US2136829A

US2136829A - Railway traffic controlling apparatus

Info

Publication number: US2136829A
Application number: US165458A
Authority: US
Inventors: Howard A Thompson
Original assignee: Union Switch and Signal Inc
Current assignee: Hitachi Rail STS USA Inc
Priority date: 1937-09-24
Filing date: 1937-09-24
Publication date: 1938-11-15
Anticipated expiration: 1955-11-15

Description

Nov. 15, 1938. I

H. A. THOMPSON RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept; 24, 1957 5 Sheets-Sheet 1 INVENTOR H15 ATTORNEY RAILWAY TRAFFIC CCNTROLLIIIG APPARATUS Filed Sept. 24, 1937 5 Sheds-Sheet 2 INVENTOR How and A. 0129115012.

HIS, ATTORNEY Nov. 15,1938. H. A. THOMPSON 2,136,829

RAILWAY TRAFFIC CONTROLLING APPARATUS bwwwookmw s US AN $61 INVENTOR fiowa dA.

HIS ATTORNEY NOV. 15, 1938.

Filed Spt. 24 1957 5 sneaks-she 4 m R Y m m M m A Mm w w H \HQWWFM h, m l. mm MQMW U w m n w mm 5 m k WW L ANN v m E E F .RN mww R1 N 5 w R Q mH 5% w u. Q Q 3 NR 5 MA w w \QNSQ KQWUE \QK H. A. THOMPSON RAILWAY TRAFFIC GCNTROLLING APPARATUS Nov. 15, 1938.

Filedsept. 24, 1937 5 Sheets-Sheet 5 m mm NO E V RNN HIS ATTORNEY Patented Nov. 15, 1938 UNITED STATES PATENT. omcs RAILWAY TRAFFIC ooN'rRo LiNG APPARATUS fibward A. Thompson, Edgewoodg -Pa, assignmto The Union Switch & Signal Company; Swissvale, Pa, a corporation of Pennsylvania Application September 24, 1937, Serial No. 165,458

21 Claims.

My invention relatesto railway traffic controlling apparatus andit has special reference to the organization of suchapparatus into systems of the class in whichwayside signals positioned along the trackwayior governing the passage of trains are controlled by energy transmitted through the track railsr 7 One object of my invention-is to provide a novel and improveduformof such organization.

Another object is to improve the facilities ,used in systems of the) class named to code and decode the trackvvayenergy; t H

rAn additional object is to make provision whereby accidental failure of the signaling appa- 15L ratus vwill be on-the safe side.

A furtherflobiectxisto organize the trafliccontrolling apparatus into a signaling system which, a is self -protecting against L broken-down rail joints.

9 a In practicing my invention; I attain the above and other objects and advantages by providing a con'imonreference-control: circuit through which pulses of energy spaced in accordancewith a-master code are supplied to the locations of allvof the wayside signals. A relay operated at eachlocation by these pulses codes the energy supplied to the rear; track section and other apparatus associated with each coding relay compares theenergy receivedvfrom the forward track section withvthe master-code pulses. In accordance with this comparison, the referredto apparatus controls the associated signal and-determines the? form of trackway energy which is supplied-to the rear? Q A a I shall describe three forms of railway trailic controlling apparatusembodyin-g my invention, and shall then point out the novel features thereofwin claims. L In the accompanying drawings, Figs, 1a, 1b and lc are diagrammatic views-which, when placed end to'end in theorder named, represent a stretch of railway track equipped-with trafiiccontrolling apparatus embodying my-invention and organizedrinto a signaling system inwhich the track circuits are operated by direct-current obtainedfrom an alternating-current source;

Fig: 2 is a representation of the manner, in which the different forms of trackway energy used in the-system of Figs. 1co--Z7 --'c compare with the pulsations which constitute the master code therefor; l

Fig. 3 is a diagrammatic View of apparatus at one signal location only showing the improvements of my invention incorporated in a signailing systemwherein the track circuits and signals are operated by direct-current energy obtained fro m batteries; V C

Fig. 4 is a similar viewlshowing the improvements of, my invention incorporated in a signaling system which uses alternating current in the track circuits; 1

Fig; 5 is a representation of a portion of one of the vsignal-locationequipments of Figs. 1a- E o-showing code checking equipment combined therewith; and i Fig. 6 is a View, showing a single referencecontrolcircuit connected to supply pulses of master codel energy to signaling apparatus associated with a plurality of different tracks.

Referring to the-drawings, in the several views of which sirnilar refererice characters refer to similar parts, the 'traflic controlling apparatus comprised by the systems of Figs. la-b-e, is organized to insurethat a safe spacing will be maintained between trains which move one after another along the track rails I and 2 in the direction of the arrows, or from left to right in the diagrams. The protected stretch of this track is divided, by insulated rail joints 3, into a number of blcks A-B, B--C,\ C D, etc; and at the entrance of each block there is positioned a signaling device S which is adapted to indicate to an approaching train the nature of the trailic conditions in the blocks immediately ahead.

The particular signaling devices shown by way of illustration atthe locations A, B, C, D and E are wayside signals of a well-known color-light type; Each comprises a standard supporting, one above. the, otlfier, two units or asemblages of three lamps G, Y, and R which when lighted respectively display the colors of green, yellow and red. These signals are arranged to show any one of the five different aspects which are respectively displayed by the devices represented at Sa, Sb, scgsd and Se. It will be assumed, for purposes'ofiiplanatiohthat these particular aspects of green over-green, green-over-yel- 1bw,- yellowover'-yellow; yellow-over-red, and red-over-red respectively signify indications of proceed, caution; approach, slow, and t p 1 The equipment illustratively represented in the diagram of each of the Figures 1a -b--c, 3 and 4 so controls the signals S that Whenever a train occupies or advances along the track |--2, the signal immediatelybehind the train gives a stop indication, the next signal to the rear a slow indication, the next one back an approach indication, the next signal to the rear a caution indication, and the fifth signal behind the train lays.

a clear or proceed indication. In eifecting this control the apparatus shown utilizes energy transmitted through the usual track circuits controlled by the trains themselves.

At each of the signal locations A, B, C, etc., in all three of the systems herein disclosed, there is provided a track relay TR connected in the usual manner with the traffic-entering ends of the rail sections of the forward track circuit to receive energizing current therefrom, a pair of auxiliary relays XI and XD arranged for selective parallel connectionwith the track relay, and a code-following relay CR which codes the energy supplied to the rear track circuit and sets up energizing circuits for the auxiliary re- The four relays just named cooperate to control the associated signal S and to determine the form of the energy supplied to the track rails in the immediate rear thereof.

The signal-control and the trackway-energy selections above referred to are made in accordance with the manner in which the energy received by the relay apparatus from the forward or associated track circuit compares with the pulsations of a master code transmitted to the code-following relay CR through a referencecontrol or master circuit 6. This circuit extends along the right of way in the manner indicated and through a master coder MC it is continuously supplied with spaced pulses of energization of the. general character indicated at H) in Fig. 2.

The particular coder shown at MC includes a circuit making and breaking device 1 which is interposed between the circuit} and a suitable source of control energy. Ordinarily this source will be of the direct-current type, such as the battery represented at 8. If desired, however, alternating current, derived, for example, from the transformer shown at IS in Fig. 4, may instead be utilized. 7

7 Operation of themaster coder is effected by a motor or other mechanism (not shown in detail) which continuously actuates the device I at a constant speed. For purposes of illustration it will be assumed that this speed is suchas to provide a master code of the1ge'neral order of 100 energy pulses per minute. In the resulting cycles of a preferred form of this code which are shownin Fig; 2, the onf and off" periods are of substantially equal lengths.

The code-following relay CR at each of the signal locations is directly connected with the master circuit 6 to receive the spaced energy pulses l acting therein. This relay is provided with contacts (represented therebeneath) which are quick acting in both the pick-up and dropout directions in order that they may change their position in accurate synchronism with the master code pulses. During the on periods of the code when the relay is energized these con: tacts are held in their uppermost or front position (shown heavy) while during the off periods, when the relay is deenergized, they occupy their lowermost or back positions (shown dotted).

The track relay TR at each location is adapted to respond to energy 'received'from the track rails through the conductors II and I2 and also to distinguish the polarity of this energy. It may be of any conventional polarized design provided with polar contacts (shown vertical therebeneath) which shift from one position to the other when the polarity of the relay energization changes and which, when the relay is deenergized,

stay in the position to which they were biased by the last energization of the relay.

In the modification of Figs. lab-c and 3 each of the track relays TR also has neutral contacts (shown horizontal) which occupy their lowermost or back positions when the relay is deenergized and which are moved to their uppermost or front positions when the relay is energized. These neutral contacts are slow releasing in order that they may remain continuously actuated when the relay is intermittently energized at closely spaced intervals of the order represented in Fig. 2.

The two auxiliary relays XD and XI also are provided with contacts which are slow releasing in the drop-out direction and quick acting in the pick-up direction. Each of these relays is arranged to receive energy from the trackway through a circuit including, in the particular arrangement shown, the conductors II and I2 which supply the track relay TR, conductors I3 and I4 conected therewith, and a selector contact 9 of the code-following relay CR.

The circuit for relay XI further includes a conductor I6 through which the code-following contact 9 connects the winding of relay XI in parallel with the track relay TR during each of the on periods of the master code cycles. Similarly, the energizing circuit for relay XD includes a conductor I! through which the contact 9 completes a connection of the winding of that relay with the track rails during the off periods of the master code. Optionally, a neutral contact l8 of the track relay TR may also form a part of both the circuits named to permit completion thereof only when the neutral contacts of the track relay are picked up.

When arranged as above described, it will be seen that the track relay TR is capable of responding to coded energy of any one of a number of different characters which may be received from the track rails and also is adapted to distinguish the polarity of that energy. The auxiliary relays XI and XD, on the other hand, are adapted selectively to respond only to energy which may be present in the associated track circuit during the on and the off periods respectively of the master code impulses which act in the circuit 6. These auxiliary relays are unaffected by changes in trackway energy polarity.

The mentioned selective response by the auxiliary relays XI and XD results from the action of contact 9 of the code-folowing relay CR. During each on period of the master code, this contact connects the winding of relay XE in energy-receiving relation with the track rails and during each off period of the master code it similarly connects the winding of the companion relay XD with the associated track circuit. The supply circuit thus periodically completed for relay'XI extends from track rail I through conductors H and I3, the winding of relay XI, conductor l6, front contact 9 of relay CR, conductor I4, front contact 3 of relay TR (not used in Fig. 4) and conductors 81 and I2 back to track rail 2. The corresponding circuit for relay in) similarly extends from rail I through conductors II and I3, the winding of relay XD, conductor I1, back contact 9 of relay CR, conductor I4, front contact l8 of relay TR (again not used in Fig. 4) and conductors 81 and I2 back to rail 2.

Being insensitive to polarity change, relay XI thus responds to the in-phase normal and to the in-phase reversed codes shown in Fig. 2 and described below and relayl fl) similarly responds to the displaced normal and to the displaced reversed codes of that f gure. The

periodof contact release delay for each of these relays is long enough to bridge the intervals between successive pulsesof the recurring energy which the winding of the relay at times receives from the track circuit and hence the relay contacts remain continuouslypicked up for the full duration of each of the referred to responses.

As already pointed out in an earlierportion of the specification, the, neutral contacts of the trackrelay TR areinsens'itive to polarity change and hence it will be seen that they remain continuously picked up when the relay receives energy of any one of the four trackway codes of Fig. 2. The polar contacts, however, will be seen to shift to the left in response to the first two or normal-polarity trackway codes of Fig. 2 and to the right in response to the lasttwo or reversed-polarity'codes of that figure. Noneof these polar contacts is included in the energizing circuits of the auxiliary relays XI and KB.

, In each ofthe three-railway signaling systems hereindisclosed, the fcurdiiferentforms of trackway code shown in Fig. 2 and already mentioned above are utilized, in connection with the relay apparatus just described, to provide the several distinctive" characters of control for governing the multi-aspect signals S which giiard the blocks of the protected stretch of track I 2. The in-phase normal variety of trackway code represented in Fig. 2 is made up of spaced energy tacts to the 1ert.

- pulses ill.

pulses 2B which are supplied to the track rails (through front contacts of the relay GR) in time coincidencecr in phase with the master code pulses iii. The polarity of these' pulses', moreover, is such as to make the track relay conductor Ii energized thereby positivewith respect to the conductor 12. Such pulses energize the supplied track relayTR. in what will be termed the norrrial direction and cause it to bias its pmarm The displaced normal code consists ofspaced energy pulses 2 lyIhich have. the same polarity as do the pulses 2e above considered but which are supplied (through back contacts of the relay CR.) to the track rails during the off" periods of the master code cycles. They are, therefore, displaced from the master code pulses Iii.

In the caseof the in phase reversed code, the pulses 22 thereof againare supplied to the trackway in. time coincidencewith the master code Their polarity, however, is such as to make the track relay conductor ll energized thereby negativewith respect to the conductor l2. Such pulsesenergize the supplied track relay TR in what will be "termed the reversed direction and cause its polar contacts to be biased to the right. V

The fourth or displaced reversed variety of trackwaycode shown in Fig. Zis made up of energy pulses 23 having the same polarity as do the pulses 22 above discussed but whichare supplied to the track rails during the off periods of the master code cycles.

In each of .the three signaling systems now about to be described in greater detail, the relay apparatus is arranged to respondin a distinctive that the in-phase normal code causes the con.- trolled signal S to give a proceed indication, the displaced norma'l code produces a caution indication, the in-phase reversed code results in an approach indication, the displaced-reversed code produces a slow indication; and no energy at all received from the trackwa'y causes the signal to give a stop indication. As the description proceeds, however, it will become ap-' parent that relations between trackway codes and signal aspects other than the above illustrative set are readily possible in signaling systems emb o-dying the improvements of my invention.

Considering first the further details of the embodiment of my invention shown in Figs. ldb-c, all of the equipments there represented at the signal locations A, B, C, D, etc. are energized from a common alternating current supply circuit 24. This circuit may be of commercial voltage and frequency and extends along the right of way in the manner indicated. Interposed be tween it and the named equipments are step-down transformers 26 which reduce to an intermediate value the voltage supplied to the various equipment circuits. l

In the particular arrangement shown, energizing current for the lamps of each of the signals S is supplied through a second transformer 28 which is constantly excited by the intermediate voltage named above and which is selectively connected with the signal lamps through circuits which include common conductors 3B and 37 and contacts carriedby the track and auxiliary relays TR, XI and XD. Through the contacts above referred to, the named relays control the signals in a manner best explained by tracing the energizing circuits for the signal lamps under the various different conditions of system operation. P

When the relay contacts occupy the positions shown for the equipment at location A, the con trolledsignal shows the proceed'o'r green-oven green indication displayed by deviceSa oi the diagram. The energizing circuit for the upper l'amp .G then includes conductor 3t joined with one side of the transformer 28, the lamp itself, conductor 3 I, a polar contact 32 of the track relay TRQcQnductOr 33, a front contact-34 of the auxiliary relay XI, conductor 35, a back contact 36 of the auxiliary relay XD, and conductor 3'! joined with the other side of the transformer. The lower lamp G at the same time receives current through a circuit wlnch extends from conductor 30 through the lamp, conductor 39, a second polar contact 40 of relay TR, conductor 4!, a second contact 42 of relay XI, conductor 43, and a second contact 44 of relay XD back to conductor 31.

When the relay contacts occupy the positions shown for the equipment at location B, the controlled signal shows the caution or green-overyellow indication displayed by device SD of the diagram. The energizing circuit for the lamp G of the upper unit then may be traced from conductor 39 through the lamp itself, con-ductpr 3|, polar contact 32 of the track relay, conductor 33, and contact 36 of relay XD, back to conductor 37. The lamp Y of the lower unit at the same time receives current through a circuit which extends from conductor 30, through the lamp itself, conductor 45, a third polar contact it of the track. relay TR, conductor 47, and the contact 44 of relay XD back to conductor 37.

When the contacts of the relays TR, XD and XI occupy the positions shown at location C, the controlled signal shows the approach or yellowover-yellow indication displayed by device so of the diagram. The energizing circuit for the upper lamp Y now extends from conductor 30 through the lamp itself, conductor 49,, contact 32 of relay TR, conductor 33, contact 34 of relay XI, conductor 35, and contact 36 of relay XD back to conductor 31. At the same time the lower lamp Y receives current through a circuit which may be traced from conductor 36 through the lamp, conductors 45 and contact 40 of relay TR, conductor 52, contact 42 of relay XI, conductor 43, and contact 44 of relay XD back to conductor 31.

When the relay contacts have the positions shown at location D, the controlled signal shows the slow? or yellow-over-red indication displayed by device Sd. The energizing circuit for the yellow lamp of the upper unit now extends from conductor 30 through the lamp, conductor 43, contact 32 of relay TR, conductor 33, and contact 36 of relay XD back to conductor 31. The circuit through which the lower lamp R receives current may be traced from conductor 30 through the lamp, conductor 53, contact 46 of relay TR, conductor 41, and contact 44 of relay XD back to conductor 31.

.Finally, when the contacts of the relays TR, XI and XI) have the positions represented at location E, the controlled signal shows the stop or red-over-red indication displayed by device Se of the diagram. The circuit through which the upper lamp R receives current then extends from conductor 30 through the lamp, conductor 55, contact 34 of relay XI, conductor 35, and contact'36 of relay XD back to conductor 31. The energizing circuit for the lower lamp R may be traced from conductor 30 through thelamp,

conductors

53 and 56, contact 42 of relay XI, conductor 43 and contact 44 of relay XD back to conductor 31.

The character of the signal-control energy which is received at each signal location from the associated track circuit determines which one of the several just-described positional combinations will be assumed by the contacts of the track and auxiliary relays TR, XI and XD. As has been pointed out, this energy is one or another of the four trackway codes respectively represented at 26, 2|, 22 and 23 in Fig. 2.

In the system of Figs. 1a b-c, the signal-control energy just referred to is supplied at each signal location to the trafiic-leaving end of the rear track circuit through one or the other of two rectifiers RP and NP connected, through

conductors

48 and 50 and the usual current-limiting impeder 58, with the rails l and 2 in normal and reversed polarity relation respectively. Included in the connections is a selector relay 6!] provided with a contact 6| which is biased to the right, as

. shown at locations A, B and C, when the normalpolarity rectifier NP is energized and biased to the left, as shown at locations D and E, when the reversed-polarity rectifier RP is energized.

When in the position first named, this contact 6| completes the connection of rectifier NP with the rails and disconnects rectifier RP therefrom. When in the position second named, this contact 6| disconnects rectifier NP and connects rectifier RP to the rails. In this manner, each of the rectifiers is prevented from being short circuited by the other. The two rectifiers NP and RP are respectively energized through a pair of transformers 62 and 64 which step down to the comparatively low value best suited for track-circuit operation the potential which is impressed between the track rails through the rectifiers NP and RP. These transformers, in turn, derive energization from the supply transformer 26 through circuits which include

common conductors

65 and 66 and contacts carried by each of the four relays TR, XI, XD and CR. Through the referred to contacts of relays TR, XI and XD an energizing circuit for one or the other of the transformers is selectively set up and through a coding contact 68 of the relayCR this circuit is periodically completed either during the on or the off periods of the master code which acts in the referencecontrol circuit 6.

As will be seen, the selection of the transformer 62 or 64 determines the polarity (normal or reversed) of the energy supplied to the trackway while the selection between the on and the off periods of the master code cycles determines the phasing (in-phase or displaced) of this energy. The manner in which these selections are made may best be explained by tracing the track energy supply circuits under differing conditions of operation of the signaling system.

When the contacts of the track and auxiliary relays TR, XI and X13 occupy the positions shown at location A, there is set up for transformer 62 an energizing circuit which is completed each time that the contact 68 of relay OR is biased to its front or uppermost position by an. energy pulse In of the master code. This circuit may be traced from conductor 65 connected to one side of transformer 26 through the primary winding of transformer 62, conductor 69, a neutral contact of track relay TR, conductor H, a polar contact 12 of relay TR, conductors l3 and 15, and contact 68 (in its front-closed position) of codefollowing relay CR back to conductor 66 connected to the other side of transformer 26.

Under these conditions, the track circuit immediately behind the location is supplied through rectifier NP with energy of the in-phase normal code represented in Fig. 2 as being made up of the spaced pulses 20. The coding of this energy, as will be seen, is effected by the master coder MC which, through the contact 68 of code-following relay CR, establishes and interrupts the trackway energizing circuit at a speed previously assumed, for purposes of explanation, to result in the general order of 100 energy pulses per minute.

When the relay contacts occupy the positions shown at location B, there is still set up for transformer 62 an energizing circuit which is exactly the same as that just traced through the relay contacts at location A. In consequence, rectifier NP continues to supply energy of the inphase normal code to the rails of the track section immediately behind the location.

When the relay contacts occupy the positions shown in location C, there is set up for transformer 62 an energizing circuit through which the rails of the track section immediately behind that location are supplied with energy of the displaced normal code. This circuit extends from conductor 65 through the transformer, conductor 69, neutral contact 10 of relay TR, conductor H, polar contact 12 of relay TR, conductor 14, contact 16 of relay 2H, conductor 11, and the contact 68 (in its back-closed position) of code following relay CR back to conductor 66. Under these conditions, the transformer energizing circuit is completed each time that the contact 68 of relay CR moves to its back or lowermost position between adjacent pulses l0 ofthe master code and the resulting pulses of trackiii my energy correspond to those shown at 2| in Fig. 2.

When the relay contacts occupy the positions shown at location D, there is'set up for trans- .former 64 an energizing circuitthrough which there is supplied to the rails of the track section.

immediately behind that location energy of the in-phase reversed code represented at 22 in Fig. 2. This circuit maybe traced from conductor 65 through the transformer, conductor 18, a neutral contact lSlofrelay conductor 80, a polar contact 8| of relay TR, conductor 82,

a contact 83 of relay XD, conductor 15, and the contact 68 (in its front-closed position) of codeductor 65, through the transformer, conductor I8, neutral contact I9 of relay TR, conductors 85 and TI, and coding contact 68 (in its back- .closed position) of relay CR back to the conductor 66.

The various component parts of the first embodiment of my improved signaling apparatus having been described, attention will now be directed to the manner of operation of the complete system shown in the diagram of Figs. 1a--bc. When all of the protected blocks are unoccupied, the control equipments at all of the signal locations assume the condition represented at location A. That is, the relay apparatus at each and every (me of the signal locations is supplied with energy of the in-phase normal code by way of the two rails of the associated track circuit.

In ,consequence,at each signal location the track relay TR holds its neutral contacts I8, 10 and 19 in the picked-up or front positions. shown and maintains its

polar contacts

10, 12, 8|, 46, 40 and 32 in the left-biased or normal positions illustrated. Likewise, the auxiliary relay XIat each location also receives trackway energy (through the circuit previously traced as extending from conductor: H, through conductor l3, the

relay winding, conductor I6, selector contact 9-in its front position-of code-following relay CR, conductor I4, contact l8 of relay TR and conductor 81 back to conductor I2) and holds its

contacts

16, 42 and 34 in their front positions.-

The auxiliary relay XD, however, is deenergized and maintains its

contacts

83, 44 and 36 in their back positions.

Under these conditions, all of the controlled signals S are caused, in the. manner previously explained, to give the. clear or proceed indication and, through circuits already traced in detail, the rails of each of the track blocks immediately behind the signals are supplied with energy of the in-phase normal or proceed code.

In the event that a train V (see Fig. 10-) oocupies one of the blocks of the protected stretch of track, the wheels and axles thereof directly interconnect or short-circuit the rails l and 2 of that block and shunt the signal control potential from between the rails. This short-circuiting diverts' the trackway energy from the associated relay apparatus and causes all three of the relays TR, XI and KB to be deenergized. In consequence, the signal-control equipment at thecentrance of the occupied. block assumes the condition represented in the diagram at location E in which the neutral contacts of the track relay TR occupy their back positions, the polar contacts thereof remain in their left-biased positions (determined by the normal energizaticn of the relay which was efiective at the time the train entered the block) and the contacts of bothauxiliary relays and XD also occupy their dropped outpositions. .As a result, the controlled signal is caused, in the manner previously described, to give the .stop. indication displayed by device'Se and, through circuits already traced in detail, the rails of the track circuit imme diately to the rear are supplied, as indicated for the block D-E, with energy of the displaced reversed or slow code.-

The relay apparatus associated with the thus energized track circuit responds to the named energy in the manner represented at location. D. There the track relay TR has picked up its neutral contacts and is holding them in their front positions and has shifted its polar contacts to 1 their right or reversed positions, the auxiliary relay XD also receives trackway energy (through the circuit previously traced as extending from conductor II through conductor IS, the relay indicated for the block C-D, with energy of the inphase reversed or approach code through circuits already traced in detail.

The relay apparatus associated with the thusenergized track circuit responds to the energy just named in the manner represented at location C. There the track relay TR is maintaining its ne'utral contacts in their front positions and .its polar contacts in their right-biased positions,

the auxiliary relay XI now also receives. trackway energy'and holds its contacts in their front positions and the relay XD is deenergized so that its contacts occupy their back positions. As a result, the controlled signal is caused to give the approach indication displayed by device so and the track circuit immediately to the rear is supplied, as indicated for the block B-C, with energy of the displaced normal or caution code.

The relay apparatus associated with the thusenergized track circuit responds to the energy named above in the maner represented at location B. There the track relay TR continues to maintain its neutral contacts in their front positions and hasshifted' its polar contacts to their leftbiased or normal positions, the auxiliary relay X0 is now also energized and holds its contacts in their front positions, and the relay XI is unactuated. In consequence, the controlled signal is caused to give the caution indication displayed by device 812- and the track circuit imme- The relay apparatus supplied with this energy responds in the manner represented at location A. There, as has already been explained in detail, relays TR, XI and XD cause the controlled signal to show the clear indication displayed by device Sc and the rails of the track circuit to the rear to be supplied with energy of the in-phase normal or clear code.

The improved system of automatic block signaling just described may be arranged to be selfprotecting against the giving of false indications due to a breaking-down of the insulating joints 3'which electrically separate the track rails of adjacent block sections. Such failure, of course, permits track circuit current from the block in the rear, for example, to flow to the track rails of the block ahead therebytending to create a potential false clear or other indication of less restrictive character.

To overcome this, both" the polarities and the phase characteristics of the coded trackway energy supplied to adjacent track circuits are alternated or staggered. One preferred form of such in-phase and displaced designations of the signal-control codes within the stretch of track represented as being under the control of a blockoccupying train V. v

7 As a result of this staggering of the polarities and of the phase characteristics of the trackway energy, it will be seen that current which may flow from a tracksection in the rear to a track section ahead through broken-down rail joints can in no instance produce an indication of the affected signal which is less restrictive than that resulting from normal operation of the system. For example, assuming that the insulating joints 3 between the adjacent sections AB and B--C break down and permit the energy of section AB to influence the relay apparatus at location B, the effect upon this apparatus will be the same as that of an in-phase reversed code. Any false indication on the part of the afi'ected signal Sb will then be of the approach character which is more restrictive than the caution indication which the named signal gives under normal operation for the particular conditions shown.

From this analysis, it will be seen that in the improved arrangement of my invention, should the coded energy of one track section pass over defective rail joints into an adjoining section, a signal indication more restrictive than normal will be displayed and the giving of potential false clear indications will thus effectively be prevented.

Considering next the further details of the embodiment of my invention shown in Fig. 3, each of the signal-location equipments comprised by the signaling system there exemplified obtains its energization from local batteries. The battery forsupplying energizing current to the lamps of the controlled signal S is shown at 90 and those for supplying to the trackway coded energy of the normal and of the reversed polarity are respectively represented at NB and RB. Comparing the apparatus of Fig. 3 with that shown in the diagram of Figs. la-b-c, it will be seen that the battery 90 is connected in the signal circuits in exactly the same manner as is transformer 28 and that the batteries NB and RB correspond to transformers 62 and 64 and their associated rectifiers NP and RP.

Except for certain difierences in the arrange: ment of the contacts which control the energize.- tion of thetrack circuits, the four relays CR, TR, XI and -XD installedat each of the signal locations in the system of Fig. 3 are identical with the four corresponding relays of the embodiment of my inventionpreviously described. They are arranged to respond in precisely the same manner when the controlling track circuit respectively transmits thereto no energy at all and energy of each of the four trackway codes represented in Fig. 2.

The signal control circuits are exactly the same as those of the system of Figs. 1a. -b--c already traced in detail except that battery 90, instead of transformer 29, is the source of current supply. Hence it will suflice to say here that when the relays receive from the associated track circuit energy of the in-phase normal code, the controlled signal S is energized in a manner causing it to dislay the green-over-green or proceed indication; when the received trackway energy is of the displaced normal code, the controlled signal displays the green-over-yellow or caution indication; when the controlling track circuit transmits energy of the in-phase reversed code, the controlled signal displays the yellow-over-yellow or approach indication; when the relays respond to track energy of the displaced reversed code, the controlled signal displays the yellow-over-red or slow indication; and when no energy is received from the trackway, the controlled signal is energized in a manner'causing it to display the red-over-red or stop indication,

In the apparatus of Fig. 3, energy of one or another of the four trackway codes shown in Fig.

2 is supplied from one or the other of the batteries NB and RB to the rails l and 2 of the rear track section byway of contacts of the four relays CR, TR, XI and XD and the

conductors

48 and 50 in a manner very similar to that described in connection with the apparatus shown in Figs. 1a--b-c. As in the case of the firstconsidered system, explanation may best be made by tracing the various circuits under different conditions of system operation. From the description of these circuits which follows, it will be noted that the code-following relay CR is provided with two coding contacts 92 and I08 respectively associated with the batteries above named and that the arrangement of the phase and polarity selecting contacts of the track and auxiliary relays TR, XI and 21D is also somewhat different than, though generally equivalent to, that previously described.

When the relay contacts occupy the positions shown in Fig. 3, the track rails are supplied with energy of the in-phase normal code. This energy originates in the battery NB and the circuit through which it is impressed between the rails may be traced from rail-supply conductor 48 through the current limiting impeder 58, conductor 95, a protective relay contact H8, conductor I06, the battery NB, conductor 9|, the contact 92 (in its front-closed position) of the code-following relay CR, conductors 93 and 94, a contact 96 of relay XI, conductor 91, a contact 98 of relay XD, conductor 99, and a polar contact Hill of relay TR back to rail-supply conductor 50.

When the relay contacts have positions corresponding to those represented at location B in Fig. 1a (TR polar to left, XI down and XD up), the track rails likewise are supplied from battery NB with energy of the in-phase normal code. In this instance, the circuit extends from battery-connected conductor 9|, through the contact 92 (in its front-closed position) ofthe code-following relay CR, conductors 93 and 94. contact 98 of relay XD, conductor 99 and contact I00 of relay TR back to conductor 50.

When the relay contacts occupy positions corresponding to those represented at location C in Fig. 1b (TR polar to right, XI up and 2G) down),

the track rails are supplied with energy of the displaced normal code through a circuit which likewise includes battery NB. This circuit may be traced from conductor 9i through contact 92 (in its back-closed position) of the code-following relay CR, conductor IOI, contact I02 of relay XI, conductor I03, contact I04 of relayXD, conductor I05, and contact I00 of track relay TR back to conductor 50. 7

When the relays maintain their contacts in positions corresponding to those represented at location D in Fig. 11) (TR polar to right, XI down.

and XD up), the track rails are supplied with energyof the in-phase reversed code. In this case, the energy originates in battery RB and is transmitted to the rails through a circuit which may be traced from conductor I06, through the battery RB, conductor I01, the contact I08 (in its front-closed position) of the code-following relay CR, conductor I09, contact I04 of relay XD, conductor I05, and contact I00 ofrelay TR back to conductor 50.

Finally, when the contacts of the relays have positions corresponding to those represented at location E in Fig. 10 (TR polar to left, XI down and XD down), the track rails are supplied from battery RB with energy of the displaced reversed code. The circuit extends from c0nductor I01 through contact I08 (in its back-closed position) of code-following relay CR, conductor III, contact 96 of relay XI, conductor 91', contact 98 of relay XD, conductor 99, and contact I00 of relay TR back to conductor 50.

The signaling system exemplified by the apparatus shown in Fig. 3'operates in exactly the same manner as does the system of Figs. 1a-h-c. That is, when all of the protected blocks are unoccupied, the relays at all of the signal locations receive energy of the in-phase normal code from the rails of the associated track circuit and maintain their contacts in the particular positions represented in Fig. 3. This causes the controlled signal S to show the proceed indication and the rails of the rear track circuit also to be supplied with energy of the proceed code.

When one of the protected blocks is occupied by a train, the short-circuiting of the rails thereof deenergizes the relays TR, XI and XD at the entrance of this block. These relays now drop their neutral contacts causing the controlled signal to; show stop and the track circuit of the next block to receive energy of the displaced reversed code. At the entrance of this second block, the relay TR now shifts its polar contacts to the right and the relay XD picks up its contacts. This causes the controlled signal to display slow and the track circuit of the next block back to receive energy of the in-phase reversed code. I

At the entrance of this third block, the relay now drops its contacts and the relay XI picks up its contacts, thereby causing the controlled signal to show approach and the track circult, of the next block back to receive energy of the displaced normal code. At the entrance of this fourth blockthe relay XI drops its contacts, the relay XD picks up its contacts and the relay TR shifts its polar contacts back to the left to cause the controlled signal to show caution and the track circuit of the next block back to receive energy of the in-phase normal code. At the entrance of this fifth block behind the train the relay contacts have the positions shown in Fig. 3 and produce the effects already described.

Protection against broken-down rail joints may be obtained in the system exemplified by Fig. 3 in the same manner as in the system of Figs. la bc, namely, by staggering both the polarity and the phase characteristics of the energy supplied to the rails of adjacent track circuits.

Considering now the further details of the embodiment of my invention shown in Fig. 4, each of the signal-location equipments comprised by the signaling system there exemplified obtains its energization from a common alternating-current circuit 24 and the energy which it supplies to the rails of the track section to the rear is in the form of coded alternating electromotive force. Interposed between the circuit 24 and each of these equipments is a step-down transformer I26 which corresponds to the device 26 of Fig. 1 and which differs therefrom only in being provided with a secondary windingmade up of two sections NS and RS from which trackway energy of the normal and reversed relative instantaneous polarities is respectively derived.

The four relays CR, TR, XI and XD at each of the signal locations perform functions exactly the same as those performed by the corresponding relays of the two previously described embodiments of my invention. Track relay TR differs in the respect that it is of the alternating current type and in addition to the track winding shown as being directly connected with the rails I and 2 through conductors II and I2, it is also provided with a local or exciting winding I32 which is constantly energized by the output voltage of transformer I26 and which permits the relay to distinguish the relative instantaneous polarity of the energy received from the trackway.

1 The code-following relay CR likewise is shown as being of the alternating current type and the master code circuit 6 with which this relay is connected is represented as being energized by alternating current derived from the main supply circuit 24- through a transformer I5 and the make and break device I of the master coder MC.

The auxiliary relays XI and XD are shown as being of the same direct current type as those of the earlier disclosed systems and their energizing r circuits include a transformer I35 and a rectifier I36. These additional elements convert the alternating current energy supplied from the rails through conductors II and I2 into unidirectional energy of a potential best suited for relay operation.

Interposed between the trackway energy supply winding sections NS and RS at each signal location and the rails I and 2 of the track block to the rear thereof is the usual track transformer IT which reduces the rail-impressed potential to the comparatively low value best suited for track circuit operation and which is connected with the rails through conductors t8 and 50 and currentlimiting impeder 58. Selection of which one of the winding sections NS or RS supplies current to the track transformer is made by contacts carried by the track and auxiliary relays TR, XI and X0 and the coding of this current is effected by contacts 92 and I08 of the code-following relay CR. The above-referred-to contacts form a part of circuits which include a conductor I21 joining (through a protective relay contact NB) the common point of the supply sections NS and RS with one side of the track transformer, conductors I28 and I30 respectively connecting the outer ends of the. two sections named with the coding contacts 92 and I08 of relay CR, and a conductor I31 joining a polar contact I of the track relay TR with the other side of the transformer TT.

The arrangement and interconnection of the relay contacts through which energy is supplied to the track transformer TT is exactly the same as in the corresponding portions of the apparatus of Fig. 3 except that the winding sections NS and RS, instead of batteries N13 and RB, constitute the sources of trackway current supply. When the relay contacts occupy the positions shown in Fig. 4, the track transformer T1 supplies the rails'with alternating-current energy of the in-phase normal code and receives this energy from winding section NS of the transformer I26 through a circuit which includes conductor I28, coding contact 92 (in its front-closed position) of the relay CR, conductors 93 and 94, contact 96 of relay XI, conductor 91, contact 98 of relay XD, conductor 99, polar contact I00 of relay TR, and conductor I31.

When the relay contacts have positions corresponding to those represented at location B in Fig. 1a (TR polar to left, XI down and XD up) the track transformer likewise suplies the rails with energy of the in-phase normal code. In this instance the transformer is connected with the supply winding section NS through a circuit which includes conductor I28, coding contact 92 (in its front-closed position) of relay CR, conductors 93 and 94, contact 98 of relay XD, conductor 99, contact I00 of relay TR and conductor I31.

When the'relay contacts occupy positions corresponding to those represented at location C in Fig. lb (TR polar to right, XI up and X1) down), the track transformer TI supplies the rails with energy of the displaced normal code. This energy also comes from the supply section NS and is transmitted through a circuit which includes conductor I28, coding contact 92 (in its back-closed position) of relay CR, conductor IOI contact I02 of relay XI, conductor I03, contact IM of relay XD, conductor I05, contact I00 of relay TR, and conductor I31.

When the relays maintain their contacts in positions corresponding to'those represented at location D in Fig. 11) (TR. polar to right, XI down and XD up), the track transformer supplies the rails with energy 'of the in-phase reversed code. This energy comes from the winding section RS of the supply transformer I26 and is transmitted through a circuit which includes conductor I30, coding contact I08 (in its frontclosed position) of relay CR, conductor I09, contact I04 of relay XD, conductor I05, contact I00 of relay TR and conductor I31;

Finally, whenthe contacts of the relays have positions corresponding to those represented at location E in Fig. (TR polar to left, XI down and XD downythe track transformer supplies the rails with energy of the displaced reversed code. This energy also comes from the supply section RS and is transmitted through a circuit which includes conductor I30, coding contact I08 (in its back-closed position) of relay CR, conductor III, contact 96 of relay XI, conductor 91, contact 98 of relay XD, conductor 99, contact I00 of relay TR and conductor I31.

The lamps of each controlled signal S are supplied in the apparatus of Fig.4, with energizing current through a transformer 28 which is constantly excited by the output voltage of the supply transformer I 28 and which is selectively connected with the lamps through contacts of relays TR, XI and XI) and interconnecting circuits arranged in the same manner as are those already described as forming a part of the systems of the first and second embodiments of my invention. Hence, it will sufiice to say here that when these relay contacts have the positions shown in Fig. 4, the controlled signal S is caused to display the proceed indication; when the contact positions are as shown at location B in Fig. 1a, the controlled signal shows the caution indication; when the positions are as represented at location C in Fig. 1b, the signal displays the approach indication; when the positions are as represented at location D in Fig. 1b, the signal shows slow; and when the relay contacts have the positions represented at location E of Fig. 1c, the controlled signal is energized in a manner causing it to display the indication of "stop.

Except for the fact that the energy of the trackway codes consists of spaced pulses of alternating electromotive force rather than of unidirectional voltage, the coded trackway energy employed by signaling the system exemplified by Fig. 4 is identical with that previously described in connection with the systems of the first two embodiments of my invention. Thus the in-phase and displaced characteristics with reference to the master code pulses I0 are exactly the same. Polarity comparison likewise is closely comparable and differs only in the respect of being made on a relative instantaneous basis. As has been explained, each of the track relays TB. is arranged through its local winding I32 to distinguish whether the energy received by its track-connected winding is in phase with or displaced from the voltage acting in the main supply circuit 24 and except for this difference, operation of the system now under consideration is exactly the same as that previously explained for the first two embodiments of my invention.

It will be evident from the foregoing that, as in the case of the two systems already described, the signaling system exemplified by the apparatus shown in Fig. 4. is so organized that when all of the protected blocks of track are unoccupied the control equipments at all of the signal locations assume the condition represented at location A. That is, the relay apparatus receives from the rails of the associated track circuit energy of :the in-phase normal code, causes the controlled signal to give the indication of proceed and supplies the in-phase normal" code to the rails of the track block immediately behind.

In the event that a train V occupies one of the blocks, the wheels and axles thereof shunt the signal control potential from between the rails causing the relay apparatus to assume a condition corresponding to that represented at location E in Fig. 1c. Under these conditions, the controlled signal is caused to display the indication of stop and the rails of the track circuit in the immediate rear are supplied with energy of the displaced reversed code.

The-equipment associated with these rails assumes, under the control of this energy, a condition corresponding to that represented at location D in Fig. 1b and causes the controlled signal S to display the indication of "slow and the rails of the track circuit in the immediate rear to be supplied with energy of the in-phase reversed code.

This causes the associated signal control equipment to assume a condition corresponding to that tween these four codes only, it will be understood that my improved equipment may readily be modified to provide for the control of signals having either more or less than the five distinctive aspects hereinbefore explained. For example, uncoded trackway energy of the positive and negative relative polarities may additionally be supplied to the rails to provide a total of seven distinctive forms of signal control.

From the foregoing, it will be seen that the improved organization of signaling apparatus of my invention operates to increase the number of distinctive forms of signal control which are obtained through the use of trackway energy having a limited Variety of forms or codes. That is to say, in the particular systems herein disclosed by way of illustration all four of the trackway codes shown in Fig. 2 are basically similar in character in that they consist of simple pulses of energy spaced in synchronism with the pulses ID of the master code. Yet when compared with this master code in the novel manner evolved by me, they provide four distinct characters of signal control response in the trackenergy receiving apparatus.

The advantages which accrue from this extension are at the same time all attained without directly interconnecting the signal-actuating circuits and by the use of but a single pair of master circuit conductors 6 through which the relay equipments at the several signal locations are supplied with the master code pulses. As has been seen furthermore, my new organization of traffic controlling apparatus is such as to render the resulting signaling syst'em self-protecting against broken-down rail joints and also against accidental interruptions of the master code supply. Still further, I have made provision whereby an accidental failure of the apparatus will cause the controlled signal to display the indication of stop thereby most strongly promoting the interests of safety.

Although I have herein shown and described only three forms of railway traffic controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a section of railway track,

a master-control circuit separate from the track rails and continuously supplied with pulsating energy, a code-following relay located at the entrance end of said section and connected with said circuit to receive operating energy therefrom, means for selectively supplying the rails of said section with coded energizing pulses which are in phase with those of said master circuit and of either normal or reversed polarity or which are' displaced from the master-circuit pulses and of either normal or reversed polarity, a track relay connected with said rails at the entrance end of the section and adapted to respond to coded energy received therefrom and also to distinguish the polarity of said energy, a pair of auxiliary relays also at the entrance end of the section energized from said rails over circuits controlled by said oode-following relay and arranged selectively to respond to rail energy of the said 2. In combination with a forward and a rear section of railway track, a master control circuit separate from the track rails and supplied with continuously recurring pulses of energization spaced to constitute a master code, a code-following relay located at the entrance end of said forward track section and connected with said master circuit to receive operating energy therefrom, means for selectively supplying the rails of said forward section with coded energizing pulses which are in phase with or which are displaced from those of said master code, a track relay connected with said rails at the entrance end of the forward section and adapted to respond to coded energy received therefrom, a pair of auxiliary relays also at the entrance end of the forward section energized from said forward section rails over circuits controlled by said code-following relay and arranged selectively to respond to rail energy of the said in-phase code and of the said displaced code, and means controlled by said track and auxiliary relays for supplying the rails of said rear section of track with energy of one or the other of said in-phase and, displaced codes.

3. In combination, a forward and a rear section of railway track, a master circuit separate from the track rails and supplied with continuously recurring pulses of energization spaced to constitute a master code, a code-following relay located at the entrance end of said forward track section and connected with said circuit to receive operating energy therefrom, means for selectively sup-, plying the rails of said forward section with coded energizing pulses which are in phase with-those of said master code and of either normal or reversed polarity or which are displaced from those of said master code and of either normal or reversed polarity, a track relay connected with said rails at the entrance end of said forward section and adapted to respond to coded energy received therefrom and to distinguish the polarity of said energy, a pair of auxiliary relays also at the entrance end of the forward section energized from said forward section rails over circuits controlled by said code-following relay and arranged selectively to respond to rail energy of the said inphase codes and of the said displaced codes, and means including a coding contact of said codefollowing relay and code-selecting contacts of said track and auxiliary relays for supplying the rails of said rear section of track with energy of one or another of the four trackway codes above named.

4. In a railway signalling system, the combination of a pair of rectifiers respectively adapted to supply the rails of a section of track with energy of normal and of reversed polarity, means for selectively impressing an alternating electrometive force upon said rectifiers, and means responsive to the energization of either of said rectifiers for connecting that rectifier to said track rails.

5. In combination with a plurality of successive sections of railway track, a master-control cir-- cuit separate from the rails of but coextensive with all of said track sections and supplied with continuously recurring pulses of master code energy, a code-following relay located at each point of junction between adjacent track sections and connected with said master circuit to receive operating energy therefrom, means governed by traffic conditions in advance of each of said sections and including a contact of the code-following relay at the exit end of the section for selectively supplying the rails thereof with coded energizing pulses which are in phase with or which up its contacts.

represented at location C in Fig. 1b in which the controlled signal is caused to display the indication of approach and the rails of the track circuit in the rear are supplied with energy of the displaced normal code.

In consequence, the equipment at the next location back assumes a condition corresponding to that represented at location B in Fig. la. Here the controlled signal shows the indication of caution and the rails of the track circuit in the immediate rear are supplied with energy of the "in-phase normal code.

Finally, the equipment at the fifth signal location behind the occupied block is thereby caused to assume a condition corresponding to that represented at location A in Fig. 10;. There the controlled signal S shows the indication of clear or proceed and the rails of the rearward track section are supplied with energy of the in-phase normal code.

Protection against broken-down rail joints may be obtained in the system exemplified by the showing of Fig. 4 in the same manner as in the previously described systems, namely, by staggering both the polarity and the phase characteristics of the energy supplied to the rails of adjacent track circuits.

In all three embodiments of my invention, the arrangement of the apparatus is such that should the master code circuit 6 accidentally cease to transmit energy pulses ID to the code-following relays CR, all of the affected signals S will show restrictive indications which alternately are "stop and slow. This comes about in the following manner:

The contacts of all of the relays CR will, under the conditions stated, drop to their back positions, thereby disconnecting the auxiliary relays XI from the track circuits, connecting the auxiliary relays XD in parallel with the track relays TR and setting up circuits through which energy of the reversed polarity only can be supplied to the rails of the rear track sections. At the signal-location defining the forward end of the stretch of protected track, all three relays TR, XI and IE will then maintain their contacts in the down positions, thereby completing circuits which cause the associated signals to show stop and the track circuit to the rear to receive continuous energy of reversed polarity.

Under the influence of this energy, the track relay TR at the next location back picks up its neutral contacts and biases its polar contacts to the right and the auxiliary relay XD also picks These actions cause the associated signal to show slow and the track circuit to the rear to receive no energy at all.

At the next signal location to the rear the contacts of all three relays TR, XI and XD are accordingly dropped down and complete circuits which cause the associated signal to show stop and the track circuit to the rear to receive continuous energy of reversed polarity. The signal controlled by this energy at the next location back now shows slow and the track circuit to the rear thereof is deenergized. It will thus be seen that in the manner above indicated failure of the master code circuit causes the affected signals alternately to show stop and slow, thereby promoting the interests of safety to a degree adequate for most applications.

Should, however, it be desired that all of the affected signals S will show stop in the event that the contacts of the code-following relay CR at any or all of the locations cease to operate for any cause whatever, this may be accomplished by using the additional protective equipment shown in Fig. 5.

This additional equipment includes a codechecking relay III installed at each signal location and provided with a slow-releasing contact II 8 which is included in the circuit through which energy is supplied to the rails of the track section in the immediate rear. This relay is energized from a rectifier H9 supplied with alternating current by a transformer I which receives from a battery I2 I, or other suitable source, pulses of direct-current energy controlled by the circuit-making and breaking action of a contact I22 which is carried by the code-following relay CR of the regular location apparatus.

Normally this contact establishes and interrupts' (and also alternately reverses) the transformer energizing circuit in synchronous timing with the master code pulses III which act in the circuit '6. This induces in the transformer secondary an alternating electromotive force which is converted by the rectifier I I9 into closely spaced pulses of unidirectional current which flow through the winding of the relay III. The contact II8 of that relay, being slow releasing, is thereby held in the upward or front position shown in which the normal track-energy-supply connection is established. Should, for any cause, the code-following relay CR cease to operate, the stoppage of contact I22 thereof interrupts the supply of pulsating energy to the transformer I 20 with the result that actuating energy is no longer supplied through the rectifier to the relay. In consequence, the contact I I8 drops to the lower or back position and thereby opens the trackway energizing circuit to prevent energy of any character from being supplied to the track rails.

The relay apparatus which is controllably connected to these rails at the opposite or trafficentering end of the block now responds in the same manner as were the rails to be short circuited by the wheels and axles of a train V. Hence, until operation of the code-following relay CR is again restored, the controlled signal S is caused to display the indication of stop.

The code-checking equipment just described is shown as forming a part of the apparatus represented in each of Figs. 3 and 4 and may be adapted for use in the signaling system of Figs. 1a b c in the manner indicated in Fig. 5. In the adaptation shown in Fig. 4 direct current for energizing transformer I2!) is derived from the output of the main supply transformer I26 through a rectifying and filtering circuit which includes elements I40, MI and I42 interconnected in well-known manner.

Referring to Fig. 6, it will be seen that a single master code circuit 6 may be utilized to supervise the operation of signal control apparatus associated with more than one railway track. In the showing of this figure, two tracks respectively consisting of rails I and 2 and rails DI and 02 are represented by way of illustration of this plural application. In such an installation, of course, a single circuit 24 for supplying operating energy to the equipments may also be made to serve all of the several railway tracks by means of connections of the character represented.

While I have described my invention as being incorporated in apparatus which supplies only four codes to the trackway and have shown signal governing means adapted to distinguish beare displaced from those 'of said master code, track-relay apparatus connected with the rails of each of said sections at the entrance end there of and controlled by the said code-following relay at the same location in such manner as to respond selectively when said rails transmit thereto energy of the said in-phase and displaced codes respectively, and a traffic-governing signal positioned at the entrance of each of said track sections and controlled by the said track-relay apparatus at the same location. I

6. In combination with a plurality of railway tracks each of which includes a number of successive sections, traffic-governing equipment positioned at the entrance end of various sections of each of said different tracks, a master control circuit separate from the rails of but coextensive with all of said governed track sections and supplied with continuously recurringpulses of master code energy, a code-following relay located at the entrance end of each of said governed sections and connected with said master circuit to receive operating energy therefrom, means includinga contact of the code-following relay at the entrance of the next track section in advance for selectively supplying the rails of each of said sections with coded energizing pulses which are in phase with or displaced from those of said master code, and track-relay apparatus connected with therails of each of said sections at the entrance end thereof and acting jointly with said code-fol" lowing relay at the same location to control said traffic-governing equipment at that location.

'7. In a railway signalling system, the combination of a code-following relay, means for supplying said relay with continuously recurring pulses of master code energy, a track relay which responds to energy in recurring pulse form, means for selectively supplying said track relay with pulses of coded trackway energy which are in phase with or displaced from the pulses of said master code, a pair of delayed-releasing auxiliary relays, circuit means controlled by said code-fol lowing relay for supplying one of said auxiliary relays with the iii-phase code pulses only of said trackway energy, other circuit means controlled by said code-following relay for supplying the other of said auxiliary relays with the displaced code pulses only of said trackway energy, a traffic-governing signal, and control circuits for said signal which include contacts carried by said track and auxiliary relays.

8. In a railway signalling system, the combination of a code-following relay, means for supplying said relay with continuously recurring pulses of master code energy, a track relay which responds to energy in recurring pulse form, means for selectively supplying said track relay with pulses of coded trackway energy which are in phase with or displaced from the pulses of said master code, a pair of delayed-releasing auxiliaryrelays, circuit means controlled by said code-following relay for supplying one of said auxiliary relays with the in-phase code pulses only of said traclzway energy, other circuit means controlled by said code-following relay for supplying the other of said auxiliary relays with the displaced code pulses only of said trackway energy, and circuits including contacts of said relays for supplying trackway energy which is additional to that referred to above and which is of one or the other of said in-phase and displaced trackway codes.

9. In a. railway signalling system, the combination ora code-following relay, means for sup:

plying said relay with continuously recurring pulses of master code energy, a polarized track relay, means for selectively supplying said track relay with pulses of coded trackway energy which are in phase with or displaced from the pulses of said master code and which are of either normal or reversed polarity, a pair of delayedreleasing auxiliary relays, circuit means controlled by said code-following relay for supplying one of said auxiliary relays with the inphase code pulses only of said trackway energy, other circuit means controlled by said code-following relay for supplying the other of said auxiliary relays with the displaced code pulses only of said trackway energy, a traflic-governing signal, and control circuits for said signal which include contacts of said track and auxiliary relays.

10. In a railway signalling system, the combination of a code-following relay, means for supplying said relay with continuously recurring pulses of master code energy, a polarized track relay, means for selectively supplying said track relay with pulses of coded trackway energy which are in phase with or displaced from the pulses of said master code and which are of either normal or reversed polarity, a pair of delayed-releasing auxiliary relays, circuit means controlled by said code-following relay for supplying one of said auxiliary relays with the in-phase code pulses only of said trackway energy, other circuit means controlled by said code-following relay for supplying the other of said auxiliary relays with the displaced code pulses only of said trackway energy, and circuits including contacts of all of said relays for supplying trackway energy which is additional to that referred to above and which is of one or another of the said four trackway codes above named.

11. In combination with a forward and a rear section of railway track, a master-control circuit separate from the track rails and supplied with continuously recurring pulses of master code energy, a code-following relay located at the entrance of each of said sections and connected with said master circuit to receive operating energy therefrom, track-relay apparatus at the entrance end of each of said forward and said rear track sections connected to receive energy from the rails of that section over a circuit controlled by the said code-following relay at the same location, a signal positioned at the entrance of each of said sections and controlled by the said trackrelay apparatus at the same location, means controlled by the code-following relay and trackrelay apparatus at the entrance of said forward sectionfor supplying coded energy to the rails of said rear section, and means responsive to a stoppage of said forward-section code-following relay for discontinuing the said supply of the energy last named whereby to cause said rear-section signal to display its most restrictive aspect.

12. In a railway signalling system, the combination with a section of railway track of means at the exit end of the section for supplying coded energy to the rails thereof, a code-following relay forming a part of said means and operated by continuously recurring pulses of master code energy received from a master-control circuit which is separate from the track rails, a signal at the entrance end of said track section, trackrelay apparatus also at said entrance end for controlling said signal in accordance with the character of the coded energy which is received at that location from the rails ofthe section, and means efiective upon an accidental stoppage of said code-following relay at the exit end of the section for preventing said signal at the entrance end of the section from displaying an indication which is less restrictive than that resulting from normal operation of the system.

under the particular conditions in effect at the time of said accidental stoppage.

13. In combination with a forward and a rear section of railway track, a code-following relay at the entrance end of said forward section, a master-control circuit separate from the track rails for supplying said relay with continuously recurring pulses of master code operating energy, a track relay connected in energy-receiving relation with the rails of said forward track section and located at the entrance end thereof, means governed by advance trafiic conditions .for selectively supplying said forward-section rails with pulses of coded energy which are in phase with or displaced from those of said master code and which are of either normal or reversed polarity, a pair of auxiliary relays also located at the entrance end of said forward section, circuit means controlled by said code-following relay for supplying one of said auxiliary relays with the in-phase code pulses only of said trackway energy and the other with the displaced code pulses only of that energy, a pair of rectifiers respectively connected with the rails of said rear track section in normal and reversed polarity relation, contacts carried by said track and auxiliary relays for selectively preconditioning for one or the other of said two lrectifiers the entrance end of said forward section, a

master-control circuit separate from the track rails for supplying said relay with continuously recurring pulses of master code operating energy,

a track relay connected in energy-receiving relation with the rails of said forward track section and located at the entrance end thereof, means governed by advance traflic conditions for selectively supplying said forward-section rails with pulses of coded energy which are in phase with or displaced from those of said master code and which are of either normal or reversed polarity, a pair of auxiliary relays also located at the entrance end of said forward section, circuit means controlled by said code-following relay for'supplying one of said auxiliary relays with the inphase code pulses only of said trackway energy and the other with the displaced code pulses only of that energy, a source of direct-current voltage, contacts carried by said track and auxiliary relays for selectively preconditioning one or another' of four circuits through which the rails or said rear track section may respectively be supplied with in-phase energy of either normal or reversed polarity or with displaced energy of either normal or reversed polarity, and contacts carried by said code-following relay for connecting each in-phase supply circuit which is preconditioned with said source during spaced periods which are in phase with the energy pulses of said master code and each displaced supply circuit which is preconditioned with said source during spaced periods which are displaced from said master code energy pulses. a

15. In combination with a forward and a rear section of railway track, a code-following relay located at the entrance end of said forward sec-- tion, a master-control circuit separate from the track rails for supplying said relay with continuously recurring pulses of master code operating energy, a source of alternating electromotive force, a track relay at the entrance end of said forward section having a local winding connected with said source and a track winding connected in energy-receiving relation with the rails of said forward section, means governed by advance traffic conditions for supplying said rails with pulses of coded alternating voltage which are in phase with or displaced from the pulses of said master code and which have an instantaneous polarity which is either normal or reversed with respect to that of the alternating electromotive force above mentioned, a pair of auxiliary relays also located at the entrance end of the forward section, circuit means controlled by said codefollowing relay for supplying one of said auxiliary relays with the in-phase code pulses only of said trackway energy and the other with the displaced code pulses only of that energy, contacts carried by said track and auxiliary relays for selectively preconditioning one or another of four circuits through which the rails of said rear track section may respectively be supplied with in-phase energy of either normal or reversed relative instantaneous polarity or with displaced energy of either normal or reversed polarity, and contacts carried by said code-following relay for connecting each in-phase supply circuit which is preconditioned with said source during spaced periods which are in phase with the energy pulses of said master code and each displaced supply circuit which is preconditioned with said source during spaced periods which are displaced from said master code energy pulses.

' 16. In combination with a section of railway track, a master-control circuit separate from the track rails and supplied with continuously recurring pulses of master code energy, a code-following relay at the entrance end of said section connected to said master circuit and operated by the said energy pulses present therein, means at the exit end of said section for selectively supplying the rails thereof with pulses of coded trackway energy which are in phase with or which are displaced fromthe pulses of said master code, a track relay connected to said rails at the entrance end of the section and responsive to recurring pulses of energy received therefrom, an auxiliary relay similarly located and also responsive to energy in recurring pulse form, a circuit extending from said rails and controlled by said codefollowing relay for supplying said auxiliary relay with the energy pulses of a given one of said two trackway codes only, and trafiic-governing apparatus controlled by the relays above named.

17. In combination with a section of railway track, a master-control circuit separate from the track rails and supplied with continuously recurring pulses of master code energy, a code-following relay connected to said master circuit and operated by the said energy pulses present therein, means for selectively supplying the rails of said track section with pulses of coded trackway energy which are in phase with or which are displaced from the pulses of said master code, a track relay connected to said rails and responsive to recurring pulses of energy received therefrom, a first auxiliary relay connected to said rails by said code-following relay during each on period of the master code and arranged to receive and respond to energy pulses of said in-phase trackway code only, a second auxiliary relay connected to said rails by said code-following relay during each off period of the master code and arranged to receive and respond to energy pulses of said displaced trackway code only, and traficgoverning apparatus controlled by the relays above named.

18. In combination with a section of railway track, a master-control circuit separate from the track railsand supplied with continuously recurring pulses of master code energy, a code-following relay connected to said master circuit and operated by the said energy pulses present therein, means for selectively supplying the rails of said track section with coded energizing pulses which are in phase with those of said master code and of either normal or reversed polarity or which are displaced from those of said master code and of either normal or re versed polarity, a track relay connected to said rails and adapted to respond to recurring energy pulses received therefrom and to distinguish the polarity of said pulses, a first auxiliary relay energized from said rails under the control of said code-following relay and arranged to receive and respond to energy pulses of said inphase trackway codes only, a second auxiliary relay also energized fro-m said rails under the control of said code-following relay but arranged to receive and respond to energy pulses of said displaced trackway codes only, and traffic-governing apparatus controlled by the relays above named.

19. In combination with a forward and a rear section of railway track, a master-control circuit separate from the track rails and supplied with continuously recurring pulses of master code energy, a code-following relay at the point of junction of said track sections connected to said master circuit and operated by the said energy pulses present therein, means for selectively supplying the rails of said forward section with pulses of coded trackway energy which are in phase with or which are displaced from the pulses of said master code, a track relay at the entrance end of said forward section connected to the rails thereof and responsive torecurring pulses of energy received therefrom, an auxiliary relay energized from said forward section rails under the control of said code-following relay and arranged to receive and respond to energy pulses of one of said two trackway codes only, a circuit through which energy may be supplied to the rails of said rear track section, a contact of said code-following relay included in said circuit for the purpose of coding said energy, and means including contacts of said track and auxiliary relays for determining section with whether the pulses of said rear-section coded energy are in phase with or displaced from the pulses of said master code.

20. In combination with a forward and a rear section of railway track, a master-control circuit separate from the track rails and supplied with continuously recurring pulses of master code energy, a code-following relay at the point of junction of said track sections connected to said master circuit and operated by the said energy pulses present therein, means for selectively supplying the rails of said forward pulses of coded trackway energy which are in phase with the pulses of said master code and of either normal or reversed polarity or which are displaced from said master code pulses and of either normal or reversed polarity, a track relay at the entrance end of said forward section connected to the rails thereof and adapted to respond to recurring energy pulses received therefrom and to distinguish the polarity of said pulses, first and second auxiliary relays energized from said forward section rails under the control of said code-following relay and respectively arranged to receive and respond to energy pulses of said in-phase and said displaced trackway codes only, a circuit through which energy may be supplied to the rails of said rear section of track, a contact of said code-following relay included in said circuit for the purpose of coding said energy, and means including contacts of said track and auxiliary relays for determining whether said rear section code pulses are in phase with or displaced from the pulses of said master code and Whether the energy of those rear section pulses is of normal or reversed polarity.

21. In combination with a plurality of successive sections of railway track, a master-control circuit separate from the rails but coextensive with ,all of said track sections and supplied with continuously recurring pulses of master code energy, a code-following relay located at each point of junction between adjacent track sections and connected with said master circuit to receive operating energy there-from, trackrelay apparatus also located at each of said junction points and connected to receive energy from the rails of the track section ahead of that point, means including a contact of said code-following relay at the same location for rendering said track-relay apparatus at each location selectively responsive to pulses of received trackway energy which are in phase with and which are displaced from the pulses of said 'master code, a signal positioned at the entrance end of each track section and controlled by said track-relay apparatus at the same location, and means also controlled by the track-relay apparatus at each location and including a second contact of the code-following relay at the same location for selectively supplying the rails of the track section to the rear with coded energizing pulses which are in phase with or which are displaced from the pulses of said master code energy.

HOWARD A. THOMPSON.

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