US2335151A - Railway signaling system - Google Patents

Description

Nov. 23, 1943.

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2 Ba 1 fiy H was a 5 5% u .QQNN $3 5% kg QQN Patented Nov. 23, 1943 7 2,335,151 RAILWAY SIGNALING SYSTEM Ralph E.

The Union Kemmerer, Swissvale, Pa., assignor to Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application July 30, 1942,

Serial No. 452,893

14 Claims. (01. 246-38) My invention relates to railway signaling systems of the type employing wayside signals of the searchlight type.

In some systems where more than two proceed indications are desired the wayside signals employ upper and lower units each comprising a searchlight signal unit. These signal units cooperate to provide the various indications. However, only certain combinations of aspects of the two signal units are authorized. It is desired to check response of the signals to determine if they are displaying the proper aspects, and to govern the supply of signal control energy to the adjacent section in the rear so that if a signal is displaying an unauthorized indication the adjacent signal in the rear will be prevented from displaying its least restrictive indication.

' An object of my invention is to provide an improved railway signaling system of the type employing wayside signals having two Searchlight signal units, the system being arranged so that the signals are checked to determine if they are displaying the proper aspects.

Another object of the invention is to provide a system of the type described and having means governed by the signals and controlling the supply of energy to the adjacent section in the rear.

A further object of the invention is to provide a signaling system of the type described in which one of the signal units controls the supply ergy to the other signal unit to thereby prevent the display of an unauthorized combination of aspects by the two signal units.

Another object of the invention is to provide a system of the type means to delay certain types of changes in the signals to thereby prevent momentary display of incorrect or unecessarily restrictive aspects by the signals.

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

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

In practicing my invention I provide repeater relays to detect response of the signal units to changes in the signal control relays and I employ these repeater relays of energy to the adjacent section in the rear. In some modifications these repeater relays directly control the supply of energy to the section in the rear, and in other modifications the repeater relays control the supply of energy to the section of endescribed and incorporating to control the supply a in the rear through a checking relay which checks correspondence between the signal control and signal repeater relays. In addition, in some modifications the signal repeater relays for the upper signal unit control the supply of energy to the winding of the lower signal unit, while in each of the modifications the lightout relay for the upper unit of a signal controls the polarity of the energy supplied to the lower unit ofthe signal so that energy effective to cause the lower unit of the signal to display a green light cannot be supplied to the winding of this unit if the lamp of the upper unit of the signal is burned out. In some modifications .of the invention the green repeater relay for each signal unit is slow in releasing and when picked up establishes a circuit to supply energy to the winding of the associated signal unit to delay changes in'this signal unit until the signal control relays respond to changes in traific conditions and thus prevent the momentary display of unnecessarily restrictive indications.

In the drawings Figs. 1 and 3 are diagrams of systems embody-' ing my invention and having wayside signals arranged to provide four aspects, and I Figs. 2 and 4 are diagrams of signaling systems also embodying my invention and having wayside signals arranged to provide five aspects.

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

Referring to Fig. 1 of the drawings there is shown therein a stretch of railroad 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 are separated by insulated joints 3 into the customary successive track sections, and the rails of each of these sections form a part of a track circuit of the usual character.

The system shown employs alternating current energy in the track circuits. This energy may be derived from any suitable source and may be distributed throughout the track stretch by a transmission line, not shown. In the drawings the termnals of the power supply source are designated BX and CK.

In the diagram forming Fig. 1 of the drawings one complete track section, designated IZT, and parts of two adjoining sections HT and I31, are shown. Each of these section has located at the entrance end thereof a with an appropriate prefix, for governing trafiic in the track' stretch. Each of these signals has an upper unit SU, and a lower unit SL, each comsignal designated S l prising a familiar searchlight signal unit. Each the rectifier HR to track relay IZTR and proof these signals is provided with a mechanism duces code following operation of this relay with capable of selectively projecting a plurality of the result that the two portions of the decoding beams of light of different colors from a single transformer primary winding are alternately enlight source. The construction of the signal 5 ergized and energy is induced in the transformer units is not a part of this invention and these secondary windings.

units may be of any well known construction. Energy from one of these windings is rectified A signal unit of the type which I may employ is by a contact of the track relay and is supplied shown in Letters Patent of the United States No. to relay l2I-I, while energy from the other transl,864,224, granted June 21, 1932, to Wesley B. former secondary winding is supplied through Wells. resonant rectifier unit lfiilDU to relay IZJ.

The signaling system shown in Fig. 1 is of the As the relays IZH and EN are picked u enfour indication variety and makes use of track ergy of normal polarity is supplied to the windcircuit energy coded at three different frequen.-- ing of signal I2SU over the circuit which is cies. This coded energy is provided by code transtraced from terminal B through front contact conditions ahead. In the illustrative form nal .0. Accordingly, the signal mechanism conshown, each code transmitter CT is provided with ditions the signal to provide its green indication,

three circuit making and breaking contacts 75, while the contact G of the signal is closed so that 120 and 180 which are continuously actuated by energy is supplied to the relay EZUG and its cona motor or other suitable mechanism at three diftacts are picked up so that its contact interferent speeds. For purposes of illustration it will rupts the circuit of the winding of signal lZSL.

' be assumed that these speeds are such as to pro- 25 At this time, as signal IZSU is displaying its green vide 75, 120 and 180 energy pulses per minute indication, relay lZUY is released and its contacts which are separated by periods of equal duration 27 and 28 additionally interrupt the circuit of in which no energy is supplied. the winding of signal IZSL. Accordingly, the Each of the track sections includes a code folsignal IZSL displays its red indication so the si lowing track relay designated TR together with 30 nal I28 displays its clear indication consisting an appropriate prefix. The track relay is located of a green light over a red light. at the entrance end of the track section and may As relays H and l UG are picked up, ener y be of any suitable type. As shown, the track of 180 code frequency is supplied to track transrelay I 2TR is of the direct current type and is former HTT over the circuit which is traced connected to the track rails through a suitable '35 from terminal BX through contact 180 of code rectifier I 2R. The track relay IZTR has assotransmitter I ZCT, front contact 3!! of relay IZUG, ciated therewith a decoding transformer ILZDT, front contact 3| of relay IZH, and prima y Wi dsignal control relays 42H, NJ and I 2K, signal reing of transformer l ITT to terminal CX. Acpeater relays I 2UG, I 2UY and IZLG, and a cordingly, energy of 180 code frequency is suplightout relay IZULO. plied to the rails of section HT and the signal The relays IN and 12K are energized from the for this section displays its clear indication.

, capacitance which are arranged and propor- 45 out relay IZULO so that this relay is picked up tioned so that when the frequency of the current as long as the lamp filament is intact.

supplied thereto is that present when the track When a train moving in the normal direction relay is responding to energy of a particular code of trailic enters section IZT, the track relay iZ'I'R frequency suflicient energy is supplied through is shunted and relays 121-1 and l2J release. On the unit to pick up the associated relay. Each release of relay IZH its contacts 20 and 23 inunit is also arranged so that when energy of a terrupt the supply of energy to the winding of sociated relay U0 p ck up its contacts Each of IZH are released energy cannot be supplied to these units includes a rectifier which rectifies signal I2SL so it continues to display its red the energy supplied through the unit. indication. Accordingly, signal lZS displays its The elements of the unit I ZODU are proporstop indication consisting of a red light over a tioned so that the 1elay'l2K is picked up when a red light. a

the track relay is responding to ener y of 120 When the signal IZSU displays its red indicacode frequency, while the elements of the unit tion its contact G interrupts the circuit of the lBllDU are proportioned so that the relay IZJ relay I ZUG, while at this time the circuit of this is picked up when the track relay is responding relay is additionally interrupted by contact 33 .r

to energy of 180 code frequency. of relay IZJ.

Each of the signals has associated therewith On release of relay l2H its contact 3| interasource of direct current, such as a storage 'batrupts the supply of energy of 180 code fretery, not shown, the terminals of which are desigquency to the transformer HTT and establishes nated B and C. the circuit for supplying energy of code fre- The equipment is shown in the condition which quency thereto. it assumes when the trackstretch is vacant. At When the train advances into section I3T the this time, energy of code frequency is sup- 70 signal for that section is caused-to display its which supplies energy to the track transformer feeds to relay I ZIR and the relay causes energy I HTT for section HT, This energy feeds through 7 5 to be supplied through the decoding transformer.

assar |2DT to the relay |2H so that its contacts are picked up. The rate of operation of the track relay |2TR on '75 code is such that energy is not supplied through the units |80DU and |20DU and the relays |2J and |2K remain released.

When relay |2H picks up, its contacts 2|) and 23 establish a circuit to supply energy of reverse polarity to the winding of signal |2SU. This circuit is traced from terminal B through front contact 20 of relay IZI-I, back contact 34 of relay HUG, back contact 22 of relay |2J, winding of signal |2S back contact 2| of relay |2J, back contact 35 of relay IZUG, and front contact 23 of relay |2H to terminal C. This energy causes the signal mechanism to condition the signal to display its yellow indication, while the front contact Y of the signal'is closed to establish the circuit to supply energy to the relay |2UY and contacts 21 and 28 of this relay are picked up. However, at this time the contacts of relays |2LG and |2K are released so the circuit of the winding of signal |2SL is interrupted and this signal continues to display its red indication. Accordingly, the signal |2S now displays its approach indication consisting of a yellow light over a red light.

On picking up of the contacts of relay IZH its contact 3| interrupts the supply of energy of 7 code frequency to section HT and establishes the circuit to supply energy of 120 code frequency thereto. This circuit is completed on picking up of relay |2UY and is traced from terminal BX through contact I of code transmitter |2CT, front contact 31 of relay IZUY, back contact 38 of relay |2LG, back contact 30 of relay IZUG, front contact 3| of relay |2H, and primary winding of transformer ||TT to terminal CX. It will be seen that the circuit for supplying energy of 120 code frequency to section ||T includes contacts of the signal repeater relays |2LG and |2UG so that this circuit will not be established if the lower signal |2SL should improperly display its green indication or the upper signal |2SU should improperly display its green indication.

When the train advances far enough to vacate section |3T the signal for that section is conditioned to display its approach indication, while energy of 120 code frequency is supplied to the rails of section |2T. This energy feeds to relay |ZTR and operates it at a rate such that energy is supplied through the unit |20DU and picks up the relay |2K so that its contacts 4|] and 4| establish the circuit to supply energy of normal polarity to the winding cuit for supplying energy to signal |2SL is traced from terminal B through front contact 20 of relay IZH, back contact of relay IZUG, front contact 42 of relay I2ULO, front contact 40 of relay IZK, front contact 21 of relay |2UY, winding of signal |2SL, front contact 28 of relay IZUY, front contact 4| of relay IZK, front contact 43 of relay H.710, and front contact 23 of relay |2H to terminal C. The energy of normal polarity supplied to signal |2SL causes the signal mechanism to condition the signal to provide its green indication so that the signal |2S displays its approach medium indication consisting of a yellow light over a green light.

It will be seen that the circuit for supplying energy of normal polarity to the winding of signal |2SL includes front contacts 42 and 43 of lightout relay IZULO. If the lamp of the upper signal is burned out, the contacts of relay |2ULO will be released and will cause the energy supplied of signal I2SL. The cirof code frequency is to the winding of signal |2SL to be of reverse polarity so that the signal mechanism will condition the signal to provide a yellow instead of a green light. This arrangement prevents the lower signal unit |2SL from displaying a green light when the lamp of the upper signal unit IZSU is burned out. This prevents the display of a single green light by a signal when the lamp of the upper signal unit is burned out, and causes a single yellow light to be displayed at such times. The single green light might be interpreted as a clear indication when the signal is intended to display its approach medium indication, while the single yellow light will be interpreted as a more restrictive indication than that intended to be displayed by the signal.

When the mechanism of signal |2SL responds to energization of the signal winding by current of normal polarity, front contact G of the signal is closed and establishes the circuit to supply energy to the relay IZLG so that contact 38 of this relay picks up and interrupts the supply of energy of 120 code frequency to transformer ||TT and establishes a circuit to supply energy of code frequency thereto. This circuit is traced from terminal BX through contact I86 of the code transmitter, front contact 38 of relay |2LG, back contact 38 of relay |2UG, front contact 3| of relay IZH, and primary winding of transformer ||TT to terminal CX. The energy of 180 code frequency supplied to the rails of section IT causes the signal for that section to provide its clear indication.

If the lamp of the upper signal unit is burned out so relay IEULO is released and signal IZSL displays its yellow indication, relay |2LG will not be energized and its contact 38 will not establish the circuit for supplying energy of 180 code frequency to section HT, but will maintain the circuit for supplying energy of 120 code frequency thereto. Accordingly, the signal for section T will not provide its clear indication but" will display its approach medium indication, and a following train will receive a restrictive indication before it reaches the signal |2S at a time when that signal is displaying a single yellow light.

When the train under consideration vacates the section in advance of section |3T energy supplied to the rails of section |3T and the signal |3S displays its approach medium indication, while energy of 180 code frequency is supplied to the rails of section |2T. This energy feeds to the track relay |2TR and operates it at a rate such that energy is no longer supplied through unit IZQDU to relay IZK but is supplied through unit IBGDU to relay |2J.

When relay |2J picks up, its contacts 2| and 22 interrupt the previously traced circuit for supplying energy of reverse pdlarity to the winding of signal |2SU and establish the circuit for supplying energy of normal polarity thereto, while contact 33 of relay |2J establishes the circuit for relay |2UG so that energy is supplied to this relay over the circuit which includes front contact G of the signal. When relay IZUG picks up, its contact 25 interrupts the circuit oi signal IZSL and this signal displays a red light, while contact 30 of the relay IZUG interrupts one circuit for supplying energy of 180 code frequency to section HT and establishes another circuit for supplying energy of 180 code frequency thereto.

When the energy supplied to section |2T is changed from 120 to 180 code frequency the re lay IZK releases and the relay lZJ picks up. The relay IZK may release before the signal IZSU responds to picking up of relay IZJ, and this system is arranged to prevent an undesirable flash of the approach indication at such times.

When energy of 120 code frequency is supplied to section I2T the relays 1 2H and IZK are picked up while the relay I2J is released so that energy of normal polarity is supplied to the winding of signal I2SL over the circuit which is traced from terminal B through front contact 29 of relay lZI-I, back contact 25 of relay lZUG, front contact 42 of relay I2ULO, front contact 40 of relay IZK, front contact 27 of relay IZUY, winding of signal I ZSL, front contact 28 of relay IZUY, front contact 4! of relay IZK, front contact 43 of relay lEULO, and front contact 23 of relay IZH to terminal C. Accordingly, the contact G of the signal is closed so energy is supplied to relay IZLG and its contacts are picked up.

On interruption of the supply of energy of 120 code frequency to section [2T the relay IZK releases and interrupts the circuit just traced for supplying energy to the winding of signal IZSL. However, on release of relay tinues to be supplied to the signal IZSL over the circuit which includes front contacts 46 andv 4'! of relay IZLG and back contacts 40 and 4| of relay IZK. The relay IZLG is of a type the contacts of which are slow to release and they remain picked up for a period longer than is required for the contacts of relay l2J to pick up. Accordingly, after release of relay lZK the contacts of relay I2LG maintain the supply of energy to the winding of signal IZSL until the relay IZUG picks up and its contact 25 interrupts the circuit of the signal I2SL. When the relay IZJ picks up it changes the polarity of the energy supplied to the winding of signal IZSU from reverse to normal so this signal displays a green light, while energy is supplied to relay IZUG so that it picks up and cuts off the supply of energy to signal IESL so this signal provides a red light.

If on release of relay |2K prior to picking up of relay |2J the supply of energy to signal iIZSL were interrupted, this signal would display a red light, while the upper signal IZSU still displays a yellow light so the signal I28 would momentarily display its approach indication consisting of a yellow light over a red light. The arrangement provided by this invention by which the slow releasing relay iZLG maintains the supply of energy to signal lZSL after release of relay IZK and prior to picking up of relay IEUG prevents the momentary display of the approach indication by the signal on a change from 1-20 to 180 code frequency and insures that the display of the approach medium indication will be maintained until the change to the clear indication occurs.

The system of this invention is arranged so that when a train moving in the reverse direction of trafiic passes through the track stretch the signals will not momentarily display indications more restrictive than are required by trafiic conditions.

When such a train enters the section in advance of section IZiT the energy supplied to section IZ'I' is changed from 180 code frequency to 120 code frequency and relay I 2J releases and relay 2K picks up. On release of relay IZJ its contact 33 interrupts the circuit of relay IZUG, but this relay is of a type which is slow in releas- I2K, energy coning so that its contacts remain picked up for a period subsequent to release of the contacts of relay IZJ. In addition, on release of the contacts of relay lZJ its contacts 2! and 22 interrupt one circuit for supplying energy of normal polarity to the winding of signal I ZSU, but energy of normal polarity continues to be supplied thereto over the circuit including front contacts 34 and 35 of relay IZUG and back contacts 2! and 22 of relay IZJ.

On picking up of relay [2K its front contacts 40 and 4| are closed to permit'energy. to be supplied to the winding of signal I ESL when the contacts of relay I EUY are picked up.

After a short time interval, contacts 34 and 35 of relay I 2UG release and interrupt the supply of energy of normal polarity to the winding of signal IZSU and establish the circuit to supply mechanism conditions the signal to display a yellow light, while front contact Y of the signal is closed so energy is supplied to relay I2U'Y. On the supply of energy to relay IZUY its contacts 27 and 28 pick up and complete the supplying energy pick up. I When the relay IZUG releases, its contact 33 code frequency to section H T, while on picking up of relay IZUY 31 establishes the circuit including back contact 38 of relay IZLG, back contact 30 of relay IZUG, and front contact 31 of relay I 2H for supplying energy of code frequency to section HT. As soon as the signal IZSL displays its green light and relay I ZLG picks up, contact 38 of relay EZLG interrupts the circuit for supplying energy of 120 code frequency to section HT and establishes a circuit for supplying energy of code frequency thereto. It will be seen, therefore, that in the timeinterval between the release of relay IZUG and picking up of relay IELG, the supply of energy of 180 code frequency to section HT is cut oil", while energy of 120 code frequency is supplied to section HT during this time. On interruption of the supply of energy of 180 code frequency to section HT the relay IiJ, not shown, for that section releases, but the relay HUG, not shown, is slow enough in releasing to maintain the suprestrictive indication thereby.

The equipment operates in a similar manner on a change from the approach medium to the I ZLG, like the relay IZUG, is of tacts of which are slow to release, and its contacts remain picked up and maintain the circuit for supplying energy to the winding of signal |2SL for a period subsequent to release of the contacts of relay I2K. After a short time interval the relay |2LG releases and its contacts 46 and 41 interrupt the supply of energy to the winding of signal IZSL, while its contact 38 interrupts the supply of energy of 180 code frequency to section HT and establishes the circuit to supply energy of 120 code frequency thereto.. On release of the relay |2LG and interruption of the supply of energy to the winding of signal |2SL the mechanism of this signal conditions the unit to provide its red light 50 signal |2S now displaysits approach indication consisting of a yellow light over a red light.

When the train under consideration enters section |2T relay IZH releases and its contacts 20 and 23 interrupt the supply of energy to the winding of signal IZSU, so this signal displays a red light, while contact 3| of relay |2H interrupts the supply of energy of 120 code frequency to section |T and establishes the circuit to supply energy of '75 code frequency thereto. The signal |2S now displays its stop indication consisting of a red light over a red light.

From the foregoing it will be seen thatthe system provided by this invention is arranged so that changes in the signals either to a less restrictive indication or to a more restrictive indication occur without objectionable displays of other indications. Furthermore, it will be seen that this system is arranged so that the supply of coded energy to the section in the rear of a signal is governed by the signal repeater relays so that changes in this energy occur only when the signals respond to a change in the signal control relays. i

Construction and operation of system shown in Fig. 2

In Fig. 2 of the drawings there is shown a modification of my invention adapted for use with signals arranged to provide five aspects. Except as hereinafter pointed out in detail, the system of Fig. 2 is the same as that shown in Fig. 1. This modification makes use of a special form of energy, designated 75M code frequency, to provide an additional proceed aspect. This 75M code may be the usual '75 code to which a distinguishing periodic characteristic which recurs every three cycles, for example, has been added. Suitable decoding means designated 75M decoding unit is provided to detect the presence of this code. The details of this decoding means are not essential for an understanding of this invention and any appropriate means may be employed for this purpose. One such means is shown in application Serial No. 452,902 .of Carl Volz filed July 30, 1942, for Code detecting means. This decoding means controls the relay IZHB in such manner that the relay IZHB is energized when and only when the track relay is responding to energy of 75M code frequency.

This modification further differs from that shown in Fig. 1 in that a relay |2LY is provided which is energized when lower signal |2SL is displaying a yellow light.

The equipment is shown in the condition which it assumes when the track stretch is vacant. At this time, venergy of 180 code frequency is supplied to the transformer |2TT and feeds to the track relay IZTR so that energy is supplied through the decoding transformer |ZDT to relay |2HA and to relay |2J through the resonant rectifier unit |DU. Accordingly, energy of normal polarity is supplied to the winding of signal IZSU over the circuit whichis traced from terminal B through front contact 20 of relay IZHA, front contact 2| of relay |2J, winding of signal |2SU, front contact 22 of relay |2J, and front contact 23 of relay |2HA to terminal C. The signal IZSU, therefore, displays its green light, while its contact G is closed to establish the circuit of relay IZUG so that contact 25 of relay |2UG is picked up and interrupts the circuit of the winding of signal IZSL. The signal |2SL, therefore, displays a red light while the signal |2S displays its clear indication consisting of a green light over a red light.

At this time, energy of code frequency is supplied to transformer ||TT over the circuit which is traced from terminal BX through contact I80 of the code transmitter I2CT, front contact 30 of relay IZUG, front contact 3| of relay I2HA, and primary winding of transformer HTT to terminal CX.

When a train moving in the normal direction of traffic enters section |2T the track relay IZTR ceases to follow code and relays |2HA and |2J release. On release of relay |2HA its contacts 20 and 23 interrupt the supply of energy to the windingof signal |2SU so this signal displays a red light, while contact 3| of relay |2HA interrupts the supply of energy of 180 code frequency to transformer ||TT and establishes the circuit to supply energy of 75 code frequency thereto. At this time, relay |2UG releases.

When the train'enters section |3T the equipment for that section operates to cause signal I3S to display its stop indication, while energy of 75 code frequency is supplied to the transformer IZTT. i

When the train vacates section |2T this energy feeds to relay IZTR which causes energy to be supplied through the decoding transformer |2DT to relay IZHA, but not to the other signal control relays. On picking up of relay contact 3| interrupts the supply of energy of '75 code frequency to section HT, while energy of reverse polarity is supplied to the winding of signal IZSU over the circuit which includes front contacts 20 and 23 of relay IZI-IA, back contacts 34 and 35 of relay IZUG, and back contacts 2| and 22 of relay |2J. Accordingly, the signal |2SU now displays a yellow light, while contact Y of the signal establishes the circuit of relay IZUY with the result that this relay picks up and its contact 31 establishes the circuit for supplying energy of 75M code frequency to section MT. The circuit for supplying energy of 75M code frequency to section IT is traced from terminal BX through contact 75M of the code transmitter IZCT, back contact 49 of relay I2LY, front contact 3'1 of relay I2UY, back contact 38 of relay IZLG, back contact 30 of relay IZUG, front contact 3| of relay IZI-IA, and primary winding of transformer IT to terminal CX.

At this time the upper unit |2SU of signal |2S displays a yellow light while the lower unit |2SL of the signal continues to display a red light. The signal |2S, therefore, displays its approach indication consisting of a yellow light over a red light.

When the train vacatessection |3T, energy of 75 code frequency is supplied to the track relay for that section so that signal |3S displays its approach indication, while energy of 75M code frequency is supplied to section l2T. When this IZHA its energy is supplied to the track relay I2TR, energy continues to be supplied through the decoding transformer I 2DT to relay IZHA, while energy is also supplied through the 75M decoding unit to the relay I ZHB. On picking up of the relay ZHB, energy of reverse polarity is supplied to the Winding of signal I ZSL over the circuit which is traced from terminal B thrOugh front contact of relay IZHA, back contact of relay IZUG, front contact of relay IZHB, back contact 41 of relay IZLG, back contact 4| of relay IZK, front contact 28 of relay IEUY, winding of signal IZSL, front contact 27 of relay IZUY, back contact 40 of relay I 2K, back contact 46 of relay IZLG, front contact 5| of relay IZHB, and front contact 23 of relay |2HA to terminal C. Accordingly, the signal unit |2SL displays a yellow light so the signal I 28 displays its advance approach indication consisting of a yellow light over a yellow light. In addition, contact Y of signal |2SL establishes the circuit of relay |2LY and its contact 49 picks up to interrupt the supply of energy of 75M code frequency to section I IT and cause energy of 120 code frequency to be supplied thereto.

When the train vacates the section in advance of section |3T, energy of 75M code frequency is supplied to the rails of section I3T, and the equipment for that section causes energy of 120 code frequency to be supplied to section |2T. When this energy is supplied to the track relay IZTR, energy is no longer supplied through the 75M decoding unit to relay I2HB, but energy is now supplied through the resonant unit IZUDU to relay IZK.

On picking up of relay IZK its contacts 40 and 4| interrupt the circuit for supplying energy of reverse polarity to signal IZSL and establish the circuit traced in connection with the system shown in Fig. 1 for supplying energy of normal polarity to the signal IZSL. The signal unit IZSL now displays a green light so signal |2S displays its approach medium indication consisting of a yellow light over a green light. At this time, contact Y of signal IZSL is opened while contact G is closed and establishes the circuit to supply energy to relay IZLG. When relay IZLG picks up, its contact 38 interrupts the supply of energy of 120 code frequency to section I IT and establishes a circuit to supply energy of 180 code frequency thereto.

' When the train vacates the second section in advance of section I3T, energy of 180 code frequency is supplied to section |2T with the result that relay I 2K releases and relay |2J picks up. When relay |2J picks up, its contacts 2| and 22 change the energy supplied tosignal I2SU from reverse to normal polarity. Thesignal |2SU now displays a green light, While its contact Y interrupts the circuit of relay IZUY and its contact G establishes the circuit of relay IZUG. Release of relay |2UY interrupts the circuit of signal IZSL, while this circuit is additionally interrupted by contact 25 of relay IZUG. The signal |2S now displays its clear indication comprising a green light over a red light.

This modification operates inthe same manner as that shown in Fig. 1 to prevent an objectionable signal flash on a change in the energy supplied to a section from 120 to 180 code frequency, or from 180 to 120 code frequency and a detailed description thereof is unnecessary.

This modification also operates toprevent an objectionable signal flash on a change from 120 to 75M code. When energy of 120 code is supplied to section I2T, relays IZHA and I-ZK aretacts of relay J the contacts of picked up so energy of reverse polarity is supplied to signal I ZSU and energy of normal polary is supplied to signal IZSL. Accordingly, relays IZLG and |2UY are picked up.

On the change to energy of M code frequency the relay IZK releases and the relay IZHB picks up. The operating characteristics of the 75M decoding means are such, however, that the relay I2HB may not pick up until after the relay |2K releases. On release of relay IZK its contacts 40 and 4| interrupt one circuit for supply ing energy of normal polarity to the winding of signal IZSL, but the supply of energy of this polarity to the signal is maintained over the circuit which includes front contacts 46 and 47 of relay I ZLG, and back contacts 40 and 4| of relay IZK. The signal, therefore, continues to display a green light. When relay IZK releases, its contact 44 interrupts the circuit of relay I2LG, but the relay IZLG is of a type which is slow to release and hence its contacts remain picked up for a period of time. This period is long enough for the relay |2HB to become picked up. Accordingly, on release of the relay |2LG the con- IZHB are pickedup and energy of reverse polarity is supplied to the winding of signal |2SL so that this signal displays a yellow light. If the circuit established by front contacts 46 and 47 of relay IZLG and back contacts 40 and 4| of relay IZK were not provided, the signal unit |2SL would be deenergized in the period between release of relay |2K and picking up of relay I2I-IB and would display a red light so that signal |2S would improperly display its approach indication consisting of a yellow light over a red light. The circuit provided by the back contacts of relay IZK and the front contacts of relay I2LG insures that signal |2SL will continue to display its green light until the circuit for supplying energy of reverse polarity to the signal is established to thereby insure that the signal will change from its green to its yellow aspect without delay.

The system of Fig. 2 is also arranged so that r on a change in the energy supplied to a section from code frequency to 75M code frequency a long display of the approach indication is prevented.

When energy of 180 code frequency is supplied section IZT, relays |2HA and |2J are picked up and energy of normal polarity is supplied to the Winding of the signal I2SU. This signal, therefore, displays a green light, while its contact G establishes the circuit of relay IZUG so that this relay are picked up and its contact 25 interrupts the circuit of signal I ZSL.

On the change in the energy supplied to section |2T from 180 to 75M code frequency the relay |2J releases while the relay I ZHB picks up. On release of relay |2J its contacts 2| and 22 interrupt one circuit for supplying energy of normal polarity to signal I2SU, but they establish the circuit including front contacts 34 and 35 of relay I ZUG for supplying energy of normal polarity to signal IZSU so this signal continues to display its green-light. On release of the relay- |2J its contact 33 interrupts the energizing circuit for relay I ZUG, but because of the slow releasing characteristics of the relay |2UG its contacts remain picked up for a period of timeand maintain the supply of energy to the signal IZSU. The relay IZUG is selected so that its contacts will remain picked up until after the relay |2HB picks up.

Accordingly, on release of relay IZUG therenergy supplied to signal I2SU is changed from normal to reverse polarity, while contact 25 of relay IZUG establishes the circuit to supply energy of reverse polarity to the winding of signal IZSL. The circuit for supplying energy to signal IZSL is complete as soon as signal I2SU responds to the energy of reverse polarity and establishes the circuit of relay IZUY so that its contacts pick up. As a result the signal IZSL will display a yellow light very soon after signal IZSU displays a yellow light, and the signal [2S will dispay its yellow over red or approach indication for only a very short period.

The system shown in Fig. 2, like that shown in Fig. 1, is arranged so that the supply of energy to the section in the rear is controlled by the signal repeater relays so that changes in this energy occur only if the signals respond to opera tion of the signal control relays. Similarly, in this modification, the lightout relay IZULO controls the supply of energy to the winding of the signal l2SL to prevent the display of a green light by this signal when the lamp of the upper signal unit is burned out.

Construction and operation of system shown in Fig. 3

In Fig. 3 there is shown a modified arrangement which I may employ to control four aspect wayside signals. This modification differs from that shown in Fig. 1 in that it employs a checking relay OR to control the supply of energy to the section in the rear. The checking relay GR is controlled by the lightout relay, and by the signal control and signal repeater relays so as to be energized only if the lightout relay is energized, and if the signal control relays and the signal repeater relays are in correspondence. The relay CR, when released, causes energy of '75 code frequency to be supplied to the section in the rear, and prevents the supply of energy of 120 or 180 code to the section in the rear.

The system shown in Fig. 3 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 rails of section HT and track relay [2TB causes energy to be supplied through the decoding transformer I2DT to the relay [2H and through the resonant rectifier unit ISBDU to the relay l2J. As these relays are picked up, energy or normal polarity is supplied to the winding of signal IZSU over the circuit which includes front contacts 20 and 23 of relay [2H and front contacts 2| and 22 of relay I2], and this signal unit displays a green light while its front Contact G establishes the circuit to supply energy to relay I2UG.

At this time, checking relay l2CR is energized over the circuit which is traced from terminal B through front contact 29 of relay 12H, front contact so of relay I2J, back contact 6| of relay IZUY, back contact 62 of relay IZLG, front contact 63 of relay IZUG, front contact 66 of relay IZULO, nad winding of relay i2CR to terminal C.

Energy of 180 code frequency is supplied to the section in the rear over the circuit which is traced from terminal BX through contact 180 of the code transmitter 120T, front contact 66 of relay I2J, front contact 61 of relay I203, front contact 3| of relay 121-1, and primary winding of transformer l ITT to terminal CX.

As the relay [2K is released, its contacts and H interrupt the circuit of signal unit IZSL and it displays a red light, while the signal |2S provides its. clear indication consisting of a green over a red light.

When a train moving in the normal direction of traffic enters section IZT the track relay I2TR is. shunted and energy is no longer supplied through the decoding transformer I2DT to the relays IZH and l2J. On release of relay I2H its contacts 20 and 23 interrupt the supply of energy to :the signal IZSU so that this signal displays its red indication, while its contact G interrupts the circuit of the relay IZUG. In addition, contact 20 and 23 of relay 12H prevent the supply of energy to the winding of signal IZSL, while contact 20 of relay l2I-I interrupts the supply of energy to relay IZCR, and contact 3| of relay [2H interrupts the supply of energy of 180 code frequency to the section in the rear and establishes the circuit for supplying energy of 75 code frequency thereto. As the signals IZSU and I2SL are both deenergized, the signal I2S displays its stop indication consisting of a red light over a red light.

At thi time the circuit of relay IZCR. is interrupted and the contact 61 of this relay is released.

When the train enters section 1.3T the equipment for that section operates to cause signal B8 to display its stop indication and to cause energy of '75 code frequency to be supplied to the transformer IZTT. When the train vacates section I2T this energy feeds to the track relay I2TR and it causes energy to be supplied through the decoding transformer IZDT to relay IZH, but not to relays I2K and IN. When relay 12H picks up, its contacts 20 and 23 establish the circuit including back contacts 2| and 22 of relay-IZJ for supplying energy of reverse polarity to the winding of signal I2SU so this signal displays a yellow light, while its contact Y is closed so that energy is supplied to the relay IZUY and its contacts pick up and establish a circuit to supply energy to the checking relay l2CR. This circuit istraced from terminal B through front contact 20 of relay l2l-I, back contact 60 of relay IZJ, back contact 14 of relay IZK, front contact 13 of relay IZUY, back contact 12 of relay I2LG, back contact 63 of relay IZUG, front contact 64 of relay I2LO, and winding of relay l2CR to terminal C.

When the relay I2H picks up, the back point of contact 3| interrupts the circuit for supplying energy of 75 code frequency to section HT and the front point of this contact establishes another circuit including back contact 61 of relay IZCR for supplying energy of '75 code frequency to section HT. As soon as the signal IZSU displays its yellow aspect and establishes the circult of relay I2UY so that its picks up and establishes the circuit of relay I2CR, the contact 61 of relay I2CR interrupts the supply of energy of '75 code frequency to section HT and establishes the circuit for supplying energy of code frequency thereto. This circuit is traced from terminal BX through contact I22 of the code transmitter l2CT, back contact 16 of relay IZK, back contact 68 of relay I2J, front contact 61 of relay IZCR, front contact 31 of relay I2H, and primary winding of transformer HTT to terminal CX. At this time, therefore, the signal I2S displays its approach indication consisting of a yellow light over a red light, while energy of 120 code frequency is supplied to the section in the rear.

i If for any reason on picking up of the relay IZH the signal I2S fails to respond and to dis- P y its y w light, he Checking elay 'ZCR tion IZT. On the supply of this energy to the will not be energized and will maintain the suprelay iETR, energy continues to be supplied ply of energy of 75 code frequency to the section through the decoding transformer MDT to the in the rear so that a train approaching the sigrelay IZI-I, While energy is now supplied to the relay I2J', but not to the relay lZK.

will receive the most restrictive proceed. indi- On picking up of the relay l2J its contacts 2| cation from the signal for section HT, While if and 22' change the polarity of the energy supplied cab signal apparatus is used, alocomotive present to the winding of signal EZSU from reverse to in section HT will also receive its most restricnormal, and the mechanism of this signal contive proceed indication in the cab. 10 ditions the signal to display a green light, while When the train advances far enough to vacate contact Y of the signal interrupts the circuit of section I3T the equipment for that section oprelay iZUY and contact G of the signal estaberates to cause signal I38 to provide its aplishes the circuit of the relay IZUG. preach indication, while energy of 120 code fre- On release of relay IZK its contacts 76 and H quency is supplied to section I2T. When the interrupt the circuit of the winding of signal IZSL track relay I ZTR responds to energy of I code and this signal displays its red light, While its frequency, energy is supplied through the decontact G interrupts the circuit of relay EZLG. coding transformer I2DT to the relay I2H and On picking up of relay IZJ or release of relay is also supplied through the resonant unit I ZDDU IZK, whichever occurs first, the circuit of relay tothe relay IZK. When the contacts 10 and 1| 20 20R is interrupted, while after the signals comof relay [2K are picked up, energy of normal plete their changes, and the signal repeater reare picked up. On the supply of energy of norfor this relay. The relay I2CR is sufficiently slow releasing to remain picked up during this change in the signals.

G of the signal is closed and energy is supplied On picking up of the relay IZJ its contact 56 On picking up of the relay IZK its contact 16 code frequency to section HT, and establishes interrupts the circuit for supplying energy of anothes circuit for supplying energy of 180 code 1210 code frequency to section HT and estabfrequency thereto. lishes a circuit for supplying energy of 180 code If the signals fail to respond to the changes frequency thereto. This circuit is traced from in the signal control relays, or if the signal reterminal BX through contact 180- of the code peater relays fail to respond to the changes in transmitter, front contact 16 of relay IZK, back the signals, the circuit of the relay lZCR will be contact 53 of relay I2J, front contact 61 of relay interrupted and contact 61 of this relay will re- EZCR, front contact 3! of relay 12H, and prilease and cut off the supply of energy of 180 a y Winding of transformer HTT to terminal code frequency to section HT and establish a circuit for supplying energy of 75 code frequency On picking up of relay [2K its contact 74 inthereto. t upts th p vi u y t a d r uit f r supply This modification employs a lightout relay in energy to the relay IZCR, but another circuit I2ULO to check the filament of the lamp of the for supplying energy to that relay is completed o upper signal IZSU. This relay governs the polarpicking p Of relay IZLG- This Circuit is traced ity of the energy supplied to the Winding of the from terminal B through front contact 20 of 15 l r signal |2sL to prevent the display of a relay a a t 60 o relay front green light by this signal atatime when the lamp contact. 74 of relay IZK, front contact 11 of of the upper signal. is burned out. The lightout relay IZUY, front contact 72 of relay IZLG back relay IZULO also controls the circuit of checking ct 63 o relay g, front Contact of relay I'ZCR so that when the lightout relay is lay IZULO, and Wlndlng relay IZCR to released, relay IZCR is also released and its contermmal h relay 15 of a type the tact 6! causes energy of 75 code frequency to be picked up in the interval between picking up of the contacts of relay 2K and picking up of relay |.2LG. Accordingly, contact 61 of relay EZCR. remains picked up and maintains the cir cuit for supplying energy of 180 code frequency to section HT.

At this timethe signal displays its approach Iii w ii l i :231 1 2 5;? this modification of the medmm mdlcamon nq i of a yellow hg-ht invention is arranged so that except for the, conof code frequency will be supplied to the section in the rear so that the signal for that section will display its most restrictive proceed indication and a train approaching the defective signal will so thatv this relay will release and its contact 61 units are Fontroued only by f control will interrupt the circuit for suppplying energy lays This aimngemeni mikes t t o 183. code frequ n y'to section HT! and will for changes m the W i to awalt establish a, circuit for supplying energy of 75 changes in the upper slgnal t m the reco-de frequency thereto, 70 peater relays for the upper signal unit, but per- When the train advances far enough to vacate mits thelower signal unit to respond immediately the. section in advance of section I351 energy of to a Change in Portion of the control relay code frequency is supplied to the rails of sec- As the slgnalumts respond promptly to n t 'qn 3T and the equipment for t t Section 0pin the control relays, the. signal will not. display crates, tosupnlyenergy of 1.80. frequency to sec- 5- ie i na 'e. a p ct on a. change in the signal to the relay IZLG. interrupts one circuit for supplying energy of 180,

. contact 3| of relay its contacts 20 and 23 cut off the control relays and it. is not necessary to provide means to prevent these signal flashes.

In addition, the checking relay |2CR checks correspondence between of coded energy to the section in the rear. This permits the supply of coded energy to the section in the rear to be controlled by the signal control relays so that changes in. the energy supplied to the section in the rear occur promptly.

Construction and operation of system shown in In Fig. 4 of the drawings there is shown a modification of this invention adapted for use where the wayside signals are arranged to providefive different aspects. This modification is similar to that shown in Fig. 3 and employs a checking relay CR which is governed by the signal control relays, the signal repeater relays, and the lightout relays. This modification differs from that shown in Fig. 3 in that lightout relays are provided for both the upper and lower signals, while this modification is similar to those shown in Figs. 1 and 2 as it employs means governed by the signal repeater relays to delay changes in the signals. This modification is also like that shown in Fig. 2 as it employs energy of 75M code frequency and has means for detecting this energy.

The system of Fig. 4 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 rails of section |2T and the track relay |2TR causes energy to be supplied through the decoding transformer |2DT to the relay |2HA and through the resonant rectifier unit IBODU to relay |2J. As-the 'relays |2I-IA and |2J are picked up, energy of normal polarity is supplied to the Winding of signal |2SU over the circuit which includes front contacts 29 and 23 of relay |2HA and front contacts 2| and 22 of relay |2J, so signal IZSU provides a green light while its contact G establishes the circuit to supply energy to the relay IZUG. At this time the circuit of the Winding of signal |2SL is interrupted by contacts 50 and 5| of relay |2HB so signal |2SL provides a red light and the signal repeater relays IZLG and The signal |2S, therefore, provides its clear indication consisting of a green light over a red light.

It is assumed that the filaments of the lamps of the signals are intact so the lightout relays |2ULO and |2LLO are both energized. Under these conditions ergized over the circuit which is traced from terminal B through front contact 2|) of relay |2HA, front contact 60 of relay |2J, back contact 6| of relay IZUY, back contact 62 of relay |2LG, back contact 85 of relay |2LY, front contact 63 of relay |2UG, front contact 64 of relay IZULO, front contact 86 of relay IZLLO, and winding of relay IZCR to terminal C.

At this time, energy of 180 code frequency is supplied to section HT over the circuit which is traced from terminal BX through contact I80 of the code transmitter |2CT, front contact 99 of relay |2J, front contact 61 of relay IZCR, front IZHA, and primary winding of transformer |TT to terminal CX.

When av train moving in the normal direction of traflic enters section |2T the track relay IZTR is shunted and energy is no longer supplied through the decoding transformer |2DT to the relays IZHA and |2J. On release of relay IZHA |2LY are both released.-

the checking relay |2CR is enthe signal control relays and signal repeater relays and controls the supply through front contact picked up the supply of energy supply of energy to the signal |2SU and this signal displays a red light, while relay IZUG releases. In addition, at this time the circuit of relay IZCR. is interrupted and its contact 61 releases, while contact 3| of relay |2HA cuts off the supply of energy of 180 .code frequency to section HT and causes energy of '75 code frequency to be supplied thereto.

At this time, therefore, signal |2S displays its stop indication consisting of a red light over a red light, while-energy of '75code frequency is supplied to the section in the rear.

When the trainenters section |3T the signal for that section displays its stop indication and energy of 75 code frequency is supplied to transformer |2TT. When the train vacates section |2T this energy feeds to the track relay |2TR and operates it so that energy is supplied through the decoding transformer |2DT to relay |2HA .minal B through front contact of relay IZHA,

back contact 34 of relay IZUG, back contact 22 of relay |2J, winding of signal |2SU, back contact 2| of relay |2J, back contact 35 of relay IZUG, and front contact 23 of relay |2HA to terminal C. The signal IZSU, therefore, displays a yellow light, and its contact Y establishes .the circuit of the relay IZUY, while the signal |2S provides its approach indication consisting of a yellow light over a red light.

When the relay -|2UY picks up it completes a circuit for supplying energy to the checking relay traced from terminal B 20 of relay |2HA, back contact of relay |2J, back contact 81 of relay 12K, back contact 88 of relay |2I-IB, back contact 89 of relay IZLY, front contact 99 of relay |2UY, back contact 9| of relay |2LG, back contact 63 of relay IZUG, front contact 64 of relay .I2ULO, front contact 86 of relay IZLLO, and

winding of relay |2CR to terminal C. Accord- |2SU responds in the proper manner and relay IZUY' is energized a circuit for the relay IZCR. willbe established.

When the relays |2HA and |2CR. are both of code frequency to section HT is cut off, and energy of IBM code frequency is supplied thereto over the circuit which is traced from terminal BX through contact 75M of the code transmitter |2CT,-back contact 94 of relay IZHB, back contact 95 of relay |2K, back contact 99 of relay |2J, front contact 61 of relay IZCR, front contact 3| of relay |2HA, and primary winding of transformer ITT to terminal CX.

When the train advances far enough to vacate section |3T the equipment for that section operates to supply energy of 75M code frequency to section IZT. When energy of this frequency is supplied to track relay |2TR energy continues to be supplied through the decoding transformer When relay |2HB picks up, its contacts 50 and 5| establish the circuit to supply energy of reverse polarity to the winding of signal IZSL.

This circuit is traced from terminal B through front contact 20 of relay |2HA, front contact 50 of relay IZHB, back contact 41 of relay IZLG, back contact 4| of relay |2K, winding of signal I 2SL,- back contact 490f relay 12K; -back'contact 4B of relay IZLG, front contact-Bibi relay I ZHB, and frontcontact-23 of relay IZHA to 'terminal C. Accordingly, the signal I 2SL=will display a yellow light and its contactYwill establish the circuit of relay -I2LY, while'thesignal IZS now displays its advance approachindication'consisting of a yellow light over a'yellow light,

When the relay I ZHB picks up, its contact 88 interrupts the previously traced circuit for supplying energy to the relay IZCR; but the circuit of this relay is reestablished when relay IZLY relays IZHB and IZLY. The relay IZCR is slow enough in releasing to remain picked up'throughout the interval in which the supply of energy to the relay I ZCR is interrupted.

On picking up of the relay I2HB its contact 94 interrupts the circuit for supplying energy of 75M code frequency to section I IT and estab lishes the circuit for supplying energy of 120 mary winding of transformer IITT to terminal CX.

When the train adyances farenough to vacate the section inadvance'ofsection I3T energyof I code frequency is supplied to section I2T and th track relay IZTR operates at a rate'su'ch that energy is no longer supplied to relay IZHB, but issupplied to relay I 2K, whilerelay IZHA remains picked up. Onpicking up of the relay I'2K 'its contacts 40 and 4I cut oif'the supply of energy of reverse polarity to the winding of signal I ZSL and establish the circuit for supplying energy of normal polarity thereto. This circuit is traced from terminal B through front contact 29 of relay IZHA, front contact 42 of relay I ZULO, front contact 40 of relay IZK, Winding of signal IZSL, front contact ll of relay IZK, front contact 43 of relay IZULO, and front contact 23 of relay I 2HA toterminal C. The

lish the circuit to en ity thereto. On release of relay IZK its contacts contact 29 of-relay IZHA, back contact 68. of

relay IZJ, front contact 87 of relay IZK, back contact 97 of relay I ZLY, front contact 98 of relay I2UY, 'front contact 9I of relay IZLG, back contact 63 of relay IZUG, front contact 64 of relay l2ULO,'front contact 86 of relay IZLLO, and Winding of relay IZCR to terminal C. Therelay IZCR is slow enough in releasing to remain picked up during the period in which the circuit of the relay is interrupted,so its contact 61 maintains the circuit for supplying energy of 180 code frequency to section HT.

When the train advances far enough to vacate the secondsection in advance of section EST energyof 180 code frequency is supplied to section IZT, and the track relay EZTR operates at a rate such that energy is supplied to relay I2J, but is not supplied to relay I'ZK, while energy continues to'be supplied to relay IZHA.

On picking up of relay I2J its contacts 2! and 22 interruptthe supply of energy of reverse polarity to the winding of signal EZSU and estabpply energy of normal polarwmding of signal IZSL. Accordingly, the signal of a green light over a red light.

When relay IZJ picksup, its contact '99 interrupts one circuit for supplying energy of 180 code frequency ,to section II T, and establishes the other circuit for supplying energy of this he quencyto section I I T.

'As signal IZSU is displaying a green light, re-

'lay IZUY is released and relay I2UG is picked up,

originally traced for this relay.

This modification of the invention includes approach indication.

'When energy of 180 code frequency is supplied I to section IZ' I', relays IZHA and I 2J are picked interrupts 'the circuit for supplying energy to signal I ZSL now displays a green light, While the signal, [28 displays its approach medium indicanormal P y is pp to the Winding Of s nal I2SU over the circuit which includes front contacts 29 and 23 of relay IZHA and front concontact Y interrupts the circuit of relay IZLY 119C155 2| and 22 f relay As a result of changes in traffic conditions in relay I2L advance the energy supplied to section I2T may On picking up of the relay I 2K its contact changed from 00018 frequency o 5M interrupts the circuit for supplying energyof 120 Code f eq e cy. On this change in the energy code frequency to section HT and establishes a 0 p d i S c ion ZT, energy is no longer supcircuit forsupplying energy of code frequency thereto. This circuit is traced from terminal iBX through contact I89 of the code transmitter 'I ZCT, front contact 95 of relay 12K, back contact 99 of relay I-ZJ, front contact 6'! of relay melt, front cs fieristic occurs on y on v ry three y s, ther contact 3| of relay IZHA, and primary winding of transformer I ITT to terminal'CX.

On picking up of the relay IZK its contact 81 the "relayI-ZCR, while this-circuit is additionally '70 pick up until'after the relay E ZJ releases.

interrupted by'contactfBB of relay IZHB when "thatrelay releases. Another'circuit is'es'ta'blislied and 22 of relay l2J for supplying this energy. In addition, on release of relay |2J its contact 33 interrupts the circuit of relay HUG, but the relay IZUG is of a type which is slow to release so its contacts remain picked up and maintain the supply of energy of normal polarity to the winding of signal |2SU for a period subsequent to the release of relay IZJ. Accordingly, the signal |2SU continues to display a green light during the transient interval.

When relay IZHB picks up, energy of reverse polarity is supplied to the winding of signal |2SL over the circuit which is traced from terminal B through front contact 2|! of relay IZHA, front contact 50 of relay I2HB, back contact 41 of relay |2LG, back contact 4| of relay |2K, winding of signal I2SL, back contact 40 of relay IZK, back contact 46 of relay IZLG, front contact 5| of relay IZHB, and front contact 23 of relay IZI-IA to terminal C. The signal |2SL, therefore, displays a yellow light.

On release of the relay IZUG the supply of energy of normal polarity to signal IZSU is cut ofi and energy of reverse polarity is supplied thereto over the circuit which includes back contacts 34 and 35 of relay IZUG and back contacts 2| and 22 of relay |2J. Accordingly, the signal IZSU displays a yellow light instead of a green light, and as the upper and lower units of signal |2S both display yellow lights the signal provides its advance approach indication.

The various parts of the apparatus are arranged and selected so that the contacts of relay |2UG remain picked up to cause signal TSSU to continue to display a green light until signal IZSL has been conditioned to display its yellowlight. This prevents the possible momentary display of a yellow over a red light by the signal |2S at this time. Such a signal would be interpreted by the engineman of an approaching train as indicating less favorable traffic conditions than actually exist and might cause him to unnecessarily effect an emergency applicalion of the brakes. This system prevents the momentary display of the approach indication at these times and thus eliminates possible delays in train movements.

The equipment operates in a similar manner to prevent a momentary display of the approach indication on a change in the signal aspect from the approach medium to the advance approach indication.

When energy of 120 code frequency is supplied to section IZT, the relays IZHA and IZK are picked up, while energy of reverse polarity is supplied to the winding of signal |2SU, and energy of normal polarity is supplied to the winding of signal |2SL. As the signal IZSL displays a green light its contact G establishes the circuit of the relay I2LG.

When the energy supplied to section I2T is changed from 120 to 75M code frequency the relay |2K releases and the relay IZHB picks up. On release of relay |2K its contacts and 4| interrupt one circuit for supplying energy of normal polarity to the winding of signal IZSL, but they establish a circuit including front contacts and 41 of relay |2LG for supplying energy of normal polarity to the signal IZSL so this signal continues to display a green light.

On release of relay IZK its contact M interrupts the circuit of relay I2LG, but the relay |2LG is of a type the contacts of which are slow to re-.

lease so they remain picked up after release of relay IZK and maintain the supply of energy to the winding of relay I2SL.

On picking up of relay IZHB its contacts 50 and 5| establish the circuit to supply energy of reverse polarity to the winding of signal |2SL on release of relay IZLG. Accordingly, on release of relay I2LG the supply of energy of normal polarity to the winding of signal |2SL is cut off, but energy of reverse polarity is supplied thereto so the mechanism of signal |2SL immediately conditions the signal to display a yellow light instead of a green light, and the signal |2S now provides its advance approach indication consisting of a yellow light over a yellow light.

The various parts of the apparatus are arranged and selected so that on the change in the energy supplied to section |2T from120 to M code frequency the relay |2LG remains picked up until after the relay IZI-IB picks up. This insures that on release of relay |2LG and consequent cutting off of the supply of energy of normal polarity to signal IZSL, energy of reverse polarity will be supplied thereto and the signal will display a yellow light and there will be no time interval during which the signal displays a red light.

If the circuit including the front contacts 45 and 41 of relay IZLG for supplying energy of normal polarity to the signal IZSL is not pro vided, the signal winding will be deenergized if relay IZK releases before relay I ZHB picks up. Under such circumstances the signal |2SL will display a red light until the relay |2HB picks up and during this interval the signal IZS will display its approach indication consisting of a yellow light over a red light. This is a more restrictive indication than is required by trafhc conditions and may unnecessarily delay traffic. The system of this invention eliminates the momentary display of the approach indication and thus prevents trafiic delays.

In the modification shown in Fig. 4 the circuit for supplying energy to checking relay IZCR, is controlled by contacts of the lightout relays for both the upper and lower signal units so that if the lamp of either of these units is burned out the checking relay |2CR will be released and will cause the energy supplied to section ||T to be of 15 code frequency. Accordingly, under these conditions the signal for section T will display its most restrictive proceed indication and trains will approach the defective signal at reduced speed.

Similarly, if for any reason there is a disagreement between the signal control relays and the signal repeater relays, the circuit of the relay |2CR will be interrupted and this relay will cause energy of 75 code frequency to be supplied to section MT.

The modification shown in Fig. 4, like the other modifications of the invention, has the circuit for supplying energy to the winding of signal |2SL controlled by the lightout relay IZULO to prevent the supply of energy of normal polarity to this signal, and consequent display of a green light by this signal, at a time when the lamp of the upper signal IZSU is burned out.

Although I have herein shown and described only four forms of railway signaling systems embodying my invention, it is understood that various changes and modifications may be made therein within the'scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a section of railway track, a control relay governed by traffic conditions in said section, a slow releasing relay, a light signal for said section, saidsignal being of a type whichhas a member biased to a first position in which it conditions the signal to provide one indication and having a Winding eiiective when energized to move said member to a secondposition in which it conditions the signal to provide a different indication and establishes a circuit to supply energy to said slow releasing relay pr videdsaid control relay is picked up, a circuit controlled by a front contact of said control relay for supplying energy to the winding of said signal, and a second circuit controlled by a front contact of said slow releasing relay for also supplying energy to the winding of said signal.

2. In combination, a section of railway track, a control relay governed by traffic conditions in said section, a slow releasing relay, 9, light signal for said section, said signal being of a type which has a member biased to a first position in which it conditions the signal to provide one indication and having a winding eifective when energized to move said member to a second position in which it conditions the signal to provide a different indication and establishes a circuit to supply en- 1 ergy to said slow releasing relay provided said control relay is picked up, a circuit controlled by a front contact of said control relay for supplying energy to the winding of said signal, and a second circuit controlled by a front contact of said slow releasing relay and a back contact of said control relay for also supplying energy to the winding of said signal.

3. In combination, a section of railway track, a control relay governed by traffic conditions in said section, a slow releasing relay, a light signal for said section, said signal being of a type which has a member biased to a first position in which it conditions the signal to provide a first indication and having a, winding efiective when supplied with energy of reverse polarity to move said member to a second position in which it conditions the signal to provide a second indication and when supplied with energy of normal polarity to move said member to a third position in which it conditions the signal to provide a third indication and establishes a circuit to supply energy to said slow releasing relay provided said control relay is picked up, a circuit including back contacts of the control slow releasing relay for supplying energy of 'reverse polarity to the winding of said signal, a circuit including a front contact of the control relay for supplying energy of normal polarity to the winding of said signal, and a front contact of said slow releasing relay and a back contact of said control relay for also supplying energy of normal polarity to the winding of said signal.

4. In combination, a section of railway track, a control relay governed by traffic conditions in said section, a slow releasing relay, a light signal for said section, said signal being of a type which has a member biased to a first position in which it conditions the signal to provide tion and having a winding efiective when supplied with energy of reverse polarity to move said member to a second position in which it conditions the signal to provide a second indication and when supplied with energy of normal plarity to move said member to a third position in which it conditions the signal to provide a third indication and establishes a circuit to supply energy to said slow releasing relay provided said control relay is picked up, a circuit including relay and of said circuit including a a first indicaverse polarity to move said back contacts of the control relay and of said slow releasing relay for supplying energy of reverse polarity to the winding of said signal, a circuit including a front contact of the control relay 7 for supplying energy of normal polarity to the winding of said signal, and a circuit including a front contact of said slow releasing relay for also supplying energy of normal polarity to the winding of said signal.

5. In combination, a section of railway track, a first control relay governed by traffic conditions in said section, a second control relay governed by trainc conditions in advance of said section, a slow releasing relay, a light signalforsaidsection, said signal being of a type which has a member biased to a first position in which it conditions the signal to provide a first indication and having a winding effective when supplied with energy of reverse polarity to move said member to a second position in which it conditions the signal to provide a second indication and when supplied with energy of normal polarity to move said member to a third position in which it conditions the signal to provide a third indication and establishes a circuit to supply energy to said slow releasing relay provided the second control relay is picked up, a, circuit including a front contact of the first control relay and back contacts of the second control relay and of the slow releasing relay for supplying energy of reverse polarity to the winding of said signal, a circuit including front contacts of the first and second control relays for supplying energy of normal polarity to the winding of said signal, and a circuit including front contactsof the first control relay and the slow releasing relay for also supplying energy of normal polarity to the winding of said signal.

6. In combination, a section of railway track, a signal for said track section, said signal being of a type having a member biased to a first position inwhich it conditions the signal to provide a first indication, said signal having a winding effective when energized with current of remember to a second position in which it conditions the signal to provide a second indication and establishes a circuit to supply energy to a first repeater relay, said winding being efiective when energized with current of normal polarity to move said member to a third position in which it conditions the signal to provide a third indication and establishes a circuit to supply energy to a second repeater relay, a first control relay governed by traffic conditions in said section and controlling the supply of energy to the winding of said signal, a second control relay governed by traffic conditions in advance of said section and controlling the polarity of the energy supplied to the winding of said signal in such manner that energy of reverse polarity is supplied to the signal winding when said relay is released and energy of normal polarity is supplied to the signal winding when said relay is picked up, a checking relay, a circuit for supplying energy to said checking relay when the first control relay'is picked up provided the first repeater relay is also picked up and the second control relay and the second repeater relay are released, a circuit for also supplying energy to said checking relay when the first and second control relays are picked up provided the first repeater relay is released and the second repeater relay is picked up, and means including said checking relay for controlling trafiic approaching said section.

- advance of said section indication and having energized with current nal to provide '7. in combination with a section of railway track, means governed by traffic conditions in for at times supplying to the rails of said section coded energy of afirst character and at other times of a second character, a code following track relay receiving energy over the rails of said section, a first and a second control relay associated with said track relay, means effective when the track relay is respondingto energy of either character to energize the first control relay and effective only when the track relay is responding to energy of the second character to energize the second control relay, a signal for said section, said signal being of, a type having a member biased to a first position in which it conditions the signal to provide a first winding effective when of reverse polarity to move said member to a second position in which it conditions the signal to provide a second indication and to establish a circuit to supply energy to a first repeater relayand effective when energized with current of normal polarity to move said member to a third position in which it conditions the signal to provide a third indication and establishes a circuit to supply energy to a second repeater relay, a checking relay, a circuit including front contacts of the first control relay and the first repeater relay and back contacts of the second control relay and the second repeater relay for supplying energy to said checking relay, a circuit including front contacts of first and second control relays and of the second repeater relay and a back contact of the first repeater relay for also supplying energy to said checking relay, and means controlled by said checking relay for governing traffic approaching said section.

8. In combination with a section of railway track, means governed by traffic conditions in advance of said section for at times supplying to the rails of said section coded energy of a first character and at other times of a'second character, a code following track relay receiving energy over the rails of said section, a first and a second control relay associated with said track relay, means effective when the track relay is responding to energy of either character to energize the first control relay and effective only when the track relay is responding to energy of the second characterto energize the second control rela a signal for said section, said signal being of a type having a member biased to a first position in which it conditions the siga first indication and having a winding effective when energized with current of reverse polarity to move said member to a second position in which it conditions the signal to provide a second indication and to establish a circuit to supply energy to a first repeater relay andeffective when energized with current of normal polarity to move said member to a third position in which it conditions the signal to provide a third indication and establishes a circuit to supply energy to a second repeater relay, a checking relay, a circuit including front contacts of the first control relay and the first repeater relay and back contacts of the second control relay and the second repeater relay for supplying energy to said checking relay, a circuit including front contacts of first and second control relays and of the second repeater relay and a back contact of the first repeater relay for also supplying energy to said checking relay, said signal including a lamp, a lightout relay energized in series with said lamp and having a contact included in series with each of the circuits for supplying energy to said checking relay, and means controlled by said checking relay for governing traific approaching said section.

9. In combination with a section of railway track, means governed by traffic conditions in advance of said section for at times supplying to the rails of said section coded energy of a first character and at other times of a second character, a code following track relay receiving energy over the rails of said section, a first and a second control relay associated with said track relay, means effective when the track relay is responding to energy of either character to energize the first control relay and effective only when the track relay is responding to energy of the second character to energize the second control relay, a signal for said section, said signal being of a, type having a member biased to a first position in which it conditions the signal to provide a, first indication and having a winding effective when energized with current of reverse polarity to move said member to a second position in which it conditions the signal to provide a second indication and to establish a. circult to supply energy to a first repeater relayand effective when energized with current of normal polarity to move said member to a third position in whichit conditions the signal to provide a third indication and establishes a circuit to supply energy toa second repeater relay, a checking relay, a circuit including front contacts of the first control relay and thefirst repeater relay and back contacts of the second control relay and the second repeater relay for supplying energy to said checking relay, a circuit including front contacts of first and second control relays and of the second repeater relay and a back contact of the first repeater relay for also supplying energy to said checking relay, a circuit including a back contact ofthe first control relay for supplying coded energy of the first character to the rails in the rear of said section, andacircuit including a front contact of the first control relay for supplying to the rails in the rear of said section coded energy of the first or second character according as said checking relay is released or picked up respectively.

10. In combination, a section of'railway track, a first and a second control relay, means governed by traffic conditions in said section and in advance of said section for at times supplying energy to said first control relay and at other times supplying energy to said second control relay, a slow releasing relay, a signal for said section having an upper and a lower unit, each of said signal units being of a typehaving a movable member biased to a first position in which it conditions the unit to provide one aspect and having a winding effective when energized to move said member to a second position in which it conditions said unit to provide a second aspect, a circuit including a front contact of said first control relay for supplying energy to the winding of said upper signal unit, and a circuit including a front contact of said first control relay and a contact of said upper signal unit closed only when the movable member of said signal unit is in its second position for supplying energy to said slow releasing relay, said slow releasing relay being effective when picked up to establish a circuit to also supply energy to the winding of said upper signal unit, said second control relay being effective when energized to establish a relay maintains the supplyof energy to the Winding of the upper signal unit until the second control relay becomes energized.

11. In combination," a section of railway track, a first and a second control relay; means gov- "ernedby trafiic conditions in said section-and in controlled by a front contact of said control readvance of said section for at times supplying en- I ergy to thefirst control relay and'at other times "supplying energy to the'second control relay, a

signal for said section having an'upp'er and a lower unit, each of said signal units being of a type which has a member biased to a first positionin which it conditions the signal unit to provide one aspect and having a winding efiective when energized to move said member to a second position in whichrit conditions the' signal unit to'provide a second aspect, a first and a second slow releas-.-

ing relay, a circuit including a'front contact of the first control relay for' supplying energy to the winding of said upper signal unit, acircuit including a front contact of saidfirst control relay" and a contact of said uppersignal unit closed only when the movable member of "said unit is in its'second positionfor supplying energy to the first slow releasing relay, a' circuit including front contacts "of said first slow releasing relay for also supplying energy to the winding of said: upper signal unit, a circuit including a front contact of said second signal control relayfor supplying energy to the winding of" said lower signal unit, a circuit including afront contact lay 'for'supplying energy to said-operating winding; a second circuit controlled by a front'con- 'tact'ofsaid slow releasing relay for also supplying energy to said operating winding, and means controlled by said slow releasing relay for governing traflic approaching said section.

13. In combination with a section of railway track, a signal for said section having an-upper and a lower unit each having a lamp, each of said units having a'member'biased to a first position in which it conditions the associated unit to display a first indication, each unit having an operating Winding eifective when energized with current of one polarity to move said member to a second position in which it conditions the unit to display a second indication and effective when energized with current of the other polarity to "move said member to a third position in which it conditions the unit to display a third indication, means governed by trafiic conditions for at times supplying energy of said one polarity and for at other times supplying energy of said other polarity to the winding of said upper unit and for at both said times supplying energy to the winding of said lower unit, a lightout relay for checking the integrity ofthe lamp of one of said units, and means controlled by said lightout relay effective when 'a defect occurs in the associated lamp for preventing the supply of energy of said other polarity to the other unit.

of said second signal controlrelay and a contactof said lower signal um't closed only when the movable member of said unit is in its second position for supplying energy'to'said's'econd slow releasing relay, j'and a circuit including a front, contact of said'second slow releasing-relay-for also supplying e ergy to the winding of said lower signalunit.

12. In combination-with'a sectionof railway track, a control relay governed'by trafiicccndi tions in said section/a" slow releasing relay, a light signal for said section',-said signal having 'a member biased toa first-position in which it conditions the signal to display one indication and having an operating winding 'efiec'tive when it energized to move said member to-a second--po-' sition in which it conditions the signal to display a different indication and establishes acircuit for supplying energy to said slow releasing-relay provided said control relay is picked up, a circuit '14; In combination with a section of railway track, a signal for said section having an upper and a'lower unit each having a lamp, each of said units having a member biased to a first position in which it conditions the associated unit to display a first indication, each unit having an operating Winding efiective when energized with current of one polarity to move said member to a second position in which it conditions the unit to display a second indication and effective when energized with current of the other polarity to move said member to a third position in which it -conditions the'unit todisplay a third indication,

means governed by trafiic conditions for at times supplying energy of said one polarity and for at other times supplying energy of said other polarity tothewinding of said upper unit and for at both said timessupplying energy to the winding or said lower unit, a lightout relay for checking the integrity of the lamp of said upper unit, and means controlled by said lightout relay effective when-a defect occurs in the associated lamp for preventing the supply of energy of said other polarity to thelower unit to thereby prevent the display of a proceed indication by said lower unit. .7 e

RALPH R. KEMMERER.

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