US2235156A - Railway signaling system - Google Patents

Description

March 1941- R. R. KEMMERER RAILWAY SIGNALING SYSTEM 2 Sheets-:Sheet ,1

Filed July 31., 1940 RP. Y m% m mm w v T m m M 3 mm m l M l m Fig. 2.

Patented Mar. 18, 1941 RAIUWAY SIGNALING SYSTEM Ralph E. Kemmerer, Swissvale, Pa., assignor to The Union Switch & Signal Company Swissvale, Pa., a corporation of Pennsylvania 7 Application July 31, 1940, Serial No. 348,937

16 Claims.

vide a signaling system of the type described.

and incorporating means to check the integrity of the lamps of the markers and controlling the supply of energy to the sections in the rear so that if while a section is occupied the lamp of the marker for that section is defective, energy effective to produce a proceed indication on the locomotive of a following train'will not be supplied to the rails of the adjacent section in the rear.

Another object of my invention is to provide an improved coded signaling system employing wayside signals, and having lightout protection means arranged so that in the event a signal lamp is defective, the signal will be conditioned to display its next most restrictive indication, while the energy supplied to the section in the rear will be changed so as to be commensurate with the indication displayed by the signal.

A further object of my invention is to provide a railroad signaling system having wayside signals controlled by coded track circuit apparatus, the signals being normally dark and being lighted on the approach of a train, the equipment being arranged so that if the lamp of a signal is defective, the coded energy supplied to the adjacent section in the rear will be altered so that a train in the section in the rear of the defective signal will receive a more restrictive indication than it normally would.

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

I shall describe three systems embodying my invention, and shall then point out the novel features thereof in claims.

In the drawings Fig. 1 is a diagram showing a signaling system having a marker lamp at the entrance to each block and incorporating lightout protection means provided by my invention, and

Figs. 2 and 3 are diagrams showing wayside signaling systems employing lightout protection means provided by this invention.

Referring to Fig. 1 of the drawings, there is shown therein a stretch of railway'track having track rails I and 2 over which traflic moves 5 in the direction indicated by the arrow, and which are divided by insulated joints 3 into the usual track sections. Two complete sections are shown and are here designated HT and UT.

The track stretch shown in Fig, 1 employs cab signals on the locomotives traversing the track stretch, and does not have wayside signals except for a marker M at the entrance to each block or track section.

The signaling system shown in-Fig. 1 is of the three-indication variety and makes use of energy coded at two different code frequencies. This coded energy is provided by code transmitters CT having two circuit making and breaking contacts and I80 which are operated at different speeds by a motor or other means so as to provide 75 or 180 energy impulses per minute which are separated by periods of equal duration during which no energy is supplied.

The system shown employs coded alternating current in the track circuits. This current may be suppliedirom any suitable source and may be distributed throughout the track stretch by a transmission line, not shown, the. terminals of the source being designatedBX and CK.

- The cab signal apparatus adapted to be used in connection with the wayside'apparatus is not a part of this invention and any form of equipment 'well known in the art may be employed. One form of apparatus which may be employed is shown in Letters Patent of the United States No. 1,986,679 issued January 1, 1935, to Lloyd V.

Lewis.

Each of the track sections has a code following track relay TR at the entrance end of the sec- 40 tion and receiving energy over the section rails through a rectifier RX. Each of the track relays has associated therewith code detecting means comprising a transformer DT and a slow releasing relay H, while, each marker lamp M has associated therewith a lightout r'elay'LOR.

The equipment is shown in the condition which it assumes when section I2T and the sections in advance are vacant. At this time energy .of 180 50 code frequency is supplied through-the track transformer IITT to the rails of section HT by the means associated with the adjacent section in advance. The equipment associated with the section in advance operates in the same. manner as that associated with section HT, as hereinafter explained in detail.

The energy supplied to the rails of section I [T feeds through the rectifier IIRX to the track relay TR and produces code following operation of this relay so that the end portions of the primary winding of the transformer llDT are alternately energized from a local source of direct current, and current is induced in the transformer secondary winding, while a contact of the track relay rectifies the energy supplied from the transformer secondary Winding to the relay III-I. The relay H is of a type which is slow to release its contacts with the result that its contacts remain picked up during the intervals between the supply of impulses of energy thereto.

As relay H is picked up, its contact 2i! establishes the circuit to supply energyvof 180 code frequency to the rails of the section in the rear, while contact 2| interrupts the circuit of the marker lamp HM.

As energy of 180 code frequency is supplied to the rails of section I2T, the relay 12H is picked up and establishes the circuit to supply energy of 180 code frequency to the section farther in the rear, while the circuit of the lamp [2M is interrupted.

As energy of 180 code frequency is supplied to the rails of the section in the rear of section IZT, the cab signal apparatus, shown diagrammatically, for a locomotive in that section will operate to provide its green or clear indication.

If the locomotive advances into section I2T, the cab signal apparatus on the locomotive will respond to the energy of 180 code frequency supplied to the track rails toprovide the engineer with a clear signal indication.

On entrance of the locomotive into section lZT the track relay I2TR is shunted and ceases to respond to coded energy with the result that energy is no longer supplied through the transformer IZDT .to the relay IZH. On release of relay IZH contact 2| of the relayestablishesthe circuit of themarker lamp IZM, and if the filament of this lamp is intact so that the lamp is lighted, the lightout relay IZLOR will pick up as the winding of this relay is connected in series with the marker lamp. v

On picking up of the lightout relay IZLOR. the circuit for supplying energy of 75 code frequency to the section in the rear is established, and is traced from terminal BX of the source of alternating current through contact 15 of the code transmitter T, front contact 23 of relay I2LOR, back contact 20 of relay l2I-I and primary winding of the track transformer I3TT to terminal OX.

When the train advances into section I IT, the equipment associated with this section operates in the manner explained in connection with section I 2T so that energy of '75 code frequency is supplied to the rails of section I2T, while the marker lamp HM is lighted.

As long as any portion of the train remains in section IZT, the track relay IZTR is shunted'so that energy of '75 code frequency is supplied to the section in the rear, while the marker lamp I2M is lighted to indicate to a following train that section IZT is occupied.

In addition, as long as any portion'of the train remains in section I2T, the track rails are shunted and coded signal control current does not flow in the rearward portions of the track rails ofsection I2T so that if a following train should code frequency thereto.

enter this section, the cab signal apparatus on the locomotive of the train would be conditioned to display its most restrictive or stop indication.

When the rear of the train vacates section IZT, the energy of 75 code frequency feeds to the track relay IZTR and produces code following operation of this relay with the result that energy is supplied through the transformer |2DT to the relay HE, and contact 20 is picked up to interrupt the circuit for supplying energy of '75 code frequency to the section in the rear and to establish the circuit for supplying energy of In addition, contact 2| of relay I2I I is picked up so that the marker lamp I 2M is extinguished, while the lightout "relay I ELOR releases.

maintain the supply of energy of 180 code fre- H .quency. to the section in the rear.

Operation'of equipment show'rt in Fig. 1 if a marker lamp is defective The equipment provided by this invention includesmeans tocheck the integrity of the filaments ofthe marker lamps so that if one of these lamps fails ,to light when it should, the energy supplied to the section in the rear will be controlled so that the cab signal apparatus on a train entering th section in the rear will not receive. a proceed indication, but instead will receive the stop or. most restrictive indication.

For purposes of illustration it will be assumed that a train enters section .I IT and that the lamp of the marker lamp MM is. defective and fails to light.

Whenthe. train enters section HT, the track relay l I TR is shunted and energyisno longer supplied through transformer MDT to the relay l |.H, and' this relay releases so that contact 20 interrupts the. circuit for supplying energy of 180 code frequency to the rails of section IZT.

In addition, contact 2! of relay H is released and establishes the circuit of the lamp 1 l M, but as it is assumed that the lamp is defective, this lamp is not lighted While the relay l ILOR is not energized and its contact 23 remains released. Accordingly, energy of '75 code frequency is not supplied to the rails of section I2T, and instead steady energy is supplied thereto over a circuit which is traced from terminal BX, over back contact 23 of-relay lILOR,'back contact 20 of relay IIH, and the primarywinding of transformer I2TT.

When the train under consideration vacates section IZT, this steadyenergy will feed to the track relay I2TR and keep it steadily energized so that energy is not supplied through the transformer I2DT to the relay IZH and this relay is released to light the lamp IZM and to effect the supply of energy of '75 code frequency to the section in the rear.

Accordingly, a second or following train will receive a restrictive indication when it enters the section in the rear of section IZT, While it will be warned by the marker lamp I2M when it reaches sectionlZT. If the train advances into section IZT, the cab signal equipment on the locomotive 'will give the most restrictive indienergy wil1 no longerbe supplied through the decoding transformer MDT to the relays NIH and NJ.

On release of relay MI-I contact 30 interrupts the circuit of the lamp G and establishes the circuit of the lamp R of signal MS. .The circuit of the lamp R is traced from terminal B through back contact 39 'of relay I ll-I, winding of lightout relay iRLO, and lamp R to terminal C. If the lamp R is not defective and becomes lighted, the relay IQRLO will be energized and its contact 35 is picked up and interrupts the circuit of the marker lamp M.

In addition, on release of the relay 14H contact 3 3 interrupts the circuit for supplying energy of 180 code frequency to the rails of section IGT, and establishes the circuit for supplying energy of '75 code frequency to section -|5T. This circuit is traced from terminal BX through code transmitter contact 75, and back contact 3 1 of relay Mil-I to the primary winding of transformer l5TT.

As long as the train is in section MT, the cab signal equipment on the locomotive, if the locomotlve is provided with this equipment, will continue to receive energy of 180 code frequency supplied by the equipment associated with section LiT and the cab signal equipment will display its clear indication.

When the train advances into section I3T, the equipment associated with that section Will operate as described in detail in connection with section l iT to supply energy of code frequency to the rails of section MT, and tocondition the signal its to display its red or stop indication.

When the train clears section I 4T, energy of 75 code frequency feeds to the track relay MTR, and this relay operates to supply energy through the transformer l-DT to the relay HI-I. As the track relay is responding to energy of the '75 code frequency, too little energy is supplied through the resonant unit HiRU to pick up the relay MJ.

On picking up of relay MEI contact 30 interrupts the circuit traced above for lighting the red lamp R and establishes the circuit of the yellow or caution lamp Y of signal MS. This circuit is traced from terminal B over front contact 38 of relay ii-I, back contact 3! of relay 5 ZJ, winding of lightout relay I l-2L0, and lamp Y to terminal C. If the lamp Y lights as it should, the relay l lYLO will be picked up so that the circuit for supplying energy" of code frequency to the section in the rear is established. This circuit is traced from terminal BX over contact 8% of the code transmitter, front contact 36 of relay i iYLO, back contact 33 of relay lGLo, and front contact 3 of relay MH to the transformer I5TT.

When the train vacates section HST, the track relay for this section responds to energy of 75 code frequency, while the energy supplied to section MT is changed to 180 code frequency. On this change in the frequency of the energy supplied to section lfiT the track relay I5TR operates at a higher speed and sufficient energy is supplied through the resonant unit MRU to pick up the relay MJ.

When relay MJ picks up, its contact 3! interrupts the circuit of the yellow lamp Y and of the relay MYLO, and establishes the circuit of the green lamp G and of the relay I ZGLO. On picking up of the relay MGLO its contact 33 interrupts the circuit traced above for supplying energy of 18.0 "codefrequencyto section HT, and

-establishes'a connectionshunting the contact.36

of the relay MYLO so that energy of 180 code frequency continues to be supplied to section I 5T.

Operat on of system shown in Fig. 2 in the event a signal lamp is defective The system provided by' this invention is arranged so that if any one of the signal lamps is defective and fails to light when it should, the lamp for the next most restrictive indication will be lighted, while the energy supplied to the section in the rear is controlled so as to be consistent with the aspect displayedby the signal.

If, for example, the green lamp G of signal MS is defective and does not become lighted when the relays MH and NJ are picked up, the relay MGLO will be released and its contact 38 will establish a circuit to "light the yellow lamp Y. This .circuit includes front contact 30 of relay i l-H, back contact 38 of relay MGLO, winding of relay MYLO, and lamp Y. At this time the relay I lGLO is released and the relay MYLO is picked up so that a circuit is established to supply energy of 180 code frequency to section I5T. This is'the code frequency which it is proper to supply to section I5T when the signal MS is displaying-its yellow or caution indication.

The system is also arranged so that if the yellow light Y is defective and does not become lighted when it should be, the red lamp R will be lighted, While the energy supplied to the section in the rear will be changed from 180 to '75 code frequency.

The yellow lamp should be lighted when the relay I 4H is picked up and the relay NJ is released, or when the relay Iii-I is picked up and the relay MGLO isreleased. In either case the relay MYLO will be picked up if the lamp lights, but'will be released if the lamp fails to light.

When the relay MYLO is released at a time when the relay MGLO is released, a circuit is established to light the red or stop lamp R. This circuit is traced from terminal B through back contact 39 of relay MYLO, back contact 40 of relay I4GLO, winding of relay l iRLO, and lamp R to terminal C. I

In addition, when relay l' l-YLO releases at a time when relay MGLO is released and relay 14H is picked up, a circuit is established to supply energy of 75 code frequency to the section in the rear. Thiscircuit is traced from terminal BX over code transmitter contact l5, back contact 36 of relay MYLO, back contact 33 of relay MGLO, and front contact 34 of relay MH to the track transformer I5TT.

If the red lamp R is intact and becomes lighted, the relay MRLO will be picked up and contact 35 will interrupt the circuit of the marker lamp M.

It will be seen, therefore, if for any reason the yellow light Y fails to light when it should, the red light R will be lighted instead, while the energy supplied to the section in the rear will be changed from"180 to 75 code frequency. This will cause the signal for the section in the rear to change its indication from green to yellow so that a following train will receive a caution indication at the entrance to section MT and will not approach the signal MS at full speed at a time when the signal MS is displayingits red or stop cation in response to the presence of steady uncoded energyin the rails of section I2T.

As the following train receives the most restrictive indication when it reaches section lZT, it will be moving at very slow speed when it approaches themarker lamp HM, and failure ofthis lamp to be illuminated will not create a serious hazard as the train will be able to stop before striking the train present in section HT.

When the first train vacates section IIT, the track relay IITR responds to coded energy and relay Ill-I picks up to interrupt the supply of steady energy to the rails of section IZT, and to establish the circuit to supply energy of 180 code frequency to the rails of section |2T in the usual manner.

From the foregoing it will be seen that when the marker lamp of an occupied block is defective, the energy supplied to the section in the rear is controlled so that a following train will receive the most restrictive signal indication one block before it reaches the defective lamp. This insures that the following train willreduce its speed so as to be able to stop before entering the occupied block.

If the energy supplied to the rails of the section at the rear of a section having a defective marker lamp were not controlled in this manner, a following train would receive a proceed indication in the section in the rear of the defective lamp and would be traveling at a substantial speed when it approached the defective lamp, and the engineer might not see the lamp since the lamp would not be lighted as it should be. Accordingly, the engineer of the second train would not know when he reached the entrance of the occupied block and would continue on into the occupied block. After the locomotive of the second train enters the occupied block, the cab signal equipment carried by it will give the most restrictive indication.

However, if the first train stopped with the rear end thereof adjacent the entrance end of section HT, the second or following train might not be able to stop soon enough after entering the occupied section and receiving the stop indication to avoid hitting the first train.

As the system provided by this invention provides a marker lamp to mark the entrance to an occupied block, following trains are warned when they approach an occupied section and can stop before entering the section or before reaching a train in the section.

Furthermore, the system is arranged so that if the marker lamp is not illuminated when it should be, the supply of coded energy to the section in the rear is cut off, while the marker lamp at the entrance of the section in the rear is lighted and the energy supply to the rails of that section is controlled to cause the cab signal equipment on a locomotive in the section in the rear of the defective lamp to. display its most restrictive indication.

It will be seen, therefore, that the system provided by this invention provides a maximum degree of safety both when the system is functioning as intended, and when thelamp of one of the marker lamps is defective.

The means provided by this invention for controlling the supply of coded energy to the section in the rear is applicable to a signaling system employing wayside signals, and Fig. 2 is a diagram showing this application of the invention.

'Construction and operation of modification shown in Fig. 2

Referring to Fig. 2, there is shown therein a stretch of railway track employing wayside signals of the color light type. One block section, identified as section MT, together with portions of two other sections, is shown.

Each of the track sections has at the entrance end thereof a wayside signal having a green or clear lamp G, a yellow or caution lamp Y, a red or stop lamp R, and a marker lamp M which may be of any distinctive color.

The system shown in Fig. 2 makes use of coded energy of two code frequencies in the track circuits thereof, while it has decoding means similar to the code detecting means employed in the system shown in Fig. l.

The equipment is shown in Fig. 2 in the condition which it assumes when the track stretch is vacant. At this time energy of 180 code frequency is supplied to the rails of section I4T by the equipment associated with the adjacent section in advance, while this energy feeds through the rectifier MRX to the track relay MTR and produces code following operation of this relay.

As a result of code following operation of the track relay MTR, the two end portions of the primary winding of the decoding transformer MDT are alternately energized from a local source of direct current, not shown, and energy is induced in the secondary windings of the transformer, while a contact of the track relay rectifies the energy supplied from one of these secondary windings to the winding of relay 14H. Energy is supplied from the other secondary winding of the transformer MDT through a resonant rectifier unit MRU to the relay NJ.

The resonant unit RU includes a capacitor and an inductance which are arranged and proportioned so as to pass energy suificient to operate the relay J when the track relay is responding to energy of 180 code frequency and to pass too little energy to operate the relay J when the track relay is responding to energy of a different code frequency, such as '75 code frequency. The unit RU includes a rectifier which converts into direct current the alternating current supplied through the unit.

As the track relay MTR. is responding to energy of 180 code frequency, the relays MH and J are both picked up, and the green or clear lamp G of signal MS is lighted by current supplied over the circuit which is traced from terminal B of a local source of direct current through front contact 30 of relay MH, front contact 3| of relay NJ, winding of lightout relay MGLO, and lamp G to terminal C.

As the relay NIH is picked up, the circuit for supplying energy of 180 code frequency to the section in the rear is established, and is traced from terminal BX of the source of alternating current signal control energy through contact I of code transmitter MCT, front contact 33 I of relay MGLO, front contact 34 of relay NH, and primary winding of track transformer IS'II to terminal CX.

As energy of code frequency is supplied to the rails of section l5T, the signal, not shown, for that section is conditioned to display its green or clear indication, while the cab signal equipment of a locomotive present in section l5T will display its clear indication.

If a train moving in the normal direction of traffic, that is from left to right, enters section MT, it will shunt the track relay TR. and

lighted, while steady uncoded energy will be supplied to the section in the rear.

The red lamp R of signal S should be lighted when the relay l lH is released, or when relay MH lamp M, while contact 42 will establish a circuit.

to supply steady energy to the section in the rear.

One circuit of the marker lamp M is traced from terminal B through back contact 39 of relay MYLO, back contact 40 of relay MGLO, and back contact 35 of relay MRLO to lamp M. Another circuit for the marker lamp is traced from terminal B through back contact 39 of relay MYLO, back contact 40 of relay MGLO, and back contact 35 of relay MRLO and lamp M to terminal 0.

The circuit for supplying steady energy to section I5TT is traced from terminal BX through back contact 42 of relay MRLO and thence over back contact 34 of relay MH, if this relay is re.- leased. If relay MI-I is picked up, the circuit for supplying steady energy to the section in the fear is traced from terminal BX over back'contact 42 of relay MRLO, back contact 36 of'relay MYLO, back contact 33 of relay MGLO, and front contact 34 of relay H. In either case the circuit for supplying energy of '75 code frequency is maintained, but the steady energy supplied over back contact 42 of relay MRLO fills in the off periods in the code so that the code is ineffective.

On the supply of steady energy to the rails of section I5T the track relay for that section is steadily picked up with the result that the redor stop lamp of the associated signal is lighted, while energy of 75 code frequency will be supplied to the section farther in the rear to condition the signal for that section to display its caution indication.

Accordingly, a-following train will receive a caution indication two blocks before it reaches the signal with the defective lamp, and will receive a stop indication one block before it reaches that signal. The train, therefore, will be traveling at slow speed when it reaches the signal at which the marker lamp is lighted and the engineer will have ample time to stop before striking a train in advance of the marker lamp. The marker lamp serves to identify the signal and shows the location of the signal, and also marks the entrance to an occupied block.

From the foregoing it will be 'seen that the system provided by this modification of the invention is arranged to check the integrity of the lamps of the wayside signals, and that in the event one of these is defective, the lamp providing the next most restrictive indication is lighted, while the energy supplied to the section in the rear is changed to that proper for that signal indication.

Construction and operation of modification shown in Fig. 3

In the system shown in Fig. 3, the lamps of the signals are normally dark, and are lighted on entrance of a train into the section in the rear of the signal. Any desired means for approach lighting may be employed to control the circuits of the signal lamps. The means shown in the drawings is substantially the same as that shown in Letters Patent of the United States No. 2,174,255 to Herman G. Blosser.

Referring to Fig. 3 of the drawings, there is shown therein a stretch of railroad track having track rails l and 2 which are divided by insulated joints 3 into the customary successive track or block sections. One complete section, which is identified as section I8T, together with portions of the adjoining sections is shown.

Each of the track sections has at the entrance end thereof a wayside signal S together with a track relay and decoding means for controlling the signal, and, in addition, means for controlling the supply of coded energy to the section in the rear.

The equipment is shown in the condition which it assumes when the track stretch is vacant. At this time energy of 180 code frequency is supplied to the coding relay I'ICTM in the manner hereinafter explained in connection with section I8T, and the contacts of this relay are picked up and released at this rate.

As a result of code following operation of the coding relay IICTM impulses of master code energy are supplied from the track battery I8TB to the rails of section I8T during the picked-up periods of the relay contacts, while during the released periods of'the relay contacts connection is established to permit impulses of feed back energy to be supplied from the section rails to the pick-up winding 41 of the relay IIAR, and to also establish a circuit to supply energy from the battery I8TB to the holding winding 52 of the relay AR and to the winding of the relay ll'AP when cont-act 5| of relay l'lAR picks up.

The master code energy supplied to the rails of section I8T feeds to the track relay IBTR and causes code following operation of this relay with the result that energy is supplied through the decoding transformer |8DT to therelay I8H and also to the impulse relay I8IR. As a result of the supplyv of energy to the impulse relay 181R this relay operates to disconnect the track relay l8TR. from the rails of section I8T and to supply impulses'o-f feed back energy from the battery IBAB to the rails of section I8T during the ofi periods in the master code supplied to the rails of section IST.

As long as the track section is vacant, therefore, the track relay IBTR responds to master code energy, While feed back energy is supplied over the section rails to the relay I'IAR which energizes the slow releasing relay IIAP.

The construction and operation of this portion of the system is not a part of this invention and is described in detail in the patent to Blosser, identified above.

The relay HAP has associated therewith a slow releasing repeater relay IIAPP which is energized when the relay I'IAP is picked up. The relays I (AP and I'IAPP together control the lamp of the signal HS, and also control the supply of energy to the decoding unit associated with the track relay for section "T for detecting when the relay is responding to energy of 180 code frequency. The operation of this portion of the apparatus is best understood by reference to the corresponding apparatus associated with section l8T.

As the track stretch is assumed to be vacant,

the relays [BAP and IBAPP are energized inthe manner explained in detail above, and the circuit for supplying energy to the primary winding of the decoding transformer IEDTA is interrupted by contact 56 of relay IBAP. Accordingly, energy is not supplied from this transformer to relay IBJ and the relay NJ is released. As the circuit of the decoding transformer I8DTA' is interrupted when section I9T is vacant, no energy is consumed by this transformer and the resonant rectifier unit IERUA; and there is a substantial saving of current for this reason. As long as section I9T is vacant, the signal ISS is dark and there is no need to energize the relay IBJ.

At this time the circuit of the lightout relay IBLOR and of the lamp IBL of signal IBS is interrupted by contact 56 of'relay IBAPP and by contact 59 of relay IBAP, while the circuit of the 180 code transmitter ISCTA is established as'contact SI of relay |8APP and contact 62 of relay I8H are picked up. The contact 180 of code transmitter I8CTA, therefore, is operated to establish and interrupt the circuit of the coding relay IBCTM 180 times a minute. The circuit of the coding relay IBCTM is complete at this time as contact 65 of relay NH and contact 66 of relay I8AP are picked up. The coding relay ISCTM, therefore, operates to supply master code energy of 180 code frequency to the rails of section lfi'I.

At this time as the contact 68 of relay WA? is picked up, the circuit for supplying energy to the operating mechanism ISG of the signal IBS is interrupted.

From the foregoing it will be seen that when section IST is vacant, the relays I8AP and |8APP are energized with the result that the signal I88 is dark, the operating mechanism of the signal is deenergized, and the decoding transformer I8DTA is deenergized.

When a train traveling in the normal direction of trafiic, that is from left to right, enters section I9T, it shunts the track relay, not shown, for that section with the result that feed back energy is no longer supplied to the rails of the section and the relay IBAP releases. Release of contact 54 of this relay establishes the circuit for supplying alternating current energyto the track transformer ISTT so that coded cab signal energy is thereafter supplied from any suitable source of alternating current, the terminals of which are designated BX and CK, to the rails of section NET to operate the cab signal equipment on the locomotive of the train which has entered this section. The alternating current energy supplied to the rails of section lliT is coded at the rate determined by the coding relay ISCTM,

and this relay is operating at this time to provide the 180 code frequency so that the cab signal equipment will be conditioned to display its clear indication.

In addition, on release of relay ISAP, contact 58 interrupts the circuit of relay IBAPP and establishes the circuit for supplying energy to the signal mechanism I8G. The relay IBAPP is slow releasing and its contacts remain picked up for a substantial time interval after release of relay IBAP. Accordingly, on release of the relay |8AP the circuit for supplying energy to the primary winding of the transformer IBDTA is established. This circuit is traced from terminal B of a local source of direct current, not shown, through front contact 58 of relay IBAPP, back contact 56 of relay I8AP, and front contact HI.v of relay IBH to contact H of the track relay i8TR. which alternately establishes connection with the two end terminals of the transformer primary winding, while the center terminal of this winding is connected to terminal C of the source of current.

As soon as the circuit for supplying energy to the transformer ISDTA is completed, energy is induced in the transformer secondary winding and is supplied therefrom through the resonant rectifier unit I8RUA to pick up the relay I8J. Picking up of the contacts 13 and M of relay lilJ changes the polarity of the energy supplied to the signal mechanism [8G to cause it to condition the signal to display its green or clear indication. The circuit for energizing the mechanism I8G is traced from terminal B through back contact 63 of relay I8AP, front contact 16 of relay IBI-I, front contact 13 of relay I8J, signal mechanism IBG, and front contact 14 of relay IBJ to terminal 0.

On expiration of a short time interval after release of relay I8AP the relay ISAPP releases. This time interval is long enough to permit the relay I8J to pick up and to permit the mechanism of signal I8G to position itself before relay I8APP releases.

On release of relay IBAPP, contact 53 interrupts the circuit traced above for energizing the transformer I8DTA, and establishes the circuit of the lig'htout relay IBLOR and the lamp ISL. This circuit includes back contact 58 of relay IBAPP and back contact 59 of relay ISAP.

If the lamp I SL is in good condition and becomes lighted, the lightout relay I8LOR will be energized and its contact 'l'l will pick up and establish a circuit to supply energy to the transformer IBDTA so that energy continues to be supplied to the relay I8J. There is a short interruption in the supply of energy to the transformer IBDTA from the time at which relay IBAPP releases and the time at which relay I8LOR picks up. The relay "U is slow releasing, however, and remains picked up during this time interval.

In addition, on release of relay ISAPP, contact 6| interrupts the circuit traced above for energizing the code transmitter IBCTA, but on picking up of the relay I8LOR its contact 19 establishes a circuit to energize the code transmitter I8CTA so that the code transmitter continues to operate.

Release of contact 66 of relay I8AP interrupts the circuit traced above for energizing the coding relay I8CTM, but another circuit for energizing this relay with energy of 180 code frequency is established on picking up of the relay I8LOR so that energy of 180 code frequency continues to be supplied to the coding relay l8CTM and this relay continues to supply energy of 180 code frequency to the rails of the section in the rear. The circuit for supplying energy to the relay IBCTM is traced from terminal B through contact I of code transmitter I8CTA, front contact 8i of relay IBLOR, front contact 88 of relay 18H and back contact 65 of relay I8AP to the relay I8CTM.

From the foregoing it will be seen that when a train enters section IQT, the relays ISA]? and I'8APP become released and establish the circuit of the transformer I8DTA so that the relay IBJ is energized, while energy is supplied to the signal mechanism I 8G to condition the signal to display its clear indication. In addition, alternating current energy issupplied to the rails of section I'ST to operate the cab signal apparatus on the locomotive to provide a clear cab signal, while energy is supplied to the lamp IBL of the signal IBS to light the lamp and cause the signal to display its clear indication.

When the train advances into section l8T, the track relay |8TR is shunted and energy is no longer supplied through the transformers I8DT and IBDTA to the relays I8H and |8J and these relays release. Release of contact 16 of relay I8H interrupts the circuit for energizing the signal mechanism I8G, and this mechanism thereupon conditions the signal N36 to display its red or stop indication.

On shunting of the track relay I8TR. energy is no longer supplied to the impulse relay IBIR and this relay no longer supplies impulses of feed back energy to the rails of section I8T. Accordingly, the relays MAP and "AP? become released andcondition the signal ITS to display its clear indication, while alternating current cab signal control energy is supplied to the rails of section I8T.

In addition, on shunting of the track relay IBTR and release of the relay NH a circuit is established to energize the code transmitter I SC'I'B which provides impulses of energy of '75 code frequency. The circuit of this code transmitter is traced from terminal B through back contact 6| of relay I8APP, back contact of relay 18H, and front contact of relay I8LOR tothe code transmitter NOTE. The contact 15 of the transmitter I 8CTB is operated, therefore, to supply energy of '75 code frequency to the coding relay I8CTM over the circuit which is traced from terminal B through contact 15, front contact 81 of relay IBLOR, back contact 88 of relay [8H, and back contact 66 of relay IBAP. The coding relay I8CTM, therefore, operates to supply impulses of master code energy of the '75 code frequency to the rails of section I9T, and when the train vacates section IST, these impulses of master code energy feed to the track relay for section I 9T, while the impulse relay associated therewith then operates to supply impulses of feed back energy to the section rails as previously explained in connection with section MT.

,The impulses of feed back energysupplied to section l9T cause the relay I8AP to pick up and its contact 68 establishes the circuit to supply energy to the relay I8APP to pick it up, while contact 68 interrupts the circuit of the signal mechanism I8G.

On picking up of relay I8AP, contact 54 interrupts the supply of alternating current cab signal control energy to the rails of section IBT, wlhile contact 66 interrupts the previously traced circuit for supplying energy of 75 code frequency to the coding relay i8CTM and establishes another circuit for supplying energy thereto. This circuit is traced from contact 15 through back contact 65 of relay I8H and front contact 66 of relay I8AP.

On picking up of relay ISAP, contact 59 inter rupts the circuit of the lamp I8L and of the relay l8LOR so that the lamp is extinguished and the relay ISLOR releases and its contact 85 interrupts the circuit for supplying energy to the code transmitter IBCTB. However, on picking up of relay I8APP, its contact 6| establishes a circuit which includes back contact 62 of relay l8H for energizing the code transmitter I8CTB and it continues to operate so that energy of 75 code frequency is supplied to the rails of section |.9T to condition the signal for enter section I9T and release the relays ISAP and I8APP so that lam-p I8L is lighted, the signal IBS will display its red or stop indication.

When the train under consideration, that is the train in section IBT, advances into section HT, the track relay for that section is shunted and the equipment associated therewith operates in the manner explained in connection with section I8T to supply mastercode energy of '75 code frequency to the rails of section MT and to condition the signal [TS to display its stop indication whenthe signal lamp is lighted.

When the train vacates section IBT, coded energy is supplied to the track relay I8TR and energy is suppliedthrough the transformer I8DT to the relay I8H and also to the relay I8IR so that relay I8H picks up, while the relay IBIR supplies impulses of feed back energy to the section rails to produce code following operation of the relay I'iAR. with resultant energization of the relays HA]? and llAPP.

When the relays HAP and llAPP are picked up, the circuit of the lamp of the signal ITS is interrupted, while the supply of alternating current cab signal control energy to section |8T is cut off.

When relay I8H picks up, its contact 62 interrupts the circuit for energizing the transmitter I 8CTB and establishes the circuit for energizing the transmitter IBCTA, assuming that the contact 6| of relay |8APP is picked up, and this transmitter operates to supply energy of code frequency.

In addition, on picking up of the relay I8H its contact 65 interrupts the circuit through which energy of '75 code frequency has been supplied to the coding relay IBCTM and establishes a circuit to supply energy of 180. code frequency thereto. The relay I8CTM, therefore, operates at the higher rate and supplies master code impulses of 180 code frequency to the rails of section IST.

If at this time a second or following train should enter section [QT and release the relays I8AP and IBAPP and establish the circuit of the transformer I8DTA, too little energy would be supplied through the resonant rectifier unit I8RUA to pick up the relay l8J since the track relay IBTR is responding to energy of 75 code frequency. The relay I8J, therefore, would remain released and the polarity of the energy supplied to the signal mechanism. I8G would be such as to condition the signal to display its yellow or caution indication when the signal lamp is lighted. The circuit for supplying energy to the mechanism I8G would be complete at this time as contact 68 of relay I8AP is released and contact 16 of relay 18H is picked up.

It will be seen, therefore, that if a second or following train enters section I 91 at a time when section I8T is vacant and section HT is occupied, the signal I 8S will be conditioned to display its yellow or caution indication, while mastercode energy of 180 code frequency will continue to be supplied to the rails of section |9T.

When the train under consideration advances far enough to vacate section HT, the track relay for this section responds to energy of '75 code frequency with the result that the energy supplied to section EST is changed from 75 to 189 code frequency. On this change in the energy supplied to the relay IZZTR this relay operates at a more rapid rate and if a train enters section IT the frequency of the ener y supplied from the transformer lfiDTA will be such that sufficient energy will be supplied through the resonant unit IBRUA to pick up the relay I SJ to thereby condition the signal IBS to display its clear indication.

On this change in the code supplied to the relay ESTR energy of 180 code frequency continucs to be supplied to the rails of section iST.

Operation of the equipment shown in Fig. 3 in the event a signal lamp is defective The system provided by this modification of the invention is arranged so that if the signal lamp of a signal is defective and does not become lighted when it should, the energy supplied to the section in the rear will be controlled so that the signals in the rear of the one with the defective lamp will display more restrictive indications than they normally would.

When the track stretch is vacant, energy of 180 code frequency is supplied to the track relay I8TR, and when a train enters section I9T, the relay iSAP releases and interrupts the circuit of the relay I SAPP.

On release of relay ISAPP, the circuit of the transformer itDTA is interrupted, while a circuit is established to supply energy to the lamp I8L and the relay HZLOR. If the lamp is defective, no energy will flow in this circuit and the relay IELOR will remain released, while its contact T? will not establish the circuit to supply energy to the transformer I8DTA. Accordingly, energy will not be supplied to the relay NJ and the polarity of the energy supplied to the signal mechanism ISG will be such as to condition the signal to display its yellow or caution indication instead of its clear indication.

The equipment is also arranged so that at this time operation of the code transmitter I8CTA is discontinued, while opei ation of the code transmitter lSCTB is initiated. On release of contact SI of relay ISAPP the circuit of the code transmitter IQCTA is interrupted, while a circuit including back contact 6| of relay I8APP, front contact 80 of relay ISI-I, and back contact 19 of relay iSLOR, is established to energize the code transmitter GBCTB to cause it to operate and provide '75 code for the coding relay lBCTM.

From the foregoing it will be seen that on entrance of a train into section IST at a time when the track stretch is otherwise Vacant and when the lamp of the signal IBS is defective, the energy supplied to the coding relay |8CTM is changed from 180 code frequency to 75 code frequency with the result that energy of '75 code frequency is supplied to the rails of section IST. Accordingly, the cab signal equipment on the locomotive of the train in se tion IQT will be conditioned to display its caution indication instead of its clear indication and the engineer will reduce the speed of the train soas to be prepared to stop when he reaches signal l 853.

In addition, at this time the signal [BS is conditioned to display its yellow or caution indicae tion, if the signal lamp were lighted, so that any light reflected through the optical system of the signal will be yellow which will be consistent with the indication displayed by the locomotive cab signal apparatus.

When the train. enters section ldT, the track relay IETR isshunted and relay I8l-l becomes released and its contact 76 interrupts the circuit of the signal mechanism EEG and the mechanism conditions the signal 588 todisplay its stop indication provided the signal lamp were lighted.

On release of relay I8H contact 88 interrupts the circuit traced above for supplying energy of 75 code frequency to the coding relay IBCTM, while contact 80 of relay ISH interrupts the circuit for supplying energy to the code transmitter IBCTB. As a result, therefore, energy is not supplied to the coding relay KBC'I'M and this relay does not operate to supply coded energy to the rails of section MT. The track relay for section lST, therefore, will remain released after the train vacates section EQT, while no impulses of feed back energy will be supplied to the section rails and the relays ISA? and ISAPP will remain rel-eased.

When the train under consideration entered section lH'I', the track relay for that section was shunted and the equipment associated therewith operated as heretofore described in connection with section I8T to supply energy of '75 code frequency to the section in the rear. Accordingly, when the train vacates section I 9T the track relay ISTR continues to be released as master code energy is not supplied to the section rails, and energy of 75 code frequency continues to be supplied to the rails of the adjacent section in the rear of section IST.

If, therefore, a second or following train should enter the section in the rear of section I9T at a time when section NT is vacant and section IBT is occupied and the lamp of signal I88 is defective, the train will receive a caution indication from the wayside signal at the entrance to the section in the rear of section I9T, while the locomotive cab signal apparatus will also operate to provide its caution indication.

When the second or following train advances into section IQT at a time when section I9T is vacant and section IBT is occupied, the cab signal equipment on the locomotive of the train will operate to give its stop or most restrictive indication since at this time the coding relay IBCTM is not operating to supply coded energy to the rails of section IBT.

At this time as section HST is assumed to be occupied, the relay IBH is released and its contact l6 interrupts the circuit of the signal mechanism IBG with the result that the signal I8S is conditioned to display its red or stop indication, if the signal lamp were lighted, and any light reflected through the optical system of the signal will be red, which is consistent with the signal displayed by the cab signal equipment of a locomotive in section IQT.

In like manner, if a second or following train should enter section le'l'. after the first train has vacated section [8T and occupies section HT, the second train will receive a caution cab signal, while the signal His will be conditioned so that yellow light will be reflected therefrom.

When the first train occupies section l'iT, the equipment associated with that section operates as heretofore explained to supply master code energy of vF75 code frequency to the rails of section IST, and the track relay TR. responds to this energy so that energy is supplied through the transformer ISDT to the relay 18H.

On picking up of relay -l-8H contact 80 establishes a circuit to supply energy to the code transmitter IBCTB, while'contact 88 of relay [8H establishes a circuit to supply energy from the code transmitter I8CTB to the coding relay I8CTM. The circuit for energizing the transmitter lBC'I'B is traced from terminal .13 over back contact Bl of relay |-8APP, front contact 810 of relay 181-1, and back contact 19 'ofrelay I.8LOR, while the circuit for supplying energy to the coding relay I8CTM is traced from terminal B over contact 15 of the code transmitter IBC'IB, back contact .81 of relay I8LOR, front contact of relay h'iI-I, and back contact 66 of relay IBAP.

As a result of the supply of energy to the coding relay I BCTM this relay supplies master code energy of 75 code frequency to the rails of section IBT, and if at this time the section is vacant, the track .relay will respond to this coded energy, while feed back energy willbe supplied over the section rails so that the relays |8AP and ISAPP become picked up.

On picking up of relay IBAPP contact 61 interrupts the circuit traced above for energizing the code transmitter ItCTB and establishes a circuit including front contact 62 of relay IBH for energizing the code transmitter JBCTA. In addition, on picking up of relay IBAP contact 66 interrupts the circuit traced above forsupplying energy of 75 code frequency to the coding relay lSCTM and establishes a circuit including front contact 65 of relay [8H for supplyin energy of 180 code frequency to the coding relay IBCTM so that the energy supplied to section |9T is changed from '75 to 180 code and the signal for section IBT will display its clear indication when the section in the rear thereof becomes occupied. This is proper as the sections IBT and IQT are assumed to be vacant.

If at this time a second or following train enters section 1ST, the supply of feed back energy over the rails of this section will be cut off and the relays L8AP and l-SAPP will become released to thereby discontinue the supply of energy of 180 code frequency to the relay ISCTM, and to supply energy of 75 code frequency thereto so that energy of "75 code frequency will be supplied to the rails of section [9T to condition the locomotive -cab signal apparatus to display its yellow or caution indication.

On release of relay lsAP contact 68 establishes the circuit including front contact 16 of relay Hill for supplying energy to the signal mechanism 18G, and as the contacts of the relay LBJ are released, the polarity of the energy supplied to the mechanism MiG is such that the signal will be conditioned to display its yellow or caution indication if the signal lam-p were lighted. Accordingly, any light reflected through the optical system of the signal will be consistent with the aspect displayed by the locomotive cab signal apparatus.

From the foregoing it will be seen that the modification shown in Fig. 3 is arranged so that if the signal lamp is defective, the supply of energy of 180 code frequency to the adjacent section in the rear will be cut off as soon as a train enters the section in the rear of the signal and energy of '25 code frequency will be supplied instead so that the cab signal equipment on the 10- comotive of the train will display its caution indication and the train will approach the defective signal at reduced speed.

In addition, it will be seen that the system is arranged so that when a signal is defective and a train passes through the track stretch, the supply of energy to the rails of the section in the rear of the section with the defective signal is cut off so that the signal for the section in the rear of the defective signal will continue to display its stop indication after the section is vacated and as long as the section with the defective signal is occupied. This insures that as long as the section with the defective signal is occupied that the signal for the section next in the rear will display its stop indication.

As there is in the rear of an occupied section one properly functioning signal which is condie tioned to display its stop indication, following trains will be given ample warning of the presence of the first train and will be prepared to stop before reaching the first train.

In addition, it will be seen that the'system is arranged so that the'mechanism of a signal with a defectivelamp is .conditioned to cause light refiected through the optical system of the signal to give an indication which is consistent with that given by the cab signal equipment on the 1. In a coded railway signaling system, in com bination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a track relay receiving energy over the rails of said forward section, a signal governing trafiic in said forward section, said signal including a lamp, means responsive to code following operation of said forward section track relay and controlling the circuit of said signal lamp and also controlling the supply of coded energy to the rails of said rearward section, means responsive to flow of energy in the circuit of said lamp for also controlling the supply of coded energy to the rails of said rearward section, and traffic governing means responsive to the flow of coded energy in the rails of said rearward section.

2. In a coded railway signaling system, in com-, bination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, a signal governing traffic in said section, said signal including a lamp, means for supplying coded energy to the rails of said forward section, a track relay receiving energy over the rails of said forward section, an auxiliary relay associated with said track relay, means operative when and only when 'said' track relay is responding to coded energy to energize the auxiliary relay, said auxiliary relay being operative when released to establish a circuit to supply energy tosaid signal lamp, means responsive to flow of current in the circuit of said Gil bination, a stretch of railroad track having a pair of track rails divided by insulated joints into a plurality of successive track sections including adjoining forward and rearward sections, a signal governing movement of traffic in said forward section, said signal including a lamp, a track circuit for the forward section comprising means for supplying energy to the track rails at the exit end of the section and a track relay receiving energy from the section rails at the entrance end of the section, means controlled by said track relay and operative when said relay is deenergized to establish a circuit to supply energy to said. signal lamp, means responsive to the flow of energy in the circuit of said lamp and controlling the supply of coded energy to the rails of said rearward section, and indication means responsive to the flow of coded energy in the rails of said rearward section.

4. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joint-s into a plurality of successive track sections including a forward and a rearward section, a signal'governing trafiic in said section, said signal including a lamp, means for supplying coded energy to the railsof said forward section, a track relay receiving energy over the rails of said forward section, an auxiliary relay associated with said track relay, means operative when and only when said track relay is responding to coded energy to energize the auxiliary relay, said auxiliary relay being operative when released to establish a circuit to supply energy to said signal lamp, a lightout relay included in series with said signal lamp, means operative when the auxiliary relay is released provided the lightout, relay is picked up to supply coded energy to the rails of said rearward section, and traffic governing means responsive to the flow of coded energy in the rails of said rearward section.

5. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, a signal for indicating occupancy of said forward section, said signal including a lamp, a track circuit for the forward section comprising means for supplying energy to the section rails at the exit end of the section and a track relay receiving energy from the section rails adjacent the entrance end thereof, means operative when said track relay is deenergized to establish the circuit of said signal lamp, a lightout relay connected in series with said signal lamp, means governed by said lightout relay and operative only when said relay is picked up to supply coded energy to the rails of said rearward section, and trailic governing means responsive only to the flow of coded energy in the rails of said rearward section to provide a proceed indication, whereby said means will operate to provide a proceed indication when the forward section is occupied only if said signal lamp is lighted.

6. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, a signal for indicating occupancy of saidforward section, said signal including a lamp, a track circuit for the forward section comprising means for-supplying relay receiving energy from the section rails adjacent the exit end of the section, an auxiliary relay associated with said code following track relay, means operativewhen and only when said track relay is responding to coded energy to en- 7. In a coded railway signaling system, in com-" bination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, a signal for said forward section having a plurality of lamps for indicating different degrees of trafiic restriction and including a first lamp providing a clear indication, a second lamp providing a caution indication and a third lamp providing a stop indication, indication means selectively responsive to the flow of different types of coded energy in the rails of the rearward section, means governed by traflic conditions in said forward section and in the adjoining section in advance for establishing circuits to light the first or the second lamp of said signal and to supply to the rails of the rearward section energy of a character effective to condition said indication means to display its least restrictive aspect, means responsive to flow of current in the circuit of the first lamp and operative on failure of flow of current therein to establish a circuit to light the second lamp, means responsive to the flow of current in the circuit of the second lamp and operative on failure of flow of current therein to establish a circuit to light the third lamp and to change the coded energy supplied to the rails of the section in the rear to a character effective to condition said indication means to display a restrictive aspect, means governed by traffic conditions in said forward section for establishing a circuit to also light said third lamp of said signal and to also supply to the rails of the rearward section coded energy of a character effective to condition said indication means to display said restrictive indication, and means responsive to the flow of current in the circuit of the third lamp and operative on failure of flow of current therein to change the energy supplied to the rails of the section in the rear to a character effective to condition said indication means to display its most restrictive indication.

8. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, a signal for said forward section having a plurality of lamps and including a first lamp providing a clear indication, 2. second lamp providing a caution indication and a third lamp providing a stop indication, indication means responsive to flow of coded energy of a first character in the rails of the rearward section to provide a clear indication and to flow of coded energy of a second character -to' provide a caution indication, means governed by trafiic conditions in said forward section and in the adjoining section in advance for establishing circuits to light the first or the second lamp of said signal and to establish a circuit to supply coded energy of said first character to the rails of said rearward section, means responsive to flow of current in the circuit of the first lamp and operative on failure of flow of current in said circuit to establish a circuit to light the second lamp, means responsive to the flow of energy in the circuit of the second lamp and operative on failure of flow of current in said circuit to establish a circuit to light the third lamp and to change the energy supplied to the section in the rear from coded energy of the first character to coded energy of the second character, means responsive to traffic conditions in said forward section for establishing a-circuit to light the third lamp and to establish a circuit to supply coded energy of said second character to the-rails of said rearward section, and means responsive to flow of current in the circuit of said third lamp and operative on failure of flow of current in said circuit to interrupt the supply of coded energy of said second character to the rails of said rearward section.

9. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided into a plurality of successive track sections including a forward and a rearward section, a signal for said section having a plurality of lamps and including a first lamp providing a clear indication, a second lamp providing a caution indication, and a thirdxlamp providing a stop indication, indication means responsive to flow of coded current in the rails of said rearward section, said. means being operative on fiow of coded energy of a first character to provide a ,clear indication and being operative on flow of coded energy .of asecond character to provide a caution indication, means operable when said forward section and the adjacentsection in advance thereof are both vacant to establish a circuit for the first lamp. including in series therewith a first lightout relay andtoalso establish a circuit for supplying .coded energy of said first character to the railsof said'rearward section, means operable when said forward section and the adjacent sectionin advance are both vacant and the first lightout relay is released to establish a circuit for the second lamp of said signal, means operable when said :forward section is vacant and the adjacent sectionin advance thereof is occupied to establish a circuit for said second lamp of said signalincluding in series therewith a second lightout relay and to also establish a circuit including a front contact of said second lightout relay for supplying coded energy of said first character to the rails .of said rearward section, means operable when said forward section is vacant and the adjacent section in advance is occupied and the second lightout relay is released to establish a circuit for-the third lamp of said signal and to alsoqestablish a circuit to supply coded energy of said second character to the rails of said rearward section, means operable when said forward section is cocupied to establish a circuit for the third lamp of said signal including in series'therewith a third lightout relay and to also establish a circuit including a front contact. of said third lightout relay for supplying coded energy of said second character to the rails of said rearward section.

10. In a coded railway signaling system, in combination, a stretch of railway track havinga pair of track rails dividedby insulated joints into a plurality of successive track sections including a first, a second and a thirdsection, a signal for and being operable on flow of coded energy of a .second character to provide a caution indication,

effective to produce a proceed indication will not,

"the second section having a lamp .and having mechanism for conditioning the signal when lighted to display a clear, a caution or a stop'indication, means for establishing a circuit for said lamp including in series therewith a lightout re lay, indication means responsive to fiow of coded current in the rails of said third section, said means being operable on fiow of coded energy of a first character to provide a clear indication means operable when said first and second sections are vacant to cause said mechanism. to

condition saidsignal to display its clear indicate tion and to establish a circuit to supply coded215 energy of said first character to the rails of said third section, means operable when said first section is occupied and said second section is vacant to cause said mechanism to condition the signal to display its caution indication and to establishpg a circuit including a front contact of said lightout relay for supplying coded energy of said first character to the rails of said third section, means operable when said first section is occupied and thesecond section is vacant. and said lightout re- Z25 lay is released to establish a circuit for supplying coded energy of said second character to the rails of said third section, and means operable w-hensaid second section is occupied to cause said mechanism to condition the signal to display its g stop indication and to establish a circuit including a-front contact of vsaid lightout relay for supplying coded energy of said second character to the rails of said third section, whereby energy be supplied to the rails of the third section when a the second section is occupied and said signal lamp is defective.

11. In a coded railway signaling system, in combination, a stretch .of railway track havingggm a pair of track rails divided by insulated joints into a plurality of successive sections including a first, a second and a third section, a signal for the second section having a lamp and having mechanism for conditioning the signal when lighted to display a clear, a caution or a stop indication, an approach relay having a contact closed when said third section is occupied and operable when said contact is closed to establish a circuit for said lamp including in series there- 50 with a lightout relay, indication means responsive to flow of coded current in the rails of said third section, said means being operable on flow of coded energy of a first character to provide a clear indication and being operable on flow of coded energy of a second characterto provide a caution indication, means operable when said first and second sections are vacant. and the third section is occupied to cause said mechanism to condition said signal to display its clear indication and to establish, a circuit to supply coded energy of said first character to the rails of said third section, means operable when said first section is. occupied and the second section is vacant and the third section is occupied to cause said mechanism to condition said signal to display its caution indication and to establish a circuit to supply coded energy of said first character .to the rails of said third section if the lightout relay is picked up and to supply coded 70 energy of said second character to the rails of said third. section if said lightout relay is released, and means operable when the second and third sections are occupied to cause said mechanism to condition said signal to display its stop indication and to establish a circuit to supply coded energy of said second'character to the rails of said third section if said lightout'relay is picked up and to cut off the supply of coded energy to the rails of said third section if said lightout relay is released.

12. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections, a signal for each section capable of displaying a plurality of different indications including a stop, a caution and a clear indication, each signal I including a lamp, each lamp having a lightout relay associated therewith, an energizing circuit for each lightout relay including in series therewith the associated signal lamp, a track relay for each section receiving energy over the rails of such section, each track relay having associated therewith a first decoding means including a first auxiliary relay which is picked up when the track relay is responding to coded energy and a second decoding means including a second auxiliary relay which is picked up when and only when the track relay is responding to energy of the second code frequency, each such first auxiliary relay being operative when released to condition the associated signal to display its stop indication and when picked up to condition the signal to display a proceed indication, each such second auxiliary relay being operative when released provided the associated first auxiliary relay is picked up to condition the associated signal to display its caution indication and being operative when picked up provided the associated first auxiliary relay is also picked up to condition the associated signal to display its clear indication, and means governed by each first auxiliary relay and the associated lightout relay for supplying energy to the rails of the adjacent track section in the rear, each such means being operative when said first auxiliary relay is picked up provided the lightout relay is also picked up to supply coded energy of the second code frequency to the rails of said section and being operative when said first auxiliary relay is picked up and the associated lightout relay is released to supply coded energy of the first code frequency to the rails of said section, said means being also operative when the first auxiliary relay is released to supply coded energy of the first code frequency to the rails of said section.

13. In a coded railway signaling system, in combination, a stretch railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, a signal for the forward section including a lamp which becomes lighted to cause the signal to display an indication, a track relay for the forward section receiving energy over the rails of said section, means for at times supplying energy of a first code frequency and at other timessupplying energy of a second code frequency to the rails of said forward section, a first decoding means associated with said track relay and including a first auxiliary relay which is picked up when the track relay is responding to coded energy and a second decoding means including a second auxiliary relay which is picked up when the circuit of said decoding means is'established and the track relay is responding to energy of the second code frequency, said first auxiliary relay being operative when released to condition-the signal when lighted to display a stop indication and 'to effect. the supply of energy of the first code frequency to the rails of said rearward section and being. operative when picked up to condition said signal to display a proceed indication and to effect the supply of energy of the second code frequency to the rails of the'rearward section, said second auxiliary relay being operative when released provided the first auxiliary relay is picked up to condition the signal to display its caution indication and when picked up provided thefirst auxiliary relay is also picked up to con dition the signal to display its clear indication, indication means for said rearward section responsive to flow of coded-energy in the rails of said section, an approach relay which is released when the rearward section is occupied, a slow releasing repeater relay energized when said ap proachrelay is picked: up, a lightout relay connectedin series with the lamp of the signal for said forward section, a circuit including a front contact of said repeater relay and a back contact of said approach relay'for energizing said second decoding means, a circuit including back contacts of said approach relay and said repeater relay for energizing said signal lamp and said lightout relay, and a circuit including a front contact. of said lightout relay for also energizing said second decoding means.

14. In a coded railway signaling system, in 0 combination, a stretch of railway track having a pair of track rails divided 'by' insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy -to the rails of saidi forward section, a code following track relay having a winding receiving energy over' the rails of said forward section, an auxiliary relay associated' with said track relay, means responsive to code following operation of said track relay for supplying energy to said auxiliary relay, a signal governing traflic in said forward section, said signal including a lamp, a lightout relay, a circuit including said lamp in series therewith for energizing said lightout relay, means governed by -said auxiliary relay and said lightout relay for supplying coded energy to the rails of said rearward section, said means being operative when said auxiliary relay is picked up provided the lightout relay is also picked up to supply coded energy of a' first character to the rails of said rearward section and being operative when said auxiliary relay is picked up and the lightout relay is released to supply coded energy of a second character to the rails of said rearward sec-' tion, said means being also operative to supply coded energy of said second character to the rails of said rearward section when said auxiliary relay is released, and traflic governing means selectively responsive to the flow of coded energy of said first and second characters in the rails of said rearward section, said means being operative in response to flow of coded energy of the first character to provide a first proceed indication and being operative in response to flow of coded having a, winding receiving energy over the rails of said forward section, an auxiliary relay associated with said track relay, means responsive to code following operation of said track relay for supplying energy to said auxiliary relay, a signal governing traflic in said forward section, said signal including a lamp, a lightout relay, a circuit including said lamp in series therewith for energizing said lightout relay, means governed by said auxiliary relay and said lightout relay for supplying coded energy to the rails of said rearward section, said means being operative when said auxiliary relay is picked up provided the lightout relay is also picked up to supply coded energy of a first character to the rails of said rearward section and being operative when said auxiliary relay is picked up and the lightout relay is released to supply coded energy of a second character to the rails of said rearward section, said means being also operative to supply coded energy of said second character to the rails of said rearward section when said auxiliary relay is released and said lightout relay is picked up and being operative to prevent the supplyof coded energy of either character to the rails of said rearward section when said auxiliary relay and lightout relay are .both released, and traflic governing means selectively responsive to the flow of coded energy in the rails of said rearward section, said means being operative in response to flow of coded energy of the first character to provide a first proceed indication and being operative in response to flow of coded energy of the second character to provide a restrictive proceed indication and being operative in response to the absence of flow of coded energy to provide the most restrictive indication.

16 In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections includinga forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, an auxiliary relay associated with said track relay, means responsive to code following operation of said track relay for supplying energy to said auxiliary relay, a signal governing traflic in said forward section, said signal including a lamp, a lightout relay, an approach relay governed by traffic conditions in said rearward section, said approach relay being energized when said rearward section is vacant and being effective when deenergized to establish a circuit including said lamp and said lightout relay in series, a circuit including front contacts of the approach relay and of the auxiliary relay for supplying coded energy to the rails of the rearward section when the approach relay is energized provided the auxiliary relay is also energized, and a circuit including front contacts of the auxiliary relay and of the lightout relay for also supplying coded energy to the rails of the rearward section when the approach relay is released provided the auxiliary relay'and the lightout relay are both energized.

RALPH R. KEMMERER.

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