US2874272A - Two-direction coded track circuit control for railway signals - Google Patents

Description

C. E. STAPLES Feb. 17, 1959 TWO-DIRECTION CODED TRACK CIRCUIT CONTROL FOR RAILWAY SIGNALS .Filed Feb. 18, 1953 2 Sheets-Sheet 1 INVENTOR.

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:4 TT 01-? N R m" z @EQ MESN C. E. STAPLES TWO-DIRECTION CODED TRACK CIRCUIT CONTROL FOR RAILWAY SIGNALS Crawfirpd E. Staples.

By M k H15 Feb. 17, 1959 Filed Feb. 18, 19 53 llnited States Patent TWO-DIRECTION 'CODED TRACK CIRCUIT CONTROL FOR RAILWAY SIGNALS Crawford E. Staples, Homewood, Pa., assignor to Westinghouse Air Brake Company, Wilmerding, Pa., :1 core poration of Pennsylvania Application February 18, 1953, Serial No. 337,586

7 Claims. (Cl. 246-,38)

My invention relates to a two direction coded track circuit control for a railway signaling system, and particularly to such track circuit control for use on short stretches of single track over which traffic may move in either direction. I

The system outlined herein is particularly adaptable for controlling signals governing entry of trains into passing tracks in centralized traflic control (.C. T. C.) territory, where said passing tracks are provided with track circuits of the coded type. In order to provide protection against simultaneous opposing moves into a pass- 1ng track, it is generally the custom to use line Wire control to check opposing signals. Line wire control for governing movement into a siding is expensive and requires considerable maintenance, especially Where passing tracks are of great length to accommodate more-than one train or to allow nonstop meets. A system which eliminates the need of such line wires has considerable advantage in railway signal systems by reducing initial expense, reducing maintenance, and increasing reliability.

Often in multiple track territory itkis desirable, or necessary, to provide reverse direction signaling on one track for a short stretch. An example would be the necessity of returning helper locomotives against normal trailic to the nearest cross-over to the normal track for the direction of their return move, perhaps a distance of only one track section. Here again, a signal system which does not require line wires and which can be remotely controlled is a definite advantage. system embodying my invention would meet the requirements for such an installation.

It is an object of my invention to provide an improved system of coded track circuit control for short stretches of railway track.

A further object of my invention is to provide remote control of the direction of trafiic in the short stretch of railway track using a signal system of the type here in- A signal volved without exceeding the normal capacity of the remote control apparatus.

Another object of my invention is to provide an improved system of signaling of the type described which operates without line wires and in which all functions are performed by energy transmitted over the rails of the stretch of railway track.

A still further object of my invention is to provide in a signal system of the type described a check against simultaneous opposing moves in the short stretch of railway track solely by use of coded track circuits.

An additional object of my invention is to provide V for operation of the signal system with a simple front contact repeater in the track circuit if a cut section is necessary because of the length of the track section.

Still another object of my invention is to provide an indication at the remote control apparatus of the occupancy of the track section, such indication to be furnished always from the same end of the stretch of railway traclg.

Other objects and features of my invention will be 2,874,272 Patented Feb. 17, 1959 apparent from the following description taken in con nection with the accompanying drawing.

In practicing my invention, a short stretch of railway track over which traffic is to move in either direction, but only in one direction at a time, is divided into one or more sections. Normally the stretch will consist of a short entry section, a main section and a short exit section. Each section is provided with a track circuit consisting of the rails of the section, a source or sources of power, and a track relay or relays. A wayside signal of any type already known to the art is provided at each end of the stretch of railway to govern the movement of trains into that stretch from the respective directions.

A source of energy for the track circuit is provided at each end of the main section. The track relays at both ends of this section are of the code following type known to the art. However, code transmitters are pro.- vided at only one end of the section, known as the master end. The second, or dependent end is provided with apparatus for generating a reverse code when the in the direction from the dependent end to the masterend. This is accomplished by the normal flow of coded track current at a selected basic code rate, such as the well-known 180 code frequency, from the master end through the track circuit to the track relay at the dependent end. To operate the signal at the dependent end to display a proceed indication, it is only necessary for the remote control signal relay to be operated to the proper position and, if all other pertinent conditions are proper; that is, switch positioned, short initial track section unoccupied, opposing signals at stop; the signal operates to display a proceed indication. After the train passes through the section in the normal direction, coded track current at the basic 180 code frequency is again transmitted through the rails and the normal direction of traffic is continued.

When it is desired to reverse the direction of traffic so that a train may enterthe stretch at the master end and leave at the dependent end, the remote control signal relay at the master end must be operated to a position which requests the clear signal. This causes a steady pulse of steady energy, longer than one of the normal code pulses, to be superimposed on the normal bas c track code. Receipt of this long pulse at the dependent end of the track circuit conditions the local circuits, if the entering signal at the dependent end has not been previously cleared, to transmit a reverse code back through the rails. This reverse code conditions a local circuit at the master end to permit the signal to display 2. proceed indication, again providing that other conditions are proper, that is, short initial section unoccupied,

switch positioned, opposing signals at stop. Thus the longer pulse establishes the reverse code and the reverse code etablishes the reverse direction of trafi'ic. Receipt of the reverse code at the master end also conditions other local circuits to change the code rate of the normal track current to a second and lower selected code rate such as the well-known code frequency. This lower code rate is transmitted in a distorted form for reasons to be described hereinafter. Receipt of the coded track current of the 75 code rate at the dependent end will not permit the entering signal at that end to be cleared, but will allow the transmission of the reverse code to continue. After the passage of a train in the reverse direction, a long pulse of steady energy is superimposed on the coded track current from the master end. This steady energy causes the reverse code transmission to cease, and the entire system then reestablishes normal operation for the normal trafiic direction.

I shall describe one form of coded track circuit con- 3 trol for railway signaling systems embodying my invention and shall then point out the novel features thereof in claims. 1

In the accompanying drawings, Figs. la and lb, when placed end to end with Fig. In at the right, are diagrammatic views showing a stretch of railway track equipped with one form of apparatus embodying my invention. In both figures, like reference characters are used to designate similar parts.

Referring to the drawings, there is shown therein a stretch of railway track over which traflic may move in either direction. This stretch of railway includes a passing siding which is connected to the main track at the right or east end by a switch 7W, and at the left or west end by a switch 9W.

The track rails 1 and 2 of the passing track are divided by insulated joints 3 into a plurality of track sections including a detector section 7T which includes switch 7W, a detector section 9T which includes switch 9W, and a section 8BT which is the passing track beside the main track 8T.

If section 8BT is of great length, it may be divided into two sections, 8BT and BT, by a cut section as shown in the upper right portion of Fig. 1b. The apparatus at the cut section is of a type already known to the art and as such is not part of my invention. As hereinafter described, the novelty in my present invention resides in the fact that this type of cut section apparatus can he used in a system which includes a reverse code. For purpose of clarity, mention of this cut section will be omitted during the general description of the operation of this system, and the track circuit of section 8BT will be considered as though the insulated joints 3 marked When Required are not installed.

The single track portion of the railway at each end of the passing track may likewise be divided into track sections which may be equipped with signaling apparatus of any type which is already known to the art.

This invention is particularly directed to the track circuit for the section 8BT and to the means for controlling signals 8LB and 10RB which govern traffic in the passing track, and is not concerned with the signaling systems for the single track main line portion except as the apparatus of this invention is installed to operate in conjunction with the apparatus for the single track portion. It is sufiicient for the present application to point out that the equipment at each end of the passing siding includes relays controlled from the remote ofiice through a suitable remote control system. These relays govern the wayside signals and switch operation mechanisms by means of circuits of the usual and well-known type. These remotely controlled relays are disclosed and described only as they are involved in the track circuit control apparatus.

The detector sections 7T and 9T are each provided with a track circuit including a track relay designated by the reference character TR prefixed by a numeral corresponding to the numeral forming a part of the reference character for the section, which relay is energized by steady current supplied by a track battery over the section rails in the usual manner, as will be apparent from an inspection of the drawings.

Each switch has associated therewith normal and reverse indicator relays, identified by the reference characters NKP and RKP, respectively, prefixed by a numeral corresponding to the switch, these relays being selectively energized according to the position of the switch. For example, the relay 7NKP is energized by a simple circuit including a suitable source of current, having terminals B and N, and a contact member 70 operatively connected to the switch 7W, as indicated by a dotted line, and closed when the switch is moved to'its normal position. When the switch 7W is operated to its reverse position, the contact member 7C is moved to the position indicatedby the dotted outline and an obvious circuit relays 9NKP and 9RKP are energized by circuits controlled by a contact member 9C operatively connected to the switch 9W.

The track section 8BT is provided with two sets of coded track circuit apparatus, one set at each end but not identical. The right-hand or east end of the track section 8BT may be referred to as the master end of the section, and is provided with code transmitters 180CT and CT for providing coded current of the and 75 code rates, that is, current which is periodically interrupted, or coded, at the rate of 180 and 75 times, respectively, per minute. These code transmitters may be of any suitable type and are shown as the relay type which, when supplied with current, are operable to open and close their contacts at a selected code rate. As here considered, the code transmitters 180CT and 75CT operate their contacts at the code rate of 180 and 75 times per minute, respectively, the 180 code being herein referred to as the basic code. The left-hand or west end of the section may be referred to as the dependent end of the section. The normal direction of trafiic will be considered as being from the dependent end to the master end, being in this case eastbound. The equipment at each end of the section 8BT includes a source of direct current, the positive and negative terminals of which are designated B and N, respectively.

As shown, there is a code following track relay 8WBTR located at the east end of section 8BT and operated by energy supplied by battery SWBTB at the west end of the section as will appear hereinafter. A similar code following track relay 8EBTR located at the west end of the section is operated by energy supplied from battery 8EBTB at the east end of the section. The relays SEBTR and SWBTR are of the well-known biased type. It is sufiicient to point out that these relays have armatures which are picked up, closing front contacts, only when current flows in the relay winding in the direction indicated by the arrow placed on the winding. The armatures are biased to a released position, closing back contacts, when the relay is deenergized and are operated also to the released position when current flows through the winding in the direction opposite to that indicated by the arrow.

The track circuit apparatus at each end of the section 8BT also includes code repeater and other relays which are provided for interconnecting the remotely controlled relays with the track circuit. It is believed that these relays and their circuits can best be understood by a description of the operation of the apparatus.

The equipment as shown in the drawing is in its normal position, that is, the position it occupies when the sections 7T, 8BT and 9T are unoccupied, the direction of traific is from the dependent to the master end of the section 8BT, and no signal is cleared for a train approaching from either direction. Thus signals 8LA, 8LB, 10RA, 10RB are displaying the stop indication, and switches 7W and 9W are positioned normal. Signals 8R, SRB, 10L, and 1(lLB are shown in the drawing to indicate the usual arrangement of signals at the respective locations. Since they control the movements of trains into the adjacent single track portions at either end of the passing track, their position and control, except for the remote controlled relays, are not involved in the present invention and no further mention will be made of these signals. 'Signals 8LA and 10RA govern the movement of trains into the main track section 8T. Again, since these signals are not directly involved in my invention, no further mention need be made of them.

Under these normal conditions, the remote controlled signal stick relays :BLHS and 8RHS at the east end will have their armatur-es positioned normal, closing the normal or left-hand contacts. This normal position may also be designated the first position, with the opposite or reverse position designated the second position. These is closed for energizing the relay 7RKP. Similarly, the 7 two stick relays control the west and eastbound signals asvaa a 8, respectively. In other words, if local conditions per.- miL hen eith r of t es relays'is op at y te control to its reverse position, the corresponding signal is operated to its clear position, the main line A signal or the passing siding 13 signal clearing according to the position of switch 7W. Obviously, only one of the relays SLHS and SRHS may be operated to its reverse position at any one time. The operated relay remains in its reverse position until returned to normal automatically by a train occupying section 7T or until returned to normal by the remote control operator. The signal stick relays LHS and 10RHS at the west end of section 8BT function in a similar manner, and are shown in their normal position.

The directional stick relays SDSR and 1%)DSR, located one at the east end and one at the west end, respectively, are also remote controlled in accordance with the established direction of traflic in the associated single track stretches. As shown, relay SDSR is picked-up and east bound trafiic is established in the single track stretch east of section 7T. Relay 10DSR is released and westbound traffic is established in the stretch west of section 9T. The position which these relays occupy for any established traffic direction is immaterial to my invention and these relays are shown merely to illustrate some association between the system of my invention and the signaling systems for the single track stretches.

Under the normal conditions shown, a coded track current of the basic 180 code frequency will be flowing from the track battery SEBTB at the east .end through the rails of section SBT tothe track relay SEBTR at the west end. As will be described in the following paragraphs, this flow of track currentestablishes the normal direction of traffic, which has been defined previously as being eastbound.

The positive terminal of the battery 8EBTB.is connected to rail 1 of section 8BT through a circuit passing over frontrcontact 4 of a code repeater relay CTR, winding of relay ,SWBTR from right to left, and lead wire 1L, and the negative terminal is connected to rail 2 through a limiting resistor and the lead wire 2L. Here, andclsewhere in this description, current will be assumed to flow from positive battery through .acircuit to negative battery. Since, then, this coded rail current flows in the winding of relay .SWBTR in the direction opposite to the arrow, the relay is ,held down. The relay CTR is also a biased relay, and is energized by current flowing in a circuit which may be traced from terminal B of the source over front contact 5 of code transmitter 180CT, back contact 6 of the signal control relay LBHR, through resistor R10, over front contact 7 of the code control relay CCR, through the winding of relay CTR from right to left, and over back contact 8 of relay SWBTR to terminal N of the source. The code transmitter 180C'Iis energized over a circuit passing from terminal B of the source over front contact 49 of relay CCR through the winding of coder 180CT to terminal N of the source. It follows that the relay CTR is operated in step with the code transmitter 180CT and the current supplied to the rails of section 8BT is correspondingly coded.

As will be hereinafter described, the transmission of a coded rail current of the basic 180 code rate is the principal factor upon which the establishing of the eastbound direction of traffic and the clearing of signal 10KB depend. It is necessary, therefore, to prevent the transmission of the 180 code if conditions at the east end are not proper. t is apparent from the preceding description that this can be done by controlling the operation of the CTR relay. For this reason, back contact 8 of the SWBTR relay is included in the energizing .circuit for relay CTR for the purpose of looking out this relay in case the SWBTRrelay should be heldup by foreign current in the track circuit. This check pre- .ven ts theSWBTRrelay from coding under such conditions and thus picking up relay LBI-lR in a manner to appear hereinafter. V i l Front contact 7 of relay CCR is included in the energizing circuit for relay'CTR to assure that various remote controlled relays are in their normal positions, that signal 8LB is not cleared, and that signal locking is not in effect. Relay CCR is normally energized by a circuit passing from terminal B of the source either over front contacts 44 and 45 of relays LMR and 7TR, respectively, in series, or over front contact 46 of relay 7NKP, and then through back contact ,48 of relay SLBP and the winding of relay CCR toterminal N of the source. The signal locking relay LMR is normally energized by a pickup circuit which may be traced from terminal B of the source over normal contact 43 of relay 8LHS, front contact 47 of relay SDSR, and through the winding of relay LMR to terminal N of the source. Relay LMR also has a stick circuit which includes its own front contact 42 and back contact 411 ofirelay LBHR. Relay SLBP is the repeater of the signal SLB and is energized and picks up when the lsignal is operated to display a proceed indication. l

Let us now assume either that switch 7W is reversed so that relay 7NKP is deenergized, and its front contact 46 open; or that no switch exists in the stretch of single track equipped with the signal system described. Under these conditions, the portion of the energizing circuit for relay CCR including front contact 46 of relay 7NKP will be open or non-existent, and relay CC R will be energized only if relay LMR is picked up. This will only occur when the contacts of the remote controlled relay SLHS are in their first position, that is, their normal position. Transmission of a coded track current of the basic code rate, upon which the clearing of the signal at the west end depends, as will be hereinafter deat the east end, current flowing in a circuit passing from the positive rail 1 over lead wire 3L, through winding of relay 8EBTR in the direction of the arrow, over back contact 39 of a code repeating relay RIR, to be referred to later, and through lead wire 4L .to negative rail 2. As hereinbefore stated, in the present description it s assumed that the insulated joints at the cut section shown in the upper right of Fig. lb are not installed. Energy supplied through ;a circuit traced from terminal B of the source overfront contact 9 of relay 8EB TR and through the winding of a track repeater relay ETP w th resistor R1 in multiple with the winding, to terminal N of the source causes the relay ETP to also pick up its armature, closing front contacts, whenever relay 8EBTR picks up. Thus, ifrelay SEBTR receives coded energy from the track circuit, it will operate its armature to close its front contacts at the samecode rate. It is then apparent that the operation of relay ETP, repeating relay 8EBTR, will also be at an identical code rate. If the energy received by relay SEBTR is steady, as will be discussed hereinafter, this relay will remain picked up with front contacts closed, and relay ETP is steadily energized and holds up. Under the L-BHAR being a front contact repeater, and relayEBTP being a back contact repeater. Both relays are made slow release so that they will remain picked up, that is, front contacts closed, when relay ETP is operating at any code rate. With relay ETP operating normally at the 180 code rate, energy which is supplied over a circuit running from terminal B of the source over front contact of relay ETP and through the winding of relay LBHAR to terminal N of the source picks up relay LBHAR, which holds up during normal coding, as previously stated, because it is made slow release by the energy storage device, consisting of resistor R2 and capacitor C1 in series, connected in multiple with the winding of the relay. Energy over a circuit traced from terminal B of the source over back contact 10 of relay ETP through the winding of the relay EBTP to terminal N of the source picks up or holds up the armature of relay EBTP, which also remains up during normal coding because of resistor R3 connected in multiple with the winding.

With relays LBHAR and EBTP both picked up, and relay ETP operating at the 180 code rate, circuits are established and conditions are proper to cause relay RBHR to pick up its armature. This relay is the 180 code detecting relay which must be energized and picked up before signal 10RB can be cleared by remote control. In other words, the east bound trafiic direction is established only when relay RBHR has picked up its armature to close its front contacts.

The circuits for supplying energy to relay RBHR may be traced from terminal B of the source over front contact 11 of relay LBHAR, front and back contacts 12, alternately, of relay ETP which is operating at the 180 code rate, through the first part or the second part, alternately, of the winding P1 of decoding transformer EDT to terminal N of the source. When pulses of energy are thus supplied, as just described, to the primary winding of transformer EDT, which is of the autotransformer type,

an alternating current energy is furnished at 180 cycles per minute through an obvious circuit to the 180 decoding unit, indicated on the drawing as 180DU, which is a resonant rectifier device already known to the art. The unit 180DU in turn supplies a pulsating direct current energy to the winding of relay RBHR sufficient to cause this relay to pick up. Relay RBHR will receive suflicient energy to pick up its armature only when energy at 180 cycles per minute is being furnished to the 180 decoding unit. With relay RBHR up, no further action is required to permit an eastbound train to enter the passing track 8BT except operation of the the remotely controlled relays controlling switch 9W and signal 10RB. Thus under normal conditions the apparatus is conditioned for eastbound trafiic.

If switch 9W has, by remote control, been moved to its reverse position, relay 9RKP will be energized, as previously described, and picked up. If relay IGRHS is now operated by remote control to put its contacts in their reverse position, also called their second position, the signal unit 10RB will receive energy through a circuit running from terminal B over front contact 13 of relay 9RKP, front contact 14 of relay 9TR, reverse contact 15 of relay 10RHS, normal contact 16 of relay IOLHS, front contact 17 of relay RBHR, back contact 18 of the left trafiic stick relay LS, and through the signal unit to terminal N of the source. Signal 10RB then will operate to display a proceed indication and a train may proceed from the single track west of the signal through section 9T, over switch 9W reversed, and into the passing siding. Signal 10RB displaying a proceed indication will cause the signal repeater relay 10RB? to be energized and picked up, relay 10RB? being controlled by a simple circuit easily traced and including a contact member 10RBY which is operatively associated with the signal 10RB, as indicated by a dotted line.

As has been described, with the contacts of the remote controlled relay 8LHS occupying their first position, en-

ergy at the basic 180 code rate is transmitted from a track battery at the master end through the rails of the track circuit of section 8BT. With the receipt of this coded energy at the basic code rate at the dependent end of section 8BT, traffic is established in an eastward direction through the section 8BT, and with the contacts of the second remote controlled relay 10RHS in their second position, the signal 10RB is cleared to permit a train to enter the section.

When the eastbound train accepts the signal 10RB and advances to occupy track section 8BT and shunts the track circuit, thus releasing in turn relays SEBTR and ETP, relay LBHAR is deenergized and after a short period releases. At this time energy supplied through a circuit from terminal B of the source over back contact 61 of relay LBHAR to the remote control apparatus (indicated only by a note on the drawing) causes an indication of occupancy of section 8BT to be transmitted to the control location in any of the usual and well-known manners. After the track section 8BT is again unoccupied and relay LBHAR energized and picked up, absence of energy at contact 61 will cause the transmission of an indication of unoccupied track section. As hereinafter described, the same action occurs for a westbound train, so that all occupancy or nonoccupancy indications originate at this end of the section.

After passage of an eastbound train through the section 8BT the apparatus will reestablish a normal condition as previously described, with a coded track current of the basic 180 code rate being transmitted from east to west and the section prepared for eastbound tratfic.

In order to permit a Westbound train to enter the passing siding at the east end over switch 7W reversed, several steps must be completed. After the switch 7W is reversed, the signal 8L3 must display a proceed indication to authorize the train to pass the signal and enter section 8BT. In order to do this, the established normal direction of traflic in section 8BT must be'cancelled and a new direction of traffic, which will be called reverse traffic direction, established from the east or master end to the west or dependent end. In conjunction with this change of traffic direction, signal 10RB at the west end must be prevented from displaying a proceed indication. If signal 10RB is already displaying a proceed indication, the reversal of traffic direction and the clearing of signal 8LB must be prevented. The method of accomplishing these matters will be described step by step in the following paragraphs.

When it is desired to reverse the traffic direction and permit a westbound train to enter the passing track, an operator, by remote control, causes switch 7W to be moved to the reverse position, thereby energizing relay 7RKP, which picks up, and deenergizing relay 7NKP, which releases. The circuits over which this action is accomplished are obvious and have been previously described. Relay 8LHS is also operated by remote control so that its armature moves to its reverse position, also called its second position.

Closing of the reverse, or second position, contacts of the remote controlled relay SLHS initiates an action which causes a pulse of energy of longer duration than any code pulse flowing in the track circuit to be superimposed on the coded energy of the basic 180 code rate which is then flowing in the track circuit. This is accomplished by the holding up of relay CTR through a series of controls established by a pulse initiating relay ZR, and its two pulse timing, slow release repeater relays Z? and ZPP.

The circuit for supplying energy to relay ZR may be traced from terminal B of the source over normal contact 19 of relay 8RHS, reverse contact 20 of relay 8LHS, front contact 21 of relay 7RKP, front contact 22 of relay ZPP, and through the winding of relay ZR to terminal N of the source. Relay ZPP is normally held up by energy through the circuit running from terminal B of the source over front contact 23 of relay ZP through the relay winding to terminal N of the source. Relay ZP in turn is normally held up by energy supplied over a circuit running from terminal B of the source over back contact 24 of relay ZR and code following back contact 26 of relay CTR through the Winding of the relay ZP to terminal N of the source. Relay ZP, by use of a resistor R4 in multiple with the relay winding, is made slow acting with a release period of approximately 0.8 second. This is sufficient time to bridge the off period of the coded energy at 180 code frequency received over the back contact 26 of relay CTR. When relay ZR picks up, relay ZP is initially held up by energy supplied through a stick circuit running from terminal B of the source over its own front contact 25 and back contact 26 of the relay CTR through the relay winding to terminal N of the source. When relay CTR is next energized, as previously described, by operation of the coder 180CT, it is then held up by energy through the circuit from terminal B of the source over front contact 25 of relay ZP, front contact 26 of relay CTR, front contact 27 of relay ZR, back contact 6 of relay LBHR, resistor R10, front contact 7 of relay CCR, through the winding of relay CTR, and over back contact 8 of relay SWBTR to terminal N of the source.

With relay CTR held up, a pulse of energy, of the nature of a longer code pulse, is supplied to the rails of section 813T over front contact 4 of relay CTR from battery SEBTB, as previously described. This long pulse of energy in the rails is limited or timed by the release time of relay ZP, which is approximately 0.8 second as previously stated, because the circuit supplying the energy to hold up relay CTR is opened at front contact 25 of relay ZP when that relay releases. Since relay ZP is deenergized as soon as relay CTR picks up, this longer pulse of energy blanks out two off periods of the 180 code and ceases at the end of the third on period.

This pulse of rail current, of 0.8 second duration, causes both the track relay at the west end and its repeater, relays SEBTR and ETP, respectively, to hold up. This action results, by various circuits, inthe picking up of the left traflic stick relay LS which in turn causes reverse coded energy to be fed into the rails by the hereinafter described operation of the code repeating relay RIR. Since it is this reverse code which causes the reversal of traific direction, various checks must be made to assure that conditions are proper for a westbound movement through the passing track. The manner in which the reverse code is initiated, and the various checks which are accomplished for safety reasons will be described in the succeeding paragraphs.

With both the track relay SEBTR and relay ETP held up by the long pulse of energy, of 0.8 second duration, received through the rails of the track circuit, relay LBHAR is then steadily energized over a circuit previously described and remains picked up but relay EBTP, being deenergized, releases after a short period. However, with relay ETP held up, pulses of energy are no longer supplied to transformer EDT, which in turn ceases to supply energy at 180 cycles per minute to the decoding unit 180DU, so that relay RBHR is 'deenergized. Although deenergized,'relay RBHR does not release during this period of 0.8 second due to slow release characteristics supplied by the rectifier in the decoding unit which acts as a snub on the relay winding. Release of relay EBTP and holding up of relay RBHR causes relay LS to be energized through a circuit passing from terminal B of the source either over front contact 28 of signal locking relay RMR and front contact 29 of relay 9TR, in series, or over front contact 30 of relay 9NKP; then over back contact 31 of relay RBP, front contact 33 of relay RBHR, back contact 34 of relay EBTP, and through the winding of relay LS to terminal N of the source. Relay LS then picks up its armature, closing its front contacts. When coding begins again at the end of 10 the long pulse of energy, and relay EBTP again picks up, relay LS isheld up by a stick circuit traced from terminal B of the source over its own front contact 35 and front contact 34 of relay EBTP, then through the winding of relay LS to terminal N of the source. With relay LS up the circuit for furnishing energy to the control unit of signal 10RB is opened at back contact 18 of relay LS. This prevents the clearing of this signal during the time the reverse traflic direction is being established and after it is established. An additional interruption of this signal circuit will be discussed hereinafter.

If signal 10RB had previously been cleared, relay 10RBP would have been energized and picked up as previously described. Since this would open the circuit supplying energy to relay LS at back contact 31 ofrelay 10RBP, relay LS could not operate and no further action would occur. Also, since relay RBHR does not release during this long pulse of energy, the proceed indication on signal 10RB would not be interrupted, Thus, since relay LS indirectly controls the transmission of the reverse code which reverses the traffic direction, it is evident that if the signal had been cleared for an eastbound move into section 8BT, traflic cannot be reversed.

In addition, a check is made to assure that the locking associated with signallORB is released and that the remote controlled relay, 10RHS, has its contacts in their normal, or first, position. This check is particularly required if switch 9W is reversed, releasing relay 9NKP, or if this apparatus were installed on a section of single track. Therelays RMR, 10DSR, and IDRHS are involved in this safety check, as will be described in the next paragraph.

The energizing circuit for relay LS is carried, as will be noted from a previous description, over front contact 28 of relay RMR to check that the locking associated with signal 10RB is released. Relay RMR is normally energized through a pickup circuit traced from terminal B of the source over normal contact 63 of relay IORHS, back contact 32 of relay 10DSR, and through the winding of relay RMR to terminal N of the source. Thus the contacts of the remote controlled relay 10RHS must be in their normal, or first position in order for the relay RMR to pick up. If switch 9W is then reversed and relay 9NKP released, or if we assume that this is a single track section with no switches, so that no energy is available over the front contact 30 of relay 9NKP, the energization of relay LS can occur only when relay RMR is picked up so that the pickup of relays LS is dependent upon the contacts of the remote control relay 10RHS being in their first position. Since the transmission of the reverse code, to be hereinafter described, is partly controlled both by relay LS and by the first portion of the circuit previously described for energizing relay LS and including front contact 28 of relay RMR, the reversal of trafiic at this west end also cannot occur unless these contacts of the remote controlled relay are in their first position. Relay RMR has also a stick circuit passing from terminal B of the source over back contact 64 of relay 'RBHR,front contact 65 of relay RMR, and through the Winding of the relay to terminal N of the source. This circuit is normally open at back contact 64 of relay RBHR, but is useful to prevent the interruption of established traffic in the event the remote operator inadvertently reverses relay MRI-IS after trailic direction has been reversed, and, as described hereinafter, relay RBI-IR has released.

However, all conditions being proper when relay LS picks'up, the initiation of a reverse code track current can then be accomplished. Energy is supplied to the primary winding P2 of impulse transformer RIT through a circuit passing from terminal B of the source either over front contact 28 of relay RMR and frontcontact 29 of relay 9TR in series, or over front contact 30 of relay 9NKP; then over back contact'31 of'relay 10RBP and front contact '36 of relay .LS;then either over front contact 37 I l of relay 8EBTR and through the upper half of winding P2, or over back contact 37 of relay 8EBTR and through the lower half of the primary winding P2, of transformer RIT, to terminal N of the source. When relay 8EBTR is operated by coded energy of any frequency received from the rails, pulses of direct current energy are then supplied to the primary winding P2 of transformer RIT,

with current flowing first in one direction and then the other through the winding. This induces a pulsating alternating current in secondary winding S2, with the current tending to flow in one direction when front contact 37 of relay 8EBTR opens and back contact 37 closes, and in the other direction when back contact 37 opens and front contact 37 closes. However, the secondary winding S2 of transformer RIT is connected through rectifier 38 to the winding of relay RIR, a biased code repeating relay, with the rectifier 38 poled so that the current is in the proper direction for relay RIR to operate momentarily only when the back contact 37 of relay 8EBTR closes.

Under these conditions, energy from track battery 8WBTB is applied to the rails of section SBT so that current flows from the positive terminal of this battery over front contact 39 of relay RIR, thence through the winding of relay 8EBTR in the direction from right to left, and over lead wire 3L to positive track rail 1; and from the negative track rail 2 over lead wire 4L through a limiting resistor to the negative terminal of battery SWBTB. A pulse of energy flows through the rails each time the relay RIR operates its armature momentarily to close its front contacts. The direction of flow of this current is such that relay 8EBTR will not operate on these pulses of energy. However, since relay RIR operates momentarily only when back contact 37 of relay 8EBTR closes, relay RIR operates only when relay 8EBTR is operating to follow a coded rail current of any code frequency transmitted through the track circuit from the east end.

It is to be noted that, when relay 8EBTR is held up by steady energy in the rails, or released for a period because of a track shunt, and steady energy is thus supplied to one or the other half, respectively, of winding P2, no voltage is induced in the secondary winding S2 and relay RIR will not operate. Also, since relay RIR operates when a back contact of relay 8EBTR is closed (relay 8EBTR deenergized), the pulse of energy supplied to the rails by relay RIR is then a reverse code pulse (a term known to the art) of the same relative polarity as the normal code. The first pulse of reverse code energy occurs immediately after the long pulse of energy ceases. The reverse code continues then at a code rate identical to that at which relay 8EBTR is operated, and which for several pulses after the long pulse of energy is of the basic 180 code frequency.

Receipt of a reverse code at the east end of section 8BT causes several actions to occur. First, a code detecting relay LBHR picks up. This in turn causes, through several interconnected circuits, the code transmitting relay CTR to operate at a lower code frequency than the basic 180 code rate so that the normal code rate in the rails is changed. The signal 8LB receives energy so that it operates to display a proceed indication. The signal repeater relay 8LBP picks up then to assure that conditions of reverse trafiic are not interrupted.

When the pulses of reverse code are received at the east end, relay 8WBTR is energized by current flowing from positive rail 1 through lead wire 1L through the relay winding from left to right, over back contact 4 of relay CTR, and through lead wire 2L to negative rail 2. Since this current is in the proper direction through the relay winding, relay 8WBTR operates at the code speed of the reverse pulses. Operation of relay 8WBTR causes the energization of an energy storage device comprising a resistor R and a capacitor C2 in series, through a circuit passing from terminal B of the source over front contact 40 of relay 8WBTR and through the storage'device to terminal N of the source. When relay 8WBTR releases, energy flows from said storage device in a circuit over back contact 40 of said relay through the winding of relay LBHR to terminal N of the source. Relay LBHR is thus energized and picks up. Relay LBHR is made slow release by rectifier 62 in multiple with its winding and holds up during the short time relay 8WBTR is energized by each reverse code pulse.

Relay LBHR picking up opens the stick circuit for relay LMR, which circuit extends from terminal B of the source over back contact 41 of relay LBHR, front contact 42. of relay LMR, and through the relay winding to terminal N of the source. Since the pickup circuit of this relay is already open at normal contact 43 of relay SLHS (previously described as being operated to its reverse, or second, position), relay LMR is deenergized and releases. As previously described, relay CCR is normally energized over multiple circuits traced from terminal B of the source either over front contacts 44 and 45 in series, of relays LMR and 7TR, respectively, or over front contact 46 of relay 7NKP; then over back contact 48 of relay 8LBP and through the winding of relay CCR to terminal N of the source. Since relay 7NKP was previously released when switch 7W was reversed so that front contact 46 is open, release of relay LMR and the resultant opening of its front contact 44 deenergizes relay CCR and it also releases.

After relay LBHR picks up, and prior to the release of relay CCR, a short on pulse of steady energy is supplied to the track circuit by relay CTR in a manner similar to that for the 0.8 second pulse. Energy through a circuit traced from terminal B of the source over front contact 6 of relay LBHR, resistor R10, front contact 7 of relay CCR, through the winding of relay CTR, and over back contact 8 of relay 8WBTR to terminal N of the source holds up relay CTR until relay CCR releases. This pulse is of very short duration, but even if relay EBTP, at the west end, should release, relay RBHR is still held up and relay LS will be retained by energy through its pickup circuit. The reverse coding will not be effected other than the possible overriding of one pulse. As Will be described hereinafter, a longer pulse of steady energy, generated in a similar manner, is used to cause the entire system to reset from an established condition of reverse tratfic direction to a condition of normal traffic direction. At the present time, however, this short pulse has no bearing on the general operation of the system, serves no useful purpose, and may be ignored.

Release of relay CCR supplies energy through a circuit from terminal B of the source over back contact 49 of relay CCR and through the winding of the code transmitter 75CT to terminal N of the source and the code transmitter 75CT begins to operate. Energy is then supplied over the same back contact 49 of relay CCR to the primary winding P3 of impulse transformer EIT alternately over front contact 50 of the code transmitter 75CT and through the upper half of winding P3, or over back contact 50 of the code transmitter 75CT and through the lower half of primary winding P3, to terminal N of the source. These pulses of energy in the primary winding P3 with the current alternately flowing in one direction and then in the other in portions of the winding cause an induced current in the secondary winding in a manner similar to that previously described for transformer RIT at the west end. Current thus induced in the secondary winding S3 of the transformer EIT flows to the relay CTR in the closed circuit traced from the lower end of winding S3 through rectifier 51, over back contact 7 of relay CCR, through winding of relay CTR, and over back contact 8 of relay 8WBTR to the upper end of winding S3, The various components of this circuit are so connected and the rectifier 51 so poled that the current through the winding. of relay in the proper direction to operate the relay only when back contact 50 of the coder 750T closes, so that relay CTR operates momentarily each time said back. contact 50 closes. Relay CTR is now repeating the operation of the coder 75CT, so that the relay armature operates to close the frontcontacts at the code rate of 75 times per minute. I i

' The coded energy now supplied to the rails over front contact 4 of relay CTR from battery 8EBTB in a manner previously described is of a distorted 75 code frequency, a lower code frequency, When relay SEBTR at the west endis operated by this coded energy of 75 code frequency, relay RIR also operates at the same code rate and the reverse code pulses likewise are transmitted at 75 code frequency. Operation of relay ETP. at 75 code frequency (repeatingthe operation of relay $E BTR continues to energize relays LBHAR and EBTP as described previously, and these relays remain picked up. Energy is still supplied to the decoding unit ISODU, but since the energy is now at 75 cycles per minute the energy supplied by the unit lfitlDU to relay RBI-IR is insuflicientto retain that relay and it releases.

The opening of front contact 17 of relay'RBHR interrupts at a second point the circuit for supplying energy to signal unit RB, the circuit having already. been opened when relay LS is picked up. This signal cannot now be operated to display a proceed indication even though relay ltlRHS might be operated to its reverse position with switch 9W reversed. Since the conditions at the east end, as described hereinafter, are now in order for signal SLB to operate, the preventing of operation of signal 10KB safeguards against. opposing moves. In addition, this latter break in the signal unit control circuit assures that, if at any time conditions at the east end are not proper for transmitting 180 code, even though trafi'ic' direction is not being reversed, the entering signal at the west end' cannot be cleared. As an example, such a condition might occur if, a switch engine was given special orders to occupy detector section II with switch 7W in the: reverse position without signal 8LB being cleared.

The special circuits, which include impulse transformers RIT and EIT, used to produce code repeating operation at the 75 coderate' by relays CTR and RIR provide two advantages. The normal and reverse code energy, respectively, of the 75 code frequency transmitted to the rails over contacts of these relays is distorted in form from that usually employed in track circuits. The length of all the code pulses of the 75- code rnte in this apparatus is such that they may be cascaded" through a cut section employing front contact repeating, and still be decoded satisfactorily. As shown in the upper righthand portion of Fig. 1b, the equipmentat the cut section, if required by' length of the trackcircuit, is of the simple front contact repeating, type, already known to the art, which; requires a minimum .of apparatus. This type of cut section cannot normally be used ina system employing a reverse code. At the same time, the combined on-time of the pulses of normal and reverse code is kept below 50%. Thisprevents the track storage current from becoming a limiting factor, and the track circuit may be as long aswhen only a normal code is used.

The operation of the apparatus at the cut section is, as indicated, simple and well known to the art.- Pulses of normal coded track current are received by relay EBTR over the rails ofsection 8BT from the master end of the stretch. Similar pulses ofcurrent are supplied to the rails of section ltlBT, which is formed when required by installing the insulated joints 3 at the cut section, from battery EBTB over the front contact of relay EBTR in series with: that battery. Since this contact is operated at a code ratecorresponding; to. that of the track current in section 813T, the'code pulses supplied to section 10BT have the same code rate and occur. at nearly the same time as those in section 8B1. Relay SEBTR at the dependent end of the siding is then operated, in the same manner as previously described, by the code pulses transmitted through section 10BT. However, the polarity of these normal code pulses from battery EBTB is such that relay WBTR at the cut section is held released. 7

When the conditions are such that reverse code pulses are supplied to the rails of section ltlBT at the dependent end, they are received at the cut section by relay WBTR. The code following operation of this relay causes similar reverse code pulses to be supplied to the rails of section 8BT. These pulses are supplied from battery WBTB through an obvious circuit, and are received from the rails at the master end by relay SWBTR. There is no difference in the resulting operation at the master end whether the reverse code is or is not repeated at a cut section.

When the reverse code energy at 75 code frequency is received at the east end of the track circuit and relay SWBTR operates following the code, relay LBHR remains energized and picked up as described previously. With front contacts of LBI-IR thus closed, energy is supplied to the unit of signal SLB through a circuit passing from terminal B of the source over back contact 52 of relay CCR, front contact 53 of relay LBHR, reverse contact 54 of relay SLHS, front contact 55 of relay 7RKP, front contact 56 of relay 7TR, and through the winding of. the signal unit to terminal N of the source. Signal SLB then operates to displaya proceed indication.

Actually, since relay LBHR was picked up by the'first two or three pulses of reverse code, which were of the code frequency, it was not necessary to have the code frequency changed to the lower rate in order to clear signal 8LB. However, it was better suited to consider the clearing of this signal at this point rather than previously. With signal SLB displaying a proceed indication, energy through a circuit from terminal B of the source over contacts SLBY operatively associated with the signal unit as indicated by a dotted line, and through the winding of relay 8LBP tov terminal N of the source causes this relay to pick up. Relay 8LBP is retained, when applicable, over its own front contact 57' by energy from terminal B of the source over either of the back contacts 58 or 59, in multiple, of relays LBHR and 7TR, respectively.

When relay ZP releases at the end of its 0.8 second release time, the opening of its front contact 23 deenergizes relay ZPP. Relay ZPP is made very slow release,

in the order of 8 seconds, by a timing unit, consisting of a resistor R6 and capacitor C3 in series, connected in multiple withits winding. When relay LBHR picks up, its front contact 60 closes a circuit in multiple with front contact 22 of relay ZPP and thus completes a circuit to retain relay ZR when relay ZPP releases. If, for any reason, such as a momentary track shunt, the long pulse of energy of 0.8 second duration is not received at the .west end of the track circuit, the reverse code will not be initiated. In this case, relay LBHR at the east end cannot pick up. Then the release of relay ZPP will de'energize relay ZR, by the opening of front contact 22 of. relay ZPP, since front contact 60 of relay LBHR will also be open. Release of relay ZR will energize relay 2?, over circuits described previously when next relay CTR closes back contact 26 during its operation at the 180 code rate. When relay ZP picks up, relay ZPP in turn is again energized by closing of front contact 23 of relay ZP, and relay ZPP picks up. Relay ZPP closes its front contact 22 and again energizes relay ZR, as previously described, since other conditions of this circuit have not changed. The various steps and actions previously described upon the initial request for a reversal of traffic direction now occur again and a second long pulse of energy of 018 second duration: is, applied to the rails of thetrack circuit to condition the system for a westbound movement. Thus, without additional action on the part of the remote operator, periodic pulses of 0.8 second duration will be supplied in an effort to clear signal 8LB until the signal is cleared or until the remote operator cancels the request.

When a westbound train enters track section SBT, the track circuit is shunted and relay 8EBTR at the West end ceases operation. Since relay ETP will also cease operation, relay LBHAR will be deenergized and will release, but relay EBTP will be retained, steadily energized over back contact 10 of relay ETP. Relay LS will also remain energized over the stick circuit including front contact 34 of relay EBTP and its own front contact 35. When relay LBHAR releases, energy is supplied from terminal B of the source over back contact 61 of relay LBHAR to the remote control apparatus to provide an indication of siding occupancy. Since the same circuit, as previously described, provided the occupancy indication for an eastbound train, it is seen that all occupancy indications for track section SBT are transmitted from this one end of the section.

During the time the westbound train occupies section 8BT coded energy is supplied to the rails at the east end in the manner previously described, by operation of relay CTR repeating a code transmitter. Since relay CCR remains deenergized because relay SLBP is held up by one of its stick circuits, the code frequency remains at the 75 code rate.

When the westbound train departs from the passing siding, if the remote operator has not requested by remote control a continuation of the westbound trafiic through section SET, the apparatus will automatically reset to re establish the normal or eastward traific direction. As will be described, this action occurs in several steps, each one depending upon the completion of the foregoing step. First normal and reverse coding at the 75 code rate is resumed. This causes a pulse of steady energy of relatively long duration to be sent from the east end. This steady pulse will first block and then cancel the transmission of the reverse code. Absence of reverse code changes the normal code back to the basic 180 code frequency and normal conditions arereestablished.

When the westbound train leaves section 8BT, energy at the 75 code rate is again received by relay 8EBTR. Operation of this relay again causes similar operation of relay ETP, which in turn energizes relay LBHAR and retains relay EBTP, in the manner previously described. However, not until the train clears the track section 9T and relay 9TR is energized and picks up, closing its front contact 29, is relay RIR energized over the circuit and in the manner previously described. Operation of relay RIR, controlled by relay 8EBTR, will again transmit the reverse code at the 75 code rate through the rails to the east end of the track circuit.

Receipt of the reverse code at the east end of the track circuit causes relay SWBTR to operate, repeating the code rate which, as previously described, energizes relay LBHR which again picks up. Since relay 7TR is already picked up and its back contact 59 open, opening of back contact 58 of relay LBHR deenergizes relay SLBP which releases. Closing of back contact 48 of relay SLBP again energizes relay CCR which picks up. This is possible even if switch 7W is still reversed and relay 7NKP released, because relay LMR has been picked up by energy over an obvious circuit originating at normal contact 43 of relay SLHS which returned to its normal, or first position, in the usual manner for such remotely controlled relays in response to the Westbound train passing signal 8LB. The circuit then for energizing relay CCR is the same as previously described. "It should be noted that, since we had assumed that the switch was reversed, the energizing of relay CCR was dependent, through relay LMR, on the contacts of the remote controlled relay SLHS being in their first position.

With relay LBHR up, the picking up of relay CCR supplies steady energy to relay CTR through a circuit traced from terminal B of the source over front contact 6 of relay LBHR, resistor R10, front contact 7 of relay CCR, through relay winding of relay CTR, and over back contact 8 of relay 8WBTR to terminal N of the source. With relay CTR held in the up position, a relatively long pulse of steady energy is transmitted to the rails from battery SEBTB over front contact 4 of relay CTR. The direction of this current is such as to hold relay SWBTR in the released position. Also, since receipt of the steady pulse at the west end of the circuit will hold relay 8EBTR up, and thus stop the operation of relay RIR, no reverse code will then be transmitted to operate relay BWBTR. With relay SWBTR released, relay LBHR is energized only from the storage unit, resistor R5 and capacitor C2, as previously described, and will release after 2.5 to 4.0 seconds. Release of relay LBHR will terminate the long pulse of steady energy by returning the control of relay CTR to energy supplied over front contact 5 of the coder 180CT, which is again operating from energy supplied over front contact 49 of relay CCR. However, the length of the long pulse of steady energy is sufficient to cause relay EBTP at the west end to release after being deenergized when relay ETP is held up. Release of relay EBTP opens the stick circuit for relay LS at front contact 34 of relay EBTP, and since relay RBHR was previously released, upon the shift to the code rate, and its front contact 33 opened, relay LS is deenergized and releases.

When energy at the 180 code rate is again supplied to the track circuit, upon the release of relay LBHR, the system is restored to its normal condition as previously described and the normal or eastbound traffic direction is reestablished. If, for any reason, such as a momentary track shunt, the long pulse of steady energy is lost, reverse code will again be applied to the rails at the west end when the shunt is removed and coded energy is supplied from the east end. Relay LBHR will then pick up again, and the pulse of steady energy will be repeated. This cycle will continue until the system is reset.

From the foregoing complete description of the operation of the signal system for the passing track, in which the establishment of traffic in first one direction and then in the other was discussed, it can be seen that at no time was there need for line wire between the two ends of the track section. The function of the apparatus at both ends was dependent only on energy transmitted through the rails of the track section. By a proper selection of code rates, with pulses of steady energy used to start certain sequences of operation, it was possible to establish a normal direction of traflic, to reverse the direction of trafiic, to prevent the clearing of signals for simultaneous opposing moves into the section, and to reset the system from the reverse traffic direction to normal trafiic direction. It is evident that the system can also be used for any section of single track where it is desired to have trafiic move in either direction, especially if traffic in one direction would predominate.

As previously mentioned, a possible use for this system is to control the return of helper locomotives, in multiple track territory, against the normal direction of traffic from the point of cut off from the helped train to a crossover to the proper track for their return movement. This distance is often only one track section in length. In such an installation, it would be desirable to provide three indications on the signal governing train movements in the normal direction, as herein described, the signal 10RB. This can be done by adding another code transmitter to provide a third code rate, such as the well-known code frequency. With trafiic established in the normal direction, the selection between the code rate, for a clear indication on signal 10RB, and the 120 code rate, for a caution indication, would be governed in a usual manner by the traffic conditions in advance of this track section. If it is also desired to provide three indication signalling reverse code pulses of the polarity described: in the previous discussion. could be used to provide a caution, or low speed indication on signal 8LB. Byslightly modifying the circuits, reverse code pulses of the opposite. polarity could be used to provide aclear, or medium speed indication on signal 8L8. As before, selection between the two polarities would be governed, by the traffic conditions in advance of this track section, in the direction of the reverse movement.v None of the previously discussed safety features need ,be sacrificed in providing this three indicationsignalling in either direction. The system is thus not limited to governing the entry of trains intoapassing siding;

It is also evident that the system may be operated by remote control from a distant location. If added to an. existing or planned CT C installation to also provide control of a passing. track, no additional control apparatus would be required at either field location'sincethe con trol' functions for signals and switches would already exist, and since the occupancy indication for the siding. is alwaysprovided from the dependent end, the indication function already available'at one end could 'be used.

Although I have herein shown and described only one form of railwaysignal apparatus embodying my invention,

it is understood that various "changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention. Y

Having thus described my invention, what I claim is:

1. In a railway signal system for at times reversing traffic on a section of railway track over which traflic normally moves in one given direction, means for remotely controllingthe direction of tratfic through the section comprising, a first direction establishing control relay located at one end of said section, a second. direction.

establishing control relay located at the other end of said section, each said control relay having contacts which normally occupy a firstposition and which may be operated to a second position, a first code following relay at said one end, a second code following relay connected to the rails at said other end, each said code following relay having contacts biased to' a first position and operated to a second position only when the relay is energized with current of a given polarity, a code transmitter at said one end operable to provide a predetermined code frequency; an energy supply means at said one end connected to the rails of said sectionand including a source of direct current, a contact controlled by the operation of said code transmitter, and the winding of said first code following relay; said supply means being effective to normally supply to the rails of said section coded energy of said predetermined code frequency, saidsource being so poled that said first code following relay is nonresponsive .to-s'aid coded energy, means controlled-by said second code following relay and responsive to said. coded energy to establish a normal direction of trailic from said other end to said one end, a first means at said one end includ ing a slow acting relay andconnected; to said supply means, said first means operative when the contacts of said first control relay are in their second position to superimpose on said coded energya pulse of energy of longer duration than that of any code pulse on said track, a second means at said other end including another relay and controlled by said second code following relay, said second means responsive to said. longer pulse of energy to energize said other relay if the contacts of said second control relay are in their first position, another energy supply means at said other endrincluding another direct current source and connected to the rails, of said section, said other supply meanas being responsive to the energization of said other relay to supply. reverse code energy to said rails, said other source being so poled that said first code following relay is'responsive to said reverse code 18 energy to establish' a reverse-direction; ofijtrafiic-fronrsaid one end to-said other endofsaid's'ection.

2. In ara-ilway signal system forat" times; reversing traific on a section, of rail-way track over which t-rafiic normally moves in one given, direction, means for re motely controlling; the directionwof traffic through the section comprising, a first direction, establishing control relay located at a first end of said section, a second direction establishing control relay located at a second end of said section, each said control relay having: contacts which normally occupy afirst position and which are operable to a secondposition, atfirst code following relay at said first end, a second code following relay connected to the rails at said secondend, each. said codenfollowing relay having contacts biased to a first position: and operated to a second. position only whenthe relay is ener gized with current of a given polarity, a coding means at said first end for at times supplying coded current of a first code frequency. and for at. other times, supplying coded. current of a second code frequency; a.- first energysupply means connected tothe section rails at said first end and including in series a source of direct current, a code repeating contact normally responsive to code of said first code frequency, and the winding of said first code i following relay; said first supply means being effective to normally supply coded energy to the rails so poled that said first code following'rel'ay isnonresponsive to that coded energy, saidsecond code following relay being responsive to the coded energy normally supplied to the rails, detecting means controlled by operation of said second codefollowing relay to establish a normal direction of trafiic from said second end to said first end, a first means at said first end including a slow acting relay connected to said first. supply means, said first means op erative when contacts of said first control relay are in their second position to superimpose upon the coded energy normally supplied to the rails-a pulse of energy of longer duration than, that of any code pulse on said track, a, second means at said second end including an impulse transformer and an impulsetrelay, said second means being responsive to said longer'pulse of energyrto cause said impulse relay to repeat the subsequent code following operation of said second code following relay, a second supply means connected to the rails at said second'end including another direct current source and a contact of said impulse relay to supply reverse code energy to said'section, saidother source being poled so that said first code following relay is responsive to said reverse code energy to establish trafiic in a reverse direction from said first end to said second end, and a, third means responsive to the operation of said first code following relaywhen contacts of said first control relay are in their second position to make said code repeating contact responsive to code of said second code frequency to maintain said reverse traffic direction.

3. Means for at times reversing traffic over a stretch of railwaytrack divided into a plurality ofsections including an intermediate section having at a first end thereof a short first section and at a second end thereof a short second section, trafiic normally moving from said second section toward said first section, comprising a first direction establishing control relay located at said first end of'said intermediate section, -a second direction establishing control relay located at said second end-of said intermediate section, each said control relay having contacts which normally occupy a first position and which are operable to a second position, an energy supply means connected to the rails at said first end and operable to normally supply coded energy of a predetermined code frequency if the contacts of said first control relay are in their first position, a first code following relay connected to the rails at said first end and a second code following relay connected to the rails at said second end offsaid intermediate section, said first code following relay. beingnon-responsiye to said coded energy, said second code following relay being responsive to said coded energy to establish a normal direction of traflic through said stretch from said second section to said first section, a first means including a slow acting relay at said first end connected to said supply means and operative when the contacts of said first control relay are in their second position to superimpose on said coded energy a pulse of energy of longer duration than that of any code pulse on said track, another energy supply means connected to the rails at said second end, said other supply means being controlled by said second code following relay and responsive to said longer pulse of energy if the contacts of said second control relay are in their first position to supply to the rails of said intermediate section reverse code energy, said first code following relay being responsive to said reverse code energy to establish a reverse direction of traffic through said stretch from said first section to said second section.

4. Means for at times reversing the direction of trafiic over a section of railway track over which traific' normally moves in one given direction, comprising afirst direction establishing control relaylocated at one end of said section, a second direction establishing control relay at the other end of said section, each control relay having contacts which normally occupy a first position and which may be operated to a second position, an energy supply means normally including a first coding means connected to the rails at said one end of said section and operable to normally supply coded energy of a first code frequency if the contacts of said first control relay are in their first position, a first code following relay connected to the rails at said one end and nonresponsive to energy from said supply means, a second code following relay connected to the rails at said other -end, said second code following relay being responsive to the coded energy normally supplied to the rails to establish a normal direction of traflic from said other end to said one end, a first means at'said one end including a slow acting relay connected to said supply means, said first means operative when contacts of said first control relay are in their second position to superimpose upon said coded energy normally supplied to the rails a pulse of energy of longer duration than that of any code pulse on said track, a second means connected to the rails at said other end, said second means beingcontrolled by said second code following relay and responsive to said longer pulse of energy to initiate the supply of reverse code pulses to the section rails, said first code following relay being responsive to said reverse code pulses to establish a reverse direction of traific through said section from said one end to said other end, and other coding means at said first end including a code control relay responsive to the operation of said first code following relay if contacts of said first control relay are in their second position to control said supply means to transmit to the section rails coded energy of a second code frequency to maintain said reverse traflic direction.

5. Means for at times reversing the direction of traffic over a section of railway track over which tralfic normally moves in one given direction, comprising a first signal located at a first end and a second signal located at a second end to govern train movements into said section, a first direction establishing control relay located at said first end and a second direction establishing control relay at said second end of said section, each control relay having contacts which normally occupy a first position and which are operable to occupy a second position, an energy supply means including a first code transmitter connected to the rails at said first end of said section and operable to normally supply coded energy of a first code frequency if the contacts of said first control relay are in their first position, a first code following relay connected to the rails at said firstend and nonresponsive to energy from said supply means, a second code following relay connected to the rails at said second end, 'said 20 second code following relay being responsive to said coded energy normally supplied to the rails to establish a normal direction of trafiic from said second end to said first end, a signal control means including a decoding means at said second end controlled by said second code following relay, said signal control means being responsive to coded energy of said first code frequency when the contacts of said second control relay are in their second position to cause said second signal to display a: proceed indication, trafiic reversing means including a slow acting relay at said first end connected to said supply means, said trafiic reversing means being operative when the contacts of said first control relay are in their second position to superimpose on the coded energy normally supplied to the rails a pulse ofenergy of longer duration than that of any code pulse on said track, a coding means connected to the rails at said second end and controlled by saidsecond code following relay, said coding means being responsive to said longer pulse of energy to initiate and to transmit a reverse code if the contacts of said second control relay are in their first position, said first code following relay being responsive to said reverse code to establish traffic in a reverse direction from said first end to said second end, other signal control means including another decoding means controlled by said first code following relay, said other signal control means being responsive to said reverse code when the contacts of said first control relay are in their second position to cause said first signal to display a proceed indication, a second code transmitter responsive to the operation of said other signal control means to control said energy supply means to transmit to the rails coded energy of a second and lower code frequency, circuit means at said second end controlled by said decoding means and respon sive to coded energy of said second code frequency to hold saidsecond signal at stop, other circuit means at said first end responsive to said reverse code when the contacts of said first control relay are in their first position to superimpose upon the coded energy of said second code frequency a long pulse of steady energy, reset means controlled by said second code following relay and responsive to said long pulse of steady energy to halt transmission of said reverse code, and other reset means effective when said first code following relay is not following said reverse code and the contacts of said first 'control relay are in their first position to restore the transmission to the section rails of'coded energy of said first code frequency, thereby reestablishing said normal direction of traflic'.

6. Means for at times reversing the direction of traffic over a stretch of railway track over which traffic normally moves in one given direction, said stretch being divided into a plurality of track sections including an intermediate section having at a first end thereof a first section and at a second end thereof a second section, comprising a first signal governing tratfic movement into said stretch at said first section, a second signal governing trafiic movement into said stretch at said second section, a first direction establishing control relay at said first end and a second direction establishing control relay at said second end of said intermediate section, each. said control relay having contacts which normally occupy a first position and which may be remotely controlled to occupy a second position, a first track relay connected to the'rails at said first end of said intermediate section and operated by energy supplied over the rails of said section, a second track relay connected to the rails at said second end of said intermediate section and operated by energy supplied over the rails of said section, coding means connected to the rails at said first end of said intermediate section for supplying coded energy of a basic code frequency if the contacts of said first control relay are in'their first position, said coded energy being effective to operate only said second track relay to estab liSh-a normal direction'of trafiic through the said intermediate section and through said stretch of railway from said second section to said first section, decoding means at said second end responsive only to the code following operation of said second track relay at said basic code frequency when the contacts of said second control relay are in their second position to cause said second signal to display a proceed indication, circuit means at said first end of said intermediate section effective when contacts of said first control relay are remotely controlled to their second position to superimpose upon said coded energy a pulse of energy of longer duration than that of any code pulse on said track, other coding means at said second end controlled by said second track relay and responsive to said longer pulse of energy if the contacts of said second control relay are in their first position to initiate the transmission through the rails of a reverse code as soon as said longer code pulse ceases, said first track relay being responsive to said reverse code to establish a reverse trafi'ic direction from said first section to said second section, other decoding means at said first end responsive to the code following operation of said first track relay when the contacts of said first control relay are in their second position to cause said first signal to display a proceed indication and to change the code rate of said coded energy from said basic code frequency to a lower code frequency to prevent said second signal from displaying a proceed indication, said other decoding means when contacts of said first control relay are in their first position being responsive to'said reverse code to superimpose a long pulse of steady energy of duration longer than that of any code pulse on said track upon said coded energy of said lower code frequency, reset means controlled by said second track relay and responsive to said long pulse of steady energy to halt transmission of said reverse code, other reset means effective when said first track relay is not being operated by said reverse code and the contacts of said first control relay are in their first position to restore transmission to the rails of coded energy of said basic code frequency to reestablish said normal direction of traffic, and circuit means responsive to said second track relay to transmit to a remote location an indication of nonoccupancy of said intermediate section when coded or steady energy is received by said second track relay and an indication of occupancy when no energy is received by said second track relay.

7. In a railway signal system for at times reversing the direction of traific on a section of railway over which traffic normally moves in one given direction, said section having at one end thereof a first wayside signal and at the other end thereof a second wayside signal, each said signal governing the movement of a train into said section at its respective end; means for controlling the 22 operation of said signals to permit the movement of trains into said section with provision for preventing simultaneous opposing moves, said means comprising, a track circuit including the rails of said section, a first code following track relay at said one end, and a second code following track relay at said other end; said means further comprising at said one end, an energy supply circuit including a code transmitter and a source of energy connected to said track circuit to normally transmit coded track energy of a basic code rate to allow said second signal to display a proceed indication, a circuit arrangement including slow acting relays to superimpose at selected times on said coded track energy a pulse of energy longer in duration than any code pulse on said track, another circuit arrangement including another code transmitter and other relays associated with said first track relay to receive a reverse code through said track circuit from said other end, said other circuit arrangement being responsive to said reverse code to permit operation of said first signal to display a proceed indication and to change the code rate of said coded track energy from said basic code rate to alower code rate, a further circuit to superimpose at other times a long pulse of steady energy of duration longer than any code pulse on said track on the coded track energy of said low code rate to permit said signal system to reestablish normal conditions; said means further comprising at said other end, decoding circuits associated with said second track relay and responsive to said coded track energy of said basic code rate to normally permit said second signal to display a proceed indication, a feed-back circuit arrangement connected to said track circuit and responsive to said longer pulse of energy at said selected times to initiate the transmission of said reverse code through said track circuit, other circuits responsive to said coded track energy of said low code rate to prevent the operation of said second signal while maintaining said reverse code, reset circuits responsive to said long pulse of steady track energy at said other times to halt the transmission of said reverse code to cause the system to reset to normal condition; and an indicating circuit responsive to the receipt or nonreceipt of track energy to eifect an indication of nonoccupancy, or occupancy, respectively, of said track section.

References Cited in the file of this patent UNITED STATES PATENTS 2,353,421 Staples July 11, 1944 2,357,519 Judge Sept. 5, 1944 2,393,135 Agnew Ian. 15, 1946 2,561,956 Staples July 24, 1951 2,617,014 Judge Nov. 4, 1952

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