US2409044A - Railway signaling apparatus - Google Patents

Description

Get. 8, 1946. JEROME A 2,409,044

RAILWAY'SIGNALIN? APPARATUS Filed Jan. 9, 1943 9 Sheets- Sheet 1 IN V ENTOR Amizurll .Japome.

1115 ATTORNEY A. 1.. JEROME RAILWAY SIGNALING APPARATUS Filed Jan. 9, 1943 9 Sheets-Sheet 2 6 W5 B I m 5 x A72 2 L M Cen12 on g *7 46JCL- 2 15' v 19 M F4 4 2' I) 22 5) Y /66 zaj w 67 Li] 2 L] a $67M A6T\ Z1 B6T- ii V Fm] up 157' [MUD] v v INVENTOR AmizurlhJepome. "aim 15 ATTORNEY Oct. 8, 1946.

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Filed Jan. 9, 1943 9 Sheets-Sheet 9- QQQQQ! A.

N .L Q N k is; B Q N i 2; E s b a a? \I INVENTOR i -Arzl2aPL.JePome. f r4 av-am N H15 ATTORNEY Patented Oct. 8, 1946 RAILWAY SIGNALING APPARATUS Arthur L. Jerome, Edgewood, Pa., assignor to The Union Switch & Signal Company,

Swissvale,

Pa., a corporation of Pennsylvania Application January 9, 1943, Serial No. 471,838

17 Claims.

My invention relates to railway signaling apparatus and particularly to improved means for indicating occupancy of a portion of a track stretch which may not coincide with the track sections into which the track stretch is divided for the control of trafilc through the track stretch.

It is customary to divide the track rails of a track stretch into track sections by insulated joints, and to equip each of these track sections with track circuit apparatus for the control of signaling apparatu governing movement of traffic through the track stretch.

In some situations, as for example the control of highway crossing signals or the lockin of switches, it is desirable to determine occupancy of a portion of the track stretch which does not coincide with the track sections which are established for the control of the traffic governing signal equipment. In order to secure the desired control in such situations it has been customary heretofore to divide the track sections into subsections and to equip each of these subsections with track circuit apparatus, while when more than one track section is involved a line circuit controlled by the track relays is pro- Vided.

The additional track circuit and other equipment for the subsections is relatively expensive, and if a track stretch includes many highway crossings or track witches so that numerous subsections are required, the cost of the equipment may be excessive.

It is an object of this invention to provide im-- proved train detecting apparatus which may be applied to a stretch of railway track to ascertain occupancy of a portion of aid track stretch without interfering with the operation of the track circuit apparatus with which the track sections are provided to control tramc in the track stretch.

Another object of the invention is to provide improved train detecting apparatu which makes it unnecessary to subdivide the track sections of a track stretch when the portion of the stretch in which it is desired to determine occupancy does not coincide with the track sections established to control the traffic governing signals.

A further object of the invention is to provide improved auxiliary track circuit apparatus of the type described which may be arranged so that its failure will not interfere with the operation of the principal track circuit apparatus.

Another object of the invention is to provide auxiliary track circuit apparatus of the type described which may be controlled by the principal track circuit apparatus so that the auxiliary track circuit apparatus is normally deenergized and is energized only when the principal track circuit apparatus detects a train in the portion of the track stretch in the vicinity of the auxiliary track circuit apparatus.

A further object of .the invention is to provide improved auxiliary track circuit apparatus of the type described which is arranged so that a first set of such apparatus may be employed to detect occupancy of a. first portion of a track stretch, and so that a second set of such apparatus may be employed to detect occupancy of a second portion of the track stretch even though the two portions of the track stretch overlap so that some of the track stretch is common to both portions.

Another object of the invention i to provide improved auxiliaryv track circuit apparatus of the type described which is adapted to detect occupancy of a zone in a track stretch even though this zone extends beyond the confines of a track section.

A further object of the invention is to provide improved auxiliary track circuit apparatus of the type described which employs an electron tube governed by occupancy of a selected zone in a track stretch, the apparatus being arranged so that failure of the electron tube cannot create a hazardous condition.

Another object of the invention is to provide improved highway crossing signal control means employing the auxiliary track circuit apparatus provided by this invention.

A further object of the invention is to provide improved crossing signal control means which is arranged so that the crossing signals are controlled jointly by the principal and the auxiliary track circuit apparatus, and so that failure of the auxiliary track circuit apparatus will not result in failure of the crossing signals to provide adequate warning of the approach of a train.

Other objects of the invention and feature of novelty will be apparent from the following description taken in connection with the accompanying drawings. 7

I shall describe several forms of apparatus embodying my invention, together with several modifications thereof which I may employ, and shall then point out the novel features thereof in claims.

In practicing my invention, at each end of the track zone occupancy of which is to be determined I connect a transformer with the section fails in such mamier as not to substantially interfere with the operation of the principal track circuit apparatus, while permitting energy to be supplied from one transformer to the other only when the intervening track zone is unoccupied. I supply alternating current of a distinctive frequency to the track rails through one of these transformers and I employ energy from the other transformer to vary the potential on the grid or control element of a cold cathode type electron tube, while I supply alternating current to the anode circuit of this type in series with the winding of a control relay. The tube operates to permit half cycles of energy of one polarity only to be supplied therethrough, and then only when energy is supplied over the associated track zone to establish the proper potential on the tube grid or control element.

In the drawings Fig. 1 is a diagram showing a stretch of railway track equipped with highway crossing signal control apparatus embodying my invention,

Figs. 2, 3, 4., 4A, 5, 6, 7, 8, 9, 9A, and. 10 illustrate modifications which may be employed,

Fig. 11 is a diagram showing a stretch of railway track in which the crossing signals for two highway intersections are governed by apparatus embodying this invention,

Figs. 12 and 13 are diagrams showing crossing signal control means embodying this invention applied to track sections in which coded alternating current track circuit energy is employed, and

Fig. 14 is a diagram showing switch locking means embodying this invention.

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

Referring to Fig. 1 of the drawings, there is shown therein a stretch of railway track over which trafiic normally moves in the direction indicated by the arrow, that is from left to right. The rails l and 2 of the track stretch are divided by insulated joints 3 into track sections for signaling purposes. One such section is shown in Fig. l and is designated 5T.

The track section 5T has at the entrance end thereof a wayside signal 58 which may be of any appropriate type and is controlled in accordance with traffic conditions in section ST and in the adjacent section in advance. As shown the signal 58 is of the familiar color light type and has a green or proceed lamp G, a yellow or caution lamp Y, and and or stop lamp R.

As shown the track section ST is provided with coded track circuit apparatus of well known design. The track circuit apparatus includes a coding relay 5CTM at the exit end of the section and having a contact H) which controls connection of the track battery 5TB across the section rails. The relay ECTM is controlled by traffic conditions in section GT in the manner well known in the art so that contact I of relay CTM is operated between its released and picked-up periods so as to cause energy of 75 or 180 code frequency to be supplied to the rails of section .BT according as section GT is occupied or is unoccupied.

A code following track relay 5TB is connected across the section rails at the entrance end of the section and has associated therewith a decoding transformer 5DT, and auxiliary relays 5H and SJ. When the track section is vacant relay 5TB follows code and its contact l2 alternately establishes the circuits of the two portions of the decoding transformer primary winding so that energy is induced in the transformer secondary windings. The energy from one of the transformer secondary windings is rectified and supplied to code detecting relay 5H so that the contacts of relay 5H are picked up as long as relay 5TB, follows code of either '75 or 180 code frequency.

The energy from the other secondary winding of the decoding transformer is supplied through a resonant rectifier unit IBUDU to relay 5J. The elements of the unit IDU are proportioned so that sufficient energy to pick up relay 5J is supplied through the unit when and only when the relay 5TB is responding to energy of 180 code frequency.

The relays 5H and EJ cooperate in the usual manner to control signal 58 so that this signal displays its red or stop indication when relay 5H is released, and when relay 5H is picked up the signal 58 displays its caution or its proceed indication according as relay 5J is released or picked up.

The relay 5H also controls the supply of energy to coding relay lCTM so that this relay is energized over a circuit controlled by a contact of a code transmitter T or of a code transmitter lBflCT depending on whether relay 5H is released or picked up.

The track section 5T includes an intersection with a highway H and this invention is directed to auxiliary track circuit means for controlling the crossing signals XS at the intersection to warn users of the highway of the approach of a train.

An insulated joint I5 is placed in one of the track rails at a point on the right-hand side of the intersection, while the portions of the track rail on opposite sides of the insulated joint are connected together through a reactor IS. The reactor I6 is designed so that it has relatively little impedance to the coded direct current traific governing energy, but has high impedance to alternating current employed in the control of the crossing signals.

A transformer T has a secondary winding having its center terminal connected to track rail I, while one end terminal of this winding is connected through a resistance I8 to the portion of rail 2 on one side of the joint [5, and the other end terminal of the transformer secondary winding is connected through resistance l9 to the portion of track rail 2 on the other side of the insulated joint i5. Accordingly, when energy is supplied to the primary winding of transformer T, one half of the transformer secondary winding supplies alternating current to the portion of the track section on one side of the joint l5, and the other half of the transformer secondary winding supplies current to the portion of the track section on the opposite side of the joint l5, while the reactor It prevents flow of alternating current energy between the portions of rail 2 on opposite sides of the joint l5 and thus prevents short circuiting of the transformer secondary winding.

The resistances l8 and i9 have relatively high resistance to thereby reduce to a very small value the now of coded direct current track circuit energy between the track rails through the two portions of the transformer secondary winding.

An insulated joint 2:] is located in rail 2 at the point in the rear of the intersection at which it is desired to have operation of the crossing signals initiated by a train moving in the normal direction of trafiic, while a similar insulated joint 22 is located in rail 2 at the point in advance of the intersection at which it is desired 5 to have operation of the crossing signals initiated by a train moving in the reverse of the normal direction.

A grid transformer AGT has the terminals of its primary winding connected to the rail 2 on opposite sides of the insulated joint 20, while a grid transformer BGT has the terminals of its primary winding connected to rail 2 on opposite sides of the joint 22. The transformers AGT and BGT are of such design that their primary windings have little resistance to flow of coded direct current track circuit energy through track rail 2.

The transformers AGT and BGT control electron tubes AT and BT respectively, which in turn control relays ATR, and BTR, which govern circuits for supplying energy to slow release relays E and W, while the relays E and W control the circuits of the windings of the interlocking relay XR which controls the crossing signals XS.

The electron tubes AT and BT are preferably of the cold cathode, controlled ionization type, while the associated relay together with a source of alternating current are connected across the anode and cathode of the tube to energize the relay by current passed by the tube when the tube is ionized, the voltage of the source of alternating current being, however, normally insufficient to start ionization, but being sumcient to cause the tube to break down when a preselected control electromotive force is applied to the control element or grid of the tube.

Each tube is provided with a grid or control element which is governed by the associated grid transformer. As shown one terminal of the secondary winding of the transformer AGT is connected through a resistance 40 and a condenser Iii to the grid 42 of the tube AT, While the other terminal of the secondary winding of the transformer AGT is connected to an intermediate point on a biasing resistor M which is connected across the terminals of the secondary winding of transformer ATT.

Similarly, one terminal of the secondary winding of grid transformer BGT is connected through a resistor (55 and a condenser 46 to the grid 48 of tube BT, while the other terminal of the transformer secondary winding is connected to an intermediate point on a biasing resistor 50 which is connected across the terminals of the second ary winding of transformer BTT.

Alternating current is supplied from a transformer ST to the transformer T, and to transformers ATT and BTT associated with the electron tubes, while the supply of energy to transformer ST is governed by a control relay GB. The alternating current may be supplied from any suitable source, not shown, the terminals of which are designated BX and CX.

The signal lamps and the relays other than the track relay are operated by direct current supplied from a suitable source, such as storage batteries, not shown, the terminals of which are designated B and C.

The equipment is shown in the condition which it assumes when sections ET and GT are vacant. At this time energy of 180 code frequency is supplied to relay ECTM and it operates to supply energy of 180 code frequency to the rails of section ET. This energy feeds over the section rails and through the reactor is and the primary windings of transformers AGT and BGT to the track relay 5TB, and operates it so that energy is supplied through the decoding transformer to relays 5H and 5J. As relays 5H and EU are both picked up the green or clear lamp G of signal 53 is lightedwhile as relay 51-1 is picked up its contact 25 establishes the circuit to supply energy of 180 code frequency to relay 4CTM so that energy of 180 code frequency is supplied to th rails of section 4T.

As relay 5H is picked up its contact 26 establishes the circuit of control relay CR and it is picked up so that its contact 21 establishes a circuit for relay W, while its contact 28 establishes a circuit for relay E. Accordingly, relays 'E and W are both energized and they establish the circuits of the windings 3e and 31 of relay XR. so that contacts 32 and as of the interlocking relay are both picked up, and interrupt the supply of energy to the crossing signals XS and thus prevent operation of the crossing signals.

As relay CR is picked up its contact 35 interrupts the supply of energy to transformer ST, and thus cuts off the supply of alternating current to the track rails and t the electron tubes; Accordingly the electron tubes and other portions of the auxiliary track circuit apparatus do not function when the track section is vacant, while the crossing signals are controlled by the usual track circuit apparatus as long as the section is vacant.

When a train moving in the normal direction of traffic enters section ET the track relay TB ceases to follow code and relays 5H and tJ release and cause the signal 58 to display its red or stop indication and change the energy supplied to relay iCTM from 180 to '75 code frequency.

On release of relay 5H its contact 26 interrupts the circuit of relay CR and relay CR releases so that its contact 35 establishes the circuit of the primary winding of transformer ST and energy is supplied from this tranformer to the primary windings of transformers ATT, BTT and T.

On the supply of energy to transformer T energy is supplied from one half of the transformer secondary winding through resistor i8 tot-he portion of the track section in the rearof the 45 intersection. This energy feeds from an end terminal of the transformer secondary winding through resistor iii, rail 2, primary winding of transformer AGT, through the wheels and axles of the vehicles forming the train, and o-verraii so I to the center terminal of the transformer primary winding.

Similarly, energy is supplied from the other half of the secondary winding of transformer T to the portion of the track section in advance of 55 the intersection. This energy feeds from the end terminal of the transformer through resistor l9, track rail 2, primary winding of transformer BGT, thence over back contact of relay SCTM or through the battery 5TB and front contact iii of relay 5CTM, and rail i to the center terminal of the transformer secondary winding.

In addition on the supply of energy to transformer ST energy is supplied therefrom to transformers ATT and BT'I' with the result that en- 65 ergy is induced in the secondary winding of each of these transformers and is impressed between the anode and cathode of the associated tube,

while a portion of the transformer secondary voltage is impressed on the grid of the associated 70 tube through the biasing resistor.

As pointed out above, the voltage of the energy impressed'between the anode and cathode of each tube is insufficient to cause ionization of the tube. The potential applied to the grid of each tubeby 75 energy supplied thereto through the biasingresistor is insufficient to cause ionization of the tube, so that unless energy is supplied to the tube grid from the associated grid transformer the tube is not ionized and no current flows in the tube anode circuit.

On the supply of alternating current through the primary winding of grid transformer AGT energy of relatively high voltage low amperage is induced in the transformer secondary winding and is supplied therefrom to the grid 42 of the tube AT.

During the half cycles in which the energy supplied from the grid transformer AGT to the grid 42 of the tube AT are of positive relative polarity the potential on the tube grid is increased to a value effective to ionize the tube and cause it to become conducting.

The transformers AGT and ATT are supplied from the same source so the energy impulses supplied from these transformers to the tube AT are substantially in phase. The various parts of the equipment are arranged so that when an impulse of energy of positive polarity is supplied from grid transformer AGT to the grid of tube AT, the impulse of energy supplied from the transformer ATT is of such polarity that the positive terminal of the transformer secondary winding is connected to the anode of the tube AT. The tube AT, therefore, breaks down and en rgy flows through the tube to relay ATR over the circuit which is traced from an end terminal of the secondary winding of transformer ATT to the tube anode 5|, through the tube space to cathode 52, and Winding of relay ATR to the other terminal of the transformer secondary winding.

The tube AT, once it has become conducting, continues to be conducting throughout most of the positive half cycle of energy from the transformer ATT. The next or negative half cycle of energy from the transformer ATT serves to deenergize the tube and restore it to its normal condition, while as long as energy continues to be supplied from the grid transformer to the tube grid, the tube is rendered conducting on each subsequent positive half cycle so that an impulse of energy is supplied to the winding of relay ATR during every other half cycle of the alternating current.

A condenser 55 is preferably connected across the terminals of the winding of relay AIR, and during the supply of each impulse of energy through the tube AT, a charge is built up on the condenser 55, while in the intervals between impulses of energy from the tube, energy from the condenser feeds to the relay winding and maintains the flow of energy through the relay winding and thus maintains the relay contacts picked up. If desired the relays ATR and BTR may be of a type the contacts of which are slow to release so that they will remain picked up in the intervals between the energy impulse-s supplied to the relay winding, and thus eliminate the need for condensers connected across their terminals.

On the supply of alternating current to the primary winding of transformer BGT the tube ET is rendered conducting and energy from transformer B'I'I is supplied through the tube to relay IB'IR to pick up its contact.

On picking up of relay ATR its contact 56 establishes a circuit to supply energy to a winding of relay E, while on picking up relay BTR its contact 58 establishes a circuit to supply energy to relay W.

There is a short period between the time at which relay CR releases and interrupts the circuits which it controls for supplying energy to relays E and W, and the time at which relays A'IR and BTR pick up and establish circuits for the relays E and W. The relays E and W are of a type which are slow in releasing so their contacts remain picked up throughout this period and maintain the circuits of the windings of the interlocking relay XR.

Accordingly, when a train enters section 5T relay CR releases and interrupts the circuits which it controls for supplying energy to the relays E and W, while the auxiliary track circuit apparatus provided by this invention is placed in operation and causes the relays ATR and BTR to be picked up and establish circuits to supply energy to the relays E and W so that they continue to prevent operation of the crossing signals.

When the train advances beyond the joint 20, the wheels and axles of the vehicles forming the train provide a path between the rails I and 2 which shunts the alternating current away from transformer AGT, and energy is no longer supplied to the transformer AGT while energy is no longer supplied from the transformer AGT to the grid of tube AT. Accordingly, the tube AT ceases to be conducting so energy ceases to be supplied to relay ATR and its contact 55 releases and interrupts the supply of energy to relay E. Contact 65 of relay E therefore releases and interrupts the circuit of the winding 30 of relay XR so that the contact 32 controlled by winding 30 releases and establishes the circuit of the crossing signals XS and these operate to yarn users of the highway of the approach of a train.

When the train advances beyond the joint IS the supply of energy to transformer BGT is cut off and the tube ET is rendered non-conducting so relay BTR releases and interrupts the circuit of relay W with the result that contact 6| of relay W interrupts the circuit of winding 3| of the interlocking relay XR. The internal construction of the relay XR is such that on deenergization of winding 3| while winding 35 is deenergized the contact 33 is prevented from moving all of the way to its released position.

When the rear of the train vacates the portion of the track section in the rear of the joint t5 alternating current is again supplied through the primary winding of transformer AGT so energy is supplied from the transformer secondary winding to the grid 42 of tube AT so that the tube is rendered conducting and energy is supplied to relay ATR to pick up its contact 55.

The alternating current energy supplied to transformer AGT at this time is supplied through the winding of relay 5TH. The value of this alternating current energy is too small to cause operation of the relay, however.

On picking up of contact 55 of relay ATR energy is supplied to relay E and its contact 6!] establishes the circuit of the winding 30 of re- 1ay XR so that contact 32 is picked up and discontinues operation of the crossing signals XS, which is proper as the rear of the train has cleared the highway intersection.

The internal construction of the interlocking relay XR is such that on picking up of contact 32 contact 33 is prevented from moving to its released position to establish the circuit of the crossing signals.

When the rear of the train advances beyond the joint IS the shunting effect of the train on the alternating current supplied to the portion of the track section in the rear of the joint I is relatively small because of the impedance of the reactor to the alternating current. Accordingly, as soon as the rear of the train passes over the joint 55 there is a substantial increase in the alternating current supplied to transformer AGT and the tube AT is rendered conducting so relay ATR will become picked up to discontinue operation of the crossing signals. The reactor l6, therefore, serves to insure that operation of the crossing signals will be discontinued as soon as the train clears the intersection.

When the rear of the train advances beyond the joint 22, alternating current is again supplied through the primary winding of transformer BGT so that the tube ET is again rendered conducting. Accordingly, relay BTR picks up and establishes a circuit for relay W and contact Si of relay W picks up and establishes the circuit of winding 3! of the interlocking relay XR so that contact 33 of relay 2B is picked up.

W hen the train advances far enough to vacate section ET the impulses of coded direct current supplied from the track battery 5TB to the track rails during the picked-up periods of contact Iii of coding relay ECTM feed through the primary windings of transformers .BGT and AGT and through the reactor it to the track relay 5TB and operate it so that energy is supplied through the decoding transformer EDT to relay 5H. At this time energy of '75 code frequency is supplied to section ET and the rate of operation of relay 5TB is such that too little energy is supplied to relay 5J through the associated resonant unit to pick up the relay contacts. Accordingly, relay 5J remains released and on picking up of relay 5H energy is supplied to the yellow lamp Y of signal 58 over a front contact of relay 5H and a back contact of relay SJ, while on picking up of relay 5H its contact changes the energy supplied to section lT from '75 to 180 code frequency.

In addition, on picking up of relay 5H its contact 26 establishes the circuit of relay CR so that its contacts 2? and 28 establish circuits to sup-- ply energy to relays W and E, while its contact 35 interrupts the supply of energy to transformer ST and thus cuts oil the supply of alternating current energy to the track rails, and also cuts off the supply of energy to the transformers ATT and BTT associated with the tubes AT and BT. Accordingly, energy is no longer supplied through the tubes to relays ATR and BTR and they release and interrupt the circuits which they control for supplying energy to the relays E and W. Before this occurs, however, energy is supplied to relays E and W over the circuits established by relay CR so the relays E and W remain picked up and maintain the circuits of the windings 39 and 3| of interlocking relay XR and thus prevent operation of the crossing signals at this time.

This system also operates to provide proper control of the crossing signals on movement of a train through the track stretch in the reverse of the normal direction.

When a train moving the reverse direction enters section 51 it shunts the track rails so as to prevent the supply of coded. direct current to the track relay it'remains released so that relay 5H releases. On release of relay 5H its contact 25 interrupts the circuit of relay CR so that it releases and interrupts the circuits which it controls for supp-lying energy to relays E and W. In addition, on release of relay CR its contact 35 establishes the circuit for supplying energy to the transformer ST so that energy from this transformer is supplied to the transformers ATT and BTT associated with tubes AT and BT, and is also sup-plied through transformer T and over the section rails to the grid transformers AGT and BGT to render the tubes conducting. Accordingly energy is supplied through the tubes to pick up relays ATR and BTR and they establish circuits for relays E and W and thus prevent operation of the crossing signals XS.

When the train advances beyond the joint 22 transformer BGT is shunted and tube ET is rendared non-conducting so that relay BTR releases and interrupts the circuit of relay W. Contact 6i of relay W, therefore, releases and interrupts the circuit of winding 3| of relay XR and contact 33 of relay XR releases and establishes the circuit of the crossing signals XS so that they operate towarn users of the highway of the approach of a train.

When the train advances beyond the joint 15 it shunts the transformer AGT so that tube AT is rendered non-conducting and relay ATR releases and causes release of relay E with resultant interruption of the circuit of the winding 30 of relay KB. The internal construction of relay XR is such, however, that contact 32 is prevented from moving to its released position at this time.

When the train vacates the portion of the track section between insulated joints l5 and 22 energy is again supplied to transformer BGT so that tube ET is rendered conducting and relay BTR is picked up and establishes the circuit of relay W. Accordingly contact 6| of relay W picks up and establishes the circuit of the winding 3! of relay XE so that contact 33 is picked up and discontinues operation of the crossing signals XS.

When the train vacates the portion of the track section between insulated joints l5 and 20 energy'is again supplied to transformer AGT so that tube AT is rendered conducting and energy is supplied to relay ATR to pick up its contact and establish the circuit of relay E with the result that contact Bil of relay E establishes the circuit of the winding 36 of relay XR.

When the train vacates section ET, the impulses of coded direct current supplied to the section rails feed to relay 5TB and operate it so that relay EH is picked up to establish the circuit of relay CR. and it picks up to establish circuits for the relays E and W and to discontinue operation of the auxiliary track circuit apparatus.

When the front of a train moving in the normal direction, or the rear of a train moving in the reverse direction, is at a point in the track section intermediate the insulated joints l5 and 22, alternating current from transformer T is prevented from reaching transformer BGT, but coded direct current supplied at the exit end of the section flows through the primary winding of transformer EST and may cause impulses of energy to be induced in the secondary winding of the transformer and therefore cause impulses to be supplied to the grid of the tube ET. The transformer BGT and the other portions of the apparatus are proportioned so that the impulses of energy supplied to the tube grid as a result of the flow of the impulses of coded direct current through the primary winding of transformer BC-T are of such value as to be ineffective to render the tube conducting. Accordingly the relay BTR is released under the conditions outlined.

Th relay BTR may be of a type the contacts of which are slow to pick up, while the condenser 64 connected across the terminals of the relay winding renders the relay slow to pick up. The relay BTR and the associated condenser may be proportioned so that the relay will not pick up if supplied with impulses of energy at the frequency of the coded track circuit energy if the impulses of coded track circuit energy supplied through the transformer BGT should cause the tube BT to become conducting.

The coded track circuit current is of relatively low frequency, the highest code speed usually employed being 180 cycles a minute, or 3 cycles a second. The alternating current employed in the track circuit is of much higher frequency, such as 60 or 100 cycles a second, so there will be a great difierence between the frequency of the supply of impulses of energy to relay BTR when the tube ET is rendered conducting by alternating current supplied to the transformer BGT and when the tube is rendered conducting by coded track circuit energy supplied through the transformer BGT. Accordingly, the relay BTR and the associated apparatus may be proportioned so that the relay will pick up when alternating current is supplied to transformer BGi'I, but to not pick up when coded track circuit energy is supplied to transformer BGT.

It will be seen that this crossing signal control system operates so that the traific governing track circuit apparatus operates to prevent operation of the crossing signals as long as the track section is vacant, while the auxiliary track circuit apparatus is deenergized as long as the section is vacant. As soon as the track section is occupied the auxiliary track circuit apparatus is energized and control of the crossing signals is transferred to the auxiliary track circuit apparatus, while the auxiliary track circuit apparatus serves to prevent operation of the crossing signals until the train advances to within a selected distance from the crossing.

When a train moving in either direction enters an approach section for the crossing, the crossing signals are placed in operation, while the auxiliary track circuit apparatus operates to discontinue operation of the crossing signals as soon as the approach section is vacated. The crossing signals remain under the control of the auxiliary track circuit apparatus as long as the section is occupied, but as soon as the section is vacated the traffic governing track circuit apparatus assumes control of the crossing signals and discontinues operation of the auxiliary track circuit apparatus.

Since the auxiliary track circuit apparatus is normally deenergized and becomes energized only when the section is occupied, the wear on the electron tubes is reduced to a minimum and their life is correspondingly increased, whil the energy consumed by the auxiliary track circuit apparatus is reduced to a minimum.

This system is arranged so that failure of the electron tubes or other portions of th auxiliary track circuit apparatus will not produce an objectionable failure of the crossing signals nor interfere with the proper functioning of the traific governing signal apparatus.

If when a train moving in the normal direction of trafiic enters th section the tube AT is defective and will not function, relay ATR will remain released and will not establish a circuit for relay E, and this relay will release and interrupt the circuit of the winding 30 of relay XR so that contact 32 releases and establishes the circuit of the crossing signals. Accordingly, operation of the crossing signals will be initiated as soon as the 12 train enters section 5T instead of being delayed until the train advances beyond the insulated joint 20.

In addition when the tube AT is defective, operation of the crossing signals will not be discontinued when the train passes the joint l5. Instead the signals will continue to operate until the train vacates the track section. When this occurs the trafiic governing track circuit apparatus functions in the normal manner and discontinues operation of the crossing signals and of the auxiliary track circuit apparatus.

Similarly, if the tube ET is defective operation of the crossing signals will be initiated as soon as the section is occupied and will be continued until the section is vacated.

If the tube failure is caused by short circuiting of the elements of the tube, th tube will cease to serve as a rectifier and alternating current will be supplied through the tube. The relay energized by current supplied through the tube is of the direct current type and its contacts will remain released on the supply of alternating current to the relay winding.

Failure of the tubes, therefore, will cause operation of the crossing signals to be initiated sooner and to be continued longer than usual. While this additional time of operation of the crossing signals may delay users of the highway, it will not create a hazardous condition, and the operation of the equipment is such that users of the highway are always provided with a warning of the approach of a train for at least the normal period.

In like manner failure of the line circuits connecting transformers ATI and BTT with the transformer T, or of the line circuits over which the relays ATR and BTR control the relays E and W, will result in prolonged operation of the crossing signals but will not cause a failure of the crossing signals to operate, and will not interfere with operation of the traffic governing signal apparatus. Failure of the line circuit over which relay 5H controls the relay CR, will result in continued operation of the auxiliary track circuit apparatus to control the crossing signals, while operation of the crossing signals will be started and stopped at the usual times, and operation of the'traflic governing signals will not be affected.

The auxiliary track circuit apparatus is shown controlled by the traffic governing signal apparatus so as to be deenergized when the associated track section is vacant, and to be energized and control the crossing signals only when the section is occupied. This is the preferred arrangement, but it is contemplated that the relay CR may be omitted and the auxiliary track circuit apparatus be continuously energized and have complete control of the crossing signals.

The auxiliary track circuit apparatus is shown arranged to provide for control of the crossing signals on movement of trains in the reverse as well as in the normal direction of traflic. If control of the crossing signals on movement of trains in the reverse direction is not required, the tube BGT and associated apparatus such as transformers BTT and BGT, and relays BTR and W, may be omitted, and the auxiliary track circuit apparatus may be employed to detect occupancy only of the portion of the track section between insulated joints 20 and I5.

In the system shown in Fig. 1 the alternating current employed in the auxiliary track circuit apparatus is supplied from a commercial source of current. If such a source is not available the alternating current may be supplied by a tuned alternator, and Fig. 2 illustrates such an arrangement.

Referring to Fig. 2 there is shown therein a tuned alternator TA which may be of any well known construction and which when supplied with direct current supplies alternating current of a, suitable frequency, such as 60 or 100 cycles a second, to the transformer ST. The supply of direct current to the alternator TA is controlled by back contact 35 of relay CR so that the alternator is deenergized as long as the track section is vacant and is energized and causes alternating current to be supplied to the auxiliary track circuit apparatus as long as the section is occupied.

In the systems shown in Figs, 1 and 2 alternating current of the same frequency is supplied over the track rails to the grid transformers as is supplied to the tube anode circuits. If desired energy of different frequencies may be employed for these purposes, and Fig. 3 shows such a modification.

As shown in Fig. 3 energy is supplied from the transformer ST to the transformer T through a rectifier RX with the result that the frequency of the energy supplied from transformer T to the track rails is twice that supplied from transformer ST to the transformers ATT and BTT.

Accordingly, because of the higher frequency of the energy supplied to the tube grids, there will always be a time during each half cycle in which energy of positive polarity is supplied to the anode of a tube that the potential on the tube grid is such as to render the tube conducting. This will be true even though there is a considerable phase shift in the energy supplied over the track rails relative to the energy supplied to the tube anode circuits. The tube characteristics are such that once a tube becomes conducting it continues to be'conducting regardless of changes in the grid potential as lon as energy of proper potential and polarity is supplied to the tube anode circuit, so the use of the higher frequency energy in the track circuits will not substantially reduce the time during which a tube is conducting, and the relay which is energized by current supplied through the tube will be supplied with energy an adequate proportion of the time to keep its contacts picked up.

The impedance of the reactor Is to flow of alternating current therethrough is proportional to the frequency of the alternating current, and if alternating current of relatively high frequency, such as is made possible by the use of the frequency doubling arrangement shown in Fig. 3, is employed in the track circuits, the reactor I 6 may be proportioned so as to have little resistance to the coded direct current track while having high impedance to the alternating current track circuit energy so that a train on one side of the joint l will have little shunting effect with respect to alternating current supplied to the portion of the track section at the other side of the joint [5. This will insure prompt termination of operation of the crossing signals when a train passes beyond the joint 15, while it also permits the coded direct current track circuit energy to be readily supplied through the reactor so that the maximum length of track section over which paratus may be operated will not be substantially affected.

the coded track circuit ap- In the modifications shown in Figs. 1, 2 and 3, the transformer T is provided with two secondary windings one of which supplies energy to the portion of the track stretch at one side of the joint l5 and the other of which supplies energy to the'portion of the track stretch at the other side of the joint I5. If desired energy may be supplied from the same secondary winding to the portions of the track stretch. on both sides of the joint l5, and Fig, 4 shows such an arrangement.

Referring to Fig. hone end terminal of the secondary winding of transformer T is connected to track rail l, while the other end terminal of this winding is connected through resistance 18 to the portion of rail 2 at the left of joint l5 and through resistance 19 to the portion of rail 2 at the right of joint l5. When a train is in the portion of the track stretch at either side of the joint 15, the supply of alternating current to the grid transformer on that side of the intersection is cut oil, while the resistor included in the circuit for supplying energy from the transformer T to the track rails limits the current taken from the transformer and thus prevents excessive reduction in the value of the energy supplied from the transformer to the portion of the track section at the other side of the joint l5.

When train is in the portion of the track section at one side of the joint I5 it exerts a shunting effect through resistors l8 and 19 on the portion of the section at the other side of the joint. The resistance of resistors l8 and I9 is so high, however, that the shunting effect exerted through them will not interfere with operation of the apparatus on the side of the joint opposite from the train.

In the modifications described above the secondary winding of the transformer T is connected across the section rails and a reactor is connected around the insulated joint l5 at the highway intersection to permit flow of direct current track circuit energy around the joint l5 while preventing flow of alternating current auxiliary track circuit energy between the portions of the track section on opposite sides of the joint I5 to thereby insure prompt cessation of operation of the crossing signals when the rear of a train passes over the insulated joint It.

The need for the reactor can be eliminated by connecting the secondary winding of transformer T around the joint [5 as shown in Fig. 4A. In this modification the transformer T is proportioned so that its secondary winding has little resistance to flow of direct current, while a current limiting resistance 56 is connected in series with the primary winding of the transformer T to limit the energy supplied through the transformer T to the track rails.

The grid transformers AGT and BGT are shown connected in series with the track rail 2, but they may be connected across the rails l and 2 as shown, in Fig. 9. A reactor 61 may be connected in series with the track relay 5TB to prevent flow of alternating current energy in the winding thereof, while an impedance of appropriate form, such'as a resistance 68, is connected across the section rails intermediate the insulated joint 28 and the entrance end of the section to permit flow of alternating current between the track rails while substantially preventing flow of direct current between the section rails.

The supply of energy to the transformer ST may be governed by a relay CR as shown in Fig. 1,

15 so that energy is supplied to the transformer when and only when the associated track section is occupied.

When a train enters section 5T so that energy is supplied to the transformer ST, energy is supplied therefrom through the resistance 65 to the transformer T, while energy is supplied from the transformer T to the grid transformers AGT and BGT over the circuit which is traced from the left-hand terminal of the secondary winding of transformer T over rail 2, through the primary winding of transformer AGT, through wheels and axles of the vehicles forming the train to rail I; over contact it of relay CTM to rail 2, and thence through the primary winding of transformer BGT to the right-hand terminal of the secondary winding of transformer T. Accordingly, each of the grid transformers supplies energy to the associated tube so that the auxiliary track circuit apparatus operates as explained in connection with Fig. 1 to prevent operation of the crossin signals.

When the train advances beyond joint 2!), the shunt between the track rails provided by the train prevents flow of energy from transformer T through the primary winding of transformer AGT so the tube associated with transformer AGT ceases to be conducting and operation of the crossing signals is initiated. At this time energy from transformer T continues to be supplied through the primary winding of transformer BGT, but when the train advances beyond the joint I 5 the supply of energy to transformer BGT is cut off and the relay associated with this transformer releases.

As soon as the rear of the train advances beyond the joint 55 energy from transformer T is supplied to transformer AGT over the circuit which is traced from the left-hand terminal of the secondary winding of transformer T over track rail 2, through primary winding of transformer AGT and resistor 68 to rail I, and thence through the wheels and axles of the vehicles of the train to rail 2 and the right-hand terminal of the winding of transformer T. Accordingly, the tube associated with transformer T is rendered conducting and operation of the crossing signals is discontinued promptly when the rear of the train clears the intersection.

When the rear of the train passes over joint 22 energy from transformer T is again supplied to transformer BGT and the relay associated with this transformer picks up. When the train vacates the track section coded direct current supplied at the exit end of the section feeds to the track relay 5TB and operates it so that the supply of energy to transformer ST is cut off and the auxiliary track circuit apparatus ceases to function.

The equipment operates in a similar manner on movement of a train through the track stretch in the reverse direction.

In the modifications shown in Figs. 1 to 4 the coded direct current track circuit nergy must be supplied through the reactor It. This reactor will have some resistance to the coded direct current and will therefore reduce the maximum perable length of track circuit. This can be overcome by substituting for the reactor a circuit controlled by the auxiliary track circuit apparatus and shunting the joint l5, and Fig. 5 shows such an arrangement.

Referring to Fig. 5, a circuit shunting the joint 15 is established when the contacts of relays E and W are picked up. This circuit includes front contact 10 of relay E and front contact 1| of relay W. The equipment is otherwise the same as that shown in Fig, 1 except that the reactor i6 is omitted, while a transformer with a single secondary winding, as shown in Fig. 4, is employed to supply energy to the section rails. This type of transformer is necessary to prevent short circuiting of the transformer secondary by the shunt circuit which is at times established around the joint [5.

When the track stretch is vacant relays E and W are held picked up by energy supplied over front contacts of relay CR so contacts 70 and H establish the circuit shunting the joint l5 and coded track circuit energy may flow around joint !5 through the shunt circuit. The resistance of the shunt circuit may be extremely low so that there is little impedance to the flow of coded direct current track circuit energy over the section rails.

When a train enters the track section relay CR. releases and establishes the circuit to supply energy to transformer ST so that the auxiliary track circuit apparatus functions as explained in connection with Fig. 1 to supply energy to relays E and W and keep them picked up although the circuits controlled by relay CR for supplying energy to these relays are interrupted.

When the train enters the approach section at the left of joint l5 relay E releases and its contact 50 interrupts the circuit of winding of the interlocking relay XR to thereby initiate operation of the crossing signals, while contact 70 of relay E interrupts the shunt circuit around joint I 5. Since the section is occupied at this time there is no need for the coded direct current to be supplied around joint [5 and interruption of the shunt circuit will not interfere with operation of the traffic governing signal system.

When the train advances beyond joint (5 relay W releases and its contact 1| additionally interrupts the shunt circuit around the joint [5. Accordingly, when the rear of the train passes beyond the joint l5 the train ceases to exert any shunting effect on the alternating current supplied to the portion of the track section at the left of joint [5, and the auxiliary track circuit apparatus associated with the portion of the track section at the left of joint l5 will function immediately after the rear of the train passes over joint [5, and relay E will pick up to discontinue operation of the crossing signals.

When the train advances farther in the track stretch relay W will be picked up, as explained in connection with Fig. 1, while on picking up of relay W its contact ll completes the circuit shunting the joint l5. At this time, however, the train is so far removed from the joint l5 as to have little or no effect on energy supplied from transformer T to the section rails, and the relays E and W are maintained energized by the auxiliary track circuit apparatus.

When the train advances far enough to vacate the section 5T, coded direct current supplied to the track rails at the exit end of the section feeds over the track rails and through the shunt circuit established by front contacts 70 and H of relays E and W to the track relay and operates it so that the relay 5H is picked up and establishes the circuit of relay CR, Accordingly, the relay CR picks up and its contact cuts off the supply of energy to transformer ST and thus discontinues operation of the auxiliary track circuit apparatus, while contacts 2'! and 28 of relay CR establish circuits for the relays W and E so that their con- 17 tacts are maintained'picked up to maintain the shunt circuit around the joint l and to prevent operation of the crossing signals.

The modification shown in Fig. 5, like that shown in Fig. l, operates so that if on entrance of a train into the track section, one of the electron tubes is defective, or the auxiliary track circuit apparatus does not function for any other reason, operation of the crossing signals will be initiated as soon as the train enters the section instead of being deferred until the train advances to a predetermined point in the section. In addition, the equipment shown in Fig. 5 operates so that operation of the crossing signals will not be discontinued when the train passes the intersection if the auxiliary track circuit apparatus is not functioning properly.

When the equipment is arranged as shown in Fig. 5, if the auxiliary track circuit apparatus is defective, the circuit shunting the insulated joint i5 will not be established when the approach sections on opposite sides of the highway crossing are Vacated. Accordingly, when the train vacates the track section, coded direct current energy supplied at the exit end of the section cannot feed to the track relay, and the associated relay 5H will remain released and will not establish'the circuit of relay CR. As a result the relay E or W will remain released, the one depending on which part of the auxiliary track circuit apparatus is defective, and the crossing signals will continue to operate, while the signal at the entrance to section 5T will display its stop indication and energy of 7 5 code frequency will be supplied to the rails of the adjacent section in the rear to cause the signal for that section to display its caution indication.

The continued operation of the crossing signals and the continued display of a stop indication by the signal at the entrance to section 5T will provide an indication that the equipment is not functioning properly.

The failure of the equipment shown in Fig. 5 to resume normal operation when the section is vacated if the auxiliary track circuit apparatus is not functioning properly may be overcome by employing means to periodically establish a circuit shunting the joint I5, as shown in Fig. 6.

Referring to Fig. 6, a coding device 200T is provided which has a contact 13 which when closed establishes a circuit shunting the joint 15. The contact 13 of the coder ZIJCT may be operated at any appropriate rate, such as 20 code frequency, which is substantially different than the rate of operation of the coders controlling the supply of traffic governing energy to the section rails. The coder 290T may operate continuously, or it may be controlled as shown by contact 12 of relay CR so as to operate only when the section is occupied. 7

With the arrangement shown in Fig. 6 when a train passes through the section and the auxiliary track circuit apparatus is functioning properly, the relays E and W will be picked up and establish the shunt circuit around joint I5 when the section is vacated, as explained in connection with Fig. 5. If when the section is vacated one of the relays E or W remains released, the shunt circuit controlled by these relays will not be established, but contact 13 of coder ZBCT will periodically establish a circuit shunting the joint 15. During the closed periods of contact 53 coded track circuit energy supplied at the exit end of the section will feed around the joint l5 over the circuit established by contact 13 to the track relay and operthrough the tube over the ate it so that the associated code detecting relay 5H picks up to establish a circuit for relay CR. When CR picks up it establishes circuits for relays E and W and they pick up to discontinue operation of the crossing signals, and to establish the circuit which they control for shunting the joint l5.

With the arrangement shown in Fig. 6, when a train is in section 5T with the end of the train adjacent one side of the joint l5, during the.

closed periods of contact 13 of coder 200T the train will exert shunting efiect on the auxiliary track circuit energy supplied to the portion of the track section on the opposite side of the joint 15. The relays E and W may be of a type which are slow enough in releasing to remain picked up during the periods in which contact 13 is closed, and thus prevent momentary operation of the crossing signals.

In the modifications shown in Fig. 1 a relay ATR is energized through the tube AT and controls the supply of energy to a winding of relay E. It is possible, however, to energize the winding of relay E from the tube AT, and thus eliminate the relay ATR, and Fig. '7 illustrates such a modification.

The modification shown in Fig. 'l is the same as that shown in Fig. 1 except that the relay ATR and the transformer ATT have been eliminated and the anode circuit of tube AT has been connected to a winding of relay E, while the grid biasing resistor 44 is connected between the line wires 92 and S3. The condenser 55, employed in the system shown in Fig. 1, is connected across the terminals of the winding of relay E.

As long as the section is vacant relay E is held picked up by energy supplied over contact 28 of relay CR as explained in connection with Fig. 1. When a train enters the section relay CR releases and causes energy to be supplied to transformer ST so that energy is supplied over the track to transformer AGT to render the tube AT conducting, while energy is also supplied to the tube anode circuit. Accordingly, energy is supplied line wires 92 and 93 to a winding of relay E and serves to keep the contacts of relay E picked up. i

The various parts of the equipment are arranged so that the energy supplied to the relay E through the tube AT is of the same relative polarity as the energy supplied to the relay E over the circuit controlled by contact 28 of relay CR so that the contacts of relay E will remain picked up on transfer of control of the relay from the principal to the auxiliary track circuit apparatus.

When a train enters the portion of the track section between insulated joints l5 and 20, energy is no longer supplied to transformer AGT and the tube AT ceases to be conducting and energy is no longer supplied to relay E and its contact releases to initiate operation of the crossing signals.

When the portion of the track section between insulated joints l5 and 20 is vacated, energy is again supplied to transformer AGT so that the tube AT is rendered conducting and energy from the transformer ATT is supplied through the tube AT to a winding of relay E to pick up its contact and discontinue operation of the crossing signals. When the track section is vacated relay GR is picked up and discontinues operation of the auxiliary track circuit apparatus and establishes a circuit to energize relay E.

The modification shown in Fig. 8 is similar to that shown in Fig. 7. In the sytem shown in Fig. 8 the transformer ATT isnot employed and the secondary winding of transformer ST is connected across the anode and cathode of tube AT through a current limiting resistor Q and over line wires 95 and 93, while the grid biasing resistor 3 3 is connected between wires 56 and 98. A winding of relay E is connected across wires 95 and 98 on the side of resistor 95 remote from the transformer ST.

When relay CR is released so that energy is supplied to transformer ST, energy is supplied through transformer T to the track rails, and thus to transformer AGT to render the tube conductme. In addition, when energy is supplied to transformer ST, energy will be supplied from the transformer secondary winding through the resistor S5 to line wires 95 and 93, and therefrom to the winding of relay E.

During the half cycles in which the impulses of energy induced in the secondary winding of transformer ST are such that energy of positive polarity is supplied to wire 98, energy will be supplied through the tube AT, assuming that it is conducting, so that the transformer secondary is in effect short circuited through the tube, and the tube serves to divert energy from the winding of relay E. The resistor 95 serves to limit the supply of energy from the transformer ST and thus prevents overloading of the tube AT.

During the half cycles in which the impulses of energy induced in the secondary winding of transformer ST are such that energy of positive polarity is supplied to line wire 98, energy will not be supplied through the tube AT, and all of the energy supplied through resistor 95 will be supplied to the winding of relay E.

Accordingly, when the tube AT is conducting, the impulses of energy of one polarity supplied to the winding of relay E are of substantially lower value than those of the other polarity, and as a result there is a substantial direct current component in the energy supplied to the winding of relay E and is eifective to maintain the contacts of the relay E picked up.

The various parts of the equipment are arranged so that the direct current component of the energy supplied from transformer ST to a winding of relay E is of the same relative polarity as the energy supplied to relay E over the circuit controlled by relay CR. This insures that the contacts of relay E will remain picked up when control of relay E is transferred from relay CR to the auxiliary track circuit apparatus.

When the portion of the track section between the insulated joints 20 and i5 is occupied energy is not supplied to transformer AGT and the tube AT ceases to be conducting. Under these conditions impulses of energy of the same value are supplied to the winding of relay E during both halves of the cycles of energy induced in the secondary winding of transformer ST. Accordingly, there is no direct current component in the energy supplied to the winding of relay E at this time and the contacts of the relay release and initiate operation of the crossing signals, while the winding of the relay may have high inductance to reduce the flow of alternating current therein.

When the portion of the track section between the joints l5 and 20 is vacated and the tube AT is again rendered conducting, the direct current component is again present in the energy supplied from transformer ST to the winding of relay E and its contact is picked up to discontinue operation of the crossing signals.

When the track section is vacated relay CR 20 is picked up and its contact 35 interrupts the circuit of transformer ST to thereby prevent operation of the auxiliary track circuit apparatus, while relay E is maintained picked up by energy supplied over front contact 23 of relay GB.

The modifications shown in Figs. 7 and 8 have been illustrated and described in connection with the circuits associated with the tube AT, but it is to be understood that these modifications are 1() equally applicable to the circuits associated with the tube BT.

In the modifications already described the primary windings of the grid transformers AGT and BGT have been connected in series with the track rail so that coded direct current track circuit energy must be supplied through those windings.

While the transformers AGT and BGT may be provided with primary windings having low resistance to the coded direct current track circuit energy, these windings will have some resistance to such energy, and will reduce somewhat the maximum length of track section over which the coded track circuit can be operated. The series connection of the grid transformers is not essential, and these transformers may be connected across the rails as shown in Fig. 9.

Referring to Fig. 9 the transformer AGT has one terminal of its primary winding connected to one track rail and has the other terminal of its primary winding connected to the other track rail through a resistor I80 which serves to limit flow of coded direct current track circuit energy th ough the transformer primary winding.

The transformer AGT is located at a point in the track stretch far enough in the rear of the highway crossing so that if operation of the crossing signals is initiated When a train advances beyond the transformer, the crossing signals will be operated for at least a predeter- 4 mined interval before the train reaches the intersection.

The equipment at the intersection as well as the equipment associated with transformer AGT may be arranged as shown in any of the modifications previously described.

In operation, when a train enters the section so that alternating current is supplied to the section rail at the intersection, this energy is supplied to the primar winding of transformer AGT with the result that energy is supplied from the transformer secondary winding to the grid of the associated tube to render it conducting and thus prevent operation of the crossing signals.

When the train advances beyond the transformer AGT the supply of alternating current to the transformer is cut off and the tube associated with transformer AGT ceases to be conducting and operation of the crossing signals is initiated and is continued until the train vacates the portion of the track section between transformer AGT and the intersection.

In addition, when a train is present in the track section and is approaching the transformer AGT, it shunts alternating current from the transformer and thus reduces the value of the energy supplied from the transformer AGT to the grid of the associated tube. The shunting effect of the train on the transformer AGT gradually increases as the train approaches the transformer and before th train reaches the transformer,

may cause the energy supplied to the grid of the associated tube to be reduced to a value ineffective to maintain conductivity of the tube. As a result operation of the crossing signals will be initiated before the train reaches the transformer, and the signals will be operated for somewhat longer than the minimum period prior to arrival of the train at the intersection. The shunting effect of the train on the transformer AGT will vary somewhat with ballast conditions, so the point to which the train must advance before operation of the crossing signals is initiated will vary with changes in ballast conditions. However, as operation of the crossing signals is always initiated when the train advances beyond the transformer AGT, and as this provides for the minimum period of operation of the signals, the system is entirely safe and any variation in the period of operation of the signals is in excess of the minimum period.

If preferred as shown in Fig. 9A a condenser NH ma be substituted for the resistor 15% in the circuit of the primary winding of the transformer AGT. The condenser iii! operates to permit alternating current auxiliary track circuit energy to be supplied to the transformer AGT, while preventing flow of the coded direct current signal control energy to this transformer.

The transformer AGT may be inductively coupled with the track rails. As shown in Fig. 10 a loop I82 consisting of a plurality of turns of wire is mounted between the track rails with portions of the loop adjacent the rails l and 2. The ends of the loop are connected to the terminals of the primary winding of the transformer AGT.

When alternating current is supplied to rails l and 2 at the intersection, and the portion of the track section between the loop and the intersection is vacant, alternating current flows in the portion of the rails I and 2 adjacent the loop I02 and induces energy in the loop from which it is supplied to the primary winding of transformer AGT, so that energy is supplied from the secondary winding of transformer AGT to the grid of the associated tube and causes the tube to be conducting.

When the portion of the track section between the loop and the intersection is occupied, alternating current no longer flows in the portion of the rails l and 2 adjacent the loop N32, and energy is no longer supplied from the loop through transformer AG I to the tube grid and the tube becomes non-conducting.

The modification shown in Fig. 10, like that shown in Fig. 1, operates so that the crossing signals are not started until the train advances beyond a predetermined point in the track section.

The modification shown in Fig. 10 results in no impedance whatever to the supply of coded direct current energy over the track rails and consequently does not affect the length of track circuit which can be operated.

This crossing signal control system is adapted for use where there are two highway crossings relatively close together so that the approach sections for the crossing signals overlap, while the system is also adapted for use where a crossing is adjacent an end of a track section so that an approach section for the signal for that crossing extends into the adjacent track section, and Fig. 11 is a diagram illustrating these modifications.

Fig. 11 consists of Figs. 11A and 1113 which when placed together with Fig. 113 at the right, is a diagram of a stretch of railway track over which traific normally moves in the direction indicated by the arrow, that is from left to right. The rails l and 2 of the track stretch are divided by insulated joints 3 into track sections for signaling purposes. and are designated IT and BT,

Each track section has at the entrance end thereof a wayside signal, designated S with an appropriate prefix, while each track section is provided with coded track circuit apparatus for controlling the signal for the section, and for also controlling the supply of coded energy to the rails of the adjacent section in the rear. The coded track circuit apparatus employed in sections IT and ST is similar to that employed in the system shown in Fig. l and a detailed description of the track circuit apparatus is unnecessary.

The track circuit apparatus for section IT includes coded feed-back equipment for indicating at the exit end of the section whether or not the section is occupied. The coded feed-back equipment may be arranged in any manner well known in the art, and has been shown arranged as shown in Letters Patent of the United States No. 2,286,002 to Frank H. Nicholson.

The track stretch includes intersections with highways HI and H2. The intersection with highway H! is located in section 1T, while the intersection with highway H2 is located in section 8T at a point adjacent the entrance end of the section so that on movement of a train in the normal direction through the track stretch it is necessary to start operation of the crossing signals KS2 for the intersection H2 before the train enters section 8T.

The crossings HI and H2 are located so close together that the approach sections for the signals for the two crossings overlap. It is necessary on movement of a train in the norma1 direction through the track stretch to, initiate operation of the crossing signals X82 before the train advances to the point in the track stretch at which it is necessary to initiate operation of the crossing signals XSI on movement of a train through the track stretch in the reverse direction.

Alternating current of one frequency, such as 60 cycles per second, is employed in the auxiliary track circuit apparatus for the control of the crossing signals X88, and alternating current of a different frequency, such as cycles per second, is employed in the auxiliary track circuit apparatus for the control of the crossing signals X82, while filters of well known design are provided at appropriate points to prevent interference between the two sets of auxiliary track circuit apparatus.

The construction of the filters is not a part of this invention, and to simplify the disclosure these have been shown diagrammatically in the drawings.

The same reference characters are employed in Fig. 11 to identify the various elements of the auxiliary track circuit apparatus as are employed in Fig. 1, while in Fig. 11 the reference characters for the auxiliary track circuit apparatus for the control of signals XS! are preceded by the prefix I, and those for the apparatus for signals X82 are preceded by the prefix 2.

The equipment is shown in the condition which it assumes when the track stretch is vacant. At this time energy of code frequency is supplied to coding relay BCTM so that it supplies energy of this code frequency to the rails of section BT and this energy feeds to track relay 8TB and operates it with the result that energy is supplied through the decoding transformer flDT to relays 8H and BJ. As relays 8H and SJ are both 75 picked up signal 88 displays its green or clear Two track sections are shown,

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