US2843731A - Polarized track circuit railway signaling apparatus - Google Patents

Description

C. B. SHIELDS July 15, 1958 POLARIZED TRACK CIRCUIT RAILWAY SIGNALING APPARATUS 4 Sheets-Sheet 1 Filed Jan. 29, 1953 lxvvzwwgiz Charles B. Sbzelds.

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HIS ATTORIVF' United States Patent POLARIZED TRACK'CIRCUIT RAILWAY SIGNALING APPARATUS Charles B. Shields, Penn Township, Allegheny County, Pa., assignor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application January 29, 1953, Serial No.-333,983

5 Claims. (Cl. 2463) My invention relates to railway trafiic Controlling apparatus and particularly to coded polarized track circuits applied to single track, two direction signaling systems. More particularly, myinvention relates to a signaling system of the above character in which the direction of trafiic is established by a code sent out from a central traflic controlling station or by other suitable manual control. Accordingly, the directional control of the system embodying my invention is not automatic as in the case of standard APB circuits.

The present invention is an improvement on the circuits shown and described in United States Reissue Patent No. 22,841, granted to me on February 11, 1947, for Railway Traffic Controlling Apparatus. The novelty in my present invention resides chiefly in using continuous polarized code pulses for establishing the direction of traffic rather than using a singletransient code pulse as was employed in the above-mentioned patent.

One object of my invention is to provide for thereversal of traflic direction without the use of control line wires, by reversing the polarity of the track circuit.

Another object of my inventionis'to provide directional locking between headblock signals so that traffic direction cannot be reversed or the opposing headblock signal cleared while the section is'occupied by a train.

' A further object of my invention is to provide for approach energizati'on of the intermediate wayside signals by selecting the polarity of the approach code.

Still --a further object of my invention is to dispense with all control wires except the control wires necessary in-a centralized traflic control system or other manual traflic control'and to provide a safe and effective system of twodirection, singletrack signaling.

Yet another object of my invention is to make use of the same track battery which supplies the approach code energy for supplying the feedback track energy upon a reversal of traffic direction.

According to my invention, I provide a pair of polarized track relays at each end of each-track section selectively responsive to codes of opposite polarity being transmitted from the-opposite end of the section by code transmitting means which, if a stretch of track is cleared for one direction of traflic, will supply code of one polarity and if the stretch is cleared for the opposite direction, the supplied code will be of the opposite'polarity. Upon the reversal of the polarity of the code being supplied at one endcfthe stretch, means controlled by the track relays cascade the polarity reversal .tothe otherend of thestr-etch whereupon the codebeing suppliedrat the other end of the stretch reverses its polarity. This latter reversal of polarity is cascaded to the first end of the stretch by means also including the track relays. I further provide means for preventing the cascading of the reversal of polarity if the codes being supplied at each end .of each section are not of the same relative polarity. This provides a directionallocking feature.

The control of the direction of traffic overthe stretch and of'the directional locking of traflic in the stretch are 2,843,731 Patented July 15, 1958 both accomplished through the medium of the track circuits and are dependent only upon the polarity of the codes being supplied to the'stretch. Accordingly, no line wires are necessary other than C. T. C. control wires or other manual control wires.

Other objects of my invention will appear herein-after as the characteristic features of construction and mode of operation of my invention are described in detail.

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

Figs. 1A, 1B, 1C and 1D, inclusive, of the accompanying drawings, when placed side 'by .side in consecutive order with Fig. 1A at the left provide a diagrammatic view showing one form of apparatus embodying my invention.

Similar reference characters refer to similar parts in each of the several figures.

Referring llOWltO the drawings, there is shown a stretch of single track made up of rails 1 and 2, and thea'djoining ends of a Western and an eastern passing siding made up of rails 3 and 4 and 5 and .6, respectively. The stretch of single track and the sidings are divided into track sections 2T, 4T, 6AT, 6BT and ST by insulated joints 7 placed in the rails. The rails of the single track stretch that make up section 21 are connected in multiple with the rails of the western passing siding by a wire 8 and the frog arrangement, and the main track rails of section 8T are connected to the rails.;of the eastern passing siding by a wire '9 and the frog arrangement, to provide the usual and well-known shunt fouling protection.

At the western headblock, shown in Fig. 1A, are provided eastbound signals ZRAS and ZRBS and a westbound signal ZLS. Each of the signals maybe of any suitable type, and are here shown as the well-known color light type. Section 2T is provided with a conventional direct current track circuit includinga track battery 2TB and a track relay ZTR. A control lever L1 controls trafiic control relays WFS and EFS, the latter being located at the eastern headblock location. Since the means for controlling the traffic control relays forms no part of my invention, control lever Ll-and the line wires can 'be replaced with a lever at each headblock location or by some form of centralized traffic control.

Coded current .is used to control the wayside signals. The current is coded at difierent code rates according to different traffic conditions. In the three aspect system here shown, code rates of 180 and pulses per minute are employed. When 180 code is supplied to a track circuit, the wayside signals will display a green aspect indicating a clear track and a train is permitted to travel at its maximum permissive speed. When 75 code-issupplied to the track circuit, the wayside signal will display a yellow aspect indicating that caution should be exercised by the engineer and thetrain should proceed at medium speed. When no energy is received by the track relay, the wayside signal will display a red aspect indicatingthat a train approaching the signal should come to astop.

Current for the operation of the apparatus other than the track circuits is provided by suitable sources .of direct current, such .as the batteriesLB shown. Each of the relays operated by coded energy is of the polar biased type, having contacts which are picked up whenand only when current flows through the relay winding in the .direction indicated by the arrow thereon.

In Fig. 1A, a code transmitting relay 2WCTRis supplied with coded .energy from battery LB ,by ,theoperation of coders 75CT and 180CT. Code following track relays 2ETR and ZWVRcontrol the supply of energy to decoding transformers.2ETT and ZWTT, respectively. Connected to a winding of transformer '2ETT is adeco'ding'unit lDU which is of conventional design and will supply suflicient energy to cause a clear control relay ZDR to pick up only when'the decoding unit is being energized at a code rate of 180 pulses per minute. An impulse transformer W2 is also at times energized by a winding of either transformer ZETT or ZWTT, depending upon traffic conditions. The winding of each of the relays 2EHR and ZWVPR is connected to another winding of decoding transformers ZETT and ZWTT, respectively. Energy is supplied to track section 4T by a track battery 4WTF, in response to the operation of the code transmitting relay ZWCTR.

A polar stick relay ZDSR controls in part a polar stick relay ZDSKR. These polar stick relays areof a conventional type Which, after deenergization, maintain their contacts in the position to which they were last operated. These polar stick relays will, upon energization of either winding, operate their contacts in the direction from which the current is flowing. The ZDSKR relay controls a reverse repeater relay ZDSKRPR which is a conventional slow-release neutral relay. -A lever L2 and contacts and 11 of a circuit controller operated by switch 1W control signal control relays ZRAHR and ZRBHR which in turn control an approach locking relay ZRMSR and a time element relay ZTER. Also provided at the western headblock location are in approach relay ZRAR and a signal control relay ZLAHR.

At the intermediate signal location IS, as shown in Fig. 1B, are two signals 4L5 and 40RS. Coders 75CT and 180CT control the supply of energy from battery LB to code transmitting relays 4ECTR and 4WCTR which in turn supply coded energy from track batteries 4ETB and 6AWTB to sections 4T and 6AT, respectively. Code following track relays 4EVR, 4WTR, 4ETR and 4WVR control the supply of energy to decoding transformers 4ETT, 4WTT, 6AETT and 6AWTT, respectively. A winding of each of transformers 4ETT and 4WTT at times supplies coded energy to an impulse transformer 4WWT and a winding of each of transformers 6AETT and 6AWTT at times supplies coded energy to an impulse transformer 4EWT. A winding of transformer 4WTT or a winding of transformer 6AETT, depending upon traffic conditions, supplies coded energy to decoding unit 180DU which controls the supply of energy to a clear control relay 4DR.

Another winding of each of the decoding transformers 4ETT, 4WTT, 6AETT and 6AWTT is connected to a winding of code detecting relays 4EVPR, 4WHR, 4EHR and 4WVPR, respectively. In addition, at the intermediate signal location, there are provided a polar stick relay 4DSR, its normal repeater relay 4DSNPR and its reverse repeater relay 4DSRPR. Relay 4DSR, in cooperation with relays 4DSNPR and 4DSRPR, functions to control the supply of energy being coded by coders 180CT and 75CT to either relay 4ECTR or 4WCTR. Furthermore, relay 4DSR also partially controls signals 4LS and 4R5.

At the cut section location CS, shown in Fig. 1C, code transmitting relays CECTR and CWCTR code the energy supplied from track batteries 6AETB and 6BWTB, respectively, to sections 6AT and 6BT, respectively. Codefollowing track relays CEVR, CWTR, CETR and CWVR control the supply of energy from battery LE to decoding transformers AETT, AWTT, BETT and BWTT, respectively. A winding of each of transformers AETT and AWTT at times supplies energy to an impulse transformer CWWT and a winding of each of transformers BETT and BWTT at times supplies energy to an impulse transformer CEWT, depending upon trafiic conditions. Another winding of each of transformers AETT, AWTT, BETT and BWTT is connected to a winding of each of code detecting relays CEVPR, CWHR, CEHR and CWVPR, respectively. A polar stick relay CDSR controls the operation of a normal repeater relay CDSNPR and a reverse repeater relay CDSRPR.

At the eastern headblock, shown in Fig. 1D, track sec- 4 tion ST is provided with a conventional direct current neutral track circuit including a track battery 8TB and a track relay STR. A code transmitting relay 6ECTR is supplied with coded energy from either coder 75CT or coder 180CT, depending upon traffic conditions. Relay 6ECTR codes energy supplied from a track battery 6BETB to section 6BT, Code following track relays 6EVR and 6WTR govern the supply of energy from battery LB to decoding transformers 6ETT and 6W l'l respectively. Decoding unit 180DU is connected to a winding of transformer 6WTT and the decoding unit in turn controls relay 6DR. A separate winding of transformer 6ETT or 6WTT at times supplies energy to an impulse transformer E6, depending upon trafiic conditions. A winding of transformer 6ETT at time supplies energy to a code detecting relay 6EVPR and a winding of transformer 6WTT at times supplies energy to a code detecting relay 6WHR.

Also provided at the eastern headblock are two polar stick relays 6DSR and 6DSKR and a slow release normal repeater relay 6DSKNPR. A control lever L6 and contacts 12 and 13 of a circuit controller operated by switch 5W control signal control relays 6LAHR and 6LBHR which in turn control signals 6LAS and 6LBS, respectively. An approach relay 6LAR and the signal control relays 6LAHR and 6LBHR control an approach locking relay 6LMSR, and all of these relays control a time element relay 6TER. A signal control relay 6RAHR controls a signal 6RS.

Before proceeding with a detailed description of the operation of the system, it is desirable to define several terms which will be used extensively in the following description. Normal codes, as herein used, are codes transmitted in a direction opposite to the established direction of tralfic. tion to normal code. Codes of normal polarity are codes which energize rail 1 positively and rail 2 negatively. Codes of reverse polarity energize the rails 1 and 2 opposite to codes of normal polarity.

As shown, the system is set up for a westbound traffic movement. Lever L1 is in its W position thereby energizing relay WFS over an obvious circuit and deenergizing relay EFS. The contacts of levers L2 and L6 are open, to hold signals ZRAS, ZRBS, 6LAS and 6LBS at stop. I

At the western headblock location coders CT and 75CT are both continually energized by an obvious circuit and each is operating its contact at the corresponding code rates of 180 operations per minute and 75 operations per minute, respectively. Signal control relay ZLAHR is controlled by a circuit which is not shown as it forms no part of my invention. For the purposes of this description, it will suflice to say that relay ZLAHR is energized unless signal 2LS displays its stop or red aspect. As shown, signal 2LS is at stop and relay 2LAHR is therefore deenergized.

The polar stick relays 2DSR and ZDSKR are both in their normal or left-hand position for reasons which will become clear as this description progresses. With relay ZDSKR in its normal or left-hand position, reverse repeater relay 2DSKRPR will be released since its energizing circuit is open at reverse contact b of relay ZDSKR. Accordingly, energy will be supplied to the winding of code transmitting relay ZWCTR at a 75 code rate over a circuit which may be traced from positive terminal B of battery LB, over contact a of coder 75CT which is operating at a code rate of 75 operations per minute, back contact a of relay ZLAHR, back contact a of relay ZDSKRPR, and the winding of relay ZWCTR to negative terminal N of battery LB. Therefore, relay 2WCTR will be operating its contact a at a 75 code rate.

With relay ZWCTR so operating, energy will be supplied to track section 4T from track battery 4WTB at a 75 code rate over a circuit which may be'traced from Feed-back code flows in the opposite directhe positive .terminal of track battery ,4WTB,over.the normal contact d of relay ZDSKR, normal contactb of relay ZDRS, front contact a of relay ZWCTR which is operating at a 75 code rate, to the rail 1, and from the rail 2 to the center tap of track battery 4WTB which is negative with respect to rail 1.

At the intermediate signal location IS, with code transmitting relay 4ECTR released, current will flow from rail 1, over back contact a of relay 4ECTR, the windings of relays 4EVR and 4WTR in series, and back to rail 2. With relays 4EVR and 4WTR connected in the manner shown in Fig. 1B, relay 4WTR will pick up on each code impulse and relay 4EVR will remain continuously released.

When relay 4WTR operates its contacts, energy from battery LB will flow through the primary winding P of decoding transformer 4WTT over an obvious circuit governed by contact a of relay 4WTR. ,Due to transformer action in transformer 4WTT, a voltage will be induced in secondary windings S1 and S2 of transformer 4WTT. The resulting energy in winding S2 is mechanically rectified by contact b of relay 4WTR and supplied to the winding of relay 4WHR, so that relay 4WHR will become energized and will pick up. Relay 4WHR is sufficiently slow in releasing its contacts to cause it to remain picked up during the short intervals between code pulses during which no energy is supplied to its windingfrom the transformer 4WTT.

When relay 4WHR picks up, the voltage induced in winding Slwill be applied toprimary winding P of impulse transformer 4WWT over a circuit which includes front contact a of relay 4WHR. The voltage across the winding P of transformer 4WWT will induce a voltage across the secondary winding S of transformer 4WWT and current will flow through a circuit including normal contact 0 of relay 4DSR in multiple with front contact b of relay 4DSNPR, these contacts being closed for reasons which will be made clear subsequently, the winding of relay 4ECTR and negative terminal N of battery LB. The parts are proportioned and arranged and the polarity is such that the energy supplied to the winding of relay' 4ECTR is efiective to pick up the contacts of relay 4ECTR only upon the release of the contacts of relay 4WTR. Accordingly, relay 4ECTR will pick up momentarily each time that relay 4WTR releases and thereby connect trackbattery 4ETB to the rails 1 and 2 over a circuit which may be traced from the positive terminal of track battery 4ETB, over front contact 12 of relay 4WVPR which is energized for reasons which will be made clear presently, front contact a of relay 4ECTR to the rail 1, and from the rail 2 to the center tap of battery 4ETB which is negative with respect to rail 1. The purpose of this reverse or feed-back energization will be made clear as the description proceeds.

From the foregoing it will be seen that, at this time, relay 4WHR will remain picked up and relay 4ECTR will operate at a code rate equal to the code rate at which relay ZWCTR is operating, that is 75 operations per minute, to supply feed-back code energy to section 4T.

The feed-back code energy which relay 4ECTR transmits to section 4T will be received at the western headblock location during the off or released time of relay ZWCTR. Accordingly, current will flow from rail 1, over back contact a of relay ZWCTR, and through the windings of relays ZWVR and 2ETR, in series, to the rail 2. Relays 2WVR and ZETR are so connected that with current flowing through them in the manner just described, relay ZWVR will operate and relay ZETR will remain released. It is apparent that each time a pulse is received, relay 2WVR will pick up and thereafter release and, therefore, operate at the same code rate as the code transmitting relay 4ECTR is located IS, that is, 75 operations per minute.

With relay ZWVRso operating, current pulses .will be supplied from battery LE to winding P of transformer 2WTT 75 times per minute over contact a of relay ZWVR. By transformer action, a voltage will be induced in winding S2 of transformer 2WTT each time a pulse of energy is supplied to Winding P of transformer ZWTT and this voltage is mechanicallyrectified by contact b ofrelay 2WVR thereby causing relay ZWVPR to pick up and remain picked up as long as relay ZWVR continues to operate. With relay 2ETR continuously deenergized, relay ZEHR will be deenergized.

With relay ZWVPR picked up, the .upper winding of relay ZDSKR will be energized so that its contacts will remain, or be operatedto their-normal position by a circuit which may be traced from positive terminal B of battery LB, over front contact b of relay WFS, front contact b of relay ZWVPR, and the upper winding of relay ZDSKR tonegative terminal N of battery LB.

The energizing circuits for signal control relays ZRAHR and ZRBHR, which will be described in detail subsequently, are both open and relays ZRAHR and ZRBHR are both released. Thecontrol circuit for approach relay 2RAR is not shown as it forms no part of my invention. Suffice it to say that relay ZRAR is energized unless an eastbound train is approaching signal 2RAS. With the track stretch in approach to signal 2RAS unoccupied, as will be assumed at this time, relay 2RAR isenergized. Therefore, approach locking relay ZRMSRis energized by a circuit which can be traced from the positive terminal B of battery LB, over back contact a of relay ZRAHR, back contact a of relay ZRBHR, front contacta of relay ZRAR, and the winding of relay ZRMSR tonegative terminal N of battery LB. Accordingly, the upper winding of relay 2DSR will be energized so thatits contacts will remain, or be operated to their normal position by a circuit which may be traced from the positive terminal B of battery LB, over front contact b of relay ZRMSR, front contact a of relay WFS, front contact a of relay ZTR, normal contact a of relay ZDSKR, and the upper winding of relay 2DSR to negative terminal N of battery LB.

Assuming that switch 1W is in its normal position, as shown, so that traflic will move directly along the main line and not out of or into the passing siding including rails 3 and 4, the switch circuit controller associated with switch 1W will have its contact 10 open and contact 11- closed. It will be seen that signal control relay ZRAHR when energized is energized over a circuit which may be traced from the positive terminal B of battery LB, over the contact of lever L2, reversecontact c of relay ZDSKR, front contact b of relay 2TR, front contact 0 of relay ZEHR, contact 11, and the winding of relayZRAHR to the negative terminal N of battery LB. It will further be seen that signal control relay ZRBHR, when energized, will be energized over a circuit which may be traced from positive terminal B of battery LB, over the contact of lever L2, reverse contacts of relay ZDSKR, front contact b of relay 2TR, front contact 0 of relay ZEHR, contact 10 of the circuit controller associated with switch 1W, and the winding of relay ZRBHR to the negative terminal N of battery LB. However, due to the fact that relay 2DSKR is in its normal position, relay ZEHR is released, and the contact of lever L2 is open, neither of these signal control relays will be picked up. With signal control relays both released, both signals ZRAS and ZRBS will display red aspects because o'fthe energization of their red lamps R by obvious circuits.

Considering now the apparatus at the intermediate signal location IS, for reasons which will 'be made clear presently, relay 4WVPR is energized. With this condition existing, polar stick relay 4DSR will be energized with its contacts in their normal-or left-hand position by a circuit which may be traced from the positive terminal -B of the battery LB, over front contact a of relay 4WVPR, frontcontact b of relay 4WHR, and the upper winding of relay 4DSR to the'negative terminal N of battery 13B.

With relay 4DSR so energized, normal repeater relay 4DSNPR will be energized by an obvious circuit including normal contact a of relay 4DSR.

Coders 75CT and 180CT are energized in multiple by an obvious circuit so that each of their front contacts a will be operating at a 75 code rate and 180 code rate, respectively. With relay 4WHR picked up, 180 code will be supplied to code transmitting relay 4WCTR over a circuit which may be traced from the positive terminal B of battery LB, over front contact a of coder 180CT which is operating at 180 times per minute, front contact c of relay 4WHR, back contact a of relay 4DSRPR, normal contact b of relay 4DSR, and the winding of relay 4WCTR to the negative terminal N of battery LB. Accordingly, code transmitting relay 4WCTR will operate its contact at a code rate of 180 pulses per minute. With code transmitting relay 4WCTR so operating, l80 code will be supplied to section 6AT from track battery 6AWT B over a circuit which may be traced from the positive terminal of battery 6AWTB, over front contact d of relay 4WHR and back contact b of relay 4EVPR in multiple, front contact a of relay 4WCTR, to the rail 1, and from rail 2 to the center tap of battery 6AWTB which is negative with respect to rail 1.

At the cut section location CS, Fig. 1C, as the coded energy from track battery 6AWTB is received, with relay CECTR released, current will flow from rail 1, over back contact a of relay CECTR, through the winding of relays CEVR and CWTR, in series, to rail 2, so that with relays CEVR and CWTR connected as shown, relay CWTR will operate its contacts and relay CEVR will remain continuously released. As relay CWTR operates, energy will be supplied from battery LB to the primary winding P of transformer AWTT, over contact a of relay CWT R and this energy will cause a voltage to be induced in secondary windings S1 and S2 of transformer AWTT. With winding S2 of transformer AWT T so energized, current will flow through the winding of relay CWHR over the rectifying contact b of relay CWTR causing relay CWHR to pick up. With relay CWHR picked up, current will flow from the winding S1 of transformer AWTT through the Winding P of impulse transformer CWWT, thereby inducing a voltage in winding S of transformer CWWT. With relay CDSR energized to its normal or left-hand position for reasons which will become clear presently, and relay CDSNPR picked up by an obvious circuit, current will flow from the secondary winding S of transformer CWWT, over front contact a of relay CDSNPR and normal contact b of relay CDSR in multiple, and through the winding of relay CECTR to the negative terminal N and thence to the other terminal of winding S of transformer CWWT. The parts are proportioned and arranged and the polarity is such that, at this time, relay CECTR will be picked up momentarily upon each release of the contacts of relay CWTR.

With relay CECTR so operating feed-back code energy will be transmitted to the rails 1 and 2 from track battery GAETB over a circuit which may be traced from the positive terminal of battery 6AETB, over front contact b of relay CWVPR which is energized for reasons which will be made clear hereafter, front contact a of relay CECTR which is operating at a 180 code rate, to the rail 1, and from the rail 2 to the center tap of the track battery 6AETB which is negative with respect to rail 1.

Referring now to Fig. 1B, with relay 4WCTR released and rail 1 of section 6A1 positively energized and rail 2 energized negatively by feed-back energy from location CS, current will flow from rail 1, over back contact a of relay 4WCTR and the windings of relays 4WVR and 4ETR to rail 2. With relays 4ETR and 4WVR connected in the manner shown in Fig. 1B, relay 4WVR will operate at a 180 code rate and relay 4ETR will remain released. In the same manner as described for relays 4 WTR and 4WHR, this codefollowing operation of 8 relay 4WVR will cause the code detecting relay 4WVPR to be energized.

The circuits controlling the signals 4RS and 4LS will be described in some detail subsequently. For the present it will be pointed out that none of the lamps of signal 4RS is energized because the common return for all of the lamps of this signal to the negative terminal N of battery LB is open at back contact 1 of relay 4WHR and none of the lamps of signal 4LS is energized because the common return for all of the lamps of this signal to the negative terminal N of battery LB is open at back contact c of relay 4WVPR.

At the cut section location CS, Fig. 1C, code transmitting relay CWCTR will be energized at a code rate by a circuit which may be traced from positive terminal B of battery LB, over front contact 0 of relay CWTR which is operating at 21.180 code rate, back contact a of relay CDSRPR, normal contact c of relay CDSR, and the winding of relay CWCTR to the negative terminal N of battery LB. With code transmitting relay CWCTR so operating, energy will be supplied to section 6BT from track battery 6BWTB at a 180 code rate over a circuit which may be traced from the positive terminal of track battery 6BWTB, over front contact c of relay CWHR and back contact b of relay CEVPR in multiple,

and front contact a of relay CWCTR which is operatingat a 180 code rate to rail 1, and from rail 2 to the center tap of track battery 6BWTB which is negative with respect to rail 1.

With rail 1 energized with energy of positive polarity and rail .2 with energy of negative polarity, in a manner similar to that already described with relation to track section 4T, relay 6WTR, Fig. ID, will operate at a 180 code rate and relay 6EVR will remain released continuously at this time. Accordingly, relay 6WHR will pick up and the primary winding P of impulse transformer E6 will be energized 180 times per minute. Code transmitting relay 6ECTR will operate at a 180 code rate over a circuit which may be traced from the lower terminal of the secondary winding S of impulse transformer E6, over front contact a of relay 6DSKNPR which is energized in a manner to be described presently and the winding of relay 6ECTR to negative terminal N of battery LB and the upper terminal of transformer E6. -With relay 6ECTR so operating, feed-back code energy will be supplied to the rails 1 and 2 from battery 6BETB over a circuit which may be traced from the positive terminal of track battery 6BETB, over front contact 0 of relay 6LMSR which is energized in a manner to be made clear subsequently, front contact d of track relay 8TR, normal contact b of relay 6DSR which is energized to its normal position by a circuit which will be traced presently, front contact a of relay 6ECTR which is operating at a 180 code rate to rail 1, and from rail 2 to the center tap of battery 6BET B which is negative with respect to rail 1.

When section 6BT is energized with feed-back code energy, relay CWCTR, Fig. 1C, will be released and current will flow from rail 1, over back contact a of relay CWCTR, through the winding of relay CWVR, and the winding of relay CETR to the rail 2. With relays CETR and CWVR connected as shown in Fig. 1C, relay CWVR will operate and relay CETR will remain continuously released. Each time a feed-back pulse is transmitted to section 6BT, relay CWVR will pick up so that it will operate at the code rate of relay 6ECTR, that is, 180 operations per minute.

The code following action of relay CWVR is detected in a manner similar to that previously explained for the other code following track relays, by action of the decoding transformer BWTT and relay CWVPR. Accordingly, relay CWVPR will be picked up at this time.

With relay CWVPR picked up, the upper winding of relay CDSR becomes energized so that its contacts assume their normal or left-hand position by a circuit which runs from the positive terminal B of battery LB, over 9 front contact a of relay CWVPR, front contact b of relay CWHR, and the upper winding of relay CDSR .to the negative terminal N of battery LB.

.As was stated earlier, the DS and DSK relays herein employed are of the polar stick type, that is, the contacts will remain in the position to which they were last energized until energy of opposite polarity is applied to the relay to move the contacts to their opposite position. Consequently, the contacts of relay 6DSR, Fig. 1D, will be found in their normal position although at the present time neither winding is energized. Relay 6DSKR will be energized to its normal or left-hand position over a circuit which may be traced from the positive terminal B of battery LB, over back contact b of relay EFS, front contact b of relay 6WHR, normal contact \a of relay 6DSR, and the upper winding of relay 6DSKR to the negative terminal N of battery LB. At this time, normal repeater relay 6DSKNPR will be energized by an obvious circuit including normal contact b of relay 6DSKR.

Assuming switch 5W is in its normal position so that traffic will move directly along the main line and not into or out of the passing siding including the rails 5 and 6, the switch circuit controller associated with switch 5W will have its contact 12 open and its contact '13 closed. It will be seen that signal control relay 6LAHR, when energized, is energized over a circuit which may be traced from positive terminal B of battery LB, over the contact of lever L6, normal contact c of relay 6DSKR, front contact b of relay 8TR, front contact a of relay 6WHR, contact 13 of the switch circuit controller, and the winding of relay 6LAHR to negative terminal N of battery LB. It will be further seen that the signal control relay GLBHR, when energized, is energized over a circuit which may be traced from positive terminal B of battery LB, over the contact of lever L6, normal contact c of relay 6DSKR, front contact b of relay 8TR, front contact c of relay 6WHR, switch circuit controller contact 12, and the winding of realy GLBHR to negative terminal N of battery LB. However, due to the fact that lever L6 is in its normal or open position, both energizingcircuits will be open at the contact of lever L6 and both signal control relays 6LAHR and -6LBHR will be released. With thesignal control relays both released, bothsignals 6LAS and 6L BS will display red aspects due to the energization of their red lamps R by obvious circuits.

Decoding unit 180DU is connected to the terminals of winding P of transformer 6WTT which is being energized at a 180 code rate. Accordingly, energy is supplied to the decoding unit at a code rate of 180 and at this code rate sufiicient energy will be supplied to the winding of relay 6DR to cause it to pick up. However, with relays 6LAHR and 6LBHR both released, the fact that relay 6DR is picked up will have no effect upon the aspects displayed by signals 6LAS and 6LBS at this time.

Having described the circuit arrangement in its normal condition, that is, set up for trafiic moving in the normal westbound direction, it will now be assumed that a train approaches the track stretch from the east. As the train approaches section 8T, signal ZLS, by means not shown, will be cleared .to a green or clear aspect, and relay ZLAHR will pick up, transferring the control circuit for code transmitting relay ZWCTR from the 75 coder to the 180 coder. Accordingly, section 4T will become energized with normal and feed-back codes of normal polarity at a 180 code rate, so that relay 4DR, Fig. 1B, becomes picked up at this time. The remainder of the system will continue to operate as described above. Also, a leverman at the eastern headblock or the operator of the centralized traffic control equipment will close lever L6, Fig. 1D. With the contact of lever L6 closed, relay 6LAHR will pick up because its previously traced energizing circuit will now be closed. Of course, if the train were to approach .on the eastern passing siding, including rails 5 and 6, then switch SW would be thrown 10 by the. operator t o.its reverse position and relay 6LBHR would pick up rather than relay 6LAHR.

With relay 6LAHR picked up, the green lamp G of signal 6LAS will be lighted due to energization by the circuit which may be traced from positive terminal B of battery LB, over front contact b of relay 6LAHR, front contact a of relay 6DR, and the green lamp G to negative terminal N of battery 'LB. With relay 6LAHR picked up, relay 6LMSR will release. Upon the release of relay 6LMSR, the polarity .of the coded feed-back energy being transmitted by code transmitting relay 6ECTR will be reversed .and the rails 1 and 2 will now be energized by a circuit which maybe traced from the negativeterminal of battery 6BETB, over back contact 0 of relay 6LMSR, front contact a of relay 8TR, normal contact b of relay 6DSR, front contact a of relay 6ECTR which is operating at a 180 code rate to the rail 1, and from the rail 2 to the center tap of battery 6BETB which is positive with respect to rail 1. At the cut section CS, in a manner similar to that described for the feed-back code of normal polarity, relay CETR will commence operating at a 180 code rate and relay CWVR will release and stay released. Accordingly relay CEHR will pick up and relay CWVPR will release. With relay CWV PR 'nowreleased, the upper winding of relay CDSR will become deenergized but, because of the stick characteristic of the CDSR relay, the contacts of relay CDSR will remain in their normal position. Furthermore, with relay CEHR now picked up and relay CWVPR released, the feed-back code transmitted by code transmitting -relay CECTR will be of reverse polarity and will be transmitted-to the rails 1 and 2 of section 6AT by a circuit which may be traced from the negative terminal of track battery 6AETB, over back contact b of relay CW-VP-R and front contact 0 of relay CEHR in multiple, front contact a of relay CECTR which is operating at a 180 code rate to the rail 1, and from the rail 2 to the center tap of battery 6AETB which is positive with respect to rail 1.

With feed-back code being applied to track section 6AT with reverse polarity, in a manner similar to that described with respect to section 6BT, relay 4ET R, Fig. 13, will commence operating at a 180 code rate and relay 4WVR will cease operating. Therefore, relay 4EHR will pick up and relay 4WVPR will release. Upon the release of relay 4WVPR, the upper winding of relay 4DSR will become deenergized, but the contacts of relay 4DSR will remain in their normal position due to the stick characteristic of the relay.

Upon the release of relay 4WVPR and the picking up of relay 4EHR, the feed-back code being transmitted to section 4T by code transmitting relay 4ECTR will be of opposite polarity to that transmitted when the circuit is operating under normal conditions. The circuit which will now supply energy from battery 4ETB to the rails 1 and 2 in section 4T may be traced from the negative terminal of battery .4ETB, over front contact d of relay 4EHR and back contact b of relay 4WVPR in multiple, front'contacta of zrelay'4ECTR which is now operating at a 180 code rate to the rail 1, and from the rail 2 to the center tap of battery 4ETB which is positive with respect to rail 1.

:With the feed-back code energy supplied to section 4T .being of negative polarity, relay ZETR, Fig. 1A, willcommence operating and relay ZEHR will pick up, and [relays .2WVR and ZWVPR will release. This will cause the upper winding of relay ZDSKR to become deenergized but the contacts of relay ZDSKR will remain in. their normal position due to the stick characteristic of .relay ZDSKR. This will prevent traffic from entering the stretch from the western headblock in the reversedirection, for reasons which will become apparent as this description progresses.

-As the train enters section 8T, its wheels and axles shunt track relay w8TR causing it to release, thereby opening the energizing circuit for signal control relay 6LAHR at contact b of relay 8TR, and causing the control relay 6LAHR to release. Upon the release of the relay 6LAHR, signal 6LAS will display a red aspect due to the energization of the red lamp R of signal 6LAS by a circuit which may be traced from the positive terminal B of battery LB, over back contact b of relay 6LAHR and the red lamp R to the negative terminal N of battery LB.

The release of relays 6LAHR and 8TR also establishes a circuit, including back contact a of relay 6LAHR and back contact c of relay 8TR, for reenergizing approach locking relay GLMSR, which then sticks over back contacts a of the signal control relays. However, feed-back code being transmitted from the eastern headblock location will continue to be of reverse polarity since, with relay 8TR released, rails 1 and 2 will be energized by a circuit which may be traced from the negative terminal of battery 6BETB, over back contact d of relay 8TR, normal contact b of relay 6DSR, front contact a of relay GECTR operating at a 180 code rate, to the rail 1, and from the rail 2 to the center tap of battery 6BETB which is positive with respect to rail 1. Accordingly, all of the feed-back energy being transmitted to the stretch will be of reverse polarity.

Upon the train entering section 6BT but having not yet vacated section 8T, the wheels and axles of the train will shunt relays 6EVR and 6WTR causing them to remain released. Accordingly, relay 6WHR will also release because it is now receiving no energy from the winding S2 of transformer 6WTT. Upon the release of relay 6WHR, the energizing circuit for signal control relay 6LAHR will become open at front contact of relay 6WHR as well as front contact b of track relay 8TR. The release of relay 6WHR will also open the energizing circuit for the upper winding of relay 6DSKR at front contact b of relay 6WHR. However, due to the stick characteristic of relay GDSKR, its contacts will remain in their normal or left-hand position.

Upon the release of relays 6WTR and 6WHR, no code impulses will be supplied to winding P of transformer E6 and, therefore, no energy will be supplied to code transmitting relay 6ECTR and it will cease to operate. Accordingly, because of the train shunt and also because of the cut-off of the feed-back code, no feed-back code will be received at the cut section location CS and relay CETR and its associated code detecting relay CEHR will both release. However, although front contact 0 of relay CEHR is now open, back contact b of relay CWVPR will be closed and feed-back code of negative polarity will continue to be supplied to section 6AT. In a similar manner to that already described, feedback of negative polarity will be supplied to all the other sections in the stretch and traffic will remain locked in the westbound direction.

Upon the train vacating section 8T, relay 8TR will pick up. This has no immediate effect upon the circuit arrangement but as this description proceeds it will become clear why the picking up of relay 8TR is useful.

Upon the train vacating section 6BT and occupying section 6AT, relay CWTR will become released due to the fact that it is shunted by the wheels and axles of the train. Therefore, no coded energy will be supplied from battery LB to code transmitting relay CWCTR and as a result relays 6WTR and 6WHR at the eastern headblock will remain released. Therefore, no feed-back energy will be supplied from battery 6BETB to section 6BT and relays CWVR, CETR, CEHR and CWVPR will remain released. With relay 6WHR remaining reno feed-back code will be transmitted by relay CECTR to section 6AT.

Upon the release of relay 4ETR, due to the train shunt in section 6AT, relay 4EHR will also release, opening its front contact d. However, because back contact b of relay 4WVPR is still closed, feed-back energy of reverse polarity will continue to be transmitted by relay 4ECTR to section 4T in a manner already described. Upon the release of relay 4EHR, energy will be supplied to the green lamp G of signal 4LS over a circuit which may be traced from the positive terminal B of battery LB, over normal contact d of relay 4DSR, front contact e of relay 4WHR, front contact a of relay 4DR, the green lamp G of signal 4LS, back contact 1 of relay 4EHR, and back contact c of relay 4WVPR to negative terminal N of battery LB. It should be noted that until the train entered section 6AT, signal 4LS was not illuminated because the lighting circuit was open, initially at the back contact 0 of relay 4WVPR and later, after the change in polarity of the feed-back code, at back contact 1 of relay 4EHR. This approach lighting feature is particularly desirable whenever battery conservation is important. However, my invention is not limited to the use of approach lighting and my apparatus will operate just as well where continuous lighting of the wayside signals is employed.

Clear control relay 4DR was previously described as supplied with energy from decoding unit DU which is of conventional design and well-known in the art of coded railway signaling. Each decoding unit 180DU will supply suflicient energy to its clear control relay when and only when the decoding unit is energized at a 180 code rate. The decoding unit supplying energy to relay 4DR will be energized at a 180 code rate and therefore will be able to supply sufiicient energy to keep relay 4DR picked up. The circuit which energizes the decoding unit may be traced from the upper terminal of winding P of transformer 4WTT over back contact 0 of relay 4DSRPR, the decoding unit 180DU, front contact 0 of relay 4DSNPR and to the lower terminal of winding P of transformer 4WTT. The coded feedback energy being transmitted by relay 4ECTR continues to be of reverse polarity as the rails 1 and 2 in section 4T continue to be energized by battery 4ETB over a circuit which has already been traced.

When the train vacates section 6AT and occupies section 4T, its wheels and axles will shunt relays 4WTR and ZETR causing them to release and thereby causing relays 4WHR and ZEHR to release. Accordingly, no energy impulses will be supplied to winding P of transformer 4WWT and, therefore, code transmitting relay 4ECTR will cease to transmit feed-back energy to section 4T. Red lamp R of signal 4L3 will now be energized by a circuit which may be traced from positive terminal B of battery LB, over normal contact d of relay 4DSR, back contact e of relay 4WHR, the red lamp R of signal 4L5, back contact 1 of relay 4EHR, and back contact 0 of relay 4WHR to negative terminal N of battery LB.

With relay 4WHR nowv released, energy at a 75 code rate will be supplied from battery LB to code transmitting relay 4WCTR over a circuit which may be traced from positive terminal B of battery LB, over front contact a of coder 75CT which is operating at a 75 code rate, back contact c of relay 4WHR, back contact a of relay 4DSRPR, normal contact b of relay 4DSR, and the winding of relay 4WCTR to negative terminal N of battery LB. Code transmitting relay 4WCTR will therefore transmit 75 code energy from battery GAWTB to the rails 1 and 2 of section 6AT of normal polarity over a circuit which may be traced from the positive terminal of battery 6AWTB, over back contact b of relay 4EVPR, front contact a-of relay 4WCTR which is operating at a 75 code rate to the rail 1, and from the rail 2 to the center tap of battery 6AW'FB which is negative with respect to rail 1. At the cut section location, operation of relay CWTR at a 75 code rate will occur, and accordingly the winding P of transformer AWTI will be supplied with energy at a 75 code rate and energy from winding S1 of transformer AWTI will be supplied to winding P of transformer CWWI at the same code rate. In this manner energy will be supplied from winding S of transfonmer OWWT to code transmitting relay CECTR which will transmit feed-back code to the intermediate signal location IS. The first few pulses of this feed-back code will be of reverse polarity due to the fact that relay OWVPR is initially in a deenergized condition. Current thus flows from the negative terminal of battery 6AETB over back contact b of relay CWVP-R and front contact a of relay CECTR to rail 1, and from rail 2 to the center tap of the battery, which is positive with respect to rail 1. However, the feed-back code shortly changes to normal polarity when relay CWVPR picks up, in the manner described shortly, permitting the current to flow from the positive terminal of battery 6AETB, over front contact b of relay OWVPR, front contact a of relay CECTR, operating at a 75 code rate, to the rail 1, and from the rail 2 to the center tap of battery '6ATB which is negative with respect to rail 1.

With relay CWTR operating at a 75 code rate, energy will be supplied to code transmitting relay CWCTR at the same code rate over a circuit which has already been traced. In a manner substantially similar to that described with relation to the circuits in their normal condition, relay 6WTR will commence operating at a 75 code rate and relay 6WHR Will pick up. Furthermore, relay 6ECTR will transmit feed-back energy of normal polarity to the cut section location which will cause relay CWVR to commence operating and relay OWVPR to pick up. With transformer 6WTT now being supplied with energy at a 75 code rate, code detecting unit 180DU will not supply sufficient energy to pick up clear control relay -6DR and it will therefore remain released. Accordingly, signal 6LA-S, if recleared for a following train at this time, can only display a yellow aspect, the yellow lamp Y being energized by a circuit which may be traced from position terminal B of battery LB, over from contact b of relay 6LAHR, back contact a of relay 6'DR, the yellow lamp Y of signal GLAS to negative terminal N of battery LB. At this time, the circuit previously traced for the red lamp of signal 4LS is interrupted, either at back contact f of relay 4'EHR or at back contact c of relay 4WVPR, and the signal becomes dark.

When the train vacates section 4T and occupies section 2T, assuming that signal 6LAS was not recleared (lever L6 in-open position), relay ZLAHR will release due to thefact that signal 'ZLS, which is controlled by circuits which are not shown, will now display red. Energy at the 75 code rate will be supplied to the Winding of relay 2WCTR by a circuit which may be traced from positive terminal B 'of battery LB, :over contact a of 75CT which is operating at a 75 code rate, back contact a of relay ZLAHR, back contact-a of relay ZDSKRPR, and the winding of relay 2WCTR to 'negativeterniinal N of battery LB. Accordingly, relay ZWCTR will transmit 75 code 'to section 4T by a circuit which maybe traced from the positive terminal -of battery 4WTB, over normal contact d of relay ZDSKR, normal contact 11 of relay .ZDSR, front contact a of relay 2WCTR which is operating at a '15 code rate to the rail 1, and from the rail 2 to center tap of'battery 4WTB which :is negative with respect to rail 1. in a'manner similar to that already described with respect to the normal condition of the circuit arrangement, coded feed-back energy of normal polarity will 'be transmitted by transmitting relay-4ECTR to section 4Ttat a 75 code rate thereby'operating relay 'ZWVR and picking up relay ZWVPR. With relay 4WTR operating and relay 4WI-IRpicked up, 180 code of normal polarity will be transmitted to section 6AT and repeated to section 6BT. Feed-back code of normal polarity but at the code rate will be transmitted by code transmitting relay CECTR to section 6AT, with relay 4WVR operating to hold relay 4WVPR energized. In like manner, normal code and feed-back code, both of normal polarity and of the 180 code rate, will be transmitted by relay CWCTR and relay GECTR, respectively, operating relays 6WTR and CWVR and holding up relays 6WHR and CWV PR.

With the system restored to its normal condition and both normal code and feed-back code being of normal polarity, the direction of traffic may now be reversed by throwing lever L1 to its eastbound position E. This will open the energizing circuit for relay WFS causing it to release and will pick up relay EFS over an obvious circuit including the eastbound contact E of lever L1. Upon relay WFS releasing, the contacts of relay ZDSR will be operated to their reverse or right-hand position due to the lower winding of relay ZDSR becoming energized by a circuit which may be traced from positive terminal B of battery LB, over front contact b of relay ZRMSR, back contact a of relay WFS, front contact a of relay ZWVPR, and the lower winding of relay ZDSR to' negative terminal N of battery LB. With the contacts of relay 2DSR in their reverse position and code transmitting relay ZWCTR operating at a 75 code rate, 75 code of reverse polarity will be transmitted to section 4T over a circuit which may be traced from the negative terminal of battery 4WTB, over front contact 0 of relay ZRMSR, front contact d of relay ZTR, reverse contact b of relay ZD-SR, front contact a of relay ZWCTR which is operating at a 75 code rate, to the rail 1 and from the rail 2 to the center tap of battery 4WTB which is positive with respect to rail 1.

With the normal code on section 4T being of reverse polarity, relay 4EVR will operate and relay 4WTR will remain released. Accordingly, relay 4EVPR will pick up and relay 4WHR will release. This will result in the code transmitted to section 6AT over front contact a of relay 4WCTR being of reverse polarity due to energization of the rails by a-circuit which may be traced from the negative terminal of battery 6AWTB, over front contact b of relay 4EVPR, front contact a of relay 4WCTR operating at a 75 code rate to the rail 1, and from the rail 2 to the center tap of battery 6AWTB which is positive with respect to rail 1. It is to be noted that, with relay 4WHR released, relay 4WCTR is now operating at the 75 code rate, as controlled over a previously traced circuit including contact a of 75CT and back contact 0 of relay 4WHR.

Accordingly, at the cut section, relay CEVR will commence operating, relay CEVPR will pick up, relay CWTR will cease operating and relay CWHR will release. Upon this happening, code of reverse polarity will be supplied to section 6BT from battery 6BWTB by a circuit which may be traced from the negative terminal of battery 6BWTB, over front contact b of relay CEVPR, front contact a of relay CWCTR which is operating at a 75 code rate to the rail 1, and from the rail 2 to the center tap of battery 6BWTB which is positive with respect to rail 1.

The winding of code transmitting relay CWCTR will no longer be supplied with coded energy over front contact b of relay CWTR because this latter relay is no longer operating. However, front contact c of relay CEVR is connected in multiple with front contact 0 of relay CWTR. Therefore, coded energy is supplied through the winding of relay CWCTR over a circuit which may be traced from positive terminal B of battery LB, over front contact 0 of relay CEVR which is operating at a code rate of 75 times per minute, back contact a of relay CDSRPR, normal contact c of relay CDSR, and the winding of relay CWCTR to negative terminal N ofbattery LB.

Accordingly, at the eastern headblock, relay '6EVR 15 will commence operating and relay 6WTR will cease to operate. With relay 6EVR now operating, relay 6EVPR will pick up and with relay 6WTR now not operating, relay 6WHR will release. Therefore, the contacts of relay 6DSKR will be operated to their reverse position due to energization of the lower winding of relay 6DSKR by a circuit which may be traced from positive terminal B of battery LB, over front contact b of relay EFS, front contact b of relay 6EVPR, and the lower winding of relay 6DSKR to negative terminal N of battery LB. Upon relay 6DSKR operating to its reverse position, a circuit will be established to energize the lower winding of relay 6DSR and it too will operate its contacts to their reverse position. This circuit may be traced from positive terminal B of battery LB, over front contact b of relay 6LMSR, front contact a of relay EFS, front contact a of relay STR, reverse contact a of relay 6DSKR, and the lower Winding of relay 6DSR to negative terminal N of battery LB.

When relay GDSKR operates to the reverse position,

the energizing circuit for relay 6DSKNPR will be opened at the normal contact b of relay 6DSKR. However, relay GDSKNPR will not immediately release because of its slow release characteristic, and as long as relay GDSKNPR remains picked up, impulse transformer E6 will continue to supply energy, now at the 75 code rate, to the winding of code transmitting relay 6ECTR over a circuit which may be traced from the lower terminal of winding S of transformer E6, over front contact a of relay SDSKNPR, and the winding of relay 6ECTR to negative terminal N of battery LB which is also connected to the upper terminal of the winding S of transformer E6. The primary winding of transformer E6 is now energized from winding S1 of transformer 6ETT over back contact a of relay 6WHR. However, the feed-back code being transmitted by relay 6ECTR will be of reverse polarity as can be seen from tracing the energizing circuit for the rails 1 and 2 of track section 6BT from the negative terminal of battery 6BETB, over reverse contact d of relay 6DSKR, reverse contact b of relay 6DSR, front contact a of relay 6ECTR which is operating at a 75 code rate to the rail 1, and from the rail 2 to the center tap of battery 6BETB which is positive with respect to rail 1.

Accordingly, at the cut section location CS, relay CETR will commence operating, relay CWVR will cease operating, relay CEHR will pick up and relay CWVPR will release. Upon this occurring the lower winding of relay CDSR will become energized over a circuit which may be traced from the positive terminal B of battery LB, over front contact a of relay CEVPR, front contact b of relay CEHR, and the lower winding of relay CDSR to the negative terminal N of battery LB. Therefore, relay CDSR will operate to its reverse position and in so doing will deenergize slow release relay CDSNPR and energize relay CDSRPR over an obvious circuit including the reverse contact a of relay CDSR.

Upon relay CDSR operating to its reverse position and relay CDSRPR picking up, the circuit which was supplying energy to relay CWCTR is interrupted. This circuit, including contact of relay CEVR operating at a 75 code rate, will become open at contact a of relay CDSRPR and normal contact 0 of relay CDSR. Relay CWCTR releases, opening its front contact a to interrupt the circuit supplying coded energy of reverse polarity from battery 6BWTB to the rails of section 6BT. Accordingly, relays 6EVR and 6EVPR will both release, thereby deenergizing the lower winding of relay 6DSKR. However, this will have no effect as to the position of the contacts of relay GDSKR at the eastern headblock location because of that relays stick characteristic.

As long as relay CDSNPR remains picked up, transformer CWWT will continue to energize code transmitting relay CECTR which will continue to send out feedback code to section GAT. However, this code will now be of reverse polarity because the rails 1 and 2 of section 6AT will be energized by a circuit which may be traced from the negative terminal of battery 6AETB, over front contact 0 of relay CEHR and back contact b of relay CWVPR in multiple, front contact a of relay CECTR which is operating at a 75 code rate to the rail 1, and from the rail 2 to the center tap of battery 6AETB which is positive with respect to rail 1.

Therefore, at the intermediate signal location IS, relay 4ETR will commence operating and relay 4WVR will release resulting in relay 4EHR picking up and relay 4WVPR releasing. Accordingly, the lower winding of relay 4DSR will become energized by a circuit which may be traced from positive terminal B of the battery LB, over front contact a of relay 4EVPR, front contact b of relay 4EHR, and the lower winding of relay 4DSR to negative terminal N of the battery LB. With the lower winding of relay 4DSR so energized the contacts of relay 4DSR will operate to their reverse position and thereby deenergize relay 4DSNPR and energize relay 4DSRPR. Relay 4DSNPR is a slow release relay and as long as it remains picked up, winding S of transformer 4WWT will supply energy to code transmitting relay 4ECTR which will thereby transmit feed-back code to section 4T. The circuit supplying energy from the secondary winding S of transformer 4WWT to relay 4ECTR may be traced from the right-hand terminal of winding S, over front contact b of relay 4DSNPR, and the winding of .relay 4ECTR to the negative terminal N of battery LB which is also connected to the other terminal of winding S of transformer 4WWT. However, this feed-back code being transmitted by relay 4ECTR will be of reverse polarity and will be supplied from battery 4ETB to section 4T over a circuit which may be traced from the negative terminal of battery 4ETB over front contact d of relay 4EHR and back contact b of relay 4WVPR in multiple, front contact a of relay 4ECTR which is operating at a 75 code rate to the rail 1, and from the rail 2 to the center tap of battery 4ETB which is positive with respect to rail 1.

With the feed-back code transmitted by relay 4ECTR being of negative polarity, relay ZETR will commence operating and relay ZWVR will cease operating. Therefore, relay ZEHR will pick up and relay ZWVPR will release. The lower winding of relay ZDSKR will not become energized by a circuit which may be traced from positive terminal B of battery LB, over back contact b of relay WFS, front contact b of relay ZEHR, reverse contact a of relay ZDSR, and the lower winding of relay ZDSKR to negative terminal N of battery LB. Upon relay ZDSKR operating its contacts to their reverse position, relay ZDSKRPR will become energized and open its back contact a to interrupt the circuit supplying energy to relay ZWCTR over contacts of the coders CT and 75CT. The closing of front contact a of relay ZDSKRPR completes a circuit for supplying energy from transformer W2 to relay ZWCTR, which will shortly supply feed-back code to track section 4T.

At the eastern headblock location relay 6DSKNPR eventually releases and closes a circuit, at its back contact a connecting one of the coders, 75CT or 180CT, depending upon traffic conditions, into the circuit arrangement to control the supply of energy to relay 6ECTR. With the stretch of track vacated as it is at this time, and relay GRAHR deenergized, coder 750T will supply energy to code transmitting relay 6ECTR over a circuit which may be traced from positive terminal B of battery LB, over the contact of 75CT which is operating at a 75 code rate, back contact a of relay 6RAHR, back contact a of relay 6DSKNPR, now released, and the winding of relay 6ECTR to negative terminal N of battery LB. Relay 6ECTR will now control normal code supplied from battery 6BETB to the track section 6BT, which code will be of reverse polarity, the rails being energized by a circuit which has already been traced in connection with feed-back code of reverse polarity previously transmitted by relay 6ECTR.

Accordingly, at the cut section location CS, relay CETR will remain operating and relay CEHR will remain picked up, and relays CWVR and CWVPR will remain released. Relay CDSNPR which became dc.- energized but remained picked up due to its slow release characteristic eventually releases. Energy Will besupplied to the winding P of impulse transformer CEWT by winding S1 of transformer BETT in a manner similar to that described with respect to other impulse transformers. The secondary winding S of transformer CEWT will supply energy to code transmitting relay CWCTR over a circuit which may be traced from the left-hand terminal of winding S of transformer CEWT, over front contact b of relay CDSRPR, and the winding of relay CWCTR to the negative terminal N of battery LB which is connected also to the right-hand terminal of winding S of transformer CEWT. The feedback code being transmitted by relay CWCTR will be of the same frequency as the code being transmitted from the eastern headblock location, that is, 75 impulses per minute. This feed-back code will be of reverse polarity which is supplied from battery GBWTB to section 6BT by a circuit which may be traced from the negative terminal of battery 6BWTB, over front contact b of relay CEVPR, front contact a of relay CWCTR which is operating at 75 code rate to the rail 1, and from the rail 2 to the center tap of battery 6BWTB which will be positive with respect to rail 1. This feed-back code of reverse polarity will cause relay 6EVR to commence operating and relay 6EVPR to pick up thereby reestablishing the energizing circuit for the lower winding of relay GDSKR.

Furthermore, at the cut section location CS, with relay CETR operating at a 75 code rate, energy will be supplied from battery LB to code transmitting relay CECTR at the same code rate over a circuit which may be traced from positive terminal B of battery LB, over front contact of relay CETR operating at a 75 code rate, back contact b of relay CDSNPR, reverse contact b of relay CDSR, and the winding of relay CECTR to negative terminal N of battery LB. Accordingly, energy of reverse polarity will be supplied, to section 6AT from the battery 6AETB by a circuit which may be traced from the negative terminal of battery 6AETB, over front contact c of relay CEHR and back contact b of relay CWVPR in multiple, front contact a of relay CECTR which is operating at a 75 code rate to the rail 1, and from the rail 2 to the center tap of battery 6AETB which is positive with respect to rail 1.

At the intermediate signal location IS, the code being transmitted by the code transmitting relay CECTR will keep relay 4ETR operating which in turn will cause relay 4EHR to remain picked up and relay 4WVR and relay 4WVPR to remain released. With the contacts of relay 4DSR now operated to their reverse positions, impulse transformer 4EWT will supply coded energy to the wind ing of relay 4WCTR over a circuit which may be traced from the left-hand terminal of the winding S of transformer 4EWT, over front contact b of relay 4DSRPR and reverse contact b of relay 4DSR in multiple, and the winding of relay 4WCTR to the negative terminal N of battery LB which is also connected to the right-hand terminal of the winding 8 of transformer 4EWT. The primary winding P of transformer 4EWT will be supplied with energy from the winding S1 of transformer 6AETT in a manner similar to that already described with respect to the energization of other impulse transformers. However, the feed-back code being transmitted by relay 4WCTR will be of reverse polarity because the rails of section 6AT will be energized from battery 6AWTB over a circuit which has already been traced with respect to supplying normal code to the section 6AT. Accordingly, at the cut section location CS relay CEVR will remain operating and relay CEVPR will remain picked up and relays CWTR and CWHR will remain released.

At the intermediate signal location, coder 1811GT will code energy supplied from the battery LB to code transmitting relay 4ECTR by a circuit which may be traced from the positive terminal B of the battery LB over the front contact a of coder ISGCT which is operating at a code rate, front contact 0 of relay 4EHR, back contact a of relay 4DSNPR, reverse contact 0 of relay 4DSR, and the winding of relay 4ECTR to the negative terminal N of battery LB. Accordingly, relay 4ECTR will operate at a 180 code rate and will code the energy supplied to the section 4T, which will be of reverse polarity, over a circuit which was already described with relation to the supply of feed-back code of reverse polarity from battery 4ETB to the section 4T.

With track section 4T being energized with energy of reverse polarity, relay 2ETR will continue operating and relay 2EHR will remain picked up, and relays ZWVR and ZWVPR will remain released. Relay ZDSKRPR has already picked up and, accordingly, transformer W2 will be operating as an impulse transformer and supplying energy to relay 'ZWCTR over a circuit which may be traced from the lower terminal of winding S of transformer W2, over front contact a of relay ZDSKRPR, and the Winding of relay ZWCTR to the negative terminal N of battery LB which is also connected to the upper terminal of the winding S of transformer W2. Winding S1 of decoding transformer ZETT will supply energy to the primary winding of transformer W2 in a manner-already described. Therefore, feed-back code will be supplied to the track section 4T from the battery 4WTB and this code will be of reverse polarity due to the fact that the track section 4T will be energized over a circuit which has already been traced with relation to normal code of reverse polarity being transmitted by relay ZWCTR. Therefore, at the intermediate signal location IS, relay 4EVR will commence operating on feed-back code and relay 4EVPR will remain picked up, and relays 4WTR and 4WHR will remain released. The circuit arrangement as now described is ready for a movement of a train in the direction opposite to the normal direction, that is, for an eastbound train movement.

It should be noted at this time that with the apparatus set for a westbound train movement, had any of these track sections been occupied so that the feed-back code in any of the track sections was of reverse polarity at the time lever L1 was thrown to its reverse position, it would have been impossible for the polar relays in the several track sections of the track stretch to have cascaded to their reverse positions so that traffic could be cleared for the eastbound traffic movement. It is because of this necessity for the circuit arrangement to be sending out normal andfeed-back code of normal polarity in order to reverse trafiic from westbound to eastbound that a complete locking of the traflic direction in one direction is achieved once a train has entered the stretch.

With the circuit arrangement now set for an eastbound train movement, let it be assumed that a train on the main track approaches section 2T from the west. Signal control lever L2 will be closed, energizing signal control relay 2RAHR, so that signal 2RAS displays a green aspect since relay 2ETR is operating at 180 code rate and relay ZDR is energized. When relay 2RAHR picks up, relay ZRMSR will release. Accordingly, the polarity of the feed-back code being transmitted by relay ZWCTR will be changed by contact 0 of relay ZRMSR, that is, the feed-back code will now be of normal polarity rather than of reverse polarity. In a manner similar to that described with respect to a westbound movement, this feed-back code of normal polarity will cascade from the Western headblockto the eastern headblock so that all the feed-back code transmitted on the track stretch will be of normal polarity whereas, the normal code will continue to be of reverse polarity. This will release relay eEVPR at the eastern headblockand will prevent any operation of the traflic relay 6DSR, so that the direction of trafiic cannot be changed. Relay 6WTR at the eastern headblock location will commence to operate and will pick up relay 6WHR and, when signal GRS is cleared, relay oDR. The picking up of these relays, however, will have no effect because all signal control circuits controlled by these relays are also controlled by either relay 6DSR or relay 6DSKR in their normal position. Since these latter two relays are in their reverse positions, there is no change in the signal controls, and it will be impossible to clear signals 6LBS or 6LAS at this time.

When a train occupies section 2T, the wheels and axles of the train will shunt relay ZTR causing it to release and thereby opening the energizing circuit for signal control relay ZRAHR causing it to release. Therefore, the red lamp R of signal ZRAS will he lighted and signal ZRAS will indicate stop. The circuit energizing the red lamp may be traced from positive terminal B of battery LB, over back contact 12 of signal control relay ZRAHR and the red lamp R of signal ZRAS to negative terminal N of battery LB. With relay 2TR released, the feedback code being transmitted by code transmitting relay ZWCTR will continue to be of normal polarity even though approach locking relay 2RMSR is now picked up. Accordingly, feed-back code being transmitted all along the track stretch will be of normal polarity. When the train occupies section 4T the wheels and axles of the train will shunt the normal code being transmitted by relay ECTR and relays ZETR and 2WVR will both become released. Therefore, no feedback code will be transmitted to section 4T. With relay ZETR released, relay ZEHR will release, thereby additionally opening the energizing circuit for relay ZRAHR. Accordingly, signal ZRAS will continue to display a red aspect.

At the intermediate signal location IS, relays 4EVR, 4WTR, 4EVPR and 4WHR will all be released. Signal 4R8 will display a green aspect, assuming that signal 6R5 is now cleared, due to the energization of the green lamp G by a circuit which may be traced from the positive terminal B of battery LB, over reverse contact d of relay 4DSR, front contact e of relay 4EHR, front contact b of relay 4DR, which is energized when signal 6R5 is cleared, green lamp G of signal 4R5, back contact f of relay lWHR, and back contact c of relay 4EVPR to the negative terminal N of battery LB. However, the lamps of signal 4L5 will be deenergized due to the fact that relay 4EHR is picked up thereby opening the energizing circuit for signal 4L5 at back contact 1 of relay 4EHR.

When the train occupies section (rAT, any energy transmitted to that track section will be shunted by the wheels and axles of the train thereby causing relays 4ETR, 4WVR, 4-EHR and 4WVPR to release. Accordingly, relay 4lECTR will commence to operate at a 75 code rate due to its energization by a circuit which may be traced from positive terminal B of battery LB, over the contact a of coder '75CT which is operating at a 75 code rate, back contact 0 of relay lEI-IR, back contact a of relay lDSNPR, reverse contact 0 of relay 4DSR, and the winding of relay 4ECTR to negative terminal N of battery LB. Accordingly, at the western headblock location, relay ZETR and relay ZEHR will pick up and relay ZWCTR will commence transmitting feed-back code of reverse polarity. Due to the fact that normal and feed-back code on section 4T will be coded at a rate of 75 pulses per minute, clear control relay 2BR will remain released. Accordingly, if signal ERAS is recleared for a following train, it can only display a yellow aspect, since contact a of relay ZDR is released. Signal 4R8 will now be in a condition to display a red aspect, if a train were to enter section 4T, due to the completion of the circuit which may be traced from positive terminal B of battery LB, over reverse contact d of relay ADSR, back contact e of relay 4EHR, the red lamp R of the signal 4R3, back 20 contact 1 of relay 4WHR, and back contact 0 of relay 4EVPR to negative terminal N of battery LB. However, with no train in section 4T, relay 4EVPR is picked up and signal 4R8 will be dark, its energizing circuit being opened at back contact 0 of relay 4EVPR.

With no feed-back code being received over section 6AT, relays CEVR, CWTR, CEVPR and CWHR will all be released. Accordingly, the feed-back code transmitted by code transmitting relay CWCTR will be of normal polarity which, as already has been explained, is opposite to the usual polarity established for an eastbound train movement. The feed-back code will be of normal polarity due to the fact that the rails or" section 613T will be energized by a circuit which may be traced from the positive terminal of battery 6BWTB, over back contact 12 of relay CEVPR, front contact a of relay CWCTR which is now operating at a code rate, to the rail 1, and from the rail 2 to the center tap of battery 6BWTB which is negative with respect to rail 1.

Accordingly, relay 6WTR will continue to operate and relay 6WHR will remain energized, and relays EVR and 6EVPR will remain released. Relay CECTR will be operating at a 180 code rate transmitting normal code of reverse polarity to track section 6AT. However, with the train occupying section 6AT, relays 4ETR, 4WVR, 4EHR and 4WVPR will all be released as previously noted, as well as relays CEVR, CW'lR, CEVPR and CWHR. With these relays released, the lower windings of relays 4DSR and CDSR will be deenergized but these relays will remain in their reverse position due to their stick characteristics. Code transmitting relay 4ECTR will continue to transmit normal code at a 75 code rate to section 4T.

When the train occupies section 613T, any energy being supplied to that section will be shunted by the wheels and axles of the train thereby causing relays CETR, CEHR, 6WTR and 6WHR to release. Furthermore, relays CWVR, CWVPR, 6EVR and GEVPR are already released. Accordingly, relay CECTR will not be supplied with energy and it will release. Therefore, no normal code will be supplied to section AT from battery AETB, thus causing relays 4ETR and Wt V R to remain released. With relays 4ETR and 4WVR both released, no energy will be supplied to relay 4WCTR and, therefore, no feedback code will be supplied to section 6AT. Accordingly, relays CEVR and CWTR will be released. I

Section 4T will be supplied with normal and feed-back codes of reverse polarity in a manner substantially the same as that described when the eastbound train occupies section 6AT. Accordingly, in a manner already described, signal 4RS will be in a condition to display its red aspect, but it will be dark, and signal ZRAS will be in a condition to display its yellow aspect it the signal is cleared for a following move.

At the eastern headblock location, signals 6LAS and 6LBS will continue to display a red aspect for reasons made clear when the traific direction reversal was described.

When the train occupies section 8T, relay 8TR will be shunted by the wheels and axles of the train and will, therefore, release. The energizing circuit for the lower winding of relay 6DSR will become open at front contact a of relay 8TR but relay 6DSR will remain in its reverse position due to its stick characteristic. Signal 6R8, which is controlled by means not shown, will display a stop or red aspect and, therefore, relay 6RAHR will be released. Accordingly, 75 code will be supplied to relay 6ECTR by a circuit which may be traced from positive terminal B of battery LB, over the front contact of coder 75CT which is operating at a 75 code rate, back contact a of relay 6RAHR, back contact a of relay 6DSKNPR, and the winding of relay 6ECTR to negative terminal N of battery LB. Accordingly, normal 75 code of reverse 21, polarity will be transmitted to section 6BT by relay 6ECTR.

At the cut section location CS, relay CETR will commence operating at a 75 code rate and relay CEHR will pick up. Accordingly, a feed-back code at a 75 code rate and initially of normal polarity will be transmitted to section 6BT by relay CWCTR and a normal 75 code of reverse polarity will be transmitted to section 6AT by relay CECTR. At the intermediate signal location IS, relay 4ETR will commence operating at a 75 code rate and relay 4EHR will pick up. Therefore, teed-back code at a 75 code rate and of reverse polarity will be transmitted to section 6AT, thereby causing relay CEVR to commence operating and relay CEVPR to pick up. When relay CEVPR picks up, its contact b changes the polarity of the feed-back code being transmitted by relay CWCTR from normal to reverse, which is correct for the established eastbound trafiic. Due to decoding unit 180DU being supplied with 75 code, relay 4DR will remain released. If another train were to enter section 4T at this time, thereby causing relays 4EVR and 4EVPR to release, signal 4R5 would display a yellow aspect due to energization of its yellow lamp Y by a circuit which may be traced from the positive terminal B of battery LB, over reverse contact d of relay 4DSR, front contact e of relay 4EHR, back contact b of relay 4DR, yellow lamp Y of signal 4R8, back contact 7 of relay 4WHR and back contact c of relay 4EVPR to the negative terminal N of battery LB. However, with no train in section 4T, signal 4RS will be dark due to the fact that the above traced circuit will be open at back contact c of relay 4EVPR. Section 4T will be supplied with normal and feed-back code at a 180 code rate of reverse polarity in a manner substantially the same as that described for the apparatus when the stretch of track was vacant and the apparatus was arranged for an eastbound train movement.

When the train vacates section 8T, the circuit arrangement will assume the same condition it was in before the train movement started.

It should be clear that from the time signal 2RAS (or 2RBS) was cleared and during the time the train occupied any of the sections from 2T to 8T, inclusive, it would have been impossible for the direction of trafiic to be changed to westbound since upon attempting to change the direction of traflic, the cascading of the polar relays would have been forestalled either by the deenergization of one of the DSK relays or by the fact that the polarities of the normal and feed-back codes were opposite.

It should also be clear that it would make no difference in the operation of my appaartus if the train were to use a passing siding since the section 2T includes a portion of the passing siding including rails 3 and 4 and section 8T includes part of the passing siding including rails 5 and 6.

From the foregoing description it should be apparent that my track circuit system would operate in a manner similar to that already described regardless of how many intermediate signal locations were in the circuit and regardless of how many cut sections were employed because these intermediate signal locations and cut sections merely cascade the action as illustrated with the cut section CS and intermediate signal location IS between sections 4T and ST. It should be further pointed out that my system will operate just as well if no out section were present and similarly it would operate if there were no intermediate signal locations present. If there were no cut sections in the system the circuit arrangement at the intermediate location would cascade the action of the relay from one headblock to another directly as it does now through the cut section, and if there were no intermediate signal location, then there would be a direct action from one headblock to the other without the intermediate cascading of the relays.

Due to the symmetry of the circuit arrangement it is not deemed necessary to explain how the trafiic direction could be restored. to the normal Westbound movement since the action would be substantially similar to the description of the change of direction from westbound to eastbound which has already been made.

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

Having thus described my invention, what I claim is:

1. In combination with a stretch of railway track over which traific may move in either direction, said stretch being divided into a plurality of track sections by insulated joints, said stretch being provided with a first and second headblock signal at its respective ends, each track section being provided at each end with two polarized code following track relays having their windings connected in series one being responsive to current of normal polarity and, the other being responsive to current of reverse polarity, a plurality of code detecting relays, one associated with one each of said track relays and energized when its associated track relay is operating, each track section being provided at each end with a code transmitter for selectively actuating the track relays atthe other end of the track section, a traific direction selecting lever which may occupy a first and a second position corresponding to the direction of trafl-lc over the stretch, a polarized traffic direction relay at the junction of each two adjacent track sections, means including said traffic selecting lever in its first position for actuating the code transmitter at thev first end of said stretch to transmit normal code of normal polarity to the first, end section, said normal code of normal polarity in said first end section actuating the track relay at the vend remote from the first end of said'stretch responsive to currents of normal polarity and thereby causing its associated code detecting relay to pick up, means including the track relays and their associated code detecting relays at the end of each section remote from said first end for cascading said normal code of normal polarity through the remaining sections of said second end, said code transmitter in each section at the end remote from said first end transmitting feed-back code of normal polarity during the off time of said code transmitter transmitting normal code to the section and controlled by said track relays and their associated code following relays at the end remote from said first end, said feed-back code of normal polarity in each section actuating the track relay responsive to impulses of normal polarity at the end of the section nearest said first end of said stretch and thereby picking up its associated code detecting relay, means including the track relays and their associated code detecting relays at the second end of the stretch for conditioning said headblock signal at said second end of said stretch to display its proceed aspect due to the presence of normal code of normal polarity in said second end section, means including said traffic selecting lever in its second position for actuating said code transmitter at the first end of said stretch to transmit normal code of reverse polarity to said first end section and thereby actuate the track relay responsive to currents of reverse polarity at the end of said first end section remote from said first end and pick up its associated code detecting relay, means including the track relays for each section at the end remote from the first end. of said stretch responsive to impulses of reverse polarity and their associated code detecting relays for cascading said normal code of reverse polarity through the remaining track sections to said second end of said stretch, means including said track relays and their associated code detecting relays at said second end of said stretch and the traflic direction relays at said second end of said stretch for causing said code transmitter at said second end to transmit feed-back code of reverse polarity to the second end section, means including the track relays in each section at the end remote from said second end and their associated code detecting relays for cascading said feed-back code of reverse polarity through the remaining sections to said first end of said stretch, said reversal of polarity of said normal and feed-back codes throughout the stretch causing said trafiic direction relays to reverse the tratfic direction and thereby cause said second headblock to display its stop aspect and said first headblock to be placed in a condition for displaying its proceed aspect.

2. In a two directional single track system of signaling, a track section provided with a track circuit at the entering end of the stretch of single track for a given direction of tratfic, means including a two-position trafiic selector in its normal position for supplying normal code of normal polarity to said track circuit at the leaving end of said section, means including said trafiic selector in its reverse position for supplying normal code to reverse polarity to said track circuit at the leaving end of said track section, means for supplying feed-back code of normal polarity during the off time of said normal code at the entering end of said section provided said section and the section immediately in advance of it are unoccupied, a first track relay operating when said normal code is of normal polarity, a second track relay operating when said normal code is of reverse polarity, a polar stick trafiic direction relay, a polar stick auxiliary relay, said auxiliary relay energized to its normal position only when said trafiic direction relay occupies its normal position and said first track relay is operating, said auxiliary relay energized to its reverse position only when said second track relay is operating, said traffic direction relay energized to its reverse position only when said auxiliary relay is reversed and said trafiic selector is reversed, and means effective upon the reversal of said traffic direction relay for reversing the polarity of the feed-back code and thereby the direction of tratfic over the stretch.

3. In a two-direction signaling system for a stretch of single track railway, the combination comprising, track circuit means for said stretch, means including a twoposition trafiic selector means in its normal position for supplying normal code of a preselected polarity to said track circuit means at the exit end of said stretch for the selected'traific direction, means for supplying feedback code of the same polarity to said track circuit means at. the entrance end of said stretch, other means including said tramc direction selector means in its reverse position for supplying normal code of the opposite polarity to said track circuit means at said exit end, a pair of track relays connected to said track circuit means at said entrance end so as to be selectively responsive to the received normal track code, one being operable by code of said preselected polarity and the other by code of said opposite polarity, a two-position traffic direction stick relay, circuit means including contacts of said track relays for energizing said trafiic direction relay to operate to its normal or to its reverse position according to the position of said traific selector means and the polarity of the received track code, said circuit means being arranged to prevent the operation of said traffic relay while said stretch is occupied to thereby provide directional locking, and means actuated by said traific relay in its reverse position to reverse the polarity of said feed-back code to thereby reverse the direction of traffic through said stretch.

4. In a signaling system for a stretch of single trackmal code to said track circuit means having a preselected polarity or the opposite polarity according as said traffic selector means occupies its first or its second position respectively, a first and a second track relay at the entrance end for the selected traffic direction selectively connected to said track circuit means so that said first relay operates when the normal code has said preselected polarity and said second track relay operates when the normal code has said-opposite polarity, a polar stick traific direction relay means having a first and a second position corresponding to said first and said second positions of said trafiic selector means, a first circuit means including contacts of said first track relay to energize said traffic relay means to operate to its first position, a second circuit means including cont-acts of said second track relay to energize said trafiic relay to operate to its second posi tion, coding means at said entrance end responsive to the operation of said track relays and effective to supply feed-back code to said track circuit means during the otf period of said normal code, said feed-back code being of said preselected polarity when said first track relay is operating, and other circuit means actuated by the operation of said trafiic relay means to its reverse position when said traffic selector means occupies its reverse position to reverse the polarity of said feed-back code to said opposite polarity to thus reverse the selected direction of trafiic over said stretch.

S. In combination, along a stretch of railway track over which traffic moves in either direction, said stretch being divided by insulated joints into a plurality of track sections, a first and a second headblock signal at a first and a second end of said stretch respectively, a traffic direction selecting mean-s which may occupy a first or a second position corresponding to selected direction of trafiic over said stretch; a pair of code following track relays at each end of each track section having connections to the section, a first track relay of each pair being responsive to code of one relative polarity and the second track relay being responsive to code of the opposite relative polarity; a code transmitting means at each end of each track section having connections to the corresponding section to actuate the track relays at the other end of that section; a plurality of code detecting relays, one associated with each track relay and energized when that associated track relay is operating; a first circuit means including said trafiic selecting means in its first position to cause the code transmitting means for the first section adjacent said first end to transmit a normal code of said one polarity, a second circuit means including said trafiic selecting means in its second position to cause said first end code transmitting means to transmit normal code of said opposite polarity, means including the track relays and associated code detecting relays at the end of each section remote from said first end and the code transmitting means at the end of each section other than said first end section remote from said second end to cascade said normal code of either polarity throughthe remaining sections to said second end, the code transmitting means at the end of each section remote from said first end being actuated by the operation of said first track relay at the corresponding location to transmit a feedback code of said one polarity during the off period of said normal code, means including the track relays at said second end of said stretch for conditioning said second headblock signal to display its proceed aspect only when the received normal code is of said one polarity, a polar stick traflic direction relay at the junction of each two adjacent track sections, a two-position traffic direction relay means at said second end of said stretch; means responsive to the receipt of normal code of said opposite polarity at said second end and including the second track relay at that location, its associated code detecting relay, and said trafiic direction relay means to actuate the code transmitting means at said second end to transmit a feed-back code of said opposite polarity to the track 25 section adjacent said second end, means including said track relays and associated code detecting relays at the end of each section remote from said second end to cascade said feed-back code of opposite polarity through the remaining sections to said first end, said reversal of polarity of the normal and feed-back codes being effected only when said normal and said feed-back codes throughout said stretch are of said one polarity at the time said traific selecting means is moved to its second position, the operation of said second track relays at the adjoining ends of each two adjacent track sections by said normal and said feed-back codes of saidopposite polarity energizing their associated code detecting relays to cause the corresponding trafiic direction relay to reverse position to 26 thus reverse the traffic direction through said stretch, and means eifective upon the reversal of said tratfic direction relay-s to halt the supply of normal code to said first end section-and to initiate a supply of normal code of said opposite polarity to said second end section.

References Cited in the file of this patent UNITED STATES PATENTS Re. 22,841 Shields Feb. 11, 1947 1,912,923 Thompson June 6, 1933 2,244,901 Staples June 10, 1941 2,318,545 Van Horn May 4, 1943 2,357,240 Van Horn Aug. 29, 1944 2,430,314 Van Horn Nov. 4, 1947

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