US2360208A - Railway traffic controlling apparatus - Google Patents

Description

Oct. 10,1944. G. A. cuLBERTsoN RAILWAY TRAFFIC CONTROLLING APPARATUS Filed May 29, 194s Patented Oct. 10, 1944 saugte RAILWAY TRAFFIC CON'TROLLING APPARATUS George A. Culbertson, Long Branch, N. J., assignor to The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania,

Application May 29, 1943, Serial No. 489,020

7 Claims.

My invention relates to railway traiiic controlling apparatus, and has particular relation to the organization of such apparatus into railway traffic controlling systems of the class adapted to control the movements of traffic in either direction over a stretch of single track railway.

Railway traffic controlling systems of the class described usually incorporate a traiic locking circuit which functions to prevent a change of traffic direction while the stretch is occupied. Such a circuit includes means, controlled either automatically by the approach of a train or manually by an operator, effective to establish the desired direction of traic and so arranged that once a direction of traffic has been established and a signal has been cleared to authorize trafc to move in the established direction, operation of the means governing the establishment of the opposite direction of trafc will not result in placing the cleared signal at stop. In other words, the circuit is arranged so that an established direction of traic cannot be cancelled by an operation of the control means governing the establishment of the opposite direction of traffic.

My invention has for an object the provision of novel and improved means arranged for use with a traflic locking circuit for preventing operation of the control means governing the establishment of the opposite direction of traffic from effecting cancellation of an established traffic direction.

Another object is the provision in a traffic v lockingcircuit of novel and improved means for maintaining the energization of the locking relay once a direction of traic has been established.

A further object is the provision in a traffic locking circuit of novel and improved means for establishing preference to traffic movements in a given direction.

The above-mentioned and other important objects and characteristic features of my invention which will become readily apparent from the following description are attained by providing each of the locking relays incorporated into a trafc locking circuit with stick circuit means effective to provide a stick circuit when a locking relay is picked up and the control means associated with the opposite direction of traffic is caused to operate. Also incorporated into such traflic locking circuit are means governed by the trailic controlling means for granting preference to a predetermined direction of traiiic.

I shall describe one form of apparatus embodying my' invention and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic View illustrating one form of apparatus embodying my invention.

Referring to the drawing, the line diagram at the top of the drawing illustrates a stretch of single track railway over which traic moves in either direction between two locations D and E. As shown, location D includes a track switch l leading from a main track to a second track DS, and location E includes a track switch 2 leading from the main track to a second track ES. Traino on the main track at locations D and E is normally in the eastbound direction, or from left to right as viewed in the drawing and as indicated by the arrows associated with the main track at such locations, while traffic on the second tracks at locations D and E is normally in the opposite or Westbound direction, as indicated by the arrows associated With such second tracks. l

The main and second tracks are divided in the customary manner intotrack sections, designated by the reference characters T with suitably distinguishing prexes. Each of these sections is provided in accordance with the usual practice with a normally closed track circuit including a track relay, designated by the reference character TR with a prefix corresponding to the prefix of its associated track section, the association of each relay with its track section being indicated conventionally by a dash line. To assist in tracing circuits later to be described in detail, contacts of relays have in some instances been represented remote from the associated relays, but in each of. such cases the contact has been identified by a reference character individual to such contact and by the reference character of the associated relay. For example, contact 53 bears the reference character A4TR to indicate that this contact is associated with relay AGTR.

The reference characters 5 and IZdeSignate signals which are provided adjacent to locations D and E for governing eastbound and westbound traiiic movements respectively over fthe single track stretch between the two locations. These signals may be of any suitable typel and are shown, for example, as light signals each of which comprises a green lamp G effective when illuminated to indicate clear and a red lamp R. effective when illuminated to indicate stop. Signals 6 and Il are also provided adjacent to locations D and E for governing westbound and eastbound movements over switches I and 2 respectively. These signals are shown, for example, as light signals and each comprises a yellow lamp Y effective when illuminated to indicate proceed and a red lamp R elective when illuminated to indicate stop. In addition, other signals (not shown) may be provided if desired at points intermediate locations D and E for governing the approach of trafc to signals 6 and II, but since the control of such intermediate` signals does not form any part of my present invention, such signals have been omitted in order to simplify the drawing and description.

The reference characters HR with suitably distinguishing prexes designate signal control relays for controlling signals 6 and II. Each signal 6 and II is controlled by its associated control relay HR in such a manner that the yellow lamp Y or red lamp R is illuminated according as the associated signal control relay is picked up or released, respectively. Relay SHR associated with signal 6 is normally energized over a circuit extending from one terminal B of a suitable source of current, such as a battery not shown, through front contact 52 of relay 56TR, front .contact 53 of relay A4TR and the winding -of relay BHR to the other terminal C of the same source of current; While relay IlI-IR associated with signal II is normally energized over a circuit which extends from terminal B through front contact 54 of relay I I-I2TR, front contact -55 of relay AI3TR, and the winding of relay I IHR to terminal C.

The reference characters J with suitably diS- tinguishing prefixes designate directional relays for controlling signals 5 and I2. and I2 is controlled by its associated directional relay J in such a manner that the green lamp G or red lamp R is illuminatedk according as the associated directional relay is picked up or released, respectively.

The two directional relays DJ and EJ which control signals 5 and I2, respectively, are in turn controlled by means of a traffic locking circuit which includes a source of current, a locking relay, and a directional relay at each end of the single track stretch, together with a pair of line wires which extend between the ends of the single track stretch. The-two sources, which may for example comprise batteries designated bythe reference character BS with suitably distinguishing prexes, are normally connected in series D- position and in circuit with both locking relays, designated by the reference characters LR with suitably distinguishing prefixes, over the two line wires I and I6. Included in the trailc locking circuit are front contacts of each of the track relays of the sections intermediate the two opposing signals, as Well as normally closed contacts, of control means, herein shown as front contacts of the track relays of the two sections A5T and AI 2T in approach of signal 5 and I2, respectively. As shown, the traic locking circuit is arranged on the double break principle wherein each wire of the line circuit has interposed therein a front Each signal 5:

contact of each track relay so that whenever `a f track relay releases, both wires will be opened. The traflic locking circuit may be traced from one terminal of battery DBS through a resistor I8, the winding of locking relay DLR, front contact I9 of relay A5TR, line wire I5, front contacts 20, 2l, 22, 23, 24, 25 and 25, of relays E-GTR. STR,V ASTR, ASJ'IR,y STR, II--I2TR and AIZTR, respectively, the Winding of relay ELR, resistor 2-1, the corresponding one terminal of battery EBS.,

the other terminal of battery EBS, front contact 29 of relay AI2TR, line Wire IB, and front contacts 30, 3|, 32, 33, 34, 35 and 35, of relays II-lZTR, ASTR, ASTR, tTR, ,Ea-STR and AETR, respectively, to the other terminal of battery DBS. With the batteries DBS and EBS connected in opposing relation and adjusted to have substantially the same terminal voltage, relays DLR and ELR are of course normally deenergized and released.

The line circuit is so arranged that whenever either approach track relay A5'IR or AI2TR is released, the battery BS and locking relay LR at the adjacent end of the traflic locking circuit is then disconnected from the line wires I5 and I6 and the direcctional relay J at that end of the traiiic locking circuit is connected with such line wires to complete a circuit which causes that directional relay and the locking relay at the opposite end of the trallc locking circuit to become energized in response to current supplied from the battery at the opposite circuit end. For eX- ample, if relay |A5IR is released when all other track relays are picked up, then battery DBS and relay DLR are disconnected from the wires I5 and I5 at front contacts I9 and 36 of relay ASTR, while relay DJ is connected, over back contacts 31 and 38 of relay DLR and back contacts 39 and 49 of relay A5TR, to wires I5 and I6 sor that relays DJ and ELR become energized in series by current supplied from battery EBS. Similarly, if relay AI ZTR is released but all other track relays are picked up, then battery EBS and relay ELR are disconnected from the wires I5 and I6 at front contacts 2B and 29 of relay AIZTR, while relay EJ is connected, over back contacts 4I and 42 of relay ELR and back contacts 43 and 44 of relay AIZTR, to wires I5 and IB so that relays EJ and DLR become energized in series by current supplied from battery DBS.

The trafiic locking circuit is further arranged so that when either locking relay is picked up due to a train entering an approach section, that locking relay prepares for itself a stick circuit which functions to hold that relay energized in the event that an opposing train subsequently enters the other approach section before the rst train enters the Single track stretch. For example, if an eastbound train enters section A5T when all other sections are vacant, relay ASTR will release and connect relays DJ and ELR in series with battery EBS, as pointed out hereinbefore, so that relays DJ and ELR will pick up. Relay ELR will of course open its back contacts 4I Vand 42 to disconnect relay EJ from the line circuit, and will close its front contacts 45 and 46. If, now, a westbound train subsequently enters section AIZT before the first train enters section 5-6'1, and relay AI2TR releases to open its front contacts 26 and 29 to interrupt the previously traced circuit over which relay ELR is picked up, that relay will be held up over a stick circuit which includes its front contacts 45 and 46 and back contacts 43 and 44 of relay AIZTR, as can be seen from an inspection of the drawing'. Re-A lay ELR accordingly maintains its back contacts 4I and 4.2 open to disconnect relay EJ from the line circuit, thereby locking signal I2 in its stop position. Similarly, if a westbound train enters section AIZT when all other sections are Vacant, relay AIZTR will release and connect relays EJ and DLR in series with battery DBS, as pointed out hereinbefore, so that relays EJ and DLR Will pick up. Relay DLR will of course open its back contacts 31 and 38 to disconnect relay DJ from the line circuit, and will close its front contacts 41 and 48 so that if an eastbound train subsequently enters section AT before the westbound train enters the single track stretch, and relay A5'I'R releases to open its front contacts I9 and 36 to interrupt the previously traced circuit over which relay DLR is picked up, that relay will be held up over a stick circuit which includes its front contacts 41 and 48 and back contacts 39 and 40 of relay A5TR. It follows, therefore, that when either approach section A5T or AI 2T is entered by a train and all other sections are vacant, the trafc locking circuit is then controlled to establish a corresponding direction of traffic, and that even though another approach section subsequently becomes occupied, the established direction of traffic will be maintained by virtue of the stick circuit provided for .the locking relay energized for that direction of traiiic.

'I'he traffic locking circuit is further arranged to grant precedence to a predetermined trac direction in the event lthat `both approach sections A5T and AIZT become occupied while the stretch is occupied. This is accomplished in a manner to lbe made clear in the following description, and at times this involves the use of an auxiliary relay X having slow pick-up and release characteristics and provided with an obvious energizing circuit which extends from terminal B through front contacts 6I, 62, 63 and 64 of relays III2TR, AI2TR, ELR and EJ respectively, and the windingof relay X to terminal C.

i The apparatus is in its normal condition, as represented in the drawing, when all sections are vacant. In this condition of the apparatus, signals 5 and I2 display stop, while signals 6 and I I display caution.

If an eastbound train enters section A5T with all other sections vacant, relays DJ and ELR become energized and signal 5 is cleared, as pointed out hereinbefore. When the train proceeds through the stretch, the track relays 5 B'I'R, STR, ABTR, etc., of the main line stretch of track, are all successively shunted and each releases to open its front contacts and thereby open the circuit of relay DJ, so that relay D'J releases to place signal 5 at stop. 'Ihe locking relay ELR is, however, held energized since each track relay in releasing closes its back contacts to complete obvious shunt paths connecting wire l5 to wire I6 and completing circuit paths over which Ibattery EBS supplies ener-gy to relay ELR. 'I'his relay is maintained energized until the eastbound train vacates the single track stretch, whereupon relays ELR and DLR are connected in series with batteries DBS and EBS, and since these batteries are poled in opposition? the relays DLR and ELR are deenergized and relay ELR acordingly releases.

If a westbound train enters section AI 2T with all other sections vacant, relays DLR and EJ become energized and signal I2 is cleared. When the train proceeds through the stretch, relays II--I2TR, STR, ASTR, etc., of the main line stretch of track, are in turn successively shunted and released. When relay II-IZTR releases,

it interrupts at its front contacts and 3D the previously traced circuit over which relays DLR. and EJ are energized, so that both relays release and signal I2 is placed at stop. Then, after the train vacates section AI2T, relay ELR becomes energized over an obvious circuit which includes battery EBS, front contacts 26 and 29 of relay AIZTR and back contacts'51 and 58 of relay I I- IZTR. Relay ELR is maintained energized when the train proceeds through the stretch, because each track relay of the main line stretch in releasing co'rnpletes a shunt path which connects wire I5 to wire I6 and which maintains the energization of relay ELR, as is obvious from an inspection of the drawing. After the train vacates the single track stretch, relays DLR and ELRV are connected in series with the two batteries DBS and EBS, which batteries are connected in opposing relation so that relay ELR accordingly will release.

As pointed out hereiirbefore, whenever either relay DLR or ELR is picked up due to a train entering the appropriate approach section, that relay will be held up if the other approach section becomes occupied, thereby providing means for preventing a .train entering an approach section from cancelling an established direction of traiic.

In addition, the energization of a particular one of the locking relays whenever a train operating in either direction occupies (the single track portion of the stretch insures granting preference to a predetermined direction of traffic should lboth approach sections be occupied. The

trame locking circuit is specifically arranged tov grant preference to eastbound traic, but it will be understood, of course, that the circuit may be rearranged to grant preference to westbound traic, if desired. The traffic preference is granted due to the fact that relay ELR is held up whenever a train occupies the single track portion of the stretch, hence if at that time both approach sections A5T and AIZT become occupied,

the apparatus is conditioned to clear signal 5 after the train in the single track portion clears -that portion. In other words, if an eastbound train is on the track between locations D and E, and both sections A5T and AIZT become occupied, then when the train vacates the stretch and enters'section AI3T, relays DJ and ELR will be energized in series over a circuit including front contacts 45 and 46 of relay ELR and back contacts 43 and 44 of relay AIZTR and lback contacts 39 and 43 of relay ll.t'i'l'l'-t. This will result in clearing signal 5 and holding locking relay ELR energized. On the other hand, if the train in the stretch is a westbound train, 'thesame result follows when the westbound train vacates the single track portion since relays DJ and ELR will` be connected in series 'by virtue of the stick circuit of relay ELR.

The apparatus embodying my invention Voperates in the manners just described to grant preference of movement to eastbound traffic under all conditions of traffic except that condition established when the following three 'things ocour: (1) a westbound train enters section AIZT with all other sections vacant, (2) another westbound train enters section AiZT 4before the rst westbound train vacates section AI2T, and (3) an eastbound train enters section A5T prior to the iirst westbound train clearing section 5-6T at the western end of the single track stretch.

I shall first describe how the apparatus thus far described would operate under the conditions assumed. When (1) the rst westbound train enters section AIZT, relays DLR and EJ would be picked up and signal I2 would become cleared. Then when (2) the second westbound train enters second. AI 2T before the first train clears that section, relays EJ and DLR would become released when the iirst train enters section II-I2T and relay I I -I2TR opens its front contacts 25 and 30, and in addition relay AIZTR would be held released by the second train in section AI2T after the rst train vacates the section. As a result, therefore, relay ELR could not be become picked up over its previously traced circuit including back contacts 51 and 58 of relay II-IZTR and front contacts 25 and 29 of relay AIZTR. With relay ELR released, it is apparent that when (3) the eastbound train enters section AST before the first westbound train clears section 5-6'1, relay A5TR would release to close its back contacts 39 and 40' so that both relays DJ and EJ would be connected in series with each other after the iirst westbound train clears section 5-6TR. These relays would therefore remain released because their circuit would include no source of current, As a result, both signals 5 and I2 would then be locked in their respective stop positions even though sections A5T and AI 2T are occupied.

To avoid this locked up condition of the signals, relay X is employed and is arranged to pick up only when (l) a first westbound train enters section AI2T and (2) a second westbound train enters section AI2T prior to the iirst train clearing that section. When (1) the rst train enters section AI2T, relay X is not picked up because relay EJ becomes energized and picks up to open its back contact 64 before the elapse of the slow pick-up interval of relay X. When (2) the second westbound train enters section AIZT before the rst train vacates the section, relay X is picked up after the rst train clears section I I -I 2T because the energizing circuit of relay X is completed since (a) back contact 62 of relay AI 2TR is held closed due to the second train in section AI2T; (b) back contact 63 of relay ELR is closed because that relay was held released by the presence of the second train in section AI2T, as pointed out hereinbefore; 64 of relay EJ is closed because relay EJ was released when the f1rst train entered section I'I-I2.'I; and (d) front contact 6I of relay II- I2TR closes to complete the circuit of relay X when the first train clears section I I-I 2T. Relay X accordingly picks up at the end of its slow` pick-up period, and closes its front contact 60 to complete an obvious auxiliary circuit including that contact, battery EBS and the winding of relay ELR. Relay ELR thereupon picks up and closes its front contacts 45 and 46 to prepare its stick circuit which is completed, in the manner pointed out in detail hereinbefore, at the back contacts of each of the track relays of the single track stretch as those relays become successively released when the rst westbound train proceeds through the stretch. With relay ELR picked up, its back contact 63 is open to interrupt the circuit of relay X, whereupon relay X releases and in turn opens its front contact 6D to interrupt the auxiliary circuit of relay ELR but the latter relay is of course retained energized-over its stick circuit. As a result, therefore, after the first westbound train clears section S-BT, relays DJ and ELR are connected in series With battery EBS and relay DJ accordingly picks up to clear signal 5 and thereby establish the preferred direction of traino.

From the foregoing, it is readily apparent that I have provided novel and improved means adapted for use with a trahie locking circuit to prevent operation of the control means governing the establishment of one direction of trafficfrom effecting cancellation of an established train direction.

(c) back contactA Although I have herein shown and described only one form 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: f

l. In a railway traffic controlling system for us with a stretch of railway track provided at opposite ends with signals for governing traffic in opposite directions in said stretch, said system including a traffic locking circuit which extendsv between the ends of said stretch and which connects a source of current and a locking relay at one end of the stretch in series relation with another source of current and another locking relay at the opposite stretch end, said sources of current being poled in opposition, means controlled by trac in said stretch for governing said locking circuit, two directional relays one for each end of said stretch, means governed by each of said two directional relays for controlling the signal at the adjacent end of said' stretch, means governed by traiiic approaching either end of said stretch for disconnecting the source and' locking relay at the adjacent one end of said stretch from said traffic locking lcircuit and for connecting the directional relay at such one end in circuit with the source and locking relay at the opposite stretch end whereby to cause said one end directional relay and said other end locking relay to pick up, and means governed by trafc approaching the opposite end of said stretch efective when. said other end locking relay is pickedr up to maintain the connection of the source and locking relay at said opposite stretch end withA said ydirectional relay at said one stretch end over a circuit including a front contact of said Iother end locking relay.

2. In a railway trahie controlling system for use with a stretch of railway track divided into a plurality of successive adjoining track sections` each provided with a track circuit including a track relay, said system including signals at opposite ends of said stretch for governing trafilc in opposite directions in said stretch, said system including two approach sections one for either end of said stretch and each provided with a track circuit including an approach track relay, said system also including a traiiic locking circuit which extends between the ends of said stretch and which includes front contacts of all of said track relays and front contacts of said approach track relays, said traffic locking circuit including a source of current and a locking relay at each end of said traic locking circuit normally connected in series relation with said sources poled in opposition, said trafc'locking circuit having associated therewith two directional relays one for each end of said circuit and each controlling means for governing the signal at the adjacent end of the stretch, said traffic locking circuit including means controlled by each approach track relay when released for disconnecting from that circuit the associated source and locking relay at the adjacent end of said circuit and for connecting to that circuit the directional relay at that end of said circuit, and means controlled by each traic locking relay when picked up or preparing a stick circuit path effective to maintain energization of said traffic locking relay should the approach track relay at the adjacent end of the stretch become released during the interval that said traic locking relay is picked up.-

'associated therewith two directional 3. In a railway trafiic controlling system for usewith a stretch of railway track dividedjinto a plurality of successive adjoining track sections each provided with a track circuit including a track relay, said system including signals at opposite ends of said stretch for governing traic in opposite directions in said stretch, said system including a trafc locking circuit having two Aline wires extending between the ends of said stretch and including front contacts of each of" "said track relays, said traffic locking circuit also including two sources located respectively at opposite ends of said circuit and two locking relays also located respectively at the opposite circuit ends, said two sources and two relays normally being connected in series with said sources poled in opposition, said traine locking circuit having relays locatedrespectively at opposite ends of said circuit for governing the signal at the adjacent end lof the stretch, two control means one for each end of said traffic locking circuit and each effective when it is the first of the control means to be operated to disconnect the source and locking relay at the adjacent circuit end from said traflic locking circuit and to connect the directional relay at the adjacent circuit end to said traffic locking circuit, and means controlled by each locking relay when picked up for preparing a stick circuit path including its own front contact and effective to maintain energization of said locking relay in the event that the control means at the adjacent circuit end becomes operated during the interval that said locking relay is picked up.

4. In combination with a stretch of railway track provided at opposite rends with signals for governing traic movements in opposite directions in said stretch, a circuit comprising two line wires extending between the opposite ends of said stretch, two sources of current located respectively at opposite ends of said circuit, two locking relays located respectively at opposite ends of said circuit, two control means located respectively at opposite ends of said stretch and eiective normally to connect said two sources and said two locking relays in series circuit over said two line wires with said sources poled in opposition, two directional relays located respectively at opposite ends of said circuit for controlling the signal at the adjacent end of said stretch, means controlled by the one of said control means iirst to be operated for disconnecting the source and locking relay at the adjacent circuit end from said two line wires and for connecting the directional relay at the said adjacent end in circuit with said line wires, and means controlled by each locking relay when picked up for preparing a stick circuit path including its own front contact and effective to maintain energization of said locking relay in the event that the control means at the adjacent end of the circuit is caused to be operated while said locking relay is picked up.

5. In combination with a stretch of railway track provided at opposite ends with signals for governing traino movements in opposite directions in said stretch, said stretch being divided into a plurality of track sections each provided with a track relay, a circuit comprising two line wires extending between the opposite ends of said stretch and including front contacts of each of said track relays, two sources of current located respectively at opposite ends of said circuit, two locking relays located respectively at opposite ends of said circuit, two directional relays located respectively at opposite ends of said circuit for controlling the signal at the adjacent end of said stretch, two control relays one associated with each end of said circuit, means for controlling each of said control relays independently of the other, circuit means effective when both of said control relays are picked up and including front contacts of such relays for connecting said two locking relays and said two sources in series circuit over said two line wires with said sources poled in opposition so that said two locking relays are normally released, circuit means controlled by either one of said control relays when such one relay is released while the other control relay is in its picked-up position and including a back contact of said one released control relay for connecting the directional relay at the associated circuit end to said line circuit in lieu of the source and locking relay at such circuit end whereby to energize both said directional relay and the locking relay at the opposite circuit end by energy supplied from the source at said opposite circuit end, circuit means controlled by each locking relay when picked up and including its own front contact for preparing a stick circuit for such locking relay, and circuit means controlled by said other control relay when such other relay is released while the said one control relay is released and including a back contact of said other control relay for completing said stick circuit for said locking relay whereby to hold energized said locking relay and said directional relay.

6. In combination with a stretch of railway track provided at opposite ends with signals for governing traiiic movements in opposite directions in said stretch, said stretch being divided into a plurality of track sections each provided with a track relay, a line circuit comprising two line wires extending between the opposite ends of said stretch and including front contacts of each of said track relays, two sources of current located respectively at opposite ends of said line circuit, two locking relays located respectively at opposite ends of said line circuit, two directional relays located respectively at opposite ends of said line circuit for controlling the signal at the adjacent end of said stretch, two approach track sections one at either end of said stretch, one 'of said approach track sections being arranged to be traversed by traffic operating over said stretch in one direction and the other of said approach track sections being arranged to be traversed by traiic operating over said stretch in the other direction, a track circuit including a track relay for each of said approach track sections, circuit means eiective when said two approach track sections and said stretch are Vacant and including front contracts of each of said approach track relays for connecting said two locking relays and said two sources in series circuit over-said two line wires with said sources poled in opposition so that said locking relays are normally released, circuit means effective when either one of said approach track sections becomes occupied while said stretch and the other approach track section are vacant and including a back contact of the track relay of the occupied approach track section for connecting the directional relay at that end of said line circuit to said line circuit in lieu of the locking relay and source at that circuit end whereby to energize both said directional relay and the locking relay at the other end of said line circuit by energy supplied rom the source at said other circuit end, means eiective when either of said lockingV relays pick up and including a front contact of such Contact of the track relay of said other approach track relay for completing said stick circuitV of said picked-up locking relay whereby te retain energized said locking relay and said directional relay.

'7. In combination With a stretch of railway track provided at opposite ends with signals for governing traffic movements in opposite directions in said stretch, said stretch divided into a plurality of successive adjoining trackl sections each provided with a track circuit including a track relay, two approach sections one for either end of said stretch and each provided with a track circuit including an approach relay, a circuit comprising two line Wires extending between the opposite ends of said stretch and including front contacts of each of said track relays, two sources of current located respectively at opposite ends of said stretch, two locking relays located respectively at opposite ends o f said stretch, means controlled by each approach relay for normally connectingI said two sources and said tWo locking relays in series circuit over said two line wires with said sources p oled in opposition, two directional relays located respectiyely atopposite ends of said stretch for controlling the signal at the adjacent end of said stretch, means controlled by the one of said approach relays rst to be. released for disconnecting the source and locking relay at the adjacent end oi the stretch from said two line Wires and for. connecting to 'such wires the directional relay at that end of said stretch, means controlled b y each locking relay when it is picked up for preparing a stick circuit which becomes completed When the other of said approach relays is released prior to the stretch becoming occupied, and means controlled by said track relays for energizing a particularone of said. lockingrelays when said stretch becomes occupied,4 said last- :mentioned means including an auxiliary relay, an auxiliary circuit for said one` locking relay completed when said auxiliary relay is picked up, and an energizing circuit for said auxiliary relay completed when the approach section at the end of the stretchl adjacent to the location of said one locking relay becomes occupied by a second train prior to aY rst train in that section entering said stretch.

GEORGE A. CULBEa'rsQN;

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