US2354023A - Traffic locking circuit - Google Patents

Description

July 18, 1944. c. D. IHRIG TRAFFIC LOCKING CIRQUIT Filed March 21, 1942 v w B 1115A 27 0mm '1':

Patented July 18, 1944 TRAFFIC LOCKING CIRCUIT Clifford D. Ihrig, Edgewood, Pa., assignor to The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania I Application March 21, 1942, Serial No. 435,745

Claims.

My invention relates to railway traflic controlling apparatus, and particularly to trafiic locking apparatus.

When trafiic is to be operated in either direction over a railway track extending between two spaced locations, trafiic locking apparatusmay be provided which includes a traffic locking circuit controlled jointly by two operators, one at each end of the stretch of railway track. Suchtraflic locking circuit is arranged to prevent the manipulation of trailic governing Signal levers or units for changing the direction of trafiic on the stretch of track between such two spaced locations while the stretch is occupied, or'while a signal is dis- .played for a train to proceed into such stretch.

It is an object of this invention to provide improved traffic locking apparatus which requires less equipment than the means heretofore known.

Another object of the invention is to provide improved traffic locking apparatus which is arranged so that the traffic locking relays function also as directional stick relays to thereby eliminate the need for separate directional'stick relays.

A further object of the'invention is to provide improved apparatus of the type described.

In practicing my invention I provide a polarized traific locking relay at eachend 'of the protected track stretch and provide means for energizing these relays in series with energy of one polarity or the other when the protected stretch is vacant. These relays govern the signals coritrollirigentrance of trains into the protected stretch,'while .the equipment is arranged so that the operator at either end of the protected stretch can cause the traffic locking relays to be energized with energyoi the polarity efiective to permit clearing of the signals governing entrance of trains'into thatend of the protected stretch 'only if the signals governing entrance of trains into the other end of the protected stretch are displaying their stop indications. Furthermore, th control of the trafiiclocking relaysis arranged so thatafter these relays have been energized to permit=clearing of the signals at one end of the protected stretch, :and-atrain thereafter enters thisstretch, the circuit for energizing the traflic locking relays in series is interrupted to prevent clearing of the signals at the other end of the protected stretch, while a stick circuit is established to energize the traffic locking relay'at the end of the stretch atwhich the trainentered so that this relay maintains the circuits or the associated signals and thus permits thesesign'als to be conditioned to authorize a secondior following train to enter the protected track stretch.

I shall describe one form of trafiic locking circuit embodying my invention, and shall then point out the novel features thereof in :claims.

. In the drawing the single .figure is a diagram of a stretch of railroad equipped with signaling apparatus embodying my invention.

Referring to the drawing, there is shown therein a stretch of track having track rails I and 2 over which traffic may move in either direction. Adjacent the left-hand or west end of the single track stretch is a passing siding or branch track 3P3 which is connected by switch. 3W with the single track stretch, and adjacent the right-hand or east 'end of the single track stretch is a passing siding :or branch track 5PS which is connected by a switch 5W with the single track stretch. The switches SW and SW and'th'e signals associated therewith may form parts .of interlocking installations at their respective locations.

Although the equipment is illustrated in connection with a single track stretch joining two passing sidings or branch tracks, the system is not limited to use in situations of this kind, and maybe employed Wherever trafiic may move in either direction between two points, but only in one direction at onetime.

The :track rails I and? are divided by insulated joints 3 into track sections for signaling purposes. As shown there is a section 3T which includes the switch SW, and a section 5T which includes the switch 5W, while the single track stretch between sections 3T'and 5T forms a track section 4T. Each track section is provided with track-circuit apparatus including a track battery connected across one end of the section rails and a track relay TR connected across the other end of the section rails. Thetrack relay 4TB, for section 41 is shown 'at the end of the section adjacent section 3T, while arepeater of this relay is located at the other end of the section and is designated dTPR.

Movement of trafiic along the main track from left to right through the switch 3W is governed by a signal 4SA, while movement of traffic from the branch track .3PS through the switch 3W is governed by :a signal 4S3. Similarly, movement of :trafiic from right to left along the main track through the switch 5W is governed by a signal .iSA, while movement of traffic from the branch track 5PS through the switch 5W is governed by a signal SSE.

The signals associated with the switches 3W andSW maybe of any appropriate type and are here shown as being of the searchlight type. The signals 345A and 58A eac'h have an upper portion capable of displaying a proceed or a stop indication, and a lower or call-on portion capable of displaying a proceed indication. The signals 4SB and SSB are each capable of displaying a stop indication and a proceed indication.

The signals 45A and GSB are governed by a signal control lever 3K, while the signals 58A and 58B are governed by a. signal control lever K. The levers 3K and 5K may form portions of interlocking machines, and each of these levers may also govern other signals, not shown, for control-. l to simplify the drawing, relay contacts are shown ling traiiic in the direction opposite to that con-j trolled by the signals which are shownreverse polarity.

In most cases the contacts of each relay are shown in the drawing directly beneath the winding of the relay, but in some instances, in order separated from the relay winding and where this is done the relay with which the contacts are Each lever 3K and 5K has. an intermediate position N in which it causes the associated si nals to display their stop indications, and is movfable from its intermediate position to a left-hand position L or a right-hand position- R. topermit the signals controlled thereby for one or theother direction of traffic to be conditioned to dis play proceed indications.

The signals GSA and 4SB have associated therewith a relay 4RGP' which is governed in accordance with the aspects displayed by these signals so as to be energized when and only when these signals display their stop indications, and to be deenergized if either of them displays a proceed indication. Similarly, a relay SRGP is controlled so as to be energized when and only when the signals SSA andSSB display stop indications and to be deenergized when either of these signals displays a proceed indication.

The relays IRGP and SRGP control approach locking stick relays ARASR and BLASR, while these relays control directional stick relays 3WSR. and SESR. The'meansfor controlling the approach locking stick relays 4RASR and 5LASR. is not a part of this invention and these relays may be controlled in any appropriate manner; as for example as shown in Letters Patent of the United States No. 2,093,170 granted to Ronald A. McCann on September 14,1937. r

The approach locking stick relays dRASR and SLASR may function in the manner well known in the art to control the associated switches to prevent movement of these switches except when it is safe for them to be .moved. The means'for controlling the switches, and for moving them between their two positions, is not a part of this invention and has been omitted in order to simplify the disclosure.

Each signal. control lever K has associated therewith a source of direct current which may be a battery designated D with an appropriate prefix. The negative terminals C of these batteries are connected together by a common line wire !0, while as hereinafter explained, energy'is at times supplied from one or the other of these batteries to a circuit including in series therewith polarized trailic locking relays WFR and The relays WFR and EFR are preferably of a type having both neutral and polar contacts and incorporating means to prevent picking up of the neutral contacts unless the relay polar contacts respond to a change in the polarity-of the'energy supplied to the relay. A relay which I may employ for this purpose is shown in Letters Patent of the United States No. 1,822,496, issued September 8, 1931 to Branko Lazich, while other relays which I may employ are shown in Letters Patent of the United States No. 2,250,214, issued July 22, 1941 to Harry E. Ashworth, in application Serial No. 402,609 by Andrew Hufnagel, and in application Serial-No. 424,151 byiArthur E,

associated is indicated by appropriate reference 'characters located directly above the contacts.

The equipment is shown in the condition which it assumes when the track stretch is vacant, the switches 3W and EW are in their normal positions, and the signal control levers 3K and 5K are in their intermediate positions.

- As the lever 3K is in its intermediate position, its contact 12 interrupts the circuits of the signals. 4SA; while its contact l4 interrupts the circuit of the signal 4SB, and its contact I 5 establishes a circuit for supplying energy to the approach locking stick relay 4RASR. This relay is energized'at this time by current supplied over its stick circuit which includes front contact l6 of relay 4RGP and front contact I8 of relay 4RASR.

As relay v IRASR, is energized, its contact 20 establishes a circuit including front contact 2| of relay 3'IR for energizing the directional stick relaysWSR, while contact 22 of this relay is picked. up to establish a stick circuit to maintain the. relay energized after release of contact 2| of trackrelay 3'I'R. In addition, contact 23 of the relay 3WSR is picked up to permit energy to be supplied from the battery 3D to the relays WFR andEFR.

At this time as switch 3W is assumed to be in its normal position, energy of normal polarity is supplied to the relay 3WPR by means, not shown, governed by the switch, and the neutral contact 24 of this relay is picked up, while its polar contact;25 occupies its left-hand or normal position.

As lever 5K is in its intermediate position, its contact 26 interrupts the circuits of the signals 58A, its contact 21 interrupts the circuit of the signal 5SB, and its contact 28 establishes the circuit including front contact 30 of relay SRGP, and front contact 3| of relay 5LASR for energizing the approach locking stick relay SLASR. As relay 5LASR is energized, its contact 32 is picked up and establishes a circuit including front contact 34 of relay 5TB for energizing the directional stick relay 5ESR, while contact 35 of relay 5ESR is picked up to maintain the relay energized after release of the contacts of relay 5TB. As relay SESR is energized, its contact 36 is picked up to permit energy to be supplied from batterySD to the relays EFR and WFR.

As the switch 5W is in its normal position, energy of normal polarity is supplied by means, notshown, to the relay SWPR so that its neutral contact 31 is'picked up and its polar contact 38 occupies its normal or left-hand position as shown.

.As directional stick relay 3WSR is energized, its contact 23 v is picked up and-establishes connection from the positive terminal B of battery 3D through front contact 40 of relay lTR'to one terminalof the winding of traflic locking relay WF'R. Similarly, as directional stick relay 5ESR is energized, its contact 36 is picked up and 'Eu'rtherr-nore, asymmetric tact 42 of relay 4TB and contact 43 of relay 3 4T-PR. are picked up, connection is established through wire '45 between the other terminalso'i the windings of the traflic locking relays WFR and EFR. It follows "that the relays WFR and are connected in series with the batteries 3D and 5D, butthat these batteries :are'included in the circuit in series opposition with the result that the neutral contacts of these relays are released while their polar contacts. remainfin their-lastoperated positions. 4 7

units 3M and 5M are included in series with the connections from the batteries 3D and 5D, respectively, and each "is poled to'permi't energy to be supplied 'f-romits associated battery, and so "to prevent supply of energy "from either batterytothe relays 'EFR and WFR if the voltage of one of the'batteri'es should substantially exceed "that of "the other battery.

As neutral contact 46 of relay 'W FR is released, it interrupts the circuits of signals ASA and 4813, and "as the neutral contact 41 "ofrelay 'EFR is released, it interrupts the circuitsof the signals SSA and 5813. Accordingly, as long as "the tra'flic locking relays wi 'RiandEFR aredeenergized, the signals :at'bot-h ends of the single track stretch and governing "entrance of trains into this stretch are prevented from dis-playing proceed indications.

If it is desired to condition'the apparatus 'to permit a train-moving from leftto right to enter the single trackrstretch the operator controlling stick circuit of approach locking stick relay 4RASR. The consequent release of contact 29 interrupts both the pick-up and stick circuits of directional stick "relay--3WSR so that contact 23 of this relay releases and interrupts the connection from the left-hand terminal of the winding o .relay WFRto terminal-B of the battery --3D and connects this terminal of the winding ofirelay WFR to the common wire ill.

Assuming that relay SESR remains, energized, the relays-EFR and WFR are now energized in series 'by-cur rent supplied from battery 5D over the circuit which is traced from terminal B o)? the battery 5D through asymmetric unit 5M, from contact 36 :of

.relay EESR, front contact M of .relay #IFPR, winding of relayEFR, front contact-43 of relay ATPR, wire 45, front contact 42 of-relay 4TB, winding of relay WFR, front contact 40 of relay 4TB, back contact 23 of relay SWSRand wire id to terminal C of battery 5D.

At this time, therefore, the relays WER'and EFR .are energizedin series bycurrentsupplied from. battery 5D, and the .neutral contacts of these relays are picked up while the polarity .of the energy supplied. to the relays is .such that their contacts are moved to their right-handor reverse positions.

Accordingly, polar contact '48 of .relay'lEER interrupts the circuit controlled by this relay .for supplying energy to signals 55A and'SSBand these signals are therefore .preventedfrom displaying proceed indications.

At this time polar contact 50 :of .relay WFR establishes the circuit for supplying energy to one or the other of the signals ISA or iSB, dependingon the position of the switch 3W. This "switch is shown in its normal position so that energy i supplied to signal ASA over a circuit which passes from terminal B through contacts 50 and 46 of relay WFR, contacts 24 and 25 of switch indication relay 3WPR), lever operated contact I 2, and contacts 4TB. and 3TB to the upper portion of signal ASA, so that this signalgives a proceed indication. When this signal ASA displays a proceed indication, relay ARGP i released and its contact l fi prevents energization of "the approach locking stick relay 4RASR. Ac-

cordingly, relay ARASR remains released and prevents movement of the switch 3W, while contact'2il of relay 4RASR interrupts the circuits of the westbound directional stick relay 3WSR so that contact 23 of this relay remains released and maintains the circuit for energizing th traffic relay 3TH will release and its contact 2! will interrupt thepick-up circuit of relay 3WSR sothat the latter relay will remain released and maintain the circuit for energizing relays WFR and EFR. 'In addition, when track relay 3TB releases, its contact I1 and 19 interrupt the circuit of the upper portion of signal RSA and the circuit of the signal 4S3 so that these signals displaystop indications.

"When the train advances into section 4T, track relay 4TB releases and its contacts 33 and 39 "additionally interrupt the circuits of the signals ASA and 8513, While its contact 48 additionally interrupts connection from terminal B of battery 3D to the left-hand terminal of the winding of relay WFR, and connects this terminal of the relay winding to common w i re Ill and thus to terminal C of battery 5D. "This 'ins'ures' that the left-hand termin'al'ofthe winding o'fthe tra'fiic locking relay will remain connectedto "terminal C ofbattery fiD asflon'g as section i' -l is occupied and prevents interruption of the circuit of relay WFR if the contacts of relay '3WSR should pick up 'afterthetrainvacates sectionF3T. In addition, on release of track relay I'll-tits contact 42 interrupts the circuit for energizing relays WFR and EFR in series "and establishes a stick circuit to energize "the relay WFR from the battery 3D. This stick circuit is traced 'from terminal B of battery 3D through reverse polar contact 52'and front neutralcontact 53 of relay WFR, back contact 42'o'f "relay 4TR,winding of relay W'FR, back contact 4? of relay 4TB, and common wire 50 to termina'lC o'f batterySD. The energy thus upplied to relay ilifFltirorn battery 31) is of the same polarity as thatpreviously supplied to the "relay from. battery 5D, and maintains the relay polar contacts in their reverse positions so that polar contact Bil-remains closed to permit energy tobe supplied to signal 48A or 48B, with the result that one "of these signals may display a proceed indication and thuspermit a second or following eastbound "train to enter the single track stretch. The energy suppliedto the signal 48A or 4813 may be supplied oveijthe circuits controlled bytra'ck'relays 3TR.and 4TB. or it may be supplied overicircuits established by a call-on relay 400R. The relay 4COR.may.jbe controlled in any .manner well known in the. art, audits circuit i .omitt'ejd from ,the drawing to simplify the disclosure.

As pointed out above, on release of the track relay- 4TH the circuit for'energizing the relays contact 54 additionally interrupts the stick circuit for th relay EFR.

On release of relay -4'I'R're1ay 4TPR also releases and its contact 4| interrupts connection between the right-hand terminal of the winding of relay BER and terminal B of battery D, while contact 43 of relay 4TPRinterrupts connection from wire 45 to the left-hand terminal of the winding of relay EFR. Accordingly, relay EFR cannot be energized from either battery 3D or 5D and the neutral contacts of the --relay are certain to remain released and'prevent the display of a proceed indication by either signal SSA or 55B.-

It will be seen, therefore, that after the equipment has been conditioned to permit an eastbound train to enter the ingle track stretch, and such a train does enter the stretch, a stick circuit is established to'maintain the relay WFR energized so that it maintains the circuit to permit energy to be supplied to the signal 48A or 4S3, while the circuit of the relay EFR is interrupted and cannot be established. This insures that the relay EFR, will remain released and will prevent the display of aproceed indication by either signal SSA-or 553. Accordingly, after an eastbound train enters the track stretch, a second or following train may also be allowed to enter the stretch, but the equipment cannot be conditioned to cause either signal BSA or 5SB to display a proceedindication and thus permit a westbound train to enter the single track stretch.

When the eastbound train enters section 5T, track relay 5TB. releases and its contact 34 interrupts the pick-up circuit of eastbound directional stick relay SESR, but this relay is maintained energized by current supplied over its stick circuit which includes front contact 32 of relay SLASR and its own front contact 35. Ac-

cordingly, contact 36 of relay 5ESR remains picked up to permit energy to be supplied from battery 5D to the relays EFR and WFR after picking up of relays 4TB and 4TPR.

Reverting to the time when the train vacates section 3T, the consequent picking up of track relay 3TB. and closure of its contact 2| permits energy to be supplied over the pick-up circuit for relay 3WSR. if a proach locking stick relay GRASR is picked up. The relay 4RASR. will be picked up if the lever 3K has been returned to its intermediate-position and the signals 48A and 48B display stop indications.

If relay 4RASR remains released, its contact 20 will interrupt the circuit of relay SWSR so that contact 23 of the latter relay remains released and interrupts the supply of energy from battery 3D to relays WFR and EFR. When the train subsequently vacates section 4T so that relay 4TB picks up, the left-hand terminal of the winding of relay WFR becomes connected to the common wire l0 through front contact 40 and back contact 23.

When the track relay 4TH. picks up, its contact 42 interrupts the stick circuit for relay WFR. Relay 4TPR also picks up, and the contacts 42 and 43 of relays 4TB. and 4'I'PR respectively establish the circuit traced hereinbefore for energizing the relays WFR and EFR in series from the battery 5D. The neutral contacts of these latter relays will be picked up and the polar contact 50 of relay WFR will establish at that point the circuit for energizing signal 43A or 453, and

ruptthe stick circuit for the relay. Under these conditions, therefore, the apparatus is conditioned 'to permit another eastbound train to enter the single track stretch.

If at the time the train vacates section 3T and track relay 3TB, picks up the approach locking stick relay 4RASR picks up, the pick-up circuit for the relay 3WSR will be complete and the contacts of this relay will'pick up. Contact 23 of the relay 3WSR will then interrupt the connection controlled thereby from common wire ill to the-left-hand terminal of the winding of relay WFR and will connect terminal B of battery 3D to this relay after picking up of relay 4TB. As long as relay 4TR remains released, the relay WFR is energized by current supplied over its stick circuit. When the track relay 4TR picks up, relay 4TPR also picks up and the relays WFR and EFR are connected in series between the positive terminals of the batteries 3D and'5D with the result that no energy is supplied from either of these batteries to the relays WFR and EFR and the neutral contacts of these relays are released while their polar contacts remain in the positions which they last occupied. As the neutral contacts of the relays WFR and EFR are released, the circuits of the signals 38A and 38B, and of signals .iSA and 5SB, are interrupted, so that all of these signals are at stop.

The equipment operates in a similar manner on movement of a westbound train through the track stretch. In order to clear the signal BSA or 5SB to permit a westbound train to enter the single track stretch the lever 5K is moved to its position L in which position contact 28 interrupts the circuit of the approach locking stick relay ELASR so that the contacts of this relay release and interrupt the circuit of the relay EESR. Contact 36 of the latter relay then interrupts the path from the battery 5D to the relays WFR and EFR, and

connects the right-hand terminal of the winding of relay EFR to common wire In so that the relays WFR and EFR are energized in series from the battery 3D. The polarity of this energy is such that the polar contacts of the relays WFR and EFR swing to their left-hand or normal positions, while the neutral contacts of these relays are picked up.

Accordingly, the contacts of relay EFR. establish a circuit to permit energy to be supplied to signal SSA or signal 5S3 so that a westbound train may be authorized to enter the single track stretch, while the contacts of relay EFR also are prepared to establish a stick circuit to energize this relay from the battery 5D after the train enters section 4T and causes release of relays 4TB. and 4TPR. As the polar contacts of relay WFR are in their left-hand or normal positions, the stick circuit for this relay is not established on release of relay 4TR, and the circuits for supplying energy to signals 48A and 48B are interrupted so that these signals display stop indications and cannot be caused to display proceed indications. V The subsequent operation of the equipment during movement of the westbound train through the track stretch will be readily understood from the ioregoing explanation oi the operation dure ing'inovement of an eastbound train, and need not be traced'furtherherein. From; the foregoing it will be seen; that the equipment; is arranged so; that the signals gov-1 erning entrance of trains into the singletrack; stretch at, either end can be cleared onlyii the signals at the other end are displaying theirstcp indicaticns. In order-to clear a signal governing entrance of trains into either end of the single track stretch the trafiic locking relay atthat end of the Stretch must fi st be e e i edwitn cur-,- rentycf; the pola y whi s su p e r inthe batteryatthe other end of the singletrach stretch, and; this can be done-only if the direc tional stick relay-at such other 1 end oi: the. st et h is p c ed rz;- :t direc io a st ck re ay, at eit r e d. vcf t e s et hican be i ked. up when and only when' the signals gQMerning entrance of trains into that end-of the singletracl; stretch are displaying their stop indications;

Furthermore, itwillbe seen that as soon as a t ain acoep sthe proceed ndi at n di pla ed: y the signal at either end of the single traclr;, ;the directional, stick relay. at that end of the-single ra k stret h is p e en ed r p ckin p s that the, polarity of the energy supplied to th trafiic locking relays cannot bechanged. This prevents clearing of the signals governing entrance of trains moving in the other direction into the single track stretch at the other end. In addi-, tion, when a train advances into thesingle track stretch, the circuit for energizing the traffic loci;- ing relays in series is interrupted so that the relay at the exit end of the stretch (with refen ence to such train) is certain to remain released and thus prevent. clearing oi the signal controlled thereby, buta stick circuit: is established tozmaintain the trafiic locking relay at the entrance end of the si le track tre ch Withicte erence to such train) energized with current of the same polarity as that previously supplied to the, relay so that this relay permits the signals, controll d ther bybe ndit one to ive r ceed ind t ons n s e m t to l wine rain to be directed into the single track stretch. V ,3 When the track, stretch becomes vacated, the stic circuit for t e t aff c oo n e a tt re end of the single track stretch at which thelast train entered the stretch is interrupted while the equipment is conditioned to permit the trafiig locking relays to be energized in series from the battery at either end so that trains moving in either direction may be directed through the track stretch.

Although I have herein shown and described only one form of tramc locking circuit 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 stretch of railway track extending between a first and a second location and over which traffic may move in either direction between said two locations, a first signal at the first location governing entrance of trains into said track stretch, a second signal at the second location governing entrance of trains into said track stretch, a first polarized relay at the first location, means efiective when and only when said first polarized relay is energized by current of normal polarity to permit said first signal to'provide aproceedrindication, a second polarized rel ay-at'the secondlo'cation, means efiiectivewhen and only whensaid second polarizedrelay is energized; by current-of reversepolarity-tb D mit said second signal to provide a proceed indication, a line circuit over whichv said polarized relays maybe energized in series, means includinga contact closed.- only when said first signal is tobe cleared far energizing said polar relays in series, with current of n orm al polarity supplied ov 'ersaid line circuit provided said track stre cn' s ac n n so ds cc d i n i playing its stop indication to thereby'permit the first slgqnalto provide a proceed indication and preventthe display of a proceed indication by the se ond: s snet, m an u n a t c .c c on when said; second signalis to be cleared for ene izin snio po ar: r a s in e wi h c rent o c c e o o i v sup ed o aid line circuit provided saidtrack stretch is vacant and said first signal is displaying its stop indication to. th r y p mit t e s on al to r i ro ed. in cation andnre nt he'dis iay o atprece d ind cat o by he rs s en lwa ni e s eflec iv e str in, enter said tr c st etcn o terr aid li -c rcu t and to establish a s ck circuit to. up l tcthepcle ized ay asso iated. h, he i n permi te to displa a n ci e d' nd at n enc eyo he samenesritv that was supp ied to aid relay ove i l ne: c rcuit to, there y cause sa dre ay o mai ain the e tabli h d. dire t n o rel i un sa track stretch is vacated. f

1 2,- roombi a on, a st e c of rai way tra eirtcndine betw enzaifi s and a econd l a i n and over ,vvhichtraffic may m OV 8 in either direct on QQE BQH'SQJQw-EWQ lo ations, a first si na attne first-l a on overnin entr ce of trains into s id; ack str t h, a. se ond si a at the. second; location governing entrance of trains into said-trash stretch, a firstpclarizedrelay at said first location, means; effective when and only wh sa rst: po ar zed: ay s e i ed y current ofnormal polarity to permit said ,first signal to provide a proceed indication, a second polarized rel y: .atsaid; secondlocatien, means efiective. when and only, when said second polarized relayis'energ-ized by current of reverse pol rit to; permit sa d, second s n to p ovide a proceed indication, a first source of direct cur-. ent at. thefirst; location, a second source of directcurrent at, the second location, a'line circuit extending between said first and second locations, means including a contact closed only when said first signal is to be cleared for energizing said polar relays in series over said line circuit by energy of normal polarity from said second source provided said second signal is displaying its stop indication to thereby maintain the display of the stop indication by said second signal and permit the display of a proceed indication by said first signal, means including a contact closed only when said second signal is to be cleared for energizing said polar relays in series over said line circuit by energy of reverse polarity from a said first source provided said first signal is displaying its stop indication to thereby maintain the display of the stop indication by said first signal and permit the display of a proceed indication by said second signal, and means effective When a train enters the track stretch to interrupt said line circuit and to establish a circuit to supply energy from said first source to said first polarized relay provided the contacts of said first polarized relay are in their normal positions and to establish a circuit to supply energy of reverse polarity from said second source to said second polarized relay provided the contacts of said second polarized relay are in their reverse positions. H

3. In combination, a stretch of railway track extending between a first and a second location and over which trafiic may mov in either direction between said two locations, a first signal at tha first location governing entrance of trains into said track stretch, a second signal at the second location governing entrance of trains into saidtrack stretch, a first polarized relay controlling said first signal, a second polarized relay controlling said second signal, means for connecting one terminal of the winding of the first polarized relay to one terminal of the winding of the second polarized relay, a first source of direct current at the first location, a second source of direct current at the second location, each of said sources of current having a first and a second terminal, the first terminal of each of said sources being of the same relative polarity, manually controlled means at the first location for at times connecting the other terminal of the winding of the first relay to the first terminal of the first source and at other times to the second terminal of the second source, and manually controlled means at the second location for at times connecting the other terminal of the winding of the second relay to the first terminal of the second source and at other times to the second terminal of the first source.

4. In combination, a stretch of railway track extending between a first and a second location and over which trafiic may move in either di-' rection between said two locations, a first signal at the first location governing entrance of trains into said track stretch, a'second signal at the second location governing entrance of trains into said track stretch, a first polarized relay controlling said first signal, a second polarized relay controlling said second signal, means for connecting one terminal of the winding of the first polarized relay to one terminal of the winding of the second polarized relay, a first source of direct current at the first location, a second source of direct current at the second location,-each of said sources of current having a first and a second terminal, the first terminal of each of said sources being of the same relative polarity, manually controlled means at the first location for at times connecting the other terminal of said first relay to the first terminal of the first source and at other times to the second terminal of the first and second sources, manually controlled means at the second location for at times connecting the other terminal of the second relay to the first terminal of the second source and at other times to 'the second terminal of the first and second sources, means including 'a contact ot'said first relay by which connection may be established from the first terminal of said first source to said one terminal of said first relay when said track stretch is occupied, and means including a contact of said second relay by which connection may be established from the first terminal of said second source to said one terminal of said second relay when said track stretch is occupied.

5. In combination, a stretch of railway track extending between a first and a second location and over which traific may move in either direction between said two locations, a first signal at the first location governing entrance of trains into said track stretch, a second signal at the second location governing entrance of trains into said track stretch, a first polarized relay controlling said first signal, a second polarized relay controlling said second signal, means for connecting one terminal of the winding of the first polarized relay to one terminal of the winding of the second polarized relay, a first source of direct current at the first location, a second source of direct current at the second location, each of said sources of current having a first and a secondterminal, the first terminal of each of said sources being of the same relative polarity, manually controlled means at the first location for at times connecting the other terminal of said first relay to the first terminal of said first source in series with a firstasyrnmetric unit and at other times to the second terminal of the second source, and manually controlled means at the second location for at times connecting the other terminal of said second relay to the first terminal of said second source in series with a second asymmetric unit and at other times to the second terminal of the first source, each of said asymmetric units being arranged to permit energy to be supplied from the associated source of current to said relays and to prevent the supply of energy from the other source of current to said relays over a circuit including said unit in series therewith.

' CLIFFORD D. IHRIG.

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