US2344573A - Railway traffic controlling apparatus - Google Patents

Description

J. J. VAN HORN 2,344,573

` RAILWAY TRAFFIC conTRoLLING. APPARATUS Filed sept. '12, 1941 1o sheets-sheet 1 Url MSN. SSN .uw QN ob n @FMAMAM m A n T T N mb w m Nm R mmm A@ A A m f e o mm.. H Sw .ME @mmm n 3f@ AAS; wvw NS@ @www5 n u AAS@ LJ'IPN 52 SS@ NQMM @ASQ NQ SAGE mbk@ @www ARS Nm@ March 21, 1944,

Match 2l, 1944. J. J.- VAN HORN l RAILWAY TRAFFIC CONTROLLING APPARATUS .AQ @SAN E SQ March 21, 1944. J. J. VAN HORN RAILWAYy TRAFFIC CONTROLLING APPARATUS Filed Sept. 12, 1941 10 SheeS-SheetI 3 H Fl l @IJHN .WSDNM W m F m m m@ m0 J mV r 4 m v m 0.@ FL r .m l www o o@ o n 1 LL rr| ya n w Y m rb vBY March 2 1, 1944. J. J. VAN HORN RILWAY TRAFFIC CONTROLLING APPARATUS J. J. VAN HORN i RAILWAY TRAFFIC CONTROLLING APPARATUS Marh 21, 1944.

10 Sheets-Sheet 5 Filed Sept. 12, 1941 @N SI s FUJI@ GMNMA LL? mw mlww 1mm.: m

b @SSN NWN March 2l, 1944. J. J. yVAN HORN RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 12, 1941 l0 Sheets-Sheet 6 March 21, 1944. J. J. VAN HORN RAILWAYTRAFIC CONTROLLING APPARATUS Filed Sept. 12, 1941 l0 She'ets-She'et 7 www? MEQ@ QN o mmww Sm uw E@ S NSNNM,

INVENT'oi- TmHopn HIS A'rnToRNEY James u Y L M TN M' Y March 21, 1944 J. J. VAN HORN RAILWAY TRAFFIC CONTROLLING APPARTUS- 1o sheets-sheet 8* Filed Sept. 12, 1941 INVENTOR J Vnbm 5G H r QLJ! Q @VS J@ Marchj 2 l 1944.

J. J. VAN HQRN RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 12, 1941 Signa] SZ HIS ATTORNEY 10 Sheets-Sheet 9 March 2l, 1944. 1. J. VAN HORN RAILWAY TRAFFIC GONTROLLING APPARATUS Filed Sept. 12, 1941 10 Sheets-Sheet 10 uw .Sk

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INVENTOR ENQ@ tbm@

BY l

. lnbln HIS ATTORNEY control or other suitable manual control is used Patented Mar. `21, 1944 RAILWAY TRAFFIC CON TROLLIN G APPARATUS James J. Van Horn, Pittsburgh, `Pa., assignor to The Union' Switch Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application September 12, 1941, Serial No. 410,504

31 Claims.

I My invention relates to railway traic controlling apparatus and is directed in ore particularly to the control of trafiic in a single track two-direction system wherein centralized trailc for establishing the traiilc direction. A distinguishing feature of my system is that it employs normally deenergized track circuits and dispenses with all control line wires except the coded C. T. C. line circuit, if C. T. C. control is used.

One object of my invention is to provide a normally deenergized track circuit system of signaling for traiiic moving in either direction on a single track, without employing the usual control line wires. Another object-of my invention is to establish the desired traiiic direction merely by moving a trailic lever at the control oilice, the checking and safety features of the system being brought into play automatically as a result of such movement. A further object of 20 my invention is to provide certain inter-controls on the C. T. C. machine, if used, to prevent interference with the established trailic direction when the entrance signal is at proceed or the section is occupied by a train. A stil1 further ob- 'ject of my invention is toI provide for the proper control of highway crossing signals and electric switch locks in a, normally deenergized. non-linewire system of the character herein disclosed. An additional object of my invention is to' use but one set of code responsive apparatus for controlling both signals at intermediate locations. A further object of my invention is to provide a block indication for certain track circuits by pclarizing the code effective therein. Other objects, 35

purposes, and characteristic features of my invention will be apparent from the description which follows. s

I accomplish the foregoing objects by: applying a rail current code at the new exit end of the 40 stretch and cascading this code progressively over the track circuit sections to the new entrance end to thereby check unoccupancy of the stretch and obtain proper restrictive indications of the opposing signals as well as permissive indications 5 of the signals 'for the new direction; using properly controlled stick repeater relays of the trame lever to prevent interference with the established trailic. direction and to permit following moves;

using "meende checking relay (FSA) :or direc- 50 tional control when the stretch is unoccupied and using the eastbound stick relay (ES) and the westbound stick relay (WS) for this directional control when the stretch is occupied; using the approach lighting relay (AR) forl the control of u ploying an additional rail current of a slow code for highway crossing control purposes -in conjunction with the normally deenergized track 5 circuits of my invention; and employing polarized coded track circuits for switch lock control without line wires, and feeding coded energy from both ends of the section toward the electric switch lock to indicate that the track sections on each side of the lock are unoccupied and that, if occupied, the train is moving away from the lock.

The present invention is an improvement on the invention disclosed in the United States patent application Serial No. 403,502, filed on July 22, 194i, by Ralph R. Kemmerer, for Railway traffic controlling apparatus.

I shall describe several forms oi apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In theaccompanying drawings, Figs. lato le taken together, with Fig. la at the left, are a dia- Y grammatic view showing one embodiment of my I invention as applied to a stretch of single track railway extending between the passing sidingsat the two ends of the stretch. Figs. Za'and 2b taken together, with Fig. 2a at the left, are a diagrammatic view showing my invention applied to a highway crossing location within a stretch of sin gie track such as shown in Fig. l. Figs. 3a, 3b, and 3c taken together, with Fig. 3a at the left, are a diagrammaticview showing my invention applied to the control of electric switch locks associated with the single track stretch. Fig. 4 shows a modified form of a portion of the ap- Figs. 5a and 5b are modified forms of certain portions of the apparatus shown in Figs. 1a and le, respectively, and also embodying my invention.

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

Referring rst to Figs. la to le, lnclusive,the stretch of track between the passing sidings PSi and PS2 is divided by the usual insulated rail joints at locations E, F, G, H, I, J, and K, to form a number of track circuit sections. Each of these paratus of Fig. 3, also embodying my invention. Fig. 4a. is an explanatory track diagram lfor Fig. 4.

provided with signals, if desired, by adding similar apparatus to that shown at the'intermediate signal locations. Y

Each section of the single track stretch is, in reality, provided with two track circuits, one eastbound and one westbound, each of which includes a 'code following track relay TR at one end and a source of direct current track circuit energy, conveniently shown as a battery, at the other end. This current is properlycoded under the iniluence of traffic conditions, orv as initiated by the operator at the central control location shown diagrammatically as the control voiice in Fig. la. Depending upon the direction of tramo movement, only one or the other track circuit is effective at any one time as will become clear hereinafter. The control relays involved in an eastbound move generally carry the prefix E or R (for right-hand) and those which control westbound moves include the prex W or L (for lefthand) in order to make the disclosure more readily understandable. l

For simplicity, I make use of but two codes, these comprising direct current periodically interrupted at the rate of 75 times per minute for approach" and 180 times per minute for clear signal indications. The coding is accomplished by means of suitable code transmitters CT and IBUCT which are-:well known. It is understood that for cab signaling purposes, alternating current coded over the contacts of these code transmitters could be superimposed on` the direct current track circuits but I have not shown this added complication since it does not involve my invention. Certain of the track circuits are polarized and employ polarized track relays as a means for providing an indication by means of a block light on the track model as to the location of atrain within the single track stretch. This feature will be described more fully hereinafter. A,Di-l

rectional stick relays are used for permitting following moves to be made without any further action being required on the part of the operator.

The relays SLFSR (Fig. 1a) and BRFSR (Fig. 1e) adjacent the twoends of the stretch are manually controlled trailc direction selecting relays which govern the direction of traiivic movepair of line wires to the desired control location or eld station. The detailsof suclra communication system do not enter actively into the present invention and it is deemed suicient for an understanding of the present invention to point out that the trafc direction from right to left or westbound is established by moving the lever 8 in the control olce (Fig. 1a) to the left-hand or;

L position so as to energize the trairic relay BLFSR at the iield station at the left-hand end ofthe stretch (location E), and that the traic direction from left to right or eastbound is established by moving the lever 8 to the right-hand or R posiportion of my system corresponds with that used' in this patent. In order further to simplify the disclosure, I have used the same reference numbers as in the Lewis patent to designate corresponding terminals or wires of the eld station code units at the two ends of the stretch, these wiresvserving' to transmit analogous control or' indication functions.

I shall now describe the operation of the apparatus of my invention in detail, rst assuming that all of the track apparatus (except the code transmitters) is deenergized, and that the operator moves the traic lever 8 to its left-hand or L position, thereby energizing the trailic'relay LFSR. The movement of lever 8 causes a control code to be transmitted from the control ofce, over the C. T. C. line, to the eld station at location E, thus causing relay SLFSR to become energized. This relay sets up the trailic direction from right to left, or westbound. 4The energization of relay SLFSR completes a circuit which energizes the code repeating relay BRTCTM on' code to thereby transmit a corresponding code to the track section BRT. If-the home relay 6LAI-l1iI for signal SLA' is deenergized, so that back contact 23 is closed, as shown, 75 code will be transmitted to condition signal 1L at location G to display an approach indication. If, however, signal BLA'is at approach or clear, then relay BLAHR will be energized so that 180 code will be supplied over contact 23, now closed in its up position. As shown, signal GLA is at stop so that the coding circuit for relay RTCTM may be traced from the code transmitter wire 15B which is one terminal of the '75 code source, back contact 23 of relay BLAHR., front contacts 24, 25,

and 26 of relays STR, ERKM, and 8LFSR (nowA up), back contacts 21 and 23 of relays BRSR and BRFR, and the winding of relay SRTCTM, to the other terminal C of the source. Contact 24 of relay STR checks that an eastbound move has not been started past signal 6R, and contact 25 of relay ERKM checks that the opposing signals A(iRA and BRC are at stop. Since relays SLAHR and GRKM are well known, the specific control circuits for these relays are not shown in detail, it being suilicient to associate these relays with 'their respective signals. Back contacts 21 and 28 of relays SRSR and BRFR, respectively, check that trafc has not been established for an eastbound move, as will be apparent hereinafter. Accordingly, with the apparatus in the condition illustrated, code is being supplied to the section BRT from the track battery TB over the front point of coding contact 29 of relay SRTCTM.

The '75 code is received at location F by the westbound code following track relay GRWTR, over the back point of contact 39 of the eastbound track relay SRETR, and is relayed into the cut section BART over thecoding contact 3| of relay GRWTR. This contact supplies a current impulse from the track battery TB over an obvious circuit each time that its front point closes. The '75 code is received by relay 'IWTR at location G, over the back Vpoint of contact 32 of relay 'IWCTM which results in the energization of relay TWTFSA which is Vslow acting by Virtue of i the resistor snub 33 and therefore retains its picked up position while relay 'IWTR is coding. The energization oi relay 'IWTFSA closes an obvious circuit over its front contact 35 and front contact 34 of relay 'IWTR for the code repeater relay TM which follows the co'de and controls one set of decoding apparatus common to both sections BART and IIRT. Relay TM itself is also IWTR relay (which in this case is 75 code) and in so' doing will energize the slow pick-up, slow `release relay 'IHR from the decoding transformer 'IDT over the rectifying contact 35 of relay TM in the usual and well-known manner. The

transformer 'IDT is energized over the coding contact 31 of relay TM and this circuit also inare both energized, a 180 code circuit is completed for the code following relay IRECTM over the coding contact 40 of code transmitter I80CT and front points of contacts 4 I and 42 of relays IWTFSA and THR, respectively, whereupon relay IRECTM will supply 180 code from battery TB over the front point of its coding contact 43 to the section IRT. The operation of the westbound approach relay 'IWAR will be explained hereinafter.

At the cut section location H, the 180 code will be received by relay 'IRWTR and re-transmitted or cascaded into section IART over the front point of coding contact 44 of this relay. This code will be received at signal location I inV the same manner as described for the signal location G so that this description need not be repeated. With relays SWTFSA and SHR both energized, relay SECTM will be energized on 180 code over the front points of contacts 45, 46, and 4l, as at location G, and will repeat this code into section BRT. From this section, the code will be repeated into section IDLT by polar relay BRWTR (which is connected in parallel with the polarized track relay 8RWTRA), as previously explained. Relays IULTRA and IDLTR at location K will receive the 180 code and will make it possible .for the operator to clear the headblock signal IBL so as to permit a westbound train to enter the single track stretch.

i Referring again to location I, it will be noted that the code supplied to section BRT is polarized and is of one polarity when the 180 code decoding relay 8DR is energized so that the front point of contact 48 is closed,vbut is of the other polarity when relay 8DR is deenergized and the back point of contact 48 is closed. Contact 48 selects either battery TBI or 'I'B2 as the supply battery for the track code and since these batteries areoppositely poled, polarized track circuit operation is obtained. The reason for polarizing the block I-K is to provide a proper block indication on the track model, which feature will be described more fully hereinafter. For the present, it will be sufficient to state that the code following biased polar track relay IULTR at location K isv energized in parallel with the non-biased polarized code following relay IULTRA andis checked over the polar contacts 49 and 50 of the latter relay to insure .that the latter has responded properly to the polarized track circuit code. 'I'he track relays of my system such as SRW'I'R, 1WTR, 'IRWTR, etc., are preferably of the biased 1 polar type which means that these relays will respond only to current of the proper polarity. Current of the other polarity will merely hold these relays more strongly in their released position. The non-biased polarized track relays such as SRWTRA and IIJLTRA respond selectively to current of either polarity and remain in the position to which they were last operated.

`\.Returning again to location K, the coding action of relay IOL'I'R will energize the decoding transformer-DT at 1 80 code over the coding contact 5| so that both relays IULDR and 8LFR will become energized. Relay BLFR is the usual code detecting relay which remains energized on impulses of either 75 or 180 code.

With relay SLFR energized and polarized relay IULTRA occupying ysive sections) with code.

its normal position as shown, a circuit will be completed to terminal SIA of the field station unit over front contact 52 of relay sLFR, wire 53,l and the normal polar contact 54 of relay I0 L'IRA, so as to provide the operator with an unoccupied Westbound block indication on the track model. The energization of relay BLFR also closes a circuit to terminal 89 of the field station unit over the front 56 and wires 51 and 58 to provide an indication at the control oilce that traic is established for a westbound move. Signal IULA or IIJLC may now be cleared by the operator in the usual and well-known manner through the code equipment, to permit a train to enter the single-track stretch and proceed toward the signal 6L at the other end. If cab signaling is used, then after the train passes signal IOLA or IULC, a code applying relay would be energized in the usual manner to provide the track section 9T (and other succes- This code supply circuit is of conventional form and so has not been illustrated.

If the single track stretch should include but one intermediate signal location (G) then the westbound block indication can be provided, as shown in Fig. 5b (Sh.5), over a. front contact of relay 8LFR and a front contact of the 180 code detecting relay IOLDR. The eastbound block indication under this condition will similarly be provided, as showny in 5a (Sh. l), over a front contact of relay BRFR and the code detecting relay GRDR. In this arrangement, it is unnecessary to polarize the code in order to obtain a. continuous block indication.

Having described the manner in which the apparatus is conditioned for a traflic movement in the westbound direction over the stretch, li shall next trace the progress of a westbound train as it moves over the various sections.

As the train enters section 9T, relay STR will release and a circuit will .be completed for the directional stick relay QISR over the back contact 60 of relay STR and the front point of contact 6l of relay IDLAHR which is the home relay for signal IOLA.- If the train enters from the siding PS2, then the circuit for relay 8LSR will include the back point of contact 6| and the front point of contact 62 of the corresponding home relay IDLCHRfor signal IULC. -Once relay BLSR picks up, it closes a stick circuit for itself over .back contact 60 of relay STR and its own point of its contactA front contact 63. When the train enters sec- 'tion' I ULT, the code detecting relay BIER will release, closing an auxiliary stick circuit for relay 8LSR over back contact 64 of relay BLFR, back points of contacts 62 and 6| of relays IULCHR and IULAHR, and front contact 63 of relay ELSR. This stick circuit does not include the back con- 'tact' 60 of relay STR so that when the train fully clears section 9T and relay STR picks; up, the directional stick feature provided by relay 8LSR will continue to be maintained. Furthermore, when the train fully clears sections lilLT and SRT so that relay SLFR picks up on 75 code. an additional stick circuit for relay BLSR will become eiiective in order that this relay may remain energized during the whole time that the stretch is occupied. Consequently, the westbound tramo directional arrow on the track model will remain lighted. This additional stick circuit for relay BLSR includes the front point of contact Y 64 of relay tLFR, reverse polar contact 65 of relay IDLTRA, and front contact 63 of relay SLSR. Reverse polar contact -65 will close before relay BLFR picks up and will remain closed thereafter until the stretch is cleared, whereupon relay BDR at location I will become energized and will restorenormal polarity code to block I-K Relay lLTRA will then again become energized in the normal direction.

Referring for the moment to the eld station unit at location K, it will be seen that the control circuit to terminal 89 for the Westbound traic direction indication can also be established over the back point of contact 56 of relay BLFR and the front point of contact 66 of relay 8LSR, The traiiic direction'indication is accordingly maintained to provide the operator with this informationV during the Whole time that the stretch .is' occupied. Moreover, this indication will persist `even after the stretch becomes unoccupied, until such time as the operator places lever 8 in the normal or N position and sends out a code to release relay LFSR and so to deenergize` the track circuits.

If approach lighted signals are used, the westbound stick relay 8WS at location I may be picked up over front contact |62 of the approach relay SWAR and front contacts 6l and 68 of relays BWTFSA and SHR, respectively, when the train approaches the signal, 8L. If. normally lighted signals are used, then the stick relay 'SWS will be picked up over the front contacts 61 and E8 of relays BWTFSA and SHR only, as soon as code is supplied to section 'IART prior to occu'- pancy of the single track stretch. When once picked up, relay SWS is retained energized during occupancy, over-a' stick circuit which includes its own front contact 69 and the back point 'of contact 68 of relay HR. This stick circuit does not become operative, however, until the train passes signal 8L and shunts the track section I ART so as to release relay BER. With relay be fed to section 'IRT in the same manner as` just describediorlocation I. whereupon relay EHR at location I will pick up and in so doing will open the stick circuit of relay 8WS at-the back point of contact 68 of relay 8HR. If the BWAR contact is used in the pick-up circuit of relay 8WS, the latter relay will nowbe deenergized. If relay 8WAR is not used, relay SWS will remain energized as its pick-up circuit remains eiective over iront contacts 61 and 68 of relays BWFSA and 8HR, respectively. Ihe energization of relay BHR will cause 180 code'to be supplied to section IK, as previously described. Relay BWS must be suiciently slow in releasing to bridge the release period of relay 8HR for a high speed, light weight engine movement past signa1 8L and possible differences in the release periods of relays SWTFSA and SHR.

It will be noted that relay BWTFSA provides lthe directional control when 4,the track section ahead of signal 8L is unoccupied, and that relay WS retains the directional control when this section is occupied. With this arrangement, one TM relay, one decoding transformer DT, one DR relay (BDR), and one HR relay (SHR) are sufficient for the control of the tWo signals 8L and SR. If the stretch contains but one set of intermediate signals between the two passing sidings, then it becomes unnecessary to polarize the track circuit code for proper block indication because Athe 180 code decoding relay lllLDR will then indicate the unoccupied condition of the block when the track circuits are energized and trafiic is established for the westward direction.

I shall now explain how traic is set up .for a move in the eastbound direction. Since relay Y IULTC'IM at location K is controlled over the "back contacts l2 and 13 of relays 8LFR and BLSB., respectively, it is not possible to energize this relay whilel traiiic is established for a westbound move because one or the other of these relays will be energized, depending upon whether the stretch is unoccupied or occupied. Consequently, if the operator desires to reverse the trailic direction to eastbound, the section must be unoccupied, and he may irst send out a code (with lever 8 vin the N position) to deenergize relay BLFSR at the eld station location E. When the clear block indication light on the track model disappears, as it will when relay SLFR is deenergized due to the removal of track circuit energy from the stretch, relay BRFSR at the zation of relay BRFSR enables an eastbound move to be established in a similar manner to vment of the block light before moving the lever i' to the R position.. The traiiic change may be effected at any time by moving lever 8 from the L to the R position provided that the stretch is unoccupied at such time. Extinguishment of the block light may occur during this process and not necessarily prior to the lever reversal.

Referring for the moment to the code'starting relays 235ST and 231ST (shown in Fig. 1b) which control the transmission of code for energizing the westbound and eastbound traiilc direction control relays 8LFSR and 8RFSR at fleld stations 235 and 231,` respectively, it will be noted that energization of terminal |85 which is essential for code transmission, as will be apparent from the Lewis patent referred to hereinbefore, will not` occur unless the lever 8 occupies the corresponding position andthe corresponding lever repeater relay 8LP or 8RP is energized. The pick-up circuit for each lever repeater relay is checked over a back' contact of the other lever repeater relay. Movement of lever 8 to the L position will pick up relay 8LP over the back contact |51 of lever repeater relay 8RP. vOnce relay 8LP picks up, a stick circuit will be completed therefor over its front'contact |58. This stick circuit can be maintained either over the L contact of the lever, or over an auxiliary circuit which includes the back contact |59 of the block (unoccupied or occupied) indicator relay SLBK and the front contact` |68 of the traiiic direction indicator relay SLFK. A still further stick circuit for relay 8LP will be closed over the front contact |6| of the signal indication relay .lllLHKwhlch indicates that signal IOL displays a proceed aspect. Accordingly, no reversal of the traillc direction can take place while the stretch` is occupied or While the entrance signal is cleared. 'I'he indication circuits controlled by relays 8LFK (terminal 89) and SLBK (terminal 9IA) are well known and will be obvious from the Lewis patent in `which the corresponding terminals are num bered 89 and 9|.

The form of traiiic lever 8 which I prefer to use is one which has associated therewith a starting key SK which is closed during the preliminary motion of the lever, thus vapplying energy more quickly to the starting 'relay to avoid certain operating difficulties. Use of 'this type of lever makes it more easy to deenergize the signals by moving the lever to its N position, since the preliminary movement of the lever (before contact L or contact R opens) makes it possible to transmit the deenergizing code to the respective signal. However, this type of lever is not essential in the operation of 'my system, and an ordinary trailic lever may be used.

Referring next to Figs'. 2a and 2b which show a highway crossing application of the apparatus embodying my| invention, it will be seen that the single track stretch |-3 is intersected by a high- -way at location 2. It will .be understood that this highway crossing stretch. is located at some point in the single track between the passing sidings PSI and PS2 of Fig. l but has beengshown as a separate portion of the complete system to sim-A plify the disclosure. v

Since the track circuits are normally deenergized, it becomes necessary to employ a differentV Vform of energy for clearing out the highway crossing control apparatus. than the energy which is normally used for track circuit operation. Accordingly, I make use cf current impulses of a code` substantially slower than the signaling code,

such for example asa code in which the current is interrupted at the rate of times per minute.

Assuming now that ihctralilc lever 8 of Fig. 1 is in its neutral or N position so that neither traffic direction is. estabished, the code transmitter NCT 'at locatifn 3 which supplies the 20 code lil.)

back point of contact 18 of relay 3ETR, wire 19,

front point of contact 80 of coder 20CT, wire 8|, battery TB, and wires 82 and 83, to the lower rail. This code will be received at location 2 and will operate the code following relay 2ETR over a circuit which can be readily traced and which includes the back point of contact |84 of relay 2WCDR. Operation of relay 2ETR causes pickup of the ETFSA (eastbound front contact slow acting repeater) relay followed by pick-up of the ETBSA (eastbound back contact slow acting repeater) relay after front contact |85 of relay ETFSA closes; 'I'hese repeater relays bridge the operation of relay ZETR'on 20 code and the closure .,of front contact |85 of relay ETBSA thus provides a check that relay 2ETR is following code and completes the energizing circuit for relay ET'M.

At location i 20 code is similarly applied to the track circuit iET--ZWT so that relay ZWTR follows 20 code and causes relays WTFSA, WTBSA, and W'I'M to become energized in the same manner as just described. With relays WTM and ETM both energized, the highway crossing control relay XR, will be energized over the front contacts |06 and |88 of these relays So that the highway crossing slgnalswill remain inactive.

It should be pointed out that since relays ETFSA and ETBSA are suillciently slow acting to remain picked up on 20 code, they will also remain picked up on '15 and 180 code. However, the ECDR and WCDR relays are so designed as to pick up and to remain picked up on` '75 and 180 code, but to release on 20 code.

Assuming next that trafllc is .established for a westbound move, coded energy of either 75 or 180 code will be applied to relay IWTR (depending on traic conditions in advance) which will cause energization of relay IWCDR from the decoding transformer iDT in well-known manner by virtue of the operation of the coding contact |89 and rectifying contact |90 of relay IWTR. Energization of relay IWCDR opens the circuit for coder ZDCT at back contact ISI, thusA removing 20 code from the track circuit |ET-2WT which controls the crossing.

Code operation of relay IWTR at 75' or 180 code causes this. code to -be repeated over front contact |92 into the track circuit IET-ZWT so as to cause operation of the code following relay ZWTR at the crossing at 75 or 180 code instead of 20 code. Relay 2WCDR will now become energized .and will close'a circuit for operating the coding relay CTM which relays the code from section |-2 into section 2 3. The circuit for operating relay CTM includes front contact |93 of relay 2WTR, wire |94, front point ofcontact |95 of relay 2WCDR, wire |96, back point of contact |91 of relay2ECDR, and wires |98 and |99, to relay CTM. The code feed circuit for section 2-3 includes the front point of contact |84 of relay 2WCDR and the coding contact |08 of relay-CTM.

it is obvious that instead of using relay CTM, the code could be repeated over a contact of the track relay itself. However, it is advantageous from the standpoint. of sensitivity 'to employ as few contact-s on th track relay as possible. Therefore, I prefer to use the .CI'M repeater. Moreover, one CTM relay suffices for repeating the code in either direction, as will be -obvious from the symmetrical arrangement of theapparatus at location 2. It will be noted that coded track circuit energy of 75 or 180 code Ymay .be

applied'to the location 2 end o f section 2-3 at manner previously described.

the same time that coded track circuit energy ofA 20 code is applied to the location 3 end of the section. Thev energization of relay 2WCDR will open the control circuit of relay ZETR, thus deenergizing this relay. Relays ETFSA and ETBSA will, however, retain their front contacts closed (due to their slow release characteristic) to bridge the open period of 20 code. During the rst open period of 20 code in section 2 3, the 75 or 180 code will operate relays WTR and SWCDR at location 3. 'Ihe pick-up of relay SWCDR opens the circuit for coder 20CT at its back contact 16, thus removing 20 code from section 23.l The circuit for relay SWTR will remain eiective over the back pointof contact 80 of coder 20CTsince this coder is so designed as to close this contact, when deenergized.

The energization of relay 2WCDR at the crossing causes the release of relays ZETR, EIT-SA and EIBSA also at the crossing, but since relay SWCDR is now energized, relay ETM is continassauts It will be apparent that the highway crossing apparatus which I have provided is such that it wili'operate properly to provide -protection ued energized by the circuit over front contact 10| of relay 3WCDR so that the highway crossing signals remain inoperative. 'I'he receipt of 75 or 180 code by relay ZWTR at the crossing will continue to maintain relays WTFSA and WTBSA energized (these were previously energized on code) so thatrelay WTM will also remain enere gized.

When a westbound train enters the section from the right and passes location 3, relay 3WTR will release because of the train shunt, followed by the release of relays 3WCDR. an'd ETM, in turn. The opening of front contact |08 of relay ETM deenergizes relay XR. which thereby released due to the occupancy by the train of track section |-2 which results inthe shunting.

of relay ZWTR. 'I'he energization of relay WSR will close a path around f ront contact |06 of preparea pick-up circuit for relay XR which will be effective as soon as the train vacates section 2-3 .and front contact |08 of relay ETM closes. The pick-up of relay XR will cause the Ahighway crossing signals to cease operating, in

the usual manner.

-During the time that section I2 is occupied, even though section 2-3 has been vacated, relay 2WCDR will remain deenergized so that track circuit energy of 75 or 180 code cannot be supplied to section 2 3. However. energy of 20 code will be applied to section 2-0, as previously described, whereby relays 2EI'R, ETFSA, EI'BSA, and finally ETM will be energized, thus cutting out the operation of the highway `crossing signals through pick-up of relay XR, as indicated above. 1 l

When the westbound train vacates section |-2' and passes beyond the next signal of the single track stretch, 75 code will be fed to the track circuitfin the rear of the signal and by a cascadingaction, this 75 code will be repeated into all of the track circuit sectionsbetween that signal and the' next signal in the rear thereof.

The presence of 75 code in section 2-3 will remove the supply of 20 code to this Section in the Vrelay WTM at its front co'ntact |07 so as to even though it should prove impossible to set up the traillc direction by means ci' the 75 or 180 track circuit code and a train enters the block under train order authority. The presence of 20 code for highway crossing control under this condition makes it possible to provide proper and safe voperation notwithstandingY unforseen failure of the ordinary track circuit code or its associated apparatus.

Referring next to Figs. 3a, 3b, and 3c, these taken together in that order show a single track stretch similar to that shown in Figs. laf-1e, but

having two intermediate sidings or turnouts TI and T2 at locations F and H, respectively. 'Ihe systemshown in these gures makes application of the apparatus embodying my invention to the control of electric switch locks which are associated with the track switches for these turnouts.

In order to permit a train to leave a siding at an electrically locked switch, for example, the siding T2 at location H when the stretch is unoccupied, traflic would have to be established in one direction or the other by a movement of lever 0 as described in connectionV with Figures la-le. I shall assume that traffic is established in the westbound direction, as described in detail in connection with Fig. 1. The operation of traic lever 8 to the L position as described in detail in connection with the apparatus of Fig. 1 results in the energization oi" relay BLESR which applies coded energy to the track circuit GRT in the rear of signal BL. Since the switch lock control relay 1RWSR at location D is deenergized at this time, the polarity of this code is positive so as to operate the polarized relay SRTWTRA at the cut section location E to its normal position in which the polar contacts |09 and ||0 are closed to the left. This causes the biased polar relay SRTWTR to pick up. The code received by relay BRTWTR will be repeated by relay BRTWTM (which itself ls a repeater of relay SRTWTR) over a circuit which includes the front p oint of contact i of relay SRTWTM, polar contact H2 of relay GRTWTRA closed to the left, and front contact H3 'of relay lOTWM, into the section 1T. 'Ihis circuit is the same as previously described (for Fig. l) in connection with cut sections involving polarized TRA relays for the control of the block indication except for the addition of the contact.

of the OTWM relay. This relay repeats the deenergized position oi' the electric switch -lock 1W, the unoccupied condition of the short lreleasing track section, 'IOT (by means of the front contact ||I of relay OTR), the contact oi? the usual time element release TER, and the back contact ||5 of The application of code of positive polarity to the section 1T will be detected at signal location' G by relays IWVI'RA and BW'I'R, in the manner previously described, and this code will be decoded in the usual manner to energize relay SWHR alone, if signal GL is at stop code to the rear) or to energize both relays BWI-IR and IWDR if signal 6L indicates approach or clear code to the rear of the signal). The energization of relay SWHR will cause 180 code to be supplied to relay BECTM at location H over a circuit which includes the 180 code terminal |00B, front point of contact H6 of relay 8WHR. front contact II'I of relay BO'I'WM, and back contacts and H9 of relays SEHR and BES, to relay BECTM. The operation of relay iSECTM on 180 code will repeat this code into section 8T and point of contact closed) the code fed to the track circuit |0LT will be of positive polarity so as to close the normal or left-hand contacts |2| and |22 of relay IOLTRA. thereby providing the proper block indication on the track model. When relay |0LTRA is energized on this code, relay BLFR of Fig. le will be energized and will transmit an indication to illuminate the trallic direction arrow on the track model for a westbound move. A clear block indication will also be established on the track model because of the normal polarity energization of relay IBLTRAJ The operator may now postion lever 'I at the control office to theleft-hand or L position and send out a code to energize terminal 82 of the eld station unit so as to energize relay TLWSR at location K which will be picked up over the front contact |23 of relay BLFR. Ifv a Vwestbound train is in the section, relay BLSR will be energized so that relay ILWSR could be picked up over front contact I 24 of that relay. After pick-up, relay 'ILWSR closes a stick circuit from terminal 03 of the fleld station unit over its own front contact |25. The

energization of relay 'ILWSR picks up relay B11-SR over front contact |26 to thereby retain control o! the traffic direction indication at the control oidee.A

After the code has been sent to the end of the single track stretch to energize relay lLWSR at location K, the operator may instruct the trainman to operate the knife switch 8K8 associated with the electric switch lock 1W at location H for the purpose of completing a circuit for relay 8S. This relay will pick up and thereby open its back contact |21 which is included in the circuit for relay 8OTWM, thus deenergizing this. relay and thereby opening front contact I in the cir- 'cuit of relay SEC'IM. The release of relay BECTM will cut Yoil' the code from section 6T and also from `section |0LT, upto signal IDR.

.` The resulting deenergization of code detecting relay SLFR will complete the circuit for relay IULTCTM at its back contact |28l so that, With relay 'ILWSR at location K energized, code of` negative polarity will be applied to the track at location K, over the front point of contact |29 of. relay.`lLWSR and the front point of contact |30 of relay VIDLTC'I'M. This code will be either 'or 180 depending upon the position'of signal |0R (position of contact 81 of relay IORAHR).

The negative lpolarity code will be detected at signal BR, location I, and will cause relay SETRA to close its polar contacts in the reverse or righthand position, whereby relay 'IRWR will become energized over contact |3| in its right-hand position. Relay IRWR will now close its front contact |32 and in so doing will cause negative polarity code to be applied to the track section 8T.

This code will be detected by relay 8ETRA at location H.

The negative polarity code received by relay SETR at location I will be decoded in the same manner as described for the other intermediate 4signal location. Also, the control of the code supply into the adjoining track. circuit 8T by the operation of relay SWCTM will be clear from the previous description presented in connection with the apparatus of Fig.v 1.

With relay SETRA energized on code of negative polarity, relay BETRA will also be energized to its reverse position so that its normal polar contact |33 will be open. Accordingly, the eastbound directional stick relay BES will then be de energized. This arrangement prevents improper operation of the stick relays such as might otherf wise cause a locked-up condition in which both relays 'WS and ES at adjoining locations would be picked up when a train enters the main track at an electric switch lock. This condition might result from the fact that coded energy is applied to both ends of the section at the same time so that no particular direction of traiiic is then established. It is to prevent the possibilityof such a locked-up condition that I employ code of .reverse polarity suppliedto the track circuit at one end of the section when an electric switch lock is involved.l

The negative polarity codereceived by relay SETR will be decoded in the usualv manner to energize relay 8EHR which causes nergization of relay WEHSM. Closing of the front contact -|34 of relay WEHSM completes a circuit over front contact |35 of relay 8S to illuminate the indication lamp LW at the electric switchlock at location H. When this indication is received,

the trainman will .restore the knife switch SKS to its normal or closed position so as to complete a circuit for energizing the switch lock 1W. This c`rcuit may be traced from theknife switch 8KS, Wire |36, front contacts |31 and |38 of relays WEHSM and 8S, respectively, and wire |39; to the switch lock 1W. Relay WEHSM becomes energized when either of the relays ilWSY or 8WHR is energized at the same time that either relay SEHR or BES is energized, as will be obvious from the drawings.

When the switch is unlocked the switch may be reversed and the train may enter the main track and proceed westward toward signal 6L. If

relay BW'I'RA at location G receives coded energy Vof normal polarity, the following stick relay BWS may be energized over a circuit which "includes the front points of contacts |40, |4|, and |42 of relays 8S,'8OTR, and 8WHR. Relay 8WS will rema'n energized Aupon the occupancy of track Y circuit T,over a circuit which includes its own front contact |43, the back point of contact |4| of relay 8OTR,.now released, and the front point of Contact |42 of relay 8WHR. When relay 8WHR releases following the movement of the train out of track circuit 80T intosection 1T,

the back point of contact |42 of relay 8WHR.

will be substituted for the back point of contact Y According1y,'relay 8S will remain energized until the switch is opened and relay BWTR is shunted so as to deenerglze relays 8WHR, and WEHSM.

If, for some reason, coded energy cannot be received over the track circuits 'IT and 8T to the termned time following the operation of the time release, in the well-known manner.

Should a westbound train wish to enter the turnout T2, it would not be possible for relays BETRA and SETR to receive coded energy if any portion of the train remained lon the track circuit 8T of the main track. It is therefore necessary to make use of the short releasing'track circuit 801 immediately ahead of the switch so that when this track circuit is occupied, the switch lock may be energized directly over the circuit which includes the closed knife switch SKS, and the back contact |41 of relay BOTR.

From the foregoing description, it will'be seen that coded energy is fed `:from each end of the single track stretch toward the electric switch lock location and whenthis energy is detected at the switch lock, this indicates that the single track stretch is unoccupied or that, if occupied, the train is moving away from the switch lock location toward one or the other end of the section and has cleared the adjacent intermediate signal.

The control of the electric switch lock at the the oliice should be so selected that the control code for these relays is transmitted to the entrance end of the Iblock only, for if codes were sent to both ends of the stretch, the relay at the entrance end of the block would be the only one to pick up because it is only at that end of the block that the code detecting relay (SLFR Aor SRFR.) would then be energized. In the system embodying my invention, itis unnecessary for the operator to establish an additional con-- trol from the C. T. C. machine to the switch lock Awhen a train occupying the main track wishes to enter an electrically locked switch, as the switch will beunlockedautomatically by Virtue of the occupancy of the releasing track section OT.

The switch lock control apparatus shown in Fig. 3 is adequate if. not more than two pairs cut section location F is similar to that described Y for the electric switch lock at location H. In

l the cut section arrangement, as in the signal arrangement just described, separate EHR. and

WHR relays with their individual decoding transformers are required to secure an unlock for the electric switch lock. The decoding circuits in 'this instance are .normally deenergized and ybecome energized when relay 1S picks up and closes its front contact I 48 following the operationy of the knife switch IKS to the right so as to energize wire |v49`.

It will be observed that two relays ,'IRWSR and -TLWSR have been provided one at each end of the stretch for the control of the electric switch v locks. The relay to be selected and energized when a Switch is to bo unlocked wm be the one switch lever 'l also in the L position, a code is sent out to the field station unit at location K for energizing terminal 82 and relay-1LWSR. but code is not sent out to the eld station unit at location D at the other end of the stretch. The latter unit will receive code and relay IRWSR will become energized only after both levers 8 and 'I occupy their R position (for eastbound traic) It is not necessary, however, that the coding circuits on the control machine at in Fig. 4 of Sh. 2 may be used for the control of the ES relay. This ligure shows the control larrangement for the eastbound stick relay (ES),

but it will be understood that a similar control o would be used for the westbound stick relay (WS) In the arrangement shown in Fig. 4, the iirst train through the block will energize relay ES. Relay ES will remain energized through its stick circuit until the block is vacated when coded track circuit energy of negative polarity will be received to energize relay EHR. Before relay ES opens its front contacts, a circuit is complete through reverse polar contact ISI (closed to right) of relay ETRA to energize relay ESA which will lbe retained in its Ienergized position by the same circuit just traced except through a front contact of relay ESA instead of relay ES. Relay ESA will remain energized until the train clears the, block, so that following trains will cause relay ES to be energized over the front contact |50 of relay ESA rather than the normal polar contact I5I of relay ETRA which will remain in its reverse position until the train clears the block. Of course, with the arrangement of Fig. 4, if the block is occupied by an eastbound train and a second train enters at the switch lock SW shown in the track diagram of Fig. 4a, the ES relay at signal 4 location may be energized even though this second train proceeds in the westbound direction after entering the main track at the switch lock. The lever circuits shown in 1b will, however, retain coded I energy in the block for an eastbound move until such time as both trains clear the block so that no diilic lty would -be'experienced through improper operation of the following stick relays.

From the foregoing description it will be apparent that I have provided a signaling system for a stretch of single track, two-direction railway which combines C. T. C. control with coded wayside signaling in a novel manner such that no control line wires (except those involved in highway crossing control) apart from the C. T. C. code line are required. Since the system is 'of the normally deenergized type, it lends itself readily to primary battery operation in territory where the ordinary commercial power sources are not available. Operation of a'traic lever at a central control location establishes the permitted direction by applying code at the exit end of the stretch, which code when cascaded to the entrance end checks unoccupancy of the stretch and permits clearing of the entrance signal. Passage of the train approach-energias the signals as these are approached, tor the purpose of conserving the energy ot the power supply source. The approach relays are included in the control for the following directional stick relays so as to provide proper directional control since .the use of the advance track circuit for this purpose, as in the usual case, is not possible be- -cause 4of the normally deenergized condition of the track circuits of the system. Deenergization of the'se track circuits brings on the normal condition of the system and cannot, therefore, be used for the directional control function. Polariredtraclrcircuitcodeisusedtodetecttheocpletely out of the stretch. The apparatus embodying my invention also provides for proper controlof highway crossing apparatus through the use of an additional code such as 20 code for detection purposes. Moreover, the apparatus embodying my invention lends itself readily to the control of velectric switch locks without any line wires other than those required for the C. T. C. line circuit.

Although I have herein shown and described only a few forms of railway traillc controlling ap.

paratus embodying my invention, it is'understood that various changes and modications may be made thereinwithin the scope of the appended' claims without departing from the 1spirit and scope of my invention.

jHaving thus described my invention, what I claim is: "tf" 1. In combination with a stretch of single u track over which traille may move in either di.

rection, said stretch being divided into a plurality voftrack circuit sections, a traillc direction control relay, manually controlled means at a control oiilce for operatingsaid -traillc direction relay, means effective when said tramo direction relay is operated for cascading current impulses of a track circuit code fromthe exit end of said stretch for a given tralc direction over said sections to the entrance end for establishing said traic direction, an entrance .g-fsignal, code responsive means operated in nse to the code received at the entrance end, nieans controlled from said cnice and eiective when said code responsive means is operated for clearingv said entrance signal, and means at said control omce eilective when said entrance signal is cleared for, preventing a reversal of the established tramo direction. j

2. In combination. with a stretch o! single track overwhich trame may move in either direction, manually controlled means at a control mitm coded rau current impulses from said e omce, direction selecting means in the trackway responsive to operation of said manually confor establishing trame' in a given direction-inver said stretch, means adjacent the exit end of said stretch for said-given direction and controlled by said direction selecting means for transmitting coded rail current impulses Y from said exit end to the entrance end, an entrance signal. control means operated in response l 9 entrance end, means controlled from said loiilce y and eiiective when said control means is operated for clearing said entrance signal, and means at said control omce eiective when said signal is cleared for preventing the reversal of said given tramo direction.

3. In combination with a stretch of single track over which traiiic may move in either direction, a manually controlled selector at a control oice having a rst and a second position, trafilc direction control means in the trackway selectivelyresponsive to operation of said selector to said rst or said second position for establishing traiilc in one or the other direction respectively over said stretch, means adjacent one end of said stretch governed by said trailic direction control means and eii'ective when the selector is in its nrst position for transmitting coded rail current 'impulses from said one end `to the other end of said stretch. means adjacent said other end also governed by said tramo direction control means and eiIective when said selector occupies said second position for transmitting coded rail current impulses from said other end to said one end of the stretch, an entrance signal at each end o f the stretch, control means at each end operated in response to the receipt of said coded current at the associated end of the stretch, means at each end controlled from said oillce and eiIective when the associated control means is operated for clearing the entrance signal at that end, and means at= the control olce effective whenl either signal is cleared for preventing va reversalfof the `established traiilc direction.

4. In combination with a stretch of Vsingle track over which tariilc may move in either direction, a normally deenergized` traiilc direction relay adjacent the exit end of said stretch for a given tradic directionfmanually controlled means at a control olilce for energizing said traflic direction relay, means eiective when said, traillc ection relay is energized for transmitting cod rail current impulses from said exit end to the entrance end of said stretch for establishing trame in a given a direction, means eirective when said coded rail current is received at saidentrance end for permitting traillc to enter said stretch, and means eilective during occupancy o! said stretch tor maintaining said trame direction relay energized lo lto thereby retain the'e'stablished trame direction.

5. In combination with a stretch of single track over which traiilc may move in either direction, a

normally deenergiaed westbound traiilc direction control relay adjacent one end ot said stretch, a

normally deenergired eastbound traiilc direction I .control relay adjacent the other4 end oi said stretch. manually controlled means for selectively energizing said westbound or said 'eastbound direction control relay. a first and a second nor- .mally deenergiaed codedetecting relay adjacent said oneand said other end of said stretchre, f spectively, means including a front contact of said westbound direction control relay and a back contact of said first code detecting relay for transl- 1e tact of said eastbound direction control relay anda 'back contact oi' 'said second code detecting relay tor transmitting coded rail currentimpulses from said other end to said one end of the y stretchto thereby energize saldiirst' code detect-J tothereceiptorsaidrailcurrentimpulsesatnldfrl relay and trame in the eastbound 1.0 Y direction over said stretch, whereby when either code detecting relay is energized its associated back back contact is open so as to prevent code transmission from that end and so prevent a reversal oi.' the established tramo direction.

6.I In combination with a stretch of single track rail current'impulses from said one end to saidv other end of the stretch to thereby energize said code detecting relay and establish tramo in a given direction over said stretch, and means ef-A fective when said code detecting relay is; energized' Iori` preventing a reversal of said given tramo. direction. D v

7. In combination with a stretch of single track over which traflic may move in either'direction.

cuit for said directional stick relay including a front contact of said slow acting repeater relay,

a normally deenergized traiilc direction control relay adjacent one end of said stretch, manually controlled means for energizing said direction control relay, means eiiective when said direction control relay is energized for transmitting'` coded rail current impulses from said one end to said .other end .of thev stretch `to thereby establish tramo in'a given direction over said stretch, a

normally deenergized stick relay adjacent said other end of the stretch, meansl effective when atrain enters said stretch at said other end for energizing said stick relay, and means eiective when said stick relay is energized for preventing a reversal of said given trafiic direction. 8. In combination with a stretch oi single track over which trafllc may move in either direction, a

normally dee'nergized trailic direction control relay adjacent one end of said stretch, manually controlled means for energizing said direction control relay, a normally deenergized code detecting relay adjacent the other end o! said stretch,

an ventrance signal adjacent said other end.

`means eiective when said directioncontrol relay is energized for transmitting coded rail current impulses from said one end to said other end ofV the stretch to thereby energize said code detecting relay-so as to establishtramc in a given direction over said stretch and permit clearing of said entrance signal, a normally deenergized stick relay adjacent said other end of the stretch,

' means effective when a train accepts said entrance signal and enters the stretch at said other end for energizing said stick relay, l effective when said stick relay is energizedfor preventing a reversal of said given tranlc direction.

-, `9. In combination with a stretch of single track over which traffic may move. in either direction, an

intermediate signal location within said stretch, 'a rst track circuitlsection within said. stretch on one side of said intermediate signal location,

va second track circuit section also within said said nrst to said second section for establishing d meansv `following trackrelay for said iirst section for cascading coded rail current impulses over said stretch from said lfirst to said second section for establishing traflic in a given direction so as tovpermit a train to enter' said stretch and approach said intermediate signal, a slow acting repeater relay which remains energized when said track relay is following code, a directional stick relay, a code repeater relay controlled over a front contact oi.' said slow acting repeater relay, an, approach relay iorsaid second section which becomes energized when the train approaches within a predetermined distance of said intermediate signal, a pick-up circ'uitfor said directional stick relay including a front contact of said approach relay and a front contact of said slow acting repeater. relay, and trailic controlling apparatus common to both said sections controlled -by said code repeater relay. A l

.11. In combination with a stretch\ of single -track over which traino may move in either direcvrelay for vsaid rst section, an eastbound code i'ollowing track relay for said second section,

means for supplying coded rail current impulses to said first section when the traffic direction is Y westbound to operate said westbound track relay, means for supplying coded rail current im- .repeater relay and havinga second energizing traiiicin a given direction, a slow acting repeater relay energized over a front contacto! said 'code 'following track relay, a directional stick relay, a code repeater relay energized over a iront contact oi said slow acting repeater relay, a pick-up cirpulses to said second section when the tramo direction is eastbound to operate said eastbound track relay,- a westbound and an eastbound slow acting repeater relay for said westbound and said eastbound track relay respectively, a westbound directional.stick relay having a pick-up circuit including a front contact of said westbound .repeater relay, an eastbound directional stick' relay having a pick-up circuit which includes airont contact of said eastbound repeater relay, a code repeater relay having a first energizing circuit` which includes afront contact of said westbound circuit which includes aback contact of said west- 'bound repeater relay and a front contact ofy said eastbound repeater relay, and trame controlling apparatus common to both said sections controlled by said code repeater relay.

l2. In combination with a' stretch of track over which traflic may move in either direction, an intermediate signal location within said stretch, a rst track circuit section within said stretch on one side of said intermediate signal location, a second track circuit section also within `said stretch on the other side of said intermediate sig# nal location, a westbound traillc direction controlv relay for supplying' rail current impulses of a flrst or of a second code to said mst section in accordance with traffic conditions in advance thereof to

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