US2264533A - Railway track circuit apparatus - Google Patents

Description

Dec. ,2, 1941. T JOHNSTON 2,264,533

RAILWAY TRACK CIRCUIT APPARATUS Filed May 25, 1940 2 Sheets-Sheet 1 P L ,2 A

Hi5 A'I-rdRN Y Dec. 2, 1941.

A. T. JOHNSTON v RAILWAY TRACK CIRCUIT APPARATUS 2 Sheets-Sheet 2 Filed May 25, 1940 F a 4 r LEE/5 7 6 6 7 I0 475 TB] 232 I 11 1 cl v T23 12? Fig. 4.

l 222' 4 B ZJ 21 I4 I 5% 5 i m, 5 773 14 11- BX c2 14 m 31M HLS' ATTORNEY Patented Dec. 2, 1941 STATES ATENT OFFICE RAILWAY TRACK CIRCUIT APPARATUS Application May 25, 1940, Serial No. 337,261

Claims.

My invention relates to railway track circuit apparatus, and it has particular reference to the organization of such apparatus into railway track circuits of the class utilizing alternating track circuit current.

It is well known that thin films or coatings of relatively high resistance present on the surfaces of track rails must be punctured by the rail voltage in order to enable a track circuit incorporating such rails to be shunted by a train. Such surface films are present to some extent on all track rails, but most frequently reach an objectionable thickness or condition on the rails of turnouts, crossovers, and other portions of track not often used, with the result that such portions of track where thick hard-to-puncture surface film conditions obtain are extremely difficult to shunt, particularly when low rail voltages such as are customary in track circuit practice, are employed. It has been found that when the rail voltag throughout the section is increased to aid in puncturing the rail film, the leakage across the track ballast tends to become excessive and other disadvantages are introduced.

I have found that relatively high rail voltages need be employed only in those portions of a track circuit such as turnouts, etc. most difiicult to shunt due to rail film conditions and/or at the entrance end of a section. Such high rail voltages aid in puncturing the track rail film and thus insure the establishment of a train shunt on the track relay. After the relay once releases, it may be held released by the train shunt in response to a lower applied rail voltage inasmuch as the effectiveness of the train shunt on a released relay is greater than on a picked up relay, due to the differences in energy .levels at which a track relay picks up and releases.

In View of the foregoing and other important considerations, it is an object of my present invention to provide a track circuit utilizing the usual low rail voltages throughout the major portion of the circuit and incorporating means for increasing the track rail voltage available at the entrance end and/or at such portions of a section where high resistance rail film conditions obtain.

Another object of my invention is to provide a track circuit in which the rails of a fouling section are interposed in series with the rails of the associated track section by means of inductive couplings.

An additional object of my invention is the provision of track circuits incorporating novel and improved means for improving the operation of alternating current track relays.

A further object of my invention is to provide novel and improved track circuits of the type utilizing alternating track circuit current.

The above mentioned and other important objects and characteristic features of my invention which will become readily apparent from the following description are attained in accordance with my invention by subdividing a track section into subsections or zones by means of oneor more insulated joints, and by utilizing transformers having a greater number of turns in one winding than in the other to couple together the rails of adjoining zones of the track section. The locations at which the insulated joints are positioned are selected to subdivide the section into a certain zone or zones in which a relatively high rail voltage is required to aid in shunting the associated track relay, and another zone or other zones in which the train shunt established under lower rail voltages is effective to shunt the track relay. The ratio of the number of turns in the two windings of the transformers and the connections of such windings with the track rails are selected to increase the rail voltage normally supplied to the rails of the section, or to decrease such rail voltage from its increased value to its normal value, in accordance with the rail surface film conditions and/or the location in the section of the zone to be supplied. More specifically, the turn ratios of the transformers are such that zones first entered by a train in the section and/or zones having relatively severe rail surface films are provided with relatively high rail voltages, while zones having less severe surface films and/or zones occupied by the train after the relay of the section has been released, are provided with relatively lower rail voltages.

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

In the accompanying drawings, Fig. 1 is a diagrammatic view illustrating a preferred form of apparatus embodying my invention. Figs. 2, 3, 4 and 5 are each modified forms of the apparatus represented in Fig. 1, and each also embodies my invention.

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

Referring first to Fig. I, the reference characters A and B designate two tracks of a stretch of multiple track railway. Track A is divided by insulated joints. 2 into an insulated section D-E', and similarly track 3- is divided by insulated joints 2 into an insulated. section F G.

The sections D-E and FG are connected by a crossover C, comprising the usual switches SA and SB and the usual track frogs and connecting track rails. Crossover C is divided by insulated joints 3 located in the rails at a point H substantially midway between the switches, into two portions, one for section DE and the other for section F-G. As is readily apparent from an inspection of Fig. 1, insulated rail joints 4 are positioned in the switch rails of switch SA to form that portion of crossover C associated with section DE into a short insulated track section extending from such insulated joints 4 to the insulated joints 3 at point I-I. Similarly, other insulated joints 4 are interposed in the switch rails of switch SB to form that portion of the crossover associated with section F-G into a short insulated track section extending from such other insulated joints 4 to the insulated joints 3 at point H. It should be noted that one rail of eachportion of crossover C is electrically connected to one track rail of the associated section, and that the other rail of the corresponding portion of crossover C is electrically insulated from each of the rails of the associated section. For example, it can be seen from an inspection of Fig. 1 that the upper rail of the left-hand portion of crossover C (as viewed in the drawing) is electrically connected to the lower rail of section DE through the medium of the frog of switch SA (and additionally connected, if desired, by bonds not shown), while the lower rail of the corresponding portion of the crossover is insulated by insulated joint 4 from the lower rail of section DE.

The reference characters TRA and TRB desi nate track relays connected respectively to the rails of sections DE and FG, and the reference characters TTA and TTB designate sources of alternating current connected respectively to former having its secondary winding connected to the rails of the associated section in series with the usual current limiting impedance 5, and its primary winding connected to a suitable source of alternating current, such as a generator not shown but having its opposite terminals designated in the drawing by the reference characters BX and CK.

The reference characters TA and TB designate transformers having two windings 6 and 1, one winding 1 of which has a greater number of turns than the other winding 6. One winding, 6, of transformer TA is connected across the track rails of section DE and hence is energized by the voltage applied to section DE by transformer TTA, it being noted that the connection of the lower terminal of winding 6 to the lower rail of section DE is completed through the top rail and frog of crossover C. The other winding 1 of transformer TA is connected across the rails of the insulated section formed in that portion of crossover C associated with section D-E. Similarly, winding 6 of transformer TB is connected across the rails of section FG and winding 1 is connected across the rails of the insulated section formed in the other portion of crossover C associated with section FG.

The voltages applied by transformers TTA and TTB to sections DE and FG, respectively, are

.effective normally to hold relays TRA and THE energized and such voltages in windings 6 of transformers TA and TB cause electromotive forces of relatively high voltage to be induced in windings 1 of such transformers and to be applied to the rails of the portions of crossover C. Whenever either section is entered by a train, the relay associated with such section is shunted and accordingly such relay is caused to be releasedv Also, a vehicle on crossover C causes shunting of one or both of relays TRA and TRB, according as the vehicle or train is in one or both of the portions of crossover C associated with sections DE and FG. Inasmuch as an insulated section of a portion of crossover C is connected in parallel to the relay of the associated track section, a vehicle on the crossover C in order to shunt the associated track relay must be effective to establish a train shunt sufiiciently low in resistance to by-pass the track circuit current away from the track relay. This low resistance train shunt is established for crossover C in spite of the relatively thick surface films usually encountered on its rails because of infrequent movement of trains thereover, due to the puncturing action of the relatively high rail voltage supplied from winding 1 of step-up transformer TA or TB as the case may be. It can be seen, therefore, that the rail voltages of sections DE and F-G may be maintained at the usual low values sufficient to enable a train on the relatively clean rails of such section to establish an effective shunt, and these low rail voltages of course prevent excessive leakage across the track ballast. By use of the step-up transformers TA and TB, the relatively low rail voltages sufficient for clean rail surfaces are stepped up to an increased value suflicient to puncture the relatively severe rail films that may be encountered on the track rails of crossover C. This permits an effective shunt to be established by a train on the crossover, without causing an excessive leakage across the ballast of the crossover due to the limited length of the rails of the crossover.

It follows, therefore, that I have provided means whereby different zones of a track electrically insulated from each other are incorporated into a track circuit, and in which the rail voltages available in the several zones are proportioned with respect to the rail film conditions usually encountered, in such manner that relatively high voltages are available in track zones where such voltages are required to assist in establishing an effective train shunt, and lower rail voltages are applied to zones wherein clean rail surfaces permit efiective shunts to be established under such relatively low voltage conditions.

It is, of course, obvious that the apparatus of Fig. 1 may be applied to the rails of a fouling section connecting the switch rails to a passing or siding track, and in which case the zone in which relatively high voltages are applied would include the rails of the fouling section and extend to the insulated joints positioned at the fouling point.

Another means for increasing the shunting action of a vehicle on the rails of a fouling section is shown in Fig. 2. Referring now to Fig. 2, the lower rail (as viewed in the drawing) of track B is divided by an insulated joint 2a into two subsections or zones insulated from one another. A passing or siding track Al is connected to track B by switch SB and fouling section J, which section extendsfrom insulated joints 3 positioned at the fouling point of track Al, to

insulated joints 4 located at the switchrails of switch SB. Track transformer TTB and relay TRCB are connected to the rails of section FG at opposite ends of the section and relay TRB is energized over a track circuit in which the rails of section J are interposed, in a manner to be explained in detail presently, in series with the rails of section F-G by couplings eifected by two transformers TB! and T32. These transformers are preferably similar to transformers TA and TB previously described in that each is provided with a winding 1 having more turns than a winding 6.

The rails of section J are coupled with the rails of section F-G by connecting winding 6 of transformer TBI across the rails of section F-G intermediate insulated joint 2a and the track current source TTB; connecting winding 1 of transformer TBI across the rails of section J at one end of the section adjacent insulated joints 3 at the fouling point of track A1; connecting winding l' of transformer TBZ across the rails of the other end of section J; and connecting winding 6 of transformer TBZ across the rails of section F-G intermediate joint 2a and track relay TRB.

The energy supplied to the track rails of section FG from track transformer TTB is prevented by insulated joint Zn. from flowing through the two track rails in series to energize relay TRB, but such energy is provided with a circuit which extends from one terminal of the secondary winding of transformer TTB through the lower rail of section FG, winding 6 of transformer T'Bi the common connection of windings 6 and l of transformer TBI to the lower rail (as viewed in the drawing) of section J, the lower rail of section J and the upper rail of section F-G (electrically connected to the lower rail of section J through the frog of switch SB and additionally connected, if desired, by suitable bonding wires) to the other terminal of the secondary winding of transformer TTB. The current supplied to winding 6 of transformer TBi over the just traced circuit induces an electromotive force in winding I of transformer TBI, and this electromotive force is provided with a circuit comprising the connection of one terminal of winding 1 of transformer TB! to the lower rail of section J, the lower rail of section J, the connection of one terminal of winding 1 .of transformer TB? to the lower rail of section J, winding 7 of transformer TBZ, the connection of the other terminal of winding 1 of transformer TB2 to the upper rail of section J, the upper rail of section J and the connection of the other terminal of winding 1 of transformer TBI to the upper rail of section J. The current supplied to winding 1 of transformer TB2 from winding '1 of transformer TB! over the just traced circuit causes an electromotive force to be induced in winding 6 of transformer T132, and this electromotive force energizes relay TRB over a circuit extending from one terminal of winding E3 of transformer TBE through the connection of that terminal to the lower rail of section F-G, the lower rail of section F-G, the winding of relay TRB, the upper rail of section F-G through the electrical connection of that rail to the lower rail of section J and the connection of the lower rail of section J to the other terminal of winding 6 of transformer TB2.

It is readily apparent that the rails of section J are interposed in series with the rails of section Fr-G in the circuit of relay TRB, so that if :a' vehicle or train is on either section F--G or section J, the trackcircuit current is shunted away from relay TRB. It isalso apparent that since the rails of section J are in series circuit with the rails of section FG, the circuit of relay TRB is of the closed circuit type wherein thereis'provided acheck upon the rails of both sections. It is further apparent that the rails of section J are interposed in series with the rails of section F G by means of inductive couplings effected by transformers TBI and T32, h nce by properly proportioning the parts of these transformers the rail voltage in section FC-i may be maintained at the usual low value sufficient under clean rail surfaces of such section to permit ready shunting of the track relay,

and the rail voltage of section VJ may be increased or raised to a value sufficient to enable the train or vehicle on section J to effect a low resistance shunt irrespective of the relatively thick rail films usually encountered there and thus establish a shunt on relay TRB.

Another modification of theapparatus of Fig. l is represented in Fig. 3, wherein sections D--E and F--G of tracks A and B are each divided into two outer zones separated from each other by an intermediate zone which includes the associated switch of crossover C. As will be made clear presently, the usual low rail voltages are applied in the outer zones of sections DE and FG, and relatively high rail voltages are applied in intermediate zones of these sections to impress corresponding high rail voltages across the portions of the connecting rails of crossover C connected in multiple with the rails of the intermediate zone.

Referring'now to Fig. 3, one rail of track A is divided by insulated joints 2a disposed one on either side of the location of switch SA, into adjoining zones or sub-sections electrically insulated from one another, and similarly track B is divided by insulated joints 2a, disposed one on either side of switch SB into electrically insulated zones. Transformers TA! and TA2 are provided one for each insulated joint 20!. of section D-E to inductively couple the rails of the adjoining zones of such section, and track 5 also is provided with transformers TBI and T32 one for each insulated joint 2a of section F-G. The associated or left-hand portion, as viewed in the drawing, of the lower rail of crossover C, which is divided by insulated joints 3 at H into two insulated portions, one for track A and the other for track B, is connected by a bond wire to the upper or insulated rail of the intermediate zone of section D-E, and similarly the right-hand portion of the upper rail of crossover C is connected by a bond wire to the lower or insulated rail of the intermediate zone of section F-G.

As is readily apparent from an inspection of Fig. 3, the transformers inductively coupling the rails of adjacent zones of section FG are connected to the rails of the associated section in such manner that the rail voltage in the outer zone adjacent the track circuit current source, which rail voltage is substantially that established across the terminals of the secondary winding of track transformer TTB, causes an electromotive force of higher voltage to be applied by winding 1 of transformer TBI to the rails of the intermediate zone of section FG defined by the insulated joints 2a interposed in the lower rail of the section, and this higher rail Voltage impressed across winding 1 of transformer 'I'B2 causes a lower rail voltage to be applied by winding 8 of the latter transformer to the rails of the right-hand zone of section FG. It is readily apparent, therefore, that since the rails of the associated portion of crossover C are connected in multiple with the rails of the intermediate zone of section F-G, the higher rail voltage available in crossover C enables a train or vehicle. in the associated portion of the crossover to establish a shunt on relay TRB in spite of the relatively thick films usually encountered on the rails of such crossover. Similarly, it can be seen from an inspection of the drawing that by means of transformers TA! and TAZ there is provided a relatively high rail voltage in the intermediate zone of section D-E so that a train or vehicle on the associated portion of crossover C is enabled to be effective to shunt relay TRA. It follows that my invention permits the voltages applied in different zones of a section to be adjusted to the values required by the shunting conditions in such zones as influenced by rail film conditions. By employing a relatively high voltage only in a zone or zones where it is necessary, and by employing lower rail voltages in the major portion of the section, the power losses and other disadvantages due to excessive leakage through the track ballast are obviated.

Fig. 4 represents the apparatus of Fig. 3 applied to track B modified in such manner that the rail voltages available in the outer zones of Fig. 4 are higher than those available in the intermediate zone. This modification represented in Fig. 4 preferably is employed where a section does not include a turnout or crossover, and permits a train or vehicle entering section F-G to establish quickly a shunt on relay TRB due to the high rail rail voltage available when the section is first entered.

As is readily apparent from an inspection of the drawing, the apparatus of Fig. 4 is substantially similar to the apparatus previously described in connection with Fig. 3, except that the connections of transformers TBI and TB2 are reversed in Fig. 4. That is to say, in Fig. 4 the high voltage winding 1 of transformer TBI, for example, is connected to the rails of the left-hand (as viewed in the drawings) outer zone of section F-G and low voltage winding 6 of the transformer is connected to the rails of the intermediate zone of the section.

It can be seen that since the rail voltages available in the outer zones of section F--G of Fig. 4 are relatively high, a train or vehicle entering such section in either of the outer zones will quickly establish a shunt on relay TRB. After such shunt has been established and the relay released, the train then occupies a zone where a lower or the usual rail voltage is avail able. This rail voltage might be insufficient under certain ballast and/or track surface film conditions to break down or puncture the rail film to an extent that permits the train to establish a train shunt sufficiently low in resistance to shunt and release relay TRB, but due to the relative differences in energy reuired to hold up and to pick up the relay, the lower rail voltage in the intermediate zone of section FG of Fig. 4 is effective to create a train shunt of the order sufficient to maintain the relay released. It follows, therefore, that the apparatus of Fig. 4 also provides means for adjusting the track rail voltages in different zones of a section to the values required for releasing or for maintaining the track relay released, and that it permits the restriction to relatively short zones of the high rail voltages such as are required to puncture a rail film and thus enable a relatively low resistance train shunt to be established for shunting and releasing a track relay, thereby obviating excessive leakage across the track ballast due to such high rail voltages.

In addition, the apparatus of Fig. 4 provides further means for improving the operation of relay TRB, by increasing the energization of the relay after it picks up. Improved operation of relay TRB is effected in this manner due to the fact that an alternating current relay picks up in response to an energization considerably lower than that required to compress its front contacts and thus obtain a proper contact pressure. As shown in Fig. 4, the means for improving the operation of relay TRB comprises connecting in circuit with relay TRB an impedance ID in the form of a primary winding of a transformer ll having a secondary winding I2 connected in a low resistance or short circuit path over front contact [3 of relay TRB. When section FG is occupied and relay TRB is released to open its front contact [3, the reactance of winding I0 is relatively high and the current to relay 'I'RB is therefore limited not only by the train shunt in the section but also by winding 10. Relay TRB is adjusted with respect to the reactance of winding III in such manner as to be effectively energized and picked up when the shunt is removed from the relay, and when front contact I3 closes, the current drawn by winding l2 decreases the reactance of winding H! and thus increases the energization of relay TRB. This increased energization of relay TRB is effective to compress the front contact of the relay and thus it improves the operation of the relay.

It is, of course, obvious that if trains travel on track B of Fig. 4 in but a single direction say, for example, from right to left as viewed in the drawing, then but a single outer zone in which relatively high rail voltages are applied, would be required at the relay end of the section. This single zone of course would be first entered by a train so that such train would establish an effective shunt of relay TRB due to the relatively high rail voltage prevalent in the entering zone and the remainder of the section could then be supplied with track circuit current of the usual low voltage.

I have represented in Fig. 5 the system of Fig. 4 modified in the manner just described to provide a high voltage zone adjacent only the entrance end of track B and in which, as indicated by an arrow in Fig. 5, traffic normally moves from right to left. A further modification of the system of Fig. 4 is that in Fig. 5 my invention is illustrated as being provided for a stretch of electrified trackway, wherein impedance bonds I4 are provided for each pair of insulated joints 2 to enable electric propulsion current to be transferred around the joints and thus permit the track rails to form a portion of the return path of such propulsion current.

Referring now to Fig. 5, the upper rail of section F-G of Fig. 5 is provided adjacent entrance end G with an insulated joint 2a. Impedance bond I4 is connected across the rails of section F-G intermediate joint 2a and the other end of the section, and such bond is provided with another winding I5 connected to the rails of section F-G intermediate joint 2a and the entrance end G of section FG. The mid tap terminal of bond l4 connected adjacent joint 2a of section F--G is of course connected to the mid tap terminal of bond I4 connected to the rails of track B at the other side of joints 2 positioned to define the entrance G of section FG.

It is readily apparent from an inspection of the drawings that impedance bonds l4 function in the usual manner to transfer propulsion current around insulated joints 2 and 2a. in track B, and that the track circuit voltage impressed across bond l4 at joint 2a of section F-G causes an electromotive force of increased voltage to be induced in its associated winding l5.

This increased voltage applied by winding IE to the rails of the insulated zone adjacent track a relay 'IRB at the entrance end of section F-G of course functions to assist a train entering section F-G in establishing an effective shunt on the track relay. It follows, therefore, that my invention provides means for utilizing an impedance bond as one winding of a voltage changing transformer inductively coupling the rails of adjacent zones of a section of track.

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

Having thus described my invention, what I claim is:

1. In combination, a section of railway track, a turnout associated with said section and having one rail thereof electrically connected to one rail of said section and the other rail thereof separated from each of the rails of said section by insulated rail joints, a track relay and a source of alternating track circuit current connected to the rails at opposite ends of said section, and means for impressing across the rails of said turnout a voltage derived from the rails of said section and higher than the voltage of said section whereby to enable a vehicle on said turnout to effectively shunt said track relay.

2. In combination, a section of railway track provided with a track circuit comprising a track relay and an alternating current source connected to the rails at opposite ends of the section, a turnout associated with said section and havin at least one rail separated from the rails of said section by insulated rail joints, and means for inductively coupling the rails of said turnout to the rails of said section for applying across the rails of the turnout a voltage higher than the voltage in said section, said higher rail voltage being effective to puncture the rail film on the rails of said turnout and establish an effective shunt on said relay when such rails are shunted by a train.

3. In combination, a section of railway track, a turnout associated with said section and having at least one rail thereof separated from the rails of said section by insulated rail joints, a source of alternating current and a track. relay connected to the rails at opposite ends of said sections, and a step-up transformer having its primary winding connected across the rails of said section adjacent said turnout and its secondary winding connected across the rails of said turnout, whereby to apply across the rails of said turnout a voltage higher than the voltage of said section to assist a train or vehicle on said turnout in establishing an eifective train shunt on said track relay.

Y 4. In combination, a-section'of railway track, a turnout associated with said section and having at least one rail thereof insulated from the rails of said section, a track relay and a source of alternating current connected to the track rails at opposite ends of said section, and inductive coupling means for interposing the rails of said turnout in series with the rails of said section in the circuit of said relay.

5. In combination with a stretch of railway track divided by insulated rail joints into successive adjoining track sections each having a source of alternating track circuit current and a track relay connected to the rails at opposite ends of the section, said sections being provided with impedance bonds for each' pair of rail joints, another insulated joint disposed in one rail of each section intermediate one of said bonds and the insulated joints defining the relay end of such section, and a secondary winding. for said one bond connected to the rails of such section intermediate said one joint and said joints ,deflfining the relay end of such section, said secondary winding being proportioned to apply across the rails at the relay end of such section a voltage derived from the track circuit source of such section and higher than the voltage of said source.

6. In combination, a section of railway track, a turnout having one rail thereof electrically connected to one rail of said section and the other rail thereof insulated from each of the rails of said section, a track relay and a source of alternating track circuit current connected to the rails at opposite ends of said section, and means for connecting the rails of said turnout in multiple with the rails of said section in the circuit of said relay, comprising a, step-up transformer having a primary winding connected across the rails of said section and a secondary winding connected to the rails of said turnout at the end remote from said section.

'7. In combination, a section of railway track, a turnout having one rail thereof electrically connected to one rail of said section and the other rail thereof insulated from each of the rails of said section, a track relay and a source of alternating track circuit current connected to the rails at opposite ends of said section, and means for connecting the rails of said turnout in multiple with the rails of said section in the circuit of said relay, comprising a step-up transformer having a primary winding connected across the rails of said section through a circuit including the said one turnout rail and a secondary Winding connected to the rails of said turnout at the end remote from said section.

8. In combination, a section of railway track, a turnout associated with said section and having at least one rail thereof insulated from each of the rails of said section, a track relay and a source of alternating current connected respectively to the rails at opposite ends of said section, an insulated joint in at least one rail of said section intermediate its ends, and means for connecting the rails of said turnout in series with the rails of said sectionin the circuit of said relay, comprising a first transformer having a winding connected across the rails of said section intermediate said joint and said source and having another winding connected to the rails at one end of said turnout, and another transformer having a winding connected across the rails at the opposite end of said turnout and having another winding connected across the rails of said section intermediate said insulated joint and said track relay.

9. In combination, a section of railway track, a turnout associated with said section and having at least one rail thereof insulated from each of the rails of said section, a track relay and a source of alternating current connected respectively to the rails at opposite ends of said section, an insulated joint in at least one rail of said section intermediate its ends, and means for connecting the rails of said turnout in series with the rails of said section in the circuit of said relay, comprising a step-up transformer having a winding connected across the rails of said. section intermediate said joint and said source and having another winding connected to the rails at one end of said turnout, and a step-down transformer having a winding connected across the rails at the opposite end of said turnout and having another winding connected across the rails of said section intermediate said insulated joint and said track relay.

10. In combination, a section of railway track, a turnout having one rail thereof electrically connected to one rail of said section and the other rail thereof insulated from each of the rails of said section, a track relay and a source of alternating current connected to the rails at opposite ends respectively of said section, an insulated joint in the other rail of said section, a transformer having a winding connected across the rails of said section intermediate said source and said insulated joint over a circuit including said one turnout rail and having another winding connected to the rails at one end of said turnout, and another transformer having a winding connected to the rails at the opposite end of said turnout and having another winding connected across the rails of said section intermediate said relay and said insulated joint over a circuit including said one turnout rail.

ALLAN T. JOHNSTON.

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