US2177090A - Approach control apparatus for railway signaling systems - Google Patents

Description

Oct. 24, 1939. H, G. BLOSSER APPROACH CONTROL APPARATUS FOR RAILWAY SIGNALING SYSTEMS Filed Aug. 17, 1938 HIS Patented Oct. 24, 1939 APPROACH CONTROL APPARATUS FOR RAILWAY SIGNALIN G SYSTEMS Herman G. Blosser, Pittsburgh, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application August 17, 1938, Serial No. 225,371

12 Claims. (Cl. 246-38) My invention relates to approach control apparatus for use in railway signaling systems of the coded track circuit class and it has special reference to the employment of such apparatus accidental failure of its trackway supply connections.

In the several views of the drawing like reference characters designate corresponding parts.

for approach controlling various signaling func- Referring first to Fig. l, the improved approach 5 tions without the use of line wires. control apparatus of my invention is there dis- Genemlly stated the Object o my invention is closed in association with a coded track circuit to improve Certain features o an pp COIlsystem of automatic block signaling for a railtrol without line wire scheme wherein the rails ay track 2 over which t n h assumed th t :gliO 0f eaeh unoccupied Signal block length of track traihc moves in the single direction indicated by transmit cede step pulses of auxiliary enersyforthe arrow, or from left to right in the diagram. Wardly from the block entrance t0 effect the The protected stretch of this track is divided ergization of a slow release approach relay at the into t customary Successive Sections by insw block eXitlated rail joints 3 and the rails of each section :7 5 A more Specific Object is to P Wide Simplified form a part of a track circuit to which coded siga s for S pp y the referred 130 pulses. of nal control energy is supplied in customary manauxiliary energy to the entrance end of each track circuit without wastage of power and with- In t View of Fig 1, reference characters 1) out interfering with the normal code following and E respectively i n t th entrance and operation of the S gna g System track reliiy at the exit ends of one of these track sections which 20 that location. is illustratively shown as being a full signal Another object is to increase t e a u With block in length; character TR designates a code which the len h f hes code s p pulses of following track relay which is installed at the y energy y be Controlled-- entrance end of the section and operated by en- An additional Object is to provide pulse pp yergy received from the rails thereof; character 5 mg apparatus Which incorporates Various Safety TB a track battery or other direct current source and Self Protecting featuresprovided at the section exit for the purpose of In practicing y invention 1 attain the above supplying these rails with the relay operating and Oth Obj cts and advantages y employing energy just referred to; character CR. a coding an impulse relay which transfers the entrance device having a nt t 5 hi h cod this en- 30 end connection of the track circuit from the sigergy by periodically interrupting the rail supply naling system track relay to a source of auxcircuit; and character S the usual wayside signal i y energy t th b g nnin f ch f code which guards the entrance of each of the track period; by r i in this impul r l y d y blocks and which is controlled by the associated over a front contact of the track r y; by giv track relay TR through the medium of decoding 35 the impulse relay a slowness of release which asapparatus |0 sures that the transferred track circuit connec- An automatic hioek ignaling ystem of th tion will not be returned to the track relay until referred t d d track ircuit type operates just before the beginning Of t e n code without the aid of line wires and in representap i y d r v n pic p curr t f r h mtive form it includes all of the elements above 40 pulse relay f the xi y ner y r e; n named. Such a system further comprises the b protecting th track r y a a s bell ac n customary facilities (not shown) for continuousin the event of accidental failure of its trackway 1y operating each of the exit end relays CR at one supply connections. or another of the usual plurality of distinctive 45 I shall describe a few forms of approach concode rates. Selection among these rates (which trol apparatus embodying my invention and shall in a typical three indication system may conthen point out the novel features thereof in sist of '75 and 180 energy pulses per minute) is claims. These illustrative embodiments are dismade in accordance with advance traflic condiclosed in the accompanying drawing in which: tions by the decoding apparatus I0 functioning 50 Fig. 1 is a diagrammatic representation of a in customary manner.

single section of railway track which is equipped This decoding apparatus (details not shown) with one preferred form of my improved nonis controlled in the usual fashion by the assoline wire approach equipment; ciated track relay TR and it performs the fur 5 5 Fig. 2 is a similar showing of entrance end therfunction of selectively setting up the lightfacilities wherein the impulse relay derives picking circuit for one or another of the lamps (G, up current from the auxiliary energy source; and Y and R in the typical three indication system Fig. 3 is a diagrammatic view of entrance end above referred to) of the wayside signal S at the facilities still further modified to protect the same location. In the arrangement represented, wot rack relay against bell action" in the event of these signal lamps derive energizing current from trol a power source which is designated by the terminals plus and minus.

For applications in which train carried cab signals (not shown) also are to be controlled, the representative coded signaling facilities may still further comprise means at the exit end of the track circuit for additionally supplying the rails thereof with coded alternating current energy. In the form shown at location E in Fig. 1, these means include a track transformer TT having a secondary winding which is connected with the track rails over coding contact of device CR during each energy on period of the mam track circuit code from battery TB. At proper times the primary winding of this transformer 'is energized over a conductor I from a suitable alternating current source designated by the terminals B and C.

In order that certain functions of the signaling system may be rendered active only upon the approach of a train, the apparatus installed at each of the signal locations D, E, etc., is supple- 'mented by an approach relay AR which is arranged to maintain the referred to functions inactive at all times except when the section of track to the rear of the location becomes occupied. In the illustrative arrangement which is shown at location E in Fig. 1, these approach controlled functions consist in lighting the wayside signal Se (normally dark) and in supplying the rails of the track section to the rear of that signal with coded alternating current energy for cab signal control.

The former function is governed by a contact 9 of the approach relay AR and the latter by a companion contact II thereof. Either of these functions may, of course, be controlled individually by the approach relay and it will be apparent, moreover, that signaling functions other than or in addition to those just named may likewise be governed by the same relay.

When applied to coded signaling systems of the conventional character just considered, the improved approach control apparatus herein disclosed renders the relay AR at each signal location responsive to the approach of a train and does this, moreover, without the use of line wires. For each of the signal blocks this approach conapparatus comprises: (1) entrance end facilities which supply the rails of that block with pulses of auxiliary energy which are in step with the recurring off periods of the received signal control code and (2) exit end facilities which receive these auxiliary pulses from the rails and energize the approach relay AR in step with them.

In the form shown at location D in Fig. 1, my improved entrance end facilities comprise a battery or other source of auxiliary energy AB, an impulse relay IR which transfers the connection of the track rails I and 2 from the track relay TR to battery AB during each off period of thereceived signal control code (in a manner similar to that disclosed and claimed by a copending application Serial No. 222,014 filed July 29, 1938, by Herman G. Blosser), and means including a contact I2 of relay TR for supplying the impulse relay IR with pick-up energy at proper times.

This impulse relay is provided with a contact I3 which occupies the lowermost position (shown in full lines) under conditions of relay deenergization and then serves to connect the operating winding of the track relay TR directly across the track rails I and 2. When, however, relay IR becomes energized, it moves contact I3 upwardly into the picked up position (shown dotted) and thereby disconnects the track rails from the relay TR. In the arrangement here shown, a second contact I4 of the impulse relay at the same time 5 sets up a circuit over which the auxiliary battery AB is connected across the track rails when a second contact I5 of the track relay TR is released. The period of this release delay is coordinated with the periods of the signal control codes to which the track relay TR responds in a manner to be made evident presently.

Each time that the track relay TR picks up during an on period of the signal control code, contact I2 of that relay connects the winding of the impulse relay IR with a source of pick-up energy designated in Fig. l by the terminals plus and minus. At the beginning of each off period which follows, relay TR releases and deenergizes relay IR. Being slow releasing, relay '20 IR stays picked up until just before the beginning of the succeeding on code period. Contact I4 thereof now connects the auxiliary battery AB across track rails I and 2 over a circuit which includes back contact I5 of relay TR. In this manner, each release of the track relay TR causes the impulse relay IR momentarily to transfer the track rail connections. from the winding of relay TR to the output circuit of battery AB. 7

In the form shown at location E in Fig. 1, the cooperating exit end facilities comprise a detector relay KR which responds to pulses of auxiliary energy received over the rails I and 2 from battery AB, a circuit controlled by a contact I! of that relay for energizing the approach relay AR from a local source designated by the terminals plus and minus, and means for making the relay AR sufficiently slow'releasing to bridge the intervals between recurrent responses of the de- 4 tector relay. 7

This detector relay KR is of the code following type and the operating winding thereof is connected in energy receiving relation with the track rails I and 2 only during the off periods of the. signal control code which contact 5 of the continuously operating device CR produces. The here represented arrangement of devices CR, KR and AR is similar to that disclosed and claimed in a copending application Serial No. 221,317 5 filed July 26, 1938, by Edward U. Thomas; in the present arrangement the just named connection is completed when the coding contact 5 occupies its lowermost or off period position.

current, use may, of course, be made of any suitable means, such as a snubbing impedance 5 (not shown) or internal design expedients incorporated in the relay. Because of their wellknown character, the drawing makes no attempt to represent any such means.

In operation of the complete approach control system which is represented in Fig. 1, the track rails I and 2 of section DE act in the usual manner to transmit energy from one end of the section to the other as long as the section re- -mains unoccupied. Each time, under such conditions, that contact 5 of the coding device CR is in the uppermost or on code period position, the track battery TB picks .up the track relay TR over a circuit which may be traced from the positive terminal of the battery through a current limiting impedance I9, front contact 5 of device CR, conductor 20, the track rail I, conductor 2I, the winding of relay TR at the section entrance, conductors 22 and 23, back contact I3 of relay IR, conductor 24, track rail 2, conductor 25, the secondary winding of transformer TT and a second impedance 26 back to the negative terminal of battery TB.

In responding to this pick-up energy, contact I2 of relay TR picks up the impulse relay IR over a circuit which may be traced from the positive supply terminal through front contact I2 of relay TR, conductor 28 and the winding of relay IR back to the negative supply terminal. In now picking up, contact I I of relay IR sets up the circuit over which battery AB supplies the track rails I and 2 with auxiliary energy. This circuit, however, remains interrupted until contact I5 of relay TR releases at the end of the on code period.

In picking up along with contact I4, contact I3 of relay IR interrupts the original connection of the track relay TR with the track rails. However, before contact I3 picks up, contact I5 of relay TR has established a parallel or stick connection over which the code energy from batte'ry TB at the section exit continues to flow through the track relay winding until the end of the on period. As shown in Fig. 1, this parallel or stick path includes a circuit which may be traced from track rail I through conductor 2 I, the winding of relay TR, conductors 22 and 23, front contact I5 of relay TR and conductors 29 and 24 back to track rail 2.

Each time that the coding contact 5 of device CR occupies the lowermost or off code period position in which the Winding of the detector relay KR is bridged across the track rails, the track relay TR at the entrance end of the section releases. Contact I5 thereof now breaks the just traced stick path and thereby disconnects the track rails I and 2 from the Winding of relay TR.

At the same time, this contact causes the auxiliary battery AB to be connected with the rails over front contact I4 of relay IR. Once established, this connection is maintained until one or the other of the contacts I4 and I5 shifts its position.

In the case of contact I5, of relay TR, this shift occurs at the beginning of the succeeding on code period while in the case of contact I4 of relay IR, this shift or release occurs at the expiration of the release delay period of relay IR. In practice this period will preferably be chosen to be just slightly less than the length of the off periods of the fastest code which the signaling system uses. In the case of the three indication system previously mentioned as employing codes of '75 and 180 energy pulses per minute, the shortest off period is determined by the 180 code, the cycle length of which is 0.33 second and the off period length of which is about 0.16 second.

Because of the just explained joint action of relays TR and IR which takes place during each off period of the received signal control code, the auxiliary battery AB becomes effective during each of these off periods to pick up the detector relay KR at the exit end of the section over a circuit which may be traced from the positive terminal of battery AB through front contact I4 of relay IR, conductor 3I, back contact I5 of relay TR, conductors 29 and 24, track rail 2, conductor 25, the winding of relay KR, conductor 32, back contact 5 of coding device CR, conductor 23, track rail I, conductors U and 33, a current limiting impedance 34 and conductor 35 back to the negative terminal of the auxiliary battery.

Under the influence of each of these auxiliary pulses of energy which is received from the trackway, the code following detector relay KR picks up and contact I! thereof completes for the approach relay AR a local energizing circuit which may be traced from the positive supply terminal through front contact I'I, conductor 31 and the winding of relay AR back to the negative supply terminal.

As a result of these recurring pulses of local energization, the slow release approach relay AR now holds its contacts 9 and I I continuously picked upand thereby maintains the wayside signal Se and the track transformer TT at location E deenergized as long as the track section DE remains vacant.

In the event that a train comes into the section DE the usual shunting action of its wheels and axles reduces to a very low value the potential difference between the rails I and 2 and thus deprives both of the relays TR and KR of pick-up energy. Relay KR now remains continuously released and the supply of local energization to the approach relay AR is discontinued. In consequence, that relay now completes at contacts 9 and II energizing circuits for the signal Se and the track transformer TT.

As a result, the named wayside signal now lights the particular lamp selected by the decoding equipment In and the transformer TT supplies the rails of the section DE with a pulse of alternating current energy from source BC each time that the contact 5 of device CR occupies its uppermost position. As has been mentioned, this energy is suitable for the control of train carried cab signals and the circuit over which it is supplied may be traced from the lower terminal of the secondary winding of transformer TT through impedance 26, the track battery TB, impedance I9, front contact 5 of device CR, conductor 20, rail I, the Wheels and axles (not shown) of the train,

rail 2 and conductor 25 back to the upper terminal of the track transformer secondary.

In the particular arrangement of Fig. 1, contact II of the approach relay AR so controls the supply circuit for transformer T1 that when the relay is released the primary of the transformer is connected with the terminals B and C over back contact II, conductor I and conductor 38. When, however, the contact II is picked up, the connection just named is broken and the two terminals of the primary winding of the transformer are by-passed over a circuit which extends from the lower terminal of the winding through conductor 38, front contact II of relay AR and conductor 1 back to the upper terminal of the winding. The purpose of this by-pass is to reduce the impedance which the secondary winding of the transformer presents to the flow of direct current from battery TB to the track rails under conditions of track section vacancy.

As soon as the rear of the departing train clears the exit of section DE, the coded energy from track battery TB is again transmitted by the rails to the track relay TR at the section entrance. That relay once more responds and acts in conjunction with the impulse relay IR to connect the track rails in energy receiving relation with the auxiliary battery AB during each of the off code periods.

These auxiliary energy pulses are, in turn, transmitted by the rails to the detector relay KR at the exit location E. In responding to them that relay again causes the approach relay AR to receive recurrent pulses of local energizing current. The approach relay once more picks up and due to its slow release characteristics continuously deenergizes the wayside signal Se and the track transformer TT at location E, thereby restoring both of these devices to their normally inactive state.

Further regarding my improved entrance end facilities which are shown at location E, it has already been pointed out that the period of release delay for the impulse relay IR is so chosen that the connection of the auxiliary battery AB with the track rails is maintained for substantially the full duration of the shortest off period for all of the various codes to which the signaling system track relay TR is called upon to respond. From a further inspection of the circuits of Fig. 1, it will be seen that the auxiliary energy supply circuit is set up by contact l4 during each on period of the trackway code and is completed by contact the instant that the track relay TR releases at the beginning of the off period. This assures that the rails are supplied with the auxiliary or approach control energy from battery AB at the earliest possible time in each of the off periods.

The improved arrangement of Fig. 1 further insures that the auxiliary supply connection will be maintained for as large a portion of each off code period as is possible. Relay IR has its slowness of release so adjusted that it will drop out contact M only just before the before-mentioned shortest off period has expired. This adjustment is capable of relatively accurate setting and it thus cooperates to insure that the maximum practical time of connection of the auxiliary battery with the rails will be realized.

Once selected to meet the limiting conditions of the highest speed code of the signaling system, the relay IR provides the same fixed period of rail connection transfer for all other signaling system codes. That is, even with the lower speed or '75 pulse per minute code previously referred to, the period of rail connection transfer will still be the same as for the 180 pulse per minute or high speed code even though the total length of the 75 code off period is of the order of 0.40 second as compared with about 0.16 second for the 180 code.

In all cases my entrance end facilities which are herein disclosed afford an improved means for introducing the pulses of auxiliary energy into the track circuit without interfering with the normal code following operation of the signaling system track relay TR. From a standpoint of energy conservation, these facilities are of special advantage since they maintain the auxiliary energy supply circuit completely disconnected from the track rails during the on code periods and thereby enable the track relay to receive the full value of trackway energy which is available at its point of connection with the rails. Moreover, during each of the ofi code periods my improved facilities maintain the track relay completely disconnected from the rails and thus allow all of the auxiliary energy from battery AB to be im' pressed upon these rails for the purpose of transmission forwardly to the operating winding of the code following detector relay KR at the section exit. 'In this manner, maximum utilization of the different forms of energy for the particular purposes intended is at all times assured.

The just discussed feature of maintaining the auxiliary battery AB connected with the track rails for substantially the full length of the oil? periods of the received signal control code is of advantage not only when cooperating exit end. apparatus of the type shown at location E is employed but also with exit end apparatus either of simpler or of more complicated corresponding form. The simpler form referred to may be that in which the code following detector relay KR is dispensed with and the winding of the slow release approach relay AR is connected directly between conductors 25 and 32 for the purpose of being energized directly by the potential from auxiliary battery AB which is transmitted over the track rails l and 2 and the back point of coding contact 5. The more complicated variety of apparatus referred to may be that in which the code following detector relay KR is provided with a second or supplementary stick winding which cooperates with the rail energized pick-up winding in maintaining the relay picked up for the full duration of each of the oif code periods within which pick-up takes place.

In any one of these forms the exit end apparatus requires that the approach relay AR be provided with slow releasing characteristics which are sufficiently extended to allow the approach relay to bridge the intervals between successive pulses of winding energizing current. The shorter the pulses of auxiliary from battery AB are, the longer will the just named intervals be. As the length of the auxiliary energy pulses are eX- tended under given code conditions, the lower will the named intervals be and hence the smaller may the period of release delay of the approach relay AR be made. Such a delay reduction is of practical significance in that it quickens the response of the slow release relay to the entry of a train into the associated track section (D-E in Fig. 1). Hence, the practical utility of my improved entrance end apparatus which has just been described and which is represented at location D in Fig. 1.

Referring to Fig. 2, I have there shownentrance end facilities modified to simplify the wiring and other features of the basic form of apparatus which is represented at location D in Fig. 1. In this modification of Fig. 2, the auxiliary battery AB is employed not only to supply the rails l and 2 with the off period pulses of energy for controlling the approach relay AR (not shown in Fig. 2) at the section exit (see location E of Fig. 1) but also to supply the pickup energy to the impulse relay IR. This impulse relay, moreover, requires only a single contact I3 and may dispense with the second contact which is shown at M in Fig. 1.

In considering the operation of the apparatus of Fig. 2, it will be helpful to assume that the track rails I and 2 extend forwardly from the entrance end location D to a cooperating exit end apparatus of the character which is represented at location E in Fig. 1. This means that the track relay TR is responsive to coded signal control energy in the same manner as in the system of Fig. 1 and that it accordingly picks up contacts l2 and I5 upon the occasion and for the duration of each on period of the received signal control code. These two contacts are arranged somewhat differently in Fig. 2 than in Fig. 1 but in other respects the track relays TR of the two figures may be identical.

Each pulse of signal control energy which is received from the track rails I and 2 of Fig. 2 picks up the track relay TR over a circuit which extends from rail I through conductor 2!, the Winding of relay TR, conductor 22, back contact I3 of relay IR and conductors 29 and 24 back to rail 2. In this manner, each of the on code periods causes contact l of relay TR to pick up the impulse relay IR over a circuit which may be traced from the positive terminal of battery AB through conductor 40, the front contact l5, conductor 28, the winding of relay IR and conductor 33 back to the negative terminal of the auxiliary battery.

Relay IR is thus caused to respond to each of the on code periods in the same manner as when controlled over front contact I2 of relay TR as shown in Fig. 1. In so responding, this relay IR picks up contact I3 and thus interrupts the pick-up circuit for the track relay TR and sets up a circuit over which the auxiliary battery AB is connected with the track rails at the beginning of the succeeding off code period.

The action just named is preceded by a completion at contact [2 of relay TR of a parallel energizing or stick circuit for the track relay. During the remainder of the on code periods the winding of relay TR receives trackway energy over this stick path which, in the particular form shown in Fig. 2, may be traced from the track rail I through conductor 2|, the winding of relay TR, conductor 22, front contact l2 of relay TR and conductor 24 back to track rail 2. In this manner, the action of contact I3 of the impulse relay IR is prevented from interfering with the normal code following operation of the track relay TR.

At the beginning of each off period of the received signal control code, relay TR releases in the usual manner and contact I5 thereof completes the before referred to auxiliary energy supply circuit. Over this circuit the battery AB now supplies the track rails I and 2 with auxiliary energy by way of a path which extends from the positive terminal of the battery through conductor 40, back contact I 5 of relay TR, impedance 34,

' control code while the latter action marks the expiration of the release delay period of the impulse relay IR. As in the case of Fig. 1, this period is preferably so chosen that contact I3 releases shortly before contact I5 of relay TR picks up when the fastest of the signal control codes is being received at the section entrance.

Acocrdingly, just before the beginning of the referred to on period, contact i3 of relay IR. releases to disconnect the auxiliary battery AB from the track rails and to reconnect the rails with the winding of relay TR over the back point of contact I3 and conductor 22. This assures that the relay TR will respond in normal manner to the code pulse of signal control energy which it next receives.

It will thus be seen that insofar as the coded signaling system and the associated approach control without line wire scheme are concerned, the modified facilities of Fig. 2 are the full equivalent of the basic form of apparatus which is shown at location D in Fig. 1. As has been pointed out, the Fig. 2 equipment has the added advantage of greater simplification which is evidenced by the elimination of contact I4 (Fig. 1) from relay IR of Fig. 2 and also the elimination of a separate source of pick-up energy (terminals plus and minus of Fig. 1) from the equipment of Fig. 2. Not only is the wiring of the appartus simplified but the double use of the auxiliary battery AB is of especial advantage particularly at out sections (not shown) in that the additional load which the impulse relay imposes upon this battery tends to equalize the drain on the battery to a point where it approaches the normal drain on the track battery (not shown in Fig. 2 but see TB in Fig. 1) which supplies the rear track section of the signaling system.

Referring now to Fig. 3, I have there represented a third form of the basic entrance end facilities of Figs. 1 and 2 modified to protect the track relay TR against bell action in the event of accidental failure of the stick portion of its trackway energizing circuit. As in the case of Fig. 2, the facilities of Fig. 3 are the full equivalent of the entrance end apparatus which is shown at location D in Fig. 1. In considering Fig. 3, therefore, it will be helpful to assume that the rails I and 2 extend forwardly from the entrance end location D and terminate in cooperating exit end apparatus of the character which is shown at location E in Fig. 1.

As in the earlier views, the approach control facilities of Fig. 3 are represented in association with a coded track circuit system of automatic block signaling which provides three indication control of the wayside signals S and which will be assumed to employ track circuit codes of 75 and 180 energy pulses per minute. Unlike the earlier views, however, Fig. 3 represents in relatively complete manner one representative form which the signaling system decoding apparatus (indicated at ill in Figs. 1 and 2) may take.

This decoding apparatus of Fig. 3 includes a decoding transformer DT provided with a direct current primary exciting circuit which is pole changed in conventional manner by a contact 42 of the code following track relay TR. The secondary winding of this transformer is connected in energy supplying relation with a first decoding relay DR'I5 over a circuit which includes a second or current rectifying contact 43 of the track relay.

This first decoding relay DR'I5 is non-selective and is adapted to pick up when the track relay TR responds to operating energy of either the '75 or the 180 trackway code. It is a direct current device and is associated with the decoding transformer DT in a manner disclosed and claimed in copending application Serial No. 210,744 filed by Frank H. Nicholson et al. on May 28, 1938, and assigned to The Union Switch & Signal Company.

Also deriving energy from the decoding transformer DT through a circuit which includes a resonant unit DUI 80 is a second decoding relay DRIED. This second relay is rendered responsive only to transformer energizing voltages which have a frequency corresponding to that produced when the track relay TR receives operating energy of the 180 pulse per minute code. Because of the frequency selective characteristics of the unit DUI8U, codes of the '75 pulse per minute and other low rates are ineffective for picking up the relay.

Through the medium of contacts 45 and 46 the two decoding relays DRT5 and DRIBO control the lighting circuits for the three lamps G, Y and R of the associated wayside signal Sd. When relay TR responds to energy of the 180 code received from the track section ahead of location D, both f the relays DR15 and DRIBB are picked up to set up the lighting circuit for the "clear lamp G. When this relay responds to energy of the pulse per minute code, relay DR15 only is picked up and the lighting circuit for the approach lamp Y is then set up. Finally, when relay TR is continuously deenergized, as when a train is in the track section ahead of location D, both of the decoding relays DR'I5, and DRIBU are released and the circuit for the stop lamp R then is set up.

Considering now the approach control facilities of Fig. 3, these make use of an impulse relay IR which is provided with slow releasing characteristics of thesame order as are used in the corresponding equipments of Figs. 1 and 2. These may, of course, be imparted to the relay in any suitable manner, as by the use of a winding snubbing rectifier 41 bridged between conductors 33 and 28 of the relay energizing circuit in the manner shown. Completion of the particular snubbing circuit which is represented is dependent upon a contact 48 of decoding relay DRl5 occupying the picked up position and thereby connecting conductor 28 with the right terminal of the winding of relay IR over conductor 49.

Not only does the Fig. 3 pick-up circuit for the track relay TR include back contact [3 of the impulse relay IR as in Figs. 1 and 2, but it also includes a contact 5| of the decoding relay DR15. As in the case of Fig. 2, the stick circuit for this track relay is completed over a front contact !2 of that relay. In Fig. 3, moreover, the circuit over which the battery AB supplies the track rails with auxiliary energy during the off periods of the received signal control code is similar to the corresponding circuit of Fig. 2 in that it includes a back contact l5 of the track relay TR and a front contact l3 of the impulse relay IR. The pick-up circuit for the impulse relay IR, however, differs from that of the preceding figures in that it includes the before referred to contact 48 of the decoding relay D R'lS.

In considering the operation of the entrance end facilities of Fig. 3, assume first that with vacant conditions of the protected track l-2 cooperating exit end facilities (not shown in Fig. 3 but see location D of Fig. 1) are supplying the rails of the section ahead of location D with energy of the pulse per minute code. Under this condition, both of the decoding relays DR'l5 and DRIBB are picked up and the lighting circuit for lamp G of signal Sd is set up over contacts 45 and 46 thereof.

Each pulse of thecoded energy (from battery TB, see Fig. 1) picks up the track relay TR over a circuit which extends from the track rail 1 through conductor 2i, the winding of relay TR, conductor 22, back contact l2 of relay TR, conductor 53, front contact 5| of relay DR'lE, conductor 54, back contact l3 of relay IR and con ductors 29 and 24 back to track rail 2.

In responding to each of these on code periods relay TR causes the impulse relay IR to receive energization over a circuit which may be traced from the positive terminal of the auxiliary battery AB through front contact [5 of relay TR, conductor 28, front contact 48 of relay DR'I5, conductor 49, the winding of relay IR, conductor 33 and impedance 34 back to the negative terminal of battery AB. Relay IR accordingly also picks up at the beginning of each of the named on periods. In so doing, contact 13 thereof sets up a circuit over which the battery AB later supplies auxiliary energy to the track rails l and 2.

This circuit is completed at contact I5 when the track relay TR releases at the beginning of the succeeding off code period and may be traced from the positive terminal of battery AB through back contact l5 of relay TR, conductor 55, front contact 33 of relay IR, conductors 29 and 24, the track rails 2 and I, conductors 2i and 33 and impedance 34 back to the negative terminal of battery AB. The circuit just traced remains completed until the release delay period of the impulse relay IR expires, at which time contact l3 interrupts this circuit and thus disconnects the battery AB from the rails. I

In this manner the facilities of Fig. 3 function to transfer the track circuit connection from the winding of the track relay TR to the auxiliary battery AB during each off period of the received signal control code. Such connection transfers, of course, cause the rails I and 2 to transmit auxiliary energy forwardly to the exit end of the section where apparatus of the char- As in the case of each of the earlier described figures, the apparatus of Fig. 3 includes provision for establishing a stick path for the track relay TR upon each pick-up operation thereof, which path serves to maintain the relay connectedacross the rails l and 2 for the full duration of the on code period. In Fig. 3, this provision includes the front point of contact l2 of relay TR and conductor 29 and a stick circuit which includes these elements. It is by way of this circuit that the track rails continue to supply energy to the winding of relay TR from each pick up of contact I3 of the impulse relay IR until the end of the on code period within which that pick up occurs.

This stick circuit of Fig. 3 may be traced from track rail 5 through conductor 2 I, the winding of relay TR, conductor 22, front contact H of relay TR and conductors 29 and 24 back to track rail 2. From a comparison of the diagrams it will be seen that this circuit is the general equivalent of that shown in l as including conductor 22, front contact !5 and conductor 29, and also of that shown in Fig. 2 as including conductor 22, front contact l2 and conductor 2d.

The entrance end facilities of Fig. 3 differ from the corresponding facilities of Figs. 2 and 3 in that they safeguard the code following track relay TR from bell action in the event of accidental failure of certain portions of the stick circuit for that relay. In each of Figs. 1 and 2, should this stick circuit fail at a time when the track rails I and 2 are supplying energy to relay TR, that relay will be caused to pick up and release at a rate which is determined by the release periods of the impulse relay IR. This form of operation will be referred to by the previously mentioned term of bell action.

In explaining this bell action, assume that the rails l and 2 are transmitting uncoded or steady energy and further assume that in Fig. l the portion of the stick circuit for relay TR of which front contact l forms a part becomes broken or otherwise incapable of completion. The bell action cycle begins when relay TR is picked up in the usual manner over back contact I3 of relay IR. Contact E2 of relay TR picks up relay IR in the usual manner and it opens the energizing circuit for relay TRat contact l3. Relay TR now releases and remains released until the end of the delay period for relay IR at which time contact l3 again releases and reconnects the winding of relay TR with the track rails.

This causes the cycle just described to be repeated and thereby produces a pumping action in relay TR at intervals which are determined by the release time of relay IR. As previously mentioned, this release time is chosen to be slightly less than the off period length of the 180 signal control code and for purposes of explanation it may be assumed to have the value of one-tenth second. Accordingly, as long as the rails transmit steady energy and as long as the stick circuit for relay TR is out of commission that relay will recurrently pick up and release at a rate which approximates ten times per second.

The same bell action is present in the apparatus of Fig. 2 in the event that the stick circuit of which front contact l2 of relay TR forms a part should go out of commission. In both instances, it occurs not only when the rails I and 2 are transmitting uncoded or steady energy but also during each pulse of the coded signal control energy which is supplied over contact 5 of device CR from the track battery TB at the section exit. Such bell action is, of course, objectionable in that, under conditions of steady track circuit energy particularly, it tends to produce false responses on the part of the controlled signal S when that signal is governed by the usual type of decoding apparatus represented at Iii in Figs. 1 and 2 and shown in Fig. 3 as including relays DRTE and DRi8fi.

The extended facilities of Fig. 3 are so arranged that this bell action will be prevented should the portion of the stick circuit for relay TR which includes conductors 29, 53 and 5'! go out of commission. In considering the character of this special protection, assume first that all of the relays TR, IR, DRIE and DRISO of Fig. 3 are in the deenergized position and that no energy is being transmitted by the rails l and 2 of the track section ahead of location D.

The first pulse or on period of any of the signal control codes picks up the track relay TR over conductor 2!, the relay winding, conductors 22 and 51, back contact M of relay DRIE, conductor 54, back contact l3 of relay IR and conductors 29 and 24. Since the DR'IE relay is released, contact 48 thereof prevents contact 15 of relay TR from completing the pick-up circuit for relay IR and as a result the track relay TR remains energized as long as voltage exists between the rails l and 2.

The first off period of the signal control code then releases relay TR in the usual manner. Due to the pole changing action of contacts 42 and 43 which accompanies this release, transformer DT supplies energy which picks up the decoding relay DR'I5. The next on period of the signal control code picks up the track relay TR over conductor 2|, the winding of the relay, conductor 22, back contact l2 of the relay, conductor 53, front contact 5! of relay DRIB, conductor 54, back contact l3 of relay IR and conductors 29 and 24.

This action picks up the impulse relay IR from battery AB over front contact [5 of relay TR,

conductor 28, front contact 48 of relay DR15, conductor 49, the winding of relay IR, conductor 33 and impedance 34' back to the battery. As long as voltage exists between the rails I and 2 the track relay TR remains stuck up over conductor 2|, the relay winding, conductor 22, front contact [2 of the relay and conductors 29 and 24.

Upon the next off period of the signal control code the track relay TR again releases and breaks the energizing circuit for relay IR at contact l5. Because of its delayed releasing characteristics, relay IR remains picked up until about one-tenth of a second later when it releases. During the time that the IR relay is energized and the TR relay is deenergized, the auxiliarybattery AB supplies the track rails l and 2 with this terminal voltage by way of a circuit which includes back contact 16 of relay TR, conductor 55, front contact I3 of relay IR, conductors 29 and 24, the rails 2 and I, conductors 2| and 33 and impedance 34. This is the impulse which controls the approach relay AR at the exit end of the track circuit.

Under certain conditions (not described herein because of their well-known character) of operation of the signaling system, the track rails I and 2 may transmit steady or uncoded energy from the exit to the entrance end thereof. In that event, track relay TR will remain energized over its front contact l2 and the decoding and impulse relays DRTE and IR will then remain deenergized, the circuit for the former being inactive due to the stationary position of the contact 42 of relay TR, and the circuit for the latter being broken at contact 48 of relay DR15.

If under these conditions of steady track circuit energy the conductor marked 29 in Fig. 3 breaks, the track relay TR will continue to receive energy over conductor 21, back contact 5i of relay DR'I5 and back contact l3 of relay IR. The controlled wayside signal Sd is not now falsely operated and hence continues to show nst pn If under conditions of steady track circuit en ergy the conductor marked 53 in Fig. 3 breaks, the just described continuously picked up c0ndition of relay TR will not be interfered with and bell action on the part of that relay will again be prevented. Similarly, if the conductor marked 5?! becomes broken, the track relay TR will release and so remain continuously regardless of the character of energy which the rails l and 2 transmit to the entrance end of the track section. This causes relays DRIE and IR to remain released and thus does not interfere with the stop display by the controlled wayside signal Sd.

Assume next that the rails l and 2 are transmitting energy of the '75 pulse per minute signal control code to the section entrance. In responding, relay TR causes decoding relay DRJ5 only to be picked up and thus puts the controlled wayside signal Set at approach. At the same time, the slow release relay IR is picked up by each on period of the 5 code and functions to transfer the track circuit connection from the winding of relay TR to the terminals of auxiliary battery AB during the early portion of each of the 01f code periods.

If the conductor marked 29 in Fig. 3 breaks, then bell action frequency of the track relay TR will be superimposed upon the on periods of the 75 signal control code. Because of their relatively high speed of recurrence (assumed to be about 10 times per second) these interruptions will be ineffective for picking up the second decoding relay DRlBll and therefore will not cause the controlled signal Sd to display a false indication less restrictive than the yellow or approach aspect. The effect upon the tuned unit DUi8Q, moreover, will be an intermittent one, that is, the bell action by relay TR takes place only during the on periods of the 75 code and for this further reason relay DRI ordinarily will not be picked up thereby.

Under the stated conditions of '75 code reception and bell action by relay TR, the referred to decoding relay DRJ5 may or may not release.

Due to the energy transferring characteristics of transformer DT relay DR'IS ordinarily will remain picked up and in that case the yellow indication by the controlled signal will be displayed in the same manner as were conductor 29 to remain intact. If, however, the relay DR15 does release, then the signal indication will be changed to stop which, of course, is in the direction of increased safety.

In the event that the track rails I and 2 are transmitting energy of the pulse per minute signal control code to the section entrance, both of the decoding relays DR'I5 and DRIBO of Fig. 3 normally respond to cause the controlled signal Sd to show the green or clear indication. If under these conditions the conductor marked 29 becomes disrupted, the relay TR will again operate its contacts at bell action frequency during each of the on periods of this code. Since the signal S is already at the clear or least restrictive indication any abnormal effect that this bell action may have on the two decoding relays can only cause the signal to show a more restrictive or safer indication so that here again the conductor marked 29 may be broken with no unsafe results.

Regarding conductors 53 and 51, the breakage of either of these under conditions of signal control code reception by the track relay TR has the effect of disconnecting conductor M of the track relay pick-up circuit from conductor 22 and once more the result will be to prevent the relay TR from picking up at all. Under such a condition, of course, the controlled wayside signal S is caused to display the maximum safety indication of stop.

In the very unusual situation in which the track rails l and 2 are transmitting energy of the 75 signal control code and this energy is changed to uncoded or steady energy there is a further possibility of bell action. This possibility will be completed only if the conductor marked 29 should break before the decoding relay DRIS has released. In that event, the track relay TR will operate at the bell action frequency, picking up over its own contact l2 and then releasing along with the impulse relay IR in the manner already explained. In such situations the apparatus of Fig. 3 will produce a flashing signal from stop to approach. This flashing action may be considered a safe failure and therefore is not objectionable from the standpoint of operation of the apparatus of Fig. 3.

From the foregoing it will be seen that I have made important improvements in that scheme of approach control without line wires wherein the rails of each unoccupied signal block length of track transmit code step pulses of auxiliary energy forwardly from the block entrance to effect the energization of a slow release approach relay at the block exit.

In particular, I have provided improved means for supplying the referred to pulses of auxiliary energy to the entrance end of each track circuit in a simplified manner which does not interfere with the normal code following operation of the signaling system track relay at that location and which eliminates power wastage; I have increased the accuracy with which the length of the auxiliary energy pulses may be adjusted or controlled; and I have incorporated various safety and self-protecting features into the pulse supplying apparatus.

As all of these improvements are entirely a function of the track circuit and apparatus which is directly associated therewith they are independent of the coding and decoding facilities of the coded signaling system and hence are usable with a wide variety of different types and form of such facilities.

While I have explained my invention in an application wherein both the lamps of the wayside signal and the supply of alternating current cab signal energy are approach controlled, it will be understood that either one of these functions may be performed separately and that other comparable functions may also be provided for in my new system.

Although I have herein shown and described only a few forms of approach control 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 a section of track, exit end means for supplying the rails of said section with coded signal control energy consisting of alternate on and off periods, a code following track relay connected with said rails at the section entrance and operated by the said coded signal control energy which is received from those rails, a source of auxiliary energy also at the section entrance, a similarly located slow release impulse relay controlled by and picked up over' a front contact of said track relay, means jointly governed by said track and impulse relays for transferring said track rail connection from the operating winding of the track relay to said auxiliary energy source at the beginning of each off period of the said received signal control code and for returning that connection to the track relay Winding before the beginning of the next on period of that code whereby to supply said rails with a pulse of auxiliary energy during each of those off code periods, a slow release approach relay at the section exit, similarly located means for receiving said auxiliary energy pulses from said rails and for energizing said approach relay in step with those received pulses whereby to maintain that relay continuously picked up under vacant conditions of said section and to allow that relay to release only when said section becomes occupied, and traffic governing apparatus controlled by said approach relay.

2. In a railway signaling system, the combination of a section of track, exit end means for supplying the rails of said section with coded signal control energy consisting of alternate on and off periods, a code following track relay connected with said rails at the section entrance and operated by the said coded signal control energy which is received from those rails, a source of auxiliary energy also at the section entrance, a similarly located impulse relay having a period of release delay which is less than the length of each of said off code periods and being effective when picked up to disconnect the rails of said section from the operating winding of the track relay and to set up a circuit over which those rails may be connected with said auxiliary energy source, means governed by said track relay for supplying said impulse relay with pickup current during each on period of said received signal control code, means also governed by said track relay for by-passing each of said relay winding disconnections from before the beginning of that disconnection until the end of the said on code period within which the disconnection occurs and for completing said previously set up rail to auxiliary source circuit from the beginning of each following off code period until the time during that period at which said impulse relay releases whereby to supply said rails with a pulse of auxiliary energy during each of those off periods,a slow release approach relay installed at the exit end of the section, similarly located means for receiving said pulses of auxiliary energy from said rails and for energizing said approach relay in step with those pulses whereby to maintain the approach relay continuously picked up under vacant conditions of said section and to allow that relay to release only when said section becomes occupied, and traffic governing apparatus controlled by said approach relay.

3. In combination with a section of track, means for supplying the rails of said section with coded signal control energy consisting of alterhate on and off periods, a code following track relay connected with said rails and operated by the said coded signal control energy which is received therefrom, a slow release impulse relay, means controlled by said track relay for energizing said impulse relay during each on period of said received signal control code whereby the impulse relay is caused to be picked up at the beginning and during a substantial portion of the 01f code period which follows, a

source of auxiliary energy, means responsive to each picked-up condition of said impulse relay for breaking the said connection of the section rails with the operating winding of the track relay and for setting up a circuit over which said rails may be connected with said auxiliary energy source, means governed by said track relay for by-passing said break in the connection of its winding with said rails until the end of the on code period within which that break occurs and for then completing the said previously set up rail to auxiliary source circuit during the following off code period whereby to supply said rails with a pulseof auxiliary energy during the aforesaid substantial portion of that 01f period, a slow release approach relay, means for receiving said pulses of auxiliary energy from said rails and for energizing said approach relay in step with them whereby to maintain that relay continuously picked up under vacant conditions of said section and to allow it to release only when said section becomes occupied, and trafiic governing apparatus controlled by said approach relay.

4. In a railway signaling system, the combination of a section of track, means for supplying the rails of said section with coded signal control energy consisting of alternate on and off periods, a code following track relay connected with said rails and operated by the said coded signal control energy which is received therefrom, a source of auxiliary energy, an impulse relay supplied over a contact of said track relay with pick-up current during each on period of said received signal control code and having a period of release delay which is less than the on period length of that code, means responsive to each picked-up condition of said impulse relay for breaking said connection of the section rails with the operating winding of the track relay and for setting up a circuit over which said rails may be connected with said auxiliary energy source, means governed by said track relay for by-passing each of said breaks in the connection of its winding with said rails until the end of the said on code period within which that break occurs and for completing the said rail to auxiliary source circuit from the beginning of each following off code period until the time within that period that said impulse relay releases whereby to supply said rails with a pulse of auxiliary energy during each of those off periods, a slow release approach relay, means for receiving said pulses of auxiliary energy from said rails and for energizing said approach relay in step with them whereby to maintain that relay continuously picked up under vacant conditions of said section and to allow it to release only when said section becomes occupied, and traffic governing apparatus controlled by said approach relay.

5. Incombination: a section of railway track, means for supplying the rails of said section with coded signal control energy consisting of alterhate on and off periods, a code following track relay having an operating winding connected with said rails and being responsive to the said coded signal control energy which is received therefrom, a source of auxiliary energy, a slow release impulse relay picked up over a front contact of said track relay, means jointly governed by said track and impulse relays for transferring said track rail connection from the operating winding of the track relay to said auxiliary energy source at the beginning of each 01f period of the said received signal control code and for returning that connection to the track relay winding before the beginning of the next on period of that code whereby to supply said rails with a pulse of auxiliary energy during each of those off code periods, a slow release approach relay, means for receiving said pulses of auxiliary energy from said rails and for energizing said approach relay in step with them whereby to maintain that relay continuously picked up under vacant conditions of said section and to allow it to release only when said section becomes occupied, and trafflc governing apparatus controlled by said approach relay.

6. In combination with a section of railway track, a source of trackway energy at the exit end of the section, an approach governing relay also located at the section exit, a coding contact which repeatedly connects the rails of said section first to said trackway energy source and then to the winding of said approach governing relay and thereby produces a trackway code consisting of alternate on and oh periods the latter ol which coincide with said relay winding connections, a code following track relay located at the entrance end of the section and having an operating winding which is connected with said rails whereby to receive said coded trackway energy therefrom, a source of auxiliary energy also 10- cated at said section entrance, a slow release impulse relay supplied under the control of said track relay with pick-up current during each on period of the said received trackway code, means jointly governed by said track and impulse relays for transferring said track rail connection from the operating winding of the track relay'to said auxiliary energy source at the beginning of each off period of said receivedgoverning relay and rendered active when that relay becomes continuously deenergized due to the presence of a train in said section.

'7. In combination with a section of track, means for supplying the rails of said section with coded signal control energy consisting of alterhate on and off periods, a code following track relay connected with said rails and operated by thesaid coded signal control energy which is received therefrom, asource of auxiliary energy, an impulse relay supplied over a front contact of said track relay with pick-up current during each on period of the said received signal control code and having a period of release delay which is less than the 01f period length of that code, means responsive to each picky-up condition of said impulse relay for breaking said connection of the section rails With the operating winding of the track relay and for setting up a circuit over which said rails may be connected with said auxiliary energy source, means governed by said track relay for by-passing each of said breaks in the connection of the track relay winding with said rails until the end of the on code period within which that break occurs and for completing the said rail to auxiliary source circuit from the beginning of the following off code period until the time within that period that said impulse relay releases whereby to supply said rails with a pulse of auxiliary energy during each of those off periods, means for receiving said pulses of auxiliary energy from said rails, and traffic governing apparatus controlled by said pulse receiving means and rendered active when the transmission of auxiliary energy pulses to those means is out off by the rail shunting action of a train within said section.

8. In combination with a section of track, means for supplying the rails of said section with coded signal control energy consisting of alternate on and off periods, a code following track relay, a circuit connecting said rails with the operating winding of said track relay whereby to transmit said coded signal control energy to that winding as long as said section remains vacant, an impulse relay having a period of release delay which is less than the off period length of the signal control code, means including a front contact of said track relay for energizing said impulse relay during each on period of the received signal control code whereby to cause the impulse relay to be picked up from a time early in'each of those on periods until near the end of the following off code period, a back contact of said impulse relay serially included in said rail to track relay winding circuit for the purpose of interrupting that circuit whenever the impulse relay is picked up, a front contact of said track relay connected in by-passing relation with said back contact of the impulse relay for the purpose of bridging each of said circuit interruptionsfrom before the beginning thereof until the end of the on code period within which the interruption occurs, a source of auxiliary energy, a circuit over which said auxiliary source may transmit energy to said rails, a front contact of said impulse relay and a back contact of said track relay serially included in said rail toauxiliary source circuit for the purpose of completing that circuit from the beginning of each 0 period of said received signal control code until thetime in that period at which the impulse relay rcleases whereby to supply said rails with a pulse of auxiliary energy during each of those off code periods, means for receiving said pulses of auxiliary energy from said rails, and trarnc governing apparatus controlled by said pulse receiving means and rendered active when the I transmission of auxiliary energy pulses to those means is cut off by the rail shunting action of a train within said section. v r

9. In combination with a section of track, means for supplying the rails of said section with coded signal control energy consisting of alternate on and off periods, a code following track relay, a circuit connecting said rails with the operating winding of said track relay whereby to transmit said coded signal control energy to that winding as long as said section remains vacant, an impulse relay having a period of release delay which is less than the off period length of the signal control code, a source of auxiliary energy, a circuit completed over a front contact of said track relay for connecting the winding of said impulse relay with said source during each on period of the received signal control code whereby to cause the impulse relay to be picked up from a time early in each of those on periods until near the end of the following off code periods, a back contact of said impulse relay serially included insaid rail to track'relay winding circuit for the purpose of interrupting that circuit whenever the lin pulse relay is picked up, a front contact of said track relay connected in by-passing relation with said back contact of the impulse relay for the purpose" of bridging each of said circuit interruptionsfrom before the beginning thereof until the end of the on code period within which the interruptionoccurs, a circuit over which said auxiliary energy source may transmit energy to said rails, a front contact of said impulse relay and a back contact of said track relay serially,

included in said auxiliary source to rail circuit for the purpose of completing that circuit from the beginning of each off period of said received signal control code until the time in that period at which the impulse relay releases whereby to supply said rails with a pulse of auxiliary energy during each of those off code periods, means for receiving said pulses of auxiliary energy from said rails, and traffic governing apparatus controlled by said pulse receiving means and rendered active when the transmission of auxiliary energy pulses to those means is cut off by the rail shunting action of a train within said section.

- 10.Incombination with a section of track, means for supplying the railsoi said section with coded signal control energy consisting of alternate on and off periods, a code following track relay, a circuit over which the operating winding of said track relay receives said coded signal control energy fromsaid rails, a decoding relay controlled by said track relay and arranged to pick up when and only when the track relay is following the coding of said received energy, an impulse relay picked up over a contact of said track relay during each on period of the said received signal control code and having a period of release delay which is less than the off period length of the signal control code, a back contact of said impulse relay and a back contact of said decoding relay serially included in said rail to track relay winding circuit for the purpose of completing that circuit in advance of the beginning of each on period of said received signal control code and for interrupting that circuit from shortly after that on period beginning until the end of the following off code period, a front contact of said track relay connected in by-passin-g relation with the two back contacts just named to bridge each of said circuit interruptions until the end of the on code period within which the interruption occurs, a source of auxiliary energy, a circuit over which said auxiliary source may transmit energy to said rails, a back contact of said track relay and a front contact of said impulse relay serially included in said auxiliary source to rail circuit for the purpose of completing that circuit from the beginning of each off period of said received signal control code until the time in that period at which the impulse relay releases whereby to supply said rails with a pulse of auxiliary energy during each of those "off code periods, means for receiving said pulses of auxiliary energy from said rails, and traffic governing apparatus controlled by said pulse receiving means and rendered active when the transmission of auxiliary energy pulses to those means is cut off by the rail shunting action of a train within said section.

11. In combination with a section of track, means for supplying the rails of said section with coded signal control energy consisting of alternate on and off periods, a code following track relay, a circuit over which the operating winding of said track relay receives said coded signal control energy from said rails, a decoding relay controlled by said track relay and arranged to pick up when and only when the track relay is following the coding of said received energy, an impulse relay picked up over a contact of said track relay during each on period of the received signal control code and having a period of release delay which is less than the off period length of the signal control code, a back contact of said impulse relay and a back contact of said decoding relay serially included in said rail to track relay winding circuit for the purpose of maintaining that circuit completed at all times that said track relay fails to receive said coded energy, a back contact of said track relay and a front contact of said decoding relay serially connected to by-pass the just named back contact of the decoding relay whereby when said coded energy is being received to complete said rail to track relay winding circuit in advance of the beginning of each on period of the received code and to interrupt that circuit from shortly after that on period beginning until the end of the following "off code period, a front contact of said track relay connected in by-passing relation with that portion of the rail to track relay winding circuit which includes the four relay contacts above named whereby to bridge each of said circuit interruptions until the end of the on code period within which the interruption occurs, a source of auxiliary energy, a circuit over which said auxiliary source may transmit energy to said rails, a back contact of said track relay and a front contact of said impulse relay serially included in said auxiliary source to rail circuit for the purpose of completing that circuit from the beginning of each off period of said received signal control code until the time in that period at which the impulse relay releases whereby to supply said rails with a pulse of auxiliary energy during each of those off code periods, means for receiving said pulses of auxiliary energy from said rails, and trafiic governing apparatus controlled by said pulse receiving means and rendered active when the transmission of auxiliary energy pulses to those means is cut off by the rail shunting action of a train within said section.

12. In combination with a section of track, means for supplying the rails of said section with coded signal control energy consisting of alternate on and off periods, a code following track relay, a circuit connecting the operating winding of said track relay in energy receiving relation with said rails, a decoding relay controlled by said track relay and arranged to pick up when and only when the track relay is receiving and following the coding of said signal control energy, an impulse relay picked up over a contact of said track relay during each on period of the received signal control code, an impedance bridged across the winding of said impulse relay over a front contact of said decoding relay whereby whenever said track relay is following said signal control code to impart to the impulse relay a period of release delay which is less than the "ofi period length of the signal control code, a back contact of said track relay and a back contact of said impulse relay serially included in said rail to track relay winding circuit for the purpose of completing that circuit in advance of the beginning of each on period of said received signal control code and for interrupting that circuit from shortly after that on period beginning until the end of the following ofi code period, a front contact of said track relay connected in by-passing relation with the two back contacts just named to bridge each of said circuit interruptions until the end of the on code period within which the interruption occurs, a source of auxiliary energy, a circuit over which said auxiliary source may transmit energy to said rails, a back contact of said track relay and a front contact of said impulse relay serially included in said auxiliary source to rail circuit for the purpose of completing that circuit from the beginning of each off period of said received signal control code until the time in that period at which the impulse relay releases whereby to supply said rails with a pulse of auxiliary energy during each of those oif code periods, means for receiving said pulses of auxiliary energy from said rails, and traffic governing apparatus controlled by said pulse receiving means and rendered active when the transmission of auxiliary energy pulses to those means is cut off by the rail shunting action of a train within said section.

HERMAN G. BLOSSER.

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