US2277459A

US2277459A - Railway signaling system

Info

Publication number: US2277459A
Application number: US353354A
Authority: US
Inventors: Warren W Seitz
Original assignee: Union Switch and Signal Inc
Current assignee: Hitachi Rail STS USA Inc
Priority date: 1940-08-20
Filing date: 1940-08-20
Publication date: 1942-03-24
Anticipated expiration: 1959-03-24

Description

w.'w. SEITZ RAILWAY SIGNALING SYSTEM Filed Aug. 20, 1940 March 24,

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HIS ATTORNEY March 24, 1942. w. w. SEITZ RAILWAY SIGNALiNG SYSTEM 3 Sheets-Sheet 2 H15" ATTORNEY Filed Aug. 20, 1940 Patented Mar. 24, 1942 RAILWAY SIGNALING SYSTEM Warren W. Seitz, Wilkinsburg, Pa., assignor to The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application August 20, 1940, Serial No. 353,354

15 Claims.

My invention relates to a coded railway signaling system and particularly to an improvement in the system shown in application Serial No. 330,122 of Howard A. Thompson, filed April 17, 1940, for Railway signaling system.

In the system shown in the application identified above each track section is divided into two subsections and the control of the signals is overlapped in such manner that there is always at least one unoccupied subsection in advance of the point in the track stretch at which a train receives the most restrictive indication. Because of this arrangement, the system is especially well suited for use in track stretches which are without wayside signals and employ cab signals only, although the system is not limited to use in such installations.

In the system shown in that application coded alternating current energy is supplied substantially continuously to the varius track sections and is employed to actuate both the track relays and the cab signal apparatus o-n locomotives traversing the track stretch. This arrangement is satisfactory where alternating current energy is available from a commercial source of current. However, where the alternating current energy supplied to the track circuits is derived from tuned reed alternators or equivalent devices, it is preferable to employ coded direct current to operate the track relays and to arrange the circuit so that coded alternating current to actuate the locomotive cab signal apparatus is supplied to each track section only when a train is present in that section. This reduces the period of operation of the alternators and correspondingly increases their life, while it reduces the I current consumed thereby.

It is an object of this invention to provide an improved signaling system of the type described employing coded direct current to operate the track relays, and having approach controlled alternating current supply devices for supplying coded alternating current cab signal control energy to the various track sections.

A further object of the invention is to provide an improved signaling system of the type described and which is arranged so that there is always at least one track section in the rear of an occupied section to which no coded alternating current cab signal control energy is supplied to thereby insure that the cab signal equipment on a locomotive traversing the track stretch will operate to provide its most restrictive indication before the locomotive enters the oocupied section and thus warn the engineman that he is approaching an occupied section.

Another object of the invention is to provide an improved coded railway signaling system.

Other objects of the invention and features of novelty will be apparent from thefollowing description taken in connection with the accompanying drawings.

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

In the drawings Figs. 1A and 1B when placed together form a diagram of a stretch of railway track equipped with signaling apparatus embodying my invention, and

Fig. 2 is a diagram showing the types of energy supplied to the various track sections in a track stretch under different conditions of track occupancy.

Referring to Figs. 1A and 1B there is shown therein a stretch of railway track having track rails I and 2 over which traffic normally moves in the direction indicated by the arrow, that is, from left to right.

The rails of the track stretch have insulated joints 3 therein to divide the track stretch into block sections, while the rails ofeach block section are further divided by insulated joints into three subdivisions or track sections. There is shown in the drawings one complete block section and portions of the equipment for the adjoining sections in advance and in the rear.

The block section shown in Fig. 1 of the drawings includes track sections AMT, BMT and GMT, while the track section of the adjacent block section in advance is designated Al5T, and the track section of the adjacent block section in the rear is designated CI3T.

The system shownin this application is of the three indication variety and. employs coded direct current track circuit energy of two code frequencies which may consist of and energy impulses per minute which are separated by periods of equal duration in which no energy is supplied. These code impulses may be provided by code transmitters CT having contacts '75 and 180 which are continuously actuated by a motor or other means.

In the system provided by this invention the these track relays serve, at times, to supply steady uncoded direct current energy to the adjacent sections in the rear.

The system provided by this invention employs coded alternating current of a suitable frequency, such as 100 cycles per second, in the track circuits to actuate cab signal equipment on the locomotives traversing the track stretch. The alternating current employed in the system is provided by tuned reed alternators, while these alternators are normally idle and are approach controlled so as to operate only when a train is present in th section to which current is supplied from the device. The alternators are also controlled by traffic conditions in advance so as to be prevented from operating when the adjacent section in advance is occupied, or in some instances when the second section in advance is occupied.

In order to effect the desired approach control of the tuned alternators the system provided by this invention makes use of the coded approach control equipment shown in United States Patent No. 2,174,255, issued September 26, 1939, to H. G. Blosser. The details of construction and operation of this part of the system are not a part of this invention. Similarly, the invention is not limited to use with this approach control means and any form of approach control equipment well known in the art may be employed to perform this function.

Each of the track relays has associated therewith a source of direct current, such as a storage battery, not shown, the terminals of which are designated B and C.

The locomotives which are operated in the territory equipped with the signaling system provided by this invention are equipped with cab signaling apparatus responsive to the presence of coded alternating current in the track rails. The cab signaling equipment is shown diagrammatically in the drawings and may be of any construction well known in the art. One system which may be employed is shown in United States Patent No. 1,986,679, issued January 1, 1935, to L. V. Lewis. The cab signal apparatus responds to alternating current energy of 180 code frequency to provide a green or clear indication, while it responds to alternating current energy of '75 code frequency to provide a yellow or caution indication. In addition, the cab signal apparatus operates when no coded alternating current energy is present to provide its red or most restrictive indication. This may be considered a stop indication or it may be regarded as a slow speed indication.

The equipment is shown in the condition which it assumes when a train is present in section CI3T and when the track stretch is otherwise vacant. At this time direct current energy of 180 code frequency is supplied to the rails of section AIET and as the track relay AE5TR is responding to coded energy, current is supplied through the decoding transformer AIEDT to the relay AIEH. As relay AlEH is picked up its contact 22 establishes the circuit including contact I80 of code transmitter AIECT for energizing the coding relay AIECR. The relay AIBCR, therefore, operates to supply master code energy of 180 code frequency from the track battery CI4TB to the rails of section CMT, While during the "013? periods in the master code "feed back energy is supplied from the section rails to the detector relay CMKR.

The track relay CMTR repeats the supply of master code energy to the rails of section BEAT,

while the relay BMTR in turn repeats the supply of master code energy to the rails of section AMT. As each track relay is responding to coded energy the impulse relay IR associated with that track relay operates to supply feed back energy from a battery AB during the off" intervals in the master code to the detector relay at the exit end of the section. As the detector relays for sections AMT, BMT and CMT are supplied with feed back energy the associated approach relays AR are energized and maintain the tuned alternators TA for these sections inactive.

As track relay AMTR is responding to coded energy relay AMH is picked up and energy of 180 code frequency is supplied to the coding relay Al iCR. so that master code energy of 180 code frequency is supplied to section CI3T. Since the track section Cl3T is assumed to be occupied feed back energy is not supplied to the detector relay Cl iKR and the approach relay CHAR is released and establishes the circuits of the operating winding of the alternator CMTA and of the primary winding of the associated transformer so that energy is induced in the transformer secondary winding. The secondary winding of this transformer is included in series with the circuit controlled by the coding relay AHiCR. for supplying direct current master code energy from the battery CI3TB to the rails of section Ci3T so alternating current energy of 180 code frequency is supplied to the rails of section CI3T.

The alternating current energy of code frequency supplied to the rails of section CiST causes the locomotive cab signal apparatus to display its green or clear indication.

If the train in section 013T advances into section AMT it will shunt the track relay Al 4TR and cut off the supply of feed back energy to the detector relay Al 4K1... and this relay will no longer establish the circuit of approach relay AMAR. Accordingly relay AMAR will release and supply energy to the alternator AMTA so .that coded alternating current will be supplied to the rails of section AMT to operate the locomotive cab signal apparatus and this equipment will continue to operate to provide its green or clear indication.

As the train continues through the track stretch, as it enters each successive track section the approach relay for that section becomes released and effects operation of the tuned alternator which it controls so that alternating current is supplied to operate the locomotive cab. signal apparatus.

When the train under consideration enters section AMT and shunts the track relay Ai iTR, relay AMI-I releases and its contact 2i interrupts the supply of ener y to the alternator CMTR and this device ceases to operate. In addition, on release of relay AMI-I contact 2?. interrupts the circuit of the contact and establishes the circuit including the 75 code contact of code transmitter AMCT for energizing the coding relay AMCR. Accordingly the coding relay AMCR operates to supply master code energy of 75 code frequency to the rails of section ClST, while when the train vacates section ClST feed back energy is supplied over the section rails to the detector relay CiBKR and this relay establishes the circuit of the approach relay CiBAR.

If whilethe first train is present in section Al tT a second or following train should enter section CH3)? the supply of feed back energy to the detector relay CISKR will be out off and the approach relay CI3AR will become released. However, release of the approach relay OMAR at this time will not effect operation of the alternator CI3TA as the circuit of this device is interrupted by contact 2! of relay AMI-I. Accordingly, no alternating current is supplied to the rails of section 013T and the cab signal equipment on the locomotive of the second or following train will function to provide its red or stop indication, that is, its most restrictive indication.

When the first train advances into section BMT the track relay BMTR is shunted and relay BMH releases and its contact 2| cuts ofi operation of the alternator AMTA. In addition, on release of relay B I 4H its contact 24 establishes a circuit to supply steady uncoded energy from the track battery AMTB to the rails of section AMT. Another circuit for supplying steady uncoded energy to the rails of section AMT is established at this time by back contacts 38 and 3! of the track relay BMTR.

In addition, on release of relay BMH contact 25 interrupts the circuit of the pick-up winding of the detector relay AMKR, to thereby prevent energy supplied to the rails of section BMH feeding to the relay AMKR and picking up the contacts of this relay.

When the first train vacates section AMT the steady energy supplied to the rails of section AMT picks up the track relay AMTR and also picks up the auxiliary track relay AM'IRA. The auxiliary track relay AMTRA is connected in multiple with the track relay Al iTR, at this time as contact 21 of relay Ai iH is released, while relay Al lH is released since energy is not supplied thereto through the decoding transformer AMDT when the track relay AMTR is steadily picked up.

When contact 28 of relay Al l-TRA is picked up and contact 2| of relay AMH is released a circuit is established to permit energy to be supplied to the alternator Cl3TA if a train enters section C'I3T and releases the approach relay Ci3AR. Accordingly, if while the first train is present in section BMT, but has vacated section AMT, a second or following train should enter section Ci3T, the alternator CE3TA will operate so that alternating current energy will be supplied to the rails of section 013T, while this energy will be coded at the 75 code frequency so that the locomotive cab signal apparatus will provide its yellow or caution indication.

When the first train advances into section CMT the track relay Cl lTR. is shunted and relay CMI-I releases. When relay CMTR is shunted the

contacts

30 and 3! establish a circuit to supply steady uncoded energy from the track battery CMTB to the rails of section BMT, and when the train vacates section BMT this energy feeds to the track relay BMTR and picks up its contacts. When relay BMTR picks up

contacts

30 and 31 interrupt the circuit which they established for supplying steady energy to the rails of section AMT. However, at this time the relay BMH remains released and its contact 24 maintains the circuit for supplying steady energy to the rails of section AMT so the auxiliary track relay AMTRA continues to be picked up and maintains the circuit for supplying energy to the alternator Ci3TA on release of the approach relay C WAR.

On picking up of the contacts of track relay BMTR steady energy supplied to the rails of section AMT does not energize the detector relay AMKR since at this time the circuit of the pick-up winding of this relay is interrupted by contact 25 of relay BMH. Relay AMKR, therefore, remains released and relay AMAR is also released.

Accordingly, if while section CMT is occupied and sections BMT and AMT are vacant a second or following train should enter section C|3T the alternator CI3TA will operate and alternating current energy of 75 code frequency will. be supplied to the rails of section CI3T to cause the cab signal equipment to display its yellow or caution indication.

However, if while either section BMT or CMT is occupied a second or following train should advance into section AMT, no alternating current would be supplied to the section rails since the circuit of the alternator AMTA is interrupted by contact 2| of relay BMI-I and the 10- comotive cab signal apparatus will function to provide its most restrictive indication.

Similarly, if while section CMT is occupied a train should enter section EMT, no alternating current would be supplied to the section rails as the circuit of the alternator BMTA is interrupted by contact 2! of relay CMH and the 10- comotive cab signal equipment will function to provide its most restrictive indication.

When the train under consideration advances into. section AI5T the track relay AlfiTR is shunted and relay AEEH releases. On release of relay .AIEIH contact 22 changes the energy supplied to the coding relay AIECR from to '75 code frequency, while contact 2| interrupts thecircuit of the alternator C'MTA.

When the train vacates section CMT the master code energy supplied by the coding relay AiBCR feeds to the track relay CMTR and produces code following operation of this relay so that it relays the supply of master code energy of '75 code frequency to section BMT, while relay BMTR, similarly relays the supply of master code energy to section AMT.

On the supply of master code energy to the relay CMTR the impulse relay CMTR operates to supply feed back energy to the section rails, and this energy operates the detector relay CMKR. so that the approach relay CMAR picks up. In addition, when relay CMTR responds to coded energy the relay CMH picks up and its contact 2| establishes the circuit to permit energy to be supplied to the alternator Bl GTA when section BMT is occupied.

Similarly, on the supply of master code energy to section BMT, relay BMH is picked up, While feed back energy is supplied over the section rails and the approach relay BMAR. picks up. When relay DMH picks up contact 24 interrupts the circuit for supplying steady energy to section AMT and thereafter coded energy is supplied to section AMT over the circuits controlled by contacts 30 and SI of the track relay BMTR.

In addition, on picking up of relay BMH its contact 25 establishes the circuit of the pick-up winding of the detector relay AMKR so that this relay will respond to feed back energy supplied over the rails of section AMT.

When coded energy is supplied to the track rela AMTR, relay AMH picks up and interrupts the circuit of the auxiliary track relay AM'IRA, while contact 2| of the relay establishes a circuit to permit energy to be supplied to the alternator CISTA on release of the approach relay CHAR, and contact 22 changes the energy supplied to the coding relay AMCR from '75 to 180 code frequency. There is, therefore, a change in the frequency of the master code energy supplied to the block section 1ST and a train in this section will receive a clear cab signal instead of a yellow or caution signal.

Similarly, the master code energy supplied to block section MT continues to be of the 75 code frequency as long as a train is present in the block section in advance, but when the train vacates the block section in advance the master code energy supplied to block section MT is changed to 180 code frequency, while energy of 180 code frequency continues to be supplied to section I3T.

The operation of the equipment may be more clearly understood by reference to Fig. 2 which is a diagram showing the types of energy supplied to the various track sections in a track stretch under different conditions of occupancy. In this diagram alternating current is shown as being supplied to certain of the track sections, but it should be understood that the supply of alternating current is governed by the approach control apparatus, and that this current is supplied to a track section only when that section is occupied. The supply of alternating current to the various track sections is shown in the diagram to make clear the sections to which such energy is supplied, and those to which this energy is not supplied.

Referring to Fig. 2 it will be seen that when a train occupies th rearward track section in a block section direct current master code en ergy of the 75 code frequency is supplied to the track sections of the adjacent block section in the rear, while master code energy of 180 code frequency is supplied to the track sections of the second block section in the rear. It will be seen also that alternating current energy of the appropriate code frequenc is supplied to the various track sections except to the forward track section of the adjacent block section in the rear of the train. As a result when a train is present in section AIST a following train will receive a clear cab signal as long as it is in block section IZT, while the cab signal will change to caution when the train enters section MT. The caution indication will be maintained while the train is in either track section AMT or BMT, but as soon as the train enters track section CMT the cab signal indication changes from yellow or caution to red or stop. The system operates at this time, therefore, to provide a caution indication at a point one full block section in the rear of the occupied section, and to provide the red or stop indication at a point one full track section in the rear of the occupied section.

In addition, it will be seen from Fig. 2 that when a train is present in the intermediate track section of a block section, a following train receives a clear cab signal until it enters the adjacent block section in the rear of the occupied block section, and that the following train will receive a caution cab signal indication throughout the block section next in the rear of the occupied block. As soon, however, as the following train enters the occupied block it will receive a red or stop cab signal indication, and that this indication is given to the following train at a point one full track section in the rear of the occupied section.

If a train is present in the forward track section of a block section the following train will receive the stop cab signal indication at the entrance to the occupied block section, and this indication is given the following train two full track sections in the rear of the occupied track section.

As this system operates to give a following train a caution cab signal at least one block section in the rear of an occupied track section and to give the most restrictive cab signal indication at a point at least one track section in the rear of an occupied section, the engineer of the following train has ample warning of the fact that he is approaching an occupied section and he can stop his train before entering the occupied section.

In the system provided by this invention the alternating current energy employed to operate the cab signal equipment is provided by tuned reed alternators. Each of these alternators is approach controlled so as to operate only when the section to which it supplies energy is occupied. Each of these alternators is also controlled by traffic conditions in advance so that the alternator is maintained inoperative at times when alternating current is not required to be supplied to the track section.

It will be seen also that each approach relay when picked up not only interrupts the supply of energy to the associated alternator, but it also short circuits the primary winding of the transformer associated with the alternator. This reduces the impedance of the transformer secondary winding which is included in series with the circuit for supplying direct current master code energy to the section rails. As the impedance of this winding is at a minimum the winding offers the least resistance to flow of impulses of master code energy and the impulses of master code supplied to the section rails are of the maximum value, therefore, and insure positive operation of the track relay for the section.

When a track section is occupied and the approach relay is released the circuit shunting transformer primary winding is interrupted, but the impedance of the secondary winding and its effect on the impulses of master code energy is not objectionable at this time as the track relay is shunted.

The equipment at the control locations, that is, at the entrance to each block section, is arranged so that the primary winding of the alternator transformer is short circuited when the associated approach relay is released provided the associated code detecting relay and track relay are also released. This is the condition when a train enters the rearward track section in a block section, as for example, section ASST, and before the train vacates the adjacent section in the rear.

When a train is present in sections CMT and Al5T the relays OMAR, AIEiH and AlETRA are released and the primary winding of the transformer associated with the alternator CMTA is short circuited by a circuit which includes a back contact of the approach relay CHAR, back contact 21 of relay AiSH and back contact 28 of relay AI ETRA.

At this time direct current master code energy of code frequence is supplied to the rails of section Cl lT over the circuit which includes in series therewith the secondary winding of the alternator transformer. As the primary winding of this transformer is short circuited at this time the impulses of master code energy are of the maximum value, and when the train vacates section CMT these impulses of master code feed to the track relay i 1TB and cause it to follow code. As the master code impulses are of the maximum value they are certain to operate th track relay CM'I'R. As soon as the track relay CMTR responds to the master code, feed back energy is supplied over the rails of section CMT to the detector relay CMKR and the approach relay C MAR picks up and establishes another circuit to short circuit the primary winding of the alternator transformer.

Although I have herein shown and described only one form of railway signaling system 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 a railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a plurality of 7 track sections, the track section at the entrance end of each block section having means receiving energy over the rails of such section, said means being effective when deenergized to sup ply coded direct current of a first frequency to the rails of the adjacent track section in the rear and being effective when supplied with coded direct current of said first or a second frequency to supply coded direct current of said second frequency to the rails of the adjacent section in the rear, each track section except the track section at the entrance end of each block section having means operative on the supply of coded direct current thereto to supply coded direct current of the same code frequency to the rails of the adjacent track section in the rear, and means for each track section governed by trafiic conditions in such section and operative when and only when the section is occupied to supply to the rails of such section alternating current energy coded at the same code frequency as the direct current energy supplied to the said section.

2. In a railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a plurality of track sections, the track section at the entrance end of each block section having means receiving energy over the rails of such section, said means being effective when deenergized to supply coded direct current of a first frequency to the rails of the adjacent track section in the rear and being effective when supplied with coded direct current of said first or a second frequency to supply coded direct current of said second frequency to the rails of the adjacent section in the rear, each track section except the track section at the entrance end of each block section having means operative on the supply of coded direct current thereto to supply coded direct current of the same code frequency to the rails of the adjacent track section in the rear, and means for each track section for supplying to the rails of such section alternating current energy coded at the same code frequency as the direct current energy supplied to such section, the means for each track section being governed by trafiic conditions in that track section and also in the adjacent track section in advance and being operative to supply energy to the section when and only when the section is occupied and the adjacent section in advance is unoccupied.

3. In a railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a forward, an intermediate and a rearward track section, means governed by traflic conditions in each block section and in the adjacent block section in advance for supplying coded direct current energy of a first or a second code frequency to the rails of the forward track section of the adjacent block section in the rear, the forward and intermediate track section of each block section having means operative on the supply of coded direct current thereto to supply coded direct current of the same code frequency to the rails of the adjacent track section in the rear, and means for each track' section governed by trafiic conditions in such section and operative when and only when the section is occupied to supply to the rails of such section alternating current energy coded at the same code frequency as the direct current energy supplied to said section.

4. In a railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the'track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a forward, an intermediate and a rearward track section, means governed by traffic conditions in each block section and in the adjacent block section in advance for supplying coded direct current energy of a first or a second code frequency to the rails of the forward track section of the adjacent block section in the rear, the forward and intermediate track section of each block section having'means operative on the supply of coded direct current thereto to supply coded direct current of the same code frequency to the rails of the adjacent track section in the rear, and means for each track section for supplying to the rails of such section alternating current energy coded at the same code frequency as the direct current energy supplied to such section, the means for each track section being governed by traflic conditions in that track section and also in the adjacent track section in advance and being operative to supply energy to the section when and only when the section is occupied and the adjacent section in advance is unoccupied.

5. In a railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a forward, an intermediate and a rearward track section, means governed by traffic conditions in each block section and in the adjacent blocks section in advance for supplying coded direct current energy of a first or a second code frequency to the rails of the forward track section of the adjacent block section in the rear, the forward and intermediate track section of each block section having means operative on the supply of coded direct current thereto to supply coded direct current of the same code frequency to the rails of the adjacent track section in the rear, and means for each track section for supplying to the rails of such section alternating current energy coded at the same code frequency as the direct current energy supplied to such section, the alternating current supply means for each track section being governed by traffic conditions in the adjacent track section in advance and being incapable of supplying energy to the associated track section when the adjacent track section in advance is occupied.

6. In a railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a plurality of track sections, means governed by traffic conditions in each block section and in the adjacent block section in advance for supplying coded direct current energy of a first or a second code frequency to the rails of the forward track section of the adjacent block section in the rear, each track section except the track section at the entrance end of each block section having means operative on the supply of coded direct current thereto to supply coded direct current to the rails of the adjacent track section in the rear, and means for each track section for supplying to the rails of such section alternating cturent energy coded at the same code frequency as the direct current energy supplied to such section, the alternating current supply means for each track section being governed by trafiic conditions in the adjacent track section in advance and being incapable of supplying energy to the associated track section when the adjacent track section in advance is occupied.

'7. In a coded railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a forward, an intermediate and a rearward track section, each track section in the track stretch having at the entrance end thereof a code following track relay responsive to coded direct current and receiving i energy over the section rails, each track relay having associated therewith an auxiliary relay which is picked up when and only when said track relay is responding to coded energy, the auxiliary relay for the rearward track section in Cal each block section being operative when released to effect the supply of coded direct current of a first code frequency and when picked up to effect the supply of coded direct current of a second code frequency to the rails of the forward track section of the adjacent block section in the rear, the track relays of the forward and intermediate track section of each block section each being operative when responding to coded energy to supply coded direct current energy to the rails of the adjacent track section in the rear, each track section having at the exit end thereof alternating current supply means for supplying to the rails of such section alternating current energy coded at the same code frequency as the direct current energy supplied to the section rails, the alternating current supply means for each track section being governed by the auxiliary relay of the adjacent track section in advance and being operative to supply energy only when said auxiliary relay is picked up.

8. In a coded railway signaling system, in co1nbination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a forward, an intermediate and a rearward track section, each track section in the track stretch having at the entrance end thereof a code following track relay responsive to coded direct current and receiving energy over the section rails, each track relay having associated therewith an auxiliary relay which is picked up when and only when said track relay is responding to coded energy, the auxiliary relay for the rearward track section in each block section being operative when released to effect the supply of coded direct current of a first code frequency and when picked up to effect the supply of coded direct current of a second code frequency to the rails of the forward track section of the adjacent block section in the rear, the track relays of the forward and intermediate track section of each block section each being operative when responding to coded energy to supply coded direct current energy to the rails of the adjacent track section in the rear, each track section having at the exit end thereof alternating current supply means for supplying to the rails of such section alternating current energy coded at the same code frequency as the direct current energy supplied to the section rails, the alternating current supply means for each track section being controlled by the auxiliary relay of the adjacent track section in ad- Vance and also by trafiic conditions in the track section to which energy is supplied by said means and being operable to supply energy to such track section when and only when said auxiliary relay is picked up and the track section to which the energy is supplied is occupied.

9. In a coded railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a forward, an intermediate and a rearward track section, each track section in the track stretch having at the entrance end thereof a code following track relay responsive to coded direct current and receiving energy over the section rails, each track relay having associated therewith an auxiliary relay which is picked up when and only when said track relay is responding to coded energy, the auxiliary relay for the rearward track section in each block section being operative when released to effect the supply of coded direct current of a first code frequency and when picked up to effeet the supply of coded direct current of a second code frequency to the rails of the forward track section of the adjacent block section in the rear, the track relays of the forward and intermediate track section of each block section each being operative when responding to coded energy to supply coded direct current energy to the rails of the adjacent track section in the rear, each track section having at the exit end thereof an alternating current supply device operative on the supply of direct current thereto to supply to such track section alternating current energy coded at the same code frequency as the direct current energy which is supplied to said track section, the auxiliary relay for each tracksection controlling the supply of direct current to the supply device of the adjacent track section in the rear and being operative only when picked up to establish a circuit to permit direct current energy to be supplied to such supply device.

10. In a coded railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a forward, an intermediate and a rearward track section, each track section in the track stretch having at the entrance end thereof a code following track relay responsive to coded direct current and receiving energy over the section rails,

each track relay having associated therewith an auxiliary relay which is picked up when and only when said track relay is responding to coded en ergy, the auxiliary relay for the rearward track section in each block section being operative when released to effect the supply of coded direct current of a first code frequency and when picked up to effect the supply of coded direct current of a second code frequency to the rails of the forward track section of the adjacent block section in the rear, the track relays of the forward and intermediate track section of each block section each being operative when responding to coded energy to supply coded direct current energy to the rails of the adjacent track section in the rear, each track section having at the exit end thereof an alternating current supply device operative on the supply of direct current thereto to supply to such track section alternating current energy coded at the same code frequency as the direct current energy which is supplied to said track section, the circuit for supplying direct current to the supply device for each track section being governed by tramc conditions in such section and also by the auxiliary relay of the adjacent track section in advance and being complete when and only when said auxiliary relay is picked up and the track section to which energy is supplied by said device is occupied.

11. In a coded railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responding to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a forward, an intermediate and a rearward track section, each track section in the track stretch having at the entrance end thereof a code following track relay responsive to coded direct current and receiving energy over the section rails, each track relay having associated therewith an auxiliary relay which is picked up when and only when said track relay is responding to coded energy, the auxiliary relay for the rearward track section in each block section being operative when released to effect the supply of coded direct current of a first code frequency and when picked up to effect the supply of coded direct current of a second code frequency to the rails of the forward track section of the adjacent block section in the rear, the track relays of the forward and intermediate track section of each block section each being operative when responding to coded energy to supply coded direct current energy to the rails of the adjacent track section in the rear, the rearward track section in each block section each having a steady energy detecting track relay receiving energy over the section rails and being picked up when and only when steady uncoded direct current energy is supplied thereto, the auxiliary relay for the intermediate track section of each block section being operative when released to effect the supply of steady uncoded direct current to the rails of the rearward track section of such block section, each track section having at the exit end thereof alternating current supply means for supplying to the rails of such section alternating current energy coded at the same code frequency as the direct current energy supplied to the section rails, the alternating current supply means for the rearward and intermediate track section of each block section being governed by the auxiliary relay of the adjacent track section in advance and being operative to supply energy only when said auxiliary relay is picked up, the alternating current supply means for the forward track section of each block section being governed by the auxiliary relay and the steady energy detecting track relay of the adjacent track section in advance and being operative to supply energy only when said auxiliary relay or said steady energy detecting track relay is picked 12. In a coded railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the'rails of said track stretch being divided by insulated joints into a plurality of successive track sections including adjoining forward and rearward track sections, each of said track sections having at the entrance end thereof a code following track relay responsive to coded direct current and receiving energy over the section rails, the track relay for said forward section having associated therewith an auxiliary relay which is picked up when and only when said track relay is responding to coded energy, said auxiliary relay being operative when released to establish a first supply circuit to effect the supply of coded direct current energy of a first code frequency and when picked up to establish a second supply circuit to effect the supply of coded direct current energy of a second code frequency to the rails of said rearward section, a transformer having its secondary winding connected in series with said supply circuits, an approach relay which is energized when and only when said rearward section is vacant, means operative when said approach relay is released to energize the primary winding of said transformer and thereby effect the supply to the rails of the rearward section alternating current energy coded at the same code frequency as the direct current energy which is being supplied to the section rails, and means operative when said approach relay is picked up to short circuit the transformer primary winding to thereby reduce the impedance of the transformer secondary winding and correspondingly increase the value of the impulses of direct current energy supplied over said supply circuits.

13. In a coded railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into a plurality of successive track sections including adjoining forward and rearward track sections, each of said track sections having at the entrance end thereof a code following track relay responsive to coded direct current and receiving energy over the section rails, the track relayfor said forward section having associated therewith an auxiliary relay which is picked up when and only when said track relay is responding to coded energy, said auxiliary relay being operative when released to establish a first supply circuit to effeet the supply of coded direct current energy of a first code frequency and when picked up to establish a second supply circuit to effect the supply of coded direct current energy of a second code frequency to the rails of said rearward section, a transformer having its secondary winding connected in series with said supply circuits, an approach relay which is energized when and only when said rearward section is vacant, means operative when said approach relay is released and said auxiliary relay is picked up to energize the primary Winding of said transformer and thereby effect the supply to the rails of said rearward section alternating current energy coded at the same code frequency as the direct current energy which is being supplied to the rails of said section, and means operative when said approach relay is picked up or said auxiliary relay is released to short circuit the transformer primary winding to thereby reduce the impedance of the transformer secondary winding and correspondingly increase the value of the impulses of direct current energy supplied over said supply circuits.

14. In a railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signal-apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a plurality of track sections, each track sect-ion having at the entrance end thereof a direct current code following track relay receiving energy over the section rails, each track relay having associated therewith an auxiliary relay which is picked up when and only when the track relay is responding to coded energy, the auxiliary relay for the rearward track section in each block section being operative when released to effect the supply of coded direct current of a first frequency to the rails of the adjacent track section in the rear and when picked up to effect the supply of coded direct current of a second frequency to the rails of the adjacent track section in the rear, the track relays of each of the track sections except the track sections at the entrance ends of the block sections being effective when responding to coded direct current energy to supply coded direct current of the same frequency to the rails of the adjacent track section in the rear, each track section having at the exit end thereof means for supplying to the rails of such section alternating current energy coded at the same frequency as the direct current energy supplied to the rails of such section, the alternating current supply means for each track section being controlled by the auxiliary relay of the adjacent track section in advance so as to be effective to supply energy only when said auxiliary relay is picked up.

15. In a railway signaling system, in combination, a stretch of railway track over which are operated locomotives equipped with signaling apparatus responsive to the presence of coded alternating current energy in the track rails of the track stretch, the rails of said track stretch being divided by insulated joints into successive block sections, the rails of each block section being divided by insulated joints into a plurality of track sections, each track section having at the entrance end thereof a direct current code following track relay receiving energy over the section rails, each track relay having associated therewith an auxiliary relay which is picked up when and only when the track relay is responding to coded energy, the auxiliary relay for the rearward track section in each block section being operative when released to effect the supply of coded direct current of a first frequency to the rails of the adjacent track section in the rear and when picked up to effect the supply of coded direct current of a second frequency to the rails of the adjacent track section in the rear, the track relays of each of the track sections except the track sections at the entrance ends of the block sections being effective when responding to coded direct current energy to supply coded direct current of the same frequency to the rails of the adjacent track section in the rear, each track section having at the exit end thereof means for supplying to the rails of such section alternating current energy coded at the same frequency as the direct current energy supplied to the rails of such section, the alternating current supply means for each track section being controlled by trafiic conditions in such section and by the auxiliary relay of the adjacent track section in advance so as to be effective to supply energy only when said auxiliary relay is picked up and the section to which the energy is supplied is occupied.

WARREN W. SEITZ.