US2082465A - Train dispatching system for railroads - Google Patents

Description

June l, 1937. N. D. PRESTON TRAIN DISPATCHING SY TEM FOR RAILROADS Filed May 7, 1929 4 Sheets-Sheet l nw nun 3 @L S ma .m @NN ms NN m4 IAL: liv@ R R u :ISS -o. A.. T R NM R m0 .V... www

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N. D. PRESTON TRAIN DISPATCHING SYSTEM FOR RAILROADS Filed May '7, 1929 4 Sheets-Sheet 4 Fl G 4. EES) E-SP Patented June l, 1937 Nl'rsn TRAIN DISPATCHING SYSTEM FOR RAILRUADS Neil D. Preston, Rochester, N. Y., assignor to General Railway Signal Company, litochester,

Application May 7, 1929, Serial No. 361,229

36 Claims.

This invention relates to systems forvhandling railway traflic, commonly known as dispatching or centralized traiiic control systems, and more particularly to a communication system for facilitating the transmission of the necessary controls or indications to and from the dispatchers oice or central control point.

In accordance with the present invention, generally speaking, it is proposed to establish communication between the dispatchers oflice and each of the several stations along the track one at a time in turn, and transmit from the dispatchers oice to each station as selected the desired controls by impulses in a predetermined code pattern, and simultaneously transmit indications from that station to the dispatchers oce over channel circuits set up sequentially by the same impulses. In transmitting the controls from the dispatchers ofce to a station, it is proposed to employ distinctive codes which respectively correspond to the combined operation of the switches and signals at that station required to establish a particular route for train movement, rather than control the switches and signals separately and independently by different codes.

Another characteristic feature of the invention is'that it is normally inactive and not operating, but is automatically set into operation upon any change in track circuit occupancy at any station. When thus set into operation, on account of the need for transmitting a new indication to the dispatchers office of a train movement, the system is organized to scan the whole controlled territory and transmit all of the control codes and indications.

The system, when inactive, may also be set into operation manually by the dispatcher, after he has changed the position of the control levers for some station or stations; and when the system is thus manually set into operation, the stations in turn are quickly selected, starting Aat the one nearest the dispatchersoifice, until the station is reached where a new control is to be transmitted, whereupon the code control and indication channel circuits for that station are automatically set up.

Another feature of the invention is that the dispatcher may, if he wishes, limit the transmission of control codes Vand the setting up of indication channel circuits to a given station, for as long a time as he Wishes, so that he is able to obtain prompt response to lever movements for zthat station, and prompt information of change in track circuit occupancy at that station.

Another characteristic feature of the invention is that the operator may at any time manu ally set the system into operation to obtainy a check of the condition of all of the track relays, switch machines, signals, and other controlled devices, and also automatically transmit the necessary control codes to cause the several switches, signals and the like to assume positions corresponding with the then existing positions of the control levers in the dispatchers office.

Other characteristic features, functions, and advantages of the 'system of this invention will be in part apparent, and in part specifically pointed out, as the description progresses.

For the purpose of explaining the nature of the invention, andas one specific typical embodiment of the invention, there is shown in the accompanying drawings, in a simplified and diagrammatic manner, the devices and circuits illustrative of the equipment in the dispatchers oiiice and at way-stations along the track, in the form preferably adopted for controlling traffic on a single track railroad; but it should be understood that the principles and functions of the invention'may be employed for the control and indication of switches, signals, or other traflic controlling devices for various other track lay- 30 outs. To `simplify the illustration and facilitate explanation, the parts and circuits are shown in the drawings diagrammatically, with Various conventional illustrations, more with the object of making it easy to understand the principles 3- and mode of operation,v than with the idea of showing lspecifically the construction and arrangement of parts preferably employed to fit the practical operating conditions encountered in practice. 40

In the accompanying drawings, Fig. 1 illustrates the equipment in the dispatchers oiiice; Fig. 2 the equipment at one station nearest `the dispatchers oice; Fig. 3 certain parts and circuits at two other stations, these three figures, when placed end to end, being intended to illustrate the ielements, or units which are duplicated to make a complete system; and Fig. 4 shows a detail modification of the starting circuits.

In describing in detail the specific embodiment of the invention shown in the drawings, the general organization of the system will be first discussed,"a`nd then the operation of the system explained.

The various electrical connections between the Various parts of the equipment in the dispatchers oiiice and at the several stations are conveniently pointed out in connection with the description of the operation. For simplicity, the circuits have been shown as terminating at (B+) (B-) CN or C, these symbols indicating connections to the terminals of suitable sources of current, such as batteries, motor-generators, or the like. The circuits wholly local to the dispatchers oice or a station are indicated as terminating at or The symbol C indicates a connection to the common wire C; and the symbol CN indicates a connection to a center or mid-tap of the sources indicated by symbols and The symbols (B+) and (B-) indicate connections to the terminals of opposite polarity of a source of current having a center of mid-tapV connected to the common wire C, so as to provide energy of opposite polarity for the several line circuits.

The equipment in the dispatchers olitec-At the central control station, conveniently termed the dispatchers oflice, where the operator or dispatcher is stationed, the equipment, shown in Fig. 1, comprises in general, a suitable track diagram of the track layout of the territory under the supervision of the dispatcher, with small electric lamps to indicate the presence of trains on Various track sections; a number of manually operable levers, two for each station, which the dispatcher manually sets to different positions to control the switches, signals, or the like at the several stations; a plurality of channel circuit selecting means, one for each station, in the form of a group or bank of neutral relays; a power operated rotary circuit controlling device, conveniently termed a station selector, for establishing the necessary electric inter-connections between the banks of channel circuit selecting relays, and the other devices of the dispatchers office equipment, and also for transferring the communication from station to station; an impulse producing device, one for each station, in the formcf a rotary code wheel; and various other manually operable keys for the several stations, relays, and auxiliary circuits for providing the automatic starting and stopping of the system, and its various other functions.

As representative of the track diagram, there is shown in Fig. 1 one end of a passing siding ps, with an OS lamp fi to indicate, when lighted, that there is a train present on the usual detector track circuit at the corresponding end of the corresponding siding PS in the field. In practice, of course, this track dia-gram comprises a large number of stretches of track, with passing sidings, cross-overs, and thelike, with many indicator lamps, like 6, to show the presence of trains at the various points. Each OS lamp 6 is controlled by an OS relay l of the polar type, having a dead-beat armature 3, which is moved to one or the other extreme position, depending upon the polarity of current iiowing through the winding of this relay, and which remains in the position in which it was last set,

until current of the opposite polarity is supplied to the relay. The OS lamps 6 may be specially controlled, in the manner disclosed in my prior application Ser. No. 199,325, filed June 16, 1927, so that new indications may be readily recognized by the dispatcher.

As representative of the manually operable control levers, there is shown in Fig. 1 a lever SM, preferably arranged to be moved up and down to either of two extreme positions, this lever being the one used to control the position of the power operated switch at the corresponding end of the siding PS. Another lever SG, movable from an intermediate or middle position (in which it is shown) to the right or left, controls the clearing of the signals at the corresponding end of the distant siding, and selects the direction in which traffic may be permitted to move at that end of the siding. These two levers SM and SG are preferably correlated by position with the track diagram, and may also be identified with the corresponding portion of the track diagram by number, color or the like.

The levers SM and SG are employed to open and close contacts in their different positions. As diagrammatically shown, the lever SM shifts two contact arms or switch members i6 and I1, into engagement with contacts indicated as arrows. Similarly, the lever SG moves a contact arm IS into three different positions into engagement with contacts indicated as arrows.

The rotary circuit controlleror station selector F, in the simplified form diagrammatically shown in Fig. 1, comprises a shaft 20, indicated by dash lines, which is arranged to be driven by a suitable electric motor 2| through a friction clutch 22. It is contemplated that the motor 2l is constantly running and tends to drive the shaft 20, the clutch 22 slipping when the shaft is held stationary. This is merely a typical arrangement, and other devices may be employed for operating the shaft 20.

The rotation of the shaft 2B is controlled stepby-step by a suitable escapement means, which as shown comprises an escapement wheel 23, with a number of teeth around its periphery corresponding with the number of stations of the system. The space between two successive teeth in the escapement wheel 23 represents a movement of the shaft 29 from one station position to the next, and corresponds with one full step of the shaft 2t. The escapement wheel is permitted to advance one-half step at a time by a suitable pallet 2G actuated by stepping magnets M and M-L The shaft 2B rotates clock-wise in the direction indicated by the arrow 93.

Fixed to the shaft 2D are eight contact arms 25-32, which are arranged to engage stationary contacts, spaced in a circle around the shaft in the different positions of the shaft. The first few full steps or station selecting positions of these arms are shown in dotted lines. These arms are each connected to wires, the wires being shown as running directly to the arms, but in practice this electric connection would be made through suitable slip rings or the like.

For each station of the system, the equipment in the dispatchers office comprises a group or bank of channel circuit selecting relays. Such a bank of five relays Ila-5a is shown in Fig. 1 for the first station A nearest the dispatchers oflice. A similar bank of relays, not shown, is located in the dispatchers ofiice for each of the stations of the system.

The channel circuit selecting relays, as Iii-5a, for each station set up channel circuits for the energization of the OS relay l and several other indication relays of the same dead-beat polar type, such as 35, 36, 31, and 38, which control the lighting of lamps N and R, associated with the switch machine lever SM to indicate the position of the switch, other lamps E and W, to indicate the direction of traffic set up, either east-bound or west-bound, and a lamp ST, to indicate that the signals are held in the stop position. The circuits by which these lamps are controlled by the contact fingers 4I, 42, 43, and 134 ofthe respective indication relays 35-38, may be readily traced on the drawings from one terminal Vof a battery or other suitable source of current indicated by the symbol (-1-), and the .other terminal of that same source, indicated by the symbol Also associated with each station, in the particular embodiment of the invention shown, is a rotary code wheel CW, which is in the general form of a simple contact drum, arranged to be driven at the proper speed through a suitable friction clutch 45 and small electric motor 46. For simplicity, this drum is shown developed, and comprises iive rows of contacts, lll-5l, and two continuous contact strips 52 and 53, all suitably secured to the drum of insulating material, and electrically connected together as indicated. As the drum of this code wheel CW rotates, the contacts move from left to right, in the direction indicated by the arrow y, and the contacts in each row engage a stationary contact ringer, indicated as an arrow, respectively connected to wires 554-58. The two continuous strips 52 and 53 are respectively connected through brushes or contact fingers and wires 59 and 60 to the positive and negative terminals of the batteries Si, having a midpoint connected to common, these terminals being marked (B+) and (I3-) The rst contact in each of the rows 41-5|,.that is, all of the contacts in the right hand vertical column, are connected together and to the strip 52. The second contacts of the rows are connected together and to the other strip 55, and so on, so that contacts in each row are alternately connected to (B+) and (B-). In the row 41 of contacts, the rst contact engaged by the cooperating brush connected to wire 58, is longer than the others. In the next row 48, the second contact-is longer lthan the others, in the next row 49 the long contact is the third, and so on, making five code combinations or patterns, each of a long impulse and four short impulses, with the long impulses at a diierent point in the patterns, as will be obvious.

The code wheel CW is normally held at rest in the position shown by a spring engaged latch or detent 62 engaging a projecting stop 63 on the drum of the code wheel; and this latch 62 is retracted to release the drum and permit it to be rotated by the motor 46, when a code starting magnet CS is energized. Associated with the magnet CS is a relay 64, for the purpose hereinafter explained.

Also associated with each station is a lever relay L, and a manually operable push-button or key SK, having two contact fingers 65 and 66.

The equipment for the dispatchers oice also includes a starting relay G, relays O and P, and a check push-button or key CK.

The system employs four line wires, extending from vthe dispatchers omce through the territory equipped, which comprise a common wire C, a signal or message line SGL, a stepping line STL, and a station selecting line SS. In the dispatchers oice, the common wire C is connected to the midpoint of thebattery 6|, and to the circuits at the points designated by the symbol C. The signal lineSGL is .connected to the contact arm 3l on the shaft 20. The stepping line STL is connected to a line relay LRa in the dispatchers oice and to the arm 30. VThis line relay LR.e is of the quick acting polar type, with its armature biased to the neutral position. VThe .station selO and thence to the arm 2.5.

Station equipment-Fig. 2 shows the ,equipment representative or `typical of a station `atene end of a passing siding PS, corresponding to the passing siding ps of the track diagram in the dispatchers oice, shown in Fig. 1. Fig. 3 shows certain parts and circuits for two other stations B and C, the parts of the complete station equipment shown at these stations being those relating to station selection.

In the typical example of a station equipment which has been selected to be shown at station A, Fig. 2, it is contemplated that the system will provide for the control of a suitable power operated switch at the end of the passing siding, and the clearing of the four signals 'l0-lg, subject to the control of the usual block signal system, and also for transmitting to the Ydispatchefs office indications of the occupied or unoccupied condition of the usual detector track circuit at the end of the siding, having a track relay T, and also indications of the positions of the switch, the clearing of the signals, and the direction or traffic set up.

For the purpose of indicating .the position of the switch, the switch machine SW, connected to and operating the switch points in the usual way, is provided with contact members l@ and l5, operated to an intermediate open position while the switch machine is operating, and to one vcxtreme circuit closing position or the other, when the switch machine has operated the switch Vpoints to the corresponding Ynormal or reverse A pair of position, and has locked the points. contact arms 'i6 and 'l1 are also operated by the switch machine SW to three different positions, into engagement with contacts shown conventionally, said arms assuming one extremeposition or the other when the switch points are over and locked in corresponding position, and assuming the intermediate position while the switch machine is operating.

Associated with each of the four signals ll-"l is a suitable circuit controller, shown conve-n .g

tionally, which is closed when the corresponding signal is cleared. For simpliiication, two position semaphore signals have been shown, and these signal circuit controllers 'iS-Sl are operated by the semaphores in the usual way. If either of the signals 'it or l, governing east-bound traic, is cleared, and its circuit controller i8 cr 19 is closed, a circuit is established for energizing a relay ER. Similarly, the clearing ci either of the signals 12 or 'I34 governing west-bound z trac energizes a relay WB. The energizing circuits for these relays may be readily traced on the drawings.

Each station equipment also includes a bank of channel circuit selecting relays 4 5, and a bank of code responsive relays ll-l5, ve having been shown as suitable for the particular application of the invention assumed. At each station is a line relay LR included in the stepping line STL, and a slow pick-up relay SL, controlled by said line relay. Also, at each station is a station relay S included in the station selecting line circuit SS; and associated with each station relay S are'two or more station counting relays a, b, etc.,

and a slow pick-up relay SP. At the first station counting relay at each succeeding' station than at the next preceding station, in accordance with the distance from the dispatchers office. The energization of the next to the last counting relay in the series at each station, in the manner hereinafter explained, selects that station and establishes communication between it alone and the dispatchers oiice.

Operation The parts are shown in the drawings in the normal or inactive position, with the system not operating, and on the assumption that the switch at station A is in the reverse position, while the four signals 'l0-13 at that station are all held at stop.

In this inactive condition, the shaft 29 of the station selector F is held stationary by the pallet 24 and escapement wheel 23, the motor 2| being running and the friction clutch 22 slipping. The stepping line STL is de-energized, and the line relay LRa in the dispatchers oilice and the line relays LR at the several stations are all deenergized and their contact fingers are in the neutral or intermediate position. The station selecting line SS is energized from negative (B-) through the back contact 84 of the starting relay G, Wire 85, contact arm 25 in the normal position, Wire 86, and relay O. The station relays S, which are in series, at all of the stations are likewise energized negatively, moving their contact fingers 81 and 89 to the left, and energizing the relay SP at that station through a circuit readily traced on the drawings through the contact iinger 88.

The code wheels CW for all of the stations in the disp-atchers omce are held in the initial position by the latches |32, but the motor it is running and slipping the clutches 55. The channel selecting relays ifi-5a inthe dispatchers office for station A and for all of the other stations, are all cle-energized; and similarly the channel circuit selecting relays` |5 at station A and at all the other stations are de-energized.

At station A, Fig. 2, on the assumption that the signal lever SG for that station was in the middle position shown during the last operation of the system, the code responsive relay I! is energized, while all of the other relays I2|5 are de-energized. The code responsive relay I I is thus maintained energized by a stick circuit from through its front contact |99 and its lower Winding; and through the back contacts IIlI, |92, |93, and |94 of the other coole responsive relays I 2-|5. This relay I beingl energized, opens its back contacts H5 and ||6, and breaks the clearing circuits for the signals 1li-13,' so that these signals are held at stop, irrespective of traflic conditions.

Automatic staTtz'ng.-The system, when thus at rest, is automatically set into operation by the operation of any track relay. When thus set into operation automatically by a track relay operation, the system automatically sets up all of the channel circuits for ali of the stations and transmits all of the code controls. This may be said to be a complete scanning or checking of all the controls and indications.

To explain this operation in detail, for convenience assume that a train enters the detector track circuit at the passing siding PS in Fig. 2, dropping the track relay T, which closes its makebefore-break contacts IIli and energizes a repeater relay TR. The relay TR is stuck up through its front contact I I I, wire I I2, and back contact IIS of the channel circuit selecting relay 5. The relay is picked up and stuck up in the same way when the track relay T picks up.

The energization of the relay TR closes its front contact I I4 and establishes a starting channel circuit through the lower winding of the starting relay G in the dispatcherss office, which may be traced as folloWs:-starting at C, front contact IIB of relay TR, wire ||5, back contact H9 of relay I, Wire ||1, back contact ||8 of relay 2, Wire II9, back contact |29 of relay 3, wire i2I, back contact |22 of relay 4, Wire 23, back contact |22 of relay 5, wires |25 and |26, front contact 96 of relay SP, wires |21 and |28, to the signal line SGL, and thence to the dispatchers oilice, arm 3|, wire |29, lower winding of relay G to (B Since the relay SP at each station is energized, there is a similar starting channel circuit for each station, so that if the track relay T at any other station should drop', or pick up, the resultant energization of the relay TR at that station would cause the energization of the starting relay G.

The energization of the starting relay G opens its back contact 84 to de-energize the relay O and the station selecting line SS. This de-energizes the relay S at the several stations, causing their contact lingers 81 and 88 to assume the neutral position. This de-energizes the relay SP at each station. The closing of the front contact |30 of the relay G connects positive (Jr) to the wire |3|, thence over wire |32, contact arm 29, wire |33, back contact |34 of the relay P, wire |35, to the stepping magnet M-I and thence to When the step-ping magnet M is de-energized by the dropping of the relay O, the magnet M-I shifts the pallet 2li to permit the shaft 29 to advance one half -step, whereupon (B+) is applied through contact arm 25 (now in the rst half-step position) to the station selecting line SS, again energizing the relay O, which in turn energizes the stepping magnet M, and allows the shaft 29 to make another half-step, bringing it into the rst full step station selecting position, shown in dotted lines.

During the time required for the slow acting relay O to pick up its armature and cause energization of the stepping magnet M, a positive impulse is maintained on the station selecting line SS, which moves the contact fingers 81 and 88 of the station relay S at each station to the right. This energizes the first counting relay a at each station. At station A, the counting relay a is energized over a circuit from wires 89 and 99, relay a, wire 9|, and back contact 92 of the counting relay b to A stick circuit for the counting relay a is established from J,-) through its front contact 93, wires 94 and 99, relay a, Wire 9|, back contact 92 of relay b to At station B, the pick-up and stick circuits for the counting relay a1 are similar and include a back contact 921 of the third counting relay c. At station C, the pick-up and stick circuits for the counting relay a. includes the back contact 922 of the fourth counting relay d; and in the same way, the rst counting relay a at each station is picked up by this positive impulse, and is stuck up through the back Contact of the last counting relay at that station.

Each station is selected or rendered effective by the closing of front contacts 91, 98, and 99, which are operated by the next to the last counting relay at that station. At station A, these contacts 91, 98, and 99 are operated by the counting relay a, at station B by the counting relay b, and so on. The closing of the front contact 91 completes the energizing circuit for the slow pick-up relay SL at the corresponding station; the closing of the iront contact 98 connects positive to upper contact linger oi the line relay LR; and the closing of the front contact 99 connects the signal lineSGL to the channel circuits at the corresponding station.

Code transmission and channel circuit selection- With the shaft 2i! of the stationselector F in the first station selecting position, corresponding to station A, a circuit is established for energizing the Vcode starting magnet CS for that station from through the back Contact |36 of the relay P, wire |37, arm 26 (now in its rst step position), wires |38 and |39, back contact |48 of the relay 55, wires lili and |42, magnet CS, wires |43 and Mil, relay 64, to The energization of the magnet CS retracts the latch |32 and permits the motor 5 to drive the drum of the code wheel CW at the proper rate. After a time sui'licient to release the latch 82, the relay'5fl attracts its armature and breaks the energizing circuit for the magnet CS just traced at the back contact M8 of the relay 84, so that the latch 62 is retracted by its spring into position to stop the code Wheel CW after one revolution. The relay ifi when once energized, is maintained energized as long as Contact arm 26 remains in the rst station selecting position by a stick circuit from( relay 56, wires |44 and |45, front contact lili! of relay 64, wires |38 and |33, arm 2.5, wire i37, back contact |55 of relay P to The contact Uli) oi the relay @l is preferably make-beiore-break.

Assuming the levers SM and SG for station A to be in the position shown in Fig. l., as the code Wheel CW rotates, positive and negative impulses are applied to the stepping line STL by the lower row of contacts t7, the iirst impulse being a long impulse. This circuit for energizing the stepping line STL may be traced from the contacts in the lower row 47, energized with (B+) and (B alternately, to the iinger engaging this lower row of contacts, wire 58, contact finger i8 oi lever SG in the middleY position, wire |55, arm 3|) in the rst station selecting position, wire |47, line relay LRa to the stepping line STL, and thence through the line relays LR in series for several stations, common wire C, and back to the battery 6|.

Thus, the line relay LR21V in the Vdispatchers oce, and all oi the line relaysA LR, LRl, etc., at the several stations are energized by alternate and impulses. While the line relays LR at all of the stations are operated, only the one at the first station A is eiective to cause any operation, because it is only at this station that the contacts 97 and S8 are closed, these contacts being associated with the station counting relay a at this rst station A, but not with the counting relay a at any other station. Similarly, the line relay LR=L in the dispatchers oice, altl-,ough connected to the banks of channel circuit selecting relays for all of the stations over the bus lines E58 and M8, operates these relays for the rst station A only, because the relays for that station iii-5e are the only ones' connected through the 32 on the shaft 25 to operation oi the bank of channel circuit selecting relays ifi-5a in the dispatchers ofilce for station A, and the relays 5 at station A, in response to the energization of the line relays LRE' and LR by the impulses applied to the stepping line circuit STL, is the saine for both banks of relays, and a description of one will. serve for both. Referring to Fig. 2, when the line relay LR is energized with a positive impulse, it moves its contact ngers and 15| -to the right, and with a negative impulse to the left. The contact finger |50 is connected to positive (-1-) over Y wire |52 and through the 'front contact 98 of the relay a.

On the first positive impulse on the stepping line STL, current from (-1-) is supplied, with the contact fingers E55 of the line relay LR to the right, over wires E55 and |54, back Contact 2.511v of relay 2, Wires |55 and |55 to the relay l, thence over wire |57, back Contact |58 of relay 2, Wires 5i! and |68, back contact |5| of relay 3, wires |62 and |E3,back contact |55 of relay 4, Wires |65 and |66, back contact |57 of relay 5, and thence to This picks up the relay i, which is at once stuck up through its front contact |58, wires |69 and |56, relay l and thence to along the same path above traced.

in the case assumed, the rst positive impulse being a long impulse, the Contact finger |5| of the line relay LR is held in its right hand position long enough to energize the slow pick-up lrelay SL over wire |70, relay SL, wire |7|, front contact 97 oi relay a to CN, indicating the midpoint oi a local battery having its positive and negative terminals connected to the contact finger |5|. A

With the first channel circuit selecting relay at the way station energized by a long impulse, not only is an indication channel circuit set up by the station A in the Ydispatchers oiiice, but also a pick-up circuit for the code responsive relay I is established. This pick-up circuit for the relay may be traced as follows: commencing at (-1-), front contact |12 of the relay SL, wires |73, |74, |75, |76, and |77, front contact |78 of relay now closed, wire |79, upper winding of relay to The long impulse, which is positive in the case assumed, is made oi sufficient duration to pickup the relay SL and energize a code responsive relay, as relay and permit another code responsive relay to drop and close its back contacts.

The indication channel circuit set up upon the energization of the relays and |21, which as shown is used to energize the indication relay 38 may be traced as follows: commencing at C, relay 38y (see Fig. 1), wire |8il, front contact |8| of relay la now closed, Wire |82, back contact |83 of relay 2e, wire |84, back contact |85 of relay 3a, wire |85, back contact |87 of relay lia, wire |88, back contact |89 of relay 5a, wire |98, arm 3| in the iirst station selecting position, toI the signal line SGL, thence to station A (see Fig. 2) then over wires 28, |S|, front contact 99 of relay a, wires |82, and l25, back contact |24 of relay 5, wire |23, back contact |22 of relay ll, Wire |2|, back contact |26 of relay 3, wire E9, back contact l i8 of relay 2, Wire l il, iront contact i6 of relay now closed, wire |93,back Contact |94 of relay ER, wire |95, back contact |96 of relay WR, to (B The relay Y38 being thus negatively energized moves its contact finger ill to the left to light the lamp ST, indicating that the signals are at stop. Ii any one of the signals lil-73 should be in a clear position, closing its corresponding circuit controller 78-8|, one or the other oi the relays ER or WR would be energized, energizing the relay 38 positively and extinguishing the lamp ST.

Upon the next negative impulse applied to the stepping line STL the relays 2'rl and 2 are energ'i'zed. This negative impulse shifts the contact inger I50`of the line relay LR to the left and applies current from wires |97, |98 and |99 (see Fig. 2), to the front contact 200 of relay I now closed, wires 20| and 202, relay 2, wires 203 and I 60, and thence through the back contacts of relays 3, 4, and 5 to the same as in the er1- er-gizing circuit for the relay I hereinbefore traced. The relay 2, when energized, is stuck up in the same way as relay I; and when relay 2 picks up, its back Contact |58 breaks both the pick-up and stick circuits for the relay I, so that this relay is de-energized and remains de-energized.

This energization of the relay 2 closes a second channel circuit for energizing the indication relay 31, which is similar to the channel circuit previously traced, and need not be traced in detail. This second channel circuit is connected to the contact nger 204 of relay ER, the front and back contacts of which are connected respectively to contact iingers 205 and 206 of the relay WR. If one of the east-bound signals 'I0 or II is cleared, the relay ER is energized, closing its front contact 204; and if the west-bound signals 12 and 'I3 are at stop, the relay WR is de-energized, closing its back contact 205, whereby the indication relay 3l is energized positively to move its finger 43 to the right and light the lamp E. On the other hand, if the west-bound signals are clear, the relay 3'I is energized negatively to light the lamp W.

In a similar way, the third impulse, which is positive, energizes the relays 3 and 3a, establishing a third channel circuit for the indication relay 35. The fourth impulse, which is negative, energizes the relays 4 and 4e, and establishes a channel circuit for the indication relay 35. Finally, the fth impulse, which is positive, energizes the relays 5 and 5a and establishes a channel circuit for the OS relay 'I. The last relay 5 or 5a of these banks of channel circuit selecting relays is not stuck up, but is held up so long as the stepping line STL is energized, the front contact 228 of the preceding relay 4 or 4a, which is deenergized upon energization of the last relay 5 or 5u by the opening of its back contact |61, being shunted by the front contact 229 of the last relay 5 or 5a.

The desired indications are communicated over these channel circuits by energizing the corresponding indication relays positively or negatively. Thus, if the switch is in the reverse position, as shown, the indication relay 35 (Fig. 1) is energized positively through the contact I6 (Fig. 2) to extinguish the light N, while the indication relay 35 is energized negatively, through contact Ti, to light the lamp R. While the switch is operating both of the relays 35 and 30 are energized positively to extinguiish both lamps R and N; and when the switch is in the normal position, the relay 35 is energized positively to eX- tinguish the lamp R, while the relay 35 is energized negatively to light the lamp N. In a similar way, if the track relay T is energized and its contact nger 207 raised, the OS relay 'l' is energized negatively to extinguish the OS lamp 6, while with the track relay T down, the relay 1 is energized positively to light the OS lamp 6.

All of these channel circuits, over which these indications are transmitted, include the front contact 99 of the counting relay a at station A, the contact siii of the counting relay b at station B, and so on, so that the channel circuits at each station are not connected to the signal line SGL unless that station is selected by the energization of its corresponding counting relay a, b, etc. Similarly, in the dispatchers office the several channel circuits for each station through the bank of channel circuit selecting relays for that station, such as the relays Iii-5a shown for station A in Fig. 1, are connected through the arm 3| of the station selector F to the signal line SGL only when that station is selected. Consequently, the channel circuits for the dilerent stations are isolated both at the stations and in the dispatchers oiiice; and if any channel circuit connection should happen to be improperly set up, due to the sticking of a relay or the like, the effect of such failure is confined to the particular station aiected and does not interfere with the proper transmission of indications over the channel circuits for other stations. This is a desirable feature, characteristic of systems involving station selection, because such channel circuit failures as may occasionally occur are localized and conned to the station aiected, and do not cripple the whole system, as may happen in selecting systems of the synchronous type where all of the channel circuits are directly connected to the signal line, so that any channel circuit improperly set up may interfere with all of the other channel circuits.

If the levers SM and SG for station A in the dispatchers oce had been set in some other position at the time of the operation of the code wheel CW and the relays |-5 and Ia-Ea, as just described, the impulses applied to the stepping line STL would be of a different code pattern, and a different one of the code responsive relays I2, I3 I4, or l5 would have been energized, instead of the relay II, as assumed. During this operation, the indication channel circuits would have been set up in the same way.

The code controls, which may be transmitted by the code wheel CW, depending on the position of levers SM and SG, are selected so that, by a single code transmitted, the necessary operation of the switch and signals for a given train movement may be obtained as eiectively as if separate codes for operation of the switch and signals were transmitted. There are four normal train movements to be handled at the end of a passing siding, namely, east-bound traffic straight through (switch normal), or into the siding (switch reverse), and west-bound traffio on the main track (switch normal), or from the siding (switch reverse). According to this invention, a distinctive code for each one of these train movements is transmitted, and in response to that code, the switch machine and signals are controlled in a corresponding Way.

As typical of this operation assume that the dispatcher wishes to set the signals and the switch at the passing siding for station A, Fig. 2, for an east-bound train to take the siding. To do this, the dispatcher moves the signal lever SG to the right, assumed to correspond with eastbound traffic, and the switch lever SM to the reverse position shown. This connects the stepping wire STL through arm 30, wire |46, contact finger I8 of the lever SG, wire 208, finger |I of lever SM to wire 51 cooperating with the group of contacts 48, in which the second negative impulse is the long impulse. Accordingly, when the relay 2 at station A is energized by the second impulse, the relay SL is also energized, the second impulse being a long one, and a pick-up circuit for the code responsive relay 2 is established from positive through the front contact tact of each of the other relays.

' previously energized is de-energized.

|12 of the relay SL, wires |13 |14, I'I5, |16, 209, front contact 2|0 of the relay 2 and wire 2|| through the upper winding of the relay I2 to negative. The energization of the relay I2 breaks at its back contact 53| the stick circuit for the relay II, and as soon as this relay drops, a stick circuit through the lower winding of relay I2 is established through the back contact 2I2 of relay II, wire 2I3, front contact 2|4 of relay I2, wire 2|5, lower winding of relay I2, wires ZIS, and thence through the back contacts |32, |93, |94 of the relays I3, I4, I5 to negative The energization of the relay I 2 closes a circuit from through its front contact ZI'I, wires 258, 2| 9 to the switch machine SW, causing it to assume its reverse position, if not already there. Closing the front contact 220 of relay I2 applies current from positive (-1-) over wires 22| and 222, back contact IIB of relay II, wire 223, circuit controller 'I4 in the reverse position, and thence over wire 224 to the signal 'II so that that signal may clear. providing the switch machine is in the corresponding reverse position. In this connection, it should be understood that the control circuits for the signals have been shown running directly to the signals, whereas in practice there would preferably be suitable relays interposed, in the manner shown, for example, in my prior application Ser. No. 199,325, filed June 16, 1927.

If the dispatcher wishes to permit an eastbound train to continue on the main track, he would put his signal lever SG in the right-hand position and his switch lever SM in the normal position, opposite to that shown. This would connect the group of contacts 49 to the stepping line STL, so that the third impulse of the series would be the long one, and the code responsive relay I3 would be energized, controlling the switch machine over wires 225 and 22B and front contact 22'! of the relay I3, to assume the normal position. This energization of the relay I3 applies current to the wire 223, the same as the energization of the relay I2, but the switch being in the normal position, the circuit controller 'I4 is in the other position to permit the other signal IG to clear for the main track.

In a similar way, which need not be described in detail, the dispatcher may set the levers SM and SG for west-bound traiiic `from the siding, whereupon the group of contacts 55 would be connected to the stepping line circuit STL, making the fourth impulse a long one to establish through the front contact of the relay 4 an energizing circuit for the code responsive relay I4, which would cause the switch machine to assume the reverse position and permit the signal 'I3 to clear. For west-bound movement on the main track, the row of-contacts 54 is used, energizing the code responsive relay I5 to place the switch in the normal position and clear the signal l2.

With respect to the code responsive relays i i-I, it will be noted that each has a stick circuit through its lower winding including a back con- Consequently, when any one of these code responsive relays II-i'i is energized through its upper pick-up winding, the stick circuits for all the other relays are broken, and any relay that may have. been In this way the transmission of a new code cancels any condition brought about by the transmission of the previous code, and avoids the necessity of transmitting a cancelling code as well as an operating code for each operation.

Station selection-After the code wheel CW for station A has completed its revolution and transmitted the five impulses, and after the last relay 5c1 has responded, the control is transferred to the next station B.

Referring to Fig. l, when the relay 5a is energized, the closing of vits front contact 23|! establishes a circuit from plus over wire 28|, arm 29, of the shaft F in the rst station position, wire |33, back contact |34 of relay P, Wire |35, stepping magnet M- I to This energization of the stepping magnet M-I advances the shaft 26 one half-step, where the arm 25 engages the contact connected to (B thereby energizing the station relays S at all of the stations negatively to cause their contact fingers 8'I and 88 to move to the left. This establishes an energizing circuit for the counting relay b at station A over Wire 239, front contact 23| of relay a, Wires 232 and 233, relay b, to The second counting relay b at each of the other stations is also energized over a similar circuit.

The energization of relay b and the opening of its back Contact 92 interrupts both the pick-up and stick circuits for the relay a at the rst station A, so that this relay a is de-energized at this station and remains de-energized. The relay a is de-energized in a similar way at all of the other stations upon energization of the relay b. At station A, the relay b is stuck up through the back contact 95 of the relay SP, wire 234, front contact 235 or" relay b, wires 236 and 233, relay b and At station B, see Fig. 3, the relay b1 is stuck up through the back contact 921 of the relay c1. At station C, the relayb2 is stuck up through the back contact 922 of the next countlng relay d2. The same process is continued for the remaining stations, the pick-up and stick circuits for all of the counting relays at each station, except the last one, being taken through the back contact oi the last one, and the last counting relay l being stuck up through the back contact 95 of the relay SP at that station.

At station B the contacts 971, 931, and 991, determining the eiiective control 01' the line relay LRl at that station, the operation of the relay SL at that station, and connecting the signal line SGL at that station to the contact nger |24 of the relay 5 at that station, are all associated with the relay b1, so that when this relay b1 is energized as just described, station B is then selected.

After the signal selecting line SS has been energized with a negative impulse to select station B, long enough to assure operation of the quick acting counting relays b at the several stations, but not long enough to pick up the slow relay SP, the relay O closes its front contact and energizes the stepping magnetv M to advance the shaft 20 another half-step and bring it into the second station B selecting position. In this position, the code wheel CW for station B is operated, and the control codes and indications are transmitted in the same Way described for station A.

After the channel circuit selection and code transmission for the second station B has taken place, and the last channel circuit relay for station B, corresponding to the relay 5a, has operated, the stepping magnet M -I is energized over a circuit through the contact arm 29, which is similar to the circuit including wire 28| and front contact 289 of relay'a, whereupon the shaft ZI! advances another half-step, and a positive impulse is applied over arm 25 to the station selecting line SS.

This posltive impulse does nothing at station A,

since the relay a can not be picked up, relay b is stuck up, and there is no relay c; but at station B and the other stations, the counting relay c is energized, dropping the counting relays b at all stations except station A. The dropping of relay b at station B opens contacts 911, 981, 991, disconnecting that station; but at station C the contacts 972, 982 and 992 are associated with the relay c, so that communication is now established to station C. After the channel circuits and code controls for station C have been transmitted, the shaft 25 advances another half-step, station selector line SS is again energized with another impulse, this time of the opposite polarity, namely negative, which energizes the next counting relay d at station C and the remaining stations; and this same operation is repeated until the shaft 20 has completed a revolution.

The arm 25 on the shaft 28, during the last part of its movement to its initial position, applies a long negative impulse to the station selecting wire SS, which picks up the relays SP at all of the stations and breaks the stick circuit for the last counting relay at that station, whereupon the counting relays at all the stations are de-energized, the starting channel circuits are established, and the system is ready for another operation.

Since the track relays T at the several stations may drop or pick up at various times as trains enter and leave the corresponding track sections, it may happen that a track relay will pick up or drop at a station while the system is operating, but after the corresponding station has been selected and the channel circuits therefor have been set up. It is necessary, therefore, in order that such OS indication may not be skipped, to keep the system in operation, when once started, until all of the new OS indications have been transmitted or cleared out. To accomplish this, provision is made so that Whenever the relay TR at any station is energized by dropping or picking up of the corresponding track relay T, it is held up through its stick circuit until the last channel circuit selecting relay, as 5, at that station has been energized to open its back contact H3. At the end of each revolution of the station selector shaft if the relay TR at any station is still energized, due to a change in the track relay at that station which has not been indicated to the dispatchers oice by a previous operation of the channel circuit selecting relays at that station, then the starting relay G is energized in the same way as hereinbefore explained, to assure another revolution of the shaft 2B; and this operation continues until all new OS indications have been communicated to the dispatchers o'ice.

Manual starting-The system, when inactive, may also be set into operation manually by the dispatcher, either to obtain a check upon the eX- isting conditions, or for the purpose of transmitting a new control. To do this, the dispatcher depresses the checking key CK, which energizes the upper winding of the relay G, directly from (-i-) over wire 231, relay G, wire 238, arm 32 to and causes the system to carry out the operation of scanning all indications and transmitting all code controls, in the same way as if the system had been set into operation by a track relay T.

The dispatcher may, if he desires, use this checking key CK to start the system into operation, after he has shifted from one or more of the control levers SM or SG to a new operated position; but since in that case, all of the channel circuits for all of the stations previous to the one for which a new lever movement had been made, would have to be set up, it is proposed to organize the system such that the station selection Will take place quickly, Without setting up the channel circuits or transmitting the code controls until the station is reached at which a new code control is to be transmitted.

To understand this feature of manual manipulation, assume that the dispatcher puts the levers SM and SG for a given station in a new position and then presses the particular key SK for that station. The closing of the contacts 65 of the key SK picks up the lever relay L, which is stuck up through its front contact 240, wire 24|, and back contact 280 of the corresponding last channel circuit selecting relay, as H. 'I'he closing of the front contact 242 of the relay L applies positive current over wire 243 to a bus 244, which is connected to the relay P. 'I'he energization of the bus 244 also energizes the upper Winding of the starting relay G over wire 245, checking key CK normal, wire 231, upper winding of the relay G, and to over wire 238 and arm 32.

The station selector shaft 20 is now started in the same way as previously described. Upon reaching the i'lrst station selecting position, remembering that the relay P is energized, if the relay L for that station is fle-energized, a circuit for energizing the stepping magnet M-l is established from over the back contact 242 of relay L for the station in question, wire 241, Contact arm 28, in the position corresponding to that station, wire 248, front contact |34 of relay P, wire I 35, magnet M--l to The energization of the magnet M-l advances the shaft 20 one half-step in the same way as previously explained, which in turn results in the energization of the station selecting line SS, and then transfers to the next station. This same operation is repeated until the station is reached at which the relay L is energized.

When the station selector shaft 20 reaches a station selecting position where the relay L is energized, the neXt energizing circuit for the stepping magnet M-l, through the front contact |34 of the relay P, is open at the back contact 242 of the relay L, so that the shaft 20 is stopped in the selecting position for the station in question. When the relays P and L are both energized, a circuit for energizing the code starting magnet CS is established from (-1-) through the front contact |36 of relay P, wire 249, arm 21, wire 258, front contact 25| of relay L, wire |39 along the regular energizing circuit for the magnet CS previously traced.' This starts the code wheel CW for the station in question and sets up the channel circuits and transmits the new control code in the same way already explained.

When the last relay, as 5a, for the selected station under consideration is energized, it breaks at its back contact 28|! the stick circuit for the relay L, so that this relay is rie-energized, assuming that the dispatcher has restored the key SK. When the lever relay L, which is quick acting, is cle-energized in this way, an energizing circuit for the stepping magnet M-I is established from through the back contact 242 of the lever relay L, wire 241, arm 28, wire 248, front Contact |34, of the relay P, wire |35, magnet M-l, to This advances the shaft 20 another half-step, bringing it into position where the station selecting wire SS is energized over arm 25, to bring about selection of the next station.

If the particular lever relay L under consideration is the only one for the several stations which is energized, then upon dropping of this relay L, the bus 244 is no longer energized and the relay P drops, so that, when the Shaft 2|) has been advanced to select the next station, the stepping magnet M| must be energized through the back contact |34 of the relay P, arm 29, wire 28|, and the front Contact 280 of the last channel circuit selecting relay, as 5a. Consequently, when this next station is selected, the channel circuits therefor are set up, before the next station after that is selected, and the same is true of succeeding stations. In other words, after the channel circuits for the station, at which the lever relay L is energized, have been selected, the system assumes its ordinary or normal condition for scanning all of the channel circuits. The relay P is preferably made slow releasing, so that upon dropping of the lever relay L, the stepping magnet M-l may be energized to advance the shaft 2|), before the relay P opens the energizing circuit for this stepping magnet at the front Contact |35.

The dispatcher, however, may set the control levers to different positions for any desired number of stations and operate the key SK at several stations. When this happens, the system passes quickly from station to station, starting with the rst station A nearest dispatchers oice, without setting up the channel circuits, until the irst station is reached, where the key SK has been depressed, whereupon the channel circuits for that station are set up and the code controls transmitted, after which the relay L for that station is de-energized. Upon de-energization of this relay L, the bus 244 and the relay P are maintained energized by the relay L at the one or more other stations, at which the key SK has been operated, so that the stepping magnet M|, is at once energized as soon as the shaft 2|) advances to each next station selecting position in turn, causing rapid station selection until the next station is reached where the relay L is energized. Upon coming to such station, where the relay L is energized, the channel circuits for that station are set up, and then the system either continues its rapid station selection, or else is restored to its normal condition for scanning all of the channel circuits at the remaining stations, depending upon whether or not there is any other relay L energized.

In this way, the normal operation of Setting up all of the channel circuits and transmitting all of the control codes, is rendered ineffective or discontinued, when the dispatcher operates one or more of the keys SK; and when thus manually controlled, the system operates to select the stations quickly, without setting up the channel circuits therefor, except for the station or stations at which the key SK has been operated, whereupon the system is restored to its normal condition for setting up all of the channel circuits and transmitting all of the code controls. If a track relay should drop or pick up at some one or more of the stations, at which the key SK has not been operated, after the revolution of the station selector shaft 2D, during which the manual intervention occurred, such change in the condition of these relays causes energization of the starting relay G and assures another revolution of the station selector shaft to clear out the new OS indications. Likewise,

if a key SK is operated, while the system is operating, and the station for that key happens to be one which has already been passed in the process of station selection, the shaft 20 of the station selector F automatically makes another revolution, to transmit the code controls for the station associated with such operated key SK, because at the end of the revolution of the shaft 25 and cycle of station selection, the upper winding of the starting relay G is energized from the bus 254, which remains energized because there is a lever relay L still energized.

If the system is operating at the time the dispatcher depresses the key SK for some one of the stations, the relay P is energized, and the system thereafter transfers quickly from station to station, without setting up the channel circuits for the stations, until the station, corresponding to the key SK which has been operated, has been reached. In other words, whether the system is at rest or is operating at the time the dispatcher actuates a key SK for a given station, communication to that given station is established as quickly as the Station selection can be accomplished, the automatic scanning of the indications to be transmitted to the dispatchers office being for the timebeing subordinated to the manual control. Putting it another way, the system normally acts, whenever set into operation from the field, to scan all of the indications and transmit code controls to check the existing positions of the various control levers, but the dispatcher may at any time intervene with a manual operation which cuts out this automatic scanning and establishes without delay communication to the station or stations which the dispatcher has selected.

Manually holding a. selected station.-In order that the dispatcher may, if he wishes, limit the channel circuit selection to a particular station, provision is made so that, if the dispatcher holds down the key SK for a given station, the code wheel CW for that station continues to rotate, and the bank of channel circuit selecting relays for that station operate repeatedly as long as this key is kept depressed. The closing of the contact of the key SK maintains the relay L energized, independently of its stick circuit, and keeps open at its back contact 242 the circuit through the arm 28 and front contact |35 of the relay P, by which the stepping magnet M| is energized. Consequently, as long as the key SK is held down, the shaft 20 of the station selector F is held in the corresponding station selecting position. The closing of the contact 65 of the key SK establishes a shunt over wires 252 and 253 around the back contact |40 of the relay 64, so that the code starting magnet CS is maintained energized, and the code wheel CW continues to revolve as long as the key SK is held down. This continued rotation of the code wheel CW operates repeatedly the banks of channel circuit selecting relay as ifi-5a and |-5 for the corresponding station.

In this way, the dispatcher may coni-ine com.- munication with any selected station, and will obtain prompt response at that station to the operation of the control levers SM and SG for that station, and likewise prompt transmission of the indications of the condition of the detector track section, position of the switch machine, and indications of the signals.

When the dispatcher releases the key SK, the y code wheel CW is stopped by the latch 52 in its initial position, and when the last channel selecting relay, as 5a has responded the stepping magnet lVi-l is energized, and the next station is selected.

While in the illustrative embodiment of the invention shown, a station is assumed to be one end of a passing siding, in many instances in practice-it is preferable. to organize the system so that both ends of a passing siding or some other zone o1' portion of the equipped territory, will constitute a station. For example, in making a nonstop meet, the dispatcherfshould be in communication with both ends of a passing siding so as to be advised promptly when the expected trains arrive at the respective ends of the passing sidings, in order that he can change the position of the switches and indications of thel signals promptly to permit the trains to pass each other without stopping. Accordingly, a station in the sense here used, may include a plurality of separated control points along the track, such as the two ends of a passing siding, and in general Vsigniiies that particular portion or zone ln the control territory with which the dispatcher may elect to hold communication as a whole, for the purpose of obtaining prompt response to lever operations and changes in track circuit occupancy for all points in that zone. In such cases, where the station comprises the two ends of a passing siding or similarly separated control points along the track, a bank of channel circuit selecting relays, such as the relays l-5, are preferably located at each end of the passing siding, or at the corresponding local control points, so as to avoid long runs of line wire from the various switches, signals, track relays, and the like, to one bank of channel selecting relays at the diierent points in the zone or territory constituting a station are operated simultaneou'sly, and must have a capacity for all of the channel circuits for that station. A line relay LR. is located near each of these banks of channel selecting relays, and also a station relay S and a group of counting relays a, b, etc., the group of counting'relays at each one of these points being the same, so Ythat the line relays at these points arey simultaneously effective to operate the banks of channel circuit selecting relays at these points. The bank of channel circuit selecting relays in the dispatchers oice, such as the relays I-5, mustl of course be of a number to take care of all of the channel circuits for the territory or zone constituting the station, and the code wheel CW must be similarly provided with the necessary number of contacts.

In this connection, it will be evident that, by increasing the number of channel circuit selecting relays, such as the relays I-5, following the same plan of control, and by providing a sufficient number of contacts on the code wheel to operate these relays, any desired number of channel circuits and code controls may be provided for any station. In fact, after an installation has been made, it is easy to add in additional indication or control for any station by merely adding another channel circuit selecting relay and contact on the code wheel for that station. The ve channel circuit selecting relays shown are merely typical of what is ordinarily required for one end of a passing siding, but any desired number of relays may be used to fit any number of switches, signals, track relays, and the like,

for any desired zone or territory.

In the arrangement hereinbefore described, since it may take several seconds for the switch machine to respond to a new control, the indication of the changed position of the switch may not be transmitted until some revolution of the station selector F subsequent to the revolution during which the control for the switch was transmitted. The dispatcher may hold down the key SK for a given station, until the indication of the response oi the switch or signals to a new control has been received, or may keep the sys-` t'ein, in operation by the key CK, until the desired indications have been received. To avoid the need for such manual manipulation on the part of the dispatcher, I preferably employ the arrangement of circuits for controlling the starting of the system shown in Fig. 4, which to avoid confusionrlias not been shown in Fig. 2.

Referring to Fig. 4, the relays ER and WR. responding to the changes in the indications of the signals l0- '13 are provided with Suitable make-beiore- break contacts 262 and 263, which are momentarily closed when these relays are energized or de-energized. 'A contact 264, operated by the switch machine, reverses the polarity of the energizing current for a neutral relay 265-, after the switch is operated to its extreme positions; and this relay 265 operates similar make-before-break contacts 266, the armature of this relay momentarily dropping during the reversal of the polarity of the current flowing in its windings. These contacts 262, 263 and 266'are connected in multiple With the contact H0, operated by the track relay T, to close an energizing circuit for a relay X, so that this relay X is energized whenever there is a change in the operated condition of the track circuit, the switch, or the signals. The relay X has a stick circuit including its front contact 261, wire 268, and back'contact 269 of the relay SP shown in Fig. 1. The closing of the front contact 216 of the relayX energizes the relay TR, shown in Fig. 2, which is stuck up in the same way through back contact H3 of the relay 5.

With this arrangement, whenever there is a change in the operated condition of the track relays, switch machine, or signals, the relay X is energized, and in turn the relay TR., establishing the same starting circuit hereinbefore explained. If this change takes place while the system is inactive in its initial condition, the relay SP being energized, the relay X picks up and drops while the relay TR is held energized until the bank of relays |-5 for the station in question has been operated. Since this change in the operated condition of the track relay, switch machine, or signals, may take place while the system is operating, and at any time in its cycle of operation, and perhaps after the channel circuit selecting relays I, 2, 3, or 4 have operated, but prior to the operation of the relay 5, the relay X and its stick circuit are provided, so as to insure at leastone complete cycle of operation following energization of the relay X. If the relay X is energized, while the system is operating it is maintained energized, by its stick circuit, the relay SP being then de-energized. An operation of the relay 5 during this cycle does not de-energize the relay TR, which is held up by its pickup circuit through the front contact 2li) of the relay X. After the cycle of operation under consideration has been completed, and the relay SP isenergized, the relay X drops, setting up'conditions for the relay TR, to drop upon the next 0peration of the channel circuit selecting relay 5.

In this way, one complete cycle of operation of the system 4is assured following any change in the operated condition of the track relay, switch machine, or signals, at any one of the several stations. Consequently, even though the system should automatically stop after the transmission of a control to operate switch or signals at some station, it is automatically started again, as soon as the switch or signal has responded, so as to transmit the indication of the changed condition. Also, if the switch machine or signals at any of the stations is for any reason operated or displaced from the position it last assumed in response to a control by the dispatcher, the system is automatically set into operation and indication of such change is at once communicated to the dispatcher.

From the foregoing it can be seen that this invention provides a communication system for train dispatching or centralized trac control systems, in which positive acting simple relays are .employed for the channel circuit selecting means and code responsive means. These relays can be installed in ordinary relay boxes along the track, and will operate more reliably under the varying conditions of moisture, temperature, and jar and vibration of passing trains, than mechanical selecting devices,

Since the communication between the dispatchers oice and the several stations is established only one station at a time, the channel circult selecting means and code responsive means at each station are operated onlyone at a time, and may be the same at Ythe several stations. yIn other words, a `bank of five channel `circuit selecting relays and five distinctive vcode patterns may be employed without interference at several stations, in marked contrast to a system in which the channel circuit selecting or code responsive devices operate simultaneously at all of the stations, so that the equipment at each station must have the capacity to set up channel circuits distinctive from all other stations and respond to codes distinctive from all other stations.

By employing one long impulse in the series or group of impulses which operate the channel circuit selecting relays, it is possible to obtain distinctive code patterns of impulses, as many in number as the total channel circuit selecting relays, with the result that there is great economy in apparatus and in time of operation, because a number of controls may be transmitted from the dispatchers ofiice and a number of indications received in the dispatchers oice simultaneously with an equal number of channel circuit selecting relays. For example, if ve channel circuit selecting relays are used, as shown, ve distinctive controls may be transmitted from the dispatchers voillce and simultaneously ve distinctive channel circuits are set up over which an equal, or greater number, of indications may be received. In other words, the channel circuit selecting equipment is made to do double duty.

While various schemes of station selection may be employed, such as disclosed, for example, in my prior application, Ser. No. 348,336, iiled March 19, 1929, in the particular scheme herein disclosed, the station selection is accomplished in a simple and reliable way by the sequential operation of neutral counting relays a, bi, etc.; and in this connection, instead of using as many counting relays at each station as there are stations, by provision of the slow pick-up relay SP, energized by a long impulse of one polarity at the end of each cycle of station selection, only two counting relays are required at the first station, three at the next,

four at the next, and so on. Also, the use of thek slow pick-up relay SP and the long impulse at the end of the cycle of station selection provides for automatic synchronization of the station selecting devices, so that any occasional improper operation of the counting relays is automatically corrected, since the long impulse at the end of the cycle of station selection, by energizing the relay SP, de-energ'izes all of the counting relays a, b, etc., at all of the stations, and assures that they willstart 01T together on the next cycle of station selection. i

Another desirable feature of the invention is that the dispatcher may manually select any station or stations without delay, and may promptly transmit a control to, or receive an indication from, such selected station or stations. Also, the dispatcher may confine communication to any selected station for any desired length of time, so that response to lever movements for that station or transmission of OS indications from that station, are not delayed by the setting up of channel circuits or transmission of code controls to the other stations. Consequently, the dispatcher is able from time to time to place himself in practically direct communication with any selected station at any time, as he nds necessary. Under operating conditionsordinarily encountered, the dispatcher can foretell from the position of trains and their running times the siding or other point in his territory where the arrival or departure of trains is next likelyto require a change in the position of switches or indications of signals. For example, a dispatcher can readily determine ahead of time the siding at which it may be possible to make a non-stop meet,

and since he can manually select the station for that siding and coni-lne communication thereto for the time being, he is able to obtain such prompt communication of OS indications and response of the switches or signals to the manipulation of the control levers, that he is able to bring about such a non-stop meet as effectively as if there were direct individual line Wire connection between the dispatchers oice and that siding.

In connection with this feature of manual station selection, it will be evident that the dispatcher is out of touch, so to speak, for the time being with the OS indications from stations other than the one he may have selected; and although the system, as disclosed, automatically operates to scan all of the OS indications, as soon as'the dispatcher discontinues the individual communication to a selected station, in many instances it is desirable to provide means for storing an indication of the dropping or picking up of the track relays in the manner disclosed in my prior application, Ser. No. 348,336, filed March 19, 1929. This storing feature is not disclosed herein in order to avoid complication.

By employing code responsive relays, such as I I--I5, interconnected in the way hereinbefore explained, the transmissiion of any code control, different from the last one, automatically cancels the condition established by the previous code and sets up in its place a new condition corresponding to the new code. This economizes in apparatus and in time, since it is not necessary to send a code to cancel the existing condition before sending the new code, as in the case in some forms of a selecting system of the code type. Furthermore, rather than control the switches and signals by individual codes, the code controls transmitted correspond to different routes for toL Cal

different train movements, which likewise is a desired'. economy in apparatus andtime.

The particular embodiment of the invention shown is susceptible to considerable modication or adaptationV to rit the varying conditions encountered in practice; and it should be understood that the particular organization and structure'of devices and circuits specically shown and described may be modified in many respects,

or-additional features incorporated, without de-V parting from the invention. Y

WhatI-claim isz- 1; In a dispatching system, the combination with a dispatchers oice and a'station, a stepping line and a signal line extending from the dispatchers oflice tothe station, selecting means in the dispatchers ofce and at the'station synchronously operated by impulses on the stepping line and establishing sequentially a plurality of channel circuits including said signal line, and code responsive means at the station governed by the selecting means at said station in accord'- ance with the duration of the respective impulses applied to the stepping line.

2. In a dispatching system, a switch and a plurality of signals at a station, and relays individually controlling both the-operation oi the switch and the indications of said signals, the energization of any one of said relays automatically de-energizing any of the other relays which may be energized.

3. In a dispatching system of the character described, station equipment comprising, a line relay included in a stepping line circuit and responding to impulses applied thereto, a bank of relays energized sequentially one at a time by the operationof said line relay, a slow acting relay energized when any one of said impulses are maintainedY longer than a predetermined time interval, and a plurality of relays selectively controlled by the contacts ofv said bank of relays and said slow acting relay.

4. In a dispatching system, the combination with a dispatchers oiicel and a way station, a stepping line circuit between the dispatchers office and said station, a line relay at the station, a bank of relays at the station energized sequentially one at a time by the operation of said line relay, a slow acting relay energized when the stepping line circuit is maintained energized longer than a predetermined interval, a plurality of relays eachY having an energizing circuit including a front contact of one relay of said bank of relays and a front contact of said slow acting relay, and means in the dispatchers ofce for energizing said stepping line circuit with different groups of impulses each having a diierent one of the impulses in the group of sufficient duration to cause energization of said slow acting relay.

5. Inv a dispatching system, a dispatchers oiiice, a plurality of stations, a line circuit, a plu-Y rality of impulse counting relays at each station operated over said line circuit sequentially, there being one more counting relay at each station than at the next preceding station, and a slow acting relay controlled over said line circuit for maintaining energized the last Vcounting relay at that station. K

6. In a dispatching system, a dispatchers oiiice, a plurality of stations, a stepping line circuit, a bank of neutral relays at each station energized sequentially one at a time in response to impulses applied to said line circuit, the relays `in said banks at the different stations varying in number, each relay of said bank whenA energized' prevents energization'of all preceding relays in that bank, and means for maintaining the last relay of each bank energized while the complete cycle of impulses is being applied to said line circuit.

7. In a dispatching system, the combination with channel circuit selecting devices in a dispatchers oice, and at a plurality of way stations, of means for operating said devices by code impulses of different patterns, whereby indications may be transmitted by code synchronously with indications communicated over channel circuits.

8. In a dispatching system, the combination with a dispatchers office, a plurality of Way stations, traiic controlling devices at each of said stations, a stepping circuit and a message circuit connecting said dispatchers oiiceV and the sev-V eral way stations, indicating means in the dispatchers office, and means for transmitting over said stepping circuit code combinations of current impulses for governing the traiiic controlling devices at said stations one station at a time, and means at said stations for governing the energization of said message circuit for each current impulse applied to said stepping circuit and thereby controlling said indicating means in the dispatchers office simultaneously with the transmission of controls for governing said tralc controlling devices.

9. In a dispatching system, a dispatchers oi'- ce, a way station, a bank of stepping relays in the dispatchers oice and at said station, a stepping circuit operating the relays in the said banks sequentially and simultaneously, a` message circuit, indication means in the dispatchers oce responsive to the energization of said message circuit upon each operationof a stepping relay, means at the station for governing the energization of said message circuit upon each operation of a stepping relay, traiiic controlling devices at said station, and control means for saidtraiiic controlling devices at the station selectively responsive to the different combinations of current impulses applied to said stepping circuit for the actuation of .said stepping relays, whereby controls may be transmitted from the dispatchers oflice to the way station over said stepping circuit simultaneously with the transmission of indications from the way station to the'dispatchers oice over said message circuit.

10. In a dispatching system, a dispatchers ofce, a plurality of stations, a bank of stepping relays at each station, a stepping circuit connectingthe dispatchers office and the several stations, a line relay in said stepping circuit at each station and responding to current impulses applied to said circuit, and means for rendering said banks of ,stepping relays at the several stations responsive to the corresponding line relay only one station at a time, and means at each station responding to the diierent code combinations of said impulses applied to said stepping circuit.

l1. In a dispatching system, a dispatchers of- Y lce, a plurality of stations, trafc controlling de'- vices at each station, a stepping circuit and a message circuit connecting the dispatchers oiice with the several stations, code responsive means at each station controlled entirely over said stepping circuit for governing the trahie controlling devices at that station, and means for transmitting indications from a station to the dispatchersoce over said message circuit simultaneously with the transmission of said controls to that station over the stepping circuit.

12. In a dispatching system, a dispatchers ofce, a plurality of stations, traic controlling devices at each station, a stepping circuit and a .message circuit connecting the dispatchers oice With the several stations, means for transmitting controls from the dispatchers oice to any selected station over said stepping circuit and for simultaneously transmitting indications from the same station to the dispatchers orlice over said message circuit.

13. In a dispatching system, a dispatchers oiice, a plurality of stations, traino controlling devices at each station, a stepping circuit and a message circuit connecting the dispatchers oice With the several stations, manually controllable meansin the dispatchers oiice for impressing on said stepping circiut any one of a series of current impulses of the same number but having different code characteristics, stepping relays in the dispatchers ofce and at each station operated sequentially and simultaneously by any one of said series of impulses, control means at each station Vresponsive to the code characteristics of the impulses of the series then being applied to thel stepping circuit, indication relays in the dispatohers oiiice operatively connected one at a time to said message circuit by said stepping relays, and indication control means at each station for governing the energizlation of said message circuit for each operation of the stepping relays at that station, whereby controls may be transmittedrirom the dispatchers office to a way station simultaneously with the transmission of indications over said message circuit.

14. In a dispatching system for railroads, a dispatchers oflice, a station, a stepping circuit connecting the dispatchers office and said station and including a line wire having a line relay at said oice and a line relay at said station in series therein, control levers in the dispatchers oice,

ingdiiierent operated conditions governed by said different code combinations of impulses, indication relays in the dispatchers office, indication control means at the station, a message circuit separate from said line wire and line relays extending from the dispatchers oice to the station, and means including said message circuit and governed by said step-by-step means for actuating said indication relays in accordance with the conditions of the corresponding indication control devices.

15. In a dispatching system for railroads a dispatchers oice, a plurality of stations, a stepping circuit and a message circuit connecting said dispatchers oice and the several stations, a bank of stepping relays in the dispatchers o'ice and at -each station operated synchronously by impulses on said stepping circuit, a plurality of control relays at each station rendered responsive one at a time to the energization of said stepping circuit by the operation of the corresponding bank of stepping relays, indicating means in the dispatchers office responsive to the energization` of said message circuit upon each operation of a stepping relay, and means at said stations for controlling the energization of said message circuit for each operation of the stepping relays at that station.

16. In a system for governing switches and signals on railroads, a dispatchers oiiice, a distant way station, step-by-step means in the dispatchers ofce and at said station operated synchronously to dene a plurality of time-spaced steps, a control line circuit and an indication line circuit connecting the dispatchers oiiice and said station, means in the dispatchers oice for governing the electrical condition of said control line circuit on the successive steps, and means at the station for simultaneously governing the electrical condition of said indication line circuit on the same successive steps.

17. In a system for governing switches and signais on railroads, a dispatchers oice, a distant Way station, a bank of stepping relays in the dispatchers oice and at said station operated synchronously to dene a series of steps at predetermined time intervals, a control line circuit and an indication line circuit connecting the dispatchers oce and said station, means at that station responsive tothe electrical condition of said control line circuit on successive steps, and means in the dispatchers office responsive to the electrical condition of said indication line circuit on the same successive steps.

18. In a train dispatching system of the synchronous selector type, a message circuit oompleted momentarily; a polar indicating relay of the permanent magnet stick type located at the dispatchers oflice and included in said circuit; and means at a distant Way station for applying potential of one polarity to said circuit when an east bound signal is at proceed, and applying potential of another polarity to said circuit when a west bound signal is at proceed.

19. In a train dispatching system of the synchronous selector type, two message circuits each completed momentarily; two polar indicating relays of the permanent magnet stick type located at the dispatchers oiice and each included in one of said circuits; and means at a distant way station for applying potential of one polarity to one of said circuits When an east bound signal is at proceed, applying potential of another polarity to said one circuit when a West bound signal is at proceed, applying current of one polarity to the other of said circuits when either a West bound or an east bound signal is at proceed, and applying current of the reverse polarity to said other circuit when all of said signals are at stop.

20. In a system for governing the positions of track switches and the indications of associated wayside signals located at intervals in an extended territory from a'central dispatchers oce, a plurality of station equipments located at intervals in said territory and each including code responsive means for governing the switch and signals adjacent thereto, said station equipments also including indication control devices conditioned in accordance with the position of the corresponding track switch and the indications of the associated signals, control levers and indicating means in the dispatchers ofce, and a communication system for establishing communication between the code responsive means of said stations one at a time and the corresponding control levers, said communication system also simultaneously establishing communication between the indication control devices at a station and the corresponding indicating means in the dispatchers office.

21. In a dispatching system, a dispatchers oiiice, a track switch and signals at a distant point, control levers in the dispatchers o'ce havin'g different positions for the different positions of said switch and the indications of said signals, a stepping circuit extending from the dispatchers oiceto said distant point', code creating circuit portions in the dispatchers oiice each including in series contacts oi said levers and connected to said stepping circuit to conduct to said stepping circuit any one of a plurality of different series of current impulses of the same number but having at least one impulse in each series distinctively diierent from the corresponding impulse of any other series dependent upon the relative positions of said control levers, and code responsive means at said distant point governed by said series of impulses for controlling said switch and signals. Y

22. In a centralized trafc control system for railroads, a dispatchers oiiice, a way station, a track switch and signals at said station controllable to set up different routes for train movements, a stepping circuit, manually controllable means in the dispatchers oidce for applying to said stepping circuit different code combinations oi impulses one for each route, a plurality of control relays at the way station each being operable to govern both the position of said switch and the indication of said signals to set up a particular one of said routes, and means at the way station for decoding the different code combinations of impulses placed on said stepping circuit, said means energizing one particular control relay only when the corresponding route code combination is decoded.

23. In a dispatching system, a dispatchers office, a way station, a track switch and signals at said station controllable to set up different routes for train movements, a stepping circuit, manually controllable means in the dispatchers ofce for applying to said stepping circuit different code combinations of impulses one for Veach route and one for all routes at stop, and a plurality of control relays a't the station, each being'selectively responsive only to a particular one of said code combinations of impulses for governing both the position of said switch and the indications of said signals, whereby any particular route Ymay be set up and whereby 'all routes may beput to stop.

24. In a dispatching system for railroads, a relay having a control Contact operable to at least two positions, a slow acting relay having neutral contacts, a source of energy having positive and negative terminals together with a mid tap, means for connecting one terminal of said slow acting relay to said mid tap of 'said source, and means including said control contact for connecting the other terminal of said slow acting relay to said positive or negative terminals of said source, whereby the neutral contacts of said slow acting relay remain in retracted positions when said control contact is operated to alternate Vpositions above a predetermined rate, and whereby Vthe neutral contacts of said slow acting relay are actuated to attracted positions when said control contact remains in one of its positions for more than a predetermined time. Y

25. In a dispatching system for railroads, a dispatchers oiiice; a plurality of way stations; a line circuit connecting the dispatchers oiiice with the way stations; means in the dispatchers office for energizing said line circuit with impulses above a predetermined rate and for prolonging selected impulses; a line relay at each way station included in said line circuit and having a control contact operable to at least two positions; a slow acting relay at each way station, said slow acting relays having neutral contacts; a source of energy at each way station having positive and negative terminals together with a mid tap; means at each way station selectively connecting one terminal of its respective slow acting relay to the mid tap of its respective source; and means including said control contact at each station for connecting the other terminal of said slow acting relay at that station to said positive or negative terminals of its respective source; whereby the neutral contacts of said slow acting relays remain in retracted positions when said control contacts are operated to alternate positions above a predetermined rate; and whereby the neutral contacts of said slow acting relays are actuated to attracted positions when said control contacts remain in one or the other of their positions for more than a predetermined time.

26. In a dispatching system for railroads, a dispatchers ofce; a plurality of way stations; a line circuit connecting the dispatchers oihce with the way stations; means in the'dispatchers olce for energizing said line circuit with impulses above a. predetermined rate and for prolonging selected impulses; a line relay at each way station included in said line circuit and having control contacts operable to at least two positions; va slow acting relay at each way station, said slow acting relays having neutral contacts; a source of energy at each way station having positive and negative terminals together with a mid tap; station selecting means at each station for rendering said slow acting relays at the several stations responsive to their respective control contacts at only one station at a time; and means including said control contact at each station for connecting the other terminal of said slow acting relay at that station to said positive or negative terminals of its respectivesource; whereby the neutral contacts of said slow acting relays remain in retracted positions when said control contacts are operated to alternate positions above a predetermined rate; and whereby the neutral contacts of said slow acting vrelays are actuated to attracted positions when said control contacts remain in one or the other of their positions for more than a predetermined time. i

27. In a dispatching system, a dispatchers office, a track switch and signals at a distant point, control levers in the dispatchers oilice having different positions for the diierent positions of said switch and the indications of said signals, a stepping circuit extending from the dispatchers office to said distant point, code creating circuit 4branches in the dispatchers oilice including in series contacts of said control levers for impressing on said stepping circuit any one of a plurality of different series of current impulses each of said series being determined in accordance with 'the relative positions of saidcontrol levers, a control relay at said distant point for each different series, each control relay corresponding to a route over said track switch, and means governed by `each control relay for clearing the one of said signals corresponding to the route to which that control relay is assigned, only when said track switch is aligned for the corresponding route.

28. In a dispatching system, a dispatchers cnice; vka track switch and signals at a distant point; control levers in the dispatchers office having different positions for the different positions of said switch and the indications of said signals; a stepping circuit extending from the dispatchers oilice tc said distant point; code creating branches in the dispatchers office each including in series contacts of said control levers for impressing on said stepping circuit any one of a plurality of different series of current impulses, each of said series being determined in accordance with the relative positions of said control levers; a control relay at said-distant point for each different series of currentimpulses,Vr each control relay corresponding to a route over said track switch; and means governed by each ccntrol relay for aligning said track switch for the corresponding route and for clearing the corresponding signal governing traffic therecver, whereby a route can not be cleared until said track switch has been governed.

29. In a centralized traic control system for railroads, a control oice, a eld station, trailc controlling devices at said field station, a stepping circuit connecting the control office and said field station, a plurality of manually operable control levers in said control ofce each of said levers being capable of assuming a plurality of positions, code transmitting circuit branches in the control office each including contacts of saidY control levers in series and capable of integrating the positions of said plurality of control 1evers for impressing on said stepping circuit composite codes characterizing such integrated lever positions, and code receiving means at the eld station capable cf differentiating said composite codes for controlling the plurality of traiic controlling devices tc positions corresponding to their respective levers.

30. In a centralized traffic control system for railroads, a control orlice, a field station, a railroad track switch at said iield station, a switch machine for operating said track switch, signals for governing trafc over said track switch, a stepping circuit connecting the control oilice and the field station, a switch machine control lever in the control ofce capable of assuming either of two positions, a signal control lever in the control oice capable of assuming either of three positions, code transmitting circuit branches in the control cflice each including contacts of said control levers in series and capable of integrating the positions of said switch machine ccntrol lever and said signal control lever for impressing on said stepping circuit composite codes representative of particular routes over said track switch said codes comprising a predetermined number or impulses, and code receiving means at the field station capable of differentiating said composite codes for controlling said track switch and said signals at that field station, whereby the complete establishment of the route corresponding to the composite route code is accomplished, and whereby failure of establishment of a complete route holds all routes at stop.

3l. In a centralized traffic control system for railroads, a control cice, a eld station, a railroad track switch at said eld station, a switch machine for operating said track switch, signals for governing trafc over said track switch, a stepping circuit connecting the control ciice and the field station, a switch machine control lever in the control oflice capable of assuming either of two positions, a signal control lever in the control cfce capable of assuming either of three positions, code transmitting circuit branches in the control cice including contacts of said control levers in series and capable of integrating the positions of said switch machine control lever and said signal control lever for impressing on said stepping circuit composite codes representative of particular routes over said track switch said codes comprising a predetermined number of impulses, and code receiving means at the field station including a route code relay for each of said composite codes, a particular route code relay being picked up only when its corresponding composite code is received, and means controlled by each cf said route code relays for operating saidl track switch and for clearing the particular signal governing traic over the corre,- sponding route only when said track switch has assumed a proper pcsitionor that route.

32. In a dispatching system for railroads, a dispatchers cnice, a plurality of stations, a stepping circuit and a message circuit connecting said dispatchers oilice and the several stations, a bank of stepping relays at each station operated synchronously by impulses on said stepping circuit, a bank of stepping relays at the office cperated synchronously with station banks, a plurality of control relays at each station rendered responsive one at a time to the energization of said stepping circuit by the operation of the corresponding bank of stepping relays, indicating means in the dispatchers office responsive tc the energizaticn of said message circuit upon each operation of a stepping relay, and means at said stations for controlling the energization of said message circuit for each operation of the stepping relays at that station.

33. In a system for governing railway signal apparatus, a central station, a distant field station, a bank of stepping relays in said central station, a bank of stepping relays at said eld station, a circuit connecting said stations, means for applying at one station a series of impulses to said circuit to characterize a code, means for causing synchronous step-by-step operation of said banks of stepping relays one step for each impulse of said series impressed on said circuit, code responsive means at the other station distinctively responsive to the code character of said series of impulses, and means including said stepping relay banks and functioning during the transmission of said series of impulses for transmitting an indication from said other tc said one station.

34. In a system for governing railway signal apparatus, a central station, a distant iield station, a bank of stepping relays in said central station, a bank of stepping relays at said field station, a circuit connecting said static-ns, means for applying at one station a series of impulses of positive and negative polarity to said circuit said impulses being of long and short duration to characterize a code, means for causing synchroncus step-by-step operation of said banks of stepping relays one step for each impulse of sai-d series impressed on said circuit, code responsive means at the other station distintively responsive to the code character of said series cf impulses, and means including said stepping relay banks and functioning during the transmission of said series of impulses for transmitting an indication from said other to said one station.

35. In a system for governing railway signal apparatus and transmitting a return indication, .a central station, a distant field station, a bank of stepping relays in said central station, a bank and means including said stepping relay banks and functioning during the transmission of said series of impulses for transmitting an indicatlon from said other 'to said one station in accordance with the polarityY of current transmitted during each operation of a stepping relay.`

36.111 combination, an oiice and a. distant field station, a multiple impulse selector type system for transmitting conditions of tra'fc from said eld station to saidoiiice .and which is normally at rest, two stick relays for initiating said system the first of which includes a. pick-up circuit closed upon a change in traffic conditions and a stick circuit including a contact closed during operation of said system and the second stick relay of which includes a pick-up circuit including a front contact of the first stick relay and a stick circuit including a contact opened when said system has completed its operation,

and a contact on said second stick relay for initiating said system.

. NEIL D. PRESTON.

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