US2213420A - Railway traffic controlling apparatus - Google Patents

Description

Sept. 3, 1940.

H. A. THOMPSON RAILWAY TRAFFIC CONTROLLING APPARATUS Filed .May 28,1938 4 Sheets-sheet l INVENTOR 15 ATTofi'NEY Sept. 3, 1940. H. A. THOMPSON.

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed May 28, 1938 4 swam-sheet 2 k 5. WC P Z J. c LQVIIIIIJJE 0 1) B T a c INVENTOR Howard ompron BY HIS ATTORNEY Sept. 1940- H. A .'T.HOMPSON RAILWAY TRAFFIC. c'oN'fRoLL ING APPARATUS Filed May 28, 1938 4 Sheets-Sheet 5 Fig Fig. 10.

Fly. 8.

INVENTOR llowalaA ompron HIS ATTORNEY Sept. 3, 1940. H. A. THOMPSON RAILWA Y TRAFFIC CONTROLLING APPARATUS Filed May 2a, 1938 4 Sheets-Sheet 4 INVEN TOR Howard T lzampron I BY HIS ATTORNEY Patented Sept. 3, 1940 UNITE T'T TENT OFFICE RAILWAY TRAFFIC CONTROLLING APPARATUS Application May 28, 1938, Serial No. 210,743

11 Claims.

One object of my invention is to provide a new and improved form of such organization which protects against the giving of false pro 1O ceed indications in the event of breakdown ofthe insulated joints which electrically separate the rails of adjacent track sections.

Another object is to make this protection an inherent part of signalling systems which use 15 code following track relays of the single element type.

An additional object is to efiect the named protection without staggering the polarities of adjacent track circuits.

20 A further object is to provide protection facilities which cause the wayside signal at the location of a broken down joint to go to stop before the guarded block becomes vacated and I there to remain until the defective joint is re- 25 paired.

A still further object is to insure that should the energy leaking over a broken down joint be momentarily interrupted the named protection will automatically restore itself without produc- 30 ing even a temporary proceed indication on the part of the afiected signal.

An additional object is to arrange the conductors and contacts of the protection giving circuits so that they are self checking.

., Another object is to provide cooperating cut section facilities which break up cascading action of steady track circuit energy, which detect a failure of their own insulated joints where either front or back contact repeating is used, and which are immune to false controlling effects of door bell code in back contact coding.

A further object is to prevent the Wayside signal at the entrance of a track section to which steady trackway energy is being supplied from flashing a false approach indication when a train enters that section.

A still added object is to accomplish the'above without dispensing with any of the desirable features of continuously coded track circuit control.

In practicing my invention, I attain the above and other objects and advantages by supplementing the rail energy supply facilities at each signal location by what will be termed a lock-out 55 circuit. Should the normally coded energy from .in the diagram.

one track section leak forwardly over a defective joint into the rails of an adjacent section, this lock-out circuit becomes effective to supply steady or non-coded energy to the rear section rails. In feeding over the faulty joint, that 5 steady energy holds the forward section track relay continuously picked up, and in consequence the associated decoding apparatus causes the controlled Wayside signal to display a restrictive aspect as an indication of the faulty condition.

I shall describe a number of forms of railway trafiic controlling apparatus embodying my invention and shall then point out the novel features thereof in claims. These illustrative embodiments are disclosed in the accompanying drawings in which:

Fig. 1 is a diagrammatic representation of a stretch of railway track equipped with trafiic controlling apparatus embodying my invention;

Figs. 2 and 3 show different forms of cut section facilities which may be used in conjunction with the signal location equipment of Fig. 1;

Fig. 4 is a representation of one of the signal location equipments of Fig. 1 modified to include a second form of control circuit for the code detecting relay;

Figs. 5, 6 and 7 are similar representations showing still further forms which the referred to relay control circuit maytake;

Fig. 8 is a showing of a cut section equipment which codes over a back contact of the track relay;

Fig. 9 is a diagrammatic view of trackway apparatus which cooperates in the control of highway crossing signals and which allows non-coded 5 trackway energy to be used tocontrol such signals without interfering with the lockout protection against defective insulated joints; and

Fig. 10 is a showing of the repeater relaysof the cut section location of Fig. 9 arranged in a 40 second manner to provide immunity to door bell codes.

In the several views of the drawings like reference characters designate corresponding parts. Referring first to Fig. 1, the improvements of my invention are there disclosed as being incorporated in the trackwayportion of a combined automatic block signalling and cab signalling system for a track I2 over which it will be assumed that trafiic moves in the single direction indicated by the arrow, or from left to right Insulated rail joints 3 divide the protected stretch of this track into the customary successive sections and the rails of each of these sections form a part of a track circuit of the usual character.

The particular track stretch which is represented in Fig. l is intended for use in a railway system employing electric propulsion and for this reason alternating current track circuit energy is used together with impedance bonds 4 of the customary form which conduct propulsion current around each pair of the insulated rail joints. As the description proceeds, however, it will become apparent that the apparatus of my invention is equally well suited for use on a steam road in which application either direct current or alternating current track circuit energy may be used. In such an application the bonds 4 would, of course, be omitted.

In Fig. 1 only two of the referred to track sections, E-Ea and EaF, are completely shown. Points of main signal block division involving these sections are marked by locations E and F while a subdivision of the signal block E-F is designated by location Ea.

Positioned at the entrance of each of the main signal blocks is a wayside signal S which is adapted to indicate to an approaching train the nature of the traffic conditions in the blocks immediately ahead. The particular signals which are shown by way of illustration at locations E and F are of a well-known color light type. When lighted, the three lamps G, Y and R of each respectively direct rays of green, yellow and red light into the range of vision of the engineman of an approaching train. As signal Se protects the entire block E-F, no wayside signal is provided at the cut section location Ed.

The rails of each of the referred to sections of track form a part of a track circuit to which coded alternating current train control energy normally is continuously supplied through a track transformer TT connected with the rails at the trafiic leaving or exit end of the section by means of a circuit which includes the usual current limiting reactor 6. This energy is derived from any suitable source and distributed to the several locations of track section division in conventional manner, as by the aid of a transmission circuit (not shown) extending along the right-of-way. In the diagram, characters B and C designate power distributing terminals which are supplied from one such source. To facilitate explanation, it will be assumed that the alternating current energy of this source has a frequency of 100 cycles per second.

The particular signalling system shown in Fig. 1 is of the three indication variety and it makes use of track circuit energy of two different codings. These codings are produced by a code transmitter CT which interrupts the supply circuit of the associated track transformer TT a definite number of times per minute according to the traffic or other conditions ahead. In the lustrative form shown, each device CT is provided with two circuit making and breaking ontacts l5 and 580 which are continuously actuated by a motor or other suitable mechanism (not shown in detail) at two different speeds. For purposes of explanation, itwill be assumed that these speeds are such as respectively to provide codes of and 180 energy pulses per minute.

Each of the referred to track circuits further includes the operating winding of a track relay TR which is installed at the traffic entering end of each track section and which receives operating energy from the rails thereof. Each of these track relays is of the single element code following type and the winding thereof may be designed to respond either to direct or to alternating current. When of the alternating current type, the winding is directly connected to the rails of the associated track section in the manner represented in Figs. 1, 2, 3 and 7. When of the direct current type, this connection includes the supplemental equipment shown at 1 in each of Figs. 4, 5, 6, 8 and 9.

Typically, this equipment 1 may take the form of a resonant transformer unit which includes a transformer, capacitor, reactor and rectifier connected as shown in Fig. 4 and so proportioned as freely to pass the cycle coded signal control energy which is received from the trackway and to rectify this energy before applying it to the direct current winding of the code following track relay TR. As regards operation, therefore, the direct current track relay is the full equivalent of the single element alternating current device shown at TR in Fig. 1.

As long as the winding of either of these two types of relays is deenergized, the relay contacts 8 and H] are released and occupy the lowermost position, shown dotted. When, however, the track rails transmit coded energy to the relay, its response to the individual pulses thereof causes these contacts to pick up and occupy the uppermost positions, shown heavy, upon the occasion and for the continuance of each of these pulses.

In the illustrative automatic block signaling system of Fig. 1, energy of one or the other of the previously described '75 and codings is normally fed to the track circuits at all times and this coded energy is used to control both the .wayside signals S and cab signals mounted on a train which proceeds along the track l-2. Because of the wellknown character of such cab signals, no attempt has been made to disclose them in the present application.

For distinguishing code following operation on the part of the track relay TR and for selecting in accordance with the presence or absence of such operation the coding of the energy which is supplied to the rails of the track section to' the rear, use is made at each wayside signal location of a pair of repeater relays FE and BP and a code detecting relay H. For aiding relay H in controlling the associated wayside signal S, a cooperating code distinguishing relay DI 80 also is provided at each location.

Devices FP and BP, respectively, are front contact and back contact repeaters for the track relay TR. Included in the energizing circuit of each is a contact H! of the associated track relay and further included in that of relay BP is a contact H of the relay FTP. Both of these circuits are shown as deriving energy from a direct current source, designated by the terminals plus and minus. Each time that contact ill of the track relay picks up in response to a pulse of trackway energy, the circuit of relay FF is completed over conductor l2. Likewise, each time that the track relay is deenergized and relay FP continues to hold its contact II in the picked-up position, the energizing circuit for relay BP is completed over conductors l3 and M.

Both of the relays FP and BP are sufficiently slow releasing that they keep their contacts continuously picked up between adjacent pulses of trackway energy which the track relay TR receives during normal operation of the signalling system. These slow release characteristics are preferably provided through the use of snubbing resistors I5 and 16. Each of these resistors is bridged across the winding of the associated relay and serve to sustain the flux in the magnetic circuit of the relay for an appreciable period following each interruption of Winding energizing current. The proportioning of each snubbing resistor is such that the associated relay will bridge the longest ofi period of any one of the codes to which the track relay TR normally responds.

It will thus be seen that as long as track relay TR is not following a code and is continuously deenergized, both of the repeater relays FF and BP likewise are continuously deenergized and their contacts occupy the released position. When, however, the track relay follows either of the two codes which the transmitter CT at the opposite or exit end of the track section produces, relay FF is continuously picked up, its contact H sets up the circuit for relay BP and contact It) of relay TR completes that circuit each time that it occupies its released position. Moreover, should the track relay receive steady energy and thus hold its contacts continuously picked up, relay FP becomes continuously energized and relay BP becomes continuously deenergized. Since relay 3? can be energized only when relay TB is following a code, it functions as a code detecting device.

In order that the snubbing resistor 16 associated with the back contact repeater relay BP will be effective only when the companion relay Fl? is picked up, the snubbing circuit which includes resistor 56 is carried over contact H of relay FP. As long as-relay FP continues to be intermittently energized, this contact completes the snubbing circuit and causes relay BP to introduce the before described delay in its contact releasing operation. When, however, relay FP is continuously deenergized, contact H opens the snubbing circuit for relay BP and, in that event, the delayed release characteristics are no longer effective. As a result, each release of contact H of relay FF is followed almost instantly by a release of the contacts of relay BP.

Relay H is a repeater of the second slow release relay BP and in the system of Fig. 1 it is arranged to perform a code detecting function. Preferably, it is a slow responding device of the ordinary ferrule type (wherein one leg of the magnetic circuit of the relay is passed through a section of heavy copper tubing that inductively retards changes in the flow of flux through that leg) and is controlled over a front contact E8 of the associated relay BP. When used, as shown, in a system employing one or another of two trackway codes of 75 and 180 energy pulses per minute, it is preferable to proportion this relay in a manner that its pick-up time will be not less than six-tenths second and its release time not less than one and two-tenths seconds.

As long as contact M of relay BP remains released, the winding of relay H is continuously deenergized and the contacts thereof are released. Each time, however, that contact I3 is picked up, current flows through the winding of relay H over a circuit extending from the positive terminal of a suitable supply source through front contact 58, conductor l9 and the winding of relay H back to the negative terminal of the supply source. If the length of this energizing period exceeds the pick-up time (assumed to be six-tenths second) for relay H, it moves its contacts to the picked-up position where it continues to hold them during the entire energizing period referred to and for the release time (assumed to be one and two-tenths second minimum) following the expiration thereof.

Control of the associated wayside signal S is effected by a contact 2| of relay I-I acting in cooperation with a contact 22 of the code distinguishing relay DlBfl. Whereas code detecting relay H picks up whenever the associated track relay TR follows either of the 75 or '180 trackway codes, relay DIBD is arranged to pick up only when the received code is of the'180 energy pulse per minute variety. For effecting this selective response; the energizing circuit of relay D880 includes a tuned unit J I80 which receives alternating current voltage of code pulse frequency from the secondary winding of a decoding transformer DT.

In operation of the code distinguishing apparatus just described, a second contact 8 of the track relay TR pole changes a primary energizing circuit for the decoding transformer DT in the customary manner. That is, each time that the contact is picked up, direct current flows in one direction through one portion of the transformer primary (by way of a circuit which extends from the positive terminal of a suitable supply source through front contact 8, conductor 23, the upper half of the transformer winding and mid tap 4 back to the negative terminal of the supply source) and each time that contact 8 is released, current flows in the opposite direction through another portion of the winding (by way of a circuit which includes conductor and the lower winding path).

The resulting alternating current voltage of code pulse frequency which is induced in the secondary winding of transformer DT supplies the winding of code distinguishing relay Dl80 with current of pick up intensity only if the frequency of that voltage is of the 180 code rate to which the tuned circuits of the unit J H86 are resonant. Thus, relay Dl8ii picks up its contact 22 in response to operation of relay TR which is initiated by the 180 code and maintains its contact in the released position at all other times, including those when energy of the 75 pulse per minute code rate is received from the trackway. Because of the well-known character of the circuits which make up the resonant unit J H80 no detailed description thereof is here given.

From the foregoing it will be seen that as long as the track relay TR fails torespond to coded energy from the trackway, the contacts of both of the relays H and Dist? will remain released. Under the stated condition (which obtains when the associated track section is occupied by a train), the controlled wayside signal S displays the indication of stop by virtue of lamp R thereof receiving lighting current over a circuit which may be traced from the positive terminal of a suitable supply source through back contact 25 of relay H, conductor 26 and the lamp R back to the negative terminal of the supply source.

l/Vhen, however, energy of the low speed or 75 coding is received and responded to by the track relay TR, code detecting relay H picks up its contacts. Under this condition, the controlled wayside signal S displays the approach indication by virtue of lamp Y thereof receiving lighting current over a circuit which extends from the positive supply terminal through front contact 2% of relay H, back contact 22 of relay D180, conductor 21 and the lamp Y back to the negative supply terminal.

Finally, when the received trackway energy is of the 180 pulse per minute coding, both of the relays H and DISH pick up their contacts and the controlled wayside signal S then displays the clear indication by virtue of lamp G thereof receiving lighting current over a circuit which may be traced from the positive supply terminal through front contact 2! of relay H, front contact 22 of relay DI80, conductor 28 and the lamp G back to the negative supply terminal.

Considering now the circuits through which the rails of the track section to the rear of each of the signal locations E, F etc. are supplied with coded energy, these include contacts 30, 3| and 32 of the three relays FP, BP and H. Depending upon the positional combination of these three contacts, the primary winding of the associated track transformer TT is periodically connected with the alternating current source B-C over the one or the other of coding contacts I80 and 15 of device CT or it is steadily connected with the alternating current source for a protective purpose later to become evident.

In the event that a train occupies the track section and thus continuously deenergizes the associated track relay TR at the entrance end thereof, the contacts of all three of the relays FP, BP and H are released and the rails of the track section to the rear then receive energy of the 75 pulse per minute coding over a circuit which may be traced from the supply terminal B through conductor 33, back contact 3| of relay BP, conductor 39, the coding contact 15 of device CT, conductor 35 and the primary of the track transformer 'IfI' back to the supply terminal C.

When energy of this 75 coding is received and responded to by the track relay TR, all three of the relays FP, BP and H hold their contacts in the picked-up position. Under this condition, the rails of the rear track section receive energy of the 180 pulse per minute coding over a circuit which may be traced from the supply terminal B through conductor 36, the coding contact I80 of device CT, conductor 31, front con tact 32 of relay H, conductor 38, front contact 3! of relay BP, conductor 40, front contact 30 of relay FP, conductors 4| and 35 and the primary of track transformer TT back to supply terminal C.

Likewise, when energy of this 180 coding is received and responded to by the track relay TR, the contacts of all three of the relays FP, BP and H are again picked up and the rails of the rear track section again receive energy of the 180 pulse per minute coding over the circuit which was traced in the preceding paragraph.

From the foregoing it will be seen that the organization of apparatus which is disclosed in Fig. l constitutes the trackway portions of a three indication combined automatic block signalling and cab signalling system. In operation of this system, as long as all sections of the protected stretch of track l-2 are vacant, the rails of each transmit energy of the 180 coding to the code following track relay TR which acts upon the code detecting and distinguishing relays H and Dltfl in a manner causing the controlled wayside signal S to display the green or clear indication.

When, however, a train passes through the track stretch, the shunting action of its wheels and axles deenergizes continuously the track relay associated with each of the occupiedsections. It, in turn, acts upon the associated decoding relay apparatus in a manner causing it to produce the red or stop indication on the part of the controlled wayside signal S and to include coding contact 15 in the primary circuit of the track transformer TT which is connected to the rails of the track section to the rear of the signal location.

Assuming that this rear section is vacant, the rails thereof transmit this 75 code energy to the track relay TR. at the entrance end thereof and it, in turn, causes the associated relays to put the controlled signal S at yellow or approach and to supply the track section to the rear of the location of that signal with energy of the 180 pulse per minute coding. Finally, in responding to this energy the track relay TR at the entrance of the last named section causes the controlled wayside signal S to show the green or clear indication and the rails of the track section to its rear also to receive energy of the 180 coding.

It has already been pointed out that under a certain positional combination of the contacts of relays FP, BP and H at each of the signal locations, the track circuit to the immediate rear thereof will receive steady or uncoded energy. In the organization of apparatus herein disclosed, this particular combination of relay contact positions results only in the event of breakdown of the insulated joints 3 which electrically separate the rails of adjacent track sections. As will be explained more fully presently, it functions to prevent the controlled wayside signal S from giving a false proceed indication in response to the energy which flows from the rails of the track section to the rear over the faulty insulated joint into the rails of the advance track circuit and thence into the winding of the associated track relay TR.

The condition of joint failure discussed in the preceding paragraph is hazardous in that its usual effect is to cause the wayside signal S at the location of the fault to give a proceed indication even though a train may occupy the track block which the signal guards. Assume, for example, that the joints 3 at location E break down upon the passage of a train through block E-F of Fig. 1. This permits energy of the '75 coding to feed over the faulty joints from the rear section rails into the rails of the occupied forward section.

As soon as the rear of the train passes some.

distance beyond the point of connection of the winding of track relay TR with the rails of this forward section, the potential between these rails resulting from the rear section leakage energy rises to a point sufiicient to effect code following operation on the part of relay TR. Acting in the normal manner through the associated decoding relays H and Dl80, this causes the controlled wayside signal Sc to display the yellow or ap proach indication. Were the leakage energy allowed, as in the past, to remain coded, it would cause the energization of relay H. Relay H be ing energized would transfer the feed circuit for transformer T1 from the 75 coding contact to the 180 coding contact and that, in tLun, would cause the energization of relay Di8ll. This would cause the display of a clear or green aspect by signal Se and thereby falsely advise the engineman of a following train that the track section EF is vacant when in reality it is occupied.

In the case of steam territory where the track rails I and 2 do not form part of a propulsion circuit through which driving energy is supplied to electric locomotives, the condition just stated results only in the event that both of the insulated joints 3 at the signal location are defective simultaneously and thus interconnect rail I of the rear section with rail I of the forward section and rail 2 of the rear section with rail 2 of the forward section. In electrified territory, however, a single broken down insulated joint 3 is the full equivalent of the just described two broken down joints in steam road territory. This is because of the autotransformer action of the impedance bonds 4.

Should, for example, the joint in rail I become defective and establish direct connection from the rear section length to the forward section length of that rail, there is completed by the impedance bonds 4 a return path around the companion joint in rail 2 and this produces the same effect as were this second joint also to lose its insulating qualities. In electrified territory, therefore, the probability of the false proceed signal indication previously discussed is comparatively high and requires special protection facilities to prevent accidents and damage in the event of a broken down rail joint.

In the improved form of organization of my invention, this protection is effected at each signal location by the before mentioned circuits which normally feed coded energy to the track circuit to the rear and which are controlled by contacts 38, iii and 32 of the forward section relays FR 3? and H.

Referring to location E of 1, again assume that, while passing over the joints 3 at that location, a train causes either or both of them to break down and establish a path over which energy from the rails of the rear track section may feed into the rails of the forward section. Because of the presence of the train in the rear portion of the section E-F, relay TB is at first continuously deenergized and the contacts of all three of the relays FP, BP and H are accordingly released. Under this condition, the rails of the section to the rear of location E are supplied with energy of the '75 coding over a circuit previously traced as including conductor 33, back contact 3! of relay BP, conductor 39 and the coding contact I5.

As soon as the rear of this train has passed far enough beyond the signal location to allow an on period of the 75 code energy (feeding from the rear to the forward section over the defective joint and the impedance bond return path) to energize the track relay TR, front contact repeater relay FP becomes energized and picks up. Contact 38 now establishes what will be termed a lock-out circuit over which steady energy is supplied to the rails of the rear track section. This lock-out circuit may be traced from power source terminal B through conductor 33, back contact SI of relay 3?, conductor 48, front contact 36 of relay FP, conductors GI and 35 and the primary of track transformer TT back to the supply terminal C.

In feeding over the defective joint to track relay TR, this steady energy holds it continuously picked up. Relay FP, therefore, continues to remain energized while back contact repeater relay BP fails to receive any energy and thus retains its contact 39 in the released position in which the look-out circuit is completed. At the same time, released contact I8 of relay BP maintains relay I-I deenergized and its contact 25, in turn completes the lighting circuit for lamp R of the controlled wayside signal Se and thereby causes that signal to display the indication of stop This stop indication by the signal at the location of the defective joint continues uninterruptedly as the train advances entirely out of the track block E--F and, in fact, until the broken down joint is repaired. This, of course, is because the steady energy which is supplied through the lock-out circuit feeds uninterruptedly over the defective joint into the winding of the track relay TR in advance and causes the contacts of relays FP, BP and H continuously to remain in the positions just described. a

It has been seen that a proceed indication (either approach or clear) can be given by the controlled wayside signal S only when the code following track relay TB is in operation and it has been mentioned that code detecting relay H is made somewhat slow in picking up. The reason for this delay is to ensure that should the track relay be momentarily deenergized from any cause while the look-out circuit is in effect, such a proceed signal indication will not falsely be iven.

In the event of such momentary deenergization during lock-out conditions, relay BP receives current over back contact Id of the track relay. 1 In picking up, it interrupts at contact 3| the supply of steady energy to the rear track circuit and continues this interruption until relay FP releases contact I I. At that time the contacts of relay BP are again released and the supply of energy to the winding of relay His discontinued.

'As already stated, the pick-up period for relay H is preferably made slightly longer (such as of the before stated order of six-tenths second) than the release period of the relay FP. This assures that the momentary deenergized condition of the track relay TR above mentioned will be ineffective for causing relay H to pick up and change the indication of the controlled wayside signal S to either approach or clear. Contacts 2i and 32 of relay I-I thus remainingcontinuously released, the signal is uninterruptedly held at stop and the 180 code supply circuit is kept open at contact 32 Following the sequence of operations just described as being occasioned by a momentary deenergization of the track relay, the look-out circuit automatically re-establishes itself upon the first on period of the 75 code, which again is supplied to the rear track section (from the terminal B connected to conductor 33 over back contact 3| of relay BP and coding contact '75 of device 01'') as soon as repeater relays FP and BP both become released. In feeding over the defective joint to the winding of the track relay, this on pulse picks up the contacts of that relay and energizes relay FP. Contact 38 thereof once more completes the look-out circuit and thus assures that the controlled wayside signal S will continuously be held at stop.

In the above operations incident to automatic restorationv of the lock-out circuit following a momentary deenergization of the track relay, it will be seen that reliance is placed upon the opening by contact I I of relay FP of the snubbingcircuit for relay BP, thereby permitting the contacts of the latter relay to drop out almost immediately upon the opening of the contacts of relay FP. This quickens the cut off of energy to the winding of relay H and thus allows the minimum pick-up delay of that relay to be considerably shorter than would be permissible otherwise.

The just described lockout circuit also becomes effective in the event that an insulated rail joint should break down when the protected track sections are vacant. Under these conditions all of the track circuits are receiving energy of the coding prior to the joint failure and the wayside signal at the entrance of each block is displaying the green indication of clear.

If, now, an insulated joint breaks down to practically zero resistance, the track relay at the faulty location receives such a large amount of energy from the code being supplied to the track circuit to the rear (when this rear code is in step with the forward code) that its contacts will occupy the picked-up position for a much longer percentage of the total time than they occupy the released position. This characteristic isinherent in the single element track relay design and results from the fact that abnormally high values of relay energizing current pick up the contacts more quickly and introduce a corresponding delay to their release because of the higher intensity of magnetic flux. This flux must, of course, die down to a predetermined value before the contact carrying armature can be released under the biasing action of the usual spring or of gravity.

In consequence of the lengthened picked-up periods of the track relay contacts and of the shortened released periods thereof which the assumed conditions produce, the intermittent energization of the back contact repeater relay BP is reduced to the point that that relay releases its contacts regardless of the relative positions of the energy pulses of the forward and rear section codes which combine to energize relay TR. In the meantime, of course, the front contact repeater relay FP remains picked up and in this manner lock-out is produced upon the release of relay BP.

If, while the track relay is responding to 180 code, and 180 code is being supplied to the track circuit to the rear, an insulated joint breaks down to have an appreciable value of resistance, say of the order of five-tenths ohm, the track relay TR will continue to respond to the two 180 codes as long as these two codes remain approximately in phase or have a relation in which their on and their off periods occur approximately in step. Under this condition the operation of the track relay is not sufficiently altered from normal to cause back contact repeater relay BP to drop out in the manner already described and the controlled wayside signal thus continues to display clear.

Since, however, the two coding devices' CT which supply the rails of the forward and the rear track sections, respectively, are usually driven by separate induction motors the relative speeds of which cannot help but vary somewhat, the inphase relation of the codes will not be a continuous one and gradually they will fall out of step. As they approach the condition in which the off period of one code is filled in by the on period of the other code, the track relay TR will again remain picked up continuously, thereby releasing relay BP and producing "lock-out in which the controlled wayside signal displays the red or stop indication.

Assume next that the insulated joint breaks down at a time when dissimilar codes are present in the track rails on the two sides of the joint, as for example, 75 code in the forward section and 180 code in the rear section. If the joint breaks down to practically zero resistance, track relay TR will again receive such a large amount of energy from the code being applied to the track circuit in the rear (when the pulses of that rear code fall into meshing relation with those of the forward code) that the relay will maintain its contacts picked up for a much greater percentage 'of the time than they are released. As in the case of the similar codes previously described, this will cause the back contact repeater relay BP to release to produce lock-out and cause the controlled wayside signal S to show stop.

If, under the conditions stated at the beginning of the preceding paragraph, the insulated joint breaks down to have a substantial resistance of the previously assumed order of five-tenths ohm, track relay TR will attempt to respond to both of the two codes. This, of course, will cause the contacts of the relay to be picked up a much larger percentage of the time than they are released. Again, this will result in the release of the back contact repeater relay BP to produce lockout and a display of stop by the wayside signal.

In those unusual instances in which a defective insulated joint may fail to produce lock-out, this action is delayed only until a train passes over the affected track circuits in the normal direction of traffic. The first train to do this produces lock-out in the manner previously explained and thus protects following train movements. In this connection it is to be observed that a following train in the normal direction of trafiic will, of course, unlock the circuit during the particular period that the train is passing over the defective joint. However, when the rear of this train is several rail lengths past the faulty joint, the circuit will again lock-out due to the feeding of energy from the rear track circuit over the joint and to the winding of the track relay TR.

The protection facilities herein disclosed are especially adapted for use with systems of automatic block signalling wherein single element track relays of the type shown at TR are employed. For many installations this single element type of relay is preferred in place of the conventional two element track relays for the reason that its use requires no line conductors between adjacent signal locations for local energy supply. Moreover, the fact that it gives a nonpolarized form of response provides further advantages later to be discussed.

One very practical feature of the look-out circuit just described is that it is not dependent upon relative polarity of the track circuits on the opposite sides of the joint. In addition to protecting against the usual failure of the joint which has already been described, the circuit is thus also capable of protecting against a further type of failure wherein one rail of one of the track circuits may become connected to the opposite rail of the adjacent track circuit.

This second type of failure sometimes does occur and may be caused, for example, by a connection between the track relays and the track junction box or may result when the conductors are accidentally pinched under the box lid or when the insulation comes off the conductors and allows them to come into direct contact with the metallic portions of the box. If the protection depended upon the use of the usual two element track relay and the staggering of track circuit polarities, the condition just described would result in a false clear signal instead of the desired stop indication produced by the look-out circuits of Fig. 1.

The particular form of lock-out circuit represented at location E in Fig. 1 provides for a check in the operativeness of the facilities through which steady energy from power source terminal B is supplied by way of conductor 33 over the cation E of 1.

back contact 3! of relay BP. Should this connection accidentally become broken, the track circuit to the rear of location E could under no circumstances receive energy of the coding and in the event of failure of one of the joints 3 at the named location at a time when a train was in the forward portion of track section EF, the track relay TR would continue to remain deenergized and hold the controlled signal S at stop. Moreover, should the connection involving conductor 33 break simultaneously with the breakdown of one of the insulated joints at location E there again would be no energy available with which to pick up the track relay contacts and the desired stop aspect of the signal would still result.

Comparable checking of the operative condition of the connections which involve conductor Q0 of the lock-out circuit may be provided by modifying the just described fundamental form of this circuit in the manner shown at location F in Fig. 1. Here, conductor 39 from the front point of the coding contact 75 is connected to the back point of contact 39 of relay FP instead of being joined directly with conductor Gil as shown in Fig. 1 at location E.

From an inspection of the connections shown at location E, it will be seen that were the connection it to be broken, the desired form of operation of the lock-out circuit would be interfered with. That is, energy then still could feed over back contact 3}, conductor 39, the 7,5 coding contact, conductor 35 and the track transformer TT to the rails of the rear track section and thus produce false proceed signal indications against which the now disabled lockout circuit would be incapable of guarding. Still further, energy might be fed over the coding contact through front contact 32 of relay H, conductor 38, front contact '3! of relay BP, conductor 39, the coding contact 15 and thence to the track transformer TT. This would result in a distorted 180 code being received by the rear track circuit which, under certain conditions, will produce a proceed indication on the part of the wayside signal or a train carried cab signal which may be under the control of this distorted code.

When, however, the connections are modified in the manner shown at location F, the undesirable conditions just named are eliminated and conductor ll! becomes completely checked because a break in this conductor will posi tively open the circuit through which both the "i5 code and the Hill code must feed to the track transformer. In the modified arrangement of location F, for example, the 75 code feed must be carried over back contact 3! of relay BP, conductor 40, back contact 3|! of relay FF and conductor 39.

From examination of the modified lock-out circuit that is disclosed at location F in Fig. 1, it will be seen that the normal operation thereof in selecting the coding of the energy supplied to the rear track circuit and also its operation in effecting a lock-out in the case of a broken down insulated joint is the same as in the basic form of circuit previously described in connection with the disclosure thereof at 10- It thus differs therefrom only in providing a further safeguard against failure or improper operation.

The effect of the steady lock-out energy on succeeding track circuits to the rear is to cause all wayside signals S associated therewith to be put at stop back as far as the next interlocking or properly arranged cut section. This effect is produced by what will be termed a cascade action of the steady energy.

In this action where no out section is used, the rails of the section immediately behind the broken down insulated joint transmit the steady energy to the track relay TR at the entrance thereof. In holding its contacts continuously picked up, this relay continuously energizes the front contact repeater relay FP associated therewith and deenergizes the back contact repeater relay BP. These relays, in turn, set up the look-out circuit for the next track section to the rear. At the entrance thereof the action. just described is repeated and so on as far back as the track circuits are continuous.

In installations where the distance between interlockings is more than several blocks, it ordinarily is desirable to break up this cascade action of the steady energy. Such a breaking up can very readily be effected where cut section facilities of the character represented at location Ea in Fig. 1 are used. As there represented, these facilities consist of the single element code following track relay TR connected to receive energy from the forward portion of the divided signal block, a repeater relay BP controlled over the back contact H] of relay TR, the usual track transformer T1 connected to the rails which constitute the rear portion of the divided signal block through current limiting reactor 6, and contacts 43 and 4,4 respectively carried by the relays TR and BP and arranged to control a connection of the primary winding of the track transformer with the alternating current power source BC.

In operation of the facilities shown at out section location Ea, relay TR follows the cod ing of the energy which it receives from forward location F and thus causes slow release relay HP to hold its contact M continuously picked up as long as this code following operation takes place. This sets up the circuit over which contact 53 of relay TR periodically makes and breaks the primary current supply circuit for transformer TT. Each time, now, that relay TR picks up in response to a pulse of forward circuit energy, the rails to the rear of location Ea receive a pulse of energy from transformer TT. Likewise, each time that relay TR releases its contacts, this supply of energy to the rear circuit is discontinued. In

this manner the trackway code is repeated 7 around the insulated joints 3 which define the out in the signal block.

In case, however, that the apparatus at location F supplies steady lock-out energy to the rails of the track section Eat-36, relay TR at out location Ea remains continuously picked up, contact 44 of relay Bl? is released and the rails of track section E'-Ea are then continuously deenergized. In this manner, the before described cascading action of the steady energy is broken up. The track section to the rear of location Ea now has a continuously deenergized condition and the associated wayside signal S shows stop in the same manner as were the track section to be occupied and the rails thereof by-passed by the train wheels and axles.

In addition to repeating the trackway code and breaking up the cascade action of the steady energy, the facilities at out section Ea also automatically protect against a broken down insulated joint 3 at that location. If this breakdown is present when the forward section Ea-F is occupied, the relay TR connected to the rails thereof will, of course, receive no energy and the supply circuit for the rear section E-Ea will continuously be interrupted. As the train proceeds into the next block or beyond location F and code energy is supplied to section Ea-F, the first on period of this code picks up relay TR and until the contacts of repeater relay BP drop out energy is supplied to the rails of the rear track section over the previously referred to circuit which extends from the supply terminal B through front contact 44 of relay BP, front contact 43 of relay TR, conductor 45 and the primary of transformer TT back to supply terminal C.

In feeding back over the defective joint 3 at location Ea this energy holds the track relay at that location continuously picked up until the release period of repeater relay BP has expired. At that time the supply of energy to the rear circuit is again interrupted and upon the reception by relay TR of another pulse of coded energy from location F the sequence of .operations just described is repeated. This results in a mutilation of the code which is repeated around the defective rail joint which is of such a nature as to cause excessively long on periods of the energy impressed upon the rails of the rear track circuit.

Because of the before explained characteristics of the decoding equipment at the signal location E in the rear, this type of mutilated code is ineffective for producing a higher proceed indication'on the part of the controlled wayside signal Se. And because the frequency of the code which is repeated around the faulty joint at the cut section location is decreased rather than increased, the type of cut section facilities represented at location Ea provides safety for all applications in which the lowest frequency code is identified with the lowest or most restrictive proceed indication.

For applications wherein it is permissible that steady energy be repeated around the cut section joint into the rear track circuit, the simplified facilities shown in Fig. 2 may be employed. In these, the rear section energy is directly coded over the front contact 43 of the code following relay TR which is identified with the forward section. Not only is each on and off period of coded energy in the forward track circuit repeated into the rails of the rear track section but steady energy in the forward section likewise produces steady energy in the rear section.

As regards protection against a broken down insulated joint at this cut section, the facilities of Fig. 2 have slightly different characteristics than those shown at Ea in Fig. 1. While the forward track section is occupied by a train, relay TR is, of course, deenergized and in the event of a broken down joint the absence of supplied energy in the rear section prevents the track relay TR from being energized over the broken down joint. When, however, the train passes beyond the exit end of the forward section, the first impulse of coded energy transmitted over the forward section rails picks up relay TR, completes the energizing circuit for transformer TT and thus effects the continuous energization of relay TR over a circuit which includes the defective joint. This estabishes a lock-out circuit similar in characteristics to the look-out circuit at each of the signal locations E and F of Fig. 1.

Referring to Fig. 3, I have there shown a third form of cut section facilities which incorporate the improvements of my invention. As in the case of the apparatus shown at location Ea in Fig. 1, these facilities are suitable for use when it is desirable to break up the cascade action of the steady lock-out energy. In addition, the Fig. 3 cut section may be used where the location thereof marks the beginning of an approach locking section of track which is identified with a track switch (not shown).

Here, both a front contact repeater relay FF and a back contact repeater relay BP are used in conjunction with the code following track relay TR, and the approach locking contact 41 is arranged to be operated by relay BP. Control of the energizing circuit for transformer T1 which is connected to the rails of the rear track section is effected by means of contacts 43 and it of relays TR and BP in the same manner as at location Ea in Fig. 1. Relay FP, controlled in the samemanner as at locations E and F of Fig. 1, is additionally employed to insure that the approach locking contact 41 will be picked up only when the track circuit beginning at location Fa receives coded energy.

As regards protection against broken down joints at the cut section location Fa, the facilities of Fig. 3 have the same characteristics as those shown at Ea in Fig. 1. Also, in caseof steady energy being received from the forward track circuit, Fig. 3 has the same characteristics as Ea of Fig. 1; namely, that no energy will be fed to the track circuit to the rear of the cut section rail joints 3.

From the foregoing analysis of the lock-out circuits which are disclosed in Fig. 1, it will be seen that the three relays FP, BP and H which are controlled by the code following track relay TR at each of the wayside signal locations pick up in a definite sequential manner each time that coded energy is first received from the rails of the associated track section following the vacation thereof by the rear end of a train which is passing therethrough. That is, upon the first on period of this initially received code, relay FP is picked up over front contact l8 and conductor l2; during the off code period which follows, relay BP is picked up over back contact iii of relay TR and front contact ll of relay FF; and some time later, which is slightly longer than the duration of the second on period of the received trackway code, slow responding relay H picks up as a result of having previously received energizing current over front contact 18 of relay BP. Speaking with reference to the contacts of relay H, there is thus provided what will be termed a three point pick-up, this term referring to the fact that three periods of trackway code must be responded to by relay TR before the contacts of relay H can be picked up following each resumption of coded energy supply to the track circuit.

In controlling the look-out circuits already described, this three point pick-up performs an important function. The first action thereof sets up the steady energy lock-out circuit at contact 30, which is completed over back contact 3| of relay BP. If an insulated joint is broken down, the relay pick-up cycle advances no further as the steady energy now feeds from the rear track circuit over the defective joint and holds the track relay TR continuously energized and the controlled wayside signal S continues to show Stop-7,

If, however, the rail joints 3 are effective for performing their intended insulating functions, the second step-of the three point pick-up takes place and the supply of steady or lock-out energy to the rear track circuit is broken at contact 3| of relay BP. Duringthissecond stage, the rear section rails receive no energy at all. This is followed by the third stage which corresponds to the second on period of the resumed trackway code and during which relay H picks up. Contact 32 thereof nowcompletes the I8!) coding circuit for the rearsection track transformer. This circuit continues active as long as the track relay TR continues to effect a normal response to codedtrackway energy.

It will thus be seen that (with the advance section of track occupied) thedisclosed lock-out circuit provides inherentprotection against the giving of a false fproceed signal indication as long as the lock-out circuit remains active regardless of whether that steady energy circuit may be intermittently opened and closed. Such an intermittent condition may, of course, be in the wiring, track transformer TT, reactor 6, rail connections, the defective insulated joints 3, or the track relay TR. .111 the event of such an opening, the track relay releases; that release breaks (at contact IID'the energizing circuit for relay FF and picks up (over contacts I and II) the companion relay BP; and that pick-up of relay BP' removes (at contact 3|) the steady energy connection from the lock-out circuit and completes (at contact I8) the energizing circuit for relay-H. Before, however, relay H has time to pick up, relay Fl? releases (due to the fact that the period of release delay for relay FF is chosen to be shorter than the period of pick-up delay for relay H) and interrupts (at contact II) both the energizing andthe snubbing circuits for relay BEP. Relay BR now immediately drops out and :deenergizes (at contact I8). relay H still before the latter has had time to pick up. Hence contact 2| of relay 'H continues to hold the controlled wayside signal S at stop even though the lockout circuit is opened in the manner just described.

After such momentary opening, moreover, reclosure of the lockout circuit still does not discontinue the stop indication on the part of the controlled signal. Following such reclosure, the first pick-up of the trackrelay TR (by rear section energy leaking over the faulty rail joint in the manner already explained) picks up relay FP, restores the supply of lockout circuit energy to the rear section rails (and to the track relay 'TR) and by causing relays BP and H to stay releasedholds the controlled signal at stop. Under the stated conditions of intermittent opening and closing of the lockout circuit, therefore, no false proceed indication is produced. Still further, it is not possible under those conditions for the track relay and'the BP relay to be picked up simultaneously because once released the track relay cannot again .be picked up (with the ad- Vance track section occupied) 'unless relay BP is released (to set up a rear section energy supply connection over back contact 3 I) and once picked up and there continuously held the track relay TR prevents (at contact III) the energizing circuit for relay B? from being completed.

Referring now to Fig. l, I have there disclosed a second arrangement of circuits for effecting "the just described three point pickup action on the part-of relays FF,- BP and H. The circuits over which contact I II; of the code following relay TR supplies energizing current to the windings pf; relays and liF,.;are the full equivalent of those shown in Fig. 1. The'codedetecting relay HI, however, difiers from the corresponding relay H of the earlier figures both in its response characteristics and in the circuits over which it receives energizing current.

Whereas the relay H of Fig. l is preferably of the ordinary ferrule type providing delayed action both in the pick-up and the release operation of the contact, the relay HI ofFig. 4 is of a normal responding type which is rendered slow releasing. bythe use of a snubbing resistor 48 which is bridged across the relay winding in the usual manner. Also, instead of having but a single energizing circuit, relay HI is provided with: (l) a pick-up circuit which includes front contact I0 of'relay TR, a conductor 49, a back contact 50 of the relay itself and front contact I8 of relay BP; and (2) a separate stick? circuit which includes front contacts 50 and I8 of devices HI and BR. 7 7

An inspection of the circuit arrangement of Fig. 4 will show the operation described below when coded energy is applied to the track circuit to which the code following track relay TR is connected. The first on period of the code picks up relay TR and thereby energizes relay FP. The succeeding off period of the code,re leases relay TR and energizes repeater relay BP over the back contact II] of deviceTR and front contact of deviceFP. The second on period of the received code picks up relay TR and supplies energizing current to the winding of relay HI over the before referred to pick-up circuit which extends from the positive supply terminal over front contactIIl of relay TR, conductors I2 and 49, back contact 50 of relay HI, conductor 52, front contact I8 of relay BP, conductor I9 and the, winding. of relay HI back to the negative supply terminal.

As therelay HI picks up and opensv its back contact, the pick-up circuit .just traced is broken but the relay has been heavilyenergized thereover and hence has no difiiculty in continuing the pick-up action to the point where its front contacts close. This completes the before referred to stick circuit through which holding current is supplied to the winding of relay HI over a'path.

from a second positive terminal of the before referred to supply source through front contact 50 of relay HI, conductor 52, front contact I8 of relay ,BP, conductor I9 and the winding of relay HI back tothe negative supply terminal. Under the action of this stick circuit, relay HI holds its contacts picked up until, the circuit is broken by a release of contact I8 of relay BP. I

As shown in Fig. 4, relays FP, BP and HI may be included in the signal location equipment of a three indication automatic block signallingsystem in the same manner as are relays FP, BP and H of Fig. 1'. Thus, code following track relay TR of Fig. 4 is; connected through the. before described resonant rectifying unit 1 to receive operating energy from the rails'I and 201' a traoksection of which location K marks the entrance. In addition to contact III, which controls the remainingthree relays under discussion, it is provided with a'contact 8 which pole changes the decoding transformer DT to produce in the secondary thereof a code frequency alternating current voltage which feeds through a selective unit J I 8 0 to the winding of a code distinguishing relay I80.

'75 codingis received. Through contacts 2| and 22 relays HI and D|80 control the wayside signal Sic in the usual'manner. I

Contacts 30, 3| and 32 of relays FP, BP and HI are included in circuits through which the alternating current source 3-0 is connected with the primary winding of the rear section track transformer TT either through one of the coding contacts 15 or I80 of transmitter CT or directly to supply steady energy thereto. This rail supply circuit includes the lock-out features already described and in all other respects is identical with the correspondingly identified circuit facilities shown at location E in Fig. 1.

From an inspection of the circuits of Fig. 4 and a consideration of the foregoing description thereof, it will be apparent that from an operating point of view these are generally equivalent of the organization of circuits which is shown at location E in Fig. 1. The major distinguishing feature is the employment by code detecting relay HI of what will be referred to as a back contact pick-up circuit, this term having reference to the fact that pick-up energy for the relay is transmitted over back contact 50 thereof.

As has been seen, this energy is interrupted when the relay armature has advanced through a range of travel wherein the back contact opens. Due, however, to the momentum of the moving armature and also toa selection of circuit constants which causes the flow of pick-up current through the relay winding to be especially heavy, the pick-up movement readily continues from the point of back contact opening to the point of front contact closing and thus the relay HI operates in the manner intended. Proper performance in this respect may be assured by providing more than the usual flexibility in the contact spring (not shown) upon which is mounted the back point with which contact 50 engages in the released position. Further benefits along the same line may be provided'by making a corresponding adjustment in the spring (also not shown) carrying the front point which contact 50 engages in the picked-up position to complete the stick circuit for the relay.

One advantage of this back contact pick-up arrangement is that it permits the retardation characteristics of the relay to be determined solely by the electrical constants of its own energizing circuit and to be independent of the electrical constants of the common energizing circuit for relays FP and'Hi of which common circuit front contact ID of .relay TR forms a part. By disconnecting the winding of relay HI from this common circuit. when the relay contacts are picked up; its holding circuit is entirely independent of that common circuit and its retardation is therefore determined solely by the electrical constants of its own energizing winding.

From a further inspection of Fig. 4, it will be seen that in the event of a broken down insulated joint at location K with a train occupying the forward portion ofthe track section of which that location marks the entrance, relay HI can never be picked up to produce a false proceed indication on the part of the wayside signal Sic for the reason that it picks up only on the second on interval of code pulse energization of the track relay TR and this cannot occur with the circuit as shown in Fig. 4 when" the source of the coded energy which feeds forwardly over the defestive joint to the track relay is at the location where the defect exists. Moreover, since the HI relay requires that the track relay TR and the repeater relay BP be picked up simultaneously before it can pick up its contacts, it is evident (from the earlier given analysis of how relays TR and BP are coordinated) that an intermittent opening and closing of the look-out circuit of an occupied block will be ineffective for picking up the HI relay contact. This is an essential requirement of any lock-out circuit which is built around the single element code following track relay TR when applied to double rail electric road track circuits in the manner disclosed in each of the drawing figures.

Another feature which is peculiar to the circuit organization of Fig. 4 is theme of a second resistor unit 54 in the snubbing circuit of the back contact repeater relay BP. The purpose of this resistor 54 is to decrease the period of contact release for relay BP when the track relay TR is responding to trackway energy of the 180 pulse per minute coding. In that event, a shunting circuit for the added resistor is maintained open by a picked-up contact 55 of the code distinguishing relay Dl80. It will be noted that resistors 54 and I6 are serially connected with front contact I I of relay FP in the referred to snubbing circuit. When both of these resistors are effective, relay BP is arranged to have'a release period just slightly greater than the off intervals of the mentioned 180 trackway code.

In the event that the low speed or pulse per minute code is received and responded to by the relay TR, code distinguishing relay DI releases and closes at contact 55 the mentioned by-passing circuit for resistor 54. Under this condition, resistor I6 only is effective in the snubbing. circuit and, in consequence, the release time of relay BP is increased to a value somewhat greater than the longer spacing or off periods of the 75 code.

While not essential in all applications, the just described use of the added snubbing resistor 54 is a further refinement which has been found somewhat to improve the operating characteristics of the circuits in applications where conditions are especially critical. In other words, by splitting the snubbing resistor for relay BP into two portions, as represented in Fig. 4, it is possible more fully to guarantee that the lock-out circuit which this relay aids in controlling will operate positively under all conditions.

In situations where the peculiar advantages and operating features of the just described back contact pick-up for the code detecting relay are not required or desired, use may be made of oneor another of the three alternative forms of energizing circuits which are disclosed in Figs. 5, 6 and '7. In all three of these figures the three relays FP, BP and Hi are shown as being applied to a three indication signaling system which is comparable to that previously described in detail in connection with Figs. 1 and 4.

Thus, in Fig. 5 the equipment is associated with a code following track relay TR which receives operating energy from the rails of the track section of which location M forms the entrance; in Fig. 6, the track relay TR is also shown as being of the direct current type receiving through resonant transformer unit 1 operating energy from the rails of a track section of which wayside signal location 0 marks the entrance; and in Fig. 7, the three relays under consideration are associated with an alternating current track relay TR of the single element code following type which receives energy from the rails of a track section of which signal location Q marks the entrance.

Referring first to Fig. 5,-the equivalentof the backcontact pick-up circuit for relay HI is provided through the use of a pick-up circuit which includes front contact 8 of the track relay TR, conductor 23, a rectifier 51, conductors 60 and 52, front contact I8 of relay BP, conductor I9 and the winding of relay HI. In effect this pickup circuit is connected in multiple with the circuit over which the upper portion of the primary of the decoding transformer DT is supplied with energizing current. The rectifier 51 is included for the purpose of preventing the energy which a stick circuit for the relay HI transmits from interfering with the operation of the decoding transformer and also to prevent reverse inductive kicks from the transformer from tending to deenergize the relay.

This stick circuit is a duplicate of that shown in Fig. 4.- with the exception that a resistor 58 is included therein for the purpose of cutting down the current from the relatively high value necessary in the arrangement of Fig. 4 to a lower value which is adequate for operating the relay by means of the arrangement of Fig. 5.

As in the case of Fig. 4., the three point pickup actionis produced by the circuits of Fig. 5.

That is, the first on period of coded energy initially received by relay TR picks up contact repeater relay FP; the following off period of the code causes back front contact repeater relay BP also to be energized and picked up; and the second on period of the received code completes the pick-up circuit for relay HI which has now been set up by front contact I8 of relay BP. This circuit may be traced from the positive supply terminal through front contact 8 of relay TR, conductor 23, rectifier 51, conductors 69 and 52, front contact I8 of relay BP, conductor I9 and the winding of relay HI back to the negative supply terminal.

In picking up, contact 59 of relay HI now completes the stick circuit through which the winding receives current which holds it continuously picked up until such time as contact I8 of relay BP may be released. This stick circuit may be traced from the positive supply terminal through resistor 58, front contact 50 of relay HI, conducis a front contact repeater for relay HI. It is an ordinary acting relay and carries the contacts H and 32 which are included respectively in the signal control and code selecting circuits of the associated signal location equipment and which perform the same functions as the correspondingly numbered contacts of relay HI in the systems of Figs. 4 and 5.

The winding of this fourth relay HP receives energizing current over a front contact GI of relay HI. Relay HI, in turn, is provided with a pick-up circuit which includes front contact I9 -is,-the first -on period of coded trackway energy which is initially received by track relayiTR picks up repeater relay FP over front contact III; the following off period of the code picks up repeater relay BP over back contact I and front contact II of relay FF; and the second on period of the received trackway code picks up relays HI and HP in rapid succession.

The pick-up circuit for relay HI may be traced from the positive supply terminal through front contact In of relay TR, conductors I2 and 49, back contact 62 of relay HP, conductor 63, front contact I8 of relay BP, conductor I9 and the winding of relay HI back to the negative supply terminal. In picking up, contact 6| of relay HI picks up repeater relay HP over a circuit which extends from the positive supply terminal through front contact 6|, conductor 64 and the winding of relayv HP back to the negative supply terminal.

In picking up, contact 62 of relay HP interrupts the pick-up circuit for relay HI and completes for that relay a stick circuit which extends from the positive supply terminal through resistor 58, front contact 62 of relay HP, conductor 63, front contact I8 of relay BP, conductor I9 and the winding of relay HI back to the negative supply terminal. By virtue of the delayed release characteristics imparted by the snubbing resistor 48, relay HI readily bridges the short interval of time that contact 62 of relay HP requires to shift from the released to the picked-up position.

Referring next to Fig. 7, I have there represented a third scheme for eliminating the back contact pick-up on the part of relay HI. In

this scheme, a third or additional contact 66 is provided on the track relay TR and it, together with contact I9 of relay BP, is included in the pick-up circuit for relay HI. In addition to this pick-up circuit, relay HI is provided with a stick circuit which is a duplicate of that shown in Fig. 5.

Like the arrangements of Figs. and 6, the

circuit organization of Fig. 7 retains the three point pick-up characteristics. That is, the first on pulse of coded trackway energy initially received by relay TR picks up repeater relay FP; the following off period of the code picks up repeater relay BP; and the second on period of the received code picks up relay HI over a circuit extending from the positive supply terminal through front contact 66 of relay TR, conduc tors 61 and 52, front contact I8 of relay BP, conductor I9 and the winding of relay HI back to the negative supply terminal. In picking up, contact 5B of relay HI completes the stick circuit for that relay which may be traced from the positivesupply terminal through resistor 58, front contact 50 of the relay, conductor 52, front contact I8 of relay BP, conductor I9 and the winding of the relay back to the negative supply ter- .rninal.

It has already been pointed out that under certain conditions steady or uncoded energy may be supplied to the rails of certain of the track sections. of each of the coded signalling systems described herein. These conditions are not restricted to the lock-out functioningof the rail supply circuits in the event of broken down rail joints but they also include detection functions of one form or another. One example of the latter may involve the control of highway crossing signals which are associated with a cut section location intermediate the ends of a signal block length of the protected track stretch. I

For applications to track sections which are supplied at times with such steady detection energy, prior art coded systems of all types known heretofore are subject to the disadvantage of producing a momentary false approach indication on the part of the controlled signal S in the event that a following train enters the track section and shunts the track relay during the time that the steady or uncoded energy is being received. This is for the reason that immediately preceding such a shunting, the contacts both of the track relay TR and of the repeater relay F1? are picked up under the control of the steady energy then being supplied to the trackway.

W'hen, now, the mentioned shunting does occur, the resulting release of the track relay completes, at contact II], the energizing circuit for the second repeater relay BP and thereby picks up this relay. When, as in the referred to prior art systems, this relay BP directly picks up the code detecting relay H without delaying its response, the controlled wayside signal is thereby caused to interrupt the stop indication (which should be displayed continuously) and to give a false approach indication for a period equal to the release time of the repeater relays FF and BP.

In the improved arrangement disclosed in each of Figs. 4, 5, 6 and 7 (and in Fig. 1 also), this false approach indication is prevented since, under the conditions stated, only two of the three steps required for the energization (or pick-up) of the signal controlling relay HI (HP in Fig. 6 and H in Fig. 1) have been performed. The necessary cycle and one-half of received code not being simulated, the H relay maintains its contacts continuously released and in consequence the stop signal indication is not interrupted.

The benefits just stated for the systems of Figs. 4, 5, 6 and '7 are also realized from the embodiment of my invention which is disclosed in Fig. 1. Although there the code detecting relay H is solely controlled by the second repeater relay BP, that relay H is a slow responding device. Since in the system of Fig. 1 the period of pickup delay of relay H is longer than the release delay of the repeater relays FF and BP, the three point pick-up characteristics of the arrangements of Figs. 4, 5, 6 and 7 are simulated and the desired interruption of the stop signal indication is prevented.

Referring next to Fig. 8, I have there represented a modification of the cut section facilities shown at location Ea in Fig. 1. In this modification of Fig. 8, a front contact repeater relay FF is substituted for the back contact repeater relay BP of Fig. 1, and coding of the energy supplied to the rails of the rear track section is effected over the back instead of the front point of contact .3 of the code following track relay TR which is operated by energy received from ahead. This arrangement also breaks up the cascade action of the steady energy which at times, as in the case of lock-out circuit operation, is impressed upon the forward section rails.

In case such steady energy is received from ahead, contact 43 of relay TR is continuously picked up and the track section to the rear accordingly receives no energy at all. When coded energy is received from ahead, it will be apparent that each off period thereof produces an on period of the code repeated in the rear track section by virtue of contact 43 completing the rail energizing circuit when in its released position. Likewise, each on period of the received code produces an off period of the code which is repeated in the rear track section.

As regards protection against broken down rail joints at location Ea, the facilities of Fig. 8 have slightly different characteristics than those shown at the corresponding cut section in Fig. 1. In the event of such a faulty joint, the track relay TR still responds to each on period of coded energy received from ahead and by periodically energizing relay FP over contact 10, it causes that relay to maintain its contact 44 continuously picked up. However, during each off period of the code received from the forward track circuit, what is termed a door bell code will be fed to the rear track circuit when a broken down joint is present at the cut section location.

This door bell code is always of a considerably higher frequency than the normal '75 and 180 codes used in the train control systems. Ordinarily it will vary within the range of from 300 to 600 cycles per minute and from a test of commercial apparatus arranged as shown in Fig. 8 the frequency of the door bell code was found usually to be within a few percent of 500 cycles per minute or approximately 8 cycles per second. The following actions are involved in its production.

As back contact 43 of relay TR releases and completes the rail supply circuit for the rear track section, the resulting energy transmitted thereto feeds over the defective rail joint 3 at the cut section location Ea and is transmitted by circuit 1 to the winding of track relay TR. In responding, this relay frequently does not pick up completely but rather raises its contacts only to the point where contact 43 breaks the rail supply circuit. Once this happens, the supply of joint leakage energy is cut off from relay TR and contact 43 again completes the rail supply circuit. The cycle of operation just described is rapidly repeated and as a result the high frequency door bell code is produced continuously during each off period of the coded energy which is received from the forward track circuit.

Inasmuch as the decoding equipment of both the wayside and locomotive signal control facilities is incapable of responding to the individual pulses of this high frequency door bell code, it ordinarily will have the same eifect thereon as a continuous pulse of track circuit energy. In consequence, the equipment to the rear of the cut section location Ea of Fig. 8 will continue to receive a code of the same fundamental frequency (75 or 180 cycles per minute) as that which is effective in the track circuit ahead of the cut section location. The rear section code differs, however, in that each off period thereof corresponds to an on period of the forward section code and further in that each on period of the rear section code is made up of door bell pulses instead of the simple 100 cycle alternating current waves from source B-C.

In situations in which the decoding equipment which is influenced by this rear section energy responds to the on periods in the same manner as were they of the usual 100 cycle wave, the cut section facilities of Fig. 8 are as effective as those shown at location Ea in Fig. 1. In certain applications, however, it has been found that the just described door bell code may produce a false approach wayside indication at the entrance of the signal block in which the cut section is included and may also give a false proceed indication in the locomotive equipment.

steady energy to the trolling effects by door bell code, I propose to modify the basic back contact code receiving arrangement of Fig-8 in the manner represented in Figs. 9 and 10. Referring to Fig. 9,

I-have there represented a stretch of track l-2 which includes a signal location Xof the usual wayside type and which marks the entrance of a block including a cut section Xa, shown as being-occasioned by an intersecting {highway- 10. with'which the usual crossing protective signals XS: are associated. Operation of these signals is controlled by a pair of interlocked relays -XRl and XR2 of the usual type.

Considering first the cut section equipment at location Xa of Fig. 9, it is arranged to be used where the cut section is associated in the manner thereishown'with control facilities for highway crossing signals XS or is the starting point for approach locking of the character discussed in connection with Fig. 3. Both front contact and back contact repeater relays FF and Bl? are controlled by contact I I] of the code following relay TR in a manner, before explained, which causes the contacts of relay BP to be picked up'only when relay TR responds to a trackway code.

This relay BP at location Xa is provided with contacts 44 and 41 which are respectively included in the circuits through which energy is supplied to the rails of track section XXa and over which the winding of interlocking relay XR2 is controlled. The latter circuit also includes a contact H of relay PP. The former is providedwith facilities including a back point engageable by" contact 44 for at times feeding rails of the rear track section XXa.

In operation of the cut section facilities shown at X0. in Fig. 9, coded energy received from the rails ahead of the insulated joints 3 produces code following response on the part of relay TR. This relay now maintains relays Fl? and BP picked up and, under the action of back contact 43, repeats coded, energy into the rails of the track section to the rear of the mentioned joints. Thisv energy is similar to the forward section code'except that each ofi period thereof corresponds to the on period of that advance code and each on period of the rear section code corresponds to an off period of the forward code. When no energy is received by the relay TR, as in the event that the section ahead of location Xa is occupied, the contacts of all three of the relays TR, FF and BP are released and steady energy then is supplied to the rails of the rear section over a circuit which extends from supply terminal B through back contact 44 of relay BP, conductor 45 and the primary winding of tracktransformer TT back to supply terminal C.

.Should one. of the insulated joints 3 at location Xa break down, back contact 43 of relay TR would act (in absence of means for preventing such action), in the manner described in connection with Fig. 8 (i. e. when a train backs into the section of track of which the faulty joint marks the entrance), to produce the high frequency door bell code. In order to prevent this production I insert in the energizing circuitof back contact repeater relay BP a re actor 12 whichis effective to cause relay BP to release its contacts whenever contact ID of relay TR operates at the high frequency door bell rate which ordinarilyapproximates 8 cycles per second. One effect of such a release is to insure that the just traced steady energy or lock-out circuit will be established even though the high frequency door bell code which normally tends to hold relays FF and BP picked up, starts in the manner already explained.

The inserted reactor 1'2 is so dimensioned electricallythat it; has yery little inductive effect upon currents of the low approach and clear code frequencies of and cycles per minute '(one and one-fourthand three cycles per second, respectively). This assuresthat when relay TR responds tothe approach code, the winding of relay BP will receive'practically full normal energizing current and thus hold its contacts picked up during the longest on period of this approach or '75 code. Likewise, when the track relay TR operates in response to the 180 cycle per minute or 3 cycle per second code, the reactor 72 still presents only a "comparatively'small amount of impedance and thus does not reduce the intensity of a energization of relay BP to a point where that relay is incapab le of bridging the longest onfperiod of the 180 code. Inasmuch as the length of this period is considerably less than that of the corresponding period'of the 75 code, the somewhatlesser amount of energy received by therelay BP does not cause improper operation. 1 I

In the case, however, of thehigh frequency door bell codev (which approaches .8 cycles per.

second), the reactor 12 offers such a considerably increased. impedance to the flowof current that relay BP is incapable of picking up its contacts in response to this code. This increased in accordance with the well-known variation of inductive reactance. component. thereof as the square of thefrequency of the applied voltage. For example. the referred to tests show .that

at the door bell frequency-of 8 cycles per secend the impedance of reactor- (Z isof the order of 6.4 .as much as at the approach code frequency of one and one-fourth cycles per second.

The same tests show that the cycles of this door are approximately equal on and bell code off. i g It'will thus beseen that the use of reactor 12 in the'manner' represented in Fig.8 assures that the door bell code will be ineffective for picking up relay,BP and thus interfering. with.-

the desired operation of the steadyenergy or lock-out circuit of which back contact 44 of relay BP forms a part;

An equivalent result may be obtained by using the reactor in themodified manner indicated at 12min Fig. 10. When this arrangement is used, both of the relays FF and BP will receive less than normal energy on the door bell code and hence neither one can then pick up.

will receive. proportionately less energy. and canimpedance on the higherfrequency is, of course,;

not under this condition hold its contact picked up for a tirne equalto the energizing period. @Cgmsidering next the equipment shown at signal location X in Fig. 9, this form of apparatus organization is used where the section in advance of the signal Sr is at times fed steady energy for use in controlling highway crossing signals of the character shown at XS. It will be seen that this location X equipment is a modification of the basic apparatus organization represented at location E in Fig. 1. As here shown, moreover, the arrangement of the various devices which the organization at location X of Fig. 9 includes is similar to that disclosed and claimed in a copending application Serial No. 282,185 filed June 30, 1939 by Ralph R. Kemmerer on Railway signaling systems. The two contacts 8 and II) of the code following track relay TR respectively control operating circuits for code distinguishing relay DI and for the relays FP, BP and HI. Relay HI, in turn, will be seen to be controlled in a manner comparable to that discussed in connection with Figs. 4 and 6.

The control circuits for the three lamps of wayside signal Sac include contacts 2I and 22 of relays HI and DIBI] arranged in the same manner as has been previously described in connection with the preceding figures. Likewise, the circuits through which alternating current source B-C supplies primary winding current to the track transformer TT connected to the rails of the track section in rear of location X are identical to the corresponding circuits of Figs. 4, 5 and 7 and closely comparable to the code selecting and lock-out circuits of Figs. 1 and 6. As will be seen, they include contacts 30, 3| and 32 of the relays FP, BP and HI and contacts I5 and I89 of the coding device CT.

Interposed between relays FP, BP and HI and the code following contact I9 which controls these relays are a pair of auxiliary repeater relays PFa and BPa which are so arranged that relay TR must respond to two code periods (an on and an off) before the three point pickup circuits of relays FP, BP and HI are rendered effective. In other words, a total of five code periods must be responded to before code detecting relay HI picks up its contacts. This further delay is introduced to take care of certain conditions which involve the control of the highway crossing signals XS. The control in accordance with these conditions is effected through the medium of a contact I6 carried by relay FPa' and included in the energizing circuit of crossing signal control relay XRI. Also included in this circuit is a line conductor I1.

Further regarding the reasons for the further delay just mentioned, it is necessary in order that the steady energy which the facilities at out section location Xa at times supply to the rails of track section X-Xa (to silence the crossing signals SX) will be ineffective for causing the look-out circuit at location X to become active and thus repeat the energyinto the trackrails behind location X when both of the joints 3 at that location are performing their insulating function in the manner intended. The referred to five point pick-up action is effected by the apparatus of Fig. 9 in the following manner.

The first on period of trackway code initially responded to by relay TR at location X picks up relay FPa over a circuit which extends from the positive supply terminal through front contact III of relay TR, conductors 49 and I8, back contact I9 of relay FP, conductor BI and the winding of relay FPa back to the negative supply terminal. The following off period of the received code picks up relay BPa over'a circuit which extends from the positive supply terminal through back contact II) of relay TR, door bell code protecting reactor I2, conductors I3 and I3,

back contact II of relay FP, conductor 82, front contact 83 of relay FPa, conductor 84, and the winding of relay BPa back to the negative supply terminal. Relays FPa and EH]. are made sufficiently slow releasing to bridge single periods of the trackway code. This delay may be provided in any suitable manner, as by use of snubbing resistors 85 and 8B.

The second on period of the trackway code to which relay TR responds picks up relay FP over a circuit which may be traced from the positive supply terminal through front contact II] of relay TR, conductors 49 and 88, front contact 89 of relay BPa, conductor 90, back contact SI of relay HI, conductor I2 and the winding of relay FP back to the negative supply terminal.

During the 01f period of the received trackway code which follows, contact III of relay TR picks up relay BP over a circuit which extends from the positive supply terminal through back contact III, reactor I2, conductors I3 and I3, front contact II of relay FP, conductor I4 and the winding of relay BP back to the negative supply terminal.

Finally, on the third on period of the received trackway code, relay HI is picked up over a circuit extending from the positive supply terminal through front contact ID of relay TR, conductor 49, back contact 59 of relay HI, conductor 52, front contact I8 of relay BP, conductor of heavy energization, relay HI completely picks up its contacts in the same manner as was explained in connection with the back contact pick-up action of Fig. 4 and locks itself in over a circuit which extends from the positive supply terminal through front contact 50 of relay HI, conductor 52, front contact I8 of relay BP, conductor 'I9 and the winding of relay HI back to the negative supply terminal.

In picking up, contact 9| of relay HI interrupts the circuit over which the winding of relay FP received its initial pick-up energy. This interruption, however, does not cause relay FP to drop out for the reason that in picking up a tinue to flow to the winding of relay FP. The

circuit for relay FP which is now active may be 'tracedfrom the positive supply terminal through front contact ID of relay TR, conductors 49 and I8, front contact I9 of relay FP, conductor 93, front contact 92 of relay BP, conductor I2 and the winding of relay FP back to the negative supply terminal.

For the purpose of modifying the response characteristics particularly in respect to the release delay period of relays FF and BP when the received trackway code is of the '75 pulse per minute frequency, the code distinguishing relay DI80 is provided with a pair of contacts 95 and 96, which, at all times except when the relay is picked up in response to a reception of the trackway code, connect a pair of resistors 91 and 98 in modifying relation with the snubbing circuits of the repeater relays FF and BP. When arranged in the manner shown, the effect of these resistors is comparable to that of the added That is, the period of. release delay of the relays FP and BP is extended during conditions of trackway code reception over that which is effective during conditions in which the trackway code which operates relay TR has a frequency of energy pulses per minute.

The various component parts of the signalling equipment. shown in Fig. 9 having been described, attention will now be directed to the manner in which the apparatus of Fig. 9 operates. As long as the track stretch |2 is vacant, signal location apparatus (not shown) ahead of the cut section Xa supplies train control energy of the 180 code to the rails of the section of which Xa marks the entrance. At this location the facilities represented in Fig. 9 repeat this code into the rails of track section XXa. At signal location X, code following relay TR responds to this energy and causes all six of the relays controlled by contacts 8 and III to be continuously picked up. This causes wayside signal Sa: to display the clear or green indication and. the rails of the track section to the rear of location X to receive train control energy of the 180 coding.

As a train proceeds through the stretch of track represented in Fig. 9, the shunting action of its wheel and axles in entering section X-Xa deenergizes relay TR at location X and causes all six of the associated relays to release their contacts. In breaking the energizing circuit for relay XRI, contact 16 of relay FPa causes the highway crossing signals XS to be placed in operation by virtue of their operating circuits being completed at contact 99 or relay XRI: At location X, the wayside signal now shows the red or stop indication and the rails of the track section to the rear are supplied with energy of the '75 coding as a result of contacts 39 and 31 of relays FF and BP being released.

As the train advances beyond cut section location Xa it shunts relay TR at that location. This effects the release of relays FF and BP and contact 44 of relay BP now connects transformer TT continuously to the power source terminals BC, thereby introducing steady energy into the rails of the track section X-Xa. As the rear of the train clears location Xa this steady energy is transmitted back to relay TR at location X.

In picking up, contact ill of that relay completes the energizing circuit for relay FPa which in turn picks up and at contact 16 completes the circuit for highway signal control relay XRI. This relay picks up contact 99 and thereby discontinues operation of the crossing signals XS. This particular action is made possible because of the mechanical interlock (not shown) between contact 99 and companion contact I09 of relay XRZ which is arranged to prevent contact from releasing as long as contact 99 is released and also after it is again picked up until such time asv the winding of relay XR2 has again been energized.

The steady energy referred to above is ineffective, however, for picking up any of the relays FP, BP, HI. and D|89 and for this reason, signal Sa: continues to show stop and rails of the track section to the rear of location X continue to receive energy of the 75 coding as long as any portion of the train remains within the signal block of which location X. marks the entrance. I

When the rear of the train has cleared the end. (not shown in Fig. 9) of this signal block, energy ofthe. 75 coding is again received at location Xa and repeated by the facilities there installed into the rails to the rear of this location.

At the cut section, relays FF and BP are picked up and the energizing circuit for the winding of relay XRZ is completed over contacts, H and 41 thereof. This restores the mentioned interlocking mechanism to a condition in which either contact 99 or I00 may be released to the highrear of location X receive energy of the 180' codingover a circuit which includes front contacts 3! 3| and 32 of relays FP, BP and HI.

In the event that the cut section apparatus at location Xa in Fig. 9 should not be provided with the door bell code eliminating reactor 12 (or 72a of Fig. 10) it is desirable that the signal location equipment to the rear of this cut section include provision for protecting against the undesirable efi'ects of such door bell code which may be produced at the cut section and transmitted'by the rails I and 2 to the track relay TR at location X. To this end, the signal location equipment under discussion is represented as including a reactor 12 connected in a manner equivalent to that shown at the cut section Xa.

The manner in which this reactor effects the desired protection is identical with that previously described in connection with the cut section description, namely, it offers such an increased impedance to the fiow of current at the high door bell frequency as to make it impossible for relay BP to be picked up when the door bell code is received. In addition, auxiliary repeater relay BPa is also incapable of'pick-up under the conditions stated for the reason that the reactor 12 also forms a part of its energizing circuit. This, of course, meansthat repeater relay FP must also remain released and in consequence a reception of the door bell code does not interfere with the supply to the rear track section of energy of the 75 coding over a circuit which includes back contact 3! of relay 3?.

If desired, of course, the equipment at location X in Fig. 9 may also include the protective reactor connected in the manner shown at 12a in Fig. 10. In this case it would be impossible for door bell codes to pick up any of the relays in the group FPaHi for the reason that the reactor 12a is included in the pick-up circuit of each and every one.

Regarding the protection against broken down insulated joints at location X, the equipment of Fig. 9 operates in a manner which, for all practical purposes, is identical with that explained in connection with the earlier figures. Should such break-down occur and cause the coded energy supplied to the rear track section to befed to the forward section track relay TR, the first on pulse of this energy picks up relay FPa, the following off period picks up relay BPa, the second on period picks up relay FP.

Contact 30 of relay FP now completes the lockout circuit over which the rails of the rear section receive steady energy. In feeding over the defective joint this energy holds relay TR continuously picked up and thus prevents relay BP from responding. Both relays Hi and DEBS, in

consequence, remain released and the signal SIL' displays the stop or red indication until the defective joint is repaired.

It will be noted that upon the expiration of the release period of relay BPa, its contact 89 drops out and interrupts the pick-up circuit for relay FP. To prevent that relay from then also dropping out and interrupting the lock-outcircuit, it is provided with a contact I06 which completes for the relay a stick circuit over which the relay winding continuously receives energy as long as relay TR remains picked up. This stick circuit may be traced from the positive supply terminal through front contact I!) of relay TR, conductors 49 and 18, front contact I06 of relay FP, conductor 90 .and the winding of relay FP back to the negative supply terminal.

Even though the door bell code protecting expedients of Figs. 9 and 10 have been disclosed in an application involving alternating-current track circuit territory, it will be appreciated that these same expedients are also applicable to direct current track circuits where the direct current code-following track relay is connected directly to the rails. In that situation, as in the one herein disclosed, the starting of door bell action at the cut section following the breakdown of both of the two insulated joints at that location initiates the same sequence of operations that have been described in connection with Figs. 9 and 10 and prevents the giving of false signal indications in a manner which is the same as that explained herein for the application to alternating current track circuits.

A similar comment may be made relative to all of the improved features and forms of apparatus organization which form the subject matter of this application and which have been disclosed as forming parts of electrified territory installations. All are equally applicable to steam road territory employing either alternating current or direct current track circuits and using track relays of any code following type in place of the single element designs herein shown.

From the foregoing it will be seen that I have provided new and improved forms of organizations of railway trafiic controlling apparatus into signalling systems wherein coded energy normally is supplied at all times to the track circuits for the purpose of controlling either or both wayside signals and train carried cab signals. All of these organizations are effective to prevent the controlled wayside signals from giving false "proceed indications in the event of breakdown of the insulated joints which electrically separate the rails of adjacent track sections.

This protection is effected without staggering the polarities of adjacent track circuits and without the necessity for use of two element track relays. When brought into action, the protection facilities cause the wayside signal at the location of the defective joint to show stop even before the track block which is guarded by this signal becomes vacated and in addition the facilities operate to continue this stop indication uninterrupted until the broken down joint is repaired.

Moreover, the facilities are so arranged that should the supply of steady lock-out energy which feeds over the defective joint be momentarily interrupted, the protection above discussed will automatically restore itself without producing even a temporary approach or clear indication on the part of the affected wayside signal. Failure of the facilities as a result of accidental improper operation of the relay contacts and the conductors which are included in my improved lock-out circuits is also effectively guarded against.

I have also provided cooperating cut section facilities which are effective to break up cascading action of the steady track circuit energy which is used under lockout conditions, to detect and prevent undesired false operating effects of a breakdown of the insulated rail joints at the cut section location, and to take care of the conditions which the presence of high frequency door bell codes introduce.

In connection with the above, I have provided improved recoding facilities for controlling the wayside signals and for selecting the coding of the energy which is supplied to the track circuits. Still more important, I have accomplished all of the above without dispensing with any of the desirable features of continuously coded track circuits.

Although I have herein shown and described only a comparatively few of the many possible forms of railway traffic controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:'

1. In combination with adjoining forward and rear sections of railway track which are electrically separated by insulated rail joints, means for supplying coded energy to the rails of said forward section, a code following track relay operated by energy received from said rails, a first slow release relay energized when said track relay is picked up, a second slow release relay energized when said track relay is released provided said first slow release relay is picked up, a signal positioned at the entrance of said forward section, means including said track and slow release relays for controlling said signal in such manner that it displays a permissive indication when the track relay is following code and a restrictive indication when the track relay is either picked up or released continuously, an energizing source for said rear track section, a coding contact, a circuit completed over a back contact of said second slow release relay only for connecting said rear section rails to said energizing source over said coding contact, and a circuit completed over a front contact of said first slow release relay and a back contact of said second slow release relay and effective to connect said rails directly to said energizing source in the event that energy should feed over said insulated rail joints from the rear track section into the forward section.

2. In'combination with adjoining forward and rear sections of railway track which are electrically separated by insulated rail joints, means for supplying coded energy to the rails of said forward section, a code following track relay operated by energy received from said rails, a first slow release relay energized over a front contact of said track relay, a second slow release relay energized over a back contact of the track relay and a front contact of said first slow release relay, a code detecting relay energized when said second slow release relay is picked up and deenergized when that relay is released, a signal positioned at the entrance of said forward section and controlled by said code detecting relay in a manner that it displays proceed .when

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