US2590924A

US2590924A - Subdivided coded railway track circuit

Info

Publication number: US2590924A
Application number: US767199A
Authority: US
Inventors: Herman G Blosser
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1947-08-07
Filing date: 1947-08-07
Publication date: 1952-04-01
Anticipated expiration: 1969-04-01

Description

April 1, 1952 H. G. BLOSSER SUBDIVIDED CODED RAILWAY TRACK CIRCUIT Filed Aug. '7, 1947 INVENTOR. G. Blosser Harm 1m: ATTORNEY Patented Apr. 1, 1952 SUBDIVIDED CODED RAILWAY TRACK CIRCUIT Herman G. Blosser, Pittsburgh, Pa., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application August 7, 1947, Serial No. 767,199

- 11 Claims.

My invention relates to railway signalingapparatus and particularly to improved means for indicating at an intermediate point in a track section equipped with coded track circuit apparatus when a train enters the section.

My invention may be applied to coded track circuits comprising a code following relay at the entrance end of a section together with means located at the exit end of the section for supplying, to the track relay over the section rails impulses of master code energy which are separated by intervals during which noenergy is supplied.

Where a track section includes an intersection with a highway it maybe desired to provide warning signal means adjacent the highway to warn users of the highway of the approach of a train, and to provide means governed by occupancy of the track section for controlling the signals which protect the crossing.

It is an object of this invention to provide, improved means adapted for use in a track section equipped with coded track circuit apparatus for indicating at an intermediate point in the track section when a train enters a section from either end.

Another object of my invention is to provide means of the type described which may be employed to detect occupancy of a portion only of the tracksection.

A further object of my invention is toprovide means of the type described which may be employed to selectively detect occupancy ofthe portion of a track section at'either side of a highway intersection. I I

A further'object of my invention is to provide improved means of the type described employing aminimum number of insulated rail joints.

Other objects of my invention and features of novelty will be apparentfrom the following. description taken inconnection with. the accompanying drawings.

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

In practicing my invention, I provide .means'at the exit end of the track section for supplying to the section rails impulses of master code energy ,to operate the code following trackrelay at the entranceend of the track section, while the track relay hasassociated therewith means for supplyingimpulses of energy to the section rails when theltrack; relay is not following code.

An intersection with a highway is located at an intermediate point in the track section and an insulated joint is located at this intersection,

while a resistor is connected around this joint. A first code following detector relay is connected across the section rails on the side of the joint nearest the track relay, and a second code following detector relay is connected across the section rails on the side of the joint farthest from the track relay, while there is means governed by these detector relays for controlling a warning signal for the intersection. The value of the resistance connected around the insulated jointand the resistance of the windings of the detector relays are proportioned so that when a train enters a section, the detector relay nearest the train is shunted, but the resistance connected around the insulated joint prevents the shunting of the detector relay farthest from the train, and it continues to operate until the train passes the insulated joint. When a train clears the crossing, coded energy supplied from the end of the section at which the train entered the section is'supplied to the detector relays, and the detector relay which is farthest from the receding train will again follow code, and cause the crossing signal to cease operation. v v

In a modification of my invention, additional insulated joints having resistors connected around them are provided to permit the efiective length of the portion of the track circuit which controls the detector relays to be adjusted as de-. sired.

In the drawings Fig. 1 is a diagram of a section of railway track equipped with track circuit apparatus embodying my invention, and j Fig. 2 is a diagram showing a modification which I may employ.

Referring to Fig. 1 of the drawings there is shown therein a section of railway track having track rails l and 2 over which traflic normally moves in a direction indicated by the arrow, that is, from left to right. The rails of the track section are separated from the rails of the adjoining track section by insulated joints 3.

An intersection of the track section with a highway H, divides the track section into two portions, the first portion extending from the I and 2 is governed by the coding relay CR which i may be governed in any manner well known in the art by trafiic conditions in the adjacent section in advance. In a typical system the relay CR may be operated to supply energy of '75 code frequency to the section rails if the adjacent section in advance is occupied by a train and to supply energy of 180 code frequency to the section rails if the adjacent section in advance is vacant.

At each of the locations D, F, and H, there is provided a source of direct current, not shown, the positive and negative terminals of which are designated by the reference characters B and C, respectively.

An insulated joint 5 is located in one of th track rails at a point near the center of the highway crossing. A resistor I has one of its terminals connected to the section rail I on the side of the insulated joint 5 adjacent the track battery TB, and has its other terminal connected to section rail I on the side of insulated joint 5 adjacent the track relay TR. The code following detector relay EAR has its winding connected across the section rails I and 2 on the side of insulated joint 5 nearest the track relay, and the code following detector relay WAR has its winding connected across the section rails I and 2 on the side of insulated joint 5 nearest the track battery. The code following operation of the detector relays EAR and WAR is detected by means of the condensers EQ and WQ and the slow release code detecting relays ECDR and WCDR, respectively. The code detecting relays ECDR and WCDR control the circuits of the interlocking relay XR which governs the crossing signal XS, which is here shown as a bell, but it is to be understood that any suitable type of warning device may be used.

The interlocking relay XR may be any suitable type, one well-known form of which is described indetail in Letters Patent of the United States, No. 1,799,629, granted to William K. Lockhart and Thomas J. OMeara, on April 7, 1931, for Interlocking Relay.

For a clear understanding of my present invention, it is sufficient to point out that if the windings of the relay become deenergized in succession, the interlocking mechanism will operate to prevent the armature associated with the winding last to become deenergized from dropping sufliciently far to close its back contacts, even though the armature controlled by the winding firstto become deenergized subsequently picks up.

The track relay TR is of the polar biased type the contact of which picks up when and only when energy flows through the relay winding in a particular direction, while the track relay is .connected in the track circuit so that its contact picks up when energy flows through the relay winding from left to right.

When contact II! of relay CR connects the track battery TB across the section rails energy 'battery. In addition,. energy flows from the positive terminal of the battery over rail I through resistor I, through the winding of relay EAR to rail 2 and thus to the negative terminal of. the battery. Energy also flows from the positive terminal of the battery TB over the portion of track rail I at the right of joint 5, through the resistor I, over the portion of track rail I at the left of joint 5, through the winding of relay TR from left to right, over back contact I2 of relay IR to rail 2 and thence to the negative terminal of the battery. Accordingly, during the closed periods of the contact of relay CR the contacts of relay WAR, EAR, and TR are picked up by energy supplied from the battery TB.

On movement of the contact I0 of relay CR to its released position, the supply of energy from the track battery TB to the section rails is cut off, and relays TR, WAR, and EAR release. Accordingly, as long as the section is vacant the track relay TR and the code following detector relays EAR and WAR are operated by the master code energy supplied over the section rails.

As a result of the code following operation of the track relay TR, energy is supplied to windings of relays FSA and BSA, which are arranged in a manner well known in the art to detect the code following operation of track relay TR. Contact I4 of relay BSA may be employed in any well known manner to control the signal governing movements into the track section and to control the supply of coded energy to the rails of the adjacent section in the rear.

During the time that contact I6 of relay WAR is released, energy is supplied to the condenser WQ by the circuit which is traced from terminal B, over back contact I6 of relay WAR to the lefthand element of condenser WQ, the right-hand element of the condenser being connected to terminal C. Each time that contact I 6 of relay WAR picks up in response to an impulse of master code energy, the circuit is established for supplying energy from the condenser WQ to the winding of the slow release relay WCDR. This circuit may be traced from the left-hand element of condenser WQ, over contact I6 of relay WAR, and through the winding of relay WCDR toterminal C, and thus to the right-hand element of condenser WQ. The relay WCDR is of a type the contacts of which are slow to release and the relay is selected so that its contacts will remain picked up in the released :periods of relay WAR when relay WAR is operated by coded energy. Accordingly, it will be seen that the code following operation of contact I6 of relay WAR will cause the relay WCDR to pick up and remain picked up as long as relay WAR is following code.

Similarly, when contact I8 of relay EAR is released energy is supplied to the condenser EQ, and when contact I8' of relay EAR is picked up energy is supplied from the condenser through the winding of relay ECDR, so that as long as relay EAR is operated by coded energy, the contacts of relay ECDR will remain picked up.

At this time the winding 20 of relay XR is supplied with energy over the front contact 22 of relay ECDR and the winding 24 of relay XR is supplied with energy over a front contact 26 of relay WCDR. As both windings of relay XR are energized the supply of energy to the crossing signal XS is interrupted and this signal is not operated.

Accordingly, when the section DH is unoccupied relays TR, EAR, and WAR are operated by the master code impulses supplied from the battery TB. When track relay TR follows code the relays FSA and BSA are picked up, and when relays EAR and WAR follow code they-cause the associated decoding relays ECDR and WCDR to remain picked up, thereby energizing the winding'sjof interlocking relay XR to keep the crossing signal XS from operating at this time.

When a train moving in the normal direction of trafiic enters the track section DH the track relayTR is shunted and remains released; In addition, the shunting effect of the wheels and axles of the vehicles forming the train diverts so much energy from the relay EAR that it ceases torespond 'to energy supplied from the track battery TB;

After the train enters the rearward portion DF of the track section, the rails of the forward portion F-H of the track section are shunted over the circuit which is traced from the portion of rail I in advance of joint through resistance 1 to the'portion of rail I in the rear of 'joint'i, and through the wheels and axles of the vehicles of the train to rail 2. The presence of resistor I in this circuit limits the effectiveness of the shunt in di erting energy from the winding of relay WAR and the various parts of the equipment are arranged and proportioned so that at this time sufiicient energy continues to be supplied from battery TB to the winding of relay.WAR to operate the relay contact.

When relay TR ceases to follow coded energy the relays vFSA and BSA release. When relay FSA releases, a. circuit is established to supply energyto the impulse relay IR. This circuit is traced from terminalB, over back contact '30 of relay TR, over back contact 32 of relay FSA, over front contact 34 of a continuously operating coding, device CT, through resistor 36, to the lefthand element of condenser IQ, and from the right-hand-element of the condenser through the windingof relay IR to terminal C of the source. Duringthe charging of the condenser IQ current flows through the winding of relay IR causing the contact I2 of relay IR to be picked up for a short interval. After the voltage of condenser IQ has reached the voltage of the source, current stops flowing in the circuit of the contact I2 ofrelay IR releases and reestablishes the circuit for connecting the relay TR across the section rails. When contact 34 of coding device CT moves it'its released position, it establishes an obvious'circuit for short-circuiting the condenser IQ through the resistor 36 so that the condenser IQ will be discharged when contact 34 of coding device CT again moves to its picked-up position. It will beapparent that each time contact 34 of coding device CT picks up there is a momentary rushof current through the winding of relay IR to cause this relayto pick up for a very short time and thereafter release. Each time that contact l2 of relay IR picks up a circuit is established to supply energy from the battery IE to the rails of section DH. However, at this time, because of the presence of a train in the track section the energy supplied from the battery IE to the section rails is prevented from reaching relays EAR and WAR so that relay EAR remains released and relay WAR continues to be operated by energy supplied from battery TB.

As'relay EAR remains released after entrance of'tlie train'into the section, contact I8 of relay EAR does not establish the circuit for supplying energyfrom condenser EQ to relay ECDR and aftera short time interval contact 22 of relay ECDR releases, interrupting the supply of energy to winding 20 of the interlocking relay XR. When contact 40 of relay XR releases, it establish'esa circuit which supplies energy from the source to the crossing signal XS, which then operates' to Warn the users of the highway of the approach of a train.

At this time, as explained above, the relay WAR'continues to operate so relay WCDR remains picked up and maintains the supply of energy to the winding 24 of interlocking relay XR.

When the train advances beyond the insulated joint 5 the resistance 1 iseliminated from the circuit over which the winding of relay WAR is shunted by the train so the energy supplied to the'relay winding is reduced below the value effective to operate the-relay. Accordingly, its contact remains released so that relay WCDR releases and interrupts the circuit of winding 24 of relay XR, but because of the internal construction of the relay the contact 42 is prevented from moving all of the way to its released position.

When the train advances far enough in the track section for the rear of the train to be located in advance of the insulated joint 5 the re sistance l is included in the circuit by which the train shunts relay EAR with respect to energy supplied from battery 13 so the energy supplied from the battery 1B is eiiective to operate the relay EAR. At this time the winding of relay WAR is directly shunted by'the train so relay WAR will not respond to energy supplied from battery 1B.

When relay EAR responds to energy from battery 13 the relay ECDR becomespicked up and its contact 22 establishes the circuit for supplying energy to the winding 20 of relay XR that contact 40 of relay XR is picked up'and cutsoff the supply of energy to the crossing signal XS.

As relay WAR remains released the relay WCDR also remains released and winding 24 'of relay XR remains deenergized.

As explained above the picked up periods of contact l2 of relay IR are relatively brief and are substantially shorter than the picked-up periods of contact 34 of the coding device CT. As the picked up periods of contact l2 are relatively brief, the released periods of the relay contact are relatively long so the periods during which the track relay TR is connected across the track rails are relatively long. Accordingly, when the track section is vacated there will promptly occur a time at which energy from battery TB will feed to the winding of relay TR and pick up the relay contact 30. If desired, the prompt picking up of the relay TR may be further assured by having the code transmitter CT operate at a rate different from the rates at which the relay CR operates. As soon as contact 30 of relay TR picks up it interrupts the circuit governed by the code transmitter CT for supplying energy to the relay.

IR so that the relay IR is certain to remain released and maintain the circuit of the relay TR. When relay TR picks up energy is supplied to relay FSA and its contact 32 picks up to additionally interrupt the circuit for supplying energy to relay IR so that it will not be operated during subsequent released periods of relay TR. Relay BSA is also picked up by the recurrent operation of contact 3!! of relay TR and its contact I4 again establishes the signal control circuits or other circuits which may be controlled over that contact.

In addition, the master code energy once more operates the code following detector relays EAR and WAR so that the relay ECDR remains picked up and the relay WCDR becomes picked up with the result that energy is supplied to both of the windings 20 and 24 of relay XR and the equip- 10 ment is thus restored to its normal condition.

The arrangement shown in Fig. 1 also operates to provide the desired control of the crossing signal XS on movement of a train through the track section in reverse of. the normal direction.

When a train moving from right to left enters the track section DH, the supply of master code energy from the track battery over the section rails is cut off and relays WAR, EAR, and TR cease to operate so energy is no longer supplied to relays FSA, BSA, ECDR, and WCDR. On release of relay FSA, the circuit previously traced for supplying energy to the impulse relay IR is established, and relay IR is operated to supply energy from the battery IE to the rails of the section.

This energy operates relay EAR since the train is ineffective to shunt relay EAR through the resistance 1. Relay WAR is shunted by the wheels and axles of the approaching train and does not operate. The release time of the slow release relay ECDR is substantially longer than the release time of the relay FSA to insure that relay ECDR will remain picked up until after relay FSA releases and causes relay IR to be operated by the coding device CT. Accordingly, after the train enters the section and cuts off operation of relay EAR by energy from battery TB the relay ECDR remains picked up until energy is supplied thereto as a result of operation of relay EAR by energy from battery IB. As relay ECDR remains picked up it maintains the circuit of the winding 20 of relay XR and prevents release of contact 40 of relay XR.

-On release of contact 26 of relay WCDR the supply of energy to the winding 24 of the relay X8. is interrupted and contact 42 of relay XR releases so that energy is supplied to the crossing signal XS to thereby warn the users of the highway of the approach of a train.

When the train advances beyond insulated joint 5 the relay EAR is shunted and the supply of energy to relay ECDR is interrupted. When relay ECDR releases, the supply of energy to the winding 20 of relay XR is cut off, but because of the internal construction of the relay XR, contact 40 is prevented from moving to its released position since contact 42 is already released.

When the train advances far enough in the track section for the rear of the train to be located at the left of insulated joint 5, master code energy supplied to the rails of the section from battery TB will flow through the winding of relay WAR and cause it to operate so that relay WCDR will become picked up. When contact 26 of relay WCDR picks up, energy is supplied to the winding 24 of relay XR, so that contact 42 of relay XR picks up and interrupts the supply of energy to the crossing signal XS.

At this time the resistance of the train shunt is low enough to prevent the relay EAR from operating. Accordingly, relay ECDR remains released and interrupts the supply of energy to the winding 20 of relay-XR, while contact 40 continues to be prevented from moving to its fully released position.

When the train vacates the track section DH an impulse of master code energy operates the track relay TR during a released period of the contact of relay IR so that contact 30 of relay TR interrupts the circuit for supplyin energy to impulse relay IR. As a result, the contact 12 of relay IR remains released to continuously connect the track relay TR across the section rails. Additionally, when relay TR picks up energy is supplied to relays FSA and its contact picks up so that during subsequent operation of relay TR the relay BSA is supplied with energy and its contact l4 picks up to establish the circuits governed thereby.

In addition, at this time master code energy is supplied to the winding of relay EAR and operates the relay contact to cause the relay ECDR to become picked up and establish the circuit for supplying energy to the winding 20 of relay XR, while relay WAR continues to be operated by energy from battery TB so that relay WCDR remains energized and maintains the supply of energy to winding 24 of relay XR. Accordingly, the equip ment is now restored to its normal condition.

From the foregoing it will be seen that the apparatus shown in Fig. 1 operates to provide the desired control of the crossing signal on movement of a train through the track section in either direction.

In some situations it is desirable to start the operation of the crossing signal XS when the train reaches a point intermediate between the extreme limits of the coded track circuit and the highway intersection.

Where this is desired,

insulated joints

45 and 46 are mounted in track rail 1 at locations E and G, as shown in Fig. 2, at the points in the track section at which the operation of the crossing signal is to be initiated. Resistors 48 and 50 are bridged around the

insulated joints

45 and 46 and are of such value as not to reduce the energy supplied to the winding of relay TR from battery TB below the value necessary to operate the relay.

When a train moving from left to right'enters the section the relay TR is shunted and remains released. However, the resistor 48 limits the shunting eifect of the train on the relay EAR so that sufiicient energy continues to be supplied from battery TB to the relay EAR to operate the relay so it prevents operation of the crossing signal. When the train advances beyond location E the resistor 48 no longer limits the shunting effect of the train on relay EAR and this relay ceases to respond to energy supplied from battery TB so that operation of the CIOSSll'lg signal XS is initiated as explained above. On continued movement of the train through the section and out of the section the equipment operates substantially as described above and a detailed explanation of the operation of the equipment at such times is unnecessary. v

When a train moving in the reverse of the normal direction, that is from right to left, enters the track section it cuts off the supply of energy from the track battery TB to the relays TR, EAR, and WAR. At this time the equipment at the lefthand end of the section causes impulses of energy to be supplied from the battery IE to the section rails and these impulses operate relays EAR and WAR to maintainthe associated code detectingrelays energized and thereby prevents operation of the crossing signal XS. The train is inefiective to shunt the relay WAR with respect to energy supplied from battery IB since the resistor 50 limits the effectiveness of the train shunt on the relay WAR. When the train advances beyond the insulated joint 46 the resistor 50 ceases to restrict the effectiveness of the train shunt and the energy supplied to the winding of relay WAR is reduced below the value necessary to operate the relay so its contact remains released and operation of the crossing signal is initiated. On continued movement of the train through the section and out of the section the equipment operates substantially as described above and a detailedexplanation of the-operation of the equipment at such times is unnecessary.

Although I have illustrated-and described only two forms of coded track circuit apparatus embodying my invention, it is to be understood that various changes and-modifications may be made therein'with the scope of the appendedcclaims without departing from the spirit and scopeof my invention.

.Having thus described my invention what I claim is:

1. In a coded railway signaling system, in

combination, a section of railway track through I which traflic normallymoves in a given direction, said track section including at an intermediate point in the sectionan intersection with a highway, a crossing signal at said intersection, a

coding device at the exit end of said section havinga contact continuously actuated to recurrently connect a firstsource of energy across the section rails, a code following track relay attheentrance end of said track section operated by energy supplied over the section rails from said first source, means associated with said track relay for at times connecting a second source of energy across the track rails when said track relay remains inoperative for a substantialtime interval and for effectively preventing operation of said track relay during said times, an insulated joint in one of said track rails and located adjacent said intersection, a resistor connected in series with said one of the track rails of said section at said intersection and bridging said insulatedjoint, a first detector relay connected across the track rails on the side of the resistornearest said track relay, a second detector relay connected across the track rails on the side of said resistor farthest from said track relay, said resistor and said detector relays being proportioned so that either of said relays maybe shunted without affecting the other, and means governed by saidfirst and second detector relays for controlling said crossing signal.

2. In a coded railway signaling system, in combination, a section of railway track through which trafiic normally moves in a given direction, said track section including at an intermediate point'in the section an intersection with a highway, a crossing signal at said intersection, a coding device at the exit end of said section having a contact continuously actuated to recurrently connect a first source of energy across the section rails, a code following track r'elayat the entrance end of said track section operated by energy supplied-over the section rails from said first source, means associated with said track section, including at an intermediate point in the section an intersection with a highway, a crossing signal at said intersection, a coding-device at the exit end of said section having a contact continuously actuated to recurrently connect a first source of energy across the section rails, a code following track relay at the entrance end of said track section operated by energy supplied over the section rails from said first source, means associated with said track relay for recurrently connecting a second source of energy across the track rails and for effectively preventing operation of said track relay during said intervals, said means beingefiective only when said track relay remains inoperative for a substantial time interval, an insulated joint located in one track rail of said section at said intersection to thereby subdivide said section into a first subsection extending from the exit end of said section to the intersection and a second subsection extending from the intersection to the entrance end of said section, a first detector relay consaid track relay for recurrently connecting a mains inoperative for a substantial time interval, an insulated joint in one of said track rails adjacent said intersection, a resistor connected in series with said one of the track rails of said section at said intersection and bridging said insulated joint, a first detector relay connected across the rails on the side of said resistor nearest the track relay, a second detector relay.

connected across the track rails on the side of said resistor farthest from the track relay, said resistor and said detector relays being proportioned so that'surficientenergy to operate one ofsaid relays is received from the source nearest nectedacross the track rails of said first subsection at said intersection, a second detector relay connected across the rails of said second subsection at said intersection, means governed by said first and second detector relays for controlling said crossing signal, a resistor for connecting the portions of said one track rail around said insulated joint, said resistor and said detector relays being proportioned so that when a train occupies said first subsection said first detector relay will be shunted and said second detector relay will be operated by energy supplied over the section rails from said second source-and so that when a train occupies said second subsection said second detector relay-will be shunted and said first detector relay will be operatedby energy supplied over section rails from said first source.

4. In a coded railway signaling system, in combination, a section of railway track through which trafiic normally moves in a given direction, said track section including at an intermediate point in the section an intersection with a highway, a crossing signal at said intersection, a coding device at the exit end of said section having a contact continuously actuated to recurrently connect a first source of energyacross the section rails, a code following track relay at the entrance end ofsaid tracksection operated by energy supplied over the section rails from said first source, means associated with said track relay for recurrently connecting a second source of energy across the track rails and for effectively preventing operation of said track relay during said intervals, said means being effective only when said track relay remains inoperative for a substantial time interval, a first insulated joint in one track rail located at said intersection, a second insulated joint in one track rail located between said intersection and the exit end of said section, a third insulated joint in one track rail located between said intersection and the entrance end of said section, a first detector relay connected across the rails of said section on the side of said first insulated joint nearest the exit end of; said section, a seconddetector relay connected across the rails of said section on the side of said first insulated joint farthest from the exit end of said section, means governed by said first and second detector relays for controlling said crossing signal, resistors connected around each of said insulated joints, said resistors and said detector relays being proportioned so that sufiicient energy to operate one of said detector relays is received from the source of energy nearest that relay when the other of said relays is shunted and so that sufiicient energy to operate will be received by both relays when the track section is shunted beyond said second or said third insulated joint.

5. In combination, a section of railway track including at an intermediate point in the section an intersection with a highway, an insulated joint in one of the track rails and located adjacent said intersection, a resistor connected in series with one of the rails of said section bridging said insulated joint, a coding device at one end of said section having a contact recurrently operated to connect a first source of current across the section rails, a code following track relay at the other end of said section and operated by energy supplied from said first source over the section rails and through said resistor, means effective while said track relay is not responding to coded energy to recurrently connect a second source of current across the section rails at the track relay end therof, an auxiliary code following relay located adjacent said intersection and having its winding connected across the section rails on the side of said resistor nearest said track relay, said resistor and the associated elements of the track circuit being arranged and proportioned so that occupancy of at least a selected portion of said track section on the track relay side of said resistor will prevent operation of said auxiliary code following relay by energy from said first source and so that occupancy of any portion of the track section on the side of said resistor farthest from said track relay will not prevent operation of said auxiliary code following relay by energy from said second source, code detecting means responsive to said auxiliary code following relay, and a crossing signal for said intersection governed by said code detecting means.

6. In combination, a section of railway track including at an intermediate point in the section an intersection with a highway, an insulated joint in one of the track rails and adjacent said intersection, a resistor connected around said joint, a coding device at one end of said section having acontact recurrently operated to connect a first source of current across the section rails, a code following track relay at the other end of said section operated by energy supplied from said first source over the section rails, means effective while said track relay is not responding to coded energy to recurrently connect a second source of current across the section rails at the track relay end thereof, an auxiliary code following relay connected across the rails of said track section adjacent said intersection, said insulated joint and said resistor being interposed between said auxiliary code following relay and said first source of current, code detecting means responsive to operation of said auxiliary code following relay, a crossing signal for said intersection governed by said code detecting means, the parts being arranged and proportioned for preventing operation of said auxiliary code following relay by energy supplied from said first source of current during occupancy of at least a selected portion of said section on'the track relay side of said intersection and for insuring operation of said auxiliary code following relay by energy supplied from said second source of current during occupancy of any portion of the track section on the side of said intersection farthest from said track relay.

7. In combination, a section of railway track including at an intermediate point in the section an intersection with a highway, a code followin track relay connected across the section rails at the first end of said section, an auxiliary code following relay connected across the section rails adjacent said intersection, means for recurrently connecting a first source of current across the section rails at the second end thereof to thereby.

energize the windings of said code followin relays in multiple, means effective while said track relay is not responding to coded energy to recurrently connect a second source of current across the section rails at the first end thereof, a crossing signal for said intersection governed by means responsive to code following operation of said auxiliary code following relay, an insulated joint in one of the track rails of said section and located adjacent said intersection and a resistor connected around said insulated joint and located between said auxiliary code following relay and said first source of current, the parts being proportioned and arranged for preventing operation of said auxiliary code following relay by energy supplied from said first source of current durin occupancy of at least a selected portion of the track section on the track relay side of said intersection and for insuring operation of said auxiliary code following relay by energy supplied from said second source of current during occupancy of the portion of said section on the side of said intersection farthest from said track relay.

8. In combination, a section of railway track including at an intermediate point in the sec tion an intersection with a highway, a code fol-' lowing track relay connected across the section rails at the first end of said second, a first auxiliary code following relay connected across the rails of said section adjacent said intersection, a

second auxiliary code following relay located adjacent said intersection and connected across the rails of said section on the side of said first auxiliary relay farthest from said track relay, means for recurrently connecting a first source of current across the section rails at the second end thereof to thereby energize the windings of said code following relays in multiple, means effective while said. track relay is not responding to coded energy to recurrently connect a second source of current across the section rails at the first end thereof, a crossing signal for said intersection governed by means responsive to code following operation of said first and second auxiliary code following relays, an insulated joint located in one track rail of said track section intermediate the point of connection of said first and second auxiliary code following relays with the section rails, a resistor connected around said insulated joint, said resistor and the asso' ciated track circuit elements being arranged'and proportioned to prevent operation of either of said auxiliary code following relays by energysupplied through said resistor during occupancy of at least a selected portion of the track section on the side of the resistor on which the relay is connected with the section rails and to insure operation of either of said auxiliary code follow' ing relays by energy supplied from the source on which the relay is connected with the section rails.

9. In combination, a section of railway track having at one end means for recurrently connecting a first source of current across the section rails and having at the other end a code following track relay operated by coded energy supplied over the section rails from said first source, and means for detecting occupancy of a predetermined portion of said track section intermediate the ends of said section, said means comprising a first resistor connected in series with a track rail of said section across a first insulated joint at one end of said predetermined portion, a second resistor connected in series with a track rail of said section across a second insulated joint at the other end of said predetermined portion, an auxiliary code following relay connected across the rails of said track section within said predetermined portion and adjacent one end thereof, means effective while said track relay is not responding to coded energy to recurrently connect a second source of current across the track rails at the track relay end of said section, and code detecting means responsive to code following operation of said auxiliary code following relay, said resistors and the associated track circuit elements being arranged and proportioned so that during occupancy of the portion of said track section on either side of said predetermined portion said auxiliary code following relay will respond to energy sup- 7 plied over the section rails from the source on the opposite side of said predetermined portion and so that during occupancy of said predetersupplied over the section rails from said first source, and means for selectively detecting occupancy of two adjoining predetermined portions of said track section intermediate the ends of said section, said means comprising a resistor auxiliary code following relay connected across the track rails adjacent one end of said portion, each of said auxiliary code following relays having associated therewith code detecting means responsive to code following operation thereof, and means effective while said track relay is not responding to coded energy to recurrently connect a second source of current across the track rails at the track relay end of said section, said resistors and the associated track circuit elements being arranged and proportioned so that each of said auxiliary code following relays will respond to energy supplied over the section rails from one end of the section or the other as long as the predetermined portion with which said relay is associated is not occupied, and control means governed by said code detecting means whereby the occupancy of said predetermined portions is indicated.

11. In combination, a section of railway track having at one end means for recurrently connecting a first source of current across the section rails and having at the other end a code following track relay operated by coded energy supplied over the section rails from said first source, and means for detecting occupancy of a predetermined portion of'said track section, said means comprising a resistor connected in series with a track rail of said section across an insulated joint located at one end of said predetermined portion, an auxiliary code following relay connected across the rails of said section on the side of said resistor remote from said first source of current, means effective while said track relay is not responding to coded energy to recurrently connect a second source of current across the track, rails at the track relay end of said section, and code detecting means responsive to code following operation of said auxiliary code following relay, said resistor and the associated track circuit elements being arranged and proportioned so that occupancy of at least a selected portion of said track section on the track relay side of said resistor will prevent operation supplied from said first source of current and so that occupancyv of any portion of the track section on the side of said resistor farthest from said track relay will not prevent operation of said auxiliary code following relay by energy from said second source, said code detecting means governing circuits for indicating occupancy of said predetermined portion.

HERMAN G. BLOSSER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,106,680 Reichard Jan. 25, 1938 2,362,156 Preston Nov. 7, 1944 2,376,967 Jerome May 29, 1945 2,409,044 Jerome Oct. 8, 1946