US2292967A - Railway traffic controlling apparatus - Google Patents

Description

Aug. ll, 1942.`

J. M. PELIKAN RAILWAY TRAFFIC CQNTROLLING APPARATUS `Filed Dec. 17,v 1940' 2 sheets-sheet 1 Aug.y 11, 1942.

J. M. PELIKAN RAILWAY TRAFFIC` CONTROLLING APPARATUS u .hm www@ NAS@ N A m N 2 Sheets-Sheet 2 Filed Dec. 17, 1940 E mw @M f l gNToR lian H/.s' ATTORNEY Patented Aug. 11, 1942 RAILWAY TRAFFIC coNTRoLLING APPARATUS John M. Pelikan, Pittsburgh, Pa., assigner. to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania `Application December, 17,1940, serial No. 370,433

. impractical. My present invention is van improvement on the invention disclosed in my -copending application SerialNo. 367,352, .filed on November 27, 1940, for Railway traffic controlling apparatus, now Patent No. 2,251,689, issued August 5, 194:1. i i

One object of my invention is to provide a coded track circuit system for two-direction signaling on a single track without employing control line wires. Another object of my invention is to provide a system of the above character, which provides broken-down rail joint protection and in which 4traffic cannot be falsely set up in both directions at the same time by stray currents. Other objects, purposes and features of my invention will be. apparent from. the de-- scription which follows.

I accomplish the foregoing objects by providing each track circuit with two polarized code following track relays,A one at each end of the associated track circuit, so arranged and connected that each relay operates asa track relay only for its proper direction of traffic. I establish traffic direction in accordance with the polarity of the coded track current and employ directional stick relays for permitting following traiiic movements and for preventing the set-up of confiicting routes. By employing code, I'provide a plurality of signal indications which permit following moves `through the single track stretch to be easily and safely made.

I shall described one form of apparatus embodying mylinvention, and shall then point out the novel features thereof in claims.

Figs. la and 1b ofthe accompanying drawings when placed end to end with Fig. 1a at the left, are a .diagramamtic view showing a stretch of single track railroad equipped with apparatus embodying my invention.

Referring to the drawings, the stretch of single track between the two passing sidings at locations D and E is divided by means of insulated rail joints -2 into a numberV of track circuits such as 5T, 4T, TT, and 8T. Entry into each of these track circuits is governed by a wayside signal located at the entering end of the track circuit for the particular traic direction. At F is a cut-section location which merely subdivides the section of track between signals 4 and '8 into two track circuits for the purpose of `providing improved track circuit operation.

Each eastbound track circuit is provided with an eastbound code following track relay at the entering end designated with a prefix corresponding to the associated track circuit, andwith a normally disconnected source of track circuit current at the leaving end. Each westbound track circuit includes. the, rails .of the eastbound track circuit but isprovided with its own westbound code following track relay at the entering end for that direction and with a normally disconnected source of current at the leaving end. The track relays are of the biased two-position polarized type which Ypick up whenl energized with current of one polarity but which remain in the released position to which they are biased when current is 'discontinued or when current of the other polarity is supplied thereto. The purpose in maintaining the track circuit sources normally disconnected is to economize track battery, these sources becoming connected in response to the action taken bythe operator or operators in setting up the apparatus for a trafc move in one or the other direction over the single track stretch.

At each signal location there is a suitable code transmitter CT which may be of the motor driven type and which supplies a or '75 coder by intermittently closing certain contacts designated as .|20 and 15, respectively, on the drawings at therate of 120 or 75 times 'per minute. Looking at location E, for example, and signal I0 which is shown at stop, the coder CTE which is energized from a source of current having the terminals B-C causes the flashing operation of the eastbound flashing relay IUEFR at a rate of either 120 or '75 times per minute, depending on the energized or deenergized condition of the home relay IDI-I for signal l0 which controls contact 42 in the circuit for relay IBEFR. Since the signal lil is at stop, the home relay IDI-I will be deenergized and the back point of contact 42 will be closed so that relay IUEFR operates at '75 code, it being assumed that the traffic lever Il has been moved to its normal or N position for an eastbound traflic move so that its N `contact is closed and the circuit for relay IIJEFR is therefore complete. Should signal I0 be occupying either the caution or the clear. position, the front point of contact 42 of relay IDH would then be closed so that relay IIIEFR would be operating at a rate of 120 times per minute. In order to simplify the disclosure as much as possible and make the circuits easy to follow, contact N of traflic lever II, contacts |20 and 15 of coder CTE, as well as contact 42 of relay IUI-I are shown removed from the apparatus by which they are operated, but in each case these contacts are clearly identied by the function which operates them. The same is also true of other contacts in the drawings, which for simplicity are identified by the relay which operates them rather than being shown in physical proximity to such relay.

Coding of the track circuit current itself is performed by the associated flashing relay for the established trafc direction, and response of the track relay to this code causes operation of certain decoding relays which control the signal indication and which code the adjoining,

track circuit so that relaying of the code will automatically continue from track circuit to track circuit until the headblock signal location for the desired traffic direction is reached. VAt location E, coding of the track circuit 8T is performed over the front point of contact 6 of relay IUEFR, which periodically connects the track battery TB across the rails.

Looking next at location 1-8, the code following action of the eastbound track relay SETR in following 120 code will maintain the distant relay 1-8DR energized by virtue of the resonated transformer-rectifier circuit which is tuned to pass impulses of 120 code but not 75 code. The energizing circuit for relay 1-8DR may be traced from one terminal B, over the front point of code following contact I2 of relay SETR, front contact I3 of the check relay 1--8CK, wire I4, and front contact I5 of the home repeater relay BEHP, to the tuned transformer and terminal C. Relay 1-8DR has a sufcient release interval to bridge the impulses of the 120 code. The check relay 1-8CK will be maintained energized on either |20 or 15 code over an obvious circuit which includes the back point of the periodically operating contact I2 of relay BETR and the constantly closed back contact I6 of theropposing track relay 1WTR.

Relay 8EI-IP is merely a repeater of the home relay 8EHR and is maintained energized over the front contact I 1 of the latter relay. Relay SEHR is maintained energized on either 120 or 75 code over the front point of contact I2 of relay GETR and front contact I3 of relay 1-8CK. The sequence of operations beginning with the code following action of relay SETR is accordingly as follows: pick-up of relay 1-8CK (if this relay has not previously been picked up) pickup of relay SEHR; pick-up of relay 8EHP; and finally, pick-up of relay 1-8DR. It will be understood that all of these relays (except 1-8DR which responds only to 120 code) are so designed as to remain picked up whether the code which is effective inthe track circuit BT is 120 or 75. The home relay 1WHR for the west-bound signal Twill obviously be deenergized because its circuit will be open at the front point of ccntact I6 of the westbound track relay 1WTR. Accordingly, the repeater 1WHP will also be deenergized. The Westbound track relay BWTR at the other end of track circuit 8T will not be operated by the discharge of any stored energy in the track resulting from the track circuit code because such energy will be of wrong polarity for pick-up of relay BWTR and will merely aid in maintaining this relay released.

Under the above conditions, signal I will be at stop, its red lamp being illuminated over an obvious lighting circuit which includes the terminals EN and EB of a suitable lighting source and back contact I8 of relay 1WHP. If the code is 120 (so that relay 1--8DR is up) signal 8 will be at clear, with the green lamp energized over the front point of contact I9 of relay 1-8DR and the front point of contact 25 of relay BEHP. If the code is so that relay 1-8DR is released, signal 8 will be at caution, as shown, with the yellow lamp illuminated over the back point of contact I9 and the front point of contact 20.

At the location 1 8, I also employ directional stick relays aEsR) and 'IWsR but since the operation of these relays comes into play only during the passage of a train through the section, this operation will be described hereinafter.v

I shall next describe how the code following operation of track relay 8ETR causes code to be relayed into section 1T and into the remaining sections to the left for setting up an eastbound route over the single track stretch.

If the track relay SETR is following code, then this same code will be relayed into track circuit 1T by virtue of the operation of flashing relay 8EFR. This relay has a 120 code operating circuit which includes one terminal B, wire 2l, contact |20 of coder CTS-I0, wire 22, front point of contact 23 of relay 8EHP, and the winding of relay BEFR, to the other terminal C of the source. This 120 code operating circuit is effective whether relay SETR is following 120 or 75 code because relay BEHP will be picked up in either case, thus completing the circuit. If, however, a train is occupying the track circuit 8T, then the operating circuit for relay SEFR will include contact 'I5 of coder CTB-40, front contact 24 of directional stick relay 8ESR, and the back point of contact 23 of relay BEI-IP which will now be deenergized. The directional stick relay BESR will have been picked up as a result of the entry of the train into track circuit 8T, as will be explained hereinafter, thus closing the 75 code circuit for relay 8EFR.

The periodic closing of front contact 25 of relay SEFR will impress either 120 or 75 code from the track battery TB across the rails of track circuit 1T. Since location F is a cut section location, the 120 or 75 code will be repeated into the adjoining track circuit 4T because of the code following response of the eastbound track relay 1ETR andthe inclusion of front contact 26 of this relay in the code supply circuit for track circuit 4T. As a result, the eastbound track relay 4ETR will follow either 120 or 75 code, as the case may be. If the code is 12'0, the group of relays 4-5CK, 4EHR, 4EHP, and 4-5DR will all be energized, in the same manner as described for the corresponding relays at location 1 8. Accordingly, eastbound signal 4 will indicate proceed andwestbound signal 5 will indicate stop.

Code will be relayed into track circuit 5T in an identical manner with that described for track circuit 1T, so that the eastbound track relay 5ETR. will follow either 129 or 75 code according as the stretch of track between signals 4 and 8 is unoccupied or occupied, respectively.

At each end of the single track stretch I have provided a traic leve-r having a normal position N for eastbound traffic and a reverse position R nal lever having a neutral position `1L in which no contacts are closed; a right-hand position r corresponding with eastbound traflic; and a lefthand position l corresponding with westbound traiilc. These signal levers are designated as 2 l and 9 at the ends D and E, respectively, of the single track stretch.

Having described the individual apparatus and its operation at the diierent locations, I shall now assume that with the stretch D-E in its normal or unoccupied condition as shown, it is desired to set up the apparatus for an eastbound traffic move. To do this, each of the traiiic levers I and II is moved to the N positiondunless the last movementrwas eastbound, in which case the traffic levers will already be occupying the N position), and the signal lever 2 is then moved to the 1' position. At the leaving end E of the stretch, relays SCK, SW1-IR, and SDR will all be deenergized because the energizing circuit, for each of these relays includes the reverse contact R of traflic lever II which is now open. Accordingly, the opposing-signal L9 will indicate stop, its red lamp being lighted over the back contact 28 of relay SWR1-I. The normal contact N of lever II will, as described hereinbefore, close the '15 code circuit for flashing relay IUEFR so that 75 code will be impressed on the track circuit 8T over the front point of contact 6 of relay IUEFR. The reason why '75 code and'not 120 code is supplied to section 8T is that a train is shown occupyingv the section immediately in advance of the single track stretch D--E, so that signal I8 is at stop and its home relay IUI-I is deenergized.

From this point on, the sequence of operations up to the response of track relay ETR will be clear from the previous description. Track circuits 1T, 4T, and 5T will all be receiving 120 code; signal 4 will indicate proceed; and signal B will indicate caution (since 75 code has been assumed in the track circuit 8T due to the presence of a train just beyond location E). The opposing signals 1 and 5 will obviously be at stop.

Looking now at the entrance end D, the check relay 20K will be picked up over a circuit which includes the normal contact N of traffic lever I, the right-hand contact r of signal lever 2, and the back point of contact 29 of periodically operating relay ETR. Relay ZEHR will accordingly be picked up overthe contacts N and r of levers I and 2, in series, front point of contact 29 of relay 5ETR, and front contact 3G of relay 20K. Since relay BETR is responding to 120 code, the decoding relay 2DR will also be picked up so that the entering signal R2 will then indicate proceed, its green lamp being lighted over the front contacts 3l and 32 of relays ZEI-IR and 2DR, respectively, in series. Relay IFR will, of course, not be flashing but will remain constantly deenergized since its energizing circuit will be open at the reverse contact R 0f traffic lever I. It will be clear,

therefore, that relay EETR will remain constantly connected across the rails, over the back contact 33 of relay IFR. With'the clearing of signal R2 by movement of the signal lever 2 to its r position, eastbound traffic may proceed into the single track stretch.

I shall next trace the progress of an eastbound train through the section, the traffic levers I and II having been placed at normal, signal lever 2 being to the right, and signal R2 indicating proceed. As the train enters the track circuit 5T, the track relay EETR becomes released, causing relays ZEHR and 2DR to release so that signal R2 goes to red. Relay 2CK will remain energized and the operator should .then place the signal lever 2 in its neutral or n' position in order to drop out relay ZCK so as to prevent any possibility cf signal R2 becoming cleared .after the train has vacated section 5T and the directional stick relay 4ESR has picked up.

. When the train passes signal 4 which has'been at green, directional stick relay 4ESR will pick up and will remain up thereafter until an opposing route is established. The pick-up of 4ESR occurs as follows. The opposing directional stick relay 5WSR is, of course, released and prior to the entry of the train into section 4T, relays 4EHR and 4EHP are both picked up. The shunting of track relay 4ETR will release 4EI-IR, but for a short interval thereafter, relay 4EHP will remain picked up because of its slow release interval. Accordingly, 4ESR will have a pick-up circuit which includes back contact 34 of SWSR, back contact 35 of 4EHR, and front point of contact 36 of 4EHP. A stick circuit is now closed for relay 4ESR over back contacts 34 and 35 of relays BWSR and 4EHR, wire 31, and front contact 3B of relay 4ESR. The subsequent release of relay 4EHP closes a second stick circuit for relay 4ESR over back point of contact 36 of relay 4EHP, wire 31, and front contact 38 of relay 4ESR.

The pick-up of 4ESR prepares a '75 code circuit for flashing relay 4EFR so that as soon as 4EHP releases, this flashing relay will be energized over the 75 code contact of coder CTL-5, front contact 39 .of relay IIESR and back contact 4B of relay 4EHP. The operation of relay IIEFR willl begin the coding of the track circuit 5T at 75 code over the front point of contact 4I so thatthe response of relay EETR to this code as soon as the train vacates section 5T will cause signal R2 to go to yellow in order to permit a following train to enter the single track stretch during occupancy thereof by the rst train.

During the time that the train occupies the sections 4T and 1T, relay 4ESR will remain picked up and relay 4EI-lR will remain released. Signal 4 will be at stop. As soon as the train fully vacates section 1T, the coding action of relays 1ETR and 4ETR, in turn, followed by `pickup of relays 4EHR and 4EI-IP will cause release of the stick relay 4ESR. Since relay 4ETR is following '75 code, relay 4EHP will be up and relay 4--5DRv willlbe down, so that signal 4 will indicate yellow or caution at this time. The manner in which 75 code was supplied to section 1T when the train passed beyond signal 8 and shunted relay SETR will be clear from the description of the application of 7 5 code to section 5T when the train passed signal 4. That is, the pick-up of BESR and release of 8El-IP causes flashing relay EFR to operate at 75 code and to supply this code to section 1T, whereupon it is relayed to the cut section 4T. Signal 8 will, of course, now be at stop;

Looking again at the signal 4 location, since relay 4EI-IP is now up, relay 4EFR will be following 12S code because it will be energized over the 120 code contact of coder GT4- 5 and the front point of contact 40 of relay 4EI-IP. Accordingly, 120 code will be supplied to section 5T so that signal R2 will go to green, signal 4 being at yellow and tion 8T.

When the train fully clears sect-ion 8T and occupies .the adjoining section as shown in the drawings, 75 .code will be .supplied to section 8T because .the flashing relay lliEFR will be energized over the back point of contact v42 of relay IH (whichis .the home relay for signal l!) of the section vnow occupied by the train) and the 75code contact of coder CTE. vOperation of relay SE'IR on 75 code will pick up relays EHR and 8EHP so that signal I8 will go to yellow. 'Ihe pick-up of SEHP will dropout BESR and will change the rate .of .operation of BEFR from l to 12'0 vcode .so that 120 code will now be supplied to sections IT and 4T, causing signal 4 to go .to green. Since the train is now completely out of the single .track stretch, an opposing or Westbound route can be setup by reversing both traic levers I and Il .to their R positions and placing signal lever 9 in its left-hand or Z position.

Since the `operations involved in setting up a westbound route and in the passage of a westbound train over the section areV precisely the same as already described for an eastbound movement except involving the corresponding Westbound relays and signals, these operations will be clear vwithout further description.

summarizing briefly the operations which take place, moving the traic lever at the new exit end of the stretch to the position corresponding to the ,desired traftlc .direction causes code to be applied to the first track circuit at the new exit end, whichcode is relayed progressively over the intervening track circuits .to cause .operation of .the code following track relay at the new entering end of the stretch. If now .both .the .traflic lever and .the signal lever at the entering .end are placed in .the position corresponding to the desired traino direction, the entering signal will clear .to permit entry of the train into the single track stretch. The opposing signals will be held at stop by virtue of the position of ,the tralTic lever at the new exit end, following movements being permitted by means of directional stick relay control which .establishes proper permissive signal indications inthe rear of the train. Once a trainY has entered the single track stretch, the traic direction cannot be reversed by manipulation of the traic levers, until such time as the train has fully cleared the stretch. A back-up move can, however, be permittedby proper movement of the traflic lever at that end of the stretch which serves as the exit for the back-up move. For example, an eastbound train occupying the section 4T may'back up and leave the single track stretch at location D provided that lever l is `iirst moved to the R position which causes code to be applied to section 5T by virtue of the code operation of relay IFR.

It Will be apparent from the foregoing that I have provided a two-direction single track system of the A. P. B. type in which coded polarized current is used for establishing trallic direction in accordance with current polarity and for selecting the signal indications. Operation of a pair of trac levers, one at each end of the single track stretch, and a signal lever at the entering end, clears the signals for a train movement through the stretch and permits following trains to enter but prevents any opposing move or a change inv the established direction until the single stretch is completely vacated. The polarity of adjoining track circuits, though shown alike i-n the drawings, Afor simplicity, may be staggered for the purpose of providing broken-down rail `joint protection. Because of the use of polarity code, opposing signals cannot lbe cleared at the same time through .the medium of stray currents, or otherwise. Moreover, if desired, the system can be controlled automatically from a remote point by a centralized trallic control operator in which case the traino and signal levers would be replaced by appropriate relays having the corresponding contacts and controlled either over a direct wire or over a coded line circuit.

Although I have herein shown and described only one form of 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 yspirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of track over which tralic may move in either direction, said stretch being divided into a plurality of track circuit sections, a rst and a second manually controlled traiiic lever at the rst and the second end respectively of said stretch, said levers having a normal and a reverse position for selectively controlling the polarity of the currentl supplied to said track circuit sections to thereby authorize eastbound and westbound traic movements respectively, an eastbound and a westbound polarized code following track relay for each of said track circuit sections, said eastbound relay responding only to current of one polarity and ,said westbound relay responding only to current of the other polarity in any given track circuit section, an eastbound and a westbound source of current for each of said track circuit sections, said westbound track relays and westbound sources being ineffective under eastbound traic conditions and becoming effective when westbound tranic conditions are established over the stretch, coding means effective when said second traic lever is moved to its normal position for supplying coded current of the proper polarity from the associated eastbound source to I the rails of the last eastbound section to thereby cause code following response of the eastbound track relay Afor that section, means controlled by said last eastbound track relay for supplying coded polarized current to the rails of the adjoining section from the eastbound source associated therewith to thereby operate the eastbound code following track relay for said adjoining section and'in turn to relay the polarized coded current to the rst eastbound section for operating the first eastbound code following track relay, an eastbound headblock signal, a lever for said signal, and rmeans controlled by said signal lever when said first traflic lever is in its normal position and said rst eastbound track relay is following code for clearing said eastbound headblock signal.

2. In combination with a stretch of track over which traic may move in either direction, said stretch being divided into a plurality of track P circuit sections, a rst and a second manually controlled traflic lever at the first and second end respectively of said stretch, said levers having a normal and a reverse position for selectively controlling the polarity of the current supplied to said track circuit sections to thereby authorize eastbound and westbound traic movements respectively, an eastbound polarized coded track circuit for each of said sections including an eastbound polarized code following track relay, a Westbound polarized coded track circuit for each ing said `eastbound track -circuits with polarized coded current progressivelyfrom said second to said iirstend of the stretch, an 'eastbound headblock'signal, a lever for said signal, 'and means controlled by said signal lever and the 'rsteastbound track circuit and eiective when said rst controlled by said last-named eastbound track relay for alternately vdisconnecting the westbound track relay of theadjoining section and supplying an impulse of polarized current to said adjoining section to cause code following operation of the associated eastbound track relay and to'relay polarized coded track circuit current to the rails of the first section to operate the iirsteastbound code following track relay, aneastbound headblock signal, and means effective when said rsteastbound track relay is following code for clearing said eastbound headblock signal.4

leveris 'moved to itsnormal position for clearing said', eastbound headblock signal'. l

3. 'In 4combination with a stretch 'of trackover which traffic Amay move in either direction', said stretch being divided vinto a plurality of track circuit sections, afirst and a se'cond manually controlled traflic lever at the `rstand second end respectively ofsaid stretch, said levers having a normal and a reverse position for selectively controlling'the' polarity of the currentjsupplied to saiditiack circuit sectionsA to thereby `authorize 'coded track circuit current being oppositein` any of said sectionsaccording as `eastbound orwestboundtraine-conditions `are established therethrough, meanseffective when Vsaid second traic lever is moved toits-normal position forV setting said westbound headblock signal at stop and for 'energizing saideastbound track 4circuits progressively from said second to said first. end of the stretchwith polarizedcoded current, means effective when said rst trafiic lever is movedlto its normal position and said eastbound signal lever is operated for clearing said eastbound headblock signal, means effectivewhen said rst trafl fic lever isA moved to its reverse position for setting saidveastbound headblock signal at stop and -for "energizing said westbound track circuits progressively Vfrom 'said rst tol-said second end of the stretch Vwith-polarized coded current, and

means effective when said-second traffic leverV is moved toits reverse position and saidwestbound signal lever isoperated for clearing said west.- bound -headblocksignal. .l A Y. 4. In combinationwith a stretch of track over which traflicmay move in., either directionlsaid stretch beingldivided into a plurality of track circuit sections, an. eastboundl and alwestbound polarizedcode following track relay foreach of said track circuit sections, each `of said relays being normally connected across the-railsof its associated section 4and beingoppositely polarized in any given sectionmeans ,effectivewhen traflic conditions are established in the eastbound direction for alternately disconnecting the westbound track relay associated with the last eastbound section and supplying an impulse of current of the properpolarity to said last section to thereby-cause'code 'following operationV of the eastbound track relay for Vsaidlast section, means o. In combination with a stretch of track over which traic may move'in either direction, said stretchA being dividedl into a plurality of track circuitseetions, an'eastbound and a westbound polarized code following track relay for each of said track circuit sections, each of saidA relays bein'gl normally connected across the rails -of its associated section, the eastbound and westbound rel'ays associated with a given section being op- 'positely' polarized,V manuallyv controllable means hat the eastbound exit end of the stretch for supplying coded 'current of proper polarity t-o the last eastbound track circuit of said' stretch for causing code following operation `of the eastbound vtrack relay associated therewith, means controlled by said last-named track relay for progressively relaying polarized coded current to the remaining sectionsof said stretch to finally cause code following operation of the eastbound track "tem havingopposing headblock signals at the ends thereof, a track circuit junction between said opposing signals, an eastbound and a westbound polarized codeiollowing track relay normally connected across the rails on opposite sides orsaid track circuit junction respectively, means for supplying polarized coded current to the track circuit associated with said eastbound relay to causef-/code following operation thereof, and

means effectivefwhen said eastbound relay Ais following `code"for-*alternately disconnecting said -westbound rela'yfromA the track and substituting a source-of .current therefor to thereby supply polarized coded'current to the rails associated with said westbound relay. Y

i. '7; In atwo-direction single track signaling systern having at least two adjoining track circuits between the 'ends of the single track stretch, an `eastbound and a'westbound polarized code following track relay normally connected across the A"railsl ofsaid two adjoiningv track circuits respectively, means for supplying polarized coded cur- 'rent ,to one-of said track circuits, and means -eiective Whenone` of said relays is following said coded current for alternately disconnecting the other of said relays from the track and substitutingV asource `of current therefor to thereby relay coded 'current into the other of said track cir- ClltSr' 8.1 In atwo-direction single track signaling sysjternhaving atleast two adjoining track circuits between the ends `of the single track stretch, an eastbound and a westbound polarized code following track relay normally connected across the rails of said two adjoining track circuits respectively, means vfor supplying polarized coded current t one of said track circuits, and means effective when one of said relays is following said coded current for alternately disconnecting the other of said relays from the track and connecting a track circuit source of opposite polarity to that which would operate said other relay to thereby relay coded current into the other of said track circuits.

9. In a two-direction single track signaling system having at least two adjoining track circuits between the ends of the single track stretch, an eastbound and a westbound polarized code following track relay normally connected a-cross the rails of said two adjoining track circuits respectively, means for supplying polarized coded current to one of said track circuits to cause said eastbound track relay to follow code, an eastbound home relay which remains energized whenever said eastbound track relay is following code, a coding relay energized over a front contact of said home relay, said coding relay having a back contact included in the track connection of said westbound track relay, and means including a front contact of said coding relay for supplying polarized coded current to the other of said track circuits.

1Q. In a two-direction single track signaling system having at least two adjoining ,track circuits between the ends of the single track stretch, an eastbound andV a westbound polarized code following track relay normally connected across the rails of said two adjoining track circuits respectively, means for supplying polarized coded current to one of said track circuits to cause said eastbound track relay to follow code, an eastbound home relay which remains energized Whenever said eastbound track relay is following code, a coding relay, a first energizing circuit for said coding relay including a front contact of said home relay for causing said coding relay to operate at a iirst code rate, a second energizing circuit for said coding relay including a back contact of said home relay an-d elfective when and only when eastbound traffic conditions have been established over said stretch for causing said coding relay to operate at a second code rate, said coding relay having a back contact included in the track connection of said westbound track relay, and means including a front contact of said coding relay for supplying polarized 'coded current to the other of said track circuits.

1l. In a two-direction single track .signaling system having at least two adjoining track circuits between the ends of the single track stretch, an eastbound and a westbound polarized code following track relay normally connected across the rails of said two adjoining track circuits respectively, means for supplying polarized coded current to one of said track circuits to cause said eastbound track relay to follow code, an eastbound home relay which remains energized whenever said eastbound track relay is following code, a coding relay, a rst energizing circuit for said coding relay includinga front contact of said home relay for causing said coding relay to operate at a iirst code rate, an eastbound directional stick relay, a second energizing .circuit for said' coding relay including a front contact of said directional stick relay and a back contact of said home relay for causing said coding relay to operate at a second code rate, said coding relay having a back contact included in the track con- Vnectionof said Westbound track relay, and means including a front contact of said coding` relay for supplying polarized coded current to the other of said track circuits.

12. In a two-direction single track signaling system having at least two adjoining track circuits between the ends of the single track stretch, an eastbound and a westbound polarized code following track relay normally connected across the rails of said two adjoining track circuits respectively, means for supplying polarized coded current to one of said track circuits to cause said eastbound track relay to follow code, a checking relay which remains energized whenever said eastbound track relay is following code, the energizing circuit for said checking relay including a back contact of said westbound track relay, an eastbound home relay which remains energized whenever said eastbound track relay is following code, the energizing circuit for said home relay including a front contact of said checking relay, a coding relay, an eastbound directional stick relay, a first energizing circuit for said coding relay including a front contact of said home relay for causing said coding relay to operate at a rst code rate, a second energizing circuit for said coding relay including a front contact of said directional stick relay and a back contact of said home relay for causing said coding relay to operate at a second code rate, said coding relay having a back contact included in the track connection of said westbound track relay, and means including a front contact of said coding relay for supplying polarized coded current to the other of said track circuits.

13. In a two-direction single track signaling system having at least two adjoining track circuits between the ends of the single track stretch, an eastbound and a westbound polarized code following track relay normally connected across the rails of said two adjoining track circuits respectively, a coding relay for each of said track circuits, each coding relay having a back contact included in the track connection of its associated track relay, and means effective when either of said track relays is following code for causing operation of its associated coding relay to thereby supply polarized coded current over a front contact thereof to the adjoining track circuit.

14. In a two-direction single track signaling system having at least two adjoining track circuits between the ends of the single track stretch, an eastbound. and a westbound polarized code following track relay normally connected across the railsof said two adjoining track circuits respectively, means for supplying polarized coded current to one of said track circuits to operate the track relay associated therewith, and means effective when said associated track relay is operating for periodically and alternately disconnecting the other track relay from the track and connecting a source of polarized current across the rails of the other of said track circuits.

15. In a two-direction single track signaling system, a track circuit at the entering end of the stretch of single track for a given direction of trafc movement, a polarized code following track relay normally connected across the rails of said track circuit, a headblock signal at said entering end controlled by said track relay, means for supplying polarized coded current to said track circuit to cause operation of said track relay, a trafc lever and a signal lever, a decoding relay having an energizing circuit which includes a front contact of said track relay and a contact of each of said two levers, and means including a front contact of said decoding relay for clearing said headblock signal.

16. In a two-direction single track signaling system, a track circuit at theleaving end of the stretch of single track for a given direction of traflic movement, a polarized code following track relay normally connected across the rails of said track circuit, a leaving signal at said leaving end, a home relay for said signal, a coding relay, a traic lever, means including a front contact oi said home relay and a contact of said traic lever for causing operation of said coding relay at a first rate, means including a back contact of said home relay and said contact of the traic lever for causing operation of said coding relay at a second rate, and means including a contact of said coding relay for supplying polarized coded current to the rails of said track circuit to thereby operate said polarized code following track relay.

JOHN M. PELIKAN.

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