highway or grade crossing of the approach of a train or loco- 
 motive. Fig. 31 shows a common circuit arrangement for such 
 
SIMPLE CIRCUITS 
 
 27 
 
 a scheme, two insulated and bonded sections of track adjacent 
 
 MJ 
 
 to a highway forming part of the control elements, although line 
 wires may also be used. These sections, 1 and 2, are electrically 
 
28 
 
 AUTOMATIC BLOCK SIGNALS 
 
 isolated by the insulating joints, G, and energized by the track 
 batteries, A. At the highway a signal, 3 (which contains the 
 accessories diagrammatically shown), gives warning of train 
 
 FIG. 30 
 
 movement by the ringing of a bell; which latter is sometimes 
 supplemental to a small low- voltage incandescent lamp for night 
 
 FIG. 31 
 
 indications. L is a station or block tower, provided with an 
 automatic drop, H, containing an audible or visual indicating 
 device, J, introduced in a local circuit closed by the release of 
 
SIMPLE CIRCUITS 29 
 
 the contact armature. E is a relay having two interlocking 
 armatures and separate magnets, so that if a train begins moving 
 in either direction, the bell, F, will ring, but as soon as it passes 
 the highway, F will cease to ring, due to the interference of the 
 armature prongs which hold open the bell circuit. Thus, sup- 
 pose a train moves from 1 to 2. A will be short-circuited and E 
 deenergized, allowing a current to flow from B through F. At 
 the first stroke of the bell clapper, a shunted current passes over 
 the lines, K, and thereby operates /. As soon as the train 
 passes the highway, the armatures of E and W interlock, one 
 holding the other away from the common contact, thus open- 
 circuiting F. When the train passes out of section 2, E 1 is ener- 
 gized, thus retaining both armatures from interference. 
 
CHAPTER III. 
 NORMAL DANGER CIRCUITS. 
 
 IN the normal danger system, the indication members are 
 always in the danger position, except when a train is approach- 
 ing them. In the last chapter, a number of such simple 
 circuits were taken up, hence preliminary details will be 
 unnecessary. 
 
 Figs. 32 to 35 show consecutive normal danger line-wire sig- 
 nal circuits as applied to a single-track line with a passing side 
 
 FIG. 32 
 
 track, and trains running in both directions. The signals are 
 numbered according to miles and tenths of a mile, indicators 
 being included at a siding. In Fig. 32, 6 is the switch leading 
 into the main siding, while 4 is a track relay having four sets of 
 armature contacts 
 
 Should a train be approaching 127.2 (on the main track), 
 the four-ohm track-relay, 4, will be short-circuited, thus causing 
 all of its contacts to open except the second, which is a back 
 
 30 
 
NORMAL DANGER CIRCUITS 
 
 31 
 
 contact. The closing of this latter causes a current to flow 
 through the clearing arrangement, 7, main 127.2 line, lower con- 
 tact at 6, and main battery at the preceding section, thus clear- 
 
32 
 
 AUTOMATIC BLOCK SIGNALS 
 
 ing 127.2. The controllers, 8 and 9 ; which are operated by the 
 semaphores at this signal, are in series, so that when either 
 operates, line 10 is open-circuited. The track battery, 5, is con- 
 nected to both the main and siding sections by the cross bond 
 and insulating joint at 6; so that should a train be upon either 
 track, it will be short-circuited. 
 
 In Fig. 33, 12 is a track-relay receiving current from 11, the 
 latter also energizing the section constituting the end of the 
 side track. The switch, 13, leading into this siding, operates 
 
 /2S.2 
 
 1 26.1' 
 
 FIG. 34 
 
 four independent contacts, which are in series with the various 
 line wires. The main battery and clearing magnets at signals 
 126.2 and 126.3 are connected to the common line wire, while 
 14 and 15 perform functions similar to 8 and 9. 
 
 Supposing that a train approaches signal 125.2, in Fig. 34, 
 17 will be short-circuited, thus closing the middle armature con- 
 tact and clearing the signal through 18, by way of the common 
 wire, line 125.2, first contact of 19, first contact of 20, lower 
 contact at 22, 14, 15, third contact of 12, first contact of 23, 
 battery 28, and returning to common. 
 
 In Fig. 35, 24 is an indicator wound to 800 ohms resistance 
 which is connected to the indicator line-wire through the fourth 
 armature of track relay 25 (of 4 ohms resistance), to the first 
 armature of 17, to 16, middle armature of 19, first armature of 
 
NORMAL DANGER CIRCUITS 
 
 33 
 
 26, battery, and common line. The remainder of the connec- 
 tions are similar to those just considered. 
 
 JJ 
 
 JJ 
 
 TO 
 
 <0-=-<0 
 
 /2V. 
 
 MO* 
 
 FIG. 35 
 
 In Figs. 36 and 37 the connections of a home and distant 
 system for single-track with train movements in one direction 
 
 A 
 
 m. 
 
 G\ W 
 
 HOT 
 
 PI 
 
 ILL 
 
 _!JI3_ 
 
 03 
 
 Indicator wire- 
 
 FIG. 36 
 
 are shown. At signal 1, D controls the distant semaphore, and H 
 the home semaphore, both being mounted on a common mast. 
 A and B are track relays, A having two armature contacts, and 
 
34 
 
 AUTOMATIC BLOCK SIGNALS 
 
 B one. F is in series with the common line and armature G. 
 4 and J have a common connection to line 12, and are respectively 
 connected to H and line H l , while L is operated by H and 
 controls the distant blade. With a train approaching 3, B and 
 K will be deenergized; hence J will be opened, and M closed, 
 being disconnected from H 1 at both J and P. 
 
 When the block of 3 is clear, Q and R will be closed. T is 
 in series with H and M at 3, and D at 1, through line D l . R, 
 S, and V are in series with the indicators, / and W (Fig. 37), 
 through the indicator line-wire. H 3 transmits current from Z 
 by way of the switch instruments, Y and X, and contact 8. 
 
 Indicator -wire* 
 
 FIG. 37 
 
 At signals 5 and 7, a similar arrangement of circuits is evident, 
 one side of the main batteries being connected as usual to the 
 common line. At 7, a single normally open circuit-breaker, (7, 
 is provided, for the control of the distant head only. 
 
 Figs. 38 to 41 contemplate consecutive normal danger over- 
 lap signals such as are in use on the C. N. 0. & T. single- 
 track, with trains running in both directions; protection being 
 afforded against both rear-end and head-on collisions. In Fig. 
 38, four signals, 1, 4, 15, and 17, with their connections, are 
 shown. Four track sections, with batteries 3, 2, 18, and 16, 
 and two relays, 7 and 6, constitute the control functions in this 
 figure. 7 has three armatures, 13, 14, and 12, the first being 
 connected to the main battery 5, the second to signal 4 through 
 
NORMAL DANGER CIRCUITS 
 
 35 
 
 a line wire, and the last to a battery line. Armatures 8, 9, and 
 10, of track relay 6, are connected respectively in series with 
 main battery 11 and the common line, armature 12 and signal 
 15, also 14 and a battery line. Thus one side of each main 
 
 FIG. 38 
 
 battery and signal is connected to the common line, this apply- 
 ing to all four illustrations. 
 
 Continuing the track sections and line wires at a cut section 
 in Fig. 39, two track relays, 36 and 37, have armatures (contacts) 
 38, 39, 40, and 41, 42, 43, respectively; while 44 and 45 are 
 connected as in the preceding, 39, 43, and 40, 42, being inter- 
 connected in series. 
 
 FIG. 39 
 
 In Fig. 40 a siding, 20, with switches, 21 and 22, is added, 
 signals 19 and 23 being placed at this siding. Track relays 24 
 and 25, each having two armatures, 27, 26, and 28, 29, are 
 added at the setting sections, their connections being similar to 
 those already given. Switch instruments are not shown at 21 
 and 22, as they short-circuit the track in a manner similar to a 
 train at these points, when open. 
 
36 
 
 AUTOMATIC BLOCK SIGNALS 
 
 The track battery, 30, in Fig. 41, is in series with the armature, 
 32, thus introducing track circuit control. Signal 34 receives 
 current from battery 44 through contacts, 41 and 29, while 35 
 is operated by current coming similarly over its line wire. The 
 
 
 
 
 r ?] 
 
 27 26 
 
 29 
 
 
 FIG. 40 
 
 main battery, 33, is in series with armature contacts 31 and an 
 armature in the preceding block. 
 
 Suppose a train to be moving toward the west at 46 and that 
 switch 21 is open. 47 will be short-circuited, and consequently 
 
 f 51 
 
 FIG. 41 
 
 37 deenergized, which causes 42 to fall, and holds 19 at danger, 
 notwithstanding the fact that two sections intervene. As 25 
 is also demagnetized, 23 is held at danger by reason of the 
 position of 28, while 29 open-circuits 44, and thus deprives 34 
 of current. 
 
NORMAL DANGER CIRCUITS 
 
 37 
 
 Another line-wire arrangement for home and distant on the 
 same masts for one of the tracks of a double-track line is shown 
 hi Figs. 42 and 43. At the former, 1 is the distant line, 2 the 
 home, 3 the common, and 4 the indication. Track relays 6 and 
 12 have a resistance of 4 ohms, 7 of 12 ohms, and 8 and 13 of 
 16 ohms; each of these having two sets of contacts. At section 
 9, for example, there are a set of binding posts, 25, which are 
 
 FIG. 42 
 
 mounted on the lightning arresters and connect to fuses. 16 
 and 21 are back contacts, while 15, 17, 18, 19, 20, 22, 23, and 
 24, are front contacts. 9 and 14 are track batteries, the latter 
 in series with 15, and therefore in open circuit when a train 
 occupies section 27. The short-circuiting of 12 also short-cir- 
 cuits 13 through back contact 16, the latter being in shunt with 
 13. When the train reaches section 28, however, 12 is energized 
 and 16 opened, B receives current from 14 through the axles 
 
38 
 
 AUTOMATIC BLOCK SIGNALS 
 
 of the train, which thus act as a single-pole switch. 5 is a main 
 battery, 10 the distant semaphore, and 11 the home. 
 
 In Fig. 43 much the same circuit disposition exists, an indi- 
 cator, 28, and two single contact switch instruments, 29 and 30, 
 being introduced at the main-line crossover switches, 31. Both 
 of these latter are also in series with the home line, 2, and the 
 semaphore apparatus at 33, which is the usual practice for main- 
 line switches, so that when either is open the home blade at 33 
 will be held at danger. One side of all main batteries and 
 switch indicators is connected to the common line. The dia- 
 
 FIG. 43 
 
 grammatic arrangement of binding posts is as it actually occurs 
 in the relay boxes. 
 
 A circuit arrangement for double-track application is given 
 in Fig. 44. Two signals, 7 and 6, the latter a distant, protect 
 a home block consisting of several sections, three of which are 
 represented; the second containing a switch, 11. There are 
 four main batteries, 1, 2, 3, and 4, which are, respectively, 
 for operating the home-signal motor, control relays, switch 
 bells, and distant signal motor. A vibrating bell, 10, is placed 
 at the switch, which rings and consequently gives warning not 
 to throw the switch when a train is in the second section from 
 the latter. If the switch is thrown, however, the home signal 
 
NORMAL DANGER CIRCUITS 
 
 39 
 
 moves to the stop position. This will be announced when the 
 section is clear by the continued ringing of the bell, which in- 
 dicates, as will presently appear, that the signal has been set. 
 
 o> 
 
 FIG. 44 
 
 When 7 is cleared, the contacts, 13, will be closed, thus ringing 
 10. 13 is in shunt with the armature, 19, of track relay, 12, while 
 the armature contacts, 18, of this relay are in series with relays 
 15 and 27, battery 2, and armature 23 of the track section, 28, 
 relay 5. Two line wires are used, and track circuit-control is 
 
40 AUTOMATIC BLOCK SIGNALS 
 
 also effected by relays 8 and 14, whose armature contacts, 26 
 and 20, are in series with the track batteries. 
 
 Suppose a train enter section 28. Armature 23 will fall, thus 
 sending a current from 2 through 15 and 27, through whose 
 front contact armature, 24, a current passes from 4 to the 
 distant-signal motor, and from 1 to the home-signal motor, by 
 way of 16. The latter action causes the home-circuit control- 
 ler, 13, to be operated, closing the circuit of battery 3 and the 
 bell as above shown. (If more than one switch occurs in a 
 section, the individual bells are connected in multiple.) 
 
 As the train enters the first section of 6, 14 is deenergized, 
 and 4 is disconnected from 6, due to the action of the front 
 contact, 21, even though 24 be closed. At the same time 22 is 
 closed and 20 disconnects the track battery from 5, thus main- 
 taining 23 in its lower position. If the block of 7 is occupied 
 or dangerous, 5 does not control 27 and 15, since 12 open-cir- 
 cuits battery 2, the signals both remaining in the stop or normal 
 position, and thereby hold the train. 
 
 As the train moves into the first section of 7, the latter is 
 deprived of current by the deenergizing of relay 12 (should the 
 block be unoccupied), due to the circuit of battery 1 being opened 
 at 18. The bell, 10, continues to ring, however, until the train 
 moves out of this section, due to its circuit being completed 
 through 19, which is in shunt with 13, and performs the same 
 function. When a train has indirectly deprived 27 of current 
 its lower or back-contact armature, 25, closes an auxiliary circuit 
 through the motor of 6, which short-circuits the latter, and, 
 by causing the counter e.m.f. of the armature to set up a 
 heavy current, effectually retards the semaphore, preventing 
 the inertia of the moving parts from destroying any part of 
 the system. In shunt with 25 is the armature, 22, of relay 14, 
 so that, when a train occupies the first section of 6 and a second 
 train is approaching, the retarding circuit will be closed in any 
 case, which would not be the condition if 27 were energized by 
 the closure of 23. 
 
 The motor-control relays are similarly connected for both 
 signals, this connection, somewhat modified, being shown in 
 Fig. 118, Chapter IX. Relay A is 27 in the last figure, the two 
 armatures, B and C, being connected to battery D and a sta- 
 tionary contact, F. J is an electromagnet which retards the 
 
NORMAL DANGER CIRCUITS 
 
 41 
 
 motion of the armature by having a soft iron disk rotate be- 
 tween its poles, this disk being fastened to the armature. E is 
 a contact piece moved by the semaphore's movement, and con- 
 nects in an evident manner 7, H, G, and F, at various parts of 
 its stroke. In the position shown, B is connected to the motor, 
 but not to the other side of the battery. If A is energized, C 
 will connect D to the motor, this setting the latter's armature in 
 motion. When E has passed over F, D is still connected to the 
 motor through G and H. When E reaches the end of its stroke, 
 / is connected with G, and a current passes from D through J, 
 rapidly bringing the armature to rest, due to the eddy currents 
 
 
 J 1 
 
 
 JJ 
 
 
 
 ihd ' 
 
 L 1 
 
 N? 
 
 c 
 
 := 
 
 i 
 j 
 j 
 
 5 
 
 n, 
 
 r- 
 
 UL< 
 
 T\^2^ 
 
 H 
 
 'Ml 
 
 
 V\ 
 
 BBJ 
 
 
 Pf 
 
 i 
 
 M 1 
 
 ^ 
 
 3* 
 
 I 
 
 E: 
 y 
 
 1 M'. 
 
 i i 
 
 j 
 
 - 
 
 
 ^ 
 
 < 
 
 k i 
 
 ' s 1 ~~^> 
 
 J 
 =71 
 
 Lr^ 
 
 
 /"; 
 
 
 Si 
 
 
 com mon 
 
 \\i 
 
 ' 
 
 S. 
 
 " y^ ^^ ^\ 
 
 lY//sdisS Jo-ma 2 
 
 +crossCLrms on pole c 
 FIG. 45 
 
 I b* ^ 
 
 
 ^//i or a 
 
 set up in the disk and also to its friction on the magnet 
 poles. 
 
 Fig. 45 is a delineation of a home and distant circuit for 
 single track, with train movement in one direction. A, B, and 
 C are operated when the home semaphore is cleared; A being in 
 series with the local distant, B in circuit with the preceding dis- 
 tant, and C controlling the switch indicator; the latter being at 
 danger when the home is at clear; E being the indicator battery. 
 B is also in shunt with magnet G } whose armature, with the 150- 
 ohm resistance, F, is connected to the common line, and the 
 home-actuating mechanism, H. G is energized with the distant, 
 at signal 0, through its track-controlled relay armature. Hence, 
 H is energized either from the preceding distant, or the local 
 battery, J; in any case however through the front contact of the 
 
42 
 
 AUTOMATIC BLOCK SIGNALS 
 
 four-ohm track-relay, K, the back contact governing the home 
 at signal 2. 
 
 Fig. 46 continues the above, with a siding added. P and 
 M are switch instruments, whose functions are to short-circuit 
 both tracks, with an open switch ; and to control the home sema- 
 phore at signal 2. N and are indicators, in parallel, which 
 are connected to both common and indicator lines. The main 
 battery, I, operates the home semaphores at 2 and 3. 
 
 Figs. 47 and 48 (etc.) show normal danger circuits in conjunc- 
 tion with all-electric interlocking, as more specifically set forth 
 in Chapter XIV. These occur at Union Street, Allentown, Pa., 
 on the Lehigh Valley Railroad, at its intersection with the 
 Allentown Terminal Railroad; and in addition to this, several 
 sidings and branch lines. The working-circuit network emanates 
 
 from a signal cabin, within which is the interlocking machine 
 and its accessories. Three separate common lines, A, B, and 
 C, with relay control, are used. Motor armatures are designated 
 by A, brake magnets by BM, and signals, switches, and derails 
 by numerals. Dwarf signals, such as 4, 18, 47, etc., are used 
 subsidiary to main and branch-line signals, and are of lesser size. 
 84 and 85 are vibrating bells under the control of track func- 
 tions preceding those shown; 86 is a storage battery; 87 a west- 
 bound distant indicator with shunted bell; 88 a westbound 
 track indicator; 89 an east-bound track indicator; and 90 an 
 east-bound distant indicator with a bell in multiple; 931 and 
 
NORMAL DANGER CIRCUITS 
 
 43 
 
 932 are disk signals, whose "hold clear" coils have a resistance of 
 600 ohms; 91 and 92 are 16-c-p. 110-volt incandescent lamps, 
 
44 
 
 AUTOMATIC BLOCK SIGNALS 
 
 controlled by signals 1 and 51 respectively, and form a visual 
 indication at the tower of movement thereof. 
 
 93, 94, 95, etc., are slot magnets which allow the signal arm 
 to return to stop when deenergized. The remainder of the cir- 
 
NORMAL DANGER CIRCUITS 
 
 45 
 
 cuits are common to those preceding, or will be more compre- 
 hensively evident on consulting Chapter XIV. 
 
 In Fig. 49 is developed a normal danger three-position signal 
 circuit for six consecutive signals, with a train in each of the 
 blocks of K, P, and S, and a crossover switch, Y, in that of N. 
 The connections at all of the blocks are similar; with the excep- 
 tions of the functions, D, E, F, G, H, and J, which are intro- 
 duced for variation. Describing the apparatus at K, we have, 
 
 indicator 
 
 FIGS. 47, 48 (III) 
 
 the three-position signal relay, 3P, track relay, T, motor, M, 
 clutch-magnet, C, lock-magnet, L, main-battery, B, and the con- 
 tact-arrangement, Z, operated by 3 P. This latter changes the 
 interconnection, so that at each indication position we have a 
 proper circuit-arrangement. Three stages of contacts exist: (1) 
 when the semaphore is at clear, and 4 is connected to 5, as at W; 
 
 (2) when the blade is at normal or danger, as at X (a similar 
 condition obtaining when the arm is at caution, as at 7); and 
 
 (3) when the semaphore is at danger with a train in its block, 
 as at Z; and 1 is in contact with 2. 
 
46 
 
 AUTOMATIC BLOCK SIGNALS 
 
 It should be noted that the 3P relays are in multiple with 
 the succeeding main batteries through the front-contact arma- 
 tures, U, of the track relays; and that in order to energize the 
 
 motor, clutch, and lock magnets it is necessary for the back con- 
 tacts, R, of the preceding relays to close. This energization 
 will not occur unless all other conditions are normal, an impossi- 
 
NORMAL DANGER CIRCUITS 
 
 47 
 
 bility if the track is short-circuited or open by any cause. The 
 front contact, A, of the 3P relays is for energizing the lock 
 
 
 -0 *f- 
 
 
 4 
 
 
 
 
 c 
 
 , * 
 
 
 
 
 
 
 fc 
 
 
 
 
 
 
 r 
 
 * 
 
 3 
 
 
 I 
 
 
 
 
 
 
 
 
 
 
 t 
 
 
 
 
 
 
 
 
 
 S 
 
 
 , 
 
 
 -f 
 
 
 
 cc 
 
 magnets, and then only by way of R and at such times as the 
 motor and clutch magnets are not in circuit. In this case three 
 line wires are necessary, as 8, 9, and 10. 
 
48 
 
 AUTOMATIC BLOCK SIGNALS 
 
 Fig. 50 gives the circuit connections peculiar to a control 
 scheme for semi-automatic home ; advance, and distant sema- 
 
 phores. The home blade, N, is controlled by lever 1, and when 
 the latter is thrown, contact C is closed; and, if D be then 
 
NORMAL DANGER CIRCUITS 
 
 49 
 
 momentarily pressed down, B will be energized by the shunt- 
 ing of battery L. This causes a current to pass through A, pro- 
 viding K is on closed circuit, even though D be released. When 
 lever 2 is thrown, E is closed, and if F is then closed for a moment, 
 
 FIG. 50 
 
 a current will pass through the low-resistance winding of J from 
 battery M. This raises its armature, throwing in circuit the 
 high-resistance winding and the shunt-track circuit of the 
 distant 0, energizing G, and, in the proper sequence, H. 
 
CHAPTER IV. 
 
 NORMAL CLEAR CIRCUITS. 
 
 IN all normal clear systems, the signal semaphores or disks are 
 in the clear position at all times except when a train is in the 
 block protected, or an otherwise dangerous condition exists. 
 This implies that the clearing or retaining devices are normally 
 in circuit with the power battery, and that their control is 
 primarily effected with front relay contacts. 
 
 In Fig. 51 a diagram of one form of polarized system of normal 
 clear signals is given. C is a two-arm semaphore signal, E being 
 
 B 
 
 J_ I v 
 
 FIG. 51 
 
 the distant, and F the home blade. F indicates the condition 
 of block A-B, to one end of which the polarized track relay, 7, 
 is connected, this relay deriving current of a given polarity from 
 the track battery, R, at B. This circuit is through the rails of 
 the track and the pole-changing switch, P, which is actuated 
 mechanically (in the direction shown by the contacts) by the 
 home blade, H, of signal D. 
 
 The distant blade, G, is not shown connected, to simplify the 
 circuits; while the pole changer is omitted at C for the same 
 reason. Relay S is connected across section V, in the block 
 controlled by H, and derives current from a battery at the 
 
 50 
 
NORMAL CLEAR CIRCUITS 51 
 
 other end of this block, a polarity changer being also inter- 
 posed. 
 
 Relay S, through the armature T 7 , and a front contact, con- 
 trols the flow of current from the signal battery U, to the home 
 blade, so that when S is deenergized T falls, and by opening the 
 circuit of U, causes H to move to the danger position. 
 
 If a train occupies the block between A and B, R will be 
 short-circuited, thus deenergizing / and allowing the neutral 
 armature, K, to drop, thereby open-circuiting the signal battery, 
 M, and causing F to move to the danger position. is a series 
 switch open-circuited mechanically by the motion of F; hence 
 E, deriving current from M through this switch, moves to the 
 caution position. 
 
 The neutral armature, K, is connected to J by the jumper 
 wire, N, J being the polarized armature of 7, whose direction of 
 motion, and consequently of contact, depends upon the polarity 
 of the current which I receives. With P in the position shown, 
 J will be in contact with its contact finger ; but if P be reversed, 
 / will be on open circuit. This latter condition will evidently 
 occur if a train be in section V. 
 
 When the train passes out of the block of H, it moves to the 
 clear position, by the action of relay, S, which restores current 
 to this blade. This causes a shifting of the pole changer, which 
 returns to the position shown in the diagram. The reversal of 
 polarity causes J to move to its normal position, thus restoring 
 E to the clear position. 
 
 Fig. 52 shows diagrammatically the arrangement of a block 
 consisting of two insulated track sections, A-B and B-C; the 
 home and distant semaphores being on separate posts. Such 
 an arrangement is employed where the blocks are of considerable 
 length, and wherever it is most desirable to locate the home and 
 distant blades on independent posts, the distant semaphores 
 being placed between the home signals. 
 
 Upon a train's entering the section, A-B, the armature, H, of 
 track relay G falls, thus open-circuiting the main battery, T, 
 and causing D to move to the danger position. When the train 
 enters the section, B-C, the track relay / is short-circuited, thus 
 allowing its armature, J, to fall, and, by open-circuiting track 
 battery M, depriving section A-B of battery current. Thus 
 G remains deenergized while D remains at the danger position. 
 
52 
 
 AUTOMATIC BLOCK SIGNALS 
 
 The presence of the train in section B-C also allows the neutral 
 armature, K, to fall, hence E moves to the caution position, 
 being deprived of current from the main battery, S. 
 
 ABC 
 
 II 
 
 H 
 
 FIG. 52 
 
 The polarized armature, L, is not directly affected until the 
 train has passed the insulating joints at C, when, by N being 
 short-circuited, P falls, thus moving F to the caution position 
 by open-circuiting the main battery, 0. The motion of F 
 throws the polarity reverser, Q, over, thereby reversing the po- 
 larity connections of R to the rails of section B-C, and causing 
 L to move away from its contact, maintaining E in the caution 
 position. This will continue until the train passes out of the 
 section controlled by F, when E will return to clear. 
 
 FIG. 53 
 
 The consecutive connections of home and distant normal clear 
 signals for one side of a double-track line are shown in Figs. 53 
 and 54. At signal 1619, D operates the distant blade and H 
 
NORMAL CLEAR CIRCUITS 
 
 53 
 
 the home semaphore. In reality, these are motor-slot magnets, 
 the motor itself being operated through an auxiliary circuit, 
 which consideration, however, does not affect the fundamental 
 connections. A and B are closed by the clearing of the home 
 board, A being in series with the distant at 1619, and B in series 
 with the distant at 1609 through the line wire. H is operated 
 by current from the power battery, C, through the armature of 
 track relay E. Hence, when the block of 1619 is occupied, H 
 will be deprived of current, and A simultaneously opened, thus 
 throwing both semaphores to the stop position. 
 
 The connections at 1629 are similar to the above, a series 
 relay, F, being added, however, whose armature is raised when 
 
 FIG. 54 
 
 current parses to the switch indicators, G and 7, in Fig. 54, 
 through the common and indicator line-wires, armature / at 
 1639, and battery M. The remaining circuits at 1639 and 1649 
 are practically identical with the preceding. In both dia- 
 grams a common line-wire is introduced. This is the usual 
 practice with line-wire systems, one side of the main batteries 
 and switch indicators being connected to it, thus economizing 
 on the extra copper that would otherwise be required. 
 
 In Figs. 55 and 56, 2, 4, 6, and 8 are normal clear home and 
 distant signals controlled through line wires and applied to one 
 of the tracks of a double-track railroad. But one track relay 
 is used in each block, the contacts, C, of these relays being in 
 series with the home operating device. B is a distant contact 
 in series with the circuit breaker, E, operated by the home sema- 
 
54 
 
 AUTOMATIC BLOCK SIGNALS 
 
 phore and controlling therewith the distant blade of the pre- 
 ceding signal. Track circuit-control is introduced at T, Fig. 
 56, this arrangement being generally interposed in long blocks 
 
 FIG. 55 
 
 having necessarily several sections. The front contact of the 
 relay, T, is in series with the track battery, M, the back contact 
 being in shunt with the latter. Hence, when T is energized, 
 
 line 
 
 FIG. 56 
 
 Jlf will be connected to and energize section N, while when T 
 is deprived of current, the back contact will short-circuit the 
 track at N, the front contact simultaneously open-circuiting M . 
 
NORMAL CLEAR CIRCUITS 
 
 55 
 
 At the switch, G, a contact, F, is arranged, so that when the 
 switch is open H will be deenergized and the home and distant 
 blades at signal 2 thrown to stop. One side of each of the main 
 batteries, 7, /, K, and L, is connected to the common line-wire, 
 as in the preceding case. 
 
 Figs. 57 to 62 show the standard normal clear overlap line- 
 
 LOCATION PLAN 
 
 WIRING DIAGRAM 
 
 FIG. 57 
 
 wire circuits on single-track for east- and west-bound movements 
 on the Southern Pacific. 
 
 In Fig. 57, A and 5 are distant signals indicating the track 
 condition when approaching a station siding. The location plan 
 shows the extent of the sections protected by the semaphores 
 and the arrangement .of the signals. Home signals, C, D, E, 
 and F, are operated by the motors and accessories having cor- 
 responding letters. A, for example, is controlled through the 
 
56 
 
 AUTOMATIC BLOCK SIGNALS 
 
 armature of relay H, the latter being connected to main battery 
 G through a front contact of track relay I, and the normally 
 closed circuit breakers at D and F, by way of one of the distant 
 line wires. 
 
 In Fig. 58 a similar arrangement is employed, a cut or relayed 
 section being introduced. This changes the extent of the con- 
 trol of the home signal preceding J in the location plan, and 
 
 LOCATION PLAN 
 
 WIRING DIAGRAM 
 
 h 
 
 FIG. 58 
 
 interposes a track relay, K, having two front and two back 
 contacts. The front points extend the function of the home 
 line wires, the back points short-circuiting L and connecting 
 one of the home lines to common. 
 
 In Fig. 59 overlaps are introduced at the west end of a station 
 siding, and a distant signal at the east end. - The distant con- 
 trol-line, M , is in series with the home-circuit controllers, N and 
 0, current being derived from the main local battery, P, an 
 independent local battery, Q, operating the mechanism. It will 
 
NORMAL CLEAR CIRCUITS 
 
 57 
 
 be noted that the negative sides of the main batteries are 
 connected to the common. This precludes the possibility of 
 dissimilar polarity, and the consequent wasteful discharge on 
 confusion of the circuit wires. 
 
 The converse of the above appears in Fig. 60, a distant signal 
 being placed at the west end (in this book, the east is always at 
 the right and the west at the left hand side, as will occur when 
 
 LOCATION PLAN 
 
 west 
 
 east 
 
 WIRING DIAGRAM 
 
 common' 
 
 FIG. 59 
 
 the reader is facing north), and overlap at the east end. The 
 independent working circuit is at R in this case, relay S having 
 three front and two back points, the latter connecting to com- 
 mon. The front points clear the signals for one direction of 
 train movement, and the back points are for the opposite sense, 
 also completing these same control circuits. 
 
 Figs. 61 and 62 show the circuit arrangements between 
 stations, with overlap. In the former, home signal T is con- 
 trolled through line 1, and U through line 2. The working ctr- 
 
58 
 
 AUTOMATIC BLOCK SIGNALS 
 
 cuit, 7, of the former is independent, that of the latter being 
 connected to the common, as are all the track-relay back points. 
 In Fig. 62 a relayed section only is shown, the line wires being 
 simply broken at the relay contacts, a location diagram being 
 unnecessary in this case. As before, the back contacts are 
 connected to common, and close the preparatory control 
 functions. 
 
 LOCATION PLAN 
 
 WIRING DIAGRAM 
 
 fc- A 
 
 FIG. 60 
 
 Figs. 63 to 66 show normal clear motor-circuits and signal 
 arrangements on the Missouri Pacific, the mile posts and signals 
 being numbered from the terminal at St. Louis. Home and 
 distant semaphores are placed on separate masts and controlled 
 through line wires. The motor connections only are represented, 
 but of course slot magnets are in parallel with the main bat- 
 teries, the motors not being in circuit except when clearing takes 
 place. 
 
NORMAL CLEAR CIRCUITS 
 
 59 
 
 At home signal 142, a circuit controller is introduced, which 
 closes the track relay upon itself when the switch is thrown, 
 
 LOCATION PLAN 
 
 X> )// 
 
 WIRING DIAGRAM 
 
 1 
 
 
 
 
 
 J- 
 
 
 
 4 i 
 
 4 
 
 common 
 
 FIG. 61 
 
 and connects the relay to the track when the switch is returned. 
 In the semaphore's stop position, also, a circuit breaker in series 
 
 BTTQ 
 
 cM 1 
 
 FIG. 62 
 
 with the motor at the distant signal, 142-D, is closed, clearing 
 the latter by energizing the motor relay. 
 
60 
 
 AUTOMATIC BLOCK SIGNALS 
 
NORMAL CLEAR CIRCUITS 
 
 61 
 
62 
 
 AUTOMATIC BLOCK SIGNALS 
 
NORMAL CLEAR CIRCUITS 
 
 63 
 
 -a 
 i 
 
64 
 
 AUTOMATIC BLOCK SIGNALS 
 
 The track relays at 172 and 171 have four sets of contacts 
 each, three of these being for the line wires; thus constituting 
 simultaneous quadruple breaks (one for each track section) 
 in these lines, which pass to preceding and succeeding signals. 
 At Valley Park two sidings appear, for train movement in both 
 directions. Signals 191 and 202 each have a circuit controller 
 and breaker, which control the track relay and section and the 
 distant signal of each respectively. At Castlewood a single 
 siding is introduced, the signal and connection arrangements 
 being similar to the preceding. It will be noted that the motor 
 batteries are not connected to the common line, since they are 
 part of independent local working-circuits. The lengths of the 
 various sections may be approximated from the mile posts. 
 
 The wiring for a one-arm distant in an overlap system is 
 shown in Fig. 67, the diagrammatic scheme of connection 
 being represented at A, NP is a neutral and polarized relay 
 (commonly termed simply a polarized relay) . The circuit con- 
 troller, Kj operated by the semaphore, is in series with the 
 motor and low-resistance (or compounding) winding, L, of the 
 slot magnet. The high resistance winding, //, is connected to N 
 and the front armature contacts, normally holding the signal 
 blade at clear. The track battery, T, is divided into two parts, 
 which are in series and have a common junction, IT. When one 
 of the neutral front contacts is closed, two cells in multiple are 
 connected across the track, of a certain polarity; and when 
 the back contact is closed, but one cell, of opposite polarity. 
 
NORMAL CLEAR CIRCUITS 
 
 65 
 
 In Fig. 68 the connections of a normal clear home semaphore, 
 with a separate distant in the rear, appear. The use of a slow 
 releasing relay admits of an ordinary slot magnet, S, having as 
 usual a compound winding. The track relay, R, has four ohms 
 resistance, and is of the ordinary neutral type. T is connected 
 to the block preceding the home signal through the polarity 
 reverser, P. The armature and front point of the slow releasing 
 relay are in series with the motor and low-resistance winding 
 of the slot, this relay being connected across the main battery, 
 Q, through the front points and armature of R. N is a circuit 
 
 FIG. 68 
 
 breaker in series with the motor, and breaks the continuity of 
 the working circuit when the semaphore is at full clear. 
 
 The relay and signal connections for a single-track normal 
 clear two -arm home and distant arrangement are shown in Fig. 
 69. The polarity reverser, R, operated by the home signal, is 
 connected to the track and track battery, T, thus controlling 
 section S of the preceding distant semaphore circuit. The arma- 
 ture and front contacts, A and F, of the slow releasing relay, 
 K, are in series with the home slot, HS, and motor, and con- 
 nected to the latter through the contact springs, A, which, with 
 B and C, are operated by the home blade. D is operated by 
 the distant, and with A is normally open. Plate G, at the 
 
66 
 
 AUTOMATIC BLOCK SIGNALS 
 
 fuse and arrester blocks, is connected to ground. The neutral 
 and polarized track-relay has two front and two back con- 
 tacts, the diagrammatic circuit-arrangement being as shown in 
 Fig. 51. 
 
 FIG. 69 
 
 A standard circuit arrangement for a normal clear wireless 
 single-arm home signal is shown in Fig. 70. A slow releasing 
 
 N 
 
 FIG. 70 
 
 slot, P, which eliminates a separate slow releasing relay, is con- 
 nected to the common wire and the armature of the four-ohm 
 track-relay, T, being in shunt with the motor, M . The latter 
 
NORMAL CLEAR CIRCUITS 
 
 67 
 
 is in series with N and operates when the latter is closed, 
 which is the case whenever the semaphore, S, is not at full clear. 
 The polarity reverser, V, governs the distant of S through the 
 polarized relay. In series with the magnets of T are the light- 
 ning arresters, R, the plate beneath which being connected to 
 ground. The main binding posts and fuse strips are shown at 
 D, to which all incoming and outgoing wires are connected. 
 
 A normal clear-wiring diagram for a one-arm home sema- 
 phore with overlaps is shown in Fig. 71. The slow releasing 
 
 FIG. 71 
 
 relay, K, is connected as already described, but a polarity rever- 
 ser is not used. Instead, the polarized relay, P, has an addi- 
 tional neutral back-contact and armature, which short-circuits 
 the track upon its deenergization. In the upper or working 
 position this armature connects the battery to the track section 
 protected by the preceding semaphore. The scheme of con- 
 nection used will be rendered clearer by the inspection of the 
 small diagram at 7 la. 
 
 FIG. 7la 
 
CHAPTER V. 
 SEMI-AUTOMATIC CIRCUITS. 
 
 A SEMI-AUTOMATIC signal is one having automatic appurte- 
 nances, but controlled from a manually operated signal, cir- 
 cuit controller, or similar devices. These are most frequently 
 used in connection with interlocking or manual signal towers, 
 and constitute either an adjunct or an extension of the latter. 
 Manual signaling cannot be effected over any great length of 
 track on either side of a cabin; hence semi-automatic distant 
 signals have been applied to most of such cases. 
 
 An interlocking plant having mechanical fixtures with elec- 
 trical control, may frequently be combined with an automatic 
 section. Fig. 72 illustrates such a composite arrangement, with 
 
 FIG. 72 
 
 a mechanical signal at danger, and a home and distant auto- 
 matic signal protecting the block immediately preceding the 
 former. N is & polarized track circuit relay, and G is a neutral 
 relay. When the track section, S, is in its normal condition, and 
 the mechanical signal is at danger, the neutral relay, A, is dee'n- 
 ergized, hence its back armature contacts control the track 
 polarity. Relay N receives a current of this polarity, and its 
 neutral armature closes the circuit of the main signal battery, 
 /, thus sending a current through L and holding it at clear. 
 
 When the home signal, P, is cleared, the circuit controller, B, is 
 closed, which raises the armature of D, thus closing the circuit 
 
 68 
 
SEMI-AUTOMATIC CIRCUITS 
 
 69 
 
 of C and sending a current through A. This reverses the 
 polarity of the track, and closes the polar contact, H, which 
 throws M to the clear position, by sending a current from / 
 through J, H, K, M, and 7. The controller, K, is operated by 
 motion of F, it being thus necessary for the home semaphore to 
 clear first. The momentary cessation of current produces no 
 effect upon the home automatic blade, because it is equipped 
 with a slow releasing slot or magnet. This retardation of move- 
 ment is produced by using in N a solenoid of high self-induction, 
 wound upon copper tubes, which thus opposes any rapid change 
 in the magnetic flux. G has a relatively high resistance, so 
 that when a train enters the section, S, it controls, it will open 
 the circuit of A and D. Hence the armature of D must be 
 returned to its upper position when A has been energized, in 
 
 n* , ru , 
 
 FIG. 73 
 
 order to close the circuit of C. Thus every train movement 
 requires that the operator raise the armature of D, otherwise 
 danger indications will be given. F and M thus operate auto- 
 matically when the mechanical signal, P, is properly manipu- 
 lated. 
 
 Frequently, a distant signal must be operated after several 
 home signals have been cleared. For this purpose a device, 
 erroneously termed a commutator, is placed upon each home 
 signal in such a series. This consists merely of a make and 
 break, similar to a controller. A series of this kind is shown in 
 Fig. 73; B, F, and 7 are commutators, which are fastened to the 
 masts of the home signals, A, E, and 77, respectively. D is an 
 interlocking lever, which controls through G the electrical func- 
 tions, and is dependent on the positions of the contacts of the 
 commutators. The local circuit, J, of the distant signal, M, is 
 
70 
 
 AUTOMATIC BLOCK SIGNALS 
 
 controlled by the line relay, P, which is actuated by the main 
 battery, C. It is evident that there may be any number of 
 similarly connected home signals in such a system. - . 
 
 In Fig. 74 a circuit controller is connected mechanically to 
 the lever, A, for the purpose of controlling the current from the 
 battery, B, the latter having in circuit the commutator, G, on 
 
 a 
 
 />H | 
 
 FIG. 74 
 
 the cleared mechanical home signal, H, and a line relay, P. The 
 armature, C, of the latter alternately connects and disconnects 
 the track battery at H from the track relay, E, controlling the 
 distant signal, D, short-circuiting the section, S, in its lower or 
 back-contact position. Current is passing through the three 
 circuits, both signals therefore being in the clear position. 
 
 In order to shunt the contacts of a relay, so that a control 
 outside of that produced by the energizing of the relay under 
 operative conditions can be effected, a spring key is used. The 
 circuit arrangement in Fig. 75 utilizes such a device. Across, 
 
 1 
 
 n H | 
 
 
 FIG. 75 
 
 or in shunt with, the upper armature of the magnetic circuit- 
 controller and indicator, D, the spring key, B, is connected. 
 The lower armature is connected across, and thus short-circuits 
 the track in its lower position, and connects the track to the 
 battery, E, in its upper position. C is a circuit controller 
 closed by the clearing of the home signal, H, and is in series 
 
SEMI-AUTOMATIC CIRCUITS 
 
 71 
 
 with D. E energizes the track relay, A, at the distant 
 signal, J. 
 
 When B is pressed downward, and C is closed by clearing the 
 home signal, a current passes through D which lifts its arma- 
 tures, the upper one maintaining the current initiated by B, 
 and the lower one sending a curreYit through A, thus clearing J. 
 
 Fig. 76 represents a scheme of connections introducing a com- 
 bined indicator and magnetic circuit controller into the circuit 
 of the line relay, P. This, given at /, consists of a solenoid, 7, 
 whose armature or core carries an indicating banner, F, to 
 which is pivoted a lever, G, provided with a knob. / is in series 
 with the contacts closed by movement of (?, hence when the 
 latter is in its lower position, current cannot pass through the 
 circuit of the line battery, B. 
 
 FIG. 76 
 
 When G is raised, the circuit is completed at /, and if the 
 circuit controller, A, is closed, a current will pass around /, and, 
 the core being energized, will maintain this condition until A is 
 open-circuited. When this current flows, D is thrown to the 
 clear position by current from the local battery, C. A } there- 
 fore, must be closed (by movement of the home signal) before 
 G is moved; should this sequence of events not occur, D cannot 
 be cleared. Since A is closed by the action which clears H, it 
 is evidently impossible for an approaching train to pass D, with- 
 out receiving a cautionary signal, unless a clear condition at 
 the cabin obtains. 
 
 Somewhat similar to the above in the arrangement of acces- 
 sories and circuits, is that shown in Fig. 77. In addition, a 
 circuit controller, P, having a positive connection to the home 
 
72 
 
 AUTOMATIC BLOCK SIGNALS 
 
 signal lever, B, is included. When B is thrown in the direction 
 of the arrow, H is moved to the clear position, and the contacts 
 at P closed. Unless the armature of the indicator, A, is raised, 
 however, E will not receive current from the line battery, C, 
 
 FIG. 77 
 
 hence D cannot be cleared. The banner on the indicator may 
 be in the form of a miniature semaphore, or a small banner which 
 appears before a glass-covered aperture in the case. 
 
 Adding a circuit controller, (7, to the above, the arrangement 
 produced in Fig. 78 is evident. This comprehends, as above 
 
 FIG. 78 
 
 stated, the addition of a protective or interlocking function, the 
 principle of the working circuits being unchanged. 
 
 An indicator and magnetic circuit controller may have its 
 movements automatically governed by the use of a setting track 
 section, in which the movement of a train sets up conditions 
 that actuate this mechanism. In Fig. 79, D is a short setting 
 section having the battery, (?, and the track relay, F. This 
 
SEMI-AUTOMATIC CIRCUITS 
 
 73 
 
 section may be of any required length, but as only a momentary 
 initial current is required for setting this function, it usually is 
 of but several rail lengths. 
 
 If the section, D, is occupied, the circuit controller, A, and the 
 indicator, (7, have no control over E. But should it not be occu- 
 pied, then, if the operator raises the armature of C, with H at 
 
 FIG. 79 
 
 the clear position, E will raise its armature, thus sending current 
 from K to D and clearing the latter. 
 
 Extension of the above principle produces the circuit diagram 
 given in Fig. 80. The lever E at the block tower is for the 
 express purpose of operating the controller with which it is 
 associated. When the home signal, H, is cleared, the contacts 
 at G will be closed. E is then thrown in the direction of the 
 
 FIG. 80 
 
 arrow, which will cause a current to flow from N through F 
 and B, if the setting section, 0, is unoccupied. Should a train 
 be in this section, however, A will be deenergized, and, by its 
 armature's falling, open-circuit N, thus depriving F and B of 
 current, and preventing D from being cleared by C. If the 
 armature of F be restored, the same condition will obtain, since 
 the circuit is still open at the armature of A. 
 
74 AUTOMATIC BLOCK SIGNALS 
 
 The circuits at a representative mechanical interlocking tower, 
 16, are shown in Fig. 81. 15 is a charging plant from which 
 power lines run to the various storage batteries. At the east- 
 bound signal, 6, the track polarity is under the control of the 
 arrangement, 4, the operating magnet being in series with the 
 contacts, 5 (closed when 6 is clear), two of the controller con- 
 tacts, 10, battery 8, and the cable. Signal 6 is operated by 
 battery 18, through line 23 and armature of 25, and signal 1 
 (at clear) by battery 3, through the polar contacts of the 
 polarized relay, 2. The latter receives current from a track cell 
 and reverser in the rear, while 24 energizes 20. Relay 21 operates 
 a reverser connected to a section preceding 14, the latter receiving 
 current from 3 through the interlocking tower. 
 
 A circuit controller, 17, is opened when the signal, 26, is at 
 danger, and is in series with the next signal in the rear. A 
 track relay, 22, is connected to the crossing track, 27, its armature 
 contact being in series with the front contacts of 20 and 28. 
 The series electric locks, 7, applied to mechanical levers, are 
 connected to battery 8 through lines 29 and 31 and common 
 line 30. Controller 13, operated by 14, is in series with con- 
 trollers 10, contacts 5, relay 4, and 21. Considering the circuits 
 already described, no difficulty should be encountered in com- 
 prehending the entire arrangement. It is evident in the above 
 circuit diagrams that a common main battery may be used for 
 numerous functions. In practice a single battery is often em- 
 ployed to furnish current for a multiplicity of such receptive 
 devices, and sometimes to energize an entire circuit network 
 of great complexity. 
 
 The normal clear circuits at the Newark drawbridge of the 
 D. L. & W. over the Passaic River are shown in Figs. 82 to 87. 
 The plans are consecutive from A to J, lines and other circuit 
 wires being numbered to render easy tracing up possible. No. 7 
 is the common line and its connections, and is shown heavy. 
 
 In Fig. 82 signals M 81 are for west-bound movements, and 
 M 82 for east bound, all four being placed upon a signal bridge. 
 Relays marked NP are both neutral and polarized, while those 
 marked H are neutral only, and have resistances of four ohms. 
 The distant blades at M 82 are semi-automatic, 40 being con- 
 trolled by the armature contacts of the 500-ohm slow releasing 
 relay 42, through the circuit breaker, 43 (operated by the home 
 
SEMI-AUTOMATIC CIRCUITS 
 
 75 
 
76 
 
 AUTOMATIC BLOCK SIGNALS 
 
 blade), the line 28, and east-bound hand switch, E, at the me- 
 chanical interlocking tower of Fig. 84. The home blade, 44, 
 operates two circuit breakers, 45 and 46, they being connected 
 in series with the distant and line 32, the latter passing to the 
 middle east-bound distant at the next bridge west. Line No. 35 
 
 -A/- 
 
 FIG. 82 
 
 passes to the west-bound middle track distant indicator for 
 Roseville Avenue, No. 26 to the east-bound distant indicator, 
 No. 31 to the west-bound (outside track) distant indicator for 
 Roseville Avenue, No. 30 to the operating mechanism of the 
 middle east-bound home signal at the next bridge west, No. 32 
 in series with the operating devices at the distant of the same 
 signal, and ^.-50 to the transmitter, T, at Fig. 84. 
 
SEMI-AUTOMATIC CIRCUITS 
 
 77 
 
 The 500-ohm slow releasing relay 47 is energized through 
 lines 29, the circuit breaker 49 at mechanical signal 16 of Fig. 
 83, the middle east-bound hand switch, M.E., at E-F, and bat- 
 teries 50; returning through the common, to which all working 
 batteries and most of the other accessories have one side con- 
 nected. Its armatures are in series with 41 through 45. Relay 
 48 is controlled from the armature of 51 at C-D through line 
 27, and controls, through its armature, both 41 and 44. The 
 signal batteries 52-53-54-55 operate the signal mechanisms 
 
 FIG. 83 
 
 they are adjacent to, the polarity reversers being operated by 
 the home blades of these signals. 
 
 In Fig. 83 the west-bound signals, M 77, are purely automatic, 
 and controlled by the polarized track-relay 56; while 15 and 16 
 are semi-automatic, and under the control of electric slots in 
 series with lines 18 and 20. Relays 57 and 62 are in multiple, 
 and connected to common and line 2, in series with the lower 
 armature or front contact of east-bound track-relay 64. Line 2 
 runs to the circuit breaker 82 of 1 D at E- F, and the track-relay 
 contact 86 at this point; the slow releasing relay 57 controlling 
 
78 AUTOMATIC BLOCK SIGNALS 
 
 the distant arm 58 through the circuit breaker 67; 60 and 66 
 being thrown by levers; 59 is controlled by 62, and is clear when- 
 ever 58 is, since 62 and 57 are in multiple. 
 
 At 63 a switch merges the east-bound and middle tracks, 
 thus removing the necessity for four-movement indication. 68 
 is the independent local battery for 58, and 69 for 59. Neutral 
 track relays, 100 and 119, produce the required track circuit 
 and line-wire control. Although it is possible to use a smaller 
 number of batteries, line wires, relays, etc., in such a com- 
 plicated situation and produce the same results, crossing of 
 circuit wires would set up conditions that would entail con- 
 siderable vexation in eradicating, while, by the use of as many 
 independent circuits as is consistent with economy, such troubles 
 seldom occur, and are more readily traced. The use of common 
 wires has often led to troublesome conditions, but such is 
 usually the result of poor insulation and careless installation 
 or maintenance. 
 
 In Fig. 84 the circuits at the mechanical interlocking tower 
 are given. E, M.E., W, and M.W. are the east, middle east, 
 west, and middle west-bound control line switches. One side 
 of each of the east switches is connected to the common battery 
 wire, B y and the multiple batteries at 50, the other sides being 
 connected to lines 28 and 29, in series with circuit breakers 49 
 and 70, and through additional circuits already traced. An 
 intercommunicating telephone instrument, 71, is in circuit with 
 72 at the drawbridge (G-H) so that communication can be 
 carried on between these points. 73 to 79 are indicators, 73, 
 74, 75, and 79 having contact armatures, the energization of the 
 magnets thus clearing not only their banners but raising also 
 these armatures. A sixty-ohm bell, 80, is closed by a back 
 contact of either 73 or 74, 81 being energized through the back 
 contact on 79. 
 
 73 receives current from battery 54, through line 25, and 
 the front neutral contact of polarized track relay 98 at A-B, 
 and is the middle east-bound indicator; 75 is the east-bound 
 home through battery 50, line 24, contact of relay 64, and com- 
 mon; 76 the east-bound advance by way of line 22, contact 
 of 86, and common; 77 the middle home through line 23 front 
 contact of 100, and common; 78 the west-bound home by line 
 21, front contact of 90, and common; 79 the west-bound distant 
 
SEMI-AUTOMATIC CIRCUITS 
 
 79 
 
80 AUTOMATIC BLOCK SIGNALS 
 
 by line 15, contact 15, cable, west-bound home indicator contact 
 of 101, to battery by the front contact of 106. 
 
 82 is the lock magnet on mechanical lever No. 16, which 
 operates the home semaphore, 16, at C-D, and is energized 
 from 50 through the front contacts of 73 and 74 in multiple; 
 that is, it releases the lever whenever either its east-bound 
 middle or east-bound distant is cleared; 83 is the lock for lever 15, 
 or east-bound outside semaphore at C-D; 84 for No. 6 at 116; 
 and 85 for No. 5 at 116. Unless 90 is energized the semaphores 
 at 117 will be in the stop position, because of the slots, 89 and 
 116, which are thus controlled by a track circuit. Circuit 
 breaker 115 is in series with line 3 and one front contact of 90, 
 also one contact of 119, circuit breaker at M-77, battery 120 
 and common, and on the other side through line 3, and con- 
 nector 3 at 88, and cable. 117 is in series with one of the front 
 contacts of 90, line 5, 5 at 88, cable, circuit breaker 126 at 7J, 
 500-ohm relay 130, and common. A slot, 97, also controls 1 D 
 (at which a derail appears) through 86, line 16 and battery B. 
 Subsidiary devices do not enter in this case, as the track circuit at 
 the approach and over the draw perform all the necessary func- 
 tions. The cable is carried to the center of the draw, the track 
 circuit connections being made so that the track forming part 
 of the draw is electrically continuous with that at the abut- 
 ments. The circuit breaker, 82, is in series with line 2, front 
 contact of 86, common, 2 at 64, east-bound hand-control switch 
 113, connector 2, cable, circuit breaker 122 at M-74 (/-/), 
 battery 121, and common. At 127 there is a derail, as also at 
 129. 
 
 Continuing on Fig. 85 (G-H), the bridge controller lock, 112, 
 is in series with a circuit breaker on lever No. 5, which is open 
 when the bridge is locked, so that when the former is energized, 
 the bridge is not in its safe position. A single-stroke bell, 107, 
 is connected to the armature contact of approach indicator 105, 
 so that when the latter has a current passed through its coils, 
 the gong will be struck once, this occurring through line 37, 
 whose connections will be shown later. 109 receives battery 
 current through the back contact of the west-bound distant indi- 
 cator, 106, and 108 through the same contact of the east-bound 
 distant indicator, 102. The bridge indicator, 104, is in series with 
 the wire 36 and the signal battery at 9 D, through the cables; 
 
SEMI-AUTOMATIC CIRCUITS 
 
 81 
 
 103 is the east-bound home indicator connected to battery 50 
 and line 4; the circuit being completed through one of the front 
 contacts of 86 and common. The lock magnet, 111, is connected 
 
 H 
 
 FIG. 85 
 
 to lever 9 of that signal, and is in series with the front contact of 
 106. The west-bound distant indicator 106 is connected by line 
 1 to the cable, one contact armature of 135, and to the west- 
 
82 
 
 AUTOMATIC BLOCK SIGNALS 
 
 bound home indicator at Harrison, the next signal point 
 east line 11 E, operating the west-bound distant signal at 
 this point. 
 
 In Fig. 86 (I-J) the east end of the cable and connections 
 
 are shown with the mechanical semaphore, 9 D, and the automatic 
 signals, Af-74 and Af-69. The four-ohm track relay, 135, con- 
 trols east-bound signal lf-69, 137 being the working battery. 
 A high-resistance slow-releasing magnet, 136, is in series with line 
 
SEMI-AUTOMATIC CIRCUITS 
 
 83 
 
 33, circuit breaker 124, cable, west hand-switch 114, and battery 
 145; while a similar magnet 130 is in series with the circuit 
 breaker, 126, and line 5 (all three circuit breakers are closed 
 when 9 D is cleared). 9 D is also under the control of slot 128, 
 which is energized through the track relay contacts. Circuit 
 breaker 125 controls 140, and 138 the preceding distant sema- 
 
 t Sig 9O 
 
 FIG. 87 
 
 phore, while 139 is in series with the distant at lf-69. A polar- 
 ized relay, 141, is used at Af-74, battery 121 operating both home 
 and distant semaphores. 
 
 The track circuit and other connections at the lower deck of 
 the draw appear in Fig. 87, with two manual signals, 9 D and 
 10 D. With the foregoing description in view, it need not be 
 dissected. 
 
CHAPTER VI. 
 BATTERIES. 
 
 THE primary cells most generally used in signal installations 
 are the following: (1) Gravity; (2) Gordon; (3) Edison. All 
 are of the closed-circuit type; that is, they are capable of 
 withstanding continuous full normal-current discharge. 
 
 Open-circuit cells are but little used; for, while certain work 
 is intermittent in character, it has been found that cells of this 
 type are not to be depended upon. For ringing electric bells at 
 places where inoperation will not result in serious consequences, 
 the Leclanche or sal-ammoniac cell has been applied with re- 
 strictions. 
 
 In the gravity cell, which is of the two-fluid type, the different 
 specific gravities of the liquids used is the only principle involved 
 in keeping them apart; porous cups and diaphragms being 
 thereby eliminated. These liquids are a saturated solution of 
 copper sulphate and a dilute solution of zinc sulphate and sul- 
 phuric acid, the latter being formed only during the action of 
 the cell, which is shown in Fig. 88. The copper element, C, 
 rests upon the bottom of the containing jar, and is connected to 
 the external circuit by an insulated wire. The copper is partly 
 covered with crystals of blue stone or copper sulphate (CuSO), 
 these crystals being surrounded by a strong solution of copper 
 sulphate. Above this latter solution, and distinctly separate 
 from it, is the solution of zinc sulphate, in which the zinc, Z (a 
 common type of which is shown also at D), is immersed. This 
 zinc is supported by the bent bare copper wires, G, which are 
 cast in the former. The action of the cell is as follows : 
 
 When the external circuit is closed, the small amount of 
 sulphuric acid (or water if the former is not present) attacks the 
 zinc, forming zinc sulphate and hydrogen. The zinc sulphate 
 remains in the upper part of the liquid, while the hydrogen 
 passes to the copper sulphate, and thus forms sulphuric acid 
 
 84 
 
BATTERIES 
 
 85 
 
 and metallic copper. The copper is deposited upon the copper 
 element, while the sulphuric acid rises and attacks the zinc, 
 this cycle being repeated as long as the external circuit is closed. 
 These reactions are expressed as follows : 
 
 Zn + H 2 S0 4 = ZnS0 4 + 2H. 
 2H + CuS0 4 = H 2 S0 4 + Cu. 
 
 When the water of the solution is decomposed, oxygen is liberated. 
 The copper which is deposited upon the copper element must be 
 loosened each time the cell is renewed, or the accumulations 
 
 FIG. 88 
 
 will become too solid for removal. When a gravity cell is in 
 proper condition, the blue line of separation should be midway 
 between the two electrodes. 
 
 The e.m.f. of this cell on open circuit is 1.07 volts; and the 
 internal resistance from about .5 to 3 ohms. This will give a 
 current on short circuit of from .3 to 2.5 amperes. The cell is 
 most commonly used for track circuits on account of its perfect 
 electrochemical depolarization. To a certain limit of saturation 
 of the upper or zinc sulphate solution, the greater the con- 
 tinued demand the more satisfactory the operation. A disad- 
 vantage of the cell, however, is the high internal resistance. 
 
86 BATTERIES 
 
 The loss this entails depends upon the resistance of the circuit 
 to which it is connected; since this loss (C 2 R) depends upon the 
 relation of the internal resistance to the total resistance. 
 The internal resistance of a gravity cell being 0.5 ohm, the 
 
 c 2 
 maximum - factor that can safely be allowed is 2, which at .30 
 
 gives an economic power valuation of 2.2. 
 
 In the Gordon cell, the elements are iron and zinc, while the 
 exciting liquid is a strong solution of sodium hydrate or caustic 
 soda, NaOH. The containing jar is either glass, porcelain, or 
 enameled steel, depending upon the conditions to be met. 
 Steel and porcelain have a longer life, and are much less liable 
 to failure during recharging and operation than glass, but the 
 operation of the cell is not visible, as is desirable to determine 
 the point when renewal must be accomplished. 
 
 Fig. 89 illustrates a 300-ampere-hour cell, such as is most 
 frequently used for signal and grade-crossing circuits, the jar 
 being 6 in. by 8 in. in size. Z is the 
 positive zinc element, which is a sheet 
 bent to a cylindrical form; it being of 
 about one-eighth of an inch in thickness. 
 This is thoroughly amalgamated, to pre- 
 vent local action, and is supported on 
 three porcelain lugs, P, fastened to the 
 perforated cylinder, D, which it sur- 
 rounds. This latter is partly filled with 
 a flaky oxide of copper (CuO), the iron 
 and this compound forming the negative 
 element. Contact is made to Z) by a 
 binding post or connector, the threaded 
 connection to which is screwed into a 
 nut in the top of the cylinder. The sheet iron cover, C, supports 
 D and Z by the binding action of two porcelain washers, A, one 
 above and the other below C. The zinc is connected to the 
 external circuit by the insulated wire, W, which is riveted to 
 the former and further insulated from C by a small porcelain 
 bushing. The riveted connection is covered with asphaltum 
 to prevent local action at the junction of the copper and zinc. 
 When the cell is renewed, the entire cylinder and contents, 
 also the remaining zinc, is thrown in a scrap pile. Formerly, 
 
BATTERIES 87 
 
 the exhausted copper oxide was removed and replaced, the 
 entire arrangement being dismantled to do this; resulting in 
 much labor and, without care, painful sores on the hands of the 
 battery man. Thus one of the objectionable features of the 
 sodium hydrate cell has been removed. 
 
 An exciting solution of from 20 to 25 per cent is employed; 
 in other words, three or four pounds of water to one pound of 
 pure caustic soda. The copper oxide and zinc are so propor- 
 tioned that all the elements are exhausted at once. A heavy 
 mineral oil is used to cover the surface of the exciting solution, 
 as this latter has a strong affinity for the C0 2 of the atmosphere, 
 which if not otherwise prevented would result in rapid deterio- 
 ration of the cell. The reaction is shown in the formula: 
 
 2NaOH + C0 2 = Na 2 C0 3 + H 2 0. 
 
 The sodium carbonate (Na 2 C0 3 ) thus formed is not only of 
 little value in setting up an e.m.f., but it also is of a creeping 
 character, crystalization taking place over the edges of the jar 
 and cover, resulting in rapid destruction of the latter. 
 
 During the action of the cell, sodium zin'cate is formed as 
 follows : 
 
 2NaOH + Zn = Na 2 Zn0 2 + 2H 2 . 
 
 The hydrogen passes to the copper oxide and forms water 
 and metallic copper, thus: 
 
 2H + CuO = Cu + H,0. 
 
 The Edison cell is also of the single-fluid type, and now em- 
 ploys an exciting solution of caustic soda or sodium hydrate, 
 NaOH. In its action it is somewhat similar to the Gordon, but 
 of a different mechanical construction. Formerly, caustic pot- 
 ash solution was used, but as this is even more difficult to handle 
 than the sodium compound, it has been abandoned. Fig. 90 
 shows the cell in part section. A cover, B, of porcelain, has a 
 recess which fits into the top of the containing jar. In the 
 center of this cover there is a boss, on each side of which stems 
 or lugs, L, incorporated with the zinc plates, Z, are securely 
 clamped by the thumbscrew connector, C. Within a slotted 
 frame of copper, F, are placed two porous, compressed, and 
 beveled plates of cupric oxide, 0, with surfaces reduced to the 
 
88 
 
 AUTOMATIC BLOCK SIGNALS 
 
 B 
 
 -L, 
 
 FIG. 90 
 
 metallic state for increased conductivity. These plates have 
 a binder of magnesic chloride, and are secured in place by the 
 copper thumb bolts, N. Two insulating tubes of hard rubber, 
 
 T, are placed on part of the frame 
 which emerges from the liquid, and 
 prevent the current from leaking 
 across the surface of the liquid to 
 parts of opposite polarity, also pro- 
 tecting the frame from corrosion at 
 the junction of the oil and solution. 
 The liquid is covered as before with a 
 heavy mineral oil, and the external 
 circuit wires are fastened to the con- 
 nectors, A and C. 
 
 The cell is renewed by removing 
 the zincs, oxide plates, and solution, 
 and replacing by new elements, care 
 being taken to have all nuts and 
 connections tight. The entire old 
 solution is thrown away and the new liquid substituted, a 
 fresh bottle of oil being poured over the surface. Before 
 replacing the new elements, they should be dipped in clean 
 water, to prevent the oil, which is of high viscosity, from 
 adhering when they are immersed in the solution. 
 
 The water used in renewing all cells should be taken from a 
 running stream or hydrant, as stagnant water contains vege- 
 table and animal impurities which render it unfit for battery 
 purposes. For this reason it is not practicable to locate barrels 
 filled with water near the battery chutes, as animalculse soon 
 manifest themselves. Spring water, is not always valuable, as 
 it may contain mineral substances whose reaction is deleterious 
 to the proper action of the cell. When mixing caustic soda 
 solution, the soda should be slowly poured into the water, and 
 the latter rapidly stirred at the same time, as failure to do this 
 will result in its falling to the bottom and solidifying. Should 
 any of the solution get on the hands or face it may be readily 
 eliminated by applying a vegetable or animal oil or grease, 
 which is thus converted into soap. If glass jars are used, they 
 should be placed on dry wood or ties, to prevent cracking at 
 the bottom, owing to unequal expansion. 
 
BATTERIES 89 
 
 The surface of the liquid should be about one inch above the 
 top of the zinc and oxide plates, for if the latter project above 
 the liquid, the bare parts will be rapidly destroyed. Also fine 
 particles of metallic copper may fall from the oxide plates and 
 by floating upon the plane of separation of the oil and solution, 
 ultimately short-circuit the cell. The condition of the oxide 
 plates may be ascertained by picking into them with a sharp 
 knife. Should they be copper colored throughout, they are 
 exhausted; but if the central portion is black, they are still of 
 use, the continuity of life depending upon the relative thickness 
 of this inner black layer. Using an exhausted set of plates 
 results in rapid depolarization, while it is not advisable to use 
 plates that have been left in the air and consequently partially 
 reoxidized, as this natural oxidization occurs only superficially. 
 
 A 300-ampere-hour capacity has an internal resistance of 
 .025 ohm, a working voltage of .667, a continuous-current de- 
 livery of 6 amperes, a short-circuit current of 26.7 amperes; 
 
 c 2 c 2 
 
 consequently a factor of 17.78, and a factor of 5.34, when 
 v pr 
 
 p = .30. The low internal resistance is advantageous when 
 the cell is called upon to deliver heavy currents; that is, when 
 connected to a low external resistance. The ratio of the energy 
 lost in the cell to the total energy expended is then very low. 
 
 The disadvantages of the sodium hydrate cells are the caustic 
 nature of the exciting liquid, the low terminal voltage, the 
 rapidity with which they give out, and the excessive heat caused 
 by the dissolving of caustic soda in water. The indication that 
 a cell needs renewing is the segregation of crystals of sodium 
 zincate upon the zinc element, a condition occurring without 
 much warning. The use of oil on the surface of a liquid is also 
 rather troublesome, as the inside surface of the jars must be 
 frequently cleaned. Also a large percentage of the cost of 
 operation is in scrap which is not really utilized. 
 
 The advantages are the uniformity of operation, freedom 
 from local action, low internal resistance, constancy of current 
 output, ability to withstand low temperatures, the absence of 
 noxious or combustible vapors, and the adaptability for heavy 
 current output. 
 
 Storage cells have many advantages over primary cells which 
 make them particularly adaptable to certain phases of signaling. 
 
90 AUTOMATIC BLOCK SIGNALS 
 
 Where large amounts of energy are required, and it is not advis- 
 able to install a separate generating plant, storage cells may be 
 economically applied, being charged by a portable generating 
 set. Such an arrangement has the advantage of a large and 
 steady output, with a smaller number of cells than the closed- 
 circuit primary cells we have considered can have. The average 
 e.m.f. of a storage cell is 2 volts, so that three Edison cells can 
 be replaced by one storage cell, as far as voltage is concerned. 
 When a stationary generating set is used, the signal batteries are 
 charged through the aid of line wires which run from the plant 
 and include the cells in series. 
 
 Most of the accumulators used in signal practice have positive 
 and negative plates of lead and an electrolyte of dilute sulphuric 
 acid (four parts of water by volume to one part of acid, giving 
 a specific gravity of 1.2). The lead plates are " formed " 
 mechanically or electrically, and are fastened together in sub- 
 stantial shape. 
 
 Storage cells are rated according to the number of ampere- 
 hours they are capable of discharging until the terminal e.m.f. 
 of a cell falls to 1.8 volts, the e.m.f. when fully charged being 
 2 volts. However, since sulphating sets in below 1.9 volts, they 
 should never be discharged until the e.m.f. becomes less than 
 this figure. 
 
 A 300-ampere-hour cell may be charged at a normal current 
 of 30 amperes, the charging continuing for 10 hours; which 
 also represents the normal rate of discharge. Smaller capacities 
 require less current; a 50-ampere-hour cell taking 5 amperes 
 under normal conditions. It is better practice to prolong the 
 charging time by decreasing the current. Better results are 
 also obtained when discharging at a low rate, a 150-ampere-hour 
 cell being capable of delivering 190 ampere-hours with 38 hours 
 allowed for both charge and discharge, and only 120 ampere- 
 hours at 5 hour discharge rate. 
 
 When charging, the e.m.f. of the generator should be 10 per 
 cent greater than the total e.m.f. of the cells when charged. 
 The resistance of a cell is very low (.003 ohm for an average 300 
 ampere-hour cell), hence it is necessary to include a resistance 
 of some kind in series when charging. To illustrate, suppose 40 
 such cells were connected in series on a 110-volt circuit. The 
 cell e.m.f. which will oppose that of the supply circuit would be 
 
BATTERIES 91 
 
 40 X 1.9, or 76 volts. Then 110 76 = 34 volts; resulting in 
 a flow of 34 -^ (40 X .003) = 283.3 amperes, which of course 
 is an excessive current. With a resistance of one ohm in series, 
 on the other hand, the current would be 34 H- 1.12, or 30.3 
 amperes, which is a normal value. 
 
 Usually the line has sufficient resistance to prevent an excessive 
 current flow; but jn any event it requires careful calculation. 
 It is advantageous to have a small variable resistance (rheostat) 
 in circuit so that the charging current may be adjusted to the 
 required value. 
 
 Accumulators should be installed in a dry place, having 
 an average temperature of about 70 F. Charging may be 
 continued until gasing sets in, a phenomenon caused by the 
 liberation of hydrogen, which gives the electrolyte a boiling 
 appearance. High insulation must be maintained; otherwise 
 the leakage factor will be high, and trouble encountered with 
 foreign currents in the track circuits. 
 
 Storage batteries may be charged from commercial power 
 circuits, or through the medium of a portable generating plant. 
 In the latter case, gasoline engines are preferable, the generator 
 being direct driven, except in the case of small units. If alter- 
 nating current is available, it is converted to direct at the proper 
 voltage by a motor generator or mercury rectifier. In all- 
 electric interlocking 110 volts is the standard pressure; 55 
 storage cells being connected in series to obtain this e.m.f. The 
 capacity of the individual cells depends upon the work they 
 perform in a given time, usually 24 hours, the cells being 
 charged so often. With such installations, a switchboard is 
 necessary. Such a board should contain an ammeter, volt- 
 meter, pilot lamps for indicating grounds, circuit switches, 
 charging rheostat, fuses, and circuit breakers (both overload 
 and reverse current). 
 
 A mercury converter or rectifier is now used for charging 
 storage signal-batteries from alternating-current mains. This 
 device suppresses the negative wave of the alternating side and 
 converts it into a pulsating direct current, with intervals of par- 
 tial current cessation. Such a current can readily be employed 
 for charging purposes, although it could not be used directly on 
 the signal motors or relays, due to the resistance offered by 
 such inductive devices; with consequent heating and loss of 
 
92 
 
 AUTOMATIC BLOCK SIGNALS 
 
BATTERIES 
 
 93 
 
 energy from eddy currents and inconstancy of the available 
 e.m.f. 
 
 Mercury rectifiers should be mounted upon a switchboard, 
 containing the main switches and connections, with a trans- 
 former, having a variable secondary voltage. The charging 
 wires run either to separate portable battery sets, or to the 
 charging line. This arrangement is not only economical, but 
 
 FIG. 92 
 
 practicable; and transmission may be effected over great dis- 
 tances, and from isolated points, at any primary potential. 
 
 Fig. 91 is the plan of a charging arrangement used on the 
 D. L. & W. is shown. The charging plant is located at Hal- 
 stead, N. Y. (192.5 miles from New York City), the total 
 territory covered being 17.7 miles. Forty-four two-arm signal 
 mains are charged in this fashion; A, B, and G being slotted 
 mechanical signals. 
 
 While nearly all forms of primary batteries used in signal 
 
94 AUTOMATIC BLOCK SIGNALS 
 
 practice are of the non-freezing types, it is advisable to make 
 battery shelters or houses as impervious to cold as possible. 
 The internal resistance of cells increases with decrease of tem- 
 perature, and when the surrounding air has a temperature below 
 that of freezing, the action is sluggish, the current discharge 
 being low and the requisite circulation of the exciting liquid 
 poor. In Fig. 92, A is a wooden battery tank or well which 
 may conveniently be installed below ground, with the top pro- 
 jecting above the surface. The latter is weatherproof and 
 provided with a hinged cover, while the cells are arranged in 
 tiers, upon ventilated shelves, for ease of inspection and renew- 
 ing. The inner base is provided with drainage holes, the scrap 
 material being contained in suitable boxes. 
 
 At B and C a sectional and side elevation of a common type of 
 battery house is given. The shelves a are arranged on the inside 
 walls, giving a maximum of room for the batteryman's opera- 
 tions. The walls are lined with felt, asbestos, or similar material, 
 6, for protection from the varying temperature of the outer air. 
 With this arrangement inspection is rapid, and safety from high 
 water assured. 
 
CHAPTER VII. 
 THE TRACK CIRCUIT. 
 
 THE track circuit includes that part of the control feature 
 which is affected by the presence of a train within a block. It 
 consists of insulated sections of track across which relays and 
 batteries are connected so that the energization of the latter 
 cannot be effected when the rails are connected by a pair of 
 wheels and axle, or by other conditions which have been prede- 
 termined as dangerous to a rapidly moving train. 
 
 The simplest imaginable track circuit, combined with an old 
 style of disk signal, is shown in Fig. 93. The section of track, 
 
 FIG. 93 
 
 J, is insulated from the adjacent track sections by the insulating 
 joints, H and 7, and is connected to a relay, D, and battery, C. 
 The latter thus energizes D through the rails as a circuit. This 
 causes the armature, G, to press against a contact in series with 
 which is an electromagnet, E (controlling the clockwork which 
 operates a banner in signal A), and a local battery, F. If a 
 train occupies /, D and C will be short-circuited, thus deener- 
 gizing E and holding the clockworked banner at danger or stop. 
 B is another similar signal at the subsequent block; train 
 movement being in an easterly direction. 
 
 Continuing the applicatiqn of the track circuit principle, we 
 have in Fig. 94 a more comprehensive arrangement for tower 
 
 95 
 
96 
 
 AUTOMATIC BLOCK SIGNALS 
 
 application than has been heretofore considered. A track relay, 
 G, controls movements of the distant semaphore and is con- 
 nected through the track to battery F. When the home signal, 
 H, is at clear, the controller, B, is on closed circuit, and therefore 
 determines (depending also on the position of the magnetic cir- 
 cuit controller's ^(A) armature) the current which flows through 
 the control electromagnet, D, from battery C. 
 
 If a train be on section T, then the track relay at G will be 
 deenergized, and the distant blade will move to caution. Also, 
 battery F will be short-circuited, hence the armature of E must 
 fall, which, in consequence, demagnetizes both D and A. If 
 the operator should move the armature of A up, it will not 
 remain there, owing to C being still on open circuit. Thus the 
 
 FIG. 94 
 
 home signal cannot be cleared except with full knowledge of 
 the electrical indications. 
 
 Before track circuits were introduced, track instruments were 
 employed to effect the circuit changes incident to the movement 
 of a train. In purely automatic practice they have been aban- 
 doned, but are still used where track bonding has not been 
 resorted to for minor electrical purposes, such as the ringing of 
 a bell, or movement of an indicator. Fig. 95 shows this device 
 in section, it consisting of a hollow upright placed a short dis- 
 tance from the rail, which contains a rod, C, forced downward 
 by a spring and carrying at its upper end a contact button which 
 engages in its upward position with the springs, A and , to 
 which the circuit wires are connected. When a train passes 
 over the rail, A is connected to B by the action of the lever, D. 
 
THE TRACK CIRCUIT 
 
 97 
 
 These contacts are in series with the device operated, and were 
 formerly in the signal-control circuit. 
 
 The track circuit which would be afforded by ordinary rails 
 is unreliable, owing to the poor electrical contact of the fish 
 plates and abutting rail ends. It is evident that a single open 
 contact such as that caused by the scale or oxide usually covering 
 rails, would suffice to break the electrical continuity of the track 
 circuit and render the signal system inoperative. Passing trains 
 and the consequent vibration serve to increase this unreliability. 
 For this reason, rail bonds are used to establish the electrical 
 connection of the adjacent rails. 
 
 ~-cast- iron housing 
 ror/A 
 
 FIG. 95 
 
 In Fig. 96 the method of applying bond wires to two butting 
 rail ends, A and B, is shown. The fish-plate, F } is bridged over or 
 shunted by two bond wires, C-C, which are usually No. 8 B.W.G. 
 galvanized E.B.B. iron, dependence not being placed on the 
 contact of the former. The connection is effected by channel 
 pins, D, one of which is shown at E, these being driven in a 
 -j^-inch hole drilled in the web of the rail, with one end of the 
 bond wire. The channel pin is recessed and tapered so that 
 when driven home it grips the wire with considerable force. 
 The wedge compresses tightly around the wire, thus producing 
 a large contact area, the hole in the pin before driving being 
 slightly larger than the diameter of the wire. The operation of 
 driving also cleans the pin, the wire, and the rail; thus affording 
 a good electrical contact, which is impervious to rain or dust. 
 A section of the rail and channel pin is given at G. 
 
98 
 
 AUTOMATIC BLOCK SIGNALS 
 
 Riveted bond wires are sometimes used, although the consen- 
 sus of opinion is that they are not so reliable as channel pins. 
 A riveted joint is illustrated at H in the above figure, a rivet 
 being shown at K, the latter being upset in a hole drilled in the 
 flange of the rail. No. 6 B. & S. copper wire is used at planked 
 highway crossings, tunnels, or other damp localities when rivets 
 are used. 
 
 In some cases bond wires are placed beneath the fish-plate ; in 
 others, outside the latter. The advantages of the first are the 
 protection afforded the wire from mischievous persons, who 
 often force the loose wire up on the face of the rail to be cut off 
 
 H 
 
 by a passing train; and also from the operations of the main- 
 tenance-of-way corps. The disadvantage is the ease of oxidiza- 
 tion, caused by the entrained moisture, and the labor of inspec- 
 tion. The second method has a reverse order of advantages and 
 disadvantages. 
 
 When a track relay fails to be energized, after a survey has 
 shown that the track battery is in proper condition, it is neces- 
 sary to inspect the bond wires on both rails of the entire section, 
 to locate the open circuit. With bond wires placed beneath the 
 fish-plates, this is a laborious process, since each bond must be 
 pulled to determine its continuity. With open bonds it is 
 merely necessary to glance at the wires to discover any break in 
 
THE TRACK CIRCUIT 
 
 99 
 
 the circuit, riding on the rear of a train giving ample time for 
 inspection. 
 
 The number of bond wires used at a joint is a matter of indi- 
 vidual opinion, but usually two are employed. With covered 
 bonds, the general practice is to use one, while at grade cross- 
 ings, bridges, and tunnels, three are used, to decrease the liability 
 of an open circuit, due to the vibration and moisture evident 
 under these conditions. Continued vibration results in crys- 
 tallization of the metal at the junction with the rail; and when 
 a break occurs, it is difficult to detect. 
 
 A representative installation at a switch or crossover is shown 
 in Fig. 97. The trunking, A, shown in section, carries the insu- 
 lated leads from the switch instrument, B, and the track connec- 
 
 FIG. 97 
 
 tions, E-C. When the switch is open, B short-circuits the 
 track, thus giving the block the same condition as that obtain- 
 ing when a train is in this section. The switch-point rail rides 
 upon two or more wedge blocks, F, that prevent it from coming 
 in contact with the rails at E, from which it must be insulated 
 when the switch is in its normal position, as the point rail is in 
 electrical connection with the rail at C, through the uninsulated 
 cross-bar, 7, and the remainder of the rail. An end elevation of 
 B is given at G. The short-circuiting action of the point rail 
 cannot be depended upon; otherwise the switch instrument 
 would not be used. This is an important consideration, as the 
 open switch must hold its home signal at danger. 
 
 The same object is obtained in a line-wire system by opening 
 the signal circuit when a switch is open. This is accomplished 
 
100 
 
 AUTOMATIC BLOCK SIGNALS 
 
 through the arrangement shown in Fig. 98. The wood, w, is of a 
 width conforming to the number of contact springs, n, used. One 
 of the latter is used for each of the circuits, and it makes and 
 
 breaks connection by its 
 end, a, with a stationary 
 contact piece, h. This is 
 effected by the small insu- 
 lated roller, /, which is 
 operated by the switch 
 movement through the 
 FlG 98 pivoted lever, m. When 
 
 the switch is closed, the 
 
 end, a, is in contact with h, and when open it is disengaged 
 from the latter, due to the removal of the roller from the hump 
 in the spring. One circuit wire is connected to n and the other 
 to h. On double-track lines, four contact springs, which are 
 in series with home east, home west, distant east, and distant 
 west, are often used. 
 
 Since cross-bars and switch rails would ordinarily short- 
 circuit the track, it is necessary that insulation be introduced in 
 these members to maintain the normal electrical isolation of 
 the rails, which are of opposite polarity. As the track voltage 
 is very low, the insulation re- 
 sistance need not be relatively 
 high, as is required in power 
 circuits. For this purpose 
 fiber is almost universally em- 
 ployed, due to its economical 
 initial cost and subsesquent 
 ability to withstand excessive 
 pressure and vibration. Sev- 
 eral schemes of switch con- 
 struction are in use which 
 eliminate the use of insulation 
 at these points. One very 
 meritorious arrangement was 
 Fig. 97. 
 
 In Fig. 99 a standard type of switch-rod insulation is shown. 
 The rod is divided into two parts, A and B, the adjacent ends 
 being secured mechanically by the bolts, C, and insulated by the 
 
 FIG. 99 
 
 described in connection with 
 
THE TRACK CIRCUIT ' 101 
 
 fiber bushings, E and strips, D. Adjacent rail ends in an insulated 
 track section are separated by fiber sheets of the same shape as 
 the rail section, as at G. The rails are held either by wood 
 splice bars, or the regular steel fish-plates are supplemented by 
 fiber sheets conforming to the rail sides. The bolts passing 
 through the rails are insulated by means of fiber bushings. 
 Where special reinforced fish-plates are used, a more substantial 
 disposition of the sheet fiber is effected. 
 
 In Fig. 100 an Atlas rail joint is shown in section. Such a 
 massive construction is required on the outer side of a curve 
 for any rail section, and is used on roads having heavy rails, 
 such as 90 or 100 pounds to the yard. 
 
 fibre insulation 
 
 FIG. 100 
 
 Properly designed insulated joints are of the utmost impor- 
 tance in maintaining the integrity of the track-circuit equip- 
 ment. Great trouble has been heretofore experienced with this 
 adjunct, but experience and time test have sifted out the forms 
 of joints that are fitted for this purpose. A good joint will have 
 great mechanical strength, stand excessive vibration and wear, 
 continue the proper alignment of the rails, have high insulation, 
 and be easily renewed. Turnouts, local freight lines, sidings, 
 and secondary tracks are sufficiently well insulated by wood 
 splice-bars; while main tracks should have joints reinforced by 
 steel plates. 
 
 In completing track or other circuits between a drawbridge 
 and the abutments, it is not often advisable to use a submarine 
 
102 AUTOMATIC BLOCK SIGNALS 
 
 cable, as the latter is not only too costly and undependable, 
 but it does not break the circuits when the bridge is open. 
 A circuit-breaking device, operated coincident with the move- 
 ment of the bridge is a desirable feature, and it should have 
 sufficient flexibility to prevent misalignment of the draw from 
 affecting it. A so-called bridge circuit-coupler, which is used 
 
 FIG. 101 
 
 FIG. 102 
 
 to preserve the continuity of such circuits, so that when the 
 bridge is open they will be opened, is shown in Fig. 101, and 
 consists of two boxes, B and E, containing the connecting arrange- 
 ments, either of which may be movable, one being fastened to 
 the bridge end, and the other to a cross-tie at the rail ends. A 
 is fastened to a lever of the bridge locking, and operates the 
 fingers, C, through the cross-bar, G, so that when the bridge is to 
 
THE TRACK CIRCUIT 
 
 103 
 
 be opened, the contact fingers, C, can be withdrawn from D, 
 thus breaking the respective circuits. Flexible cables, F, allow 
 a wide range of movement of C, the bridge circuits being 
 completed through the binding contacts, H. 
 
 One method of installing track cells and relays is shown in 
 Fig. 102. Within the cast iron chute, C (which is embedded in 
 the earth near the track to such a depth that only about one 
 foot of the top appears above ground), the three cells, /, held in 
 a wooden cage, H, are placed. This cage is raised and lowered 
 by the rope, G. The wires, K, leading from the cells pass to 
 the track by way of the trunking, F. Other wires, E, within the 
 hollow upright, B, pass from the relays, R, to the track. These 
 relays are placed upon the shelves, S, and in the design given 
 
 FIG. 103 
 
 FIG. 103 a 
 
 are of the polarized and neutral types. The number of wires, 
 M, will vary; in a double-track system there would be ten or 
 twelve, although eight only are shown in the figure, which is 
 for single-track. The number also varies accordingly as the 
 section is at a signal or not ; in the former case more wires being 
 used. For the batteryman's convenience and for protection, 
 a cover, D, provided with a lock, L, is added. The casing, A, 
 is of cast iron, and both water and insect proof. Sometimes the 
 track chute is separate, consisting of a simple cast-iron cylinder. 
 At K a connector, which is soldered to the leads at the cells, 
 is shown. The groove at the side is for the reception of the 
 soldered wire. 
 
 In Fig. 103 the relay and track connections at a cut section 
 on a normal clear, wireless, two-arm home and distant system 
 appear, the diagram of circuits being given at A. P is a polarized 
 
104 
 
 AUTOMATIC BLOCK SIGNALS 
 
 relay having two contacts in multiple on both polar and neutral 
 armatures. The track battery, B, has two components, the 
 greater ampere-hour capacity (of a given polarity) being con- 
 nected to the track during the normal operation, which is when 
 the semaphores are at clear. When a train occupies either sec- 
 tion C or E, section E will be short-circuited by the action of 
 the neutral armature contacts when the magnets are deener- 
 gized. When the distant blade at the preceding signal is at 
 caution, the ampere-hour capacity (at the opposite polarity) of 
 the connected track battery, B, is least, since this occurs only 
 when a train occupies the distant section. 
 
 In Fig 104 the track and other connections at a normally 
 clear wireless, with overlap, banjo-disk home signal, S, are 
 shown. R is a polarized relay, the distant signal being placed 
 
 FIG. 104 
 
 at a relayed cut section. Such a scheme of connection is also 
 used for a distant with a home in the rear, the latter having 
 a separate distant signal. An electromagnet energizes the disk 
 armature, this magnet having two windings, one of high resis- 
 tance, and the other of low resistance. The high-resistance coil 
 is connected in shunt with the contacts of the normally open 
 spring-switch, E. When the signal is at danger this shunt is 
 closed, thus short-circuiting the high-resistance coil and leaving 
 in circuit the low-resistance winding. This produces a high initial 
 current discharge, and consequent torque, when the front contacts 
 at the relay are closed, insuring the proper clearing of the ban- 
 ner. When once cleared, the latter can be held in this position 
 by the low energy of the high resistance winding. At the connec- 
 tion points, B is the free battery terminal, and C the common. 
 
CHAPTER VIII. 
 CONTROLLED MANUAL SYSTEMS. 
 
 IN the manual system of block signaling, the signals are 
 operated and controlled solely by the tower attendant, there 
 being no automatic control of the indicating functions. In the 
 controlled manual system, which is intended for long block sec- 
 tions, the movements of the signals are effected by the operator, 
 but these movements are controlled by electrical devices whose 
 sources of current are in various track and line circuits. 
 
 In its usual form, this latter system consists of a number of 
 electromagnets whose moving systems are so mechanically 
 connected to the levers they control, that movement of the 
 latter is prevented unless the block covered is in the proper 
 condition for such movement. This is effected by giving the 
 operator at one end of the block electrical control over the lever 
 movement at the other end. 
 
 Thus, if the operator at 17 allows the movement of a train to 
 18, and then throws his signal to the danger position, he cannot 
 throw the latter to clear until the operator at 18 unlocks his 
 lever (17's), which 18 will not do until the train has passed out 
 of the block, automatic arrangements preventing this unlocking, 
 even if it were attempted. These latter accomplish this object 
 by an electromagnet controlling the lever at 17, in series with 
 which is a battery at 18, the line wire of this circuit being 
 either broken at one of the various cut sections of the block, 
 or at the section of the next block at 18, which has a track- 
 relay back-contact in series with this battery, so that the 
 locking magnet is not demagnetized until a train enters this 
 section. 
 
 This latter arrangement is given in diagrammatic form in Fig. 
 105. Track relay 6, at section 18a, normally holds its armature 
 in the position shown. When a train, passing from 17 to 18, 
 arrives at 18a, by short-circuiting track battery c, Us armature 
 
 105 
 
106 
 
 AUTOMATIC BLOCK SIGNALS 
 
 closes the circuit of d, thus energizing a and releasing the locking 
 function, e. 
 
 Under the permissive system, however, this arrangement 
 would not give adequate protection, for, should a train be 
 allowed to pass 17 before the previous train has reached 18, then 
 when the latter arrives at 18 the locking function at 17 is released, 
 thus giving a clear signal to the next train entering front section 
 17-18. To prevent this confusion, a track relay and contacts 
 may be interposed in the latter section, thereby approaching 
 more closely to an automatic system. This would be disadvan- 
 tageous, however, in taking away, in this case, the requisite 
 control of conditions from the tower operator. 
 
 In the manual control system brought out by Coleman, a com- 
 bined track and wire circuit is used to control the movement of 
 
 
 d 
 
 iiiiiiii 
 
 
 f 
 
 
 
 @ 
 e 
 
 J7 
 
 18 
 
 
 
 ~~ 
 
 t 
 
 ^ 
 
 *7s o. i 
 
 FIG. 105 
 
 mechanical signals. This arrangement will now be outlined, 
 but not the actual mechanical construction of the devices used; 
 the relations of the circuits and functions to automatic circuits 
 being the principal object of this description. 
 
 In Figs. 106, 107, and 108 the arrangement of connections 
 and a diagrammatic representation of the functions of the appa- 
 ratus is shown. Fig. 106 gives the circuits at the first block 
 station considered; Fig. 107, at the second station; and Fig. 
 108, at the third station, the fourth and all subsequent stations 
 being entirely similar to the third in the arrangement of accesso- 
 ries and circuits. 
 
 In Fig. 106 signal arm 5, controlling the home block, is 
 operated by lever 1, which is pivoted at 2, through the inter- 
 position of the usual mechanical accessories, and also the electric 
 slot, 13. This slot prevents electrically the movement of the 
 
CONTROLLED MANUAL SYSTEMS 
 
 107 
 
 signal arm when unfavorable conditions exist, as will be shown 
 later. The locking arrangement consists partly of a sector 
 casting, 6, having a lug, 10, which is connected by a link to the 
 slotted section, 18, the latter being moved whenever the signal- 
 man, by squeezing the hand piece, 3, attempts to unlock the 
 lever and subsequently throw the latter. The movement of the 
 sector is governed by the electromagnet, 9, through the finger, 7, 
 and the links, 8, connected to its armature. 
 
 In addition to 9, there is a circuit-control electromagnet, 12, 
 and also the relay, 14, connected to the track. The arrangement 
 of accessories at station 2 is somewhat similar to the above, and 
 
 common 
 
 FIG. 106 
 
 contemplates in addition a sliding semaphore, 26, and a switch, 
 19. The connections of the electric slot at this signal are not 
 shown, as it should be remembered that these circuits are traced 
 out only so far as they affect the signal at station 1. 
 
 The electromagnet, 9, is connected in series with the line wires 
 and with one of the front contacts of the track relay, 14. The 
 line wires pass to the make and break arrangement 20, operated 
 indirectly by the switch lever at station 2, the battery, 21, being 
 in this circuit; hence 9 will not be energized unless the sector 
 block, 22, is in the normal or danger position, as shown. The 
 circuit of 9 will thus be broken at 20, and finger 7 will prevent 
 motion of the sector block, 6, thus effectually locking signal 5 in 
 the danger position. 
 
108 
 
 AUTOMATIC BLOCK SIGNALS 
 
 Hence, before 5 can be cleared, the operator is required to 
 summon the operator at station 2 to put his signal in the normal 
 or stop position. Thus the apparatus requires that the block 
 covered by 5 be closed at its outgoing end, thereby preventing 
 a train from receiving a single permission to pass through two 
 blocks. When a train is to pass from 1 to 2, all conditions being 
 favorable, the operator throws lever 1, and consequently signal 
 5, the train then passing this signal. This causes the track 
 battery 25 to be short-circuited, thus deenergizing relay 14, 
 thereby breaking the circuit of 9. This allows the finger, 7, to 
 drop, preventing motion of sector block 6, and consequent 
 
 Com mo ??> 
 
 FIG. 107 
 
 unlocking of the lever. Thus signal 5 cannot be thrown to the 
 clear position until the train has passed out of the block and 
 restored contact 16 to its normal position by removing the 
 short circuit from the battery. 
 
 Since the train cannot pass out of the block until the signal, 23, 
 has been cleared, it follows that when this occurs the circuit of 9 
 will be opened at 20; hence, before the signal, 5, at station 1 can 
 be again cleared, the train must pass out of the block of 23, and 
 23 must be thrown to the danger position. It is evident that a 
 careless operator might throw the signal at station 1 to the clear 
 position, and thus allow another train to enter the block before 
 the first had passed out of it. But this is prevented by the 
 
CONTROLLED MANUAL SYSTEMS 
 
 109 
 
 action of the electric slot, which throws the signal to the stop 
 position when a train has entered its block independently of the 
 operator. Thus the connection between the lever and the sema- 
 phore is not positive, but depends upon the electrical conditions 
 of the block. The circuit of this slot (which is operated by an 
 electromagnet) is composed of the wire, 4, the second front 
 contact of track relay 14, electromagnet 12, armature contact 
 27, battery 17, common line-wire, and wire 28. 
 
 FIG. 108 
 
 When a train enters the block of signal 5, track relay 14 is 
 short-circuited, thus breaking the slot magnet circuit at 15, and 
 simultaneously at 27. This causes 5 to pass to the danger posi- 
 tion, independent of the position of lever 1. The reason for 
 interposing the independent double break is to preclude the 
 possibility of the operator's throwing forward the lever to the 
 normal position as soon as the train has passed into the block 
 protected by 23, as this latter position of the train will restore 
 the break in the circuit at 15 by the action of 14. Thus the 
 connection between the lever and its semaphore is effectually 
 broken until the proper conditions obtain. The consent of the 
 
110 AUTOMATIC BLOCK SIGNALS 
 
 operator at 2 to allow movement of the signal lever at 1 is usually 
 given by an electric bell or telegraph code. 
 
 It is evident that the circuit cannot be closed at 27 except 
 by a current passing through the circuit independent of its 
 own armature and contact. This latter circuit is formed by the 
 wire, 4, passing from the slot magnet of 13, and includes also 
 make-and-break arrangement 15, magnet coils 12, make-and- 
 break mechanism 11, battery 17, common line-wire, and wire 
 28. Since 11 is controlled by sector block 6, and the links, 
 10, attached to 18, when the lever, 1, has been thrown to its nor- 
 mal or stop position, the circuit is closed at this point, it being 
 open when 5 is in the clear position. 
 
 The motion of the hand piece, 3, which is necessary in order 
 that the lever may be unlocked preparatory to its movement, 
 produces motion in the slotted casting, 18, which indirectly 
 breaks the circuit at 11, providing the sector block, 6, does not 
 meet with the free end of the finger, 7. The closing of the cir- 
 cuit at 11 causes a current to pass through the coils of 12, 
 thereby closing the circuit of slot 13 at 27. This becomes 
 necessary in order that the slot mechanism may be held locked 
 when lever 1 is to be moved. Otherwise the signal could not 
 be cleared, since the mechanical connection is through the 
 interposition of the slot. As 27 is in shunt with 11, the circuit 
 is not broken by the opening of 11, so that the current from 17 
 continues to pass around the coils of 12. 
 
 As already stated, this system is applied to block sections of 
 great length, so that if a continuous rail circuit were used, it 
 would become needlessly expensive and complicated. As this 
 combination of wire and track circuits is more readily compre- 
 hended, and simplifies what will follow, the above description 
 has included it. In the circuits given with those at station 3, 
 the track circuit will be omitted, except for a short working or 
 setting length at each signal. 
 
 It has been shown that when a train passes signal 23 the con- 
 trol of 5 is restored to the operator at station 1, provided the 
 operator at 2 has put his lever in the normal position. At sta- 
 tion 3, on the other hand, 23 cannot be unlocked at once by the 
 passing train, only the plunger, 58, being released. This latter 
 must be actuated by the operator before the train passing signal 
 23 can short-circuit the track relay and produce an automatic 
 
CONTROLLED MANUAL SYSTEMS 111 
 
 set of conditions at station 2. The operator at station 3 must 
 actuate the plunger, 58, at the request of the operator at station 
 2, so that the latter may give a clear signal to the next train to 
 occupy the block. In addition, the former must throw his sig- 
 nal to danger. 
 
 Since a train cannot pass 34 until 23 is cleared, and since 23 
 has been placed in the danger position to allow of 5's being 
 unlocked, it cannot be thrown to the clear position without the 
 permission of the operator at station 3. The apparatus by 
 which this permission is given constitutes Coleman's machine, 
 the mechanical construction of which will not be taken up. 
 
 Again considering the arrangement at station 3, it is evident 
 that lever 35 cannot be thrown until the sector block, 36, can 
 clear 37; that is, until a current passes through the electro- 
 magnet, 38. The floor knob, 39, is then pressed downward, 
 which closes the contacts at 40 and connects one side of 38 with 
 the common line-wire. When this occurs, we may trace up the 
 circuit to the closed contacts at 41 and the open contacts at 42. 
 These latter must be closed by energizing the electromagnet, 43, 
 before the circuit can be completed through the battery, 64, and 
 the common line return. As 43 is in shunt with the binding 
 posts, 44 and 45, a current must come in over the line wires from 
 station 2, and on the common line side through the armature 
 contacts of relay 52. Hence, it is necessary that 52 be in an 
 energized condition, that is, with no train on the section of track- 
 battery 53. At station 2, 20 must be closed, then a current from 
 21 will flow through 43. With these conditions fulfilled, 51 can 
 be cleared by throwing 35. 
 
 As above stated, 58 is a plunger which is moved in the direc- 
 tion of the arrow, normally held in the extreme inner position by 
 a spring, 70, this plunger being provided for the purpose of allow- 
 ing the signal at the next station to be unlocked. When 58 is 
 pulled out to the position shown, the projection on the dog, 57, 
 drops within the aperture, 71, in 58, thus breaking the contact of 
 spring 55 with 54, and connecting 56 with 54. The spring con- 
 tacts, 59, are closed, at the same time those at 41 being opened. 
 The former is effected by the action of the rock shaft carrying 
 the dog, 57, and the latter by the movement of a train. 
 
 The resistance coil, 69, is interposed in the circuit of 61, while 
 61 is an electromagnet which has an armature provided with a 
 
112 AUTOMATIC BLOCK SIGNALS 
 
 swinging carrier, 62. When 60 is energized, its armature, 63, 
 which carries a retaining catch, closes the contacts, 68, thus 
 connecting 48 with 49. When 37 is raised by 38, the contacts of 
 65 are opened, thus disconnecting 47 from 64. When the train 
 passes, 52 is energized, and its armature closes the lower contact, 
 the operator returning the lever to its normal position. This 
 opens the retaining circuit at 66, and in consequence, electro- 
 magnet 60, releasing the catch 63, allowing the word " Free " 
 on a banner to pass before a glass aperture in the housing, which 
 denotes that the lever at station 2 may be unlocked for a second 
 train. Thus the dependence of one operator upon the other is 
 shown. By tracing up the circuits, the reader will be able to 
 deduce the remainder of the functions. A complete description 
 of the apparatus would be too lengthy for this book. 
 
 On single-track lines, a modified form of lock and block arrange- 
 ment must be used if the controlled manual system is employed. 
 Trains bound in both directions must run alternately into sidings 
 to allow passing, these sidings being governed by signals which 
 are interconnected electrically. Block towers are placed as 
 near as convenient to overlapping opposite sidings, into which 
 trains proceed under given conditions. The operator at block 
 tower 23, for example, governs the levers at 24, this consecutive 
 arrangement being necessary for safety. It is evident, also, 
 that each operator has control over trains moving in both 
 directions. 
 
 In Fig. 109 the relation of such a single-track system, with 
 the Leonard scheme of control, is shown. D is a track instru- 
 ment (a device which closes a circuit when the wheels of a train 
 pass over the end of a projecting lever whose other end operates 
 a spring contact, as in Fig. 95) which closes the circuit of the 
 battery, F, through the lock instrument, E. In this same circuit 
 is a circuit breaker, G, which disconnects E from F. A circuit 
 closer, A, is situated at the ends of the east- and west-bound 
 sidings, and is connected to E and F by the line wires, K, L. 
 (The west-bound apparatus is distinguished by small letters.) 
 
 The operator, to allow an east-bound train to proceed from 
 23, unlocks the signal lever at the latter point. The unlocking 
 current passes over the line wires w, which connect successive 
 towers. This function then remains locked until released by 
 the track instrument, due to the effect of the passing train. 
 
CONTROLLED MANUAL SYSTEMS 
 
 113 
 
 The line circuit at the same time is opened (by the circuit 
 breaker, G, of the signal C), so that a west-bound train cannot 
 enter the section, because the west-bound signal, B, is at danger, 
 it being controlled by the battery at 23. If the locking function 
 is not released by D y the train enters the side track, and the 
 switch, S, must be closed by the brakeman immediately after 
 the train passes the derailing switch, which is at A. This 
 operation closes for an instant the unlocking circuit at A, 
 which sends a current to the lock instrument from the battery, F. 
 If a west-bound train is to be allowed to proceed, permis- 
 sion and unlocking is first received from 25. The signal, C, is 
 then cleared, which breaks the circuit of the track instrument 
 
 "3 ^x.^ 
 
 S. n ni 
 
 . fan jSTX* r s 
 
 K 
 
 L 
 
 *LJ _j 
 
 XiiJ ^ 
 
 k w ^S\ Jf 
 
 ^^Twest b'ound C- ^>T 1 
 
 S sid i 
 
 "3 t oJ 1 
 a 
 
 k A 
 
 
 ^jH 
 
 ^ 7 
 
 
 _ ^ N^ 
 
 W Tower 2V W 
 FIG. 109 
 
 and prevents the signal from being unlocked by a train until 
 it has first been thrown to the stop position. Indicators are 
 used at the switches to apprise the conductor as to whether 
 he may proceed on the main line or take a siding. 
 
 The electric slot is a controlling device which automatically 
 causes a mechanical semaphore to move to the danger position 
 after a train has passed this signal. This arrangement pre- 
 vents negligence on the part of the signal operator causing a 
 rear end collision. Its function is thus similar to the rod slot 
 which has been in use for many years on purely mechanical 
 systems. Fig. 110 represents the application of a Union electric 
 slot to a triple-lens mechanical signal. The semaphore, S, is 
 secured to a pivoted casting carrying three lenses, L, night 
 
114 
 
 AUTOMATIC BLOCK SIGNALS 
 
 indications being given by the lamp, A, the white light from 
 which must pass through a lens when the signal is in a full or 
 partial stop position. 
 
 This blade is operated by the rod, C, which passes into the 
 slot box, D, and is connected mechanically (when a train is 
 not in the block of the signal) with the rod, C. The latter 
 
 -u 
 
 FIG. Ill 
 
 is pivoted to a rocking lever counterweighted at F, which is 
 connected to the signal lever by the steel wires, G. E is a circuit 
 controller connected to the slot or control circuit of other signals, 
 as will be shown later. 
 
 The slot structure and its weatherproof housing is shown in 
 part section and part elevation in Fig. Ill; 1 being a side and 
 2 a front view. When motion is imparted to the rod, H, by 
 
CONTROLLED MANUAL SYSTEMS 115 
 
 the signalman, the frame, F, and the accessories attached to it 
 move. The rods, R and H, are not connected unless the electro- 
 magnet, M, is energized, when the signalman has full control 
 of the semaphore. On the other hand, if M be deenergized, 
 the connection between R and H is broken and movements 
 of the latter will in no wise affect the former, hence the blade 
 cannot be moved. 
 
 To the frame, F, the electromagnet, M, spring S, pivots P, 
 and guide sleeve, F, are secured. The link, /, moves around 
 the upper pivot as a center, while the spring piece, A, by pressing 
 against the projection, B, holds 7 in the position given. The 
 roller, W, which is attached to 7, engages in a recess with the 
 pawl, Q, the latter being pivoted in a recess on the rod, 72, at T. 
 When current is not passing through M, the centers of T, W, 
 and p are not in the same straight line. Therefore, if a pressure 
 be applied upward on H (which will occur when the signalman 
 attempts to clear the signal), the roller will move to the left by 
 the action of the link, 7, on its pivot. Hence this roller disen- 
 gages with the pawl (which cannot move further to the left) due 
 to the weight of the unbalanced semaphore; and 77 moves up or 
 down without engagement. The electromagnet has a movable 
 armature, which is held at one end by the stationary pivot, K, 
 and at the other end by a movable pivot, N. is a short link 
 secured rigidly to the lever, a, these being pivoted at P. The 
 armature is normally held upward, and away from the pole 
 tips by the spring, L. The pivots, K, N, and P, are normally 
 out of line, hence, when an attempt is made to force W upward, 
 a allows Q to be disengaged, thereby preventing motion of R. 
 
 If M be energized, due to the block protected by the signal 
 being clear, the tension of L will be overcome and the armature 
 will be in its extreme lower position. This forces the roller into 
 the recess in Q, and if movement be imparted to H, Q will also 
 move, and consequently R. If this motion were too rapid, 
 due to too energetic motion of the signal lever, it is evident 
 that the inertia of the parts would in all probability break some 
 part of the mechanism. To prevent this occurrence, a damping 
 cylinder or dashpot is interposed. It consists of a shell, D, 
 having a carefully fitted plunger, P, the latter being stationary, 
 and pivot ally secured to the bolt, V. The shell is fastened to 
 the coupling, U, connected to the semaphore rod, and has an 
 
116 
 
 AUTOMATIC BLOCK SIGNALS 
 
 extension, Z, which is slotted and forms a guide with the bolt, 
 V. An adjustable valve, X, through which the entrained air 
 (on the downward motion) bleeds out with more or less rapidity, 
 according to the retardation desired, is provided; and a shell, E, 
 forms a protection from the weather. The case, C, is bolted to 
 the signal mast by the lug, G. 
 
 When R is moved upward, the entire frame and its appurte- 
 nances, such as the magnet and pawl, also move. The spring, A, 
 only presses upon B at the commencement of the motion, so 
 that in case M were demagnetized by the presence of a train in 
 the block or an opened switch, when the signal was at clear, its 
 armature would rise, and the pawl be released, thus causing the 
 signal to assume the danger position independent of the operator. 
 The latter then replaces his lever upon receiving the indica- 
 tion by the action of the circuit controller. If the signalman 
 attempted to throw the signal to the clear position, he could not 
 succeed, since H has no connection with R. However, H, M, 
 F, and the roller will move upward, but this does not affect the 
 semaphore's position. The electric slot and its modification 
 
 occupies an important position 
 in composite manual and auto- 
 matic signaling, and is employed 
 extensively on signals governed 
 from centralized towers. 
 
 The method of applying circuit 
 controllers to the levers of the 
 controlled manual and semi-auto- 
 matic systems is shown in Fig. 
 112. The lever, Af, pivoted at 
 H, has two extensions, F and 
 G, to which the wires or bars 
 operating the signal are secured. 
 In order to unlock this lever, the 
 latch must be opened by moving 
 the pivoted member, L, in the 
 direction of the small arrow. 
 N is an electric lock or slot, 
 connected by a link to one of the rock shafts of the interlock- 
 ing machine, 7. This rock shaft is also linked to the unlocking 
 segment of the lever by the rod, E. 
 
 ~L 
 
 D' 
 
CONTROLLED MANUAL SYSTEMS 
 
 117 
 
 G and D are circuit controllers operated respectively by the 
 toes, and M. B-K is a floor button which closes a circuit 
 connected to the distant cabin, and serves as a means of com- 
 munication and releasing between the operators. The functions 
 and operation of this arrangement will be apparent from de- 
 scriptions already given. 
 
 One application of a duplex rotary circuit-controller, E, is 
 shown in Fig. 113, it being fastened to the signal pole and 
 operated through the home semaphore by the rod or connecting 
 link, M. 7 is a mechanically operated home and distant, the 
 electric slots, A and C, securing the semi-automatic control, and 
 being energized by battery D through the interposition of the 
 
 FIG. 113 
 
 polarized relay, G. A is controlled by the neutral armature, F, 
 and C by both the polarized, N, and neutral armatures in series. 
 The controller, B, is in series with the home slot, and by being 
 open when the semaphore is not at clear, effects a saving in 
 current consumption, besides giving an additional manual con- 
 trol if desirable. 
 
 When the home blade is at stop, contact B is open, hence C is 
 deenergized, so that the distant cannot be cleared unless the 
 former is clear; a similar condition existing when either F or N 
 is open, which will occur if T is short-circuited or of the wrong 
 polarity. Contacts a and b effect a polarity reversal of the 
 track battery, /, by motion of M . This polarity change occurs 
 at every motion of the home blade, thus controlling the preced- 
 ing signal. The fourth contact of the controller is unconnected, 
 
118 
 
 AUTOMATIC BLOCK SIGNALS 
 
 the construction allowing a nearly complete stroke of M before 
 a change in connection takes place. 
 
 A circuit controller for operation by the foot is shown in sec- 
 tion and elevation in Fig. 114. To the floor or other convenient 
 
 support, B, the pivoted lever or 
 foot piece, A, is secured. The 
 opposite end of this foot piece 
 carries a roller, H, which presses 
 against a curved spring strip, G. 
 Normally, G is in contact with 
 F, or E is connected to D. 
 When A As forced downward, 
 E is connected to C, and D is 
 
 open-circuited. This device is applied wherever it is desired to 
 close one circuit simultaneously with the opening of a normally 
 closed circuit. 
 
 FIG. 114 
 
CHAPTER IX. 
 MOTORS, RELAYS, ETC. 
 
 SIGNAL motors are of small size, series wound, and for direct 
 current only. As they are generally operated by battery cur- 
 rent, the terminal voltage is of necessity low. It is not prac- 
 ticable to operate motors over line wires of any great length, 
 owing to the great loss of energy in the latter, and the low 
 starting torque of the motor. 
 
 The sizes of motors used vary from 65 to 150 watts, or one- 
 twelfth to one-fifth of a horse-power. From 10 to 20 Edison 
 or Gordon cells are used to operate these motors, so that, should 
 the applied voltage vary from 7 to 14, the full-load current 
 will vary from 9 to 5 amperes in the smallest motors to from 
 20 to 11 amperes in the one-fifth horse-power unit. The larger 
 motors (as in all-electric systems of interlocking) are supplied 
 with current from a storage battery having considerable poten- 
 tial, so that the above currents are much reduced. Derailing 
 and switch movement motors are at a maximum of about one 
 horse-power, although they operate normally at about 420 
 watts (7 amperes at 60 volts, or 4 amperes at 110 volts). 
 
 In Fig. 115 a standard form of signal motor is illustrated. 
 F is the laminated field, which consists of a large number of 
 stampings of soft iron held firmly between heavy end pieces of 
 similar contour. The exciting coils, W, are connected in series 
 with the armature, A, through the brushes B, and the commu- 
 tator, C. S is a removable transparent glass end-shield, which 
 effectually prevents dust and moisture from collecting on the 
 moving surfaces, also allowing inspection from time to time. 
 P is the brake pulley and M the brake mechanism, whose func- 
 tion is described in connection with Fig. 117. 
 
 The laminations of soft iron on both armature and field, 
 having a high permeability, allow of a greater flux density 
 than could be obtained from solid iron, at the same time reduc- 
 
 119 
 
120 
 
 AUTOMATIC BLOCK SIGNALS 
 
 ing to a minimum the eddy-current loss. The armature shaft 
 carries a pinion which engages with the gear train of the clearing 
 mechanism. The motor is provided with a base by means of 
 which it is bolted to the frame. Semaphore signals in general 
 use motors that have become the standard for small sizes in 
 electrical power application, with but slight modification. 
 
 There are a number of combined electrical and mechanical 
 methods of applying a brake to a motor armature for the 
 purpose of rapidly bringing it to rest; so that the semaphore 
 movement will occur within a minimum time and at a uniform 
 
 FIG. 115 
 
 rate throughout the entire angle of motion. Obviously the 
 most effective arrangement will operate immediately upon cur- 
 rent cessation, and release upon the commencement of its flow. 
 Two such schemes will now be considered. 
 
 In Fig. 116, a is a friction wheel keyed to the shaft, i, of the 
 motor. In series or shunt with the motor or its field is an 
 electromagnet, g, whose armature, /, pivoted at d, and weighted 
 at e, carries a shoe or brake, 6, pivoted at c, and conforming on 
 its inside surface to the circumference of a. When the current 
 passing through g (and consequently the motor) ceases, b will 
 engage with a and bring the latter to a stop within a time 
 
MOTORS, RELAYS, ETC. 
 
 121 
 
 proportional to the relative position of c. The disadvantage 
 of this device is the multiplicity of parts and the waste of 
 energy in exciting g. 
 
 In Fig. 117, which is a brake frequently applied to sema- 
 phore motors, F is the field pole of the motor, S the armature 
 shaft, and P a pulley keyed to the latter. B is a rubber held 
 normally against the face of P, by the adjustable spring, H. 
 B is carried on the iron rocking pieces, and its position deter- 
 mined by the adjustment, G. When current passes through the 
 motor, the iron prong or strip is attracted to the tips of F, and 
 by overcoming the tension of H releases B. When current 
 
 G 
 
 FIG. 116 
 
 FIG. 117 
 
 ceases, the cessation of the flux in F releases the prong, caus- 
 ing B to be forced against P, and rapidly overcoming the 
 inertia of the armature. 
 
 Soft iron disks affixed to the armature shaft have also been 
 used to retard the rotation of the latter. The disk moves 
 between the poles of a strong electromagnet, and the reaction 
 caused by the setting up of eddy currents in this disk effec- 
 tually brings, the armature to a stop. 
 
 A motor brake and the circuit arrangement thereto is shown 
 in Fig. 118. A is the signal-control relay (normal danger) in 
 series with the main battery, common, home line-wire, and 
 track-relay armature. It has front and back armature con- 
 tacts, C and B, having a common connection. B is in series 
 
122 
 
 AUTOMATIC BLOCK SIGNALS 
 
 with the motor, so that the latter is short-circuited upon itself. 
 H is a circuit controller whose movable contact, E, travels in 
 the direction of the arrow when the signal is clearing. When 
 A, is energized, a current passes from D to G, H t motor, and (7. 
 When the semaphore is about cleared, E connects G and /, 
 thus sending a current through the brake magnet, J, and bring- 
 ing the motor armature to a stop, current being cut off simul- 
 taneously from the motor circuit. When the semaphore 
 returns to danger by the deenergization of its slot and A, the 
 current set up by the counter e.m.f . through the low resistance 
 circuit, H-E-F-B, produces the desired retardation. 
 
 For a given output, the resistance of motors increases as 
 the voltage of the circuits to which they are applied is increased. 
 
 lines 
 
 FIG. 118 
 
 In small motors, the higher the average voltage at which they 
 operate, the more efficient do they become. It is not so much 
 the actual resistance of the motor itself which gives the increased 
 efficiency, but the relativity of this resistance to the total 
 resistance, external to the motor terminals, such as that in 
 the wiring, relay contacts, batteries, and connections. Hence, 
 the greater the operating voltage, the less will be the percentage 
 of loss in these subsidiary devices, and the greater the available 
 energy manifested in motor torque. 
 
 A transmission gear for throwing one or more semaphores to 
 clear is outlined in Fig. 119. The motor, M, drives the sheave, 
 S, through the gearing, G. B is a brake magnet whose arma- 
 ture lever when deenergized bears against the wheel, W, keyed 
 to the armature shaft, thus preventing rotation of the lat- 
 ter, the adjustable counterweight, (7, providing a time limit. 
 
MOTORS, RELAYS, ETC. 
 
 123 
 
 This arrangement is fastened near the base of the signal pole 
 and provided with a weatherproof cover. 
 
 Numerous types of relays are used in signal practice, all of 
 which embody certain generic features. Great variations exist, 
 however, in the resistance to which they are wound, in one case 
 a four-ohm winding being standard, and in another a 3000-ohm 
 winding is applied. 
 
 M 
 
 w 
 
 FIG. 119 
 
 FIG. 119o 
 
 In Fig. 120 a Taylor neutral-track or control relay is shown. 
 The magnets, M, are carried on the cast brass base, between which 
 and the sub-base are the armature 
 and contacts, the latter being pro- 
 tected by a cylindrical glass ring, G. 
 The contact fingers, H, are fastened 
 to the armature, A, by lavite bush- 
 ings, L, and make scraping connec- 
 tion with the front contact, F, and 
 back contacts, B ; these being intro- 
 duced in the external circuit by the 
 binding posts, C. The coils of M 
 are connected to posts, P. 
 
 Fig. 121 shows in section and 
 elevation a polarized type glass- 
 enclosed relay having a neutral arma- 
 ture, C, and a polarized armature, G. The latter swings about a 
 pivot, B, the direction of motion depending upon the polarity 
 of the poles of magnets, M. A is a permanently magnetized 
 rod of steel, one end of which is fastened in the yoke, H, the 
 
 FIG. 120 
 
124 
 
 AUTOMATIC BLOCK SIGNALS 
 
 other projecting to the level of the pole tips of M. The neutral 
 armature is given a vertical movement, and has front carbon 
 contacts at D and back contacts at E, through the flexible 
 strip, F. 
 
 The operation will be evident from the plan of the contact 
 parts in Fig. 122. When current in either direction passes 
 through the magnets, the neutral armature, G, is raised, closing 
 the front contacts, D. On cessation of current, the back con- 
 tact only is closed. If the pole tip on the right hand side be of 
 north polarity, and the same end of the polarized armature, G, 
 
 H 
 
 be magnetized inductively from the permanent magnet so 
 that it becomes a south pole, attraction will result and the 
 armature will turn in this direction. The opposite end of the 
 armature will be repelled from the other magnet pole, as the lat- 
 ter is of south polarity, the armature end also being south. 
 This causes the contact fingers, L, to be forced against the 
 carbon contact-buttons, K. A reversal of current will reverse 
 these conditions. 
 
 Both armatures are pivoted close to the field poles, so that 
 the required motion is slight, hence they are continually in a 
 strong field when energization occurs, due allowance being 
 
MOTORS, RELAYS, ETC. 
 
 125 
 
 made for eliminating the effects of residual magnetism. Adjust- 
 ment is not required, as the pivots are fastened to the pole 
 tips, overcoming the variations due to expansion. The alter- 
 nate polar contacts are in multiple, and contact made with a 
 scraping motion, for self-cleaning. With a short armature 
 motion, a wide break results, flexible copper strips connecting 
 the binding posts of the armature fingers. 
 
 --K. 
 
 j FIG. 122 
 
 Fig. 123 shows a relay designed for breaking circuits carry- 
 ing heavy current at comparatively high potential (for signal 
 circuits). The magnet coils, M, are 
 connected to the track, or other control 
 circuit; the working current being car- 
 ried by the resilient strip, E, and carbon 
 contacts, C. When the armature falls, 
 a wide and rapid break is introduced, 
 the back contact at D being then closed. 
 B is a series magnetic blow-out coil, 
 the poles of its magnetic circuit caus- 
 ing a powerful flux to pass across the 
 arc, thus rapidly disrupting it ; a slight 
 movement of the armature, F, also 
 produces a wide break at C. The 
 mechanism is enclosed in a glass case, 
 as the presence of dust or insects is inimical to its proper 
 operation. 
 
 FIG. 123 
 
126 AUTOMATIC BLOCK SIGNALS 
 
 The G. E. neutral relay, with the glass cover removed, is 
 shown in Fig. 124. M are the electromagnets, which actuate 
 the armature, A. The latter carries brass lugs to which the 
 carbon contacts C, are clamped, these making and breaking 
 contact with the flexibly mounted fingers, F, carrying ends Of 
 silver. The posts, P, are in connection with the terminals, D-D. 
 A quadruple break is effected by this device, which is very 
 satisfactory. The contacts cannot be fused by lightning, 
 as carbon and a metal will not fuse together in such cases. 
 
 FIG. 124 
 
 The advantage of using carbon is that its oxide is a gas; thus 
 it continually presents a clean surface, while the oxide of silver 
 itself is a good conductor. 
 
 In order to eliminate the false conditions set up from relay 
 contacts being fused together by lightning, the relay armature 
 arrangement shown in Fig. 125 is used. The armature, H, 
 of the electromagnet, M, having pole tips, P, is pivoted at F, 
 and carries a depending member, K, at the pivot, G. Fastened 
 to K is the spring contact strip, B-E, which normally is in 
 contact with the connection A. When B, however, becomes 
 fused to the contact button, C, this latter point acts as the 
 
MOTORS, RELAYS, ETC. 127 
 
 pivot, so that when M is demagnetized the weight of H and 
 
 K causes J to come into contact with D. The signal magnet 
 
 relay or battery is connected to D and C, so that when E comes 
 
 into contact with D, it will be 
 
 short-circuited, as this shunt 
 
 has practically no resistance. 
 
 This causes the signal arm to 
 
 move to the stop position, 
 
 thereby apprising the main- 
 
 tainer that something is 
 
 wrong. Otherwise, the pres- 
 
 ence of a train in the section 
 
 would not affect the clear FIG 125 
 
 position of the signal, since 
 
 the release of the armature cannot open the circuit at C-B. 
 
 Great care should be exercised in selecting the proper resist- 
 ance value to which relays are to be wound, as upon this 
 factor depends in a large measure the life of the batteries to 
 which they are connected. Thus a 700-ohm relay will take 
 but one-tenth of the current that one wound to 70 ohms would. 
 Too high a resistance is not advisable, as the wire then must 
 be of very small diameter, so that the proper number of ampere- 
 turns can be put into the necessarily limited space between 
 the cores. Fine wire is very costly and difficult to wind, while 
 the slightest corrosion or mechanical injury results in an open 
 circuit. Too large a size or wire, on the other hand, involves 
 too great a current input for the production of the proper 
 ampere-turns. 
 
 Individual cases require special determination of resistance; 
 so that no fixed rule can be followed. It is sometimes advis- 
 able to introduce a German silver resistance spool, having a 
 predetermined ohmic factor, in series with a relay connected 
 to a battery of too high voltage, which is primarily intended 
 for other purposes. Such a procedure should be avoided 
 whenever possible, however, as the energy thus lost in the 
 resistance is wasted. Relays in series must have resistances 
 proportional to the work which they perform. For instance, 
 a relay in series with a disk magnet must have a low resistance 
 relative to that of the latter, otherwise too great a proportion 
 of the available energy would be taken. Relays in parallel 
 
128 
 
 AUTOMATIC BLOCK SIGNALS 
 
 must have high resistance so that the changed drop in poten- 
 tial resulting on one or more being thrown in circuit cannot 
 materially affect the others. 
 
 Fig. 126 is a plotted curve showing the voltages required 
 to operate standard track -relays of from 2 to 10 ohms resistance. 
 Curve V shows the least voltage that should be applied to a 
 given relay of a certain resistance in practice. This curve 
 allows for operation under favorable conditions; with allowance 
 
 .6 
 .5 
 
 I" 
 
 *-J 
 
 M 
 
 ^ 3 5 d ^ a 
 
 Resistance in ohms 
 
 FIG. 126 
 
 9 10 
 
 for an average amount of leakage, due to the effects of wet 
 weather, and rail proximity to stone ballast. 
 
 The curve, M, shows the minimum voltage that will lift the 
 armature of the relay and produce contact with the fingers. 
 This voltage curve allows only for a moderate amount of 
 resistance of motion due to friction of the pivots, and will not 
 lift the armature with cobwebs, interference by insects, or 
 other deleterious opposition. On the other hand, the presence 
 of residual magnetism will require a lower voltage for ener- 
 gizing the magnetic circuit; this, however, being an undesirable 
 condition. 
 
MOTORS, RELAYS, ETC. 129 
 
 There is a sufficient interim of current cessation at the reversal 
 of polarity in a wireless system to throw the signal at danger 
 unless a slow releasing of the control armatures or slots be 
 provided for. The slow-releasing slot is obviously the best 
 solution of this difficulty, as external control fixtures are then 
 not required. The home-slot magnets are therefore constructed 
 with a soft copper tube interposed between the core and the 
 winding, and equal in length to the core. Any change of current 
 in the latter sets up strong momentary eddy currents in the 
 tube, which oppose any change in flux through the magnetic 
 circuit. The magnet is also wound to sufficient ampere-turns 
 to produce a much greater flux than is actually required, so 
 
 FIG. 127 
 
 this flux must die down a considerable amount before the 
 armature is released. Should the circuit remain open after 
 the mechanical pull of the armature becomes less than the 
 opposition of gravity or the slot arm, the home semaphore 
 will return to danger. 
 
 Important adjuncts in a line-wire system are devices to 
 secure adequate lightning protection. They are particularly 
 required to prevent relay points from fusing together by afford- 
 ing the discharge a shunt circuit to ground of lower impedance 
 than by way of the former. A lightning or other static dis- 
 charge is in reality a surging alternating current of enormous 
 frequency and short duration. Such a discharge will overcome 
 the high resistance of an air-gap rather than pass around a few 
 
130 
 
 AUTOMATIC BLOCK SIGNALS 
 
 turns of coiled conductor, as the latter, at this frequency, 
 offers an extremely high inductance. 
 
 A bank of four G. E. lightning arresters is shown in Fig. 
 127. The lines are connected to the posts, A, the instruments 
 to the connectors, B, and ground to the plate, G. The choke 
 coils, K, consisting of a few turns of heavy wire in an insulating 
 form, are in series with the glass tube enclosed fuses, F, these 
 latter being removable, and held between clips C. A discharge 
 will pass from the points beneath the slate end pieces to the 
 ground plate rather than around the coil. Jumping areas 
 also occur between the lower parts of the convolutions and G, 
 thereby increasing the factor of safety. 
 
 Another common form of arrester is illustrated in Fig. 128. 
 
 FIG. 128 
 
 Upon a porcelain form are wound two connected helices 
 of bare wire, D, one end of which is connected to post A, and 
 the other end to C. B is grounded, A connected to the line 
 or track wire, and C to the instrument or wire desired to be 
 protected. When a discharge enters at A, D offers such a 
 high impedance that the air-gap between E and D is bridged 
 before many turns have carried the current, thus conveying 
 it to the ground. When a bank of such arresters is employed 
 the ground plates are connected by the strips, F, but one ground 
 wire being used. No provision is necessary to prevent ground- 
 ing of the battery currents, since they are of too low potential 
 to bridge this gap, as would be the case on a commercial light- 
 ing or power circuit. 
 
CHAPTER X. 
 HALL APPARATUS. 
 
 THE enclosed disk signal has a number of meritorious features, 
 among which are the protection of the moving parts against 
 the weather, and the low energy required to operate the moving 
 system. An electromagnet of comparatively 
 small size operates the latter, the power 
 required being insignificant (about 2.5 watts 
 in ordinary cases). The external appearance 
 of a post-type normal danger home and 
 distant disk-signal, such as is used on the 
 Lehigh Valley, is given in Fig. 129. A is the 
 home banner, which consists of a red silk, 
 cotton, or aluminum disk stretched on a ring 
 having a diameter of about 18 inches; while 
 B is the distant banner, which is of a green 
 fabric. The inside back of the housing, C, is 
 painted white, so that when the disks are in 
 the upper position, the aperture in the case 
 will show white. The case is usually painted 
 black, so that the color of the opening may 
 be seen for a considerable distance. 
 
 Lamps L are placed in the rear of the 
 apertures, D and E, before which spectacles 
 
 of the same color as the disks pass, for night 
 signaling. The tendency of gravity is to hold the disks in a 
 position directly behind the glass-covered apertures, so that 
 unless the magnets are energized, a color indication will be 
 given to the engineer. Disk signals are purely color arrange- 
 ments, in contradistinction to semaphore, or position and color 
 signals. Where home or distant units on separate masts are 
 used, the banjo is placed on top of, and centrally disposed with 
 respect to the pole, which produces a more symmetrical combi- 
 nation. 
 
 131 
 
132 
 
 AUTOMATIC BLOCK SIGNALS 
 
 Among the disadvantages of enclosed signals may be men- 
 tioned: the tendency of sleet or snow to obscure the disk, by 
 covering the glass and thus giving a white effect ; the direct reflec- 
 tion of the sun's rays in the engineman's eyes, preventing a clear 
 view of the disk ; and the liability of the glass spectacles falling 
 out, due to their tendency to crack from the effects of the inertia 
 of the moving system. Only the latter may be regarded as a 
 dangerous feature, since all railroads require that a train stop 
 when a signal is only partially or imperfectly displayed; which, 
 while resulting in a certain loss of time, has not argued much 
 against their introduction. 
 
 Within the housing or banjo of 
 the disk signal is placed the arrange- 
 ment shown in Fig. 130, which 
 constitutes the disk instrument. It 
 consists of an electromagnet, F, 
 whose armature, D, moves a member, 
 L, to which the banner, B, of colored 
 cloth for indications by day, and 
 the disk, A, of colored glass for night 
 indications, are -fastened. D is pivoted 
 at K, and its continuity of motion 
 causes a greater flux to pass through 
 the magnetic circuit by decreasing 
 the sectional area of the air-gap. 
 F is held in place by the brass piece 
 I-E, this being secured in the iron 
 base, G, by the eccentric washers, H, 
 G being fastened to the inside of 
 the banjo. The external circuit is 
 connected to the binding posts, C. 
 A and B move before clear glass apertures in the housing, a 
 lamp being placed in the rear of A. 
 
 This type of signal mechanism is used extensively on the 
 Lehigh Valley, Philadelphia and Reading, and Chicago and 
 North Western. The disadvantage of the cloth banner is the 
 rapidity with which the coloring matter fades in the penetrating 
 sunlight which often strikes it in both summer and winter. 
 
 An indicator, which is used at switches, towers, and inter- 
 locking points, and is usually in series with the indicator line- 
 
 FIG. 130 
 
HALL APPARATUS 
 
 133 
 
 wire, is shown in Fig: 131. It is in reality a miniature modifica- 
 tion of the disk signal mechanism, and consists of an armature, C, 
 pivoted at G, to which is attached a small red disk or banner, D ; 
 this armature moving between the polar extensions, B, of an 
 electromagnet, A. D is counterbalanced by an adjustable nut, 
 E, so that the energy required to move the armature will be at a 
 minimum. Insulated from but fastened to the magnetic yoke are 
 the binding posts, F, to which the external circuit is connected. 
 The moving system is of such design that the air-gap remains 
 practically constant, while its sectional area continually increases 
 
 FIG. 131 
 
 FIG. 132 
 
 with upward movement of the disk, the ampere-turns required 
 being therefore very low. A slight amount of rust will prevent 
 movement of the armature, hence the indicator is enclosed in a 
 sealed housing having a glass aperture before which the banner 
 moves. 
 
 One type of polarized relay is illustrated in Pig. 132. Upon 
 a porcelain or slate base the magnet coils, M, with their cores 
 and supports are mounted, with the armatures, P and N, the 
 former polarized or permanently magnetic, the latter neutral. 
 D, D, are the polar contacts; and <?, C, the neutral front and back 
 contacts, and fingers. Binding posts, B and B' , are for the 
 external connection of these coils and contacts. 
 
134 
 
 AUTOMATIC BLOCK SIGNALS 
 
 In Fig. 133 an interlocking relay is shown, in section and 
 elevation. This in reality consists of two relays, whose arma- 
 tures, A and A', are dependent upon one another. This is 
 effected by the locking dogs, D, whose points, P, engage with 
 the ends, E, on the armatures, by the action of the rollers, R. 
 When current ceases to pass through the magnet coils, the 
 armature falls (if not locked) and its roller forces over the dog, 
 thereby preventing the other armature from dropping. Each 
 
 . 
 
 
 
 FIG. 133 
 
 relay has four sets of front and back contacts, the construction 
 being similar in many respects to those herein described. 
 
 Fig. 134 shows a glass-enclosed, also a glass-niounted, neutral 
 relay, with four front and four back contacts. Such relays are 
 generally employed as track instruments, and are wound to a 
 comparatively low resistance. 
 
 The principle of the type, D, structure is illustrated in Fig. 
 135. G is the main gear, which, driven by a motor, in turn 
 produces the reciprocation necessary to clear the semaphore, 
 
HALL APPARATUS 
 
 135 
 
 through the lever, J. Both / and G have the shaft, A, as a center, 
 J being loose thereon. M is the slot magnet, whose armature 
 
 FIG. 134 
 
 is secured on and gives motion to the pivoted bar, F. H is a 
 pivot bearing for the end of the rod, B, and R is a roller stud 
 on the same. D is a trigger-shaped piece fastened to G, which 
 engages with the end, E. If M be deenergized, and G rotated 
 
136 
 
 AUTOMATIC BLOCK SIGNALS 
 
 in the direction of the arrow by the motor, when D strikes E, 
 R will force F up, and cause D to pass E, thus imparting no 
 motion to / or the semaphore, a stop, S, preventing F from 
 being thrown too far. If M be energized, G evidently, by a 
 converse reasoning, will cause / to move in the direction of 
 
 FIG. 135 
 
 the gear, and, clear the semaphore. The requisite changes in 
 interconnection and disengagement are also effected by the 
 moving system, but these need not be entered into. 
 
 A type, F, motor mechanism for a double semaphore structure 
 is shown in Fig. 136, and is similar in mechanical design to 
 the electro-gas arrangement. Two independent sets of mechan- 
 ism are used, but only one will be described. The motor, 15, 
 frame 5, dashpot pistons, and clutch magnets are supported 
 by the iron base, 8, as are also the side frames-, 6 and 7, which 
 act as housings for the gear shafts, 36 and 37, and retain the 
 clutch levers, 11 and 12 (which are hidden from view). Rigidly 
 secured to the dashpot cylinder, 29, is the thrust rod, 13, the dash- 
 pot pistons being mounted on pedestals within the frame and on 
 the base, 8. This thrust rod is guided by the cylinder, 29, the 
 upper end of 13 passing through a bearing in frame 5. The sema- 
 phore, connected to 24 by a link, is held at clear by a latch en- 
 gaging with a lug on the clearing lever, 22. The thrust rod, 13, 
 carries the latch support, 96, which in turn carries clearing lever 
 
HALL APPARATUS 
 
 1ST 
 
 22, thrust piece 100, and a latch engaging with the lug on 1, to 
 hold the semaphore at clear. 100 carries a V-shaped latch, 
 33, which engages with the lug on the clearing lever, 22, the 
 clearing operation being indirectly performed by the train of 
 motor-driven gears, 3. 
 The movable contacts of the circuit controller, 21, are operated 
 
 FIG. 136 
 
 by the control rod, 49, and escapement lever, 47; the latter is 
 thrown by the latch support roller, 52. The front armatures 
 of the clutch magnets, 1 (one magnet being on each side), con- 
 trol the parallel contacts of the motor circuit, while the back 
 armatures are secured to the clutch levers, 11, thus keeping 
 the latter under the control of the magnets. When the home 
 blade is at stop, the controller contacts for the series motor, 
 15, are closed, and the distant clutch magnets are on open 
 
138 AUTOMATIC BLOCK SIGNALS 
 
 circuit, so that the latter cannot be cleared before the home is 
 fully at clear. The motor circuit is closed directly the home 
 clutch magnet is energized, by the front contacts, 4; while 
 simultaneously the rear armature, 9, is attracted, thus pre- 
 venting the clutch lever, 11, from moving when the stud roller 
 exerts its pressure. The motor now drives the gears and 
 brings 38 under 100, forcing it up. As 11 is securely held by 
 9, 22 cannot swing back ; hence the thrust rod and all its appur- 
 tenances are carried to the clear position, in moving to which 
 roller, 19, pivoted in 22, rolls against 11. The final portion of 
 this movement to clear brings roller 52 against the short link 
 of escapement, 47, rocking it about 56, so that rod 49 operates 
 the circuit controller and opens the motor circuit, at the same 
 time closing that of the distant. The home is held at clear 
 by the action of the lug on 11, which engages with a latch on 
 96, releasing the downward pressure on the stud roller, and 
 allowing the distant to be cleared by the motor. A stud roller 
 similar to 38 is on the opposite side of the gear and displaced 
 180 from 38; for clearing the other blade, a similar structure 
 to 96-100-52-, etc., is employed. 
 
 After having been cleared, 38 moves beneath 100, the signal 
 circuit being broken as soon as the clutch magnet is energized, 
 as before. The motor circuit is opened by the front armature, 
 and the rear armature allows 11 to swing back sufficiently to 
 permit the retaining latch to disengage and cause the return 
 to danger by gravity, this movement being dampened by the 
 dashpot, 29. As soon as this movement begins, the circuit 
 controllers, 21, are reversed, and should the motor inadver- 
 tently become on closed circuit the gears will merely revolve 
 uselessly, since 38; cannot clear the semaphores unless clutch 
 magnets, 1, are energized. Should the clutch magnets become 
 deenergized with the blades partly at clear, 22 would swing 
 back, since latch 33 is permitted to pass the clearing lever lug, 
 thereby throwing the semaphore to danger, as 100 swings on 
 its pivot 105 to the normal position after the stud roller has 
 moved beneath it. 
 
 A double electromechanical slot is shown in elevation and 
 section in Fig. 137. The dashpot shells, Z), are secured to the 
 rods, R, which are interposed in the semaphore links. When B 
 is forced upward by the operator's lever, L will tend to swing 
 
HALL APPARATUS 
 
 139 
 
 outward on its pivot. If the enclosed coil magnet, M, be ener- 
 gized, its armature, A, will hold C at the inner position, so that 
 L cannot move, and motion of B is transmitted to R. If, 
 however, M be deenergized, roller throws C over, in opposition 
 
 FIG. 137 
 
 to the spring S, and B moves upward without throwing the 
 semaphore. 
 
 In Fig. 138, which illustrates a combined tower indicator and 
 bell, S is a miniature semaphore showing the condition of a track 
 section or signal, which is thrown by the armature, A, of the 
 magnet, M , through the bell crank, L. When S moves to dan- 
 
140 
 
 AUTOMATIC BLOCK SIGNALS 
 
 ger, the clapper C, on the semaphore rock-shaft strikes a gong, G, 
 thus warning the signal operator. The armature also carries front 
 and back contacts T for introduction in the circuits of the tower. 
 
 Fig. 139 outlines a switch instrument which does not close 
 the circuit contacts (on a normal danger network) until the 
 rail point has reached its fully normal position. These contacts, 
 C, are actuated by the links, L, arranged about the rock shaft, R. 
 When the sector, S, is moved in the direction of the arrow, the 
 
 FIG. 139 
 
 steel block, B, engages with the piece, A, and thus opens the con- 
 tacts. The switch link is fastened to D. 
 
 A standard switch indicator is shown in >Fig. 140, the miniature 
 semaphore being moved in a somewhat similar manner to that 
 
HALL APPARATUS 
 
 141 
 
 shown in Fig. 138. Front and back contacts are also provided, 
 a push button, P, being introduced in series with the magnet 
 winding, and in shunt with the front "stick" contact. With 
 
 FIG. 140 
 
 this device, a trainman, by pressing the button, may ascertain 
 the condition of the two preceding blocks, the semaphore being 
 normally in the danger position. 
 
 In Fig. 141 the standard wireless connections for single-track 
 
 FIG. 141 
 
 one-way movements with overlap appear. The motor, Af, is 
 in series with the front-contact of a slow-releasing relay in series 
 with the track relay, D, front contact, the contacts, 1, 2, 3, 4 
 being operated simultaneously by movement of H. 
 
142 
 
 AUTOMATIC BLOCK SIGNALS 
 
 In Fig. 142 the wireless connections of a normal clear home 
 and distant signal, S, for one of the tracks of a double-track road, 
 and a polarized relay, P, are shown. The scheme of interconnec- 
 tion is an elaboration of that already given in Fig. 70, utilizing 
 a compound slot, h, in series with the motor for the home blade 
 and a simple wound slow-releasing slot, d, for the distant. This 
 is the usual practice, as the home is cleared first, and the effect 
 
 FIG. 142 
 
 of drop in potential is not so manifest in the case of the distant 
 slot. E is a polarity reverser, for the control of the preceding 
 distant. 
 
 Fig. 142a shows the standard connections for a normal clear 
 home and distant disk-signal on one of the tracks of a double- 
 track road, H being the home banjo. This arrangement is 
 an extension of the home banjo-circuit given in the preceding 
 chapter, a polarized relay being used, as in the latter case. 
 
HALL APPARATUS 
 
 143 
 
 T has two components, which are connected in series. When 
 one of the neutral armatures comes in contact with the back 
 contact point (by short-circuiting of the track) but one cell 
 is connected to the latter. N operates both blades, being 
 under rather heavy discharge when the low-resistance winding 
 is in circuit and the disk being cleared, and under slight demand 
 when at clear. The insulating joints are not shown opposite, 
 
 FIG. 142o 
 
 as in practice they are staggered, in common with the ordinary 
 joints. 
 
 Figs. 143 and 143a are consecutive circuits showing the Hewett 
 line-wire scheme of normal danger operation, with a normally 
 open track- circuit, the track relays being normally closed for 
 switch indicator control. At signal 522, the track element is 
 connected in series with the opposed or differential relays or 
 windings A and B (having a common armature), but in this case 
 
144 
 
 AUTOMATIC BLOCK SIGNALS 
 
HALL APPARATUS 
 
 145 
 
 no energization results, so contact C is open. When A (which is 
 in shunt with the track) is short-circuited by a train or otherwise 
 
 B is fully energized, and consequently, C is raised ; T receives 
 current from K, and is in series with a differential winding, U. 
 
 At 532, a train appears in the home block, which short-circuits 
 the upper winding, L, and fully energizes M ; thus raising both 
 
146 AUTOMATIC BLOCK SIGNALS 
 
 contact points, and clearing 542. The 4-ohm relay, 0, is also 
 energized (by the closing of the lower contact of M) from P. 
 The home mechanism, when cleared, closes two contacts and 
 opens one ; when moving to stop, the reverse ; D is a relay having 
 two connections of its windings: one of 200 ohms, the high 
 resistance, and the other of 20 ohms, this being effected by a 
 shunting contact operated by the home mechanism. Also, 
 when either the home or distant clears, short-circuiting con- 
 tacts are operated, which throw into circuit the high-resistance 
 slot or retaining coil, which maintains the clear position of the 
 semaphores, with insignificant current consumption. 
 
 When the armature contact, Q, is closed, 7 is connected to the 
 track; and, if energized, the local home will clear, and subse- 
 quently, the distant. At 522, N is a resistance in series with the 
 distant signal line through G, which is the cause of a supple- 
 mental energization of /, having a subsidiary control over 7. 
 The indicator, R, is connected to the indicator line and common, 
 and is in series with F. The home semaphore at 522 is con- 
 trolled by E, and at 532 by a front contact of 7. 
 
CHAPTER XI. 
 UNION APPARATUS. 
 
 IN Fig. 144 the track and motor connections embodied in the 
 Union standard normal clear polarized rail- circuit scheme of 
 operation are shown. The home signal, H, protects the block 
 immediately behind it (not shown), the approaching train in 
 
 Mam botfery 
 
 U 
 
 S/o* 
 re/eas/n<? 
 
 Tr-oc/t 6o#eiy 
 fb/e 
 
 Trotn 
 
 V 
 
 FIG. 144 
 
 the block preceding short-circuiting the track section and hold- 
 ing the signal at D at stop, in a manner now to be described. 
 Excepting the track battery and pole changer at H, the entire 
 arrangement of accessories and connections shown in the figure 
 is at D. H has the same subsidiary devices, but their delineation 
 would over-complicate the diagram. 
 
 The track battery at H is not connected directly to the track, 
 a pole changer being introduced. The polarized relay is con- 
 nected at the other end of the block (relay control being inter- 
 posed where the blocks are of excessive length) and is affected 
 
 147 
 
148 AUTOMATIC BLOCK SIGNALS 
 
 by three conditions: (1) the cessation or continuance of current, 
 irrespective of its polarity; (2) the establishing of current of one 
 polarity; and (3) establishing of current of the opposite polarity. 
 Under certain conditions it would be apparent that the polar 
 contact would still remain closed upon cessation of current, when 
 the latter was in the proper direction. To provide against such 
 a contingency, a supplemental break is introduced, as will be 
 apparent later. 
 
 The polarized relay has two armatures, a neutral and a polar; 
 the former being raised whenever current circulates around the 
 coils ; and the latter closing its contact when the current is in one 
 direction and opening it when a reverse polarity is set up. The 
 neutral contact controls the home semaphore, and the polar 
 contact the distant semaphore in every case. When a train 
 occupies the block (as is the case for the signal at D, or by rea- 
 son of an open switch or similar cause), the polarized relay is 
 de-energized; the home signal assuming the danger position, by 
 the action of gravity. This movement to stop operates the 
 pole changer, and thereby throws the distant signal in the rear 
 to the caution position, through the action of the polar con- 
 tact, distant slot, and gravity. 
 
 The reversal of polarity must evidently cause a momentary 
 drop of the neutral armature, due to the instantaneous ces- 
 sation of current through the magnet coils, followed immediately 
 by a sweeping out of the residual flux. As the contact of this 
 armature is in the home slot and motor circuits, it follows 
 that the signal arm must move to danger. However, an 
 intermediate slow-releasing relay contact is in series with 
 the motor and home slot, the magnets of this relay being in 
 series with the neutral armature contact and having a very 
 high self-induction, being also provided with a copper tube 
 for choking effect, so that before the self-induction current 
 occasioned on breaking the circuit can neutralize itself (and 
 consequently the residual flux cease) the circuit is again com- 
 pleted, and its magnetism fully restored; the home signal arm 
 being thus unaffected. 
 
 The slot magnets are compound wound, having two sepa- 
 rate windings, the inner of many turns and high resistance 
 and the outer of few turns and low resistance. The high- 
 resistance coils are connected in multiple with the main battery, 
 
UNION APPARATUS 149 
 
 and the low- resistance coils in series with the motor; so that 
 when a heavy current passes through the motor it must pro- 
 duce a corresponding increase in the magnetic effect upon the 
 slot magnet armatures. 
 
 The sets of contacts, 1, 2, and 3, are indirectly operated by 
 movement of the home semaphore; and 4 by the distant. 
 Both 2 and 3 are normally closed (when the signal is at clear), 
 while 1 is normally open (shown closed in the figure, since 
 the signal is at stop). When the distant arm is at clear, 4 is 
 opened; when at caution, closed, as in the diagram. The 
 high-resistance home slot winding is connected across the bat- 
 tery through the contact of the slow-releasing relay; the 
 same winding of the distant slot being in multiple with the 
 battery, through the polar and neutral contacts of the polar- 
 ized relay on one side, and through the home operated con- 
 tacts 3 on the other side. 
 
 The motor is connected to the battery for the movement 
 of the home blade through the low-resistance winding of the 
 home slot, normally open contacts 1, and the slow-releasing 
 relay armature; and for movement of the distant semaphore 
 through the normally closed contacts 2, normally open con- 
 tacts 4, low-resistance winding of the distant slot, and the polar 
 and neutral contacts of the polarized relay. 
 
 A partial elevation and section of one type of such a signal 
 mechanism for semaphores is shown in Fig. 145. The motor, 
 17, through its armature shaft, 39, drives the large gear, 21, 
 whose pinion, 22, engages with the sprocket-carrying, gear 20. 
 The home semaphore is connected to the rod, 7, pivoted at 33, 
 and the distant to 8; the former being at clear. Motion is 
 imparted to these rods by the movable members, 37, which 
 rock about a shaft, 32. These members carry the slot magnets 
 9 and 34, to which connection is made through flexible cable, 
 to the binding posts, 36. The armatures, 40, of these magnets, 
 through the latch ends, 31, engage with the train of links, 30, 
 25, 29, and 28, so that when 34 is energized under specific 
 conditions, the cam piece, 28, is immovable. , 
 
 To the ends of the arms, 37, are pivoted two links, 6 and 10. 
 The former operates the plunger, 4, of a dashpot, the shell, 3, of 
 which is held in the mechanism frame. The relative retarda- 
 tion is varied by the screw, 2, which governs the discharge of 
 
150 
 
 AUTOMATIC BLOCK SIGNALS 
 
 the entrained air through the orifice, 1. These dashpots prevent 
 spasmodic movements of the mechanism when returning to 
 the stop position by gravity. Link 10 operates a current 
 reverser or pole changer, the essential parts of which are the 
 sets of contact springs, 14 and 13, with the scraping pieces, 12. 
 Connection to the track circuit is effected through the binding 
 posts, 11, 15, and 42. 
 
 FIG. 145 
 
 As only the home blade is at the clear position, the distant 
 block must be occupied or dangerous. If it be supposed to be 
 again clear, 9 will be energized simultaneously with the passing 
 of the current through the motor. As the motor gains speed, 
 the chain starts to move, and as 44 is held rigid by the inter- 
 posed links and the spring, 38, 37 will be carried upward by 
 the action of the roller engaging with 44. When it reaches 
 its extreme upward position, a stud opposes gravity through 
 
UNION APPARATUS 
 
 151 
 
 the latch, 41, latching taking place when 40 passes the hook. At 
 the same time, the motor circuit is opened at contact springs, 
 26, by the insulated strip, 27, through the pivoted piece, 46, 
 which 37 strikes, since 43 and 24 are in series with the motor. 
 The brake, 45, is applied when the current through the motor 
 ceases, thus bringing the armature to an almost immediate 
 stop. The electrical connections have been described in con- 
 nection with the preceding figure, the external and intercon- 
 nections being made at the posts, 5. 
 
 In Fig. 146 the arrangement, which is frequently used to 
 clear the signal arm, is isolated. The motor drives the chain, 
 J, in the direction of the arrows. This causes a roller, R, to 
 strike the pivoted member, E y which is connected to the links, 
 F and G. The semaphore rod is pivoted at A, and the whole 
 
 FIG. 146 
 
 structure at J5, the dashpot plunger and polarity changer being 
 operated from end I. If the slot magnet, D, be energized, arma- 
 ture C, through its hook end, will prevent H from moving 
 when E is struck, through the action of F and G. Hence R 
 raises E and the entire arm about B as a center, thus clearing 
 the semaphore in opposition to gravity. If D is not energized, 
 this cannot occur; and if it be de-energized when the blade is 
 at clear, the release of H will cause it to fall to stop. 
 
 The Union standard disk mechanism is illustrated in Fig. 
 147. It consists of an aluminum disk or colored banner, D, 
 carrying a lens at its center; and suspended upon a rod, which 
 passes through the pivoted armature, A, of the electromagnet, 
 M. The moving system is counterweighted at W, the electro- 
 magnet being held within a box fastened to the rear of the 
 narrow case, a front view of which is shown at C. A hinged 
 
152 AUTOMATIC BLOCK SIGNALS 
 
 lamp is placed in the rear of C for night signaling, the rays of 
 this lamp passing through a lens at the center of the disk. 
 The rear of the aperture, P, before which the banner moves, 
 is painted white, so that when the latter is raised a clear indi- 
 cation is given, the lower end only being visible, the clear 
 lens before the lamp being also seen at the center of P. An 
 opening is provided so that repairs and connections can be 
 readily made. 
 
 In Fig. 148 a slow releasing relay is shown, A being the 
 armature, B the back contact prong, and F the front contact. 
 The magnets are wound to such a resistance that a high self- 
 induction results at the current strength normally passing 
 
 FIG. 147 
 
 through the coils. The magnetic circuit is long and of generous 
 sectional area, the pole tips presenting a large surface to the 
 armature. A soft copper sleeve is slipped over each core 
 before the winding is put on. The eddy currents set up momen- 
 tarily in the sleeve when any change in exciting current occurs, 
 oppose any change in flux, and thus tend to retain the mag- 
 netism. These factors, combined with a short lift, small air 
 gap, large percentage of residual magnetism, and high working 
 flux density (much greater than is actually required for the 
 mechanical work done) produce a slow release of the armature 
 when the energizing current is interrupted. Such a relay is 
 used in connection with the polarized wireless system, when 
 slow-releasing slots are not employed, to prevent open-circuiting 
 
UNION APPARATUS 
 
 153 
 
 of the home slot circuit when a momentary reversal of polarity 
 occurs at the polarized relay. 
 
 Fig. 149 illustrates a vertical rotary switch-circuit controller 
 in section. This instrument is intended to short-circuit the 
 track relay at a track switch when the latter is open, or to 
 short-circuit the signal relay. When the switch is closed, 
 the contacts are open, so that the electrical conditions of the 
 section are not interfered with. The arrangement consists of 
 the dust and waterproof cast iron housing, A, provided with a 
 
 FIG. 148 
 
 FIG. 149 
 
 hinged cover, B, which is held securely in place when closed 
 by a lock and clasp, C. Fastened to an insulating strip are 
 the phosphor-bronze platinum-tipped strips, F, with the binding 
 nuts, D, for connection to the external circuits. The housing 
 is fastened to the long tie, /, by lag screws, adjacent to the 
 switch-point rail. It is connected to the latter by the rod, 7, 
 which imparts motion to the crank, G, fastened to the cam 
 piece, H, the pivot being the shaft, N. Riding on the inclined 
 flat lip, H, is a small roller, L, fastened to a cast iron rocking 
 piece pivoted to the shaft, M, L being pressed against H by 
 the action of the spring, 0. 
 
154 
 
 AUTOMATIC BLOCK SIGNALS 
 
 Closing the switch will, through the rod, 7, produce a move- 
 ment of the rotary cam piece and thus throw the roller, L } up- 
 ward, which compresses the spring, 0, and moves the lower insu- 
 lating strip downward, allowing the contact strips, F, to separate, 
 thus breaking the circuit. With G in the position shown in 
 the figure, the switch is open, the contact strips thus short- 
 circuiting the track. The pur- 
 pose of the rotary cam is to 
 absorb the motion given to G 
 , by every car wheel which passes 
 I over the switch-point rail, and 
 prevent its being communicated 
 f to the contact strips. In Fig. 
 150 the mode of application 
 of such a box to a switch is 
 shown. K is the switch-point 
 rail, which is connected to the box crank by the rod, 7. 
 In Fig. 151 a duplex rotary circuit-controller is illustrated. 
 
 FIG. 150 
 
 FIG. 151 
 
 This arrangement is intended to control from one to four sep- 
 arate circuits; or it may be employed to reverse the polarity 
 or connections of two independent circuits. It is frequently 
 employed in place of the switch circuit-controller above described. 
 The instrument consists (Fig. 151a) of two operating cams, V, 
 
UNION APPARATUS 
 
 155 
 
 whose outer edges bear against rollers arranged on pivoted 
 bars, the latter carrying contact springs and connectors, X. 
 
 Within the weatherproof cast iron housing, 11 (this being 
 merely a connection plan), are 
 two cams, 14 and 27, arranged 
 to move about a pivot, 26. 
 These cams are secured to the 
 crank, 25, operated by the switch, 
 semaphore, or interlocking ma- 
 chine rod, 24. The outer edges 
 of the cams bear against small 
 rollers, 13, secured to the rocking 
 members, 12, pivoted at 28. 
 These rocking members carry 
 the insulated contact springs, 
 21, 22, 17, and 18. 
 
 The stationary pieces, 15 and 
 29, also carry insulated contact 
 spring strips, 16, 19, 20, and 23, 
 which are in or out of contact 
 with the movable strips accord- 
 ing to the position of the cams, 
 and consequently the position 
 of 24. Connecting posts, 30 
 
 and 31, to which the wires, 5 and 6 pass, are insulated and 
 stationary, and have a projection beneath which obstructs 
 the motion of the movable contact springs. In the position 
 of the cams shown, 21 is in contact with 30, and 31 
 with 17. 
 
 To sho,v the use of the arrangement as a reverser of polarity, 
 suppose that a track battery is connected to 1 and 2, one track 
 rail being connected to 3 and 4. If the other rail is connected to 
 5, it is evident that the polarity of the track circuit is reversed 
 at every consecutive movement of 24; which may be secured to 
 the home semaphore of a signal on the wireless or polarized 
 track-circuit system. By connecting one side of one circuit to 
 1 and 3, and the other side to 7 and 8, we have double-pole 
 simultaneous control of two circuits. Numerous such combi- 
 nations will occur to the signalman. 
 
 Fig. 152 shows a polarized indicator mechanism, such as 
 
 FIG. 151a 
 
156 
 
 AUTOMATIC BLOCK SIGNALS 
 
 is used at a siding or crossover, or to indicate the state of two 
 or more distant devices having suitable battery connections. 
 When applied at a siding switch, it apprises the brakeman of 
 an approaching train, and the movement of the home signal 
 governing the section in which the switch is located. When 
 used in conjunction with a slotted mechanical signal, it may 
 similarly indicate the approach of a train, and the clearing or 
 return of the semaphore. 
 
 FIG. 152 
 
 It consists of an electromagnet, M, whose permanently mag- 
 netized armature, A, is held centrally in a state of static equi- 
 librium by the adjustable springs, S, between the pole pieces, R. 
 This armature is pivoted at P, and engages at its lower end with 
 a rocking member, B, the latter giving motion to a pointer (not 
 shown) which has three positions of rest, according to the direc- 
 tion of the current or its continuity. The mechanism is enclosed 
 in a cast iron box, placed at the top of an upright located near 
 the switch. 
 
UNION APPARATUS 
 
 157 
 
 Fig. 153 shows a front and side elevation of a multiple unit 
 semaphore indicator, with the binding posts and armature con- 
 tacts. This type has three front contacts, 1, 2, and 3, also two 
 back contacts, 4 and 5. The electromagnet, 8, through the 
 armature, 11, operates a shaft, 7, which is secured to a miniature 
 semaphore moving before the face glass, 9. Interconnection 
 and connection to external circuits is effected at the binding 
 posts, 10. These instruments are mounted in a moisture-proof 
 
 FIG. 153 
 
 housing in gangs or banks, and find application in train sheds, 
 signal towers, and stations. Frequently single-stroke and vibrat- 
 ing bells supplement these devices, giving an audible announce- 
 ment of the semaphore movement. A common bell for each 
 bank may be used, but it is better practice to employ individual 
 bells. 
 
 Fig. 154 illustrates a neutral type disk indicator, which is 
 applied where it is desired that two indications be given, as, for 
 example, to indicate the condition of a given block, whether 
 occupied or clear. It consists of a metal disk, D (usually red), 
 
158 
 
 AUTOMATIC BLOCK SIGNALS 
 
 which is actuated by the armature of the electromagnet, M, 
 the latter being in series with a track-relay armature contact. 
 D is fastened upon the vertical shaft, S, which is fastened by a 
 link and stud, P, to an extension, E, of the armature. When M 
 is energized, E moves outward a trifle, thus permitting P to 
 swing around, and present the edge of the disk to the observer. 
 B is of non-magnetic material, the armature being partly enclosed 
 by it. 
 
 FIG. 154 
 
 FIG. 155 
 
 To apprise a tower attendant of the presence of a train in a 
 certain block, or indicate the approach of a train to a signal, 
 a drop annunciator is used. This consists, as shown in Fig. 155, 
 of a banner, #, with the desired inscription on its face, which 
 moves before a glass-covered aperture in the housing (shown 
 removed). This banner is affixed to a pivoted casting, L, which 
 is provided with a handle or finger, H, and is held in its upward 
 position by a trip upon the piece, S, pivoted at P, whose position 
 and movement are adjustable. To the latter, the armature, A, 
 of the electromagnet, M, is fastened. When a current passes 
 
UNION APPARATUS 
 
 159 
 
 through M, B is released in an obvious manner, and is restored 
 by means of the handle, H. An auxiliary circuit for audible 
 announcement of the movement of B is sometimes made use of, 
 and consists of a battery and bell in series with the contacts, 
 K-C, the latter being closed when L is in its lower position. 
 
 Drop annunciators are used in connection with crossing cir- 
 cuits (see Fig. 31) to announce approaching trains, and at inter- 
 locking towers to avoid delays caused by switching engines 
 drilling within yard limits. Delays to through passenger trains 
 by long, slow-moving freight trains, which receive a signal prior 
 to the former, are prevented by its use, so that the operator can 
 first give the passenger train the right of way. 
 
 FIG. 156 
 
 One form of circuit controller, the application of which was 
 considered in Fig. 77, is illustrated in Fig. 156, G being a part 
 section and elevation, and F a front view. The electromagnet, 
 A, enclosed in a box having a glass door, H, is in series with the 
 armature contacts, D-C, connection to external circuits being 
 afforded by the lugs, E. When the knob, B, is raised, these con- 
 tacts are .closed, hence a current passes around A (providing 
 the external circuit is otherwise complete) thus raising the 
 armature, C, and maintaining the energization of A. Should 
 the external circuit be opened, C will fall, and A will be dee'n- 
 ergized, until C is again raised by the operator, irrespective of 
 the condition of the external circuit. 
 
CHAPTER XII. 
 
 ELECTRO-PNEUMATIC AND ELECTRO-GAS SYSTEMS. 
 
 ELECTRO-PNEUMATIC systems, which are used on many busy 
 lines, employ low voltage controlling circuits, the working 
 medium for operating switches and semaphores being com- 
 pressed air, supplied by a local compression plant and conveyed 
 to the subsidiary apparatus through underground pipes. The 
 circuits generally used on such systems (normal clear for single 
 track) are shown in Fig. 157. 
 
 1 
 
 
 U 
 
 
 
 i 
 
 n 
 
 
 
 i 
 
 I 
 
 
 u, 
 
 ~~n. 
 
 ^ 
 
 -n* 
 
 1 
 
 3' 
 
 3. 
 Jfi 
 
 TCTf 
 
 123 
 
 FIG. 157 
 
 Three consecutive home and distant signals, 121, 123, and 
 125, are considered, with single sections, a train being on the 
 block protected by 125. The admission of air to the cylinder 
 operating the home semaphore is controlled by the electro- 
 magnet, H, and to the distant cylinder by D. A circuit con- 
 troller, C, is operated by the home semaphore's movement, and 
 is closed when the latter is at clear; while K is a circuit breaking 
 
 160 
 
ELECTRO-PNEUMATIC, ETC., SYSTEMS 161 
 
 arrangement in series with the distant magnet, and operated by 
 the returning to the stop position of the home arm, thereby 
 preventing a clear distant arm when the home is at danger, an 
 occurrence which would be confusing to the engineman. Each 
 section is provided with a track battery, 6, and relay, R, as in 
 other systems. B is the main battery which operates the home 
 and distant control magnets, the former through a local circuit, 
 the latter over line wires. 
 
 The train, by short-circuiting the track relay, open-circuits 
 the main battery, and, by depriving the home magnet of current, 
 moves the home blade to the stop position. The distant also 
 assumes the caution position by the action of the circuit breaker; 
 the distant blade of 123 thus maintaining this position by reason 
 of its opened circuit controller. Sometimes the latter is effected 
 by using the polarized track-circuit principle, line wires not 
 being then used. 
 
 Liquid carbon dioxide (C0 2 ) has numerous advantages as a 
 source of power, which result from its enormous expansion at 
 almost any pressure desired, through the use of proper valves. 
 In exhausting at low pressure, or entering a chamber during 
 expansion, it precipitates no moisture; in fact it may be relied 
 upon to remove any moisture with which it comes in contact, 
 since its point of saturation is high. 
 
 The Hall electro-gas signal, which uses this agent as a motive 
 power, is now regarded as a very high development of the auto- 
 matic semaphore, and possesses inherent features which bid 
 fair to rank it as a standard type. It employs standard posts, 
 case, and fittings, with additional special accessories for the 
 control and reception of the gas and flasks. These flasks are 
 identical with those used for soda fountain purposes, and are 
 about four and one-half feet long and eight and one-half inches 
 in diameter, weighing when charged about 150 pounds, con- 
 taining 50 pounds of liquid gas. Two such flasks are used at 
 each signal, and are placed in a chute near the base of the 
 latter. 
 
 The flasks are provided with a safety valve blowing off at 
 2400 pounds pressure, and when charged exert a pressure of 
 about 800 pounds per square inch. In direct sunlight, or when 
 near a locomotive boiler, this valve operates, although the flasks 
 will actually stand about one and one-half times this pressure. 
 
162 
 
 AUTOMATIC BLOCK SIGNALS 
 
 Before passing to the operating cylinders, this is reduced to 
 about 40 pounds by a reducing valve. 
 
 In Figs. 158, 159, and 160, the mechanism of this signal is 
 revealed. The first is a front elevation, the second a side view, 
 
ELECTRO-PNEUMATIC, ETC., SYSTEMS 
 
 163 
 
 and the third a part section showing important details of con- 
 struction. The signal is a home and distant, although a three- 
 
 109- 
 
 FIG. 159 
 
 position structure can be equally well adapted to this motive 
 power. The gas expands and exerts its force through the verti- 
 
164 
 
 AUTOMATIC BLOCK SIGNALS 
 
 cal cylinders, 200, the semaphores being moved by the extended 
 cylinder rods, 70, the cylinders being movable, and the pistons 
 
 109 
 
 IOQ 
 
 FIG. 160 
 
 fixed to the mechanism frame. The home signal-control electro- 
 magnet appears on the right side and the distant on the left; 
 
ELECTRO-PNEUMATIC, ETC., SYSTEMS 165 
 
 these magnets, through their armatures, governing the admission 
 of gas to the working cylinders, and are interposed as a function 
 between the cylinders and flasks. 
 
 The magnets are controlled by track circuits on either line 
 wire or wireless systems, and are energized through a local bat- 
 tery. In connection with Fig. 162 such an arrangement will be 
 described. When a blade has been cleared, it is held in the clear 
 position by latches controlled by the magnets, their release 
 allowing gravity to throw the same to the stop position. The 
 home movement controls the distant as in other types, the 
 means by which this is effected being shown later. 
 
 The reducing valve, 31, whose gauge has two pointers, show- 
 ing the supply and working pressures, is connected to the 
 expansion chamber and valves, 100, the latter being controlled by 
 the magnets, the armatures, 12, raising the link, 109, and lever, 108. 
 The reducing valve is also in connection with the supply flask 
 through the pipe, 82. The semaphores are held at clear by the 
 clutch levers, 14 and 15, which are actuated by their attached ar- 
 matures, 7, moving before the poles of the magnets. When the 
 signal is at clear, the rocking latch, 21, holds it in this position by 
 engaging with the clutch lever. The roller buffer levers, 17 and 
 16, keep the clutch lever from striking the magnet poles when 
 the signal returns to the danger position, and maintain the arma- 
 ture at a short distance from the pole tips when in this position, 
 so that danger of freezing fast is eliminated. The magnets, it 
 will be seen, are double functioned, their front armatures opera- 
 ting the gas valve, and rear armature holding the signal at 
 clear. 
 
 When the signal has cleared, the cut-off levers, 114 and 115, 
 act, and cut off the gas from the working cylinder, allowing 
 it to exhaust at the same time, they being controlled through 
 the pawls, 116, pivoted at 48. These pawls engage with the roller, 
 20, at the upper position, the gas thus being shut off by their 
 mutual action, the stroke of the cylinder being varied by chang- 
 ing the point of release and clutch engagement. The clutch 
 casting, 9, is fastened to the cylinder rod, rod 47 guiding it. The 
 position of 9 can be changed, thus changing the stroke. A switch, 
 85, is operated by the rod, 44, when the stud, 19, is in engage- 
 ment with it, and rocks about a central shaft which carries 
 the contact blades. 
 
166 
 
 AUTOMATIC BLOCK SIGNALS 
 
 The clearing action is as follows: When the magnets, 39, are 
 energized, their armatures, 7 and 12, are attracted, the gas 
 valve being thereby opened through the links, 37, 108, and 109. 
 The supply valve, 96 (see Fig. 161), is raised, while the exhaust 
 port is simultaneously closed. Gas enters the cylinder through 
 the center of the piston, and raises the former, thus clearing 
 the signal. When the latch, 21, has moved past the projecting 
 finger of the clutch lever, 15, the pawl, 116, is raised by the 
 roller, 20, the cut-off lever, 115, moving downward. The links, 
 109 and 108, are thereby forced down, thus closing the supply 
 
 SUJlfl 
 
 FIG. 161 
 
 port, 96, and opening the exhaust port, 95. The latch, 21, 
 through its engaging with 15, thus opposes gravity, which 
 tends to move the mechanism to danger. As long as the 
 armature, 7, is attracted, the signal will remain at clear. 
 
 If the track section becomes occupied, armature 7 is released, 
 thereby causing lever 15 to move back. This releases 21, 
 and the semaphore moves to stop. A rapid downward move- 
 ment is prevented, as the air must be forced out through the 
 partly closed check valve, 98, the entrained air thus damping 
 this motion. 
 
 The expansion chamber, 30, is for the purpose of allowing the 
 gas to expand and increase its temperature. As an expanding 
 
ELECTRO-PNEUMATIC, ETC., SYSTEMS 167 
 
 gas always lowers in temperature, extracting heat from the 
 walls and adjacent parts, should freezing occur its particles 
 are too finely divided to produce any untoward results. Freez- 
 ing, however, by solidifying a gas having such great expan- 
 sibility, is a wasteful process. 
 
 The piston area is five square inches, and with a 40-pound 
 working pressure, the upward force is equivalent to 200 pounds, 
 which gives sufficient margin for positive action. Should 
 greater pressure be desirable, it can be changed by adjustment 
 of the reducing valve. About 12,500 movements can be made 
 per flask, with this working pressure, or 250 per pound of gas. 
 
 The magnets have two windings, which are connected in 
 multiple when the valve is being operated, the high-resistance 
 winding being used to hold the signal at clear. With the polar- 
 ized track-circuit scheme, when slow releasing clutches are 
 used, the second winding is first disconnected from the battery 
 and immediately closed upon itself by a switch, the induction 
 current thus set up (which opposes any change in flux) pre- 
 venting the cores from being at once demagnetized and retain- 
 ing the armature in position. 
 
 The slow-releasing clutch-magnets take a current of .0113 
 ampere at 4 volts, or .045 watt; and retain sufficient flux to 
 hold the semaphore at clear for 2.5 seconds after they are 
 disconnected from the battery, which gives ample time for 
 polarity reversal, and full energization in the opposite direction. 
 The valve requires .1 watt for its operation, and from four to 
 six cells are used in the battery to which the magnets are con- 
 nected. 
 
 In Fig. 162, A, B, and C, are the slot batteries respectively 
 of the normal danger electro-gas single-blade signals, 1, 2, and 3. 
 The cut sections, 5, 6, 7, and 8, have track relays of corresponding 
 number, which produce the required interconnection. The 
 battery, B, energizes the working magnets at 2 through the 
 lower armature contacts of relays 7 and 6, and the upper arma- 
 ture contact of 5. Hence, when 7 is short-circuited, 2 will 
 clear by the back contact of 7, providing the sections of 6 and 
 5 are unoccupied. 
 
 The actual circuits embodied in a normal clear, wireless, 
 two-arm, home and distant electro-gas semaphore, for a single- 
 track signal system, are shown in Fig. 163. R is a polarized 
 
168 
 
 AUTOMATIC BLOCK SIGNALS 
 
 relay, whose neutral armature front contacts are connected 
 to the main battery, Q, and both polar and neutral armatures 
 to the home semaphore; P is a polarity reverser operating 
 
 FIG. 162 
 
 the preceding distant polar armature; N, a compound wound 
 and duplex armature magnet clearing (through its valve operat- 
 
 FIG. 163 
 
 ing armature) the home blade, and the distant. Each has 
 two windings : one of 280 ohms, and the other of 350 ohms. 
 These are connected in multiple when the semaphores are to 
 
ELECTRO-PNEUMATIC, ETC., SYSTEMS 169 
 
 be cleared; the high resistance winding alone being used to 
 hold it at clear. When the home blade is cleared, switch L 
 is closed, thus giving current to the distant magnet from Q. 
 K is a switch arm which is in contact with the upper finger 
 when the home semaphore is at clear, and with the lower when 
 at stop. Its function is to short-circuit the 280-ohm winding, 
 thus leaving in circuit only the high resistance coils. Switch 
 S connects the low resistance winding in shunt with the high 
 resistance winding, it being open when the distant blade is 
 clear, thus decreasing the watts used. 
 
CHAPTER XIII. 
 ELECTRIC LOCKING. 
 
 AN electric lock is a device, electrically controlled, which 
 interposes a small latch or bar at a notch or recess in a mov- 
 able or sliding piece, so that the latter cannot be given motion 
 except under conditions governed by the lock. This moving 
 piece obviously may be a semaphore, switch, or interlocking 
 machine rod; in fact anything whose automatic control is 
 desired. 
 
 Electric locking is sometimes introduced in mechanical 
 levers, so that a signal operator cannot return to caution a 
 clear distant that a train has just passed, then return the home 
 to stop; permitting him thereafter to set up a false clear con- 
 dition of a conflicting route by the mechanical unlocking that 
 takes place. The lock circuit is through the rails of the section 
 intervening between the home and distant signals, and in 
 series with a battery and the lock magnets of the conflicting 
 levers. The train may either complete the circuit directly or 
 through the medium of a relay contact. Separate circuits 
 may also be employed to lock the individual levers. 
 
 Electric locking, as a subsidiary function, is treated of in 
 Chapter 5. It is scarcely possible to design a semi-automatic 
 connection arrangement without the use of such locking; it 
 forming the simplest scheme for controlling routes of any 
 desired combination. 
 
 When a plate or rod connected to a lever has a notch or 
 aperture into which a securety held but freely moving locking 
 member drops, motion of the former can or cannot be effected, 
 according to the position of the latter. Thus in Fig. 164, D 
 is a rigid stationary plate having an aperture, S', C a movable 
 plate connected to the lever to be locked; and L the armature 
 of an electromagnet, R. If A be an unlocking controller, 
 when it is moved in the direction of the arrow its contacts 
 will be closed and a current pass from B through R, raising 
 
 170 
 
ELECTRIC LOCKING 
 
 171 
 
 L and unlocking C, and thereby rendering the lever free. Con- 
 flicting routes may thus be protected electrically. 
 
 A section of one form of switch lock is given in Fig. 165. 
 Within a suitable housing, H, is placed an electromagnet, A, 
 whose armature, B, carries a locking piece, F; the latter engaging 
 
 with a slot or recess in a rod, E, connected mechanically with 
 the switch point. Before the switch can be thrown, E must 
 be free to move, which will not be the case if the armature is 
 down, due to the locking which occurs by F falling into both 
 a slot in the boss, Z), and the rod slot. When current passes 
 
 J/rV^S8SS^0 
 ' // Ss /7~S/// / / 
 
 FIG. 165 
 
 around A, B will be raised and E free to move. At G another 
 form of recess is shown, which has obvious advantages. B is 
 carefully adjusted by means of the pivot screws, C. 
 
 Electric locks are most frequently used to regulate inde- 
 pendently the function of the devices they are supplementary to. 
 
172 
 
 AUTOMATIC BLOCK SIGNALS 
 
 As their application is varied, a large number of different types 
 are in use. In Fig. 166 an electric lock applied to a mechan- 
 ical interlocking machine is shown. The armature, F, of the 
 electromagnet, M, carries a locking piece, E, which rests between 
 the stationary lugs, A, and a recess in the piece at the rear of D, 
 which is integral with the dog, G, of the locking bar, C; hence C 
 cannot be moved unless M is energized. B is a banner which 
 moves before an aperture in the housing, H, and is secured 
 to the lock piece, E, serving as an indicator to the operator 
 of the position of the lock bar. 
 
 Electric locking is sometimes applied as an intermediary to 
 
 FIG. 166 
 
 derails or switches, so that the cleared home signal (mechanical) 
 of an approaching train renders effective this locking, the 
 release being arranged to act subsequently, providing the 
 train has entered an unlocking track section and the home 
 signal has been thrown to the stop position: the latter having 
 to occur prior to the passing out of the train from the releasing 
 section. This leads to the consideration of electric releases 
 (although mechanical releases have been more extensively 
 applied). 
 
 Electric releases are adjuncts which allow of a temporary 
 manipulation of interlocked devices by the introduction of a 
 supplementary or compensating feature; so that the interlock- 
 
ELECTRIC LOCKING 
 
 173 
 
 ing machine can be set normal under specific conditions. 
 This release must be returned to its normal state (and con- 
 sequently the electric locking made effective) before any routes 
 can be set up for approaching trains. 
 
 In Fig. 167, B is a battery in series with which is connected 
 a stick relay, R, and the normally open contact-springs, C; and 
 whose armature contact is in series with 
 the normally open contacts, K. N is a 
 nut which moves along the threaded rod, 
 A, when the crank, H, is revolved. When 
 N is moved upward, the contacts, K, are 
 closed, but B discharges no current as the 
 armature of R is down. When N strikes 
 C, the latter are closed, thus allowing 
 a current to pass through R. M is a 
 circuit controller operated by throwing 
 the lever to which it is attached, while 
 T is a locking relay in series with the 
 contacts, K, and energized when they 
 are closed. To require the return of N 
 to the normal position, both C and K 
 must be opened, as the battery will have 
 two multiple paths for the current, the 
 first through the front contact of the 
 locking relay, its coils, the circuit con- 
 troller, and lock; the second through 
 the contacts, K, the/ armature of R, the 
 coils of R, and the circuit controller, 
 the lock, T, being thus shunted, and 
 consequently deenergized. When K-K 
 opened, however, this will not 
 
 arc 
 
 FIG. 167 
 
 occur, and the locked functions will be 
 released. 
 
 This release arrangement is placed at some distance from the 
 operator, so that some time will be taken to reach it, and this, 
 in addition to that required in moving N up and down suffices 
 to give the requisite time before the signal can be cleared for the 
 changed route, assuring greater safety thereby. 
 
 Fig. 168 is a section of the sector block and lock employed in 
 the Coleman arrangement. Within the housing, which is 
 
174 
 
 AUTOMATIC BLOCK SIGNALS 
 
 fastened to the frame of the interlocking machine, is the sector 
 block, S, which is moved about a center by the link, (7, fastened 
 to the lever, D, secured to the square shaft, G. D is connected to 
 
 the unlocking segment, so that 
 whenever the operator raises the 
 latch preparatory to throwing 
 the lever, it will describe an 
 arc. Within the case is an 
 electromagnet whose armature 
 extension, B, drops into a slot, P, 
 in the sector, a coinciding slot 
 being also in the case. Hence, 
 when the electromagnet is de- 
 energixed, B will fall into the 
 slot and securely lock S. B 
 also carries a banner through 
 the projecting rod, H, which 
 passes before an aperture, A, in 
 the case, and indicates to the 
 operator the position of B. 
 
 By providing a circuit con- 
 troller connected to a battery 
 
 circuit in which a locking electromagnet is included, it is evident 
 that a distant signal's movement may be employed to govern 
 the movement of an interlocked lever. In Fig. 169 we have an 
 interlocking magnet, B, applied to the lever, A, in such a manner 
 
 FIG. 168 
 
 I C 
 
 FIG. 169 
 
 that when its armature is down, motion of A in the reverse 
 direction cannot be effected. When the interlocked lever has 
 been thrown to its normal position, and the distant signal arm 
 fails to assume the caution position, since the contacts at the 
 controller, C, are open, it is not possible to throw the lever of the 
 
ELECTRIC LOCKING 175 
 
 home signal, H, to its full normal position. Hence such a route, 
 and all other conflicting routes, are successfully locked until D 
 has been cleared, thus raising the armature of B by the current 
 from F. This provision is sometimes required to preclude the 
 possibility of D's not working properly with its lever. Such an 
 arrangement does not interfere with keeping both home and dis- 
 tant signals in their proper relation, or their normal indications, 
 providing the levers are manipulated in proper sequence. 
 
 Fig. 170 combines the simple interlocking of the lever of the 
 above case with an indicator and magnetic controller, the signals 
 being in the clear position. C is in the latter position, due to its 
 electromagnet being deenergized, a condition occurring when 
 B is open. Thus C operates in unison with the distant signal, 
 and if B is closed, will be in the caution position. The move- 
 ment of the armature of C, beside setting the miniature signal, 
 
 FIG. 170 
 
 connects the electric lock, A, in shunt with its magnet, thus ener- 
 gizing the former and releasing the lever. This release is usually 
 effected on the latch of the lever which must be loose before the 
 latter can be moved over its quadrant. Not only is less energy 
 required to move the locking member in this case, but the liability 
 to stick is also much less. The purpose of the above arrangement 
 is to set the signals hi their normal position, and still require 
 that the distant signal be at caution before a route can be altered. 
 A circuit arrangement for the switch lock of an outlying 
 switch controlled from the signal cabin is shown in Fig. 171. 
 The operator's hand switch, C, is a two-point arrangement, the 
 left-hand contact of which is connected to the relay, Z), and in 
 series with the contact, G, at the switch, B. S is a mechanically 
 operated home signal having the circuit controller or commutator, 
 F, the latter being in series with the switch-lock magnet and 
 relay, H, so that when S is cleared H is deenergized, and con- 
 
176 
 
 AUTOMATIC BLOCK SIGNALS 
 
 sequently locks B. H also has an armature and contacts, 7, 
 while M is a push-button, or switch, at B; L is a bell, connected 
 to one side of the main battery, the latter being also connected 
 to the common line-wire. 
 
 If a freight train at the siding, B, desires to move to the main 
 line, the conductor presses the button, M, which causes L to ring 
 in the cabin. If the operator can allow the switch to be thrown 
 open, he moves the hand switch lever to the right-hand contact. 
 If F be closed, a current will pass from the main battery over 
 the common line-wire to H, F, E, and (7, thus energizing H 
 and releasing the lock. A train cannot now pass in the direc- 
 tion of the arrow, since the semaphore at S is at danger. 
 
 M- 
 
 1 I 
 
 line 
 
 FIG. 171 
 
 Also, if the lock, 7), were energized, its armature, E, would be 
 raised, thus opening the circuit and preventing H from being 
 energized. The train could not proceed from B if S were at 
 clear, as F would be opened. 
 
 Should a train desire to proceed from the siding, A, to the 
 main line, the reverse operations occur, the hand switch lever 
 being moved to the left-hand contact. A current then passes 
 through D, raising its armature and releasing the switch lock. 
 C must now be closed and H deenergized, so that the armature, 
 7, will close the circuit. This cannot occur if the switch at B is 
 open, or H is energized. 7), however, may control a signal, so 
 that a train movement on the main track can be allowed only 
 when it is energized ; that is, C must be in the left-hand 
 position. 
 
ELECTRIC LOCKING 
 
 177 
 
 In Fig. 172 a control circuit, such as is used in connection with 
 a train staff on a single-track line with sidings, is shown. The 
 main line is connected to a siding by the switch, 1. From the 
 block tower, 9, the home signals, 2 and 22, are operated, 11 being 
 a circuit breaker operated by the semaphore of 2, while 17 is 
 operated by the insertion of a train staff; and when the latter is 
 closed, relay 19 is energized. 
 
 The removal of the staff opens this circuit, but the relay 
 remains energized, since a current flows through it by reason 
 of the armature, 18, of the 4-ohm track-relay, 23, being up. 
 This also closes the slot circuit, causing a current to pass through 
 
 FIG. 172 
 
 the coils of a slot or lock magnet, 3, whose armature, 4, .controls 
 the movement of the main line signal, 2, which must be cleared 
 in order to allow a train to proceed in the direction of the 
 arrow. When 22 has been cleared, which will occur when the 
 switch, 1, has been opened, a staff is inserted and therefore the 
 circuit closer, 7, operated. 
 
 When this signal is cleared, the circuit through the lock 
 magnet, 13, is broken at 11, which allows the locking function, 
 14, to fall, the latter locking the switch rod in place. The 
 switch cannot therefore be opened until a train has passed 
 over the insulated section to which the 4-ohm relay is connected. 
 The engineman of a train passing into the protected section 
 
178 AUTOMATIC BLOCK SIGNALS 
 
 removes the staff at 7, thus opening this circuit and causing 2 
 to pass to the danger position. The track being short-circuited, 
 the 5-ohm relay, 19, is deenergized, and the 9-ohm relay, 10, 
 energized. After the entire train has passed over the track 
 section across which a difference of potential is maintained 
 by the battery, 8, the 4-ohm relay is again active, which allows 
 the switch to be thrown to its normal position. 
 
 The signal, 6, may be a distant signal, or one showing the 
 condition of the main line for trains taking the siding. 15 and 
 5 are slot batteries, and the armature, 18, has a lower contact, 
 21, which is in series with 12 and 10. 16 is a hand switch pro- 
 vided to unlock 13 through battery 15, in case it becomes 
 necessary to move a train in one direction before another can 
 proceed to that point. 
 
 Detector bars may sometimes be replaced by short insulated 
 track sections introduced at the switch to be governed, electric 
 locking being also provided. In electrical power interlocking, 
 special track relays having contacts capable of carrying and 
 breaking heavy currents are necessary. These have non- 
 fusing carbon contacts of great area, a wide break being inter- 
 posed when the relay operates, in some cases requiring also a 
 magnetic blow-out. The locking-circuits are usually independ- 
 ent of the power circuits control in such cases; but their appli- 
 cation need not be entered into here. 
 
CHAPTER XIV. 
 ALL-ELECTRIC INTERLOCKING. 
 
 NUMEROUS types of interlocking are in use, in which the 
 operative agencies are either partly mechanical, or mechanical 
 with electrical control. The General Railway Signal Co., how- 
 ever, manufacture apparatus in which both working and control 
 functions are electrical, a mechanical interlocking frame being 
 used as an auxiliary to the levers. An early form of this 
 apparatus (known as the Taylor) will first be described. 
 
 In Fig. 173 the connections at a double route signal, 37, 
 having two home blades, one of which protects the main track 
 and the other a diverging track, 44, are shown. A derail, 28, is 
 also in the block of 37, and is operated by a motor, 12. This 
 diagram is completed by Fig. 174, which represents the con- 
 nections at the interlocking cabin pertaining particularly to 37. 
 The motor, 49, operates 44; 28 is thrown by 12, while both arms 
 of 37 are cleared by 31. The line wires, 1, 2, 3, 4, 5, 6, 7, 8, and 
 9, pass to the interlocking machine, 45 and 38 running to the 
 distant signal protecting the home block of 37. 
 
 The motor, 31-32, operates either of the home semaphores, 
 according to which selector magnet, 29 or 30, is energized. A 
 circuit controller, 33, is hi circuit with the motor, 31, and the 
 brake magnet, 26. The contacts, 46, are in series with the wire 
 feeding, 31 and 26, and are provided so that a clear signal will 
 not be given when the derail is open. Should the derail be in 
 the opposite or safe position, these contacts will be closed. 
 Such a precaution is necessary in high-speed train movements, 
 as an open derail would cause a wreck. 
 
 The track is energized by the battery, 27, the relay being 
 omitted. The rotation of 12, and consequently the throwing 
 of 28, moves the pole changer, 18, the function of which will 
 be shown later. At 44, the motor, 48-49, is also connected to 
 a pole changer operated by the switch movement. Contacts 
 11 are controlled by 44, being closed when the latter is open, 
 
 179 
 
180 
 
 AUTOMATIC BLOCK SIGNALS 
 
 while the contacts, 10, are at the same time open. 10 is in series 
 with 30, and 11 in series with 29, so that when one semaphore 
 at signal 37 is cleared, the other cannot be, since but one route 
 at a time can be set up. 
 
 I.Z.3.f:5.6?89. 
 
 FIG. 173 
 
 In Fig. 174 the connections at the cabin are shown. B is a 
 60-volt storage battery; 115, 116, 117, and 118 are track relays, 
 having contact armatures, 133 to 136, for carrying heavy cur- 
 rents; 119 to 122 are latch-releasing magnets, which when ener- 
 
ALL-ELECTRIC INTERLOCKING 
 
 181 
 
182 AUTOMATIC BLOCK SIGNALS 
 
 gized permit the levers (bars with handles, having a horizontal 
 movement) to which they are connected to be moved; 123 to 132 
 are indication magnets, which give an indication of switch or sig- 
 nal movements; while the row of switches in the lower part of the 
 figure are pole changers and connectors actuated by the levers 
 themselves when the latter are thrown. The wires, 79, pass to 
 the ends of the sections in which the track relays are introduced ; 
 the lines, 1 to 14 (only 1 to 9 are relevant to this description), 
 run to the arrangement given in the preceding figure, and have 
 the same significance; 80 and 83 pass to preceding switches, 
 while 81 and 82 are signal wires. 84 is a common wire connect- 
 ing one side of the battery, all the electromagnets, and several 
 of the line wires. There are 10 lever (the levers themselves 
 being omitted) circuits; they being distinguished by the fact 
 that each has an indication magnet; signal levers opening one 
 contact and closing another, while the switch levers open two 
 circuits and close two during movement. 
 
 The armatures, 153 and 136, also 133 and 134, are in series, 
 so that should either fall the circuit will be opened. Lines 7 
 and 10 are connected to 84; while 11 is a battery line in series 
 with 135 and 136; 12 and 13 being switch lines and 14 a signal 
 line. In tracing up a lever's circuit, it should be remembered 
 that the order is changed after a rail switch or signal has been 
 thrown, by reason of the electric switches thus opened or closed, 
 and that single switches are for signal, and double switches for 
 switch movement. 
 
 Consider, for instance, signal lever 123. (The levers are sup- 
 posed to have the same numbers as the indication magnets.) 
 When the lever is " thrown " 137 will be disconnected from 138, 
 and 123 therefore deenergized. Immediately after, 138 will be 
 connected to 139, and a current flow from B to line 80, and the 
 signal (provided conditions are safe) at the latter. 
 
 Considering switch lever 131 : When the switch is closed by 
 the lever a current flows from B through 134 and 133-72 and 
 71-line wire 9- to Fig. 173-25 and 23-49-22-21-24-48-line 7- 
 Fig. 174- common wire 84, and back to B. Since 48-49 begins 
 its rotation, the switch is thrown and the current reverser 20-25 
 is operated, so that the next time 131 is thrown the motor arma- 
 ture will revolve in the opposite direction, and consequently 
 moves the switch back to its former position. The current will 
 
ALL-ELECTRIC INTERLOCKING 183 
 
 then pass through line 8 instead of 7. The switch movement 
 cannot occur unless 115 and 116 are both energized, which 
 requires of course a clear track and the absence of conflicting 
 routes. Relay 116 is connected to track battery 27 through 
 the rails of the track between 37 and the next signal, while 115 
 is connected to the side route extending beyond switch 44. 
 Hence when either 115 or 116 is deenergized, 44 cannot be 
 thrown. 
 
 The reverse and normal currents to switch 44 are through the 
 contacts, 133 and 134, as train movement over this switch may 
 take place in either position, since it joins two routes. The 
 reverse current is not required through the relay contacts in 
 case of a derail, as a train does not move over such a switch 
 when normal; and sometimes it is necessary to reverse it when 
 the block is occupied, that is, when the track relay is deenergized. 
 
 Lever 127 is for switch 28, and levers 132 and 128 are for 30 
 and 29 respectively of the semaphores at signal 37. Tracing up 
 the connections for 127, we have, considering that this lever has 
 been pulled outward (and consequently contacts 52 and 53, 
 55 and 56 separated; with 53 connected to 54, and 56 to 57), 
 5-101-54-53-line 4-Fig. 173-17- 19-12-18-16-15-13-line 6- 
 Fig. 174-140-124-84-5. By reason of the movement of the 
 switch, by the rotation of 12, the polarity changer, 18-19, is 
 reversed, so that 18 and 19 are disconnected from 16 and 17 and 
 connected to 14 and 15. This closes the indication circuit and 
 causes a current to flow from the switch motor, 12, through 18- 
 14-line 3-56-57-120-84-line 6 -Fig. 173-13-15-18. Thus 120 
 is energized, the lever latch is released and the latter can com- 
 plete its stroke. This releases the lever of 30 (132) so that the 
 lower semaphore of 37 can be cleared. When 132 is reversed, 
 77 is disconnected from 76 and connected to 78. A circuit is 
 thus closed including 5-101-78-77-line 1-Fig. 173-line 1-con- 
 tacts 11, (which are under the control of 44 )-29-3 1-32-34-33- 
 3^46-13-line 6-Fig. 174-140-124-84-5. 
 
 The clearing of the semaphore connected to 29 moves 33 in 
 a downward direction and thus shunts the above circuit with 
 the brake magnet, 26. As long as 132 is reversed, the upper 
 semaphore of 37 will be at clear, while the connecting of 35 with 
 36 clears the distant signal preceding 37. Should 132 be 
 returned to its normal position, 77 will be in contact with 76, as 
 
184 AUTOMATIC BLOCK SIGNALS 
 
 in the figure. When the signal is returning to danger, 33 again 
 connects 34 and 36, thus closing the circuit through the motor 
 31-32, and the indication magnet, 132, of Fig. 174. 
 
 The effect of gravity is to give the armature, 31, a rapid rate of 
 revolution, which sets up a counter current and dampens the 
 fall of the blade. This current passes momentarily through 
 the brake magnet, 26, which in addition to the retardation of 
 the motor armature, prevents injury to the moving system 
 from inertia. The energization of 132 also releases the lever 
 latch and allows the lever to complete its movement, which 
 could not occur did this release current not flow. 
 
 It will be noted that the indication furnishes to the operator 
 the right to complete the lever stroke, since it occurs after 
 the lever has started. This is similar in function to that of 
 other schemes of power interlocking, the indication showing 
 that the switch has completed its movement. This indication 
 is used only on the switch levers, as will be noted in Fig. 174, 
 there being but four such indication magnets. 
 
 A later development of the above circuit arrangements is 
 shown in Fig. 175, in which the track circuits (which may be 
 either polarized or neutral) are not considered. In defining 
 the functions and their relativity, the previous figures will 
 not be considered, although an extension of the principle to 
 a more elaborate though concentrated and isolated case is the 
 object in view. Two sets of interconnected (by eight lines or 
 wires in underground conduits) circuits are shown: first, those 
 at the interlocking cabin; and second, those at a distant signal, 
 1, a high home signal, 2 (protecting two separate routes), a 
 switch movement, 3, and a dwarf signal, 4 (the single sema- 
 phore home signal, 5, being for movements in the opposite direc- 
 tion, and its circuits therefore not shown). 
 
 The tappet bars are given a vertical movement by the levers; 
 cross locking being effected by the dogs, d, which are affixed 
 to sliding horizontal bars, and the recesses, b, cut in the tappet 
 bars. If a dog engages with a recess, and the former is immov- 
 able, it is evident that the lever to which this locked tappet 
 bar belongs cannot be moved. In the figure, levers 1, 2, and 
 4 are immovable; that is, they are mechanically locked in 
 position. Lever 3 is movable, however, since it is not engaged 
 by any dog, and if it be pulled outward, its tappet bar will 
 
ALL-ELECTRIC INTERLOCKING 
 
 185 
 
 nn* , rh , 
 
 ^=B^ 
 
186 AUTOMATIC BLOCK SIGNALS 
 
 rise, thus unlocking levers 1, 2, and 4, since their dogs are now 
 released by the action of the recesses. The levers operate 
 the signals and switch of the same numbers, hence the latter 
 are locked in the same fashion. It is thus evident that switch 
 3 must be thrown before the signals can be cleared, this sequence 
 being manifestly required. 
 
 The cam slot in the lever transmits an intermittent motion 
 .to the corresponding tappet bar, which is for the purpose of 
 preparing for a change in the circuits to which the lever is 
 mechanically connected. The circuit controller consists of 
 stationary and movable contact pieces, whose relation, though 
 not their actual construction, is as shown. 
 
 The dwarf signal lever (4) and the switch lever (3) have 
 each eight stationary contacts; the two remaining levers having 
 but four, the reasons for which will appear later. The first 
 half of the outward movement of levers 1, 2, and 3 produces 
 no change in the connections, since the movable contacts engage 
 the same brushes, and constitute the preliminary locking move- 
 ment for the conflicting routes affecting this lever. 
 
 The central part of the lever stroke moves the contact pieces 
 to the sets of brushes on the opposite side the tappet bar 
 being stationary. The further motion of the lever is opposed 
 by the latch, L (or L 1 , L 2 , etc.), which can only be released by 
 the energization of the indication magnet, 7, which will allow 
 of its travel being continued until the end of the stroke is 
 reached. This final movement further raises the tappet bar, 
 releasing the dogs and bars controlling conflicting routes, and 
 preserving the connections obtaining at the beginning of the 
 last half of the stroke. The switch movement will first be 
 considered. 
 
 To the main common line the indicator common, all the 
 signals, and the switch movement are connected, either directly 
 or through a circuit-breaker contact. The switch movement 
 is controlled by two other wires, through which the indication 
 current passes, with the indicator common. The control wire 
 in the normal position is, in the reverse position, the indicator 
 wire, both being used at a time. These two wires are connected 
 to opposite brushes of the circuit controller, so that reversal 
 of polarity can be effected by straight motion of the controller 
 rod from the lever. In the position shown (which is normal) 
 
ALL-ELECTRIC INTERLOCKING 187 
 
 the indicator wire is connected to the indication common 
 through the indication magnet, I 3 , and the indication bus-bar, 
 while the control wire is connected to the positive side of the 
 battery through the safety magnet, S, and the operating bus- 
 bar. In the reverse position these connections are reversed, 
 as above stated. 
 
 Additional control of the switch movement is effected by 
 the polarity changing arrangement, P, which is operated by 
 the switch-lock bolt after it has passed through the lock rod and 
 adjacent plates. This pole changer has eight fixed contacts 
 and two movable contact plates. Each of the motor armature 
 terminals is connected to two of these fixed contacts, each con- 
 trol wire to one, and one of the field terminals to the remaining 
 two, the other field terminal being joined to the main common. 
 This connection arrangement, through the action of the other 
 movable contacts, connects in the one case (that shown, or 
 normal) A to the indicator wire and b to the field, F 3 ; and in 
 the reverse position, A to the field and 6 to the reverse indicator 
 wire. In the former position, also, the pole-changing switch is 
 disconnected from the normal control; no current flowing, 
 although this control is connected to the battery. Reversal 
 of the switch lever, however, will connect the reverse control 
 wire with the battery, a current flowing through the following 
 circuit: 
 
 Battery- K-operating bus-safety magnet, /S-circuit controller 
 contacts, 6 and 8-reverse control wire-contacts 16 and 15-A 3 - 
 contacts 11 and 12-jP 3 -main common-battery. When the 
 switch has completed its movement and is locked in position, 
 the lock rod throws the pole changer, so that contact 9 is con- 
 nected to 10, and 13 to 14. The reverse control wire is thus dis- 
 connected from the armature, 6, and connected to the reverse 
 indication wire, while a is connected to the field coils; the rea- 
 sons for which will appear shortly. 
 
 The safety magnet, S, and the indication magnet, 7 3 , both have 
 their poles facing, and capable of acting upon the armature, T\ 
 this armature normally resting upon the poles of the safety mag- 
 net, which is in series with the battery and both control wires; 
 the one in circuit depending upon the positions of P and the 
 switch lever circuit controller. Should a break occur in any of 
 these wires or in the safety magnet, coils S will not be energized. 
 
188 AUTOMATIC BLOCK SIGNALS 
 
 If a cross or short circuit occurs between the control wires, the 
 total current, both that passing to the switch motor, and that 
 through the indication magnet, will pass around S, so that 
 should all the current pass through the indication magnet on 
 return, it will not exceed the current in the former; hence the 
 armature will be held by S, and the indication cannot be given. 
 As the armature normally rests upon the poles of S, in which 
 case the air-gap is zero, and the magnetic reluctance low, 
 this probability is further increased. Thus it is practically 
 impossible for a cross to set up a false indication. 
 
 A motor when operating sets up a counter electro-motive 
 force which opposes that of the operating current. If the latter 
 be suddenly cut off and the armature immediately connected to 
 an independent circuit, a current will flow in the latter (its 
 strength determined by the counter e.m.f. and total resistance 
 in the circuit) in the opposite sense to that of the driving cur- 
 rent; and will be maintained by the inertia of the armature and 
 mechanically connected parts. This is precisely the effect which 
 is utilized to give an indication through 7 3 , the proper connec- 
 tions being effected by the pole changer. The circuit thus 
 formed for the indication current is: terminal a-F 3 -mam com- 
 mon-indicator common-magnetic cut-out, ^-switch J-indi- 
 Cation bus-/ 3 -circuit controller contacts 4 and 2-reverse 
 indication linepole changer contacts 10 and 9-armature ter- 
 minal 6. The current thus flows in the same direction as before 
 through the field, hence its magnetic flux is unaltered, while 
 the indication magnet releases the switch lever by reason of the 
 following : 
 
 Normally, the latch, L 3 , is held in the position shown by the 
 dog, P 3 , and prevents full outward movement of the lever by 
 the engaging of projection Q 3 with the projection on the right- 
 hand end of L 3 . When P is energized, however, T 3 is moved 
 upward, and its rod strikes dog P 3 so that L 3 is released and 
 allowed to drop, permitting the completion of the lever stroke. 
 (It should be remembered that the travel of the lever has already 
 been traced to its middle position.) Hence the indication cur- 
 rent cannot be set up before the motor-operating current has 
 been cut off, the indication wire connected to one side of the ar- 
 mature, and the connections between armature and field re- 
 versed. The cessation of operating current might be produced 
 
ALL-ELECTRIC INTERLOCKING 189 
 
 by a broken conductor, which is a highly improbable condition, 
 while crosses are guarded against by S. 
 
 The magnets, M and M' , are in series and connected to the 
 indicator and control line- wires, their junction being also in 
 connection with one terminal of F* and consequently the main 
 common. By means of these magnets, the movement of P is 
 under the control of lever 3, at such times as it is not operated 
 automatically by the lock rod. When the battery is connected 
 to the normal control wire, current energizes M\ but when the 
 reverse control wire is in connection with the battery, M' is 
 energized. These currents shift the pole-changer mechanism hi 
 the direction of the magnet through which the current circulates, 
 hence movement can be effected at any time during the switch- 
 and lock-rod-movement, except at the very beginning and end- 
 ing of the latter. If the lever is used to reverse the switch, 
 current passes through the motor and through M f \ this current 
 so holds the pole changer that the operating current will be 
 maintained. Should it be desirable to throw the switch normal 
 before this reverse movement has been completed (which con- 
 tingency might arise from snow, ice, or other obstruction between 
 the main and point rails), the lever is merely pulled back to the 
 normal position, thus energizing M through the normal control 
 wire and throwing the switch back. This is effected by M 
 shifting P to its former position, sending current through the 
 motor in the proper sense by way of the normal control wire; 
 the pole changer being again shifted to the position shown, thus 
 setting up the indication current. When M shifts P, current 
 does not pass through I 3 , since the lever controller is not in the 
 proper relation with the pole changer, and current is not set up 
 if the magnet refuses to operate, on account of the reversed 
 armature connections. A circuit-breaking device is in series 
 with M and M', so that when the switch has fully moved and is 
 locked in either position, the current is cut off from these mag- 
 nets. This does not alter the rest of the diagram, however. 
 
 When the lever, 3, is moved to the normal position, the battery 
 is connected to the normal control wire through S, thus sending 
 a current through the switch motor, which starts at a and 
 returns to b, in the opposite sense to that used in reversing 
 the switch, the field current maintaining its proper course. 
 The armature thus revolves in the opposite direction, the switch 
 
190 AUTOMATIC BLOCK SIGNALS 
 
 rails being thereby thrown normal, and at the completion of 
 this movement, P is shifted to the position shown in the dia- 
 gram, the indication current being thereby set up. Terminal b 
 is thus open-circuited, while a is put in series with the normal 
 indication wire, which at first was the reverse control line. 
 
 The switchbox contains a pole-changing device which con- 
 trols the motor of the two-home-arm high signal, 2. When the 
 motor revolves in one direction, one of the semaphores is cleared, 
 and when in the other direction, the remaining blade. This 
 switch thus acts selectively, the semaphore being connected 
 by a chain to opposite sides of a sheave wheel driven by the 
 motor through reduction gearing. Hence, when one sema- 
 phore is cleared, the other must be at danger, gravity producing 
 this latter condition through the medium of counterweighted 
 levers, which are mechanically connected to the blades. 
 
 Each semaphore operates a circuit breaker, the upper arm 
 having two sets of contacts, and the lower one set. One of 
 the former closes the circuit of the distant signal, 1, the lower 
 arm not having a distant function. The lever, 2, which con- 
 trols this home signal, operates a controller having one reverse 
 and one normal pair of fixed contacts, but one movable piece 
 being used. Only one line wire, the control and indication, 
 passes to 2, and is in series with 7 2 and the lower set of fixed 
 contacts. One of the upper contacts is connected to the indi- 
 cating bus, and the other to the operating bus. When lever 
 2 is reversed, the positive side of the battery will be connected 
 to P and the control line, a current flowing through the cir- 
 cuit including 7 2 -control \me-G 2 -G-F 2 -switchbox-a 2 -A 2 -b 2 - 
 switchbox-main common-battery. If the switchbox is in its 
 normal condition, the upper arm at 2 will be cleared. Upon 
 the completion of the movement to clear, G 2 opens the home 
 circuit and closes the distant circuit, the motor-brake magnet, 
 B 2 j being in shunt across this break, this magnet having a 
 comparatively high resistance and bringing the motor arma- 
 ture to a stop, holding the signal at clear as long as lever 2 is 
 in this reverse position. 
 
 As P is energized, L 2 releases the lever, so that the full 
 movement to the reverse position can be made. This energi- 
 zation does not constitute an indication, as such is not required, 
 since locking is not released. The movement of the distant 
 
ALL-ELECTRIC INTERLOCKING 191 
 
 signal, 1, to the clear position is the only indication required of 
 the proper clearing of this upper blade, this being accomplished 
 by the interposed circuit-breaker. When lever 2 is pushed 
 back to^ normal, the brake-magnet circuit is broken, and the 
 indication magnet connected to indication common and the 
 control line. Hence the brake mechanism is released, the blade 
 returning to normal by the action of gravity on the counter- 
 weight. This sets the train of gears and motor armature into 
 rotation, developing a counter e.m.f., the circuit-breaker, G 2 , also 
 closing the indication circuit in its upper position. This circuit 
 includes A 2 -b 2 switchbox-main common -indication common- 
 #-J-indication bus-! 2 -control line-(r 2 -(;r-.F 2 -switchbox- and a 2 . 
 The latch, L 3 , is thus released, so that the final part of the 
 stroke of the lever, 3, can be made. The energy expended 
 in this releasing circuit retards the moving armature and pre- 
 vents a blow being delivered by the moving parts. 
 
 If the switchbox switch is reversed when lever 2 has been re- 
 versed, the current will pass through the armature from 6 2 to a 2 , 
 in the opposite direction to that above shown. This, therefore, 
 causes the armature to revolve in the opposite direction, thus 
 clearing the lower arm, the indication current being developed 
 in the same manner as above described, the brake magnet, B 2 , 
 being put in circuit by the action of (7, with which it will be 
 in shunt. The indication current is also in the opposite direc- 
 tion in the armature and switchbox. 
 
 The dwarf signal, 4, is not thrown to clear through the aid' 
 of a motor, but directly by the movable magnetic circuit of a 
 heavy solenoid. This solenoid has two distinct windings, 
 represented in the diagram by R and W. R is the retaining 
 coil, and is of high resistance, holding the small semaphore at 
 clear, while W is the working or clearing coil, and of compara- 
 tively low resistance. The indication current is taken directly 
 from the working battery by way of the signal's lever, 4, 
 instead of utilizing the counter e.m.f. of a motor, it serving 
 equally well. The circuit controller has eight stationary and 
 two movable contacts as before; four of these fixed contacts 
 being shorter, however, so that the movable pieces will not 
 dwell upon the former more than a predetermined time. 
 
 A normally fixed connection exists between the indication 
 magnet and the positive side of the battery, the indication line 
 
192 AUTOMATIC BLOCK SIGNALS 
 
 being connected to but one of the short fixed contacts. The 
 indication line is connected to a circuit-breaker, Z), at the dwarf 
 signal, another circuit-breaker, G 4 , being in series with the working 
 coil. The latter is closed only when the signal lever is reversed, 
 while D is closed only when the signal is normal. When the lever 
 is at the normal indication position, the control line is connected 
 to the indication bus, and the other end of the indication magnet 
 to the indication wire. At the reverse indication position 
 (when the movable contacts are in the dotted line denoting the 
 reverse indication and control points) the positive side of the 
 battery is in connection with the control wire, the indication 
 magnet being in series with the indicator and main common 
 lines, and the negative side of the battery. 
 
 At the full normal and reverse point, the indication magnet is 
 open-circuited, and the control wire is connected in a manner 
 similar to the indication and control positions. When lever 4 
 is reversed, current flows through the control wire to W, to the 
 main common battery, and circuit-breaker, G 4 , thus clearing the 
 semaphore; G 4 then opening, cutting in R (and W, which is in 
 series with it, although now having but little magnetizing effect) 
 which retains the blade in the clear position. The clearing cur- 
 rent is about 6 amperes, and tho retaining current .25 ampere. 
 
 The indication current, which is sent through the indication 
 magnet when the lever has reached the normal indication posi- 
 tion, is not set up for any other purpose than to release the lever 
 and allow the full reverse movement to be made, as in the case 
 of the high signal, the reason for this being that an interlocking 
 function is not to be released. When the lever is moved back to 
 normal, R is open-circuited, and the blade moves to danger, thus 
 closing the circuit-breaker, D, and connecting the main common 
 line to the indication line. A latch releasing current then flows 
 through 7 4 , because the latter has been connected to the indica- 
 tion line by the movement of the lever to normal. 
 
 The indication common is not connected to the main common 
 at the cabin; but is run out to a point where the effects of voltage 
 drop in the main common, due to the heavy current taken by 
 the motors, etc., will be at a minimum. Should this line be near 
 the battery, the drop in potential would have a tendency to 
 cause a current flow back over the indication lines of the 
 levers not being operated, and might open the safety cut-out 
 
ALL-ELECTRIC INTERLOCKING 193 
 
 (to be described) when not required, resulting in considerable 
 annoyance. 
 
 This cut-out is provided to eliminate the evil effects resulting 
 from crosses between any of the various wires. J and K are 
 two switches connected respectively to the indication and opera- 
 ting buses, being normally held open by a spring, and closed by 
 current in the coil, C. When K is open, it cuts the battery off 
 from all functions, while J opens all of the indication circuits. 
 Coil C, which is of high resistance, is connected across the battery 
 through the main and indication common lines. H is a low- 
 resistance coil, wound differentially with respect to C, so that 
 the greater the current in H in a given direction, the greater the 
 opposition to the flux of C, and consequently the less the pull on 
 the armature. H is in series with the indication common, so 
 that all indication currents must pass through it, these currents 
 moving in the direction of the arrows, and assisting C to main- 
 tain the contacts at K and J closed. Any current flowing from 
 the positive side of the battery through H, due to a cross, will 
 pass in the opposite direction to the arrows, and consequently 
 tend to neutralize the flux set up by C, and open the cut-out, as 
 the indication common, to which H is permanently connected, 
 is on the negative side of the battery. All wires connected to 
 the interlocking machine which are functionally operative are 
 connected to the negative battery terminal through the indica- 
 tion bus, J, H, indication, and main common; hence, current 
 passing from any line-wire to these will set up a current which 
 produces a flux in opposition to C and thus opens K and J. H 
 has a low resistance, hence the greatest percentage of the current 
 resulting from a cross will flow through it, and if this current be 
 of sufficient strength to cause rotation of a motor armature, it 
 will certainly open the cut-out. 
 
 In Fig 176 a portion of a standard all-electric interlocking 
 machine is shown. A rear view, showing the fuse and terminal 
 board, is at 1 ; 2 is a typical section, and 3 a partial front view 
 of the locking. Besides a supporting frame, there is a terminal 
 board, A, the controllers, C, levers D, lever guides E, locking G, 
 case H, and indication and safety magnets, / and S. The case 
 is provided with glass doors, for ready inspection and repairs, 
 and the fuse board contains all fuses, buses, terminal posts and 
 connections. The upper bus is the switch operating, the lower 
 
194 
 
 AUTOMATIC BLOCK SIGNALS 
 
 the signal operating, and the central is the common indication 
 bus. B is an indication selector, which is used only on switch 
 
 levers, consisting of electromagnets operated by the working 
 current, moving an armature in one direction when the switch 
 
ALL-ELECTRIC INTERLOCKING 
 
 195 
 
 lever is normal, and in the other direction when at reverse. It 
 closes the indication circuit corresponding to the lever position, 
 leaving the other open. 
 
 In Fig. 177 the appurtenances directly common to the levers 
 and their relation are shown. A shows a lever entirely in, and 
 B the same four-fifths out. D is held in the guides, E, by the 
 bars, F, and is provided with a slot, U, which imparts variable 
 
196 AUTOMATIC BLOCK SIGNALS 
 
 motion to the tappet bar, 7, the respective positions being 
 numbered 1 to 5. The moving contact block, Z, receives motion 
 from D by the rod, W . I and S are the indication and safety 
 magnets respectively, and impart motion to rod R through the 
 armature, T. X and Y are stationary contacts connected 
 to the various functions, as shown in the diagram, Fig. 175. 
 R engages with P, which is held down by the spring, 0, the 
 latter also acting against the pivoted latch, L. 
 
 The raising of the tappet bar, by the movement from 1 to 2, 
 locks all the conflicting levers, the projection, M, then striking K, 
 and tilting the latch, L, to a nearly horizontal position, causing J 
 to be struck by Q, thus retaining the lever. When moving 
 from 2 to 3, Q also meshes with the teeth on N, thus causing the 
 latter to rock about its axis, and by throwing dog P into engage- 
 ment with L, locking the latter, as at B. From 3 to 4, N con- 
 tinues its revolution, being stopped by Q striking J. Here 
 an indication current passes through 7, releasing L by rea- 
 son of R striking P, allowing the motion from 4 to 5 to take 
 place, thus unlocking the unconflicting levers by the upward 
 motion of V. Hence, D will be immovable when conflicting 
 routes are set up, and cannot move from 4 to 5 without an 
 indication; while if it is moved to or beyond 3 it cannot pass 
 4 nor return to 1 without an indication, which will not occur 
 unless the function controlled is locked in the position corre- 
 sponding to that of the lever. 
 
 The switch and lock movement for a left-hand slip switch is 
 shown in Fig. 178, and consists of the motor, A, and connecting 
 shaft B, pole-changer C, gear frame F, driving rod G, lock 
 movement H, and cover L. The motor is of enclosed and 
 weatherproof construction, and operates the entire arrange- 
 ment. The gear mechanism, F, reduces the speed of the motor 
 armature for the required slow movement of the detector bar 
 and switch, and disengages the motor after the full switch 
 movement has taken place. This latter is effected by the cam, 
 D, which is on the same shaft as the main gea,r, by the clutch 
 shifter, V (which allows the shaft to revolve without affecting 
 the pinion), and by toothed clutches, not detailed. Unless 
 the pinion engages with one of the clutches, it is loose on the 
 shaft, so that when the stroke is completed the clutch is moved 
 transversely by a shifting-cam on the main gear, after which 
 
ALL-ELECTRIC INTERLOCKING 
 
 197 
 
 the indication is given. The main gear-pin, E, moves the lock 
 plunger, detector bar, and switch, through the rod, G, and crank 
 cam, D. The lock movement, H, directly operates, the pole 
 
 changer, detector bar, U, and lock plunger. G throws R, 
 and consequently S and T } so that the switch cannot be thrown 
 if a train be passing it. C is moved through the medium of 
 
198 
 
 AUTOMATIC BLOCK SIGNALS 
 
 the pole-changer movement, I, after the lock rod, M, is held by 
 the lock plunger. The pole changer moves in one direction 
 when the switch is moved normal and in the opposite direction 
 at reverse, with results already shown diagrammatically. 
 
 The operation of the switch movement is as follows: When 
 the switch lever has been thrown, and the motor connected 
 to the battery, the armature drives the main gear through 
 
 FIG. 179 
 
 one revolution. At the first part of its revolution the lock 
 bolt is released, and the detector bar raised. The pin, E } then 
 strikes the outer end of the pivoted cam, D, thus throwing 
 the switch, this taking approximately one-third of a revolution. 
 The remaining third of the revolution results in the lowering 
 of the detector bar, and setting of the lock bolt, the pole changer 
 being thrown as soon as the plunger passes through the lock 
 rod, the motor disengaged, and the indication given. 
 
ALL-ELECTRIC INTERLOCKING 
 
 199 
 
 The reversible pole-changer mechanism, shown in outline 
 and connection at the switch machine and designated by P 
 in the diagram, is illustrated in plan and elevation in Fig. 179. 
 Rod W is connected mechanically to the lock bolt, and operates 
 the movable contacts, which engage the fixed contact-fingers 
 N. V is a control drum, acting as a circuit- breaker, which is 
 operated by the shaft (shown dotted) carrying the main gear 
 and cam so that the magnets, M, are open-circuited when the 
 switch is home and locked. The movable cores, to which the 
 moving contact blocks are secured, are under the control of 
 the magnets when the switch is to be thrown. These magnets 
 are shown at M and M f in the circuit diagram also. 
 
 A Taylor switchbox (or ground selector) is shown in Fig. 
 180. The movement of the switch rails throws the link, C, 
 
 thereby bringing the movable contact members, 5, into con- 
 nection with the row of stationary clips, D, closing the desired 
 circuits. When the switch is thrown in the other direction the 
 contact strips, A, engage with a similar row of contacts on the 
 opposite side of the box. This device is used for any appli- 
 cation of functions depending upon switch or other movement 
 for their control. 
 
 Fig. 181 shows a Taylor hook selector, suitable for fastening 
 to a signal pole and controlling a semaphore. B is the counter- 
 weighted lever, which normally has no connection with lever D. 
 The latter is keyed to the shaft, F, while B moves about F as 
 a center merely. When the electromagnet is energized, the 
 armature, E, is raised, causing hook C to be thrown directly in 
 the path of a cross piece, fastened to 5, so that movement of 
 the latter cannot occur without D being moved. Hence, 
 when B is pulled in the direction of the arrow by the motor, 
 
200 
 
 AUTOMATIC BLOCK SIGNALS 
 
 the signal will be cleared, if A is energized. When the inter- 
 locking lever for the signal is thrown, current passes through 
 the proper selector magnet, through the motor and circuit 
 
 FIG. 181 
 
 breakers. This clears the signal, the indication being given in 
 the usual manner. From two to five arms may thus be oper- 
 ated, and if ground selectors are used, but one interlocking lever 
 is required. 
 
CHAPTER XV. 
 THREE-POSITION SIGNALS. 
 
 THREE-POSITION semaphores eliminate the distant blade and 
 still give an indication of the condition of the distant block. 
 This is accomplished by using three distinct positions of the 
 semaphore: the all-clear being vertical; the caution diagonal; 
 and the stop position horizontal, or nearly so. The control 
 and operation may be effected by either line or track circuits, 
 
 to charging wire 
 
 FIG. 182 
 
 the former being first described. Considering three consecutive 
 signals, No. 3 being occupied, 1 and 3 will be controlled by the 
 track circuits in the blocks they protect, while 2 will be con- 
 trolled by line wires from 3. 
 
 Figs. 182 and 183 show the consecutive circuits employed in 
 the Grafton arrangement of such signals. Fig. 182 gives the 
 connections at the first signal considered; the semaphore, 17, 
 being operated by a motor, 19, of about .1 horse power, its posi- 
 
 201 
 
202 
 
 AUTOMATIC BLOCK SIGNALS 
 
 tion and movement being governed by the slot instrument, 18. 
 The armature contacts, 13, of the track relay, 10, are in series 
 with the cut-out, 22 (operated by the motion of the sig- 
 nal mechanism), and one side of the main or storage battery, 7, 
 the latter being located at the signal, and charged by feed wires 
 running on poles from a central generating plant, one side of 
 this battery being connected to the common line, 23. If the 
 contacts, 6, are closed, a current will pass through 18, which 
 locks the signal and holds it in the clear position shown. 
 Should 10 be deenergized, however, by reason of 16 being 
 
 FIG. 183 
 
 short-circuited by a train in the section, 18 will be released and 
 17 will return to the stop position. Circuit-breaker 4 is closed 
 when the signal is in either the stop or the caution position, but 
 is opened in the clear position; while 5 is closed only in the stop 
 position, and 6 closed in the clear and caution positions. The 
 three-position relay, 1, is in series with the line wires, and has two 
 armatures, 2 and 3; the former shunting the circuit- breakers, 
 and the latter connecting the motor to one side of the battery 
 through 4, 22, and 13. If the wires, 15 or 14 (Fig. 183), should 
 be broken it is evident that 7 would be continually passing a 
 heavy current. To guard against such an occurrence, the cir- 
 cuit opener, 22, operated by the signal mechanism, is provided. 
 
THREE-POSITION SIGNALS 
 
 203 
 
 The armatures, 11, 12, and 13, of relays 8, 9, and 10, are in series 
 with this device. 
 
 The special parts of the signal mechanism are shown in Fig. 
 184. The semaphore is connected to the rod which is fastened 
 to the sleeve, F, the accessories being secured to the latter, and 
 move with it when the semaphore is cleared. The rod, M, is 
 operated through a train of gears by the electric motor, there 
 being three stationary positions. 
 B is the slot magnet, whose 
 armature affects the position of 
 the lock block, L, through the 
 toggle arrangement, C-D-K. A 
 is a dashpot, whose piston is 
 stationary, it being required to 
 prevent spasmodic movements 
 of the moving system, and pre- 
 vent the inertia of the latter 
 from injuring the mechanism. 
 N and J are latches which engage 
 with F at its various positions 
 and relieve the motor and gearing 
 of the weight of the apparatus 
 when at rest. 
 
 When B is energized, L is 
 forced into engagement with a 
 recess upon the upper end of 
 M, so that motion of the latter 
 results in motion of the former, 
 their tendency being to disen- 
 gage. The circuit-breakers not 
 shown are operated by an ex- 
 tension of the sleeve, F, while / is the armature extension of 
 a catch magnet, which, when deenergized, prevents F from mov- 
 ing upward by the hooked end of the armature being forced 
 into the notches, 0, by the spring, H. The operation of the signal 
 should be readily perceived from the above description, a rather 
 complicated application in conjunction with semi-automatic 
 signals being now taken up. 
 
 In Figs. 185 and 186, the connections of two automatic three- 
 position signals on double track, and their relation to mechani- 
 
 / L 
 
 FIG. 184 
 
204 AUTOMATIC BLOCK SIGNALS 
 
 cal semaphores, moved by levers from a cabin at a junction, 
 are shown. Both 2 and 4 are electrically operated, but are also 
 under the control of the signalman; while 1 and 2 are entirely 
 automatic. In order to trace out the connections most expe- 
 ditiously, Figs. 182 and 183 should again be consulted. Both 
 diagrams are similarly arranged, and are connected by the line 
 wires, 1 to 7. 
 
 At 10 in Fig. 185, the circuits at signal 1 are shown, 
 the remainder of the figure being devoted to the connections of 
 2 and the interlocking functions. The circuit- breakers, 16 and 
 17, are opened when the semaphore of 1 is moving to the clear 
 position, while 18 is closed,the three-position relay, 19, controlling 
 signal 1, current being derived from the main battery, 11. Cir- 
 cuit-breakers 22, 23, and 24 are similar in function and operation 
 to those operated by 1, while 25 is in series with one of the con- 
 tacts of the circuit controller, 14. The latter is operated by the 
 lever which throws 4 of Fig. 186 to the clear position, at which 
 time the breaking device, 31, is closed. This effects a cau- 
 tionary indication through the distant line wire. 
 
 The lock magnet, 27, is for the purpose of securing the lever 
 for 4 in the stop position, unless it is energized by way of the 
 common and No. 4 line wires, through 13 and the first of the set 
 of contacts 32. When the lever of 4 is reversed, the lever relay, 
 28, is energized and acts as a controlled function; the stick relay, 
 38, through its lower armature, being interposed for accom- 
 plishing this purpose. The latter must be energized before the 
 signal can again be cleared. 
 
 In tracing up the circuits it should be remembered that 2 
 is controlled in a manner similar to 4, and that while its con- 
 nections are shown, only those of the latter are described. 
 As the latch of the lever for 4 is lifted the circuit controller, 13, 
 is shifted, so that the stick relay, 15, is connected through con- 
 tacts, 36, and the upper armature of 15 and its coils, line-wire 4, 
 and the storage battery. The lever relay, 28, has been closed 
 through the storage battery, armature 37 of the control relay, 
 35 (of signal 4), line 7, 36, lower armature of 15, line 5, lever 
 relay 33, line 3, and to the battery. When 13 is not shifted, 
 we have from the battery, 37, line 7, 36, upper armature of 
 15, 15, line 4 to battery. 
 
 As 33 is on closed circuit when the signal latch is raised, it 
 
THREE-POSITION SIGNALS 
 
 205 
 
206 
 
 AUTOMATIC BLOCK SIGNALS 
 
 performs the office of a track relay, the motor and other circuit 
 being closed by its armature, thus allowing the semaphore to 
 be cleared. With a train between 1 and 4, track relay 35 is 
 short-circuited, which open-circuits 33 and 15, thus causing 4 
 
 -a 
 
 Jl^ 
 if I 
 
 to move to the stop position. When the lever of 4 is put into 
 its normal position, 15 will be energized by reason of 36 being 
 connected to 39 (13 and 14 are supposed to move vertically). 
 It will be evident that these semi-automatic signals are thus 
 
THREE-POSITION SIGNALS 207 
 
 returned electrically to the stop position, and cleared 
 mechanically. 
 
 When 33 is energized, 4 cannot be cleared unless the block 
 ahead is clear, because of the track relay introduced; which is 
 also the case in the automatic control of signal 1. The lever 
 of 4 is locked in its stop position by the deenergization of the 
 lock magnet, 27; hence the latter must have its circuit to battery 
 closed through 39, the first left-hand set of the contacts, 32, 
 line 6, battery, and line 4. The first set of contacts at 32 will 
 not be closed, however, unless 4 is in the stop position. 
 
 Slot circuit-closers 32 are operated in a manner similar to 
 the three-position contactors that have been described. With 
 a clear track, the signalman must first clear 4 before a train can 
 enter the block. The unlatching moves 13, and simultaneously 
 31, thereby throwing the signal, by sending a current from the 
 battery through the motor circuit. The circuit closer, 31, is 
 similar to 12, while 29 and 42 are three-position relays. The 
 contractors, 30, are operated by signal 3; and 14 is a circuit con- 
 troller, similar to 13, operated by movement of 2. The respec- 
 tive signal slots are b v 6 2 , etc., the track relays, a v etc. 
 
 In Fig. 187, the connections of three consecutive G. E. three- 
 position signals, 75, 85, and 95, appear. Two line wires, 1 and 
 2, interconnect the various signals, these being in series with 
 the three-position relays, R. The contacts of the latter are 
 closed when the semaphore is in the clear and danger positions, 
 and open when in the caution position. The controller, A, is 
 an arrangement with movable sectors and stationary contacts; 
 and rotates in an opposite sense (in the diagram) to the sema- 
 phore. The lock magnet, L, holds the semaphore in position, 
 and the clutch magnet, C, in series with the motor, M , engages 
 the semaphore operating gear at its various positions of rest. 
 
 When the semaphore is at clear, 7 is connected to 8, and the 
 lock-magnet and three-position relay (at 65) are in multiple, 
 being energized by the power battery, P, at 75. The lock mag- 
 net holds the semaphore at clear, and opposes the tendency of 
 gravity to move it to the stop position. As R is energized, the 
 current to the lock magnet, L, is in series with its armature. 
 
 With the semaphore at caution, 6 and 7 and 4 and 5 are con- 
 nected. The three-position relay, R, at 85 is deenergized, since 
 the track battery, T, at 95, is short-circuited. Current thus 
 
208 
 
 AUTOMATIC BLOCK SIGNALS 
 
THREE-POSITION SIGNALS 209 
 
 passes through R (at 75) and the lock magnet in parallel, the 
 motor, M, being out of circuit at this moment. 
 
 When the semaphore is at danger, as at 95, the track relay, 0, 
 is short-circuited, thus cutting the motor out of circuit with the 
 power battery. The three-position lock and clutch magnets 
 are thereby deenergized, and the semaphore is acted upon only 
 by gravity. It should be remembered that all movements 
 toward full clear are performed by the motor, and all toward 
 danger by gravity. Thus the return from clear to caution is 
 effected by gravity under the control of the lock magnet. 
 
 In Fig. 188 a later modification of the above is shown. The 
 power battery, P, in this case is disconnected from the motor 
 circuit by a quadruple break as are also the stationary con- 
 tacts, 4 and 7, of the controller. These contacts carry the heavy 
 working current, the actual construction being shown in Fig. 190. 
 
 One form of G. E. top post, automatic, three-position signal, 
 such as is used in connection with signal bridges, is illustrated 
 hi Fig. 189. The glass spectacles are removed, the, semaphore 
 being in the caution position. The return to stop is assured (by 
 reason of a preponderance of weight on the left side) after the 
 lock magnet has released. 
 
 The internal mechanism of the top post three-position signal 
 is shown in Fig. 190, the doors of the housing being thrown 
 open. The small series-wound motor, M, drives the main gear, 
 G, which is indirectly connected to the semaphore shaft. 
 Secured to this same shaft are the contact sectors of the con- 
 troller, S, which engage with fixed clips during rotation. An 
 intermediate shaft gear and pinion exist to further decrease 
 the motor speed. D is a dashpot, whose piston rod is connected 
 to a crank, carried by the semaphore rock shaft, to prevent 
 injury to the parts when the blade returns to stop. C is the 
 lock and L the clutch magnet, whose connections were shown 
 in Fig. 187. The stationary contacts of the controller are con- 
 nected to the track-relay armatures, lock and clutch magnets, 
 battery and lines, in the order shown in the latter circuit diagram. 
 The clutch magnet operates a toggle clamp which holds the 
 semaphore in its proper position. 
 
 The lock magnet is in circuit when the blade is at clear and 
 caution, but not when in the stop position; the clutch magnet 
 being in circuit whenever the motor is, since it is in series with 
 
210 
 
 AUTOMATIC BLOCK SIGNALS 
 
THREE-POSITION SIGNALS 
 
 211 
 
 the latter. The circuit is broken by a spring action quick break, 
 so that burning of the contacts will be minimized. 
 
 A later development of the above three-position (normal clear) 
 operating structure, appears in Fig. 191. The 14-volt series 
 motor, A, drives the train of gears and pinions, C, D, E, F, 
 thereby transmitting a rotary movement to the clutch wheel, H, 
 which is free to move on the semaphore shaft, J. The inner face 
 
 FIG. 189 
 
 of this clutch gear contains a plurality of V-shaped bosses, B, 
 with which the clutch structure, K, engages, when the operating 
 magnets, M-M', are energized. These magnets, with their 
 armature and toggle levers, are mounted on a sector frame, S, 
 which is rigidly keyed to the shaft, J, and thus gives motion to 
 the semaphore, the latter being attached at Q. The motor and 
 clutch magnets, as shown in the diagram, are connected in 
 series, so that when the motor is operative, these coils are ener- 
 thus causing the toggle levers to force the working end 
 
212 AUTOMATIC BLOCK SIGNALS 
 
 into engagement with the bosses on the clutch wheel, which is 
 then revolved in the direction of the arrow by the motor, 
 thereby throwing the semaphore to the caution or clear direc- 
 tion. This locking sector, 8, mounted directly on the shaft, J, 
 is provided with bosses (not evident in the position given) 
 
 FIG. 190 
 
 which engage with, and are securely held by, the toggle levers 
 operated by the magnets, N- N', at the caution and clear posi- 
 tions. By the action of the control contacts, a, b (and four 
 others at the rear of P), and the segments, U and U', the motor 
 is thrown in and out of circuit. In the caution position N-N' 
 is energized and the lock toggles (counterweighted at 0), engage 
 with the boss on the locking sector, thus holding the semaphore 
 
THREE-POSITION SIGNALS 
 
 213 
 
 at the 45 position. With the track circuit justifying a clear 
 indication (which is normal); a similar scheme of connections 
 obtains, with the same sequence. 
 
 The contact segments, U, U f , and C7", effect the proper varia- 
 tion of interconnection with the contact fingers, a, 6, c, d, etc., 
 
 FIG. 191 
 
 and are mounted on the shaft sleeve, P (keyed to J), carrying 
 the plunger of the oil filled dashpot, DP, and insulated by the 
 moulded collars, n, n', and n". The remaining connections and 
 especially those made by the fingers and posts hidden from 
 view, are effected as in the diagram and preceding mechanism. 
 An additional adjustable control segment, U", and fingers, c and 
 
214 AUTOMATIC BLOCK SIGNALS 
 
 dj constitute an auxiliary control feature, for purposes of indica- 
 tion at a block tower or similarly appointed location. 
 
 By arranging the mechanism adjacent to the semaphore, with 
 the rock shaft of the latter driven directly by the gearing, a 
 remarkably self-contained unit is assured. This, in combina- 
 tion with the three-position arrangement, marks a step for- 
 ward in the standardization of automatic signals. The energy 
 taken by the motor is also greatly reduced, owing to the absence 
 of clumsy connections and accessories. 
 
 The three-position Hall electrorgas signal employs two cylin- 
 ders which are connected to the single signal rod by a walking 
 beam. When the home clears, the beam is lifted at one end, 
 the signal rod moving half its distance, the fulcrum being at the 
 distant cylinder. When the latter clears, the end at the home 
 cylinder is the fulcrum, the rod being thus forced to complete 
 its stroke. About three seconds are required for clearing such 
 a semaphore, a single cylinder moving its entire stroke in from 
 one to two seconds. 
 
CHAPTER XVI. 
 ELECTRIC RAILWAY SYSTEMS. 
 
 ELECTRIC railway signals have not as yet reached the 
 perfection that steam road devices approach, owing to their 
 more recent application, and the inherent difficulties obtain- 
 ing in such systems which do not have to be considered in the 
 latter case. Chief among these is the leakage current neces- 
 sarily the concomitant of a grounded system in which heavy 
 currents at high voltage are employed. This leakage is so 
 great that ordinary battery relays become useless. An advan- 
 tage, which, however, can be over-estimated, is the power 
 circuit current that can be drawn in any quantity at every 
 point on the right of way. Nearly all signals applied to electric 
 lines employ a contact device operated directly or indirectly by 
 the trolley wheel, third-rail shoe, or other part of the moving car. 
 
 On a grounded return direct-current street railway system, 
 or on a steam road which is crossed by or interconnected 
 through ground pipes or bridges with such a system, it some- 
 times becomes advantageous to use a signaling scheme which 
 will not respond to direct current. The working circuits may 
 be of direct current, this latter either obtained from batteries 
 or the power lines; but the control circuits carry only alterna- 
 ting current. Such an arrangement is represented generically in 
 Fig. 192, the circuits having two insulated components, one con- 
 taining the secondary, S, of a small transformer or converter, and 
 the other the primary coil, P. The track is connected to an 
 alternating-current supply, the special laminated magnetic circuit 
 relay, R, governing the elements for either a normal clear or a 
 normal danger system. A direct current, whether by leakage or 
 grounded connection, flowing through the primary, cannot induce 
 a current in the secondary or, consequently, operate the signal. 
 
 In the New York Subway, but one track is divided into insu- 
 lated sections, the signals, lamps, and relays being operated by 
 alternating current, these relays having vanes instead of arma- 
 
 215 
 
216 
 
 AUTOMATIC BLOCK SIGNALS 
 
 tures to close the contacts. Several other such systems have 
 been devised and applied, but not to an extent that would 
 warrant their description herein. 
 
 On an alternating-current road, the relays can be made of 
 high ohmic impedance, so that an alternating current cannot 
 set up sufficient current in the coils to lift the armature. Direct 
 current is of course used in both supply and control circuits, 
 since the opposing inductance of the relays is but momentary, 
 and manifested only when a change in current strength occurs. 
 
 Fig. 193 is a diagram showing the circuit arrangement used 
 in the Uni direct-current system. The trolley wheel, T, operates 
 a special switch, L, and closes a circuit according to the direction 
 of motion. 7 is a lightning arrester in series with the perma- 
 nent feed-wire, M . The latter is connected to a red lamp, F, 
 the locking electromagnet, A, the contacts, E, operated by B, 
 the contact, D, lightning arrester K, lighting line-wire R, and 
 to ground, through similar apparatus at N. B and C are the 
 
 to signal 
 
 alternating current \supply 
 FIG. 192 
 
 lighting magnets, since when they are energized the lamps 
 are lighted. These are alternately excited, the cores acting 
 upon a walking beam. In the position shown, the green lamp, 
 G, is energized, while in the opposite position, F will be in 
 circuit. The extinguishing line-wire, S, is in series with B, 
 through the lightning arrester, J, and the trolley switch, L, or 
 the switch contacts, 0, operated by C. H is a resistance 
 interposed in the power circuit to keep the current down to 
 the required figure. A operates the contacts, P, and locks 
 the arrangement, preventing interference. 
 
ELECTRIC RAILWAY SYSTEMS 
 
 217 
 
 When a. car enters the block, the automatic switch is struck 
 by the trolley, thus lighting the green lamp at the home end of 
 the block, at the same time lighting the red lamp at the distant 
 end; the latter being in series with the former. When the car 
 reaches the trolley switch at the leaving or distant end of the 
 block, both lamps are extinguished. The block is thus unoccu- 
 pied when both lamps are out, and occupied when either red 
 lamp is in circuit. Since the arrangement is double acting, 
 this applies to cars entering either section. The current carried 
 under any condition is one-half ampere. 
 
 trolley wire 
 
 FIG. 193 
 
 Unless a car receives a green signal on approaching a block, 
 that block is in a dangerous condition. A car following one 
 already occupying the block does not affect the signal circuits 
 set up by the former, and a visual indication will not be given 
 to either should a lamp burn out. The latter is a remote possi- 
 bility, since they are renewed monthly. 
 
 The single- wire circuit arrangement used in conjunction with 
 the Eureka system, is shown in Fig. 194. G is a contact maker, 
 consisting of steel combs having contact teeth, connected on 
 one side to the feed wire and to the rail or ground through the 
 electromagnet, M, and the resistance, R. The lamps, L, are 
 
218 
 
 AUTOMATIC BLOCK SIGNALS 
 
 shunted by the resistances, S, so that should any burn out the 
 remainder will still give visual indication. M operates a con- 
 tact arrangement consisting of a rotating structure carrying 
 contact fingers A, which engage with contacts P, 0, and N, 
 according to the position of the mechanism. A similar com- 
 bination is used at B. When, as shown in the figure, the lamps, 
 L, are burning, it indicates that the block is occupied. When 
 this does not occur, the lamps are either connected to the feed 
 wire, or to ground only. But one car at a time can thus occupy 
 a block. 
 
 In the two-wire system, a diagram of which is given in Fig. 
 195, a number of cars can be in the block at the same time. 
 
 Teed wire 
 
 FIG. 194 
 
 The contact comb in this case has three members, a long comb 
 on one side of the trolley wire, and two short ones on the opposite 
 side. The main-current controller, G, has two electromagnets, 
 F and E t which act independently upon the rotating member. 
 When a car enters the block, the current passes from the short 
 comb the wheel comes first in contact with, sending current 
 through the setting magnets and holding the signals at danger. 
 One of the magnets actuates an automatic switch, so that the 
 current passes through the same coil when the second short 
 comb is struck. C and D constitute a current-directing relay 
 whose function, as above stated, is to keep the current from both 
 short combs flowing through the same magnet, when the trolley 
 wheel strikes the contact maker. When a car enters the block 
 it switches the current from both combs through the operating 
 
ELECTRIC RAILWAY SYSTEMS 
 
 219 
 
 magnets, setting the system at clanger; and when the car leaves 
 the block it similarly sets the system at safety. This occurs 
 in both directions. 
 
 Under normal operative conditions, the circuit of an empty 
 block is grounded at both ends. This circuit, as above shown, 
 consists of four green lamps, g, in series with a red lamp, r, at 
 either end of the block. The controller, /, is similar in construc- 
 tion to G] the auxiliary controller, H, being interposed, whose 
 function it is to open or close the magnet-operating circuit. 
 Should two cars enter the block from opposite ends, this latter 
 opens the circuit automatically, so that one car must back out 
 of the block, thereby restoring the apparatus, and giving the 
 
 feed wire 
 
 FIG. 195 
 
 other car the right of way. When a car enters an unoccupied 
 block, H closes the circuit, so that when the car leaves the block 
 at the other end the main controller first energized is again ener- 
 gized, thus restoring the circuits to their normal condition. 
 This device may be dispensed with, but it makes a more effective 
 and desirable combination. 
 
 The United States system employs pivoted disks or " sema- 
 phores " in addition to lamps, these semaphores being operated 
 by magnets. A mechanical locking device also secures the 
 contacts until released by the car's leaving the block. In Fig. 
 196, the internal circuits at each end of the block are shown; 
 and in Fig. 197, the external circuits of the entire block. Since 
 but two lamps are normally in circuit at the same time, resist- 
 ances R are interposed to keep down the current. When a car 
 enters the left-hand (or setting) end, the wheel closes the right- 
 hand side of the trolley switch; the current thereby flowing 
 
220 
 
 AUTOMATIC BLOCK SIGNALS 
 
 through the magnet, B, line 3, to the other signal and ground. 
 When B is energized, it throws over its contact lever, thus dis- 
 
 RCLAY 
 
 connecting the ground wire, and putting the feed from the 
 trolley wire into circuit, the trolley switch contact opening 
 immediately after the car has passed. The green lamp is then 
 
ELECTRIC RAILWAY SYSTEMS 
 
 221 
 
 illuminated and its semaphore thrown, thus indicating that the 
 red lamp and semaphore have been set at the other end of the 
 block. The remaining contacts closed by the movement of 
 the armature of B close a circuit including the outside contact of 
 both trolley switches. The magnet, A, is in series with the sig- 
 naling circuit, and opens two non-interference contacts in series 
 with the trolley switch, thus preventing a car from entering at 
 the opposite end of the block, locking the lever of the magnet, B, 
 at this end, making a normal indication until the car passes out 
 of this end of the block. Line 2 and its connectipns constitute 
 a releasing circuit. Upon the car passing out of the block, it 
 operates the outbound trolley switch, closing the right hand 
 
 SWITCHES 
 -TROLLEY W//?f N \ 
 
 FIG. 197 
 
 contacts, sending a current through C at this end of the block, 
 thus breaking the signaling circuits and that of magnet A through 
 the contacts of the latter's armature ; and unlocking the armature 
 of B by releasing lock piece F. Since B is deenergized, the 
 apparatus is again in its normal condition. The above sequence 
 of connections occurs with a car moving in either direction. 
 The actual arrangement of the contact carrying members H and 
 Kj and of the stationary contacts, G and Z), is not as shown in 
 the figure, where an attempt is made only to show the principle. 
 In the Kinsman system, a remote modification of which is used 
 on the Boston Elevated and Interborough Rapid Transit Rail- 
 roads (electric, although it is equally well adapted to steam roads), 
 an automatic train-stop is employed in conjunction with a manual 
 or automatic visual system in such a way that the control of the 
 
222 AUTOMATIC BLOCK SIGNALS 
 
 train is taken from the engineman or motorman at a critical 
 time, so that it is not possible to pass a danger signal. This 
 arrangement meets the demand for a device which, independ- 
 ently of the motorman or engineman, would set up a retarding 
 effect, preventing procedure into an occupied or otherwise dan- 
 gerous block. 
 
 Fig. 198 shows the above applied to a normal clear automatic 
 visual system. The home and distant semaphore signal, S, has 
 its home control magnet equipped with an auxiliary armature, w, 
 which has a front and back contact, and is in series with a switch 
 box, Ej the slightly elevated guard or contact rails, G, and the 
 battery, B. These contact rails are each about 120 feet in length, 
 with inwardly curved ends. The battery, B, is in two parts; one t 
 side having a voltage of about 5, and the other side 3. The 
 front contact of m is connected to the junction of these parts, 
 so that when it is in the upper position, the voltage impressed 
 on the circuit will be 3, and in the lower position, 8. 
 
 Two contact arms, K, are fastened to, and insulated from, the 
 locomotive; these making a scraping contact with the guard 
 rails. Connected to these contact pieces and the engine or car 
 frame is a circuit containing an electrical recording device, H, 
 and a stop magnet, J, the latter operating directly on the throttle 
 (or control switch, controller, or circuit breaker of an electric 
 train), or being so interposed that it forms a positive link between 
 the throttle and valve. Simultaneously with the shutting off 
 of the steam or current, the air brake is applied. 
 
 Returning to Fig. 198, if a train, represented by the loco- 
 motive equipment, H-K, be moving in an easterly direction 
 with a dangerous track (having the switch A open), and con- 
 sequently with the signal in the danger or stop position; as 
 soon as the contact arms strike the guard rails, a current passes 
 from all of B through m, to the switch box, guard rails, stop- 
 valve magnet, and returns through the frame of the engine 
 and rail. The stop- valve shuts off the steam, applies the air 
 brake, and, by raising its armature, closes the circuit of the 
 danger-recording magnet, HI. This stop- valve magnet requires 
 from 5 to 8 volts at its terminals to operate. At signals C and 
 D, the same connections obtain. The key switch-box is in 
 series with m, so that when the brakeman turns the key, the 
 control circuit will be opened. 
 
ELECTRIC RAILWAY SYSTEMS 
 
 223 
 
 
 i 
 
 1 
 
 \ 
 
 \ 
 
 B 
 
224 AUTOMATIC BLOCK SIGNALS 
 
 If the switch at A were closed, the visual signal would be 
 in the clear position, hence m would close its front contact. 
 This would send a current at a potential of 3 volts through the 
 same circuit, but the stop-valve magnet would not operate. 
 Its armature therefore remains in the lower position, thus 
 causing a current to pass through the safety recording magnet, 
 H2. 
 
 In Fig. 199 the application to a normal danger system is 
 shown. A train is supposed to be in the distant block of signal 
 A, the home block being clear. The current passing through 
 the home magnet, M, by way of the armature of the relay, D, 
 raises m and causes a current to flow through the circuit shown 
 by the heavy lines. Thus the action of the apparatus is similar 
 to that shown in the diagram for normal clear circuits. The 
 current through the recording apparatus is therefore the same 
 in both cases. The latter is not a required part of the arrange- 
 ment, but its use is advisable, since it serves as a check upon 
 the engineman's statements. 
 
 In order that a switching engine may make reverse move- 
 ments at a signal, the circuit is opened at the switch box, 
 which prevents the signal apparatus from operating. In 
 order to prevent failures in this apparatus from causing dis- 
 astrous results, a detector circuit is employed, the relay, D, 
 being in this circuit, which is normally closed. A broken wire, 
 open or exhausted battery, or other defective condition, will 
 open the circuit at this point, and throw the home signal to 
 the danger position. This will also cause the stop magnet to 
 operate if the train passes the stop signal. If at the same time 
 a failure manifests itself in the locomotive and contact-rail 
 equipments, then disaster may accrue. But the probability 
 of such coincidence events occurring is remote. 
 
 The obvious advantages of the Kinsman system are some- 
 what offset by the necessity of adding parts to a car or loco- 
 motive, in opening the circuit at switching movements, the 
 use of contact rails, and the poor protection afforded to a slow- 
 moving freight train pushed by an engine at its rear. An 
 automatic stop, nevertheless, removes one of the greatest disad- 
 vantages of visual signaling devices. 
 
 A difficulty encountered in a grounded-return system is the 
 disproportionate current carried by the track rails, which is 
 
ELECTRIC RAILWAY SYSTEMS 225 
 
 moreover continually varying in value, due to the greater or less 
 conductive continuity outside of the rails, and the uncertainty 
 of the contact of the car wheels therewith. In one system 
 this effect is overcome by making each section a conducting 
 loop with heavy stranded inductive bonds at the insulating 
 joints, which are electrically joined at their adjacent centers. 
 A low-potential transformer secondary with or without an air- 
 gap in the magnetic circuit supplies energy to the section and 
 relays. 
 
 Until proper commercial development has occurred it would 
 be out of place to include a description of such devices, how- 
 ever meritorious they might appear, although several such are 
 being considered by a number of trunk lines. 
 
CHAPTER XVII. 
 MAINTENANCE. 
 
 THE operation of cleaning the zinc and removing part of 
 the more or less saturated zinc sulphate solution from a gravity 
 cell is known as patching. Owing to the impurities which 
 occur in commercial zinc, this element becomes coated to a 
 depth of one-half inch or so with an adhesive brown or gray 
 mass, after about two weeks of ordinary continuous operation. 
 This latter must be removed at regular intervals, or it will 
 interfere with the proper circulation of the liquids, and con- 
 sequently with the operation of the cell. The lower projections 
 of this deposit may either come into direct contact with the 
 copper or with the copper sulphate solution, either of which 
 will produce a partial short-circuit of the cell. 
 
 This mass is removed most expeditiously by a dull knife, 
 after which a long-handled brush with short stiff bristles is 
 used to clean the zinc thoroughly. This may be repeated until 
 but a small amount of zinc remains, when a new element must 
 be used. It is never advisable to leave too little or just enough 
 zinc for the last run, as such a proceeding may result in either 
 complete inoperation before the proper time, or, by setting up 
 too weak a current, produce an unreliable movement, of the 
 track-relay armature. Although failure of the armature to 
 lift can only hold the signal to which it is connected at the 
 danger position, this entails an unnecessary loss of time to 
 passing trains. 
 
 Alternating with the operation of patching is that of renew- 
 ing. The liquids of the cell are thrown away, excepting about 
 one quart of the zinc sulphate solution, which is retained and 
 furnishes the initial sulphuric acid for the renewed cell. The 
 zinc and copper are cleaned of their deposits, and the undissolved 
 crystals of bluestone saved. Two pounds of new bluestone are 
 added, and after the quart of old solution has been replaced, 
 the cell is filled to the proper height with clean water. Renew- 
 
 226 
 
MAINTENANCE 
 
 227 
 
 ing is a wasteful process, but it has not been found practicable 
 to save the saturated copper sulphate solution. The scraps of 
 copper, however, are returned to the supply house. Patching 
 and renewing are performed each month, so that the battery- 
 man goes over his territory every two weeks. This territory, 
 on a double-track road, may be of from 15 to 30 miles in length. 
 All joints in the wiring of a signal system must be soldered. 
 The best way of accomplishing this is by means of molten 
 solder in a crucible or pot, which is poured over the cleaned and 
 fluxed joint by a ladle. All traces of flux are thus removed, 
 and a thoroughly heated joint with a minimum amount of 
 superfluous solder results. After being soldered, the joint is 
 
 B 
 
 / / / / / / 
 
 FIG. 200 
 
 carefully taped, preferably first with rubber strip, the latter 
 being covered with a thin layer of binding tape. The finishing 
 consists in either gently heating the joint, or painting with a 
 quick drying waterproof solution. 
 
 The proper joining of copper conductors to the steel rail is 
 a matter of primary importance, a certain amount of skill being 
 required. In Fig. 200, A is the formed iron wire end which is 
 to be connected to the rail by channel pins or plugs, for either 
 a relay, controller, or battery connection. At B the wire is 
 twisted, which constitutes the second step, and C shows an 
 insulated copper wire inserted in the loop, the insulation being 
 removed from the loop to the end. This wire is twisted around 
 the iron, forming Z), after which it is soldered, as at E, near the 
 
228 
 
 AUTOMATIC BLOCK SIGNALS 
 
 end of the joint, so that the insulation will remain uninjured. 
 After making sure that not a trace of flux remains, the joint is 
 taped carefully, as shown at F. 
 
 The manner of connecting and housing such a taped joint is 
 shown in Fig. 201. A gives a section of the rail and an end view 
 of the wood trunking or duct; B is a longitudinal section, and C 
 an elevation. The weather cap, D, is shown removed at B. 
 
 Track batteries should be frequently and carefully inspected 
 to determine not only their physical condition, but their elec- 
 trical performance when operating. Faulty or dirty connec- 
 tions may result in the addition of considerable resistance. 
 
 FIG. 201 
 
 Thus, in taking a millivoltmeter reading across the cells, and at 
 the track, if even a slight difference occurs, a high resistance 
 may occur between these two points. This may be due to 
 faulty connections, too much or too fine wire, and, in some cases, 
 imperfect contacts at the pole-changing switch. 
 
 A relay which fails to close its armature circuit with its mini- 
 mum current should be at once replaced, and contacts that 
 have been fused by lightning and then separated should be 
 discarded. When track sections are inspected, the bonding, 
 insulating joints, condition of the ballast, rail connections, and 
 line wires should also be given attention. It is well to make 
 memoranda of everything noted, so that local operative con- 
 ditions may be deduced from the data thus obtained. The 
 
MAINTENANCE 
 
 229 
 
 numbers of all cut-sections and signals should be tabulated, 
 thus systematizing the entire territory. 
 
 When a battery reading is obtained at one end of a section, 
 it should be compared with the reading at the other end of this 
 section. Either may be the battery or relay ends, depending 
 upon the direction taken. Proper drainage of the roadbed must 
 be insisted upon; and the relative amount of moisture present 
 may be found by these readings. 
 
 In hot weather the expansion of the rails may force the 
 fiber rail-ends slightly above the level of the rail face. Passing 
 trains then pound off this projecting piece, ultimately destroy- 
 ing the fiber, and sometimes causing the upset parts of the rail 
 to come into contact. This results in one side of the adjacent 
 
 ABC D E F G H I JKLMNOPQ. R S 
 
 1.3 
 J.I 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 *> 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 -- 
 
 ^ 
 
 
 
 
 
 
 
 
 .9 
 .6 
 .? 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ' 
 
 h^ 
 
 
 
 396O 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ' 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 O 600 J20O J800 ZtOO 3000 3600 
 feet 
 
 FIG. 202 
 
 sections being connected, interfering with the normal operation 
 of the system This is a condition that is difficult to remedy, 
 and replacing of the rail end must ultimately be resorted to. 
 
 In Fig. 202 (which shows one square for each one hundred 
 in the original), the voltmeter readings obtained from a typical 
 wireless cut-section have been plotted. The cross-section paper 
 on which the results are given should allow one vertical division 
 for each one-hundredth of a volt, or 100 divisions per volt. 
 Each horizontal division may be equivalent to one rail length, or 
 
 5280 
 30 feet, there being = 176 divisions per mile of track. The 
 
 voltage curve is found by joining the points of intersection of 
 the voltage reading obtained at each ten-rail section with the 
 horizontal equivalent' of the number of rail lengths from the 
 
230 AUTOMATIC BLOCK SIGNALS 
 
 starting point. The voltage is measured at each change in 
 connections. At A we have the voltage at the battery ter- 
 minals; B is the voltage at the terminals of the polarity changer; 
 C at the connection of the pole-changing switch with the track 
 wires; D the voltage between the rails; E to Q, inclusive, the 
 voltage at the various equidistant divisions; Q that at the 
 last rail length considered (No. 132, or 3960 feet from D); and 
 R and S that at the end of the rails and terminals of the track 
 relay respectively. The reason for the line, D-Q, not being 
 straight is because of the different effects introduced by the 
 heterogeneous conditions of the ties, unequal depth of ballast, 
 non-uniform resistance of bond wires, and various specific rail 
 resistances; although this curve may be taken as being suffi- 
 ciently uniform to show good practice. The current taken 
 by the relay (.62 ampere) was too slight to introduce any per- 
 ceptible temperature effect. With a battery voltage of 1.32 
 the following readings are apparent from the curve at the 
 various points where measurement was taken. 
 
 Voltage at Volts 
 
 A y or battery terminals 1 . 32 
 
 B, or pole changer terminals 1. 32 
 
 C, or track wires 
 
 D, or between rails 
 
 .32 
 .28 
 .25 
 .21 
 .18 
 .15 
 .10 
 .06 
 .03 
 
 E, or between rails at 10 rail lengths ' 
 
 F, or between rails at 20 rail lengths 
 
 67, or between rails at 30 rail lengths 
 
 jB, or between rails at 40 rail lengths 
 
 I, or between rails at 50 rail lengths 
 
 t7, or between rails at 60 rail lengths 
 
 K, or between rails at 70 rail lengths 
 
 L, or between rails at 80 rail lengths 1 . 00 
 
 M, or between rails at 90 rail lengths 98 
 
 N, or between rails at 100 rail lengths 95 
 
 O, or between rails at 110 rail lengths 92 
 
 P, or between rails at 120 rail lengths 89 
 
 Q, or between rails at 130 rail lengths 86 
 
 .R, or pole changer at 132 rail lengths 84 
 
 S, or track relay at 132 rail lengths 82 
 
 Should abrupt changes occur in the direction of such a curve, 
 it indicates that conditions at this point are abnormal. Thus, 
 a high-resistance bond wire, or poor joints in a series of rail 
 
MAINTENANCE 231 
 
 lengths will result in a line which does not conform to the 
 general direction of the remainder of the line. Theoretically, 
 the line joining the points at which indications are taken should 
 be straight, but the factors above mentioned introduce varia- 
 tions of direction. Should considerable current leakage occur, 
 the change in the direction of the line would be at once evident. 
 The curve given is a fair example of what may be expected 
 with gravel ballast, with a relay of 3 1-2 ohms resistance, 
 which requires a minimum of .23 volts to lift its armature. 
 This condition gives a wide possible variation of voltage through 
 which the armature will rise, which is necessary, because of varia- 
 tions in the weather conditions. On account of the decrease 
 in the length of air-gap, and the consequent increase in the 
 permeability caused by the motion of an armature, it follows 
 that the minimum voltages that commence motion will produce 
 a good closing of the contacts. 
 
 The voltage of the relay being .82 and its resistance 3.5 ohms, 
 the current flowing through it will be .82 -f- 3.5 or .234 ampere. 
 As the output of the battery is .62 ampere, the relay evidently 
 takes only a fraction of the total current, or 38 per cent; the 
 remainder, 62 per cent, being shunted across the rails by the 
 ballast and timbers, which represents an average percentage of 
 leakage, the drops in potential in the rail being also considered. 
 
 Where cinders or culm are intermixed with gravel, or when 
 the former are used exclusively as ballast, a material change 
 in the readings obtained will be evident. This is due to the 
 better conducting qualities of the former and to the better con- 
 tact usually made with the rail. Fig. 203 illustrates an average 
 of such cases. A battery of six gravity cells, connected in 
 multiple, was used in this case, the current passing to the rails 
 being one ampere, A being the voltage at the battery and B at 
 the track. From B to M are measurements taken at regular 
 intervals of 600 feet (20 rail lengths), the section being 7020 
 feet in length, N being the track voltage at the end of the 
 section, and .35 the voltage at the relay. 
 
 The relay resistance is 3.5 ohms, with a terminal e.m.f. of 
 .35 volts, the current taken being .35 -^ 3.5 or .1 ampere, the 
 remaining .9 ampere or 90 per cent leakage through the ballast 
 from rail to rail. 
 
 This represents a case where failure of the relay to operate 
 
232 
 
 AUTOMATIC BLOCK SIGNALS 
 
 may be expected in wet weather, owing to the better conduct- 
 ing qualities of the ballast at such times. Since .35 volt is 
 just above the operating e.nuf. or such a relay, the reason for 
 such failure is obvious. 
 
 The conditions above represented may be eliminated by 
 shortening the length of the section, or by dividing it into a 
 number of sections. If we divide it into two equal parts, and 
 use two sets of batteries and relays, the length of each section 
 will be 3510 feet, the e.m.f. at the end of the first section will 
 be (from the curve) about .51 volt, or 46 per cent above 
 .35 volt. 
 
 Since a greater relative gain is made by excluding some of 
 the loss due to the track leakage, the actual result will be some- 
 
 . 
 
 J K L M 
 
 1200 2VOO 3600 80O 6000 7200 
 
 feet 
 
 FIG. 203 
 
 what in excess to the above. It should be remembered that a 
 track section must be designed to give a maximum of voltage 
 at the relay, with a minimum of leakage, so that a minimum 
 number of track cells in multiple is required. Because of the 
 great variations in the resistance and insulation of a track sec- 
 tion, it is not possible to give a fixed rule as to the voltage 
 that should be maintained at the terminals of a relay. 
 
 Numerous multiple paths are afforded, even under favorable 
 conditions, for leakage from rail to rail. For this reason the 
 voltage across the latter must be very low, otherwise the per- 
 centage of lost energy will be too high. This voltage, however, 
 could not be excessively low (as for instance that which would 
 be obtained from a few thermoelectric couples in series) or 
 relays could not be satisfactorily operated, and the shunting 
 
MAINTENANCE 233 
 
 action of a train in a long section might not remove sufficient 
 current from such a relay's coils. Ties are of hard wood of high 
 specific resistance, but since from ten to twenty-five thousand 
 spikes are driven in them to the mile, it is seen that the reduc- 
 tion in insulation resistance becomes very great indeed. Par- 
 ticularly is this true when the ties are wet and slate or culm 
 ballast is used. The latter frequently contains considerable 
 sulphuric acid, which, by associating with the water, greatly 
 reduces the specific resistance of the ballast. 
 
 With properly designed relays and other current-taking 
 devices a larger number of cells should preferably be used in the 
 main battery than is required under normal conditions. This is 
 because the cells ordinarily used are more efficient when a mod- 
 erate current is taken from them. Abnormal current discharge 
 results in polarization (with concomitant increase of resistance, 
 loss, of energy, and reverse e.m.f.), sluggishness of chemical 
 action, and poor recuperation, while the ampere-hour capacity 
 is greatly reduced. 
 
 In winter, cells have to withstand long-continued low tem- 
 perature, which decreases their terminal voltage somewhat, and 
 increases their terminal resistance. The drop in potential in a 
 battery is thus much greater when low temperatures obtain, so 
 that the load upon them is increased, especially when motors 
 are in circuit. Motors require heavy initial current discharge, 
 so that the voltage falls very rapidly when they are in circuit. 
 High voltage thus becomes desirable in a signal circuit, and is 
 more than compensated for in economy of operation. Another 
 argument for high voltage is the liability of a low potential 
 not overcoming the resistance under the motor brushes 
 which a particle of dirt, congealed lubricant, or moisture 
 interposes. 
 
 To find the insulation resistance of any circuit, as, for instance, 
 that between the rails of a track section, having given a volt- 
 meter whose resistance is known, connect the latter in series 
 with the resistance to be measured, and a battery whose voltage 
 is approximately equal to the range of the voltmeter scale. 
 After noting the reading, measure the battery voltage. Divide 
 this latter result by the former, and add one to the quotient, 
 which, when multiplied by the voltmeter resistance gives the 
 required resistance. Thus with a battery reading of 2.8 volts, 
 
234 AUTOMATIC BLOCK SIGNALS 
 
 and a resistance reading of .9 volt with a voltmeter resistance of 
 
 (28 \ 
 '- hi) X 200 = 822 
 
 ohms. 
 
 The slot and slow-releasing magnets of a normal clear two- 
 arm semaphore signal, with a working battery of 16 cells (11.2 
 volts) require a current of 16 milliamperes (.016 ampere). 
 These three magnets, which are connected in multiple with the 
 battery, have a combined resistance of 700 ohms, and have 
 sometimes equal resistances, or about 2100 ohms each. The 
 total current required per day (assuming that the semaphores 
 remain at clear) is, therefore, .384 ampere-hour. The average 
 motor current required is two amperes, the actual current being 
 greater when the motor starts, and less when full speed is reached, 
 due to the full counter e.m.f. which is developed in the latter 
 case. 
 
 With 100 train movements a day, both semaphores would 
 operate 100 times, so that the motor actually operates 200 
 times. With trains in the block for say three minutes each, 
 the slot magnets would not be energized for 300 minutes out of 
 each day, or 5 hours. The daily current discharge into the slot 
 and slow-releasing magnets is thus only .304 ampere-hour. There 
 can be eight blade movements per minute of motor operation, 
 so that the motor will be in use for 25 minutes a day, or .416 
 hour, the current required being .932 ampere-hour, which, 
 added to the .304 ampere-hours required for the slots, etc., gives 
 1.236 ampere-hours. As the capacity of the cells used is ordi- 
 narily 300 ampere-hours, they will last when operating this 
 signal for about 240 days, allowing for some depreciation. 
 
 When a smaller number of train movements occur the cells 
 will last longer. One-arm signals could be relied on to give a 
 battery life of from one to two years, the latter being in extreme 
 cases, as the best of cells cannot be left on an intermittent circuit 
 for so long a time and be depended upon. The resistances of the 
 compound slot magnets of a signal can have high values, owing 
 to the heavy series winding which carries the motor current when 
 the latter is operating, and thus compensate for the drop in 
 potential due to the momentary heavy demand on the battery. 
 
 Maintainers and inspectors will find a voltmeter having two 
 scales desirable: one reading up to three volts, and having fifty 
 
MAINTENANCE 235 
 
 divisions per volt; and the other reading up to 15 volts with 
 ten divisions per volt. With the former it is possible to read, 
 with some show of accuracy, in millivolts. A milliammeter is 
 also a useful prerequisite to check up the resistances and input 
 of relays and other magnets. 
 
 Motor brushes should be adjusted to exert only such pressure 
 upon the commutator as is consistant with good electrical 
 contact. The ends or leaves should be spread apart, to avoid 
 the introduction of an open circuit by contact only with one of 
 the mica strips separating the bars. 
 
 The buffers or dashpots on motor signals should receive 
 careful attention, otherwise injury will result to the moving 
 system or too great a retardation will occur. The vent should 
 be so adjusted that the loss of speed (resulting on the tendency 
 to form a vacuum) when clearing is imperceptible. In lubri- 
 cating, heavy oil must not be used and care should be taken 
 that dust or dirt does not enter the buffer chamber. A light 
 non-freezing oil is best for use on all moving parts, including 
 the motor commutator, it being sparingly applied on the latter 
 by a cloth. When a signal is in the danger position all the 
 weight of the moving system should be borne by the spec- 
 tacle casting and its stop. On no account should the slot be 
 impeded in any way. 
 
 The clearing of a semaphore by a motor is a rather tedious 
 process, from six seconds to a quarter of a minute being required. 
 With a two-arm arrangement, the motor must start up twice 
 when the distant and home are cleared in the proper sequence 
 after a train has passed a signal. 
 
 Relay boxes must be of such construction that insects can- 
 not enter, as their operation sometimes causes open circuits or 
 false conditions. They must also be weatherproof, although 
 extreme care need not be exercised, providing the relays are 
 enclosed in glass covers, which is the present practice in con- 
 struction. Motor armatures should also be well protected, 
 particularly at the commutator end, as a trifling amount of dirt 
 at this part may cause endless trouble. Although an open 
 circuit in the motor can only result in a false danger indication, 
 this produces a certain amount of delay to through trains. 
 All operated contacts must be enclosed in closed housings to 
 prevent access of moisture or dust. 
 
FIG, 204 
 
MAINTENANCE 
 
 237 
 
 Engineers or conductors are generally requested to fill out 
 blanks when held by a signal for which the immediate cause 
 is unknown. These are passed to the maintainer or inspector, 
 whose duty is to at once examine the signals and accessories 
 to determine the cause of failure. Maintainers, batterymen, 
 supervisors, and engineers, with the maintenance-of-way corps, 
 exercise such a strict observance of the working conditions that 
 it is not often a failure takes place undetected. Such constant 
 supervision, particularly on roads having heavy traffic, is abso- 
 lutely necessary to keep up the integrity of a signal system. 
 
 FIG. 205 
 
 When any serious trouble occurs, its results increase with great 
 rapidity, owing to the momentous position which signals possess 
 in a competent aggrandization. Maintainers must go over 
 their entire territory immediately subsequent to a lightning 
 storm, replacing fuses and inspecting relay points. Special 
 engines are delegated to assist in performing this service, a 
 flurry of telegrams and messages being coincident. 
 
 Continuous spectacles and castings are advancing in favor, 
 and are meritorious because they prevent a clear indication 
 until the semaphore has described more than two-thirds of its 
 working arc, also eliminating the complete shutting off of the 
 
238 
 
 AUTOMATIC BLOCK SIGNALS 
 
MAINTENANCE 
 
 239 
 
 light at any point or angle of transition when moving for an 
 indication. A drooping semaphore may readily be detected hi 
 
 ***<*. ^SpfSS 
 
 daylight by the engineman; but in the dark this is difficult, 
 as he is only governed by the color of the intercepted light. 
 Hence, a partly cleared or improperly displayed member, while 
 
240 AUTOMATIC BLOCK SIGNALS 
 
 readily perceived in the daytime, at night may give a clear 
 indication when such is wrong. Sight shields only remedy 
 this difficulty, by showing the engineman that he must come to 
 a stop, by reason of the rules governing improperly displayed 
 signals. 
 
 Fig. 201 shows a generator and switchboard used in a typical 
 transmission scheme for storage battery charging.- The gene- 
 rator has a terminal e.m.f. of 500 volts, and in this case is 
 bipolar and compounded. The series winding is shunted for 
 adjustment of the compounding, an equalizer being used when 
 two or more are connected in multiple. The switchboard 
 contains, on each side, a main switch, D, circuit-breaker E, 
 fuses F, ammeter A M, and a voltmeter, V M, which is thrown 
 on either side of the lines by switch S. The circuit-breaker will 
 open on " no voltage " or " reverse current," by the action of 
 the shunt coil, A } or through an overload by the series coil, B, 
 the contact blades being shown at C. G is a rheostat for 
 changing the terminal voltage by variation in the current passing 
 through the shunt field-coils. The individual storage batteries, 
 both east and west, are connected in series. The use of two 
 multiple lines assures the maximum distance of transmission 
 at a minimum line loss. 
 
 We have, in Fig. 205, a comprehensive, normal, clear cir- 
 cuit, such as occurs on the L. S. and M. S. R. R., which 
 includes most of the connections that have heretofore been 
 considered. In view of the preceding descriptions, this need 
 not be analyzed, but it covers the standard storage battery-line 
 wire arrangement now being extensively applied to trunk lines. 
 
 In conclusion, Figs. 206 and 207 contemplate normal danger 
 circuits on the Erie Railroad, from Bergen, N. J., to Suffern, 
 N. Y. Included therein are slot control of mechanical sema- 
 phores, a charging line arrangement, and indicators at B J, 
 tower. This exemplifies the circuits usually employed at inter- 
 locking plants, and is typical of the electrical control of long- 
 established mechanically operated semaphores, and their appli- 
 cation as a supplement to an automatic network. 
 
INDEX. 
 
 Advance signal, 1. 
 
 All-electric interlocking, 142, 179-200. 
 
 Allentowii Terminal B. R., circuits, 
 
 42-47. 
 
 Annunciator, drop, 168, 159. 
 Armature, use of neutral, 61. 
 
 use of polarized, 62. 
 Arresters, lightning, 129, 130. 
 Atlas insulated joint, 101. 
 Automatic motor brake, 41. 
 Automatic signals defined, 1. 
 
 Batteries, 84-94. 
 
 types of, 84. 
 Bell circuits, 38, 40, 42. 
 Bell-indicator, 139, 140. 
 Block signals denned, 1. 
 Bonds, inductive, 225. 
 
 track, 96, 97. 
 
 Brakes, automatic motor, 41, 120-122. 
 Breakers, circuit, 25. 
 
 Cells, renewing and patching, 88, 89. 
 
 thermo-electric, 14. 
 
 types of, 84. 
 
 use of primary, 14. 
 Charging storage batteries, 90-93. 
 Circuit breakers, 25. 
 
 controller, 59. 
 
 controllers, magnetic, 70-73, 159. 
 
 coupler, 102. 
 
 Circuits, at interlocking tower, 46, 
 74. 
 
 crossing signal, 25. 
 
 controller, 16. 
 
 disk, 15. 
 
 electro-gas signal, 167-169. 
 
 electro-pneumatic, 160, 161. 
 
 normal clear, 50-67, etc. 
 
 normal danger, 30-49, etc. 
 
 open track, 12, 143-146. 
 
 semi-automatic, 18, 48, 49, 68-83, 
 etc. 
 
 Circuits Continued. 
 
 siding control, 23. 
 
 simple, 15-29. 
 
 simple normal clear, 20. 
 
 simple normal danger, 9. 
 
 single track, 41, 42. 
 
 supplemental bell, 17, 38-42. 
 
 three-position, normal danger, 45-48. 
 
 working, 8. 
 Clear conditions, false, 10. 
 
 C. N. O. & T. R. R. circuits, 34-36. 
 Coleman's apparatus, 106-112. 
 Common line, 30-47, 53, 57. 
 Commutator, 69. 
 
 Control circuits, defined, 8. 
 Control, semi-automatic, 18, 48, 49. 
 
 semi-automatic track circuit, 19. 
 Controlled manual systems, 105-118. 
 Controllers, duplex rotary, 164, 165. 
 
 rotary switch circuit, 163, 164. 
 
 use of lever circuit, 116. 
 
 use of duplex rotary, 117. 
 
 use of foot, 118. 
 Cut-out, 192, 193. 
 Cutouts, relay, 13. 
 Cut-section, 2, 56. 
 
 connections at, 103, 104. 
 
 Danger conditions, false, 10. 
 Detector bars, use of, 178. 
 Disk indicator, 132, 138. 
 
 instrument, 132. 
 
 mechanism, 151, 152. 
 Distant signal control, 16. 
 
 D. L. & W. R. R., circuits on, 74-83, 
 
 192, 193. 
 Double electromechanical slot, 138, 
 
 139. 
 
 route interlocking, 179. 
 semaphore motor mechanism, 136- 
 
 138. 
 track circuits, 38, 39, 62, 63. 
 
 241 
 
242 
 
 INDEX 
 
 Edison cell, 87. 
 
 Electric locking, 170-178. 
 
 locking defined, 170. 
 
 locks, 74. 
 
 railway signals, 215-225. 
 
 releases, 172, 173. 
 
 slots, 106-110, 113-116, 138, 139. 
 Electro-gas signal apparatus, 161-167. 
 
 circuits, 167-169. 
 Electro-pneumatic signal circuits, 160- 
 
 161. 
 
 Erie R. R., circuits on, 238-240. 
 Eureka signals, 217-219. 
 
 Failures at clear, 11. 
 at danger, 11. 
 
 G. E. three-position circuits, 207 211. 
 
 three-position signals, 209-214. 
 Gordon cells, 84 86. 
 Grafton three-position signals and cir- 
 cuits, 201-207. 
 
 Hall Signal Co. apparatus, 131-141. 
 
 three-position electro-gas signal, 214. 
 Hewett open-track circuits, 143-146. 
 Hold-clear coils, 43. 
 Home signal defined, 1. 
 
 Indication of block's condition, 2. 
 Indicator circuits, 38. 
 
 disk, 132, 133, 157, 168. 
 
 magnetic circuit controller, 70-73. 
 
 polarized, 155, 156. 
 
 semaphore, 157. 
 
 switch, 25, 140. 
 
 use of polarized, 13. 
 Installing track cells and relays, 102, 
 
 103. 
 Instrument, disk, 132. 
 
 switch, 140. 
 
 track, 96, 97. 
 
 use of switch, 22, 23, 99, 100. 
 Insulation of switch rods, 100. 
 Interlocking, all-electric, 42, 179-200. 
 
 machine, 193-196. 
 
 machine lock, 172. 
 
 relay, 134. 
 
 use of, 2. 
 
 Joints, making wire, 227, 228. 
 
 Key, spring, 70. 
 
 Kinsman signals and circuits, 221- 
 225. 
 
 Lamps, use of incandescent, 43, 44. 
 Lehigh Valley R. R., circuits, 42^7. 
 Leonard's control scheme, 112, 113. 
 Lever appurtenances, 195, 196. 
 
 circuit controller, 68, 72-74. 
 Lightning arresters, 129, 130. 
 
 overcoming effects of, on relay con- 
 tacts, 126. 
 
 Line-wire circuits, 22-48. 
 Lock and block arrangement, 112. 
 Locking, electric, 171-178. 
 L. S. & M. S. R. R., circuits on, 237, 
 240. 
 
 Magnetic circuit controllers, 70-73, 
 
 175. 
 
 Maintenance, etc., of signals, 226-240. 
 Manual signal control, 105, 106. 
 Mercury rectifiers, use of, 91-93. 
 Missouri Pacific R. R., circuits on, 58, 
 
 60. 
 Motor brakes, 120-122. 
 
 control relays, 40. 
 Motors, signal, 119-122. 
 
 Neutral armature, use of, 51. 
 New York subway signals, 216. 
 Normal clear circuits, 60-67. 
 
 simple, 20. 
 
 Union, 147-149. 
 Normal danger circuits, 30-49. 
 
 Hall, 141-146. 
 
 simple, 21-23. 
 
 Outlying switch lock circuits, 175, 176. 
 Overlaps, circuits, 104. 
 use of, 26, 66-64. 
 
 Patching cells, 226. 
 Permissive signaling, 106. 
 Polarized, armature use of, 52. 
 
 normal clear circuits, 50-52. 
 
 relay, 123-125, 132. 
 Pole changer, reversible, 199. 
 Preliminary considerations, 1-14. 
 Preparatory control functions, 68. 
 
 Quadruple breaks, 64, 209, 
 
INDEX 
 
 243 
 
 Rail joints, 101. 
 Rectifiers, mercury, 91-93. 
 Relayed section, 66, 68. 
 Relays, heavy current, 125. 
 
 inspection of, 228-235. 
 
 interlocking, 134. 
 
 motor control, 40. 
 
 neutral, 126, 134, 136. 
 
 polarized, 123, 125. 
 
 resistance of, 127. 
 
 slow-releasing, 69. 
 
 Taylor neutral track, 123. 
 
 with glass housing, 134-135. 
 
 Sector block, 173, 174. 
 Selector, ground, 199. 
 
 hook, 199, 200. 
 Semaphores, arrangement of, 3. 
 
 motor operated, 6. 
 
 principles of application, 6, 7. 
 Siding control circuits, 23, 35, 36. 
 Signals, advance, 1. 
 
 bridge, 6. 
 
 distant, 1. 
 
 external design of, 4. 
 
 enclosed disk, 131, 132. 
 
 electric railway, 215-225. 
 
 electro-gas, 161-167. 
 
 electro-pneumatic, 160, 161. 
 
 numbering, 2. 
 
 semaphore, 3, 5, etc. 
 
 semi-automatic, 10, 68. 
 
 three-position, 201-214. 
 Slot, double electro-mechanical, 138, 
 139. 
 
 electric, 106-110. 
 
 magnets, 44, 53. 
 
 slow-releasing, 129. 
 
 Slow-releasing relay, 68, 152, 153. 
 Southern Pacific R. R., circuits on, 
 65-59. 
 
 storage batteries, 89-93. 
 Switch contacts, use of, 9. 
 
 indicators, 25, 140, 141. 
 
 instruments, 22, 23, 42, 99, 140. 
 
 lock, 170, 175, 176, 196-198. 
 
 movement, 196-198. 
 
 Tappet bars, 184. 
 
 Taylor neutral track relay, 123, 
 
 hook selector, 199-200. 
 Telephone transmitter, 76, 79, 81. 
 Three-position signals and circuits, 
 
 45-48, 201-214. 
 Track battery inspection, 228. 
 
 circuit, the, 95, 104. 
 
 control, 64. 
 
 instruments, 96, 97. 
 
 simple, 95. 
 
 Tram staff control circuit, 177, 178. 
 Transmission gear, 122, 123. 
 
 TIni signals, 216, 217. 
 
 Union Switch & Signal Co. apparatus, 
 
 147-159. 
 
 normal clear circuit, 147-149. 
 United States signals, 219-221. 
 
 Voltage curves, relay, 128, 232. 
 
 battery, 229. 
 Voltage, determining battery, 228-234. 
 
 Wells, battery, 93, 94. 
 
 Wireless or track circuits, 141, 143. 
 
 Wires, bond, 96, 97. 
 
 Working circuits, 8. 
 

 
YC 6V509 
 
 UNIVERSITY OF CALIFORNIA LIBRARY