US2341343A - Railway signaling system - Google Patents

Description

Feb. 8, 1944. T. w. TIZZARD, JR

RAILWAY SIGNALING SYSTEM Filed Aug. 7, 1941 5 Sheets-Sheet l MU Q 33 a 5G HIS A'II'TORNEY Feb. 8, 1944. r. w. TIZZAIIRD, JR

RAILWAY SIGNALING SYSTEM Filed Aug. 7, 1941 5 Sheets-Sheet 2 H16 A'IITORNEY Feb. 8, 1944. T, w. TIZZARD, JR

RAILWAY SIGNALING SYSTEM Filed Aug. '7, 1941 5 Sheets-Sheet 3 Eh. -L ril fll @66 em T rub INYENTQR T720772 W Tzz'zami H15 Ar'roRN EY 9 T. w. TIZZARD, JR

RAILWAY SIGNALING SYSTEM 5 sheets-sheet 4 Filed Aug.. 7, 1941' INVENTQR 120m Wfizzard BY HIS AT I 'ORNEY Feb. 8, 1944. T. w. TIZZARD.'JR

RAILWAY SIGNALING SYSTEM 5 Sheets-Sheet 5 Filed Aug. 7, 1941 mwwom HIS ATTORNEY Patented Feb. 8, 1944 signer to Ihe Union. Switch" and Signer-1Company, Swissvale, Pa., a corporation of Pennsyh Vania.

Application August 7', 1941, Serial No. 405,821

16 Claims My invention relates to. a railway signaling system and particularly to an improved, system which employs apparatus; of the type shown in application Serial No. 393,363 of George W. Baughman.

It is an object of my invention to provide an improved signaling system of the type described and arranged to facilitate control of the signalingsystem by remote control apparatus.

A further object of the invention is to provide an improved system of the typedescribed and incorporating means for approach locking the switches atthe entrance ends of the passing sidings without necessitating the use of additional linewires.

A further object of the invention is to provide an improved signaling systemwhich is arranged so; that when the remote control apparatus has. been manipulatedto condition thesi'gnalsfor one direction of trafiic in a track stretch between passings-idi-ngsto display proceed indications, the signals for the other direction of traffic cannot be, conditioned to provide proceed indications;

Gther objects of the invention and features of novelty will be apparent from the following description taken inconnection with the accompanying drawings;

I shall describe twoforms of signaling; system embodying my invention, and shall then pointoutthe novel featuresthereof in claims;

In. the drawings,

Figs. Ia, 1b and 1c; when placed together in the order named form a diagram showing a stretch of railway track equipped with one form of? signaling system: provided by my invention, and

Figs. 2m and 2b; when placed together in the order named. form a diagram showing a stretch Off railway track equipped with a modified form of signaling: system provided by my invention.

Similar reference characters referto similar parts in both views.

Referring to the: drawings, there is shown therein. a stretch of railway track over which trailic moves in: both directions. In addition, there are passing sidings M and- N which are connected with the main track by means of switches MW andNW in the customary manner.

For purposes'ofiillhstration itwill' be assumed that: the; rightehand: end of the track stretch is east; and? that the. lett-hand end. thereof is west,

Accordingly; train movements from leftv to rightarezeastbonnd; while train movementsfrom right to. left: are westbound.

The rails of. themain, track are divided by intem provided by thi invention is directed particularly to means for controlling the signals 25- and 4S, and the signals 3S and ES. The signals IS and 6S at the entrance ends of the passing sidings may be controlled in any appropriatemanner well known in the art in accordance with trafiic conditions in advance and the position of the associated switch. It is also contemplated that the signals IS and ES will be controlled by remote control apparatus so that these signals will normally display stop indications, but may be controlled by an operator by means not shown to be governed by traffic conditions in advance.

In addition to the signals for the main track a signal ZSA is provided to control movement of eastboundtrains from the siding M onto the main track, while a signal SSA is provided to control movement ofwestbound trains from the siding N onto the main track. These signals may be controlled in any appropriate manner well known inthe art.

In the system shown in the drawings the signals are shown as being of the color light type, but it should be understood that the invention is not limited tothe use of signals of this type and that;

any desired form of signal may be employed instead.

The signal system provided by this invention is arranged to be controlled by remote control apparatus such as a centralized traffic control system. The remote control system includes a relay 5LHS associated with-signal 5S; and a relay ZRHS associated with signal 28.

The relays ELHS and 2RHS are normally released and when released condition the associated signal to display its stop indication as hereinafter explained in detail. The relays ELI-IS and ZPJHS when picked up permit the associated signalsto be controlled in accordance with traffic conditions in advance.

The relays 5 LHS and ZRHS may be controlled from a remote point in any desired manner, as

by direct wire or by a centralized traffic control system. The details of the-meansfor controlling these relays are not a part of this invention and have been omitted to simplify the disclosure.

The signals 2S and BSA, and 5S and SSA have associated therewith lock relays 2RMR and 5LMR, which are governed in accordance with the aspects displayed by the signals and by traffic conditions in the track stretch leading to the signals. Each of these relays is controlled in such manner as to be picked up when and only when both of the signals with which it is associated display stop indications, and to be released when either signal displays a proceed indication. Each of these relays is also controlled by time delay means so that when the relay is released and a train is in the vicinity of the switch, it cannot be picked up until the expiration of a time delay period unless the time delay period is eliminated by passage of a train.

In addition, each of the lock relays is controlled by traffic conditions in the detector section which includes the switch governed by the lock relay. When this section is occupied, the detector looking is effective to prevent movement of the switch, while a circuit is established to pick up the lock relay without waiting for the expiration of the time delay period.

The means for controlling the relays ZRMR, and ELMR is not a part of this invention and these relays may be controlled inany manner well known in the art. These relays, for example, may be controlled in the manner that relays RMR and LMR of Patent No. 2,093,170 to Ronald A. McCann are controlled.

Similarly, the signal IS has associated therewith a relay lSP which is picked up only when theupper portion of the signal displays its green or clear indication. Likewise the signal 68 has associated therewith a relay ESP which is picked up only when the upper portion of the signal displays its green or clear indication.

The system provided by this invention has a line circuit I formed by line wires 20 and 2| and extending between signals 28 and 3S, and a line circuit II formed by line wires 22 and 23 and extending between signals 48 and 53.

At each end of each line circuit are located line relays designated P and K together with a prefix corresponding to that of the signal with which the relays are associated.

Each of the relays P is of the stick polar type having contacts which are moved to one position when the relay winding is supplied with energy of one polarity and to another position when the relay winding is supplied with energy of the other polarity. These relays are also arranged so that their contacts when moved to either position remain in that position on deenergization of the relay winding.

Each of the relays K is of the biased polar type having contacts which are released when the relay winding is deenergized and become picked up only when energy flows in one direction through the relay winding.

The relays P control connection from the line circuits to the relays K in such manner that if the relays P respond properly to a change in the polarity of the energy supplied over the line circuits,; the direction of flow of energy through the windings of the relays K will be such as to be effective to pick up the contacts of the relays K.

The arrangement of the relays P and K is not a part of this invention but is shown and claimed in application Serial No. 311,955 of Harry E. Ashworth.

Each of the signal locations is provided with a source of direct current, such as a storage battery, not shown, the terminals of which are designated B and C.

The system provided by this invention employs continuously operating code transmitters T, izocr, and |3EICT, having contacts which are opened and closed at rates such as to provide '75, 120, and energy impulses a minute which are separated by periods of equal duration during which no energy is supplied.

In the drawings the relay contacts are in most instances shown directly under the winding of the relay. However, in some instances, in order to simplify the drawings, the relay contacts are shown removed from the relay winding, and where this is done the relay with which the contacts are associated is designated by appropriate reference characters placed above the contacts.

The equipment is shown in the condition it assumes when the track stretch is vacant, the switches MW and NW are in their normal positions, the upper and lower portions of signals- IS and 68 are conditioned to provide stop indications, and the remote control relays ZRHS and ELHS are deenergized. I

As relay ZRHS is not energized, its contac 25 is released and interrupts the circuit of relay ZHP so that its contact 26 is released and establishes the circuit of the red or stop lamp R of signal 23. As signals 28 and ZSA are both displaying. stop indications, the relay ZRMR is energized and its contacts 36 and 40 are picked up to permit energy to be supplied to the west end of line circuit I, while its contact 39 interrupts the circuit for supplying energy from the decoding transformer EDT to the relay 2J.

As signal IS is assumed to be conditioned by the remote control apparatus, not shown, to display its red or stop indication, relay ISP is released and its contacts 30 and 3| establish connections from a source of current to the wires of line circuit I so that energy of reverse polarity is supplied to this circuit. During the pickedup periods of the contacts of code transmitter IZUCT terminal B is connected through resistance 32, front contact 33 of track relay ITR. back contact 3| of relay ISP, front contact'35 of code transmitter IZOCT, front contact 35 of relay 2RMR, and front contact 31 of track relay 2TB. to line wire 2|, while terminal C is connected through back contact 33 of relay. ISP,

front contact 38 of code transmitter |20CT,' front contact .40 of relay ZRMR, and front contact 4| of track relay 2TB to line wire 20. During the released periods of the contacts of code transmitter IZUCT the supply of energy to the west end of line circuit I is interrupted, while the line wires are connected over front contacts of relays 2'I'R'and 2RMR, and the back contacts of and the code transmitter to the line relays 2]? 2K.

The energy supplied to the west end of line circuit I is supplied to line relays 3P and 3K dur-.

front contact 46 of track relay 3TH, front contact 4! of track relay 4TB, and back contact 48 of coding relay WCR to the other terminal "of the windings of relays3P and 3K.

The? contacts of, coding. relay I i/CIR are oper ated at '75 or 180 cod'e: frequencyaccording as:

relay 4His:r.e1eased: or picked. up.=. At this time relay; GE: is: picked: up: and its contact 50 establishes: a: circuit controlled. by a contact of code transmitter I-BEECT. for; energizing; relay! WCR; so

the contacts of. this relay: pick up: andrelease 180i times a minute;

The? rate: of' operation of thecontacts of relay W-CR whether theyare; operating at 180- or; '75.

code: frequency; is substantiallydifi'erent. from the: rateofoperation of. the contacts of code transmitter I'ZiJCJT. Accordingly the: contacts of relay; WCR and: of code transmitter 1211GT do not operate: in synchronisrm. and: there are frequently. recurring; periods: during which the com tacts: off code1 transmitters IZEJC'I are; picked up and the contacts of relay WCR are: released; At these timesienergy is; supplied: over the: line circuit IIItmreIaystI-E! and 3K. As1this energyisof' reverse: polarity the contacts of? relaytP occupy theirrightrlia'nrl" or. reverse: positions as shown,

while: the: contacts of relay 3K respond to the impulses-"of. energy supplied to the relay Winding: scr that energy is: supplied: through; thedecoding.

transformer SDT? to relay 3H as explained: in United States Patent No.. 22372788 to H. Nicholson and: E- R. Allison; Accordingly. the contactsof relay. 3H are picked: up: and its con tact 5 cooperates: with reverse polar contact 52 of relay 3P to establish the circuit of the ye'lloworcaution l'amp Y of signal 38.

During the picked-up periods of? the contacts of coding relay WCR' connection fromtiieline circuit to-relays 3F and 3K is interrupted; while energy is supplied to the east end of the line circuit. At this time relay 4H is picked up, as explained below, so the energy supplied to the line circuit is of normal polarity; During the picked-up periods of the contacts of relay WSR.

contacts of'coding relay WCR' are picked up and the contacts of code transmitter l-Zll'C'I" are re leased energy is supplied over line circuit I to line relays ZP-andi 2-K. As this energyis ofnorma'l' polarity the contacts of relay 2P occupy their-normal position as shown, while rela-y 2K responds to the impulses of energy supplied thereto and energy is supplied through the decoding transformer ZDT to relay 2H so that contact 53 of this relay is picked up. However, at this time contact of' relay ZRHS is released so the circuit of relay ZiI-IP is interrupted; and this relay is released and its contact 25' establishes the circuit of the red lamp R of signal 25';

The relay 2H cooperates with other means, not shown, to control locking of the switch MW. This means is arranged so that the switch is lockedwhenthe relay 21-1 is deenergized and may be moved. whens tlie relay 2H is picked up. As the relay 2H is picked up at this time the'switch MW maybe moved if desired.

The equipment associated with line circuit II- operates in similar manner at this time. As

signal. [is is'assumed .tozbe conditioned to..-display a; stopiindication: relay= 6SP-is released and? the energy-- supplied; to the liner circuit 11 during-the.- pick-edeupi periods of the contacts of the code 1 transmitter I-ZBG'I isofreverse polarity.

Similarly, as; relay 3'H- ispickedup its contacts Gil-and: 6 if establish.- connections such that energy of; normal polarity is supplied to the line circuit II: during the picked-up periods of contacts 63 and 6-41 of coding. relay ECR. As relay 3151 is.

picked up its contact tt establishes a circuit to supply-energy. ofz= code frequency to relay ECR so-the contactsof-relayECR operate at the-180 code'rate. During the released periods of the. contacts of the coding relay ECR the line circuit II. is connected to line relays 4P'and 4K. As the energy supplied'at. the east end of the line circuit. is. of reverse polarity the contacts. of; relay ll." occupy their; reverse positions and, acircuit. includingf-rontcontact; 66 of relay 6H,. andjreverse polar contact 61 of relay lP-is established tolight the yellowor, caution lamp Y of signal 48.

During;thereleasedperiods of the-contacts 10* and W oaths-codetransmitter IZBCT at signal;

. iiSLthewires. of. linecircuit II are connected to line relays 5P and 5K so that energy of normal polarity supplied ,to -the-westend of line; circuit II may 'feed*. to these; relays and relay 5K responds. to theimpulses ofv energy supplied theretoso that energy is supplied! through the decoding trans.-

former EDT to therelay 5H; Accordingly, the contacts of relay EI-Iiare. picked up and contact 12 cooperates with normal polar contact 13 of relay 5P-to establish the-circuit of relay 5HP. However; this circuit is-not complete at this-time; as

the remotely controlled; relay ELI-IS. is released and: its contact 'it-interruptsthe circuit of relay 5H3 Accordingly, contact 590i relay EiiI-IP isrreleasedand establishes the circuit of the red or stop lampR* of signal 58.

At thisit-imez as-s-igna-lsfiS and 55A are displaying: stop indications. relay; ELMR- is picked up and itscontacts 81'v and 52* establish the circuits to. permit. energy to be supplied. to the east end. ofi'the linecircui-t II,.while its contact 84- interrupts the" circuit; for supplying energy from the decoding transformer 513T. to relay 53 so relay 5J- is deenergizedz Operation 0 equipment on. cyissoigvcv of an eastbound. train. through. the. track stretch it is desired to condition the track stretch for passage of an eastbound train the operator manipulates the remote control apparatus to energize-relay iiRI-IS and its contact 25 piclss up" andcompletes the circuit of relay ZI-IP while contact 280i relay 2H? picks up and interrupts th'c'circuit of'the red or stop lamp R- of signal 2S and establishes the circuit of the yellow or caution lia-mplf'of this signal. As a result of this-change in the aspect of signal 28 relay ZRMR becomes released and its contacts 3t and E9 prevent'thefurther suppl'y'of energy to the West end of the line circuit I and connect the line circuit directlytothe linerelays EP- and 21; so that these relays are energized Whenever the contacts of coding-relay WCR are picked up. In addition, on release of relay ZRM-R its contact 39 establishes the circuit to supply energy from the decoding transformer 2171 to relay 2.3.

At this time, as pointed out above, coding relay WCR; is operating at the 180 code rate so 1 energy of this code frequency is supplied to the line circuit, while as the line circuit is directly connected to the line relays energy of this frequency is supplied to the line relay 2K. The relay 2K, therefore, follows 180 code and energy is supplied through the decoding transformer 2DT to maintain relay 2H picked up, while energy is supplied from the decoding transformer through the resonant rectifier unit RU to relay 2J. The unit RU is arranged to permit sufficient energy to be supplied through the unit to pick up the relay 2J only when the relay 2K is responding to energy of 180 code frequency. As energy of this frequency is supplied to the relay 2K at this time the relay 2J is picked up and its contact 85 interrupts the circuit of the yellow lamp and establishes the circuit of the green or clear lamp G of signal 28.

As a result of the cutting ofi of the supply of energy to the west end of line circuit I, which occurs on release of relay ZRMR, relay 3K ceases to follow code and relay 3H releases and its con tact 5| establishes the circuit of the red or stop lamp R of signal 38.

In addition, on release of relay 3H its contact 69 changes the energy supplied to coding relay ECR from 180 to 75 cod frequency, while its contacts 60 and BI change the energy supplied to the west end of line circuit II from normal to reverse polarity. On this change in the polarity of the energy supplied to line circuit II and to line relay 5P the contacts of relay 5P shift to their right-hand or reverse positions and contact 13 interrupts the circuit of relay 5HP to maintain this relay released and thereby prevent the display of a proceed indication by signal 5S if the operator should manipulate the remote control apparatus so as to energize relay 5LI-IS.

In addition, in order to condition the track stretch to permit passage of an eastbound train the operator manipulates the remote control apparatus, not shown, to cause signal (is to be governed b traffic conditions in advance. As the stretch is assumed to be vacant and as the switch NW is assumed to be in its normal position the upper portion of signal 68 will now display its green or clear indication, while relay BSP will be energized and its contacts 81 and 88 will pick up and will change the energy supplied to the east end of line circuit II from reverse to normal polarity. On this change in the polarity of the energy supplied over the line circuit II to line relay 4P the contacts of this relay shift to their normal or left-hand positions and contact 61 interrupts the circut of the yellow lamp Y and establishes the circuit of the green or clear lamp G of signal AS.

It will be seen, therefore, that as a result of manipulation of the remote control apparatus to condition the track stretch for eastbound traffic signal 28 i conditioned to display a green or clear indication, while the supply of energy to the west end of line circuit I is cut off to thereby put signal 3S at stop and to change the polarity of the energy supplied to the west end of line circuit II so that signal 53 will be held at stop. In addition, on clearing of signal (is the polarity of the energy supplied to the east end of line circuit II is changed so that signal 48 displays its green or clear indication. All of the eastbound main track signals, therefore, show green or clear indications, while all of the westbound main track signals show stop.

When an eastbound train enters section 1T track relay ITR releases and its contact 33 prevents the supply of energy to the west end of line circuit I, while its contact 34 interrupts the circuit of relay ZHP so that contact 26 of relay ZHP releases and establishes the circuit of the red or stop lamp R of signal 28.

In addition, when the train enters section IT and track relay ITR releases the detector looking for switch MW becomes effective to prevent I picking up of the relay 2RMR and thereby pre-' vent movement of the switch MW.

On release of track relay ITR the remote control relay ZRHS may be released or not depending on the method of operation of the remote control apparatus. For purposes of illus--' tration it will be assumed that this remote con-" trol system is arranged and operated in such manner that the relay 2RHS remains picked up when track relay ITR releases, and that the relay ZRI-IS when picked up remains picked up un- I release. On release of relay 2H its contact 58 interrupts the circuit of relay ZI-IP.

In addition, on release of track relay 2TB its contact 4] establishes a circuit short circuiting the portion of the line circuit I west of the track relay, while its contact 3'! establishes a circuit short circuiting the portion of the line circuit east of the track relay. As both portions of the line circuit are short circuited there is no pos-- sibility that the line relays will be improperly energized if energy is improperly supplied to either portion of the line circuit.

When the train advances into section 3T track relay 3TR releases and. its contacts 42 and 46 release and additionally interrupt and short circuit lin circuit I, while contacts and 9| of relay 31R interrupt the supply of energy to the west end of line circuit II, and connect this line circuit directly to the line relays 4P and 4K and thereby render operation of these relays more interrupts the circuit of relay EI-IP to insure that this relay will remain released and maintain the circuit of the red or stop lamp R of signal 58.

In addition, release of relay 5H may render the locking for switch NW effective so that this switch cannot be moved without waiting for releas of the time locking means. may also control indication means, not shown, so that on release of the relay the indication means will operate to provide an indication of the approach of the train.

When the train advances into section 4T track relay lTR releases and its contacts 93 and 94 ply of energy to the east end of line circuit Iand The relay 5H up .of relay ZRMR. up of itra'ckxrelay .lT-R a pick-up (circuitis estab- .-lished.or;relay 2RMR.=as.explained in Patent.No. 1.2;093 ,L'll); torBonald ..'McCann -.mentioned above.

"Accordingly, ithe'relay lZRMR .apicks up land :es-

tablishestastickrcircuit to maintain itself picked counterpart relays -at the other signal locations, is'of a typewhich -is slow in releasing so that it will bridge the intervals between the supply of impulses of energy thereto. Accordingly, I on release of the contacts of the track relay 4TH, the contacts of relay 4H remain "picked. up forsa period? and maintain the pick-up circuit :of :relay l-SR long enough for :the contacts of this'relay -to pickup.

When the contacts .of relay AH releaseits contact "96 completes z-a stick circuit "for .relay llSR, while its :contact 168 interrupts the circuit :of the green lamp and-establishes the circuit of .the red onstopllamp of'signalAS.

WhenzrelayllSR picks up its contact Jll'lcuts .o'ff the supply oflenergytothe .west end. of line circuit-II.

"When the :traima-dvances into 'section 5T track relay5TR releases vand its contacts 1133.3nd. addition ally interrupt and short circuit .line circult II.

When the rear .of :the :train vacates section T track relay, lTRzpicks up so that energy mayibe supplied-to: the sweet endlof .line circuit I"on:pick- .In addition, on picking up sas long ;as:-signal.2S displays a stop-indicatiomwhile contacts .49 and .36 of.re1ay12RMR establish connection from the contacts of :the :code transmitter VIZfiCT to the line circuit .1 :so that energy issuppliedto the .westend of line. circuit .I;aiter :picking up (of the contacts of track .relay 253B. This-energy is of. reverse polarity :as signal 1:5 ?is :displaying its .red lorrstop indication and relay l SP is released.

When'the rear ofthetrain va'cates section 2T ltrackrelay 2TB. picks up,'while when theitrain vacates section :3T :track relay 3TB. picks :up and energy :supplied'vto-the west end of line circuit I feeds to .-line relays 13F and 3K :over the circuit Which-,includesback contacts :43 and 411 of'track relay 5TB. On-the supply of energy ofreverse polarity to relay 3P its contacts :remain in their reverse position, .while :on ithe supply of coded energy to therelay 3Kienergy issupplied through transformer EDT to relay ..3H. Accordingly, the :contacts of .relay :.3H :pick up vand. contact :5 l co- ,operateswithreversepolar contact 52 of relayi3P 'to'zestab-lish thecircuit of the yellow or caution lamp of signal 3S.

-.Qn picking up :of the contacts 69 and 161 of relay 13H andpfcontactsllfland 9! of relay 3TB connections are established to permit energyof normal polarity .to be supplied to line circuit/II after the contacts of track relay 4TB pickup. Ascontact .69 of re1ay'3I-Iis picked up the coding relayiECR operates at the 1'80code frequency;

When the trainadvances-far enough to vacate section QT, track relay ATE/picks up and its con-' 'tacts :filtand ll :connect the line wires Zll and 2| of "line circuit '1 to the contacts 5 and 58 of coding relay WCR so that during ther eleased periods of these conta'cts-energ-ymaybe supplied over the line circuit' to the line relays eP and-iiK,

while during thepicked-ruplperiods of thesel-contacts energy :may be supplied a to Jthe east end 1 of linecircuitlI.

At this time relay 4H .is released :while .relay 5 .ASR, is maintained picked ;up.by;energy supplied .over the cstick circuit which inclues back'contact 49.61 of relay AH. Accordingly, icluringwthe pickedup periods of the contacts of the coding relay WCR terminal B of the .source is :connected 10 throughbackcontactfill .of: relay ;3SR,,front contact 103 of :relay :ASR, ;and back contact 55 of relay 14H to line wire: 25], while iterminal C ;is connected through front contact 11194 of relay 45R, .and back contact -51 of relay 4Htoline .wire Energy of normal polarity is .thereforetsupplied to the .eastiend of line circuit I and thisqenergy is supplied to line relays 32F a -K during the released periods of the contacts of code transmitter IZGCT. .Qontact15B of :relay'ZH thereupon ,picks;up, a-ndvassuming thatcontactjZS of relay .;2RI-IS remains picked up as explained 'above, completes the circuit of'relay ZHP. Accordingly, contact 52,6 0f relay-HIP picks up and, interrupts thezacircuitlof the red-or stop lamp "R ,of (signal 2s ;and establishes :the =Cl1Cllit of the yellow or caution lamp Y of this signal. ,On this change in the indication displayed by :signal 28 relay .2RMR becomes released to prevent ymovement -01? the :switch :MW,-while contacts 36 and of 3ogrelay ZRMR cut oil thesupply ,of ene g to the west end of line circuits Land eonnectthe wires of line ,circuit .1 directly :to the line relaysgZP and 2K 50 that relay 2K will operate at the frequency determinedrbyuthe :rate of operation of coding relay WCR. ,Inadditiongonrelease of relay -2RMR its contact 39-establishes the circuit .for supplying energy from the transformer ZDT to relay. 2J.

Atthis time :as relay 41-1 is released its-contact 5E] establishes the circuit. controlled by code (transmitter 750T jfor supplying energy to the coding relay WCR so that this relay supplies energy of 75 code frequency to line :oircuit I1 and relay 2Kope1ates at this frequency. As a'result too little :energyis suppliedthrough the resonant :unit EU :to pick up :the contacts oforelay N: and contact .55 :remains :released and maintains the circuit of the yellow or caution lamp Y vof signaIiZS.

From the foregoing fit ;.will be v.Seen that when an eastbound train passes through the track zstretch. signal 2S:continues to, display; a, stopflndilcationuntil the trainyacatessection3T. When the train :advances this .far, assuming that .the .remote control relay oZRHS cremains energized, signal 28 is conditioned rto display itsyellow or caution indication,;while relay FZRMR: is released to prevent movement of'the switch"MW,-and to cut off the supply of energy to the west end of line-circuit I'sothatsignal 3S-displays its redor stop indication.

Continuing with consideration of the-operation of the equipment in response 'to passage of the eastbound train, and assuming that a second .trainlhas not entered ,thetrack stretch an'd'that relay TZRI-IS remains picked up, when the train advances into section 16T track relay LBTR/r'eleases-;.and,its contact H15 routs ofi" itheisllpplyrof energy to the east /end'of line circuit :I I. 1

;'In;-a'ddition, when the train venters section :51 signal :66 is conditioned b y means, not shown, its adisplayits ,red; or stop indicati n; while ;.cn :this vchange in :the aspect :of signal :6S :relayreleases,

the 180 rate.

When the train advances farenough to vacate section 5T track relay 5TB picks up, but at this time relay 43R. is maintained picked up by its stick circuit and its contact l! continues to interrupt the supply of energy to the west end of line circuit II so that on picking up of track relay TB. energy is not supplied to the line relays 5P and 5K.

When the train advances far enough to vacate section 6T track relay GTR picks up and its contact I05 establishes the circuit to permit energy to be supplied to line circuit II during the pickedup periods of the contacts of code transmitter I20CT. At this time, as signal 68 displays a stop indication, relay ESP is released and the energy supplied to line circuit II is of reverse polarity. This energy feeds to line relays 41? and 4K and causes the contacts of relay 4P to occupy their right-hand or reverse position while relay 4K follows code so that energy is supplied through the transformer 4DT to relay 4H so that the contacts of relay 4H pick up. On picking up of its contact 66 the circuit of the red or stop lamp R of signal 48 is interrupted and the circuit including reverse polar contact 61 of relay 4P is established to light the yellow or caution lamp Y of signal 4S.

In addition, on picking up of the contacts of relay 4H its contact, 96 interrupts the stick circuit of relay 4SR. so that the contacts of relay 48R release and its contact I0! establishes the circuit to supply energy to the west end of line circuit II. This energy is of normal polarity as relay 3H is picked up and feeds to the line relays 5P and 5K so that the contacts of relay 5? occupy their normal or left-hand positions, while relay 5K responds to coded energy and energy is supplied through the transformer 5DT to the relay 5H. The circuit of relay 5I-IP continues to be interrupted by contact 18 of relay ELI-IS so that contact 19 of relay BHP remains released and maintains the circuit of the red or stop lamp of signal 5S.

On picking up of the contacts of relay 4H its contacts 55 and 51 establish connections to maintain the supply of energy to the east end of line circuit I after release of the contacts I03 and I04 of relay 48R.

On picking up of the contacts of relay 2H its contact 50 establishes the circuit controlled by code transmitter IBUC'I for supplying energy to coding relay WCR so that this relay operates at Accordingly, relay 2K operates at this higher rate and sufiicient energy is supplied through the resonant unit RU to pick up the relay 2J. Contact, 85 of. relay ZJ, therefore, picks up and establishes the circuit of the green ,or clear lamp G of signal 23.

, As the train proceeds through the track stretch, the signal 68 will again be conditioned to display its green or clear indication, assuming that the emote control apparatus, not shown,

, continues to cause the signal 68 to be governed by traffic conditions in advance.

When signal 6S again displays its clear indication contacts 81 and 88 of relay ESP pick up and change the polarity of the energy supplied to the east end of line circuit II from reverse to 4K continues to follow code and relay 4His maintained picked up to maintain the supply of energy of normal polarity and 180 code frequency to line circuit I so that signal 28 continues to display its green or clear indication.

The operation of the equipment on passage of a westbound train throughthe track stretch is substantially the same as for passage of an eastbound train through the stretch.

When the operator wishes to condition the track stretch for passage of a westbound train he operates the remote control apparatus to energize relay SLHS, and to cause signal [S to provide a proceed indication. When relay ELI-IS picks up its contact 18 completes the circuit of the relay 5H1? which thereupon picks up and its contact establishes the circuit of the yellow or caution lamp of signal 5S. When this signal displays a proceed indication relay. SLMR. releases to cut off the supply of energy to the east end of line circuit II and to connect the line circuit directly to the line relays 5P and 5K. In addition, contact 84 of relay BLMR establishes the circuit to supply energy from transformer 5DT to relay 5J so that relay 5J picks up and its contact I09 establishes the circuit of the green lamp G of signal 58. At this time relay 3H is picked up and its contact 69 establishes the circuit to supply energy of code frequency to coding relay WCR so that energy of this frequency is supplied to line circuit II. Accordingly, sufiicient energy is supplied through the resonant unit RU to pick up relay 5J. I I

As the supply of energy to the east end of line circuit II is cut off relay 4K ceases to follow code and relay 4H releases and conditions signal 4S to provide its red or stop indication, while release of contacts 55 and 51 of relay 4H changes the energy supplied to the east end of line circuit I from normal to reverse polarity and release of contact 50 of relay 4H changes the energy supplied to relay WCR from 180 to '75 code frequency.

On this change in the polarity of the energy supplied to the east end of line circuit I the polar contacts of line relay 2P shift to their reverse position and its contact 0 interrupts the'circuit of relay 21-1? to thereby insure that signal 28 will display a stop indication.

When signal I S is caused to display a proceed indication contacts 30 and 3| of relay l SP pick up and change the energy supplied to the west end of line circuit I from reverse to normal polarity so that the contacts of relay 3P shift from theirreverse to their normal positions and contact 52 establishes the circuit of the green lamp of signal 38.

-When the westbound train enters section 6T track relay BTR releases and its contact I05 prevents the supply of energy to line circuit II, while its contact I06 interrupts the circuit of relay SPH so that contact 19 of relay 5HP releases and establishes the circuit of the red or stop lamp R of signal 53.

In addition, as a result of release of track relay BTR the detector looking for switch NW becomes effective to prevent picking up of relay SLMR and thereby prevent movement of switch NW.

For purposes of illustration it will be assumed that the remote control apparatus is arranged so that the relay ELI-IS when picked up will not become released when track relay GTR is released, but will remain picked up until it is released by manipulation of the remote control apparatus by the operator.

When the train advances into section 5T track circuits line circuit II to insure, display of stop indications by signals 43 and S. When the train advances into section 4T track relay 4TB releases and additionally interrupts and short circuits line circuit II, while contacts 43 and 41 of relay 4TB. cut off the supply of energy to the east end of line circuit I and connect the relays 3P and 3K directly to the linecircuit. As a result of the cutting off of the supply of energy to the east end of line circuit I relay 2H releases and additionally interrupts the circuit of relay ZHP. In addition, release of relay 2H may look the switch MW, while it may operate indication means to give notice of the approach of the train. When the train advances into section 3T track relay3TR, releases and interrupts and short circuits-line circuit I, while its contact establishes the pick-up circuit of relay 38R. As a result of interruption of line circuit I relay 3H releases and establishes the holding circuit for relay 38R, and also establishes the circuit of the red or stop lamp R of signal 3S. In addition, on release of relay 3TB its contacts 90 and 9! prevent the supply of energy to the west end of line circuit II and connect line circuit II directly 'to the line-relays AP and 4K.

As a'result of picking up of the contacts of relay 3S5. its contact 5- 1 prevents the supply of energy to the east end of line circuit I, while its contacts H2 and H4 establish circuits to permit the supply of energy to line circuit II on picking up of track relay 3TB.

When the train advances into section 2T track relay ETR releases and additionally interrupts and short circuits line circuit I.

When the train vacates section 6T contact I05 of track relay GTR is picked up to permit energy to be supplied to reIay'BI-IP, while contact I05 of, track relay 6TB is picked up to permit-energy to be supplied to line circuit II. The energy supplied to line circuit II is of reverse polarity as relay ESP is released since signal 68 is displaying a stop indication.

When track relay 6TB picks up a pick-up circuit is established for relay BLMR as explained in the patent to McCann mentioned above, and this relay picks up to establish a stick circuit to maintain itself energized as long as signal 58 displays a stop indication, while on picking up of relay BLMR its contacts BI and 82 connect the line wires of line circuit II to the contacts of the code transmitter IZIJC'I' so that energy -may be supplied to the east end of line circuit II.

' When the train vacates section 5T track relay 5TB. picks up while when the train vacates section 4T track relay 4TB. picks up and energy supplied at the east end of line circuit II feeds to line relays 4P and 4K over the circuit which includes back contacts so and 9! of relay 'ETR.

Accordingly, relay 4H picks upand its contact 68 cooperates with reverse polar contact 51 of relay AP to establish the circuit of the yellow lamp Y of signal dS. l In addition, on picking up of relay 6H its contacts 55 and 57 establish connections to permit energy to be supplied to the west end of line circuit I. At this time track relay 4TB is picked up, but as track relay 3TR is released, and as contact 54 of relay 38R is picked up, energy is not supplied to line circuit I. When the train enters section IT track relay ITR releases and its contact 33 interrupts the circuit for supplying energy to the west end of line circuit I, while its contact 3% interrupts the circuit of relay ZHP to insure that this relay will remain released and maintain the display of a stop indication by signal 28.

In addition, on release of track relay ,ITR. signal IS is conditioned by means not shown to display its red or stop indication, while as a result of this change in the signal! S relay lSP releases to'cause energy subsequently supplied to line circuit I to be of reverse polarity.

For purposes of illustration it will be assumed that the remote control means, not shown, associated with signal IS, is unafiected by passage of the train, but is arranged to continue to cause this signal to be governed by traffic conditions in advance until changed by reason of manipulation of the remote control apparatus by the-operator.

When the train vacates section 3T trackrelay STR picks up and-its contacts 9%] and 9i establish the connections over which energy is supplied to the west end of line circuit II. At this time relay 353R is picked up while relay 31-1 is released so that energy of normal polarity is supplied to line circuit II. This energy feeds to relays 5P and 5K and relay 5K follows code so that energy is supplied through the transformer is released, and, accordingly, signal 58 continues to display its red or stop indication.

When the train advances far enough to vacate section 2T track relay ZTR picks up, but as contact 54 of relay 38B is picked up energy is not supplied to line circuit I and energy, therefore, is not supplied to relays 2? and 2K; Accordingly, relay 2H1? remains released and cannot be picked up and the signal 28 continues to display its stop indication.

When the train advances far enough to vacate section i'I track relay [TR picks up and its contact 33 establishes the circuit to supply energy to the west end of line circuit I. As pointed out above, at this time relay is is released, while re-'- lay 23L is picked up so that energy of reverse polarity is supplied to line circuit I. This energy feeds to relays BP and 3K so that energy is supplied through the transformer 313T to relay 3H. On picking up of relay 3H its contact 5% cooperates with reverse polar contact 52 of relay 3? to establish the circuit of the yellow or caution lamp Y of signal 33. In addition, on picking up of relay 3H its contact H5 interrupts the stick circuit of relay while its contact 89 changes the energy supplied to relay ECR from 75 to code frequency.

On release of relay 38R its contact 54 establishes the circuit to supply energy to the east end of line circuit I and this energy feeds to relays 2F and 2K so' that relay 2K follows code and energy is supplied through the transformer EDT to relay 2H. The energy supplied to line circuit I is of normal polarity as contacts 55 and 5! of "relay lI-I arepicked up so that the contacts of relay 2P shift to their normal positions. Although contact 58 of relay 2H, contact Ho of relay 2P, and contact M of relay ITR are closed, relay 2I-IP remains released as its circuit is interrupted by contact 25 of relay ZRHS so that signal 28 continues to display its red or stop indication.

In addition, on release of relay 355R its contacts H2 and H t release, but at this time contacts 65 and SI of relay Eli are picked up so that energy circuit II. a

Modification shown in Fig. 2

The system shown in Fig. 1 is arranged so that one stop and one caution indication is provided in the rear of a train. However, under some conditions, such as on stretches of downgrade track or where a passing siding is relatively short, one caution indication may not provide adequate warning of vthe presence of a train. In such situations it is desirable to provide two caution indications in the rear of a train so that a second or following train will have adequate distance in which to stop after receiving a restrictive indication. The system shown in Fig. 2 of the drawings is arranged so that for one direction of trafiic two caution indications are provided in the rear of a train in selected stretches. The system shown in Fig. 2 is similar to that shown in Fig. 1 and identical reference characters are employed in the two figures to identify the elements which are common to both systems. The system shown in Fig, 1 is arranged so that when an eastbound train is present in section IT signal 6S will display its red or stop indication, signal 4S will display its yellow or caution indication, while when remote control relay ZRHS is picked up signal 28 will display its green or clear indication.

The system shown in Fig. 2 is arranged so that under the same conditions signal 28 will display its yellow or caution indication.

On passage of a westbound train through the track stretch the system shown in Fig. 2 operates toprovide the same signal indications as the system shown in Fig. 1.

In the modification shown in Fig. 2 the portions of the equipment associated with signals 28 and 3S, that is the equipment associated with line circuit I, is substantially the same as that of the corresponding part of Fig. 1. This portion of the equipment differs from that shown in Fig. 1 in that the circuit of the coding relay WCR. is controlled by contact I42 of relay HN instead of by contact 50 of relay 4H.

In the modification shown in Fig. 2 the equipment associated with line circuit II differs somewhat from that shown in Fig. 1. In the modification shown in Fig. 2 the coding relay ECR at signal AS is continuously operated at '7 5 code frequency, while the line relays 4P and 4K and the associated equipment control the signal 43 and the supply of energy to line circuit I in response to both the frequency and the polarity of the energy supplied over line circuit II instead of in response to coded energy as in the system shown in Fig. 1.

The system shown in Fig. 2 further differs from that shown in Fig. 1 in that the signal 53 is governed only by the polarity of the energy supplied over line circuit II instead of by a combination of polarity and frequency.

The system shown in Fig. 2 also differs from that shown in Fig. 1 in that the frequency of the energy supplied to the east end of line circuit II is controlled by the aspects displayed by signal (is and the adjacent signal in advance. This control is effected by means of a relay GSA which is picked up when the signal 68 is displaying either its green or its yellow indication, and by relay BSA which is picked up when the signal SS is displaying either its yellow or its green indication.

The equipment is shown'in the condition which it assumes when the track stretch is vacant and the remote control relays are released so that signals IS, 2S, 5S and 68 display their red or stop indications.

I As signal BS is displaying its stop indication relay BSAis released and its contact I2I establishes the circuit controlled by code transmitter IZIICTior supplying energy to coding relay'CR so that the contacts of this relay pick up and 'release'at the code rate. I

As' relay BSAis released the energy supplied to line circuitII during the picked-up periods'of contacts 1.0 and II of coding relay GR is of reverse polarity. This energy feeds to line relays 4P and 4K over the circuit which includes back contacts I23 and I24 of relay HN and back contacts 63 and 64 of relay ECR. As the energy supplied to relay 4P is of reverse polarity contact 61 of relay 4? interrupts the circuit of relay I-IN and its contacts are released so that energy may be supplied to the west end of line circuit II during the picked-up periods of relay ECR.

In addition, as contact I28 of relay I-IN is released the circuit for supplying energy from transformer IDT to relay IJ is interrupted and relay M is released, and a circuit including front contact I3il of relay 4H and back contact I3I of relay 4.1 is established to light the yellow or caution lamp Y of signal 4S. 1

At this time relay 31-1 is picked up while ISR is released so that energy of normal polarity is supplied to the line circuit II during the picked-up periods of coding relay ECR. This energy is supplied to relays SP and 5K during the released periods of coding relay CR so that relay 5K responds to code while contact I25 of relay 5P occupies its left-hand or normal position as shown. At this time remote control relay 5LI-IS is assumed to be released and its contact I8 interrupts the circuit of relay 5H so that contact I26 of relay 5H is released and establishes the circuit of the red or stop lamp R. of signal 58.

As relay HN is released its contact I42 is released and establishes the circuit for supplying 0 energy of 75 code frequency to coding relay WCR.

At this time, as explained in detail in connection with the modification shown in Fig. 1, energy of normal polarity is supplied to the east end of line circuit I during the picked-up periods of coding relay WCR, While energy of reverse polarity is supplied to the west end of the line circuit I during the picked-up periods of the contacts of code transmitter IZBCT. Accordingly, relay 3K ffollows code and contact 5| of relay 31-1 is picked up and cooperates with reverse polar contact 52 of relay 3P to establish the circuit of the yellow lamp Y of signal 38.

In addition, at this time relay 2K follows code so that relay 2H is picked up while contact III) of relay 2P occupies its normal position as shown. The relay ZRHS is assumed to be released, however, and its contact 25 interrupts the circuit of the relay 2I-IP so that contact 26 is released and establishes the circuit of the red or stop lamp of signal 2S. I

As relay 2H is picked up it conditions the locking means, not shown, for switch MW to permit this switch to be moved.

The locking means for switch NW is controlled bya relay LR which is energized over a separate line circuit which is governed by track relays 3TH, 4TB. and 5TR. As the track stretch is assumed to be vacant relay LR is picked up and permits the switch NW to be moved.

Operation of modification shown in Fig. 2 on passage of an eastbound train In order to condition the track stretch for movement of an eastbound train the operator manipulates the remote control apparatus to energize relay ZRHS, while he also causes the remote control apparatus to condition signal 65 to be governed by traffic conditions in advance and by the aspect displayed by signal BS. The means by which this control of signal 68 is effected is not a part of this invention and this signal may be governed by any means well known in the art.

The signal 88 may be an automatic signal governed by traffic conditions in advance or it may be a remotely controlled signal similar to signal 28 which normally displays a stop indication, but which may be governed by remote control apparatus so that it is at times controlled by traflic conditions in advance. In the present case this signal is shown as being at the leaving end of a passing siding and it will be assumed that this signal is controlled in the same manner as signal 23. It will be assumed also that the operator manipulates the remote control apparatus to cause signal 88 to display an indication determined by trafiic conditions in advance and that the track stretch in advance is vacant so that the signal provides its green or clear indication.

As the signal 88 is displaying its green indication signal BS also displays its green or clear indication so that relays BSA and BSA are both picked up and energy of 180 code frequency is supplied to coding relay CR. As contacts 81 and 88 of relay BSA are picked up energy of normal polarity is supplied to the east end of line circuit II during the picked-up periods of the contacts of relay CR. This energy causes the contacts of relay AP to shift to their left-hand or normal positions and contact 61 of relay 4P completes the circuit of relay I-IN so that its contacts I23 and I24 are picked up and cut oil the supply of energy to the west end of line circuit II and con nect line circuit II directly to the line relays 4P and 4K so that thereafter relay 4K follows the 180 code supplied over the line circuit.

In addition, on picking up of relay HN its contact I28 establishes the circuit to supply energy from the decoding transformer 4DT to relay 4J and as relay 4K is following 180 code sufiicient energy is supplied through the resonant rectifier unit RU to pick up the relay lJ. Accordingly, contact I3I of relay 4J interrupts the circuit of the yellow or caution lamp Y and establishes the circuit of the green or clear lamp G of signal 48.

When the contacts I23 and I24 of relay HN are picked up the supply of energy to the west end of line circuit II during the picked-up periods of the contacts of coding relay ECR is cut oil so that relay K ceases to-follow code and relay 5H will remain released and maintain the display of a red or stop indication by signal 58 even if the remote control apparatus should be manipulated to pick up relay 5LHS.

On picking up of relay I-IN its contact M2 cuts off the supply of energy of '75 code frequency to coding relay WCR and establishes the circuit to supply energy of 180 code frequency to this re-- lay.

When remote control relay 2RI-IS is picked up its contact 25 completes the circuit of relay 2HP so that contact 26 of relay 2HP picks up and completes the circuit which includes back contact 35 of relay N for lighting the yellow or caution lamp Y of signal 28. When signal 2S displays a proceed indication relay 2RMR releases and its contacts 40 and 36 interrupt the supply of energy to the west end of line circuit I and connect the line circuit directly to the line relays 2P and 2K, while contact 39 of relay 2RMIR establishes the circuit for supplying energy from the transformer ZDT to relay ZJ. As relay 2K is connected directly to the line circuit it operates at 180 code frequency and suiiicient energy is supplied through the resonant rectifier unit RU to pick up the relay 2J. Contact of this relay therefore pick up and establishes the circuit of the green or clearlamp G of signal 28.

As a result of releasing of relay 2RMR the locking of switch MW becomes effective to prevent a change in the position of the switch.

As a result of the cutting oif of the supply of energy to the west end of line circuit I occasioned by release of the contacts of relay 2RMR relay 3K ceases to follow code and relay 3H releases and its contact 5I establishes the circuit of the red or stop lamp R of signal 33.

In addition, as a result of the release of relay 3H its contacts 68 and 6!, which control the polarity of the energgy supplied to line circuit II, release, but as relay HN is picked up and interrupts the supply of energy in the line circuit at this time release of relay SE is without effect.

When an eastbound train enters section IT track relay ITR releases and its contact 33 interrupts the circuit for supplying energy to the west end of the line circuit I. However, at this time as relay 2RMR is released energy is not supplied to the West end of line circuit I.

In addition, on release of track relay ITR its contact 34 interrupts the circuit of relay 2HP so that its contact 26 releases and establishes the circuit of the red or stop lamp R of signal 28 When the train advances into section 2T track relay 2TB releases and interrupts and short circuits the line circuit I so that relay 2K ceases to follow code and energy is no longer supplied through the transformer ZDT to relays 2H and 2J. Accordingly, relay 2H releases and its contact 58 additionally interrupts the circuit of the relay 2HP so that contact 26 of relay 2HP remains released and maintains the circuit of the red or stop lamp R of signal 25.

On this change in the aspect displayed by signal 2S relay ZRMR may be energized and its contacts All and 36 pick up. However, energy cannot be supplied to line circuit I as track relays ITR and 2TR are released. 7

7 When the train advances into section 3Ttrack relay 3TR releases and additionally interrupts and short circuits line circuit I. On release of track relay 3TB, its contacts IEI and I32 interrupt the circuit of the lock relay .LR and this relay releases and locks the switch NW to prevent a change in the position of the switch until after the expiration of a time interval.

In addition, on release of track relay 3TB, its contacts 99 and SI interrupt the circuit including the front contacts I23 and I24 of relay HN for connecting the line circuit II to line relays 4P and 4K and connect the line circuit directly to these relays.

When the train enters section 4T track relay ATR releases and its contacts I35 and I36 additionally interrupt the circuit of relay LR, while its contacts 93 and st interrupt and short circuit line circuit II, and its contact 95 establishes the pick-up circuit of relay SR.

On interruption of the line circuit II relay 4K ceases to'follow'code-so that energy'is no longer suppliedto therelays 4H and M and these relays release so that contact I39 of relay IH establishes the circuit of the red or stop lamp R of signal 48. In addition, on release of relay 4H its contact 96 establishes a stick circuit to maintain relay R. picked up, while contact 98 of relay 41-1 interrupts the circuit of relay HN so that contact I42 of relay I-IN releases and changes the ener y suppliedto coding relay-WCR from 180 to codefrequency. At this time, however, relay 4TB is released and its contacts 43 and 4! connect the wires of line circuit I directly to the line relays 3P and 3K and prevent the supply of energy to the east end of line circuit I.

When the train advances into section 5T track relay ETR releases and additionally interrupts and short circuits the line circuit II, while contacts I31 and I38 of relay 5TB. additionally interrupt the circuit of lock relay LR.

When the train advances into section 6T track relay 6TB releases and causes signal 68 to display its red or stop indication, while release of relay 6TB causes the detector looking for switch NW to be effective. When signal 68 displays its stop indication relay GSA is released, while when contact I of relay 6TB is released it prevents the supply of energy to the east end of line circuit II.

The remote control apparatus for controlling signal 65 may be arranged in the manner Well known in the art so that when the apparatus is manipulated to cause this signal to be governed by traffic conditions in advance the signal will continue to be governed in this manner until the remote control apparatus is further manipulated to again cause signal 68 to provide its stop indication regardless of trafiic conditions in advance.

When the train advances into section 8T track relay 8TB. releases and causes signal ES to display its red or stop indication so that relay 88A releases.

When the train vacates section IT track relay ITR picks up, and as explained in the above mentioned patent to Ronald A. McCann a pick-up circuit is established for the relay ZRMIR and this relay picks up and establishes a stick circuit to maintain itself picked up as long as signal 2S continues to display a stop indication. When the train vacates section 2T track relay ZTR picks a up and energy of reverse polarity is supplied to the West end of line circuit I over the back contacts of relay ISP and the front contacts of relay 2RMR. When the train vacates section 3T track relay 3TB. picks up and the energy supplied to 5:

line circuit I feeds over the front contacts of track relay 3TH. and the back contacts 43 and II of relay 4TH to line relays SP and 3K so that relay 3-K follows code and energy is supplied to relay 3H. Accordingly, relay 3H picks up and its contact 5| cooperates with reverse polar contact 52 of relay 3? to establish the circuit of the yellow or caution lamp Y of signal 38.

When the train vacates section 4T track relay ITR picks up and its contact interrupts one stick circuit for relay ISR, but this relay is maintained energized by current supplied over the circuit which includes its own front contact 9'! and back contact 96 of relay 4H.

When track relay 4TH picks up its contacts 43 and II connect the line Wires of line circuit I to the contacts of coding relay WCR. so that thereafter the line relays SP and 3K are energized only during the released periods of the coding relay contacts. while during the picked-up periods of the coding: relay contacts energy of normal ;po larity is supplied to the line circuit I over back contacts 55 and 5'! of relay 4H, and front contacts I03 and I04 of relay ISR. This energy 5 feeds to line relays 2P and 2K, and relay 2K follows code and energy is supplied through transformer 2DT to relay 2H-so that this relay picks up. At this time relay WCR is operating at the 75 code'frequency rate as contact I42 of i0 relay HN is re1ea'sed.' Y It will be assumed thatth'e remote control sys-" tem is arranged so that the'relay' ZRHS, when picked up remains picked up after passage ofa train unless the operator manipulates the remote control apparatus to release this relay. It will be assumed also that the equipment has not been operated to release the relay ZRHS, or if this re-' lay did release that the equipment Lhas'been operated to cause it to pick up again.

Accordingly, when the train vacates section 4T and energy is supplied to the east endzof line circuit I so that relay 2H picks up, the circuit of relay 21-1]? is complete and the contact 26 of this relay picks up to establish the circuit of the yel- 25 low lamp Y of signal 28. Onqthis change'i'n the aspect of signal 28 relay 2RMR releases and. cuts off the supply of energy to the west end of line circuit I and connects line circuit I directly to line relays 2P and 2K. In addition, contact 39 30 of relay ZRMR establishes the circuit for supplying energy from transformer 2DT to relay 2.1. However, at this time relay HN is released and energy of '75 code frequency is supplied to the coding relay WCR so that energy of this frequency 35 is supplied over line circuit I to relay 2K and too little energy is supplied through the resonant rectifier unit RU to pick up relay 2J. Contact 85 of this relay therefore remains released and maintains the circuit of the yellow or caution 40 lamp Y of signal 28. a

On release of relay ZRMR the supply of energy to the west end of line circuit I is cut off and relay 3K therefore ceases'to respond ,to coded energy so, that relay 3H releases and its contact 5I establishes the circuit of the red orstop lamp R of signal 38, u

When the'train advances far enough to vacate section 5T track relay 5TB. picks up. However, at this time relay 48R is picked up and its contact I01 interrupts the supply of energy to the west end of line circuit II so that on picking up of track relay 5TB energy is not supplied to line relays SP and 5K.

When the train advances far enough to vacate section 6T track relay 6TB picks up and its contact I05 establishes the circuit to supply energy to the east end of line circuit II. Energy may'be supplied to the east end of linecircuit IIat this time as lock relay 5LMR remains picked up since signals 58 and ESA have continuously displayed stop indications. j

When the train vacates section 6T signal 68 continues to display its red or stop indication and relay SSA remains released so that energyvof reverse polarity and code frequency is supplied to the coding relay CR. This energy feeds to line relays AP and 4K over the circuit which includes back contacts I23 and I24 of relay HN, and back contacts 63 and 64 of coding relay ECR.

As the energy is of reverse polarity the contacts of relay 4P shift to their right-hand or'reverse positions and contact 61 interrupts the circuit of relay HN to thereby maintain this relay released so that its contact I28 interrupts the circuit of relay IJ and its contact I42 maintains the supply of. energy of 75 code frequency to codl y WCR... The ener y supplied to relay 4K produces code followin operation of this relay so that relay 4H picks up and its contact I351 establishes the circuit of the yellow or caution lampY of signal 4S.

When relay 4H picks up its contact 96 interrupts the stick circuit of relay lSR sov that relay R. releases and its contact I01 establishes the circuit for supplying energy to the west end of line circuit II. This energy is of reverse polarity as relay 3H is released. This energy feeds to line relays 5]? and 5K and produces code following operation of relay 5K, but as relay ELHS is released energy is not supplied to relay 5H and its contact I26 remains released and maintains the circuit of the red or stop lampR of signal 58.

On picking up of the contacts of relay 4H con tacts and 57 interrupt one circuit and establish another for supplying energy to the east end of a line circuit I so. that energy of normal polarity and '15: code frequency continues to be supplied to! this circuit and signal 26 continues to display its yellow or caution indication.

It, will be seen, therefore, that when an eastl bound train advances. far enough to vacate section 6T energy of reverse polarity and 120 code frequency is supplied to the right-hand or east end of line circuit II with the result that relay 4H picks up and establishes the circuit of the yellow or caution lamp Y of signal 4S, while contact 61 of relay 4P interrupts the circuit of relay HN. Accordingly, contact It?! of relay HN maintains the supply of energy of '75 code frequency to the east end of line circuit I to maintain the display of the yellow or caution indication by signal 28. At this time. therefore, the signal 6S displays its red or stop indication, while signals 48 and 2S both display their yellow or caution indications so that there are a red and two yellow signal indications in the rear of the train in section IT, and a second or following train will have ample warning of the presence of a first train and will have adequate distance in which to stop.

When the train advances far enough to vacate section IT signal BS is conditioned by means not shown to display its yellow or caution. indication. and on this change in the indication. displayed by signal 6S relay BSA picks up. On picking up of relay BSA its contacts 81 and 88. change the polarity of the energy supplied to the east end of line circuit II from reverse to normal while contact 12! of relay ESSA interrupts. one cicuit for supplying energy of 120 code frequency to coding relay CR and establishes the circuit which includes back contact l3 ,9 of relay BSA for supplying energy of 12.0 code frequency to coding relay CR.

The energy of 120 code frequency and normal polarity supplied over line circuit II causes relay 4H to continue to be energized, while contact 61 of relay 4P is shifted to its left-hand or normal position and completes the circuit of the relay HN. Accordingly, relay HN picks up and its contacts I23 and I24 cut off the supply of energy to the west end of line circuit II and connect the line relays 4P and 4K directly to the line circuit, while contact I42 of relay HN interrupts the circuit for supplying energy of '75 code frequency to relay WCR and establishes the circuit for supplying energy of 180 code frequency to this relay.

On this change in the frequency of the energy supplied to line circuit I relay ZJ picks up and.

its contact interrupts the circuit of the yellow lamp Y of signal 28 and establishes the circuit of the green or clear lamp G of this signal.

At this time, therefore, signal 88 displays its red indication, while signals 68 and 48 display their yellow indications and signal 28 displays its green or clear indication.

When the train in section 8T advances far enough in the track stretch for signal 88 to display a proceed indication the aspect of signal 63 changes from caution to clear while relay 8SA picks up. Under these conditions the relays BSA and BSA are both picked up and energy of code frequency is supplied to coding relay CR over the circuit which includes front contact I39 of relay 85A and front contact l2! of relay SSA.

When the relay 4K responds to energy of 180 code frequency, sufiicient energy is supplied through the resonant rectifier unit RU to pick up elay 4J. Accordingly, its contact I31 establishes the circuit of the green lamp G of signal 45.

On this change in the aspect of signal 48 there is no change in the energy supplied to line circui-t I and signal 28 continues to display its green or clear indication.

From the foregoing it will be seen that the modification shown in Fig. 2 operates to provide twoyellow or caution signals in the rear of a train in a selected portion of the track stretch to thereby provide increased braking distance in these regions.

Operation of the modification shown in Fig. 2 on passage of a westbound train through the track stretch For purposes of illustration it will be assumed that the track stretch is vacant and that the remote control apparatus is manipulated to condition the track stretch for passage of westbound trains.

In order to condition the stretch for passage of Westbound trains the remote control apparatus is manipulated to cause signal IS to be controlled by traiiic conditions in advance, and as the track stretch is assumed to be vacant signal IS will display its green or clear indication.

The remote control apparatus is also manipulated to pick up relay ELI-IS so that signal 58 will. provide. a proceed indication, while the westbound signals in the rear of signal 53 are also governed so as to provide proceed indications.

When signal is displays its green or clear indication contacts 30 and 3| of relay iSP are picked up so that energy of normal polarity is supplied to the west end of line circuit I. This energy causes the contacts of polar line relay 3P to. occupy their lefthand or normal positions and contact 52- establishes the circuit of the green lamp G of signal 38.

Energy of 75 code frequency and normal polarity continues to be supplied to the west end of line circuit II at this time so that when relay ELIIS is picked up energy is supplied to relay 5H and its. contact MG, establishes the circuit which includes normal polar contact E25 of relay 5? to light the green or clear lamp G of signal 5S.

when signal 58 displays a proceed indication relay ELMR releases to thereby connect the line circuit II directly to line relays EP and 5K and to. out, oi? the supply of energy to the east end of line circuit II. As a result relay 3K ceases to follow code so that relay 4H releases and its contact I30 establishes the circuit of the red or stop lamp R of signal is. When relay 4H releases its contacts 55 and 5? change the energy supplied to the east end of line circuit I from normal to reverse polarity.

On this change in the polarity of the energy supplied to line circuit I contact IEO of relay 2P shifts to its reverse position to interrupt the circuit of relay ZHP and prevent energization of this relay if the remote control apparatus should be manipulated to pick up relay ZRI-IS.

As relay ZHP is maintained released the signal 2S will display its stop indication, while as relay 2H is picked up the switch MW is not locked but may be moved if desired.

When the train enters section 6'1 and the track relay BTR releases the detector looking for switch NW becomes effective. When track relay BTR releases its contact I05 interrupts the circuit for supplying energy to the east end of line circuit II, while its contact I06 interrupts the circuit of relay 5H so that contact I26 of relay 5H releases and establishes the circuit of the red or stop lamp R, of signal 55.

In addition, as a result of the release of track relay 6TB, the detector locking for switch NW is elfective and this switch cannot be moved.

When the train advances into section 5T, track relay 5TB, releases and interrupts and short circuits line circuit II so that energy is no longer supplied to the line relays 5? and 5K. Accordingly, energy is no longer supplied through the decoding transformer EDT and the relay 5H will remain released after contact I06 of track relay 6TB, is picked up.

When the train advances into section 4T, track relay 4TB. releases and additionally interrupts and short circuits line circuit II, while its contacts 43 and 4! release and out off the supply of energy to the east end of line circuit I and connect the line wires of line circuit I directly to line relays 3P and 3K so that signal 38 continues to display its green or clear indication.

As a result of interruption of the supply of energy to line circuit I, relay 2K ceases to follow code and energy is no longer supplied to relay 2H and this relay releases to condition the switch locking means, not shown, to lock the switch MW.

When the train advances into section 3T, track relay 3TB, releases and interrupts and short circuits line circuit I so that energy is no longer supplied over this circuit to line relays 3P and 3K. Accordingly, relay 3K ceases to follow code and energy is no longer supplied to relay 3H and its contact 5| releases and establishes the circuit of the red or stop lamp R of signal 38.

In addition, on release of track relay 3TB. its contact I40 establishes the pick-up circuit for relay SES so that its contact I II picks up and establishes a stick circuit for the relay. The pick-up circuit for relay 3E5 includes front contact I I5 of relay 3H, while on release of this contact another stick circuit is established for relay 3E8.

As a result of picking up of relay 38R, its contact 54 interrupts the circuit for supplying energy to the east end of line circuit I to thereby prevent the supply of energy to this line circuit until the train vacates section IT.

Furthermore, on release of track relay 3TB its contacts 90 and 9| cut ofi the supply of energy to the west end of line circuit II and connect the line wires of this line circuit directly to the line relays 4P and 4K.

When the train advances into section 2T, track relay ZTR releases and additionally interrupts and shunts line circuit I, while when the train enters section IT, track relay ITR releases and its contact 33 prevents the supply of energy to the west end of line circuit I, while contact 34 of track relay ITR releases and interrupts the circuit of relay ZHP so that relay 2HP will remain released and maintain the display of a stop signal by signal 28.

In addition, on release of track relay I'I'R. the detector looking for switch MW becomes effective, while signal IS is conditioned by means not shown to display its red or stop indication.

When the rear of the train vacates section 6T, track relay 0TB. picks up and its contact I05 establishes the circuit to permit energy to be supplied to the east end of line circuit II, while contact I 06 of track relay 6TB is picked up to permit energy to be supplied to relay 5H.

In addition, on picking up of track relay 6TB. a pick-up circuit is established for relay SLMR, as explained in the patent to McCann, while on picking up of relay SLMR a stick circuit is established to maintain the relay energized as long as signal 5S displays a stop indication. Also on picking up of relay 51MB, its contacts 8| and 82 establish connection from line wires 22 and 23 to contacts I0 and II of coding relay CR so that energy may be supplied to line circuit II.

At this time signal 68 displays its red indication so that relay BSA is released and the energy sup,- plied to line circuit II is of reverse polarity.

When the train vacates section 5T, track relay 5TH. picks up, while when the train vacates sec tion 4T, track relay 4TB. picks up and energy supplied to the east end of line circuit II is supplied over back contacts and 9| of track relay 3TH to line relays 4P and 4K. This energy is of reverse polarity so that contact 61 of relay 4P occupies its reverse position and interrupts the circuit of relay HN and contact I28 of relay HN is released and interrupts the circuit of relay 4J. The energy supplied to line relay 4K causes code following operation of this relay and energy is supplied through the transformer 4DT to relay ll-I so that contact I30 of relay 4H picks up and establishes the circuit of the yellow or caution lamp Y of signal as.

On picking up of track relay 4TH its contacts 43 and 4'! connect the line wires of line circuit I to the contacts of coding relay W'CR so that energy may be supplied to the west end of line circuit I during the picked-up periods of this relay and may be supplied over the line circuit I to the line relays 3P and 3K during the released periods of the contacts of relay WCR. At this time relay WCR is operated at the '75 code rate as contact I42 of relay HN is released.

When the train vacates section 3T, track relay 3TB picks up and its contacts 00 and 9! establish the circuit to permit energy to be supplied to the west end of line circuit II and thus to the line relays SP and 5K. This energy is of reverse polarity as contacts 60 and SI of relay 3H are released. If the remote control relay SLHS has remained picked up, or if it became released the remote control apparatus has been manipulated to pick it up again, energy will be supplied through transformer EDT to relay 51-1 on code following operation of relay 5K, and contact I25 of relay 5H will pick up and establish the circuit including reverse polar contact I25 of relay 5P to light the yellow or caution lamp Y of signal 58.

In addition, on picking up of the contacts of track relay 3TH, its contact M interrupts one stick circuit for relay 3E8, but this relay is maintained picked up by energy supplied over the stick circuit which includes its own front contact MI and back contact 4150f relay 3H. As relay 3SR is maintained picked up, its contacted continues to prevent the supply of energy to the east end of line circuit I.

When the train advances far enough to vacate section 3T the circuit of the lock relay LR is complete and this relay is picked up to permit the switch NW to be moved.

When the train vacates section 2T, track relay 2TB, picks up, but as contact '54 of relay 3S5, re-

mains picked up, energy is not supplied to line circuit I and does not :feed to line relays 2? and K.

When the train advances far enough to vacate section .IT, track relay ITR picks up and its contact 33 establishes the circuit for supplying energy to the west end of line circuit 1. it this time .relay [SP is released so that the energy supplied .to line circuit I is of reverse polarity, while relay 2RMR is picked up as signals 28 and 28A have continued to display stop indications so that energy is supplied to line circuit I. This energy feeds to relays BF and 3K and relay 3K follows code so that energy is supplied through the transformer SD'I to relay 3H. Accordingly, contact 51 of relay 3H picks up and cooperates with reverse polar -'contact 52 of relay 3? to establish the circuit of the yellow or caution lamp Y of signal 38. Inxaddition, contact N of relay 3H interrupts the stick circuit of relay so that contact 54 of relay 3E3 releases and establishes the circuit to supply energy to the east end of line circuit I. At this time relay ill is picked up so that the energy supplied to linecircuit I is of normal polarity.

Ihe energy supplied to the east end of line circuit I feeds to line relays 21 and 2K and relay 2K follows'code so that energy is supplied through transformer EDT to relay 2H, while contact Ms of relay 2? occupies its normal position as shown. However, until the remote control relay ZR'HS is energized, relay 2H1? remains released and maintains the circuit of the red or stop lamp R of signal 28. As relay ZRMR is picked up, its contact 39 interrupts the circuit of the relay M and this relay remains released.

Wh n the train advances far enough in the track stretch for the signal IS to again display its green or clear indication, relay iSP picks up and changes the energy supplied to the west end oi line circuit I from reverse to normal polarity. As a result, the contacts of relay iP shift from their reverse to their normal positions and contact 52 establishes the circuit of th green or clear lamp of signal 38.

From the foregoing it will be seen that when a Westbound train passes through the track stretch, signal 58 will display its red or stop indication until the train vacates section ST, and that signal 38 will display its red or stop indication until the train vacates section IT. When the train vacates section lT, signal is displays its stopindication, while signal 38 displays its caution indication, and signal 55; displays its green or clear indication. Accordingly, a second or following Westbound train will receive only one caution indication before reaching a signal displaying a stop indication.

Although the modification shown in Fig. 2 of the drawings has been illustrated and described asproviding two caution indications in the rear ofan eastbound train and one caution indication in'the rear of a westbound train, it 'is obviousthat the equipment may be arranged to provide two caution indications in the rear of a westbound train and one caution indication in the rear of an eastbound train. r

Similarly the equipment shown in Fig. 2 may bev arranged to provide two caution indications in the rear of trains traveling in each direction. This method of operation maybe secured bylsubstitutin'g for the equipment associated with line circuit =I equipment arranged in the same manner as that associated with line circuit II.

In such .a modification energy of '75 code frequency would be supplied to the east end-of line circuit I, while this energy would be of normal or reverse polarity according to whether relay iH ispicke'd up or released.

The frequencyand polarity of the energy supplied to the west end of line circuit I would be governed in the same manner as theenergy-su'pplied to the east end of line circuit II is controlled, while the supply of energy to the east end or -line circuit I :and to the west end of line circuit 11 will be controlled by the :directional stick relays as at present. In addition, in such a modification the approach locking of the switch will be controlled over -a separate line circuit similar to that for controlling switch NW.

From the foregoing it will be seen that this invention provides an improved signaling system adapted *for use in traCkstr-etches in which the signals are governed by remote control apparatus. The system is arranged so that when the remote control apparatus has been manipulated to clear the 'signalsfor one-dlrection-of trafiic, the energy supplied to the line circuits for controlling the signals for the other direction of trafiic is either out on or its polarity is changed so that the signals for such other direction of traffic cannot be conditioned to provide proceed indications.

.lt will be seen also that some modifications of this invention provide means not only for controlling the signals for both directions of trafiic rover onelinecircuit but also provide means operzative over the same line circuit for controlling locking of the switches at the .passing sidings.

In addition, it will be seen that the system provided by this invention enables more than one caution indication to be provided .in the rear of a train in sele'ctedlocations if desired.

The system provided by this inventiona't times makes use of mutilated code generated by operation of coding devices at opposite ends of a line circuit at different rates, and at such times the frequency responsive portions of the equipment is rendered inoperative so that it is unafiected by the. irregular code. When the frequency responsive apparatusris intended to functio'n thecoding device at that end of the line circuit is cut out :and the-line relays are connected directly to the line circuit so that accurate unmutilated'code is supplied to the line relays at such times.

Although I have herein shown and clescribed :only two forms :of railway signaling system emrbo'dyi'ng mylinvention, it isunderstood that vari- -ous changes and modifications may be made :the'rein within-the scope of the appended claims without departing irom the spirit and scope of :my invention. 7 I

Having thus "described-my invention, what I :clainris:

,1,;In :coinbination, a stretch of railroad track "havingla :pair of track rails over which trafiic im'oves in both directions, the rails of the track stretch being divided by insulated joints into a plurality of track sections including an intermediate section having at one side a first section and at the other side a second section, a first signal governing movement of traffic from the first section into the intermediate section, a second signal governing movement of trafiic from the second section into the intermediate section, a pair of control conductors substantially cOeX- tensive with and controlled by traific conditions in said intermediate section, a first coding device and a first electroresponsive device at the end of the control conductors adjacent said first signal, a second coding device and a second electroresponsive device at the end of the control conductors adjacent said second signal, each of said coding devices having contacts continuously actuated between a position in which they establish connection from the control conductors to the associated electroresponsive device and a position in which they permit connection to be established between said control conductors and a source of current, each of said electroresponsive devices controlling the associated signal, and means-effective on the display of a proceed indication by the first signal to connect the first electroresponsive device directly to the control conductors and to interrupt the supply of energy to the control conductors over the connections controlled by said first coding device.

2. In combination, a stretch of railroad track having a pair of track rails over which trafiic moves in both directions, the rails of the track stretch being divided by insulated joints into a plurality of track sections including an intermediate section having at one side a first section and at the other side a second section, .a first signal governing movement of traific from the first section into the intermediate section, a second signal governing movement of traflic from the second section into the intermediate section, a pair, of control conductors substantially coextensive withand controlled by traific conditions in said intermediate section, a first coding de- .vice and a first electroresponsive device at the end of the control conductors adjacent said first signal, a second coding device and a second electroresponsive device at the end of the control conductors adjacent said second signal, each of said coding devices having contacts continuously actuated between a position in which they establishconnection from the control conductors to the associated electroresponsive device and a position in which they permit connection to be established between said control conductors and a source of current, each of said electroresponsive devices controlling the associated signal,

vand means efiective on the display of av proceed indication by the first signal to interrupt the supply of energy to the control conductors over the connections controlled by said first coding device.

3. In combination, a stretch of railroad track having a pair of track rails over which traflic moves in both directions, the rails of the track stretch being divided by insulated joints into a plurality of track sections including an intermediate section having at one side a first section and at the other side a second section, a first signal governing movement of traffic from the first section into the intermediate section, a second signal governing movement of traflic from the second section into the intermediate section, a pair of control conductors substantially coextensive With and controlled by trafiic conditions in said intermediate section, a first coding device and a first electroresponsive device at the end of the control conductors adjacent said first signal, a second coding device and a second electroresponsive device at the end of the control conductors adjacent said second signal, each of said coding devices having contacts continuously actuated between a position in which they establish connection from the control conductors to the associated electroresponsive device and a po-. sition in which they permit connection to be established between said control conductors and a source of current, the second electroresponsive device controlling the second signal, means governed by said first electroresponsive device and by manually controlled means for controlling said first signal, and means efiective on the display of a proceed indication by said first signal to interrupt the supply of energy to the control conductors over the connections controlled by said first coding device.

4. In combination, a stretch of railroad track having a pair of track rails over which traffic moves in both directions, the rails of the track stretch being divided by insulated joints into a plurality of track sections including an intermediate section having at one side a first section and at the other side a second section, a first signal governing movement of traffic from the first section into the intermediate section, a second signal governing movement of trafiic from the second section into the intermediate section, a pair of control conductors substantially coextensive with and controlled by trafiic conditions in said intermediate section, a first coding device and a first electroresponsive device at the end of the control conductors adjacent said first signal, a second coding device and a second electroresponsive device at the end of the control conductors adjacent said second signal, each of said coding devices having contacts continuously actuated between a position in which they establish connection from the control conductors to the associated electroresponsive device and a position in which they permit connection to be established between said control conductors and a source of current, the contacts of the first coding device being operated at a first rate and the contacts of the second coding device being operated at times at a second rate and at other times at a third rate, the second electroresponsive device controlling the second signal, means governed by the first electroresponsive device for controlling said first signal, said first electroresponsive device selectively controlling said first signal in accordance with the rate of supply of impulses of energy thereto and thereby in accordance with the rate of operation of the second coding device, and means effective on the display of a proceed indication by the first signal to interrupt the supply of energy to the control conductors over the connections controlled by said first coding device and to connect said first electroresponsive means directly to said control conductors.

5. In combination, a stretch of railroad track having a pair of track rails over which traflic moves in both directions, the rails of the track stretch being divided by insulated joints into a plurality of track sections including an intermediate section having at one side a first section and at the other side a second section, a first signal governing movement of trafiic from the first section into the intermediate section, a second signal governing movement oftraflic from the second section into the intermediate section, a pair of control conductors substantially coextensive with and controlled by trafiic conditions in said intermediate section, a first coding device and a first electroresponsive device at the end of the control conductors adjacent said first signal, a second coding device and a second electroresponsive device at the end of the control conductors adjacent said second signal, each of. said coding devices having contacts continuously actuated between a position in which they establish connection from the control conductors to the associated electroresponsive device and a position in which they permit connection to be established between said control conductors and a source of current, the contacts of the first coding device being operated at a firstrate and the contacts of the second coding device being operated at times at a second rate and at other times at a third rate, the second electroresponsive device controlling said second signal, a first and a second auxiliary relay associated with said first electroresponsive device, the first auxiliary'relay being picked up whenever said electroresponsive device is responding to coded energy, the second auxiliary relay being picked up only when said electroresponsive device is responding to coded energy of the frequency supplied when the contacts of said second coding device are operated at said second rate, means governed by said first auxiliary relay for conditioning said first signal to display one proceed indication, means effective on the display of a proceed indication by said first signal to interrupt the supply of energy to the control conductors over the connections controlled by said first coding device to connect said first electroresponsive device directly to said control conductors and to establish the circuit of said second auxiliary relay, and means governed by said second auxiliary relay for conditioning said first signal to display another proceed indication.

6. In combination, a stretch of railroad track having a pair of track rails over which trafiic moves in both directions, the rails of the track stretch being divided by insulated joints into a plurality of track sections including an intermediate seciton having at one side a first section and at the other side a second section, a first signal governing movement of traffic from the first section into the intermediate section, a second signal governing movement of trafiic from the second section into the intermediate section, a pair of control conductors substantially coextensive with and controlled by traffic conditions in said intermediate section, a first coding device and a first electroresponsive device at the end of the control conductors adjacent said first signal, a second coding device and a second electrorespon sive device at the end of the control conductors adjacent said second signal, each of said coding devices having contacts continuously actuated between a position in which they establish connection from the control conductors to the associated electroresponsive device and a position in which they permit connection to be established between said control conductors and a source of current, means for causing the energy supplied to the control conductors over the connections controlled by the contacts of the second coding device to be of normal polarity at times and of reverse polarity at other times, the second electroresponsive device controlling said second signal, means governed by the first electroresponsive device for controlling said first signal, said meansbei'ng effective to cause said signal to display a proceed indication only when energy of normal polarity is supplied to said first electroresponsive device, and means efiective on the display of a proceed indication by said first signal to interrupt the supply of energy to the control conductors over the connections controlled by said first coding device.

'7. In combination, a stretch of railroad track having a, pair of track rails over which traific moves in both directions, the rails of the track stretch being divided by insulated joints into a plurality of track sections including an intermediate section having at one side a first section and at the other side a second section, a first signal governing movement of trafiic from the first section into the intermediate section, a second signal governing movement of trafiic from the second section into the intermediate section, a pair of control conductors substantially coextensive with and controlled by traffic conditions in said intermediate section, a first coding device and a first electroresponsive device at the end of the control conductors adjacent said first signal, a second coding device and a second electroresponsive device at the end of the control conductors adjacent said second signal, each of said coding devices having contacts continuously actuated between a position in which they establish connection from the control conductors to the associated electroresponsive device and a position in which they permit connection to be established between said control conductors and a source of current, means for causing the energy supplied to the control conductors over the connections controlled by the contacts of the second coding device to be of normal polarity at times and of reverse polarity at other times, the second electroresponsive device controlling the second signal, a first and a second auxiliary relay associated with the first electroresponsive device, means effective when said first electroresponsive device is supplied with coded energy of either polarity for energizing said first auxiliary relay, and means effective when said first section is unoccupied,

the first auxiliary relay is energized, and the first electroresponsive device is supplied with energy of normal polarity to energize the second auxiliary relay, said second auxiliary relay being effective when energized to cause said first signal to display a proceed indication.

8. In combination, a single track railroad having a stretch of single track between two passing sidings, said single track stretch being divided by insulated joints into a first and a second section, a first headblock signal governing entrance of trains moving in one direction into the first track section and a second headblock signal governing entrance of trains moving in the other direction into the second track section, a first intermediate signal governing movement of trains from the second section into the first section, a second intermediate signal governing movement of trains from the first section into the second section, a first pair of control conductors substantially coextensive with said first track section, a second pair of control conductors substantially coextensive with said second track section, each pair of control conductors having at each end thereof a coding device and an electro-responsive device, each of said coding devices having contacts continuously actuated between a position in which they establish connection from the control conductors to the associated electroresponsive device and a position in

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