US2302046A - Railway signaling system - Google Patents

Description

Nov. 17, 1942. H, NICHOLSON 2,302,046

RAILWAY SIGNALING SYSTEM I Filed Jul},' 20, 1940 2 Sheets-Sheet l I Fig. I.

' INV NTOR ihmbjZ/V' 1 012 H145 ATTORNEY Nov. 17, 1942.

F. NICHOLSON I 2,302,046

RAILWAY SIGNALING SYSTEM Filed July 20, 1940 2 Sheets-Sheet 2 Quart/ olled Con za0z Closed 0 'T 42 .5'0 3 MC Szlgnal INVENTOR Hall/s HJV OZJOIZ H15 4 ATTORNEY Patented Nov. 17, 1942 UNITED STATES PATENT OFFICE 2,302,046 RAILWAY SIGNALING SYSTEM Application July 20, 1940, Serial No. 346,577

9 Claims. (Cl. 24638) My invention relates to a railway signaling system of the type employing coded current in the track circuits thereof, and particularly to means for reducing the current consumption of such a system.

This application is a continuation in part of my application Serial No. 318,122, filed February 9, 1940, now U. S. Patent 2,249,722, granted July 15, 1941, for Approach control apparatus for railway signaling systems.

Some types of coded signaling systems employ energy coded at different frequencies and have decoding means for detecting response of a track relay to these different frequencies of energy. One form of coded signaling system employs energy of 75 and 180 code frequency, that is 75 and 180 energy impulses per minute which are separated by intervals during which no energy is supplied. In such a system when a track section is occupied, energy of 75 code frequency is supplied to the adjacent section in the rear with the result that the signal for that section is conditioned to display its yellow or caution indication, while energy of 180 code frequency is supplied to the rails of the sections farther in the rear to l condition the signals for those sections to display their green or clear indications.

The decoding means for detecting response of a track relay to energy of 180 code frequency consumes a relatively large amount of current, and a substantial saving in current consumption can be effected if this decoding means is deenergized at times when its operation is not required.

It is an object of my invention, therefore, to provide an improved coded railway signaling system having separate decoding means for detecting response of a track relay to energy of one code frequency, and having means to deenergize this decoding means at all times except when operation of the decoding means is essential to operation of the signaling system.

A further object of my invention is to provide an improved signaling system of the type describedand in which the decoding unit for detecting energy of one code frequency is approach controlled so as to be energized only when the adjacent section in the rear is occupied.

Another object of my invention is to provide an improved system of the type described and in which one decoding unit is deenergized whenever the associated track section is occupied.

A further object of my invention is to provide a system of the type described including means to approach control both one decoding means and the lamps of the signals, the system being arranged so that on entrance of a train into a section and operation of the approach control means, lighting of the lamps is delayed until the decoding means has had an opportunity to function.

Another object of my invention is to provide an improved signaling system of the type described and adapted for use with semaphore signals, the system being arranged so that lighting of the signal lamp is deferred for a period long enough after operation of the decoding means is initiated to permit the signal arm to be moved from one position to another before the lamp is lighted.

A further object of my invention is to provide an. improved coded railway signaling system.

I shall describe one form of railway signaling system employing my invention, together with one modification which I may employ, and shall then point out the novel features thereof in claims.

In the drawings Fig. 1 is a diagram of a stretch of railway track equipped with a signaling system embodying my invention, and

Fig. 2 is a modification of the system shown in Fig. 1.

Referring to Fig. 1 of the drawings, there is shown therein a stretch of railway track having track rails I and 2 over which trafiic normally moves in the direction indicated by the arrow, that is, from left to right. The rails of the track stretch are divided by insulated joints 3 into the customary successive track sections. One complete track section, designated IZT, is shown, together with portions of the adjoining sections I31 and HT.

Each track section has at the entrance end thereof a wayside signal S for indicating to approaching trains the nature of traffic conditions in advance. As shown, the signals are of the color light type, each having a green or clear lamp G, a yellow or caution lamp Y, and a red or stop lamp R. While signals of the color lamp type have been illustrated, the invention is not limited to the use of signals of this type and any appropriate style of wayside signals may be employed.

Each track section has a code following track relay TR, connected across the section rails adjacent the entrance end thereof, while each section has means governed by the track relay of the section in advance for continuously supplying energy of either 75 or 180 code frequency to the section rails adjacent the exit end thereof.

Each track relay has associated therewith ed at this time.

auxiliary relays H, J and a code transmitter CT. The code transmitters may be of any suitable type and as shown have contacts 75 and I80 which are continuously actuated by a motor or other means to supply 75 and 180 energy impulses per minute which are separated by time intervals of equal length during which energy is not supplied. The code transmitters are also arranged so that during the off intervals in the code supplied to a section a circuit is established which shunts the section rails to thereby prevent a charge being developed in the ballast of the section.

In addition, each track relay has associated therewith approach control apparatus comprising relays AR, ARP and ARR. The approach control means employed in the systems shown in this application is shown in Letters Patent of the United States-No. 2,176,605 to Herman G. Blosser. The invention is not restricted to use in connection with approach control means of this type, and any approach control means wellknown in the art may be employed if desired.

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 rails of section II T and thus to the track relay IITR,

As a result of code following operation of the track relay HTR, energy from a local source of direct current, the terminals of which are designated'B and C, is alternately supplied to the two end portions of the primary winding of the decoding transformer IIDT so that energy is induced in the transformer secondary winding, while a contact of the track relay rectifies the energy supplied from this secondary winding to the winding of the relay I IE and this relay is picked up.

As relay III-I is picked up, its contact 20 establishes the circuit of the 180 contact of the code transmitter ICT, and during the pickedup periods of this contact a circuit is established to supply energy from the track battery [2TB to the rails of section I2T. This circuit is traced from one terminal of the battery IZTB through contact |30of the code transmitter, contact 20 of relay! II-I, winding of detector relay I2AR and resistor H to track rail 2, while track rail l is connected to the other terminal of the track battery IZTB.

Accordingly, during the picked-up periods of contact I80 of code transmitter HOT impulses of energy are supplied to the rails of section IZT over a circuit which includes the relay IZAR in series therewith.

The various parts of the equipment are arranged and proportioned so that when section IZTis unoccupied, the value of the current fiow- 1 60 ing in the track circuit of this section is too small to pick up the relay IZAR, and accordingly the contact 23 of this relay remains released and interrupts the circuit of relay IZARP.

As'relay I2ARP is released, its contact 24 interrupts the circuit of the decoding transformer HDTA, while contact 25 establishes the circuit of relay! ZARR. As relay IZARR is picked up, its

.contact 21 interrupts the circuits of the lamps of the signal HS and these lamps are not illuminat- This is proper as section I2T is assumed to be vacant and there is no need for the signal HS to display an indication;

As contact 24 of relay I ZARP interrupts the circuit of the primary winding of transformer 5 IDTA, no energy is supplied through this transformer and the resonant rectifier unit H RU to the relay HJ. Accordingly, the relay NJ is released, while no energy is consumed by the transformer HDTA, the resonant unit EU and the relay I lJ This saving of energy is substantial as these elements consume considerable current.

During the released periods of the contact I of the code transmitter l iCT the circuit for supplying energy from the track battery IZTB to the rails of section |2T is interrupted, while a circuit including a back contact of the code transmitter contact I80 is established to shunt the rails of section IZT and thus dissipate any charge which may have been developed between the rails of section I2T.

On the supply of energy of code frequency to the track relay I2TR the equipment associated with this relay operates in the manner explained in detail in connection with section HT so that relay [2H is picked up to establish the circuit to supply energy of 180 code frequency to the rails of section IST, while as long as section HT is vacant, the detector relay ISAR remains released so that relay |3ARP is also released and relay ISARR is picked up,

Operation of system shown in Fig. 1 on movement of a. train through the track stretch.

When a train moving in the normal direction of trafiic, that is, from left to right, enters section l3T, it shunts the track relay, not shown, for that section,- while on shunting of the relatively high resistance track relay and establishment of a relatively low resistance path between the track rails through the wheels and axles of the vehicles of the train there is an increasein the value of the current flowing in the track circuit for section I3T. In addition, as the train advances in the section and reduces the length of the rails included in the track circuit, there is a further increase in the value of the current flowing in the track circuit, and therefore, in the winding of the detector relay |3AR which is included in series with the track circuit. The various parts of the equipment are selected and proportioned so that when the train advances to a predetermined point in the track section I3T, such as 4000 feet from the signal I 253, the current flowing in the track circuit of section I3T will be increased to a Value which will effect operation of the detector relay ISAR.

Accordingly, when a train advances to a predetermined point in section I3T, the detector relay I 3AR. responds to the coded energy supplied to the track circuit for section [3T and contact 23 establishes a circuit to supply energy to the relay I3ARP and the contacts of this relay pick up. The circuit of the relay IEARP is interrupted during the off intervals in the code supplied to the rails of section IET, but the relay ISARP is of a type which is slow in releasing and its .contacts remain picked up during the intervals gy is thereafter induced in the transformer secondary winding, and as the track relay IZTR is responding to coded energy of 180 code frequency, the energy induced in the transformer secondary winding is of such frequency as to be freely supplied through the resonant rectifier unit I2RU to the relay IN.

The resonant rectifier unit is of a construction well-known in the art and comprises an inductance and a capacitor which are selected and proportioned to freely pass energy of the frequency supplied thereto when the track relay is responding to energy of 180 code frequency, and so as not to pass energy of substantial value when the track relay is responding to energy of a difi ferent code frequency, as for example, the 75 code frequency. The resonant rectifier unit includes a rectifier which converts into direct current the alternating current which is supplied through the unit.

It will be seen, therefore, that when a train advances to a predetermined point in section I3T, the detector relay I3AR begins to respond to coded energy with the result that relay l3ARP picks up and completes the circuit of the decoding transformer IZDTA. Energy is thereafter supplied from the transformer to the relay I2J and this relay picks up and establishes the circuit over which energy is supplied to the green or clear lamp G of the signal 128.

In addition, on picking up of relay I3ARP its contact 29 interrupts the circuit of the relay I3ARR and after a time interval, the contact 21 of relay |3ARR releases and establishes the circuit for supplying energy to the lamp G of signal I25. This circuit is traced from terminal B over back contact 21 of relay I3ARR, front contact 30 of relay I2H, front contact 32 of relay IZJ, and lamp G of signal 123 to terminal 0.

The relay |3ARR is of the slow releasing type and is selected so that on picking up of relay HARP and interruption of the circuit of relay I3ARR and establishment of the circuit of the transformer I2DTA, the contact 2'! of relay ISARR will not become released and complete the circuit for energizing the lamps of signal IZS until the relay IZJ has had time to become picked up. This prevents a flash of the yellow lamp Y which would otherwise occur.

When the train advances into section :21, the track relay IZTR is shunted and ceases to follow coded energy. Accordingly, energy is no longer supplied through the decoding transformer I2DT to the relay I2H and this relay releases with the result that its contact 30 interrupts the circuit of the green lamp G of signal I28 and establishes the circuit of the red or stop lamp R, while contact 26 interrupts the circuit of the decoding transformer I2DTA to out of? consumption of energy by this decoding means.

In addition, on release of relay 12H contact interrupts the circuit for supplying energy of 180 code frequency to the rails of section HT and establishes the circuit for supplyingenergy of '75 code frequency thereto. As long as any portion of the train remains in section I3T, the track rails of the section are shunted and the value of the current in the track circuit is high enough to cause code following operation of the detector relay I3AR so that relay I3ARP remains picked up and relay BARR remains released and continues to establish the circuit of the red or stop lamp R of the signal I2S.

' However, as soon as the rear of the train vacates section I3T, the current in the track circuit of this section is reduced to a value insufficient to operate the detector relay I3AR and this relay no longer supplies energy to the relay I3ARP, while the relay I3ARP releases and establishes the circuit of the relay I3ARR and interrupts the circuit of the decoding transformer IZDTA. On picking up of relay BARR the circuit of the red lamp R of signal I33 is interrupted and this lamp is extinguished.

When the train advances to a predetermined point in section I2T, the detector relay IZAR begins to respond to coded energy supplied to the track circuit of section IZT and relay IZARP picks up, while relay I2ARR releases as explained above. As the track stretch is assumed to be vacant, the track relay HTR is responding to energy of 180 code frequency so that the relay HH is picked up and relay IIJ becomes picked up after picking up of relay IZARP. Accordingly, on release of relay IZARR the green or clear lamp G of signal I [S is lighted.

When the train advances into section HT, the relay III-I releases and interrupts the circuit of the green lamp and establishes the circuit of the red lamp R of signal HS, while it also interrupts the circuit of the decoding transformer HDTA. In addition, release of relay HH cuts off the supply of energy of 180 code frequency to the rails of section IZT and establishes the circuit to supply energy of code frequency thereto.

When the train vacates section I2T, this energy feeds .to the track relay IZTR and causes code following operation of the relay with the result that energy is supplied through the decoding transformer I2DT to the relay HE and this relay picks up and changes the energy supplied to section [3T from '75 code frequency to code frequency.

Similarly, when the train advances far enough to vacate section HT, energy of '75 code frequency is supplied to the track relay for this section with the result that relay HH picks up and changes the energy supplied to section IZT from 75 to 180 code frequency. On this change in the energy supplied to the track relay IZTR the relay l2I-I remains picked up and maintains the circuit for supplying energy of 180 code frequency to the adjacent section in the rear, while the relay I2J remains released until a train enters section I3T and effects operation of the detector relay I3AR.

The system provided by this invention is arranged so that if while a train is present in section HT, a second or following train enters section I3T, it will receive a yellow or caution indication from the signal I 2S.

When section HT is occupied and section [2T is Vacant, energy of 75 code frequency is supplied to the rails of section IZT and to the track relay [2TB with the result that energy is supplied through the decoding transformer IZDT to the relay 12H. As relay IZH is picked up, its contact 20 establishes the circuit to supply energy of 180 code frequency to the rails of section I3T, while contact 26 establishes the circuit over which energy is supplied to the decoding transformer I2DTA, and contact 33 establishes the circuit over which energy is supplied to the yellow lamp 70 Y of signal I2S.

circuit of the relay BARR which thereafter releases and completes the circuit of 'the yellow or caution lamp Y of signal IZS.

At this time as the circuit of the decoding transformer I2DTA is complete and as the track relay IZTR is responding to coded ener y; current is induced in the secondary winding of the transformer IEDTA. However, as the track relay is responding to energy of 75 code frequency, the frequency of the alternating current induced in the secondary winding of transformer IZDTA is such that it is not freely passed by the resonant unit I2RU, and too little current is supplied to the relay I2J to pick it up. Accordingly, its contact remains released and maintains the circuit of the yellow lamp Y of signal IZS.

In like manner, when one track section is occupied and a second or following train enters the adjoining section in the rear, it will receive a stop indication from the signal for the occupied section. If, for example, section |2T is occupied, the track relay for this section will be released and energy will not be supplied through the decoding transformer 'l2DT to the relay 121-1. The relay 12H will be released, therefore, and will establish the circuit for supplying energy of 75 code frequency to the rails of section I3T, while contact 26 will interrupt the circuit of the decoding transformer IZDTA, and contact 33 will establish the circuit through which energy is supplied to the red or stop lamp of signal [28.

If a second train enters section IST and effects operation of the detector relay BAR, relay |3ARP will pick up and relay BARR will release and complete the circuit for supplying energy to the red lamp of signal I38.

On picking up of relay I3ARP the circuit of the decoding transformer HEDTA is not established as this circuit is interrupted at this time by contact 26 of relay l2I-I. This prevents supply of energy to the transformer IZDTA at this time when no purpose would be served by supply of energy to this transformer.

From the foregoing it will be seen that the system provided by this invention is arranged so that the decoding transformer IZDTA for detecting when the track relay is responding to energy of 180 code frequency is normally deenergized with the result that current consumption by this decoding means is restricted to those periods during which operation of the decoding means is necessary in the operation of the signaling system. The circuit of this decoding means is controlled by the approach control means so as to be complete -only when a train is present in the I section in the rear of the signal controlled by the decoding means. This is the only time the signal displays an indication and is, therefore, the only time operation of the decoding means is required.

In addition, the circuit of this decoding means is controlled by the H relay of the associated signal apparatus so that the circuit of the decoding transformer DTA can only be established when the H relay is picked up, that is, when the track relay is responding to coded energy. This prevents supply of energy to the transformer DTA whenever the associated track section is occupied. This is desirable since when a section is occupied and the track relay for the section is shunted, there is no need for the decoding means to function.

Furthermore, a train might stop and remain for a substantial time interval with portions thereof in two track sections so that the approach control means for the rearward one of these sections wouldoperate to establish the circuit of the decoding transformer DTA with resultant large current consumption during this time interval if this circuit were not interrupted by a contact of the H relay.

The equipment is also arranged so that the approach control apparatus controls not only the decoding transformer and the relay J, but also the signal lamps, while the control equipment is arranged so that the circuit of the signal lamps is not established for a. time interval subsequent to establishment of the circuit of the transformer DTA and the J relay, this time interval being long enough to enable the J relay to become picked up if traffic conditions are such that it should do so. This arrangement prevents a flash 0f the yellow lamp which might otherwise occur.

It is contemplated that the invention may be applied to signaling systems employing signals of types other than color light signals employed in the system shown in Fig. 1. For example, the invention might be employed in a signaling system employing semaphore signals. These require a substantial time interval for movement of the semaphore arm from the 45 or caution .position to the 90 or clear position. In order to prevent a flash of a signal lamp it is essential to delay lighting of the lamp until the signal arm has had time to complete its movement, and Fig. 2 is a diagram showing a modification adapted for use in connection with signals of the semaphore type.

Construction and operation of modification shown in Fig". 2

The system shown in Fig. 2 is similar to that shown in Fig. 1 and the same reference characters are employed to identify the elements which are common to both figures.

The system shown in Fig. 2 employs a signal its of the semaphore type. The details of construction and operation of this signal are not a part of this invention and any type of signal well known in the art may be employed. One form of signal which may be employed is described on page and following of the Signal Dictionary, 1908, while signals of this type are also described on page 265 and following, of a book Alternating current signaling, by Harold McCready.

The signal 558 has a signal arm which is supported on a pivot and is movable thereon to either of three positions to provide three signal indications. The signal arm or blade has a horizontal or stop position, a 45 position in which it pro-videsa caution indication, and a or vertical position and it provides a clear indication.

The signal arm is provided with roundels or lenses of different colors which are positioned in front of a. lamp L in different positions of the signal arm. Thus there is a red, a yellow and a green roundel through which light is projected in the stop, caution and clear positions of the signal arm.

The signal includes a motor for moving the sig nal arm to its 45 and 90 positions, while it in-' cludes holding magnets for maintaining the signal arm in these positions. The equipment is shown in Fig. 2 in the condition which it assumes when the track stretch is vacant. At this time energy of code frequency is supplied to the rails of section IBT and effects code following operationof the track relay ISTR with the result that energy is supplied through the transformer ISDT to the relay IBH, and contact 20 establishes the circuit for supply.-

ing energy of 180 code frequency from the track battery HTB to the rails of section HT over a circuit including in series therewith the detector relay HAR and the resistance 2|.

As the track stretch is assumed to be vacant, too little energy flows in the track circuit of sec-- tion HT to operate the detector relay HAR, and accordingly no energy is supplied to relay HARP and this relay is released and interrupts the circuits of the decoding transformer IBDTA and the relay HAS.

Asthe circuit of transformer IBDTA is interrupted, no energy is supplied to the relay "SJ and this relay is released.

As relay ISH is picked up and relay IBJ is released, a circuit is established which includes front contact 40 of relay IGH and back contact 4| of relay NJ for supplying energy to the mechanism of signal [65 to maintain the signal arm in its 45 or caution position.

In addition, as relay HAS is released, the circuit of the lamp I6L of signal MS is not lighted.

If a train now enters section IT and advances I far enough to effect operation of the detector relay HAR, the relay HARP will pick up and complete the circuit of the transformer ISDTA so that energy is supplied therefrom through the resonant unit IBRU to pick up the relay IEJ. When relay IBJ picks up, its contact 4| interrupts the circuit for causing the mechanism of the si nal IBS to maintain the signal arm in the 45 or caution position, and establishes the circuit to cause the signal mechanism to move the signal arm to its 90 or clear position and to thereafter maintain it in this position.

When relay HARP picks up, its contact 42 establishes a circuit including back contact 44 of relay HAS for energizing the heating element of a thermal relay HTE. This relay has a normally open contact 45 which controls a pick-up circuit for the relay HAS. The contact 45 becomes picked up after the expiration of a time interval after the supply of energy to the heating element of the relay is initiated. This time interval is long enough to permit the relay |6J to become picked up and for the signal arm to thereafter be moved from its caution position to its clear position.

When contact 45 of the thermal relay HTE picks up, it establishes a pick-up circuit for the relay HAS and relay HAS picks up. When its contact 44 is picked up, it interrupts the circuit of the heating element of relay HTE and establishes a stick circuit to maintain the relay HAS energized as long as relay HARP remains picked n picking up of relay HAS its contact 41 establishes the circuit of the lamp ISL and this lamp becomes lighted so that the signal IBS displays a green light to provide a clear indication.

The system is also arranged so that if the signal arm completes its movement before the thermal relay HTE picks up and establishes the pick-up circuit of relay HAS, a circuit will be established for this relay by a signal controlled contact 50. This contact is controlled by the signal arm of the signal IBS in such manner as to be closed when and only when the signal arm is in its 90 or clear position.

Accordingly, if the signal arm completes its movement to its clear position before the thermal relay HTE picks up, the signal controlled contact 50 will establish a pick-up circuit for the relay HAS and this relay will pick up and establish the stick circuit to maintain itself energized,

while it will establish the circuit of the lamp IGL and interrupt the circuit of the thermal relay HTE.

When the train under consideration advances into section I6T, the track relay IBTR is shunted and relays l6I-I and NH release. Release of relay IBH interrupts the circuit of the mechanism of signal [6S andthe signal arm thereupon moves to its horizontal or stop position. In addition, on release of relay IBH its contact 20 interrupts the circuit for supplying energy of code frequency to section HT and establishes the circuit for supplying energy of 7 5 code-frequency to section HT.

, When the train advances far enough to vacate section HT, the relay HAR ceases to respond to coded energy andthe relay HARP releases and interrupts the circuit of relay HAS which thereupon releases and interrupts the circuit of the lamp ISL.

When the train advances into the section in advance of section IGT, the equipment associated with that section operates to supply energy of 75 code frequency to the rails of section IBT and when the train vacates section I6T, this energy feeds to the track relay I6TR.

When the track relay [6TB responds to energy of 75 code frequency, energy is supplied through the decoding transformer MDT to the relay [6H, and on picking up of this'relay contact 20 changes the energy supplied to section HT from 75 to 180 code frequency, While contact 40 establishes the circuit for. supplying energy to the signal mechanism to cause it to move the signal arm from its horizontal or stop position to its 45 or caution position.

When the train advances far enough to vacate the section in advance of section IBT, the energy supplied to section I6T is changed from 75 to 180 code frequency and the relay I6I-I remains picked up, while relay IBJ remains released as the circuit of the decoding transformer IBDTA is interrupted by contact 24 of relay HARP. Accordingly, the signal arm of signal IES remains in its 45 or caution position until a train enters section HT and effects operation of relay HAR at which time relay IBJ becomes picked up and the signal arm is moved to its vertical position as explained above.

In the system provided by this modification the circuit of the signal lamp is controlled by the relay HAS, while this relay is controlled by the thermal relay HTE in such manner that lighting of the signal lamp is delayed long enough to permit the signal armto b moved from its caution to its clear position. When the signal arm reaches its clear position, a circuit is established to pick up the relay HAS even though the thermal relay HTE has not completed its operation.

If trafiic conditions are such that the .signal arm of signal I6S does not move to its vertical or clear position, the circuit of the relay HAS will be established when contact 45 of thermal relay HTE picks up instead of when signal controlled contact 50 is closed.

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

Having thus described my invention, what I claim is:

1. 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 forward and a rearward track section, means governed by trafiic conditions in advance of said forward section for at one time supplying coded energy of a first character and at other times supplying coded energy of a second character to the rails of said forward section adjacent the exit end thereof, a code following'track relay at the entrance end of said forward section having a winding receiving energy over the rails of said section, a first decoding means including a first auxiliary relay, a second decoding means including a second auxiliary relay, a first circuit controlled by the track relay for supplying energy to the first decoding means, a second circuit controlled by the track relay for supplying energy to the second decoding means,

the first decoding means being arranged so that the first auxiliary relay is picked upwhen the track relay is responding to coded energy of either character, the second decoding means being arranged so that the second auxiliary relay may be picked up only when the track relay is responding to coded energy of said second character, means operative when said first auxiliary relay is released to supply coded energy of said first character to the rails of said rearward section and when said first auxiliary relay is picked up to supply coded energy of said second character to the rails of said rearward section, means operative only when said rearward section is occupied to establish said second circuit, and a signal for exit end thereof, a code following track relay at,

the entrance end of said forward section having a winding receiving energy over the rails of said section, a first decoding means including a first auxiliary relay, a second decoding means including a second auxiliary relay, a first circuit controlled by the track relay for supplying energy to the first decoding means, a second circuit controlled by the track relay for supplying energy to the second decoding means, the first decoding means being arranged so that the first auxiliary relay is picked up when the track relay is responding to'coded energy of either character, the second decoding means being arranged so that the second auxiliary relay may be picked up only when the trackirelay is responding to coded energy of said second character, means operative when said first auxiliary relay is released to supply coded energy of said first character to the rails of said rearward section and when said first auxiliary relay is picked up to supply coded energy of said second character to the rails of said rearward section, means operative only when said rearward section is occupied and said first auxiliary relay is picked up to establish said second circuit, and a signal forsaid forward section controlled by said first and second auxiliary relays.

3 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 forward and a rearward track section, means,

governed by traffic conditions in "advance of said forward section for at one time supplying coded the first decoding means, a second circuit controlled by the track relay for supplying energy to the second decoding means, the first decoding means being arranged so that the first auxiliary relay is picked up when the track relay is responding to coded energy of either character, the second decoding means being arranged so that the second auxiliary relay maybe, picked up only when the track relay is responding to coded energy of said, secondcharacter, means operative when said first auxiliary relay is released to supply coded energy of said first character to the rails of said rearward section and when said first auxiliary relay is picked up to supply coded energy of said second character to the rails of said rearward section, a signal for said forward section including a lamp, said signal being operative when said second auxiliary relay is picked up and said lamp is lighted to provide a distinctive signal indication, and means operative when the rearward section is occupied to first establish said second circuit and after the expiration of a time interval long enough to enable the second auxiliary relay to become picked up to-establish a circuit to supply energy to said signal lamp.

4. 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 forward and a rearward track section, means governed by traific conditions in advance of said forward section for at one time supplying coded energy of a first character and at other times supplying'coded energy'o-f a second character to the rails of said forward section adjacent the exit end thereof, a code following track relay at the entrance end of said forward section having a winding receiving energy over the rails of said section, a first decoding means including a first auxiliary relay, asecond decoding means including a second auxiliary relay, a circuit controlled by the track relay for supplying energy to the first decoding means, a circuit controlled by the track relay forsupplying energy to the second decoding means, the first decoding means being arranged so that the first auxiliary relay is picked up when the track relay is responding to coded energy of either character, the second decoding means being arranged so that the second auxiliary relay may be picked up only when the track relay is responding to coded energy of said second character, means operative when said first auxiliary relay is released to supply coded energy of said first character to the rails of said rearward .section andv when said first auxiliary relay is picked up to supply coded energy of said second character to the rails of said rearward section, a signal for said forward section having aplurality of signal lamps for providing a plurality of different signal indications, a first supply circuit including a back contact ofsaid second auxiliary relay over which energy may be supplied to one lamp of said signal and a second supply circuit including a front contact of said second auxiliary relay over which energy may be supplied to another lamp of said signal, and means operative when the rearward section is occupied to first establish the circuit of said second decoding means and after the expiration of a time interval long enough to enable the second auxiliary relay to become picked up to also establish said first or said second supply circuit.

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 forward and a rearward track section, means governed by trafiic conditions in advance of said forward section for at one time supplying to the rails of said forward section energy of one code frequency and at another time supplying to the rails of said forward section energy of a second code frequency, a code following track relay for said forward section having a winding receiving energy over the rails of said section, a first and a second auxiliary relay associated with said track relay, means operative when said track relay is responding to coded energy of either code frequency to supply energy to said first auxiliary relay, means including a supply circuit controlled by the track relay for supplying energy to said second auxiliary relay, said means being operative to effectively energize said relay only when the track relay is responding to energy of said second code frequency, means operative according as the first auxiliary relay is released or picked up for supplying to the rails of said rearward section energy of said first or said second code frequency, means operative when and only when said rearward section is occupied to establish said supply circuit, and a signal for said forward section controlled by said first and second auxiliary relays.

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 forward and a rearward track section, means governed by traffic conditions in advance of said forward section for at one time supplying to the rails of said forward section energy of one code frequency and at another time supplying to the rails of said forward section energy of a second code frequency, a code following track relay for said forward section having a winding receiving energy over the rails of said section, a first and a second auxiliary relay associated with said track relay, means operative when said track relay is responding to coded energy of either code frequency to supply energy to said first auxiliary relay, decoding means operative only when energized and the track relay is responding to energy of said second code frequency to supply energy to pick up said second auxiliary relay, means operative according as the first auxiliary relay is released or picked up for supplying to the rails of said rearward section energy of said first or said second code frequency, means operative when and only when said rearward section is occupied and said first auxiliary relay is picked up to energized said decoding means, and a signal for said forward section controlled by said first and second auxiliary relays.

'7. 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 forward and a rearward track section, means governed by traffic conditions in advance of said forward section for at one time supplying to the rails of said forward section energy of one code frequency and at another time supplying to the rails of said forward section energy of a second code frequency, a code following track relay for said forward section having a winding receiving energy over the rails of said section, a first and a second auxiliary relay associated with said track relay, means operative when said track relay is responding to coded energy of either code frequency to supply energy to said first auxiliary relay, decoding means operative only when energized and the track relay is responding to energy of said second code frequency to supply energy to pick up said second auxiliary relay, means operative according as the first auxiliary relay is released or picked up for supplying to the rails of said rearward section energy of said first or said second code frequency, a semaphore signal for said forward section having an arm movable between a plurality of different positions and having a lamp which when lighted provides a signal indication of one of a plurality of different colors depending on the position of the signal arm, means controlled by said first and second auxiliary relays for effecting movement of said signal arm to its various positions, and means operative when said rearward section is occupied to energize said decoding means and to subsequently establish the circuit of said signal lamp after a time interval long enough to permit said second auxiliary relay to become picked up and for said signal arm to be moved from one of its positions to another.

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 forward and a rearward track section, means governed by traffic conditions in advance of said forward section for at one time supplying to the rails of said forward section energy of one code frequency and at another time supplying to the rails of said forward section energy of a second code frequency, a code following track relay for said forward section having a winding receiving energy over the rails of said section, a first and a second auxiliary relay associated with said track relay, means operative when said track relay is responding to coded energy of either code frequency to supply energy to said first auxiliary relay, decoding means operative only when energized and the track relay is responding to energy of said second code frequency to supply energy to pick up said second auxiliary relay, means operative according as the first auxiliary relay is released or picked up for supplying to the rails of said rearward section energy of said first or said second code frequency, a signal for said forward section comprising a member movable to a plurality of different positions and a lamp which when lighted provides a signal indication of one of a plurality of different colors depending on the position of said movable member, means controlled by said first and second auxiliary relays for moving said movable member to its various positions, and means operative when said rearward section is occupied to energize said decoding means and to subsequently establish the circult of said signal lamp after the expiration of a time interval long enough to permit said seccond auxiliary relay to 'become picked up and for said signal movable member to be moved from one to another of its positions.

9. 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 forward and a rearward section, means governed by traflic conditions in advance of the forward section for at one time supplying energy of one code frequency and at another time supplying energy of a second code frequency to the rails of said forward section, a code following track relayhaving a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay associated with said track relay, means eifective when said track relay is responding to coded energy of either code frequency to supply energy to the first auxiliary relay, means operative according as the first auxiliary relay is released or picked up to supply energy of said first or second code frequency to the rails of said rearward section, a transformer, means for supplying energy from said transformer to said second auxiliary relay and operative to efiectively energize said relay only when said transformer is intermittently energized at the rate which occurs when said track relay is responding to energy of said second code frequency, a source of direct current, a supply circuit including a contact of said track relay for supplying energy from said source to the input terminals of said transformer, means eifective when said rearward section is vacant to interrupt said supply circuit, and a signal for said forward section controlled by said first and second auxiliary relays,

FRANK H. NICHOLSON.

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