US2243726A - Railway signaling system - Google Patents

Description

G w. BAUGHMA-N 2,243,726 RAILWAY SIGNALING SYSTEM May 27, I941.

Filed March 8, 1940 IN NTOR "I 9&1226272.

Geo/rye BY r Patented May 27, 1941 res RARWAY SIGNALING SYSTEM Application March 8, 1940, SerialNo. 322,974

11 Claims. (01. 246-130) My invention relates to railway traific controlling apparatus of the type employing coded current in the track circuits thereof, and more particularly to the provision in a system of this character of improved track circuit detection means for the control of highway crossing signals or other apparatus.

Where a track section includes an intersection with a highway it is customary to divide the track section into subsections to facilitate control of the crossing signals which protect the intersection. On entrance of a train into the rearward or approach subsection operation of the crossing signals is initiated, while when the train vacates the rearward subsection it is desired to discontinue operation of the crossing signals without conditioning the signals governing movement of trains in the track section to display a proceed indication.

It has heretofore been proposed to provide in a system of this kind means operative when a train enters the forward or clearing sussection to supply to the track rails of the rearward subsection steady uncoded energy, and to provide means associated with the rearward subsection and operative on the supply of steady energy thereto to discontinue operation of the crossing signals.

If steady energy is supplied to a track circuit in which coded energy is normally employed, the

advantage of improved shunting sensitivity which results from the use of coded current in the track circuit is lost as long as steady energy is supplied to the track circuit. Accordingly a following train entering the track section at a time when steady energy is supplied thereto might not effectively shunt the track relay for the section with the result that operation of the crossing signals would not be started and users of the highway would not be warned of the approach of the train.

It is an object of my invention to provide an improved railway signaling system of the type employing coded current in the track circuits thereof to control the signals governing movement of trains through the track stretch, the system also employing coded current in the track circuits for detection purposes to thereby provide the same degree of shunting sensitivity at such times as is normally obtained in the track circuits.

A further object of my invention is to provide, 3

in a railway signaling system of the type employing coded current in the track circuits thereof to control the signals governing movement of trains through the track stretch, means to supply coded energy of a distinctive character to a track ciri cuit to detect occupancy of the section Without affecting the signals governing traflic in the track stretch.

Another object of my invention is to provide an improved railway signaling system having a track section having a track circuit including means responsive to coded current of one relative polarity for controlling the signals which govern movementof trains through the track section, and having means responsive to coded current of the other relative. polarity for detecting occupancy of the track section to thereby enable coded current to be employed to detect occupancy of the track section without interfering with the means controlling the signals governing trafiic in the track section.

A further object of my invention is to provide an improved signaling system of the type de-.

scribed and adapted for use in track stretches r where coded alternating current is supplied to the track rails of the track sections to actuate vehicle carried signal apparatus, the system being arranged so that when coded direct current of the polarity employed for detection purposes is supplied .to a track section coded alternating current will not be supplied thereto to thereby insure that at such times the vehicle carried signaling apparatus will be conditioned to provide its inost restrictive indication.

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

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

In the drawing the single figure is a diagram of a stretch of railway track equipped with coded signaling apparatus embodying my invention.

Referring to the drawing, there is shown therein a stretch of railway track having track rails l and 2 over which traific 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 track sections for signaling purposes. One of these sections includes an intersection with a highway and the rails of this section have insulated joints 3 therein to divide the section into subsections to facilitate control of the interlocking relay XR, which controls the crossing signals XS which protect the highway intersection. The two subsections are designated Al H and Bi 1T, while portions of two track sections are shown and are designated MT and I2T.

Each of the principal track sections has adjacent the entrance end thereof a wayside signal,

designated S with an appropriate prefix, for governing movement of trains in the track section. As shown the signals are of the familiar color light type, each having a green or clear lamp G, a yellow or caution lamp Y, and a red or stop lamp R. The invention, however, is not limited to a system employing this type of wayside signals, and any suitable signals may be employed. Furthermore, the invention is not limited to a signaling system employing wayside signals, but is equally applicable to a system which has cab signals only.

The rails of each of the track sections form a part of a track circuit to which direct current coded or periodically interrupted at either of a plurality of different frequencies is supplied at a point adjacent the exit end of the track section to control the wayside signals, while coded alternating current is also supplied to the track circuits to operate cab signaling apparatus carried by locomotives operating through the track stretch.

Each of the-track sections has adjacent the entrance end thereof a code following track relay TR having a winding receiving energy from the rails of the associated track section. The track relays are of a type which are responsive to direct current of one relative polarity only, while current of opposite relative polarities is employed in the track circuits of adjoining track sections to prevent improper operation of the track relay of one of the sections in the event the insulated joints separating the rails of the sections become defective.

The subsection BI IT is provided with an auxiliary code following track relay BI I TRA having its winding connected in series with that of the principal track relay BI ITR. The relays BI ITR rand BIITRA are arranged so that one relay responds to current of one polarity only and so that the other responds to current of the other polarity only.

The track relays IZTR, and BI I TR each have associated therewith decoding means selectively responsive to code following operation of the relay to control the associated signal, and to also control the supply of coded direct and alternating current to the rails of the adjoining track section in the rear. As shown the decoding means associated with each of these track relays comprises a decoding transformer DT, auxiliary relays H and J, a code transmitter CT, a track transformer TT, and a track battery TB.

The primary windings of the track transformers T are, supplied with alternating current from a suitable source, the terminals of which are designated BX and CX, while each of the track relays has associated therewith a source of direct current the terminals of which are designated B and C in the drawing.

The decoding means associated with the track relays IZTR and BIITR is not a part of this invention and any suitable means of this type may be employed.

The track relays AI ITR and BI ITR each have associated therewitha front contact repeater relay FSA and a back contact repeater relay BSA. The track relay AI ITR also has associated therewith a track transformer BI ITT, a code transmitter AI ICT, and a track battery BI ITB.

As shown the code transmitters I ICT and I ZCT have continuously operated contacts I88 and I5 which provide track circuit current of two code frequencies, namely, current of 180 interruptions per minute over the periodically closed contact I83, and current of '75 interruptions per minute over the periodically closed contact I5.

The code transmitter AIICT has one circuit making and breaking contact 28. While the coded direct current which is supplied to the rails of section BI IT for detection purposes may be of any desired frequency, it is preferred to employ a code frequency, such as 20 impulses per minute, which is substantially lower than the code frequencies employed in the control of the signals.

The equipment is shown in the condition which it assumes when the track stretch is vacant. At this time coded direct current of the code frequency is supplied to the rails of section I2T by the means, not shown, associated with the adjacent section in advance. This energy is of the polarity which is effective to produce code following operation of the track relay IZTR.

As a result of movement of contact 22 of the track relay IZTR, between its picked-up and released positions, the two end portions of the primary winding 2I of the decoding transformer I2DT are alternately energized with the result that energy is induced in the secondary windings 23 and 24 of the transformer. The contact 25 of the relay IZTR rectifies the current supplied from the secondary winding 23 of the transformer IZDT to the Winding of the relay I2H and the contacts of the relay IZH are maintained picked up.

As the relay IZTR is responding to energy of the 180 code frequency, the frequency of the current induced in the secondary winding 24 is such that suflicient energy is supplied through the resonant rectifier unit IZRU to maintain the contact of the relay IZJ picked up.

As contact 21 of relay IZH and contact 28 of relay IZJ are picked up, the circuit of the green lamp G of signal I2S is established and this lamp is lighted. As contact 39 of relay I2H is picked up, the circuit of the I88 contact of the code transmitter I2CT is established and the circuit of the track battery IZTB and of the secondary winding 32 of the track transformer IZTT is intermittently established so as to supply coded alternating and direct current of the 180 code frequency to the rails of the clearing section AI IT.

The coded alternating current supplied to the rails of section AIIT serves to control vehicle carried signal apparatus on trains traversing the track section, while the coded direct current effects operation of the track relay AI ITR.

On the supply of coded direct current to the track relay AIITR the contacts 35 and 36 are picked up and released. During the picked up periods of the contact 35 energy is supplied to the winding of relay AIIFSA, while during the released periods of contact 35 energy is supplied to the winding of relay AI IBSA over a circuit which includes front contact 38 of relay AI IFSA. A resistor 48 is connected across the terminals of the winding of relay AI IFSA to render the relay contacts slow to release, while contact 38 when picked up establishes a circuit to connect a resistor 4| across the terminals of the winding of the relay AI IBSA to render the contacts of this relay slow to release. Accordingly, as the track relay A] I TB. is responding to coded energy, the relays AI IFSA and AIIBSA are both energized and their contacts are picked up, while the contacts of these relays are slow enough in releasing to remain picked up during the intervals between the supply of impulses of energy to the relay windings.

As the contacts 43 and 44 of the relays AI IBSA are picked up, a circuit is established to supply direct current energy of normal relative polarity from the track battery BI ITB to the rails of the approach section BI IT during the released periods of the track relay contact 36. This circuit is traced from track rail 2 of section BI IT through wire 55 and front contact 44 of relay AIIBSA to one terminal of the track battery BI ITB, and from the other terminal of the battery through front contact 43 of relay Al IBSA, back contact 36 of track relay Al ITR, and wire 46 to track rail I of section BI IT.

The circuit for supplying direct current to the rails of the approach section BI IT is interrupted during the picked-up periods of the track relay contact 35. Accordingly energy of the same code frequency is supplied to the rails of section BI IT as is supplied to the track relay AI ITR.

During the picked up periods of the track relay contact 36 a circuit is established for supplying energy from the secondary winding 32 of the track transformer BIITT to the rails of section BIIT. This circuit is traced from rail 2 of section BI IT through wire 45 to one terminal of the transformer secondary winding 32, and from the other terminal of the winding 32 through front contact 36 of the track relay AI ITR and wire 46 to rail I of section BI IT.

The circuit for supplying alternating current to the rails of section BE IT is interrupted during the released periods of the track relay contact 36 with the result that the alternating current supplied to the rails of section BIIT is coded at the same code frequency as the direct current supplied to the track relay AI ITR.

From the foregoing it will be seen that when the track relay AIITR is responding to coded energy, impulses of direct current are supplied to the rails of section BI IT during the released periods of the track relay contacts, and that during the picked-up periods of the track relay contacts impulses of alternating current are supplied to the rails of section BI IT.

In addition it will be seen that during the picked-up periods of the track relay contacts a shunt circuit is established between the track rails I and 2 of section BE IT through the secondary winding 32 of track transformer BI ITT.

This circuit is of relatively low resistance and provides means to dissipate any charge built up between the track rails I and 2 by the supply of impulses of direct current thereto. As the track rails are shunted during the intervals between the supply of impulses of direct current energy thereto, the accumulation of a charge between the track rails which might interfere with operation of the track relays is prevented.

At this time as contact 48 of relay AI IBSA is picked up, the circuit of the winding 49 of interlocking relay XR is established and this winding is energized.

As the track stretch is assumed to be vacant, coded direct current supplied to the rails of section BIIT feeds to the track relays BI ITR and BIITRA and flows through the windings of these relays in series. As stated above, the track relays Bi iTR and Bi ITRA are arranged so that they respond to current of opposite relative polarities. are arranged so that only the relay BI ITR. will The relays Bi I'I'R. and BI ITRA respond to energy of the polarity which is supplied thereto when the contacts of the relay AI I BSA are picked up. Accordingly at this time th relay BI ITR responds to coded direct ourrent, while the contact of the relay BI ITRA remains in its released position.

As the contact 50 of relay BI ITRA remains As a result of code following operation of the track relay BIITR, energy is supplied through the decoding transformer BIIDT to the relays BI IE and BI IJ in the manner described in detail in connection with section IZT.

As the contacts of relays BI Ii-I and BI IJ are picked up, the circuit of the green or clear lamp G of signal IIS is established. In addition, as contact 3d of relay BIIH is picked up, the circuit for supplying coded alternating and direct current of the code frequency to the rails of section IBT is established.

The relay BI iH has another contact 5| which when picked up establishes a circuit to supply energy to the winding 53 of interlocking relay 253. As both windings of the relay XR. are energized, this relay maintains the crossing signals XS inactive.

Operation. of equipment on passage of a train in normal direction of tmfiic When a train moving in the normal direction of tralfic enters the approach section BI IT, the track relay BI ITR is shunted and no longer responds to coded energy. At this time the cab signal equipment carried by the locomotive responds to the alternating current of 180 code frequency supplied by the equipment associated with relay AIITR and provides the engineer with a clear signal.

As the relay BI ITR is shunted, energy is no longer supplied through the decoding transformer Bl iDT to the relays BI IE and BI IJ and the contacts of these relays become released.

As a result of release of contact 21 of relay iII-I, the circuit of the green lamp G of signal IIS is interrupted, and the circuit of the red or stop lamp R is established. As a result of release of contact 38 of relay BI IH, the circuit for supplying energy of the 180 code frequency to the rails of section I ET is interrupted and the circuit for supplying energy of the 75 code frequency is established.

In addition, as a result of the release of the contacts of relay BIIH, contact 5i interrupts the circuit for supplying energy to the winding 53 of interlocking relay XE. Accordingly, the armature controlled by this winding becomes released and eifects operation of the crossing signals XS to warn users of the highway of the approach of a train.

When the train advances far enough in the track stretch to enter the clearing section AI IT, the track relay AI iTR. is shunted and its contacts remain released. As contact 35 of relay AIiTR does not engage its front contact, en

of the contacts 43.

is established for supplying energy of the opposite or reverse relative polarity from the battery BI ITBto the rails of section BI IT. This circuit includes contact 20 of the code transmitter AI ICT and is traced from.- rail 2 of section BI IT through wire 45 and back contact 43 of relay AI IBSA to one terminal of the battery BI ITB, and from the other terminal of the battery through back contact 44 of relay AI IBSA, front contact 20 of the code transmitter AI'ICT, back contact 55 of relay AI IBSA, and wire $6 to rail I of section BIIT. This circuit is interrupted during the released periods of contact 20 of the code transmitter AI ICT, and the rate of operation of contact 20 is such as to close the circuit for supplying energy to the rails of section BI IT twenty times a minute and to provide the same number of intervals of substantially equal duration during which energy is not supplied to the rails of section BI IT.

During the released periods of contact 213 of the code transmitter AI ICT a circuit is established which shunts the rails of the section BI IT. This circuit is traced from track rail I of section BI IT through Wire 45, back contact 55 of relay AIIBSA, back contact 20 of code transmitter AI ICT, and wire 45 to rail 2 of section BIIT. Since the rails of section BII T are shunted during the intervals between the supply of impulses of current thereto, the accumulation of a charge between the track rails at this time is prevented.

As a result of release of the contacts of relay AIIBSA, contact 48 interrupts the circuit of winding 49 of interlocking relay XR. However, because of the internal construction of the re lay m, the armature controlled by winding 49 is prevented from moving all of the way to its released position since the armature controlled by winding 53 is already released.

As long as any portion of the train remains in the approach section BI IT, the track relays Bl ITR and BI I'IRA continue to be shunted, but as soon as the rear of the train vacates section BI IT, coded direct current supplied to the rails of the section feeds to the track relays BI ITR. and BI ITRA.

The polarity of the direct current impulses supplied at this time is such that the track relay BIITRA will respond to these impulses, while the relay BI I TR will not respond to these impulses and its contacts remain in their released positions.

As the contacts of the relay BI ITR remain in their released positions, the signal I IS continues to display its stop indication, while energy of the 75 code frequency continues to be supplied to the rails of section IElT.

On movement of the contact 59 of relay BI ITRA to its picked up position energy is supplied to the winding of relay BI IFSA, and the contact of this relay becomes picked up so that on movement of contact 58 to its released position energy is supplied to the winding of the relay BI IBSA. The relays BI IFSA and BI IBSA have snubbing resistors associated therewith to render the relay contacts slow in releasing, and these relays and the resistors are selected so that the relay contacts will remain picked up during the intervals between the supply of impulses of energy to the relay windings.

As a result of the supply of energy to the winding of relay BI IBSA, contact 55 of the relay becomes picked up and establishes a circuit to supply energy to the winding 53 of the interlocking relay XR. The armature controlled by this winding accordingly becomes picked up and operation of the crossing signals XS is discontinued, while, because of the internal construction of the relay, the armature controlled by the winding 49 continues to be prevented from moving to its released position.

When the train advances far enough to enter the track section I2T, the track relay IZTR is shunted and energy is no longer supplied through the decoding transformer IZDT to the windings of the relays IZH and IN. Accordingly the contacts of these relays become released and condition the signal I 2S to display its red or stop indication, while the energy supplied to the rails of the clearing section AIIT is changed from the to the 75 code frequency.

As long as a portion of the train remains in section AI IT, the track relay Al I TB is shunted, but when the rear of the train vacates the section, coded direct current of the 75 code frequency feeds to the winding of the track relay AI ITR and produces code following operation of the track relay contacts, and as a result the contacts of the relays AI IFSA and AI I BSA become picked up.

On picking up of the contacts 43 and 44 of relay AI I BSA, the circuit controlled by contact 20 of the code transmitter AI ICT for supplying energy of reverse relative polarity to the rails of section BI IT is interrupted, While the circuit is established for supplying energy of normal relative polarity to the rails of section BIIT during the released periods of the track relay contact 36.

In addition, as a result of picking up of the contacts of the relay AI IBSA, contact 55 interrupts the circuit controlled by code transmitter contact 20 for shunting the rails of the section BI IT, while contact 48 of relay AI IBSA establishes the circuit for supplying energy to the winding 49 of the interlocking relay XR. On the supply of energy to this winding the armature controlled by the winding is picked up and the relay is restored to its normal condition.

On movement of the track relay contact 36 to its picked-up position the circuit is established for supplying impulses of alternating current to the rails of section BI IT and for shunting the track rails of the section, as explained above.

At this time as the track relay AI ITR. is responding to energy of the 75 code frequency, the energy supplied to the rails of section BIIT is coded at this frequency.

On interruption of the supply of impulses of direct current of reverse relative polarity to the rails of section BI IT the track relay BI ITRA ceases to respond to coded energy, while on the supply of impulses of direct current of the normal relative polarity to the rails of section BI IT the track relay BI ITR responds to coded energy and energy is supplied through the decoding transformer BI IDT to the winding of the relay BI IH.

It will be seen that on each movement of the contacts of the track relay BI ITR to their picked-up or released positions there is a, change in energization of the decoding transformer primary winding, and that contact 25 of the relay establishes a circuit to supply an impulse of energy from the transformer secondary winding to the winding of relay BI IH.

The relay BI IH and the transformer BIIDT are selected and proportioned so that the contacts of the relay when released will not become picked up as a result of the supply of one impulse of energy from the transformer to the relay winding, or on the continued supply of impulses of energy at the frequency at which they are supplied when the track relay is responding to energy of a code frequency substantially lower than the 75 code frequency, such as, for example, energy of the 20 code frequency.

The relay BHH and the transformer Bl IDT are also selected and proportioned so that the relay contacts when released will become picked up on the supply in rapid succession of a plurality of impulses of energy from the decoding transformer, such as are supplied to the relay winding when the track relay is responding to energy of the '75 code frequency.

Since at this time the track relay Bl lTR is responding to energy of the '75 code frequency, impulses of energy are supplied to the winding of relay Bill-I which are effective to pick up the relay contacts after a plurality of such impulses of energy have been supplied to the relay winding. As the track relay Bl [TR is responding to energy of relatively high code frequency, and since impulses of energy are supplied to the winding of the relay Bl EH in both the picked-up and released positions of the track relay contacts, the plurality of impulses of energy necessary to pick up the contacts of the relay BI [H are supplied to the winding of the relay BHH Very quickly after initiation of code following operation of the track relay Bl ITR.

It will be seen also that on initiation of code following operation of the track relay AHTR the supply of energy of reverse relative polarity to the rails of section Bl IT is continued until the contacts of relay Al I BSA become picked up,

and that on picking up of the contacts of relay Al IBSA the supply of energy of normal relative polarity to the rails of section Bl IT is initiated immediately. Accordingly, there is no time delay between cessation of code following operation of the track relay Bl lTRA and initiation of code following operation of the relay Bl ITR.

Because of the slow releasing characteristic of the relay BllFSA a short time interval must elapse after the track relay BHTRA ceases to follow code before the contacts of the relay BI lFSA become released, while the contacts of the relay Bl lBSA release soon thereafter.

On release of the contact 56 of relay Bl IBSA the circuit which it controls for supplying energy to the winding 53 of the interlocking relay XR is interrupted. However, as pointed out above, at this time the contacts of the relay Bl IH become picked up promptly, and the various parts of the equipment are arranged so that the contact El of relay BllH becomes picked up to establish the circuit which it controls before the contact of relay Bl IBSA becomes released. Accordingly on the change in the supply of energy to the rails of section Bl lT from energy of reverse relative polarity to energy of normal relative polarity there is no interruption in the supply of energy to the winding 53 of the interlocking relay XR, and this relay, therefore, maintains the crossing signals XS inactive.

At this time as the track relay Bl lTR is responding to coded energy of the 75 code frequency, the contacts of the relay Bl IH are picked up, but insufficient energy is supplied through the resonant unit Bl IRU to the winding of the relay Bl U to pick up the contacts of this relay. As the contact 28 of relay Bl U is released, and as the contacts of the relay BHH are picked up, the signal l is is conditioned to display its yellow or caution indication, while contact 30 of relay B! IH interrupts the circuit for supplying energy of the 75 code frequency to the rails of section I01 and establishes the circuit for supplying energy of code frequency thereto.

When the train vacates section I2T, energy of the 75 code frequency supplied to the rails of this section by the means associated with the track relay of the adjacent section in advance feeds to the' relay EZTR and the equipment associated with this relay conditions the signal |2S to display its caution indication, while the energy supplied to the rails of section AI IT is changed from 75 to 180 code frequency.

On this change in the frequency of the energy supplied to the rails of section AI IT there is an increase in the rate of operation of the contacts of the track relay Al I'IR, and a corresponding change in the frequency of the code supplied to the rails of section BIIT. Accordingly the contacts of relay BII'IR operate at a higher rate and sufficient energy is supplied through the resonant unit Bl lRU to pick up the contact of relay Bl lJ withthe result that signal HS displays its clear indication instead of its caution indication.

From the foregoing, it will be seen that the system provided by this applicant normally employs coded direct current in the track circuits of the various track sections to control the signals governing movement of trains through the track stretch and to normally maintained the crossing signals inactive.

It will be seen also that on passage of a train through the track stretch, that when the train enters the clearing subsection in advance of the crossing, the supply of coded energy of normal relative polarity to the rails of the approach subsection in the rear of the crossing is out off, while coded energy of reverse relative polarity .is supplied to the rails of the rearward or approach subsection.

The track circuit apparatus associated with the rearward subsection and controlling the signals governing traflic in the track stretch will not respond to energy of this relative polarity, and, therefore, the wayside signal controlled by this apparatus continues to display its most restrictive indication.

However, the approach subsection in the rear of the intersection has means including an auxiliary track relay which is responsive to the supply of coded energy of reverse relative polarity, and is operative to discontinue operation of the highway crossing signals and to thereafter maintain the crossing signals inactive as long as coded energy of reverse relative polarity continues to be supplied to the auxiliary track relay.

If a second train enters the rearward or approach subsection at a time when coded current of reverse relative polarity is being supplied thereto, the auxiliary track relay will be shunted and the relays Bl IFSA and Bi lBSA controlled thereby will become deenergized and contact 56 of relay Bl lBSA will interrupt the circuit for supplying energy to the winding 53 of the interlocking relay XR so that this relay will initiate operation of the crossing signals XS to warn users of the highway of the approach of the train.

It will be seen that at this time the shunting sensitivity of the track circuit of the rearward subsection is determined by the code following auxiliary track relay BHTRA with the result that the shunting sensitivity of the track circuit is the same when energy is supplied to the track circuit to discontinue operation of a crossing signal as it is when energy is supplied to the track circuit to control the signals governing trafiic in the track stretch.

In addition it will be seen that when coded direct current of reverse relative polarity is supplied to the approach section that the supply of coded alternating current to the rails of the section is interrupted so that if a train enters the subsection the cab signal apparatus on the locomotive Will display its most restrictive indication.

Furthermore, it will be seen that the frequency of the coded current supplied to the rails of the subsection in the rear of the crossing for the purpose of discontinuing operation of a crossing signal is much lower than the frequency of the code employed for the control of the traflic governing signals. If for any reason the track relay BIITR should respond to the energy of this low code frequency, insufiicient energy would be supplied through the decoding transformer BI IDT to the relay BI II-I to pick up the relay contacts and the signal II S, therefore, would continue to display its stop indication. Similarly, if a train should enter the rearward subsection at a time when the forward subsection is occupied,'the cab signal equipment on the locomotive would not respond to energy of this low code frequency to provide a proceed indication, even if for any reason coded alternating current were supplied to the rails of the track section.

Operation of equipment on movement of a train through the track stretch in the reverse direction The system provided by this invention is arranged so that the crossing signals and the traffic energy of the 180 code frequency and the signals I28 and IIS are conditioned todisplay their green or clear indications,

When the train enters the adjacent section in advance of section IZT, the energy supplied to the rails of section I2T is changed from 180 to 75 code frequency with the result that signal IZS is conditioned to display its yellow or caution indication, while energy of 180 code frequency continues to be supplied to the rails of section AI IT.

When the train enters section IZT, the track relay IZTR is shunted and the signal IZS is conditioned to display its red or stop indication, while the energy supplied to the section in the rear is changed from 180 to '75 code frequency. The track relay AIITR responds to the lower code frequency and repeats the supply of ener y of the 75 code frequency to the rails of section BI IT, while the signal H is conditioned to display its yellow or caution indication instead of its green or clear indication.

At this time as the track relays AIITR and BI ITR are responding to coded energy, the circuits are established to supply energy to both of the windings of the interlocking relay XR and this relay maintains the crossing signal XS inactive.

When the train advances into section AIIT, the track relay of this section is shunted and its contacts thereafter remain in their released positions with the result that energy is not supplied to the winding of relay AIIFSA and the contacts of this relay become released, thereby interrupting both the circuit of the winding of relay AI IBSA and of the snubbing resistor 4| so that the contacts of the relay AIIBSA become released. v 5 I I 1 On release of contact 48 of relay AI IBSA the circuit of the Winding 49 of the interlocking relay XR. is interrupted, and the armature controlled by this winding becomes released and initiates operation of the crossing signals XS.

It will be seen that on shunting of the track relay AI I TR the contacts of this relay move to their released positions, if they are not already in that position. On movement of the track relay contacts to their released positions the supply of energy to the winding of the relay Al IFSA is cut off, while contact 36 establishes the circuit to supply energy to the rails of section BI IT. This energy feeds to the track relay BI ITR. and picks up the contacts of the track relay with the result that there is a change in energization of the primary winding of the decoding transformer BI IDT and an impulse of energy is supplied to the winding of the relay BI IH. The operation of the equipment is such, therefore, that on shunting of the track relay AI ITR an impulse of energy is supplied to the winding of the relay BI IH subsequent to the interruption of energy to the Wind'- ing of the relay AI I FSA.

As a result of this supply of energy to the winding of the relay BI I H, the contacts of the relay are maintained picked up, and contact 5| maintains the circuit for supplying energy to the winding 53 of the interlocking relay XR. The relay BI IH is of a type the contacts of which are slow in releasing and this relay is selected so that its contacts wi1 l remain picked up until after the contacts of the relay AIIBSA become released.

The contacts of relay AI IBSA release very soon after the contacts of the relay AI IFSA release as the circuit of the snubbing resistor 4| is interrupted on release of the contacts of relay AI IFSA. and release of the contacts of the relay BI IH need not be delayed long after the release of the contacts of relay AI IFSA to insure that the circuit of the winding 53 of the interlocking relay XR will not be interrupted until after the contact 48 of relay AI IBSA becomes released to interrupt the circuit of the winding 49 of the interlocking relay )3.

Since the winding 49 of the relay XR is deenergized before the winding 53 is deenergized, the armature controlled by the Winding 49 releases first and subsequent release of the armature controlled by the winding 53 will not interfere with the control of the crossing signals.

On release of the contacts of the relay AI IBSA the circuit which includes a back contact of the track relay for supplying energy to the rails of section BI IT is interrupted, and the circuit for supplying coded energy of reverse relative polarity to the rails of section BI IT is established. Accordingly coded current of reverse relative polarity is supplied to the rails of section BI I T and the auxiliary track relay BI ITRA responds to this energy, while the contacts of the track relay Bl I TR remain released.

As the contacts of relay BIITR remain re leased, energy is no longer supplied through the decoding transformer 13! IDT to the winding of the relay Bl IE and the contacts of relay Bl iH become released to condition the signal HS to display its red or stop indication, and to change the energy supplied to the section in the rear from 180 to 75 code frequency. In addition, contact i interrupts the circuit of the winding 53 of, the interlocking relay XR, and the armature controlled by this winding moves toward its released position. However, as the armature controlled by the winding 49 is already in the released position, the armature controlled by winding 53 is prevented from moving all of the way to its released position. i

As a result of code following operation of the auxiliary track relay Bi lTRA, energy is supplied to the windings of the relays BHFSA and BHBSA and contact 56 of relay BHBSA be"- comes picked up to establish a circuit to supply energy to the winding 53 of the interlocking relay XR. Accordingly the armature controlled by the winding 53 becomes picked up, while the armature controlled by winding 49 remains in its released position and maintains the crossing sign'als active.

From the foregoing it will be seen that when a train traveling in the reverse direction of traffic enters section A! iT, the supply of energy to the winding $9 of the interlocking relay XR. is cut off and that this relay initiates operation of the crossing signals. In addition at this time the supply of energy of normal polarity to the section Bi ITR. is cut off so that energy is no longer supplied to: the winding of the relay Bl 11-1, but

that the contacts of. the relay Bl lH remain picked up long enough to maintain the supply of energy to the winding 53 of the interlocking relay XR, until after the winding i9 is cleenergized so that operation of the crossing signals is controlled by the armature which is controlled by the winding 49.

When the train advances far enough in the track stretch to enter section BUT, the relay Bl iTRA is shunted and ceases to follow code with the result that the contacts of relays Bl IFSA and Bi iBSA become released. On release of contact of relay Bi iBSA the supply of energy to the winding 53 of the interlocking relay XR is interrupted. The armature controlled by this winding,

therefore, moves towards its released position, but

is prevented from moving all of the way to that position since the other armature of the relay is already in its released position.

7 When the rear of the train clears section l2T, the track relay of, this section responds to coded energy of the 180 code frequency, and the signal E28 is conditioned to display its clear indication, while energy of the 180 code frequency is supplied to the rails of section Al IT.

When the rear of the train vacates section AH'I, coded energy feeds to the track relay Al ITR and produces code following operation of the relay so that the windings of relays A! iFSA and AHBSA are energized. On picking up of the contacts of the relay AHBSA the circuit for supplying coded energy of reverse relative polarity to the rails of section BHT is interrupted, while the circuit for supplying coded current of normal relative polarity to section Bi ET is established.

In addition, on picking up of the contacts of the relay Ai iBSA contact 48 establishes the circuit to supply ene'rggy to the winding 49 of the interlocking relay XRL. Accordingly the armature controlled by this winding becomes picked up and discontinues operation of the crossing signals XS, while because of the internal construction of the relay the armature controlled by the other winding of the relay is prevented from moving to its released position on picking up of the armature controlled by winding 49.

As long as any portion of the train remains in section Bi iT, the track relays for the section continue to be shunted, but when the rear of the train vacates the section, coded direct current of normal relative polarity feeds to the track relay B! iTRand produces code following operation of th relay. As a result, energy is sup plied through the decoding transformer Bl IDT to the windings of the relays Bi HI and BHJ and the contacts of these relays become picked up to establish the circuit of the green or clear lamp of signal HS. I

In addition, on picking up of the contacts of the relay Bi iI-I the energy supplied to the rails of section GT is changed from '75 to code frequency, while contact 5| establishes the circult to supply energy to the winding 53 of the interlocking relay XR and the armature controlled by this winding becomes picked up.

The system provided by this invention employs polarized direct current in the track circuits, and the current employed in adjoining track circuits may be of opposite relative polarity to prevent improper operation of the signaling system in the event theinsulated joints separating two sections are defective so that energy from one track section feeds across the defective joint to the rails of the adjoining section. With this arrangement energy feeding feeding from the rails of one section across a defective joint to the rails of the adjoining section will be of the polarity opposite to that which is employed in the section to which the energy feeds, and since the code following track relays will respond to energy of one polarity only, they will not respond to energy supplied from the adjoining track circuits since it is of the Wrong polarity.

Where the rails of a track section are normally supplied with coded energy of one relative polarity for the purpose of controlling the signals governing traffic in the stretch, and at other times are supplied with coded energy of the other relative polarity for detection. purposes, as is the case in the approach section Bl IT, it is necessary to provide means energized from the rails of the section and responsive to cur-- rent of both polarities;

Accordingly, if energy from section l'fiT feeds across defective joints to the rails of section Bi 5T, the track circuit apparatus of section Bl IT will respond to this current.

The equipment associated with section BHT may be arranged so that either one of the two track relays will not respond to energy of the polarity supplied from the rails of section HIT, but the preferred arrangement is that in which the track relay Bi lTR does not respond to this energy. If, therefore, the insulated joints separating the sections MT and BHT are defective so that coded energy from section iiiT feeds to the rails of section BUT, the track relay Bl l'IR will not respond to this energy and the signal US will not be improperly conditioned to display a proceed indication at times when section Bi PI is occupied.

The energy which feeds over defective joints fiorr'i section EST to the rails or section BHT will effect operation of the track relay BI I'I'RA so that the windings of the relays BI IFSA and BIIBSA are energized and contact 56 of relay B! IBSA is picked up and establishes the circuit in the normal direction the track relays BI ITR and BI I TRA are shunted when the train enters section BI IT, and operation of the crossing signals XS is initiated as explained above. The energy from section IIiT feeding across the defective joints is not effective to operate the track relay Bi I'I'RA until the rear of the train is located some distance in advance of the entrance end of the sec-tion. Accordingly the crossing signals will be operated for a period prior to the time at which the train reaches the highway intersection, and users of the highway will have an indication of the approach of the train.

' Since coded current of both relative polarities is supplied to the rails of section BI IT, if the joints separating the rails of this section from section AI IT become defective, energy of one or the other polarity supplied to the rails of section BI IT will effect operation of the track relay AI ITR.

In the preferred embodiment the equipment is arranged so that the track relay Al I TR Will respond to energy of the polarity employed in the track section B! IT for detection purposes. When energy of this polarity is supplied to the rails of section BIIT, the section AIIT is occupied so that energy supplied at the exit end of section AIIT does not feed to the track relay AIITR. If energy of reverse relative polarity feeds over defective joints to the relay AIITR, the relay will respond to the coded energy until the contacts of relay AI IBSA become picked up. This interrupts the supply of energy to section BI IT until the contacts of relay AtIBSA become released, whereupon the cycle is repeated. As a result, energy of the code frequency is intermittently supplied to the rails of section BIIT and there is no possibility that the signal lis will be improperly conditioned to display a proceed indication.

From the foregoing it will be seen that this invention provides an improved railway signaling system in which coded direct current of one relative polarity is employed in a track circuit to control the traffic governing signals, while coded direct current of the other relative polarity is employed in the track circuit at times for detection purposes.

While the invention has been illustrated and described in connection with the control of a highway crossing signal, it should be understood that the invention is not limited to use in this connection and that it may be employed wherever it is desired to ascertain occupancy of a track section.

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

Having thus described my invention, what I claim is:

1..In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into successive track sections, one of said sections including an intersection with a highway, the rails of said section having insulated joints therein adjacent the intersection to divide the section into a forward and a rearward subsection, means governed by traffic conditions in advance of the section for selectively supplying to the rails of the forward subsection energy coded at either of a plurality of different frequencies, a code following electroresponsive device receiving energy from the rails of the forward subsection, means responsive to code following operation of said device for supplying to the rails of the rearward subsection direct current of one relative polarity coded at the same frequency as the energy supplied to said device, means controlled by said device and operative when said device is not responding to coded energy to supply to the rails of the rearward subsection coded direct current of the other relative polarity, a first and a second code following electroresponsive device receiving energy from the rails of the rearward subsection, the first device being responsive to direct current of said one relative polarity only and controlling means governing the supply of coded current to the rails of the adjacent section in the rear of the rearward subsection, the second device being responsive to the supply of direct current of the other relative polarity, a crossing signal protecting said highway intersection, means responsive to code following operation of said first device for maintaining said crossing signal inactive, and means responsive to code following operation of said second device for also maintaining said crossing signal inactive.

2. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into successive track sections, one of said sections including an intersection with a highway, the rails of said section having insulated joints therein adjacent the intersection to divide the section into a forward and a rearward subsection, means governed by trafiic conditions in advance of the section for selectively supplying to the rails of the forward subsection energy coded at either of a plurality of different frequencies, a code following electroresponsive device receiving energy from the rails of the forward subsection, means responsive to code following operation of said device for supplying to the rails of the rearward subsection direct current of one relative polarity coded at the same frequency as the energy supplied to said device, means controlled by said device and operative when said device is not responding tocoded energy to supply to the rails of the rearward subsection coded direct current of the other relative polarity, a first and a second code following electroresponsive device receiving energy from the rails of the rearward subsection, the first device being responsive to direct current of said one relative polarity only and controlling means governing the supply of coded current to the rails of the adjacent section in the rear of the rearward subsection, the second device being responsive to the supply of direct current of the other relative polarity only, a crossing signal protecting said highway intersection, means responsive to code following operation of said first device for maintaining said crossing signal. inactive, and means responsive to code following operation of said second device for also maintaining said crossing signal inactive.

3. .In a coded railway signaling system, in combination, a stretch of railway track having a pair of a plurality of different frequencies, a code following electroresponsive device receiving energy from the rails of the forward subsection, means responsive to code following operation of said device for supplying to the rails of the rearward subsection direct current of one relative polarity coded at the same frequency as the energy supplied to said device, means controlled by said device and operative when said device is not responding to coded energy to supply to the rails of the rearward subsection coded direct current of the other relative polarity, a. crossing signal protecting said intersection, and means receiving energy from the rails of said rearward subsection, said means being operative when and only when responding to coded direct current of either relative polarity to maintain the crossing signal inactive, said means being operative when not responding to coded energy of said one relative polarity to establish a first supply circuit for supplying energy of one code frequency to the rails of the section in the rear of said rearward subsection and being operative when and only when responding to coded direct current of said one relative polarity to interrupt said first supply circuit and to establish a second supply circuit for supplying to the rails of the section in the rear of the rearward subsection energy of. a second code frequency.

4. In a coded railway signaling system, in combination, a stretch of railway track havinga pair of track ra ls divided by insulated joints into successive track sections, one of said sections including an intersection with a highway, the rails of said one section having insulated joints therein adjacent the intersection to divide the section into a forward and a rearward subsection, means governed by traffic conditions in advance of the section for selectively supplying to the rails of the forward subsection energy coded at either of a plurality of different code frequencies, a code following track relay for the forward subsection having a winding receiving energy from the rails of said forward subsection, a first supply circuit through which direct current of one relative polarity may be supplied to the rails of the rearward subsection, a second supply circuit through which alternating current may be supplied to the rails of the rearward subsection, said first and second supply circuits each including a contact of said track relay whereby when said track relay is responding to coded energy each of said supply circuits is interrupted at rates such that the energy supplied through said supply circuits is coded at the same frequency as the energy supplied to said track relay, a third supply circuit through which direct current of the other relative polarity may be supplied to the rails of the rearward subsection, means for periodically interrupting said third supply circuit, means responsive to and operative when and only when rails of said rearward subsection, said means being operative when and only when supplied with coded direct current of either relative polarity to maintain said crossing signal inactive, said means being operative when not sup-plied with vcoded energy of said one relative polarity to establish a circuit to supply energy of a first code frequency to th rails of the adjacent section in the rear of said rearward subsection and being operative only on the supply of coded direct current of said one relative polarity to cut off the supply of energy of the first code frequency and to establish a circuit to supply coded energy of a second code frequency to the rails of th adjacent section in the rear of said rearward subsection.

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 successive track sections, one of said sections including an intersectionwith a highway, the rails of said one section having insulated joints therein adjacent the intersection to divide the section into a forward and a rearward subsection, means governed by traffic conditions in advance of the section for selectively supplying to the rails of the forward subsection energy coded at either of a plurality-of diiferent code frequencies, a code following track relay for the forward subsection having a winding receiving energy from the rails of said subsection, an auxiliary relay associated with said track relay, means responsive to code following operation of said track relay for supplying energy to the winding of said auxiliary relay, said auxiliary relay being operative when energized to establish a first supply circuit through which direct current of one relative polarity may be supplied to the rails of the rearward subsection and being operative when not energized to establish a second supply circuit through which direct current of the other relative polarity may be supplied to the rails of the rearward subsection, the first supply circuit including a contact of the track relay whereby energy supplied through said circuit is coded at the same frequency as the energy supplied to said track relay, means for intermittently interrupting the second supply circuit to code the current supplied through said circuit, a crossing signal protecting said intersection, means receiving energy from the rails of the rearward subsection and operative on the supply of coded direct current of either relative polarity to maintain said crossing signal inactive, said means being operative when not supplied with coded energy of said one relative polarity to establish a circuit to supply energy of a first code frequency to the rails of the adjacent section in the rear of said rearward subsection and being operative when and only when coded direct current of said one relative polarity is supplied thereto to cut off the supply of energy of the bination, a stretch of railway track having a pair of track rails divided by insulated joints into successive track sections, one of said sections including an intersection with a highway, the rails of said one section having insulated joints therein adjacent the intersection to divide the section into a forward and a rearward subsection, means governed by traflic conditions in advance of the section for selectively supplying to the rails of the forward subsection energy coded at either of a plurality of different code frequencies, a code following track relay for the forward subsection having a winding receiving energy from the rails of said subsection, an auxiliary relay associated with said track relay, means responsive to code following operation of said track relay for supplying energy to the winding of said auxiliary relay, said auxiliary relay being operative when energized to establish a first supply circuit through which direct current of one relative polarity may be supplied to the rails of the rearward subsection and to also establish a first shunt circuit by means of which connection may be established between the rails of the rearward subsection, each of said circuitsincluding a contact of the track relay and being arranged so that one circuit is established in one position of the track relay contact and the other circuit is established in the other position of the track relay contact, said auxiliary relay being operative when deenergized to establish a second supply circuit through which direct current of the other relative polarity may be supplied to th rails of the rearward subsection and to also establish a second shunt circuit by means of which connection may be established between the rails of the rearward subsection, means for alternately interrupting said second supply circuit and said second shunt circuit at a predetermined rate, sad means being operative to interrupt each of said circuits before establishing the other of said circuits, a crossing signal protecting said intersection, and means receiving energy from the rails of the rearward subsection and operative on the supply of coded direct current of either relative polarity to maintain the crossing signal inactive, said means being operative when not supplied with coded direct current of said one relative polarity to establish a circuit to supply coded energy of a first code frequency to the rails of the adjacent section in the rear of said rearward subsection and being operative when and only when supplied with coded direct current of said one relative polarity to cut off the supply of energy of the first code frequency and to establish a circuit to supply energy of a second code frequency to the rails of the adjacent section in the rear of said rearward subsection.

'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 successive track sections, one of said sections including an intersection with a highway, the rails of said one section having insulated joints therein adjacent the intersection to divide the section into a forward and a rearward subsection, means governed by traiiic conditions in advance of the section for selectively supplying to the rails of the forward subsection energy coded at either of a plurality of different code frequencies, a code following track relay for the forward subsection having a winding receiving energy from the rails of said subsection, an auxiliary relay associated with said track relay, means responsive to code following operation of said track relay for supplying energy to the winding of said auxiliary relay, said auxiliary relay being operative when and only when energized to establish a first supply circuit through which direct cur-- rent of one relative polarity may be supplied to the rails of the rearward subsection and being operative when and only when deenergized to establish a second supply circuit through which direct current of the other relative polarity may be supplied to the rails of the rearward subsection, each of said supply circuits having associated therewith means for periodically interrupting said circuit to thereby supply coded energy to the rails of the rearward subsection through said supply circuit, a crossing signal protecting said intersection, and means receiving energy from the rails of the rearward subsection and operative on the supply of coded direct current of either relative polarity to maintain the crossing signal inactive, said means being operative when not supplied with coded direct current of said one relative polarity toestablish a circuit to supply coded energy of a first code frequency to the rails of the adjacent section in the rear of said rearward subsection and being operative when and only when supplied with coded direct current of said one relative polarity to cut off the supply of energy of the first code frequency and to establish a circuit to supply energy of a second code frequency to the rails of the adjacent section in the rear of said rearward subsection.

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 successive track sections, one of said sections including an intersection with a highway, the rails of said one section having insulated joints therein adjacent the intersection to divide the section into a forward and. a rearward subsection, means governed by traflic conditions in advance of the section for selectively supplying to the rails of the forward subsection energy coded at either of a plurality of different code frequencies, a code following track relay for the forward subsection having a winding receiving energy from the rails of said subsection, an auxiliary relay associated with said track relay, means responsive to code following operation of said track relay for supplying energy to the winding of said auxiliary relay, said auxiliary relay being operative when and only when energized to establish a first supply circuit through which direct current of one relative polarity may be supplied to the rails of the rearward subsection and being operative when and only when deenergized to establish a second supply circuit through which direct current of the other relative polarity may be supplied to the rails of the rearward subsection, each of said supply circuits having associated therewith means for periodioally interrupting said circuit to thereby supply coded energy to the rails of the rearward subsection through said supply circuit, the rearward subsection having a first and a second code following track relay each having a winding receiving energy from the rails of said section, said first track relay being responsive only to direct current of said one polarity, said second track relay being responsive to direct current of the other polarity, a crossing signal protecting said highway intersection, means responsive to code following operation of either of said track relays for maintaining said crossing signal inactive, and means responsive to code following operation of said first track relay for controlling the supply o-f coded energy to the rails of the adjoining section in the rear of said rearward subsection, said means being operative when said first track relay is not responding to coded energy to establish a circuit to supply energy of a first code frequency and being operative when said first track relay is responding to coded energy to establish a circuit supply energy of a second code frequency to the rails of said adjoining section in the rear of said rearward subsection.

9. In combination, a stretch of railway track intersected by a highway and comprising a signal approach section and a signal clearing section, a crossing signal for the intersection, means efiective when said clearing section is unoccupied for supplying to the rails of the approach section train governing code comprising impulses of unidirectional current of one relative polarity, means responsive to entrance of a train into said clearing section for interrupting the supply of train governing code to the rails of said approach section and for supplying thereto detection code comprising impulses of unidirectional current of the other relative polarity, a first and a second electroresponsive device associated with said approach section, each of said devices having a winding receiving energy over the rails of the said approach section, the first device being responsive only to the supply of current of said one relative polarity and the second device being responsive to the supply of current of the other relative polarity, whereby said first device responds only to the train governing code and the second device responds to the detection code, and means responsive to code following operation of either of said devices for maintaining said crossing signal inactive, whereby said signal is inactive when the approach and clearing sections are unoccupied and is rendered active on entrance of a train into the approach section and is again rendered inactive when the train advances into the clearing section and vacates the approach section.

10. In combination, a stretch of railway track intersected by a highway and comprising a signal approach section and a signal clearing section, a crossing signal for the intersection, means effective when said clearing section is unoccupied to supply to the rails of the approach section train governing code comprising impulses of unidirectional current of one relative polarity, means responsive to entrance of a train into said clearing section for interrupting the supply of train governing code to the rails of said approach section and for supplying thereto detection code comprising impulses of unidirectional current of the other relative polarity, and electroresponsive means receiving energy from the rails of said approach section and responsive to the supply of coded energy of either relative polarity to maintain the cross signal inactive, whereby said signal is inactive when the approach and clearing sections are unoccupied and is rendered active on entrance of a train into the approach section and is again rendered inactive when the train advance into the clearing section and vacates the approach section.

11. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into successive track sections including adjoining forward and rearward sections, the forward section including an intersection with a highway and being divided into an approach and a clearing subsection, a crossing signal for said intersection, means effective when the clearing subsection is unoccupied to supply to the rails of the approach subsection train governing code comprising impulses of unidirectional current of one relative polarity, means responsive to entrance of a train into said clearing subsection for interrupting the supply of train governing code to the rails of said approach subsection and for supplying thereto detection code comprising impulses of unidirectional current of the other relative polarity, and electroresponsive means receiving energy from the rails of said approach section, said means being operative on the supply thereto of either train governing or detection code to maintain the crossing signal inactive, said means also being operative when not supplied with train governing code to efiect the supply of train governing code of a first character to the rails of said rearward section and being operative when supplied with train governing code to efiect the supply of train governing code of a second character to the rails of said rearward section, whereby said crossing signal is inactive and train governing code of the second character is supplied to the rails of said rearward section when said approach and clearing subsections are unoccupied, and on entrance of a train into the approach subsection the signal is rendered active and train governing code of the first character is supplied to the rails of said rearward section, andwhereby the signal is again rendered inactive when the train advances into the clearing subsection and vacates the approach subsection while train governing code of the first character is supplied to the rails of the rearward section until the train vacates the clearing subsection and thereafter train governing code of the second character is supplied to the rails of said rearward section.

GEORGE W. BAUGHMAN.

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