US2314241A - Railway signaling system - Google Patents

Description

lMarch 16, 1943. c. A. PICKELL.

RAILWAY SIGNALING SYSTEM 4 sheets-sheet 1 Filed Sept. 11, 1940 1m Field ca; sending and recewmg unII' INVEN OR 0i @6h/2M I ro m- ATTORNEY March 16, 1943. y c. A. PICKELL.

RAILWAY SIGNALING SYSTEM Filed Sept. l1, 1940 `4 Sheet-Sheet 2 INVENToR v BY l ATTORNEY Filed sept. 11, 1940 4 sheets-sheet 3 Fizld code 'sending and receiving uniT TOR Mm d ATTORNEY March 16, 1943. c. A. Plcmam.I

RAILWAY SIGNALI'NG SYSTEM Filed Sept. 11, 1940 4 Sheets--SheetI 4 RIU., En .H MN

INVENToR l, BY a @1 auf,

@ ATTORNEY .mw .ai

Patented Mar. 16, 1943 Clark A. Pickell, Rochester, N. Y.,

General Railway Signal Company,

assignor `to Rochester,

Application september 11, 1940, serial No. 356,346

11 Claims.

This invention relates to a railwaysignaling system of the absolute-permissive-block type having or not having superimposed thereon a centralized trailc controlling system for governing the movement of track switches and for clearing the starting signals at the entrance to the single track sections in which, if superimposed control is added, said starting signals are normally held at stop, and relates more particularly to means for indicating in a central ofce the condition of occupancy of the entire single track section of such system in a simple and economical manner.

A single track section connecting two passing sidings in an A. P. B. system having two intermediate double signal locations ordinarily employs six track relays in such single track section, By reason of the distance that many of these track relays are located from a coding unit in a code type system it would be prohibitive, by reason of the line wires which would have to be added, to transmit to the central oiTlce the positions assumed by such track relays.

In accordance with the present invention it is proposed to provide circuits and relays at the two ends of a single track section, which circuits and relays in combination transmit through the medium of the code type system having a field coding unit at each end of said single track section, accurately the fact Whether the single track section is occupied or unoccupied. More specifically, it is proposed to use the home relay at one entrance end to a single track section in combination with an approach relay indicating the condition of energization of the neXt opposing home relay for controlling the control circuits which manifest Occupancy of the single track section.

Other objects, purposes and characteristic features oi the present invention will in part be described hereinafter and the several specific embodiments thereof are shown in Figs 1A, 1B and 1C, Fig. 2 and Fig. 3 of the drawings. Figs. 1A, 1B and 1C if laid side by side in that order conveniently show one system embodying the present invention and Figs. 2 and 3 show how the system of Fig. 1 may be modified to constitute a second and a third embodiment.

Referring to the drawings with Figs. 1A, 1B and 1C laid side by side in this order, these drawings show two passing sidings PSI and PS2 which are connected by a single track section including track circuited blocks X, Y and Z. Each of these blocks is provided with a centrally fed track circuit including a battery BX, BY or BZ and a track relay at each end of such block. These track relays have been designated by the reference character T having a prefix corresponding to the signal which such track relay directly controls. The passing siding PSI is connected to the single track section comprising block, X, Y and Z by a switch SWI, whereas ythe passing siding PS2 is connected to this single track section by a track switch SW2. Traflic is governed into the west end of the single track, section by the starting signals S2 and `SZA for trains leaving the main track and side track of the passing siding PSI, respectively. Similarly, traffic may be governed into the east end of the passing siding by starting signals S1 and SIA. The signals for governing east bound traino through and out of lthe single track section have been designated S4, S6 and S8, whereas the signals governing west bound trafc through and out of the single track section have been designated S5,QS3 and SI.

Although the present. invention may beapplied to any suitable type of A. P. B. systemy only a few specic forms of such a system havebeen H1115- trated and in order to get a better understanding of the rst specific system illustrated in Fig. 1

the circuits and apparatus located at each intermediate signal will be briefly described.' Since the apparatus at each of these intermediate signals is the same as that at any other intermediate signal location the description of the apparatus associated with intermediate signal S4 Will suffice.

Although this signal S4 may be of any vsuitable construction, such as a semaphore signal, a search-light signal of the movable spectacle type on a multi-unit light signal, for convenience va multi-unit light signal only has been illustrated.

This signal S4 is preferably provided with three light units, one light unit of which if lighted will ernit a green beam as designated Vby theletter G and signifying clear traffic conditions, another unit of which if lighted will emit ayellow beam as designated by the letter Y and signifying caution traffic conditions, and anotherof which units will emit a red beam and signifying danger trafc conditions, as designated `by the letter R. These lamps G, Y `and R are preferably controlled by a neutral contact |84 and a polar contact H4 of a home and distant relay 4HD. This home-distant relay llHD although it may be a slow releasing relay of any type ispreferably a relay of the polar retained-neutral type. This polar retained-neutral relay may be of a construction such as illustrated in the patent to Field, No. 2,180,583, dated November 2l, 1939.

As shown, relay `flHD is energized by a circuit including a front contact I24 of the relay 4T, a front contact I35 of the track relay 5T, a back contact I45 of the directional stick relay SRS and a front contact I56 of the home-distant relay BHD located at the next signal S6 in advance. This same circuit has another branch through the medium of which the relay 4HD may be energized by current of negative polarity, and this branch circuit includes the back contact I 56 of the home-distant relay 6HD and also includes a front contact Iii6 of the directional stick relay SRS.

These directional stick relays SR, are controlled in a well known and usual manner and by referring to signal S4 it will be seen that the relay SR4 may be picked up through a circuit including the back contact |84 of the track relay 4T and the front contact |94 of the home-distant relay 4HD in series. Upon picking up of this directional stick relay SRA it will be stuck up through a stick circuit including its own stick contact 201 and the back contact |81 of the track relay 4T. Dropping of the track relay 4T to pick up the stick relay SRA will also result in the dropping of relay 4HD by opening of its front contact |24. Since, however, the neutral armature of the home-distant relay 4HD is of the retained type the front contact |94 of this relay 4HD will not open until the stick relay SR4 has picked up. Upon eventual dropping of the relay 4HD a second stick circuit is closed for the stick relay SR4. This second stick circuit includes the stick contact 204 and the back contact 2|4 of the relay 4HD in series.

It is thus seen that the directional stick relay .SR4 can only be picked up when east-bound trac passes the signal S4, and that it will remain stuck up until this train has entirely left I the block Y as will be evidenced by the picking up of the relay 4HD. This picking up of the relay 4HD will break the second stick circuit for the relay SR4, the rst stick circuit having been broken when the track relay 4T picked up, allowing dropping of this stick relay SRA. The intermediate signals S3, S and S6 are controlled in a similar manner as just described for the signal S4 and for this reason like elements associated with the signals S3, S5 and S6 have been designated by like reference characters as those for signal S4, but having distinctive exponents, prefixes or subxes.

Since the starting signals associated with the entrance end of a single track section and since the exit signals for such single track sections, for

a particular direction of traffic, are dependent upon the positions of the track switches at the entrance end and at the exit end respectively, and since no direction relays are associated therewith, these signals are specifically controlled differently and the control circuits for these signals will now be briefly described.

Referring to Fig. 1A the track switch SWI may be controlled by a switch machine SM, which is controlled by circuits including a front contact 251 of a lock relay LI and interlocked contacts controlled by the normal relay INW and the reverse relay IRW in any Well known and usual manner, as conventionally illustrated by the dotted line 261. These switch control relays INW and IRW are preferably controlled through the medium of a code type system which has been conventionally shown by the oflice code sending and receiving unit O, the field code sending and receiving unit FI shown in Fig. 1A, and

the field code sending and receiving unit F2 75 shown in Fig. 1C. This code type communicating system may be of any suitable construction, such for instance, as disclosed in the patent to Preston and Bushnell, No. 2,155,561, dated April 25, 1939. The position of the track switch SWI is preferably indicated by a suitable switch indication relay WPI, which is preferably of the polar-neutral type and is preferably picked up to a particular polar position only when the track switch assumes a particular extreme position and providing the switch is locked in that position.

It will be seen that the starting signals S2 and S2A are normally held at stop. This is accomplished by the signal control relay RGZ shown in the eld code sending and receiving unit FI, which relay RGZ shown as a neutral relay, but

may be of any other suitable construction, is normally in its deenergized dropped away position. This signal control relay RGZ may also be a relay of the mag-stick polar type. This relay RGZ through the medium of its front contacts ISRl and ISR may energize either the signal relay 2G or the signal relay 2AG depending on the polar position assumed by the switch repeating relay WP at that time. These relays 2G and 2AG being further or additionally controlled by the back contact 301 of the lock relay LI, front contact 3 Il of the detector track relay DTI, front contact 322 of the relay 2HD and front contact 331 of the relay WPI. The relay 2G when energized and picked up will result in placing the signal S2 in either its caution or its clear condition depending on the polar position assumed by the contact 362 of the relay 2HD, this picking up of the relay 2G also extinguishing the red lamp R of the signal 2 by opening of the back contact 312 of the relay 2G. If the switch repeater relay WPI assumes its left-hand energized position signifying that the track switch SWI assumes the take-siding position the picking up of the relay RGZ will energize the relay 2AG which will result in the clearing of the dwarf starting signalSZA by lifting of its contact 402. This picking up of relay 2AG presumes the detector track relay DTI and the relay ZHD to be energized and the lock relay LI to be deenergized. This picking up of the signal relay 2AG will, however, also by the opening of its back contact 4I2 open the energizing circuit for the signal-at-stop relay MI', which in turn by opening of its front Contact 421 will open the energizing circuit for the home-distant relay 3HD. This circuit for relay 3HD in addition to the usual track relay contacts |23, |32 and II1 also includes the contact 231 of the relay IG. In a similar manner as the relay MI is deenergized by opening of the contact 4|2 of relay 2AG this relay MI may be deenergized by the opening of back contact 432 of the relay 2G. If desired the relay MI may be omitted, in which case the contacts 4I2 and 432 will be included in series in the circuit of the relay AEI.

The relays IG and IAG are controlled in a manner similar to that in which the relays 2G and 2AG are controlled, and since the switch SWI is locked so long as any signal governing traffic thereover is at proceed, suitable means must be provided to manually hold signals SI and SIA at stop. For convenience the manual control for these signals has been omitted. The relay IG to be energized requires the lock relay LI to be down and the relays DTI and IHD to be up and further is dependent on the position assumed by the polar contact 441 of the switch indication relay WPI. The relay IG has included in its energizing circuit the front contacts 461 `and 411 of relays DTI and IHD and the back contact 451 of the lock relay LI. Relay IAG is .controlled similarly to relay IGbut does not include the contact 411 of relay IHD. Signal SI iscontrolled by contacts 501 and-SI1 of relays IG and IHD in the same manner as signal S2 is .controlled by contacts 312k and 362 of relays 2G and ZHD. Also, the lamps of signal SIA are controlled by contact 521 of relay IAG in the same manner as the lamps of signal SZA are controlled by contact 402 of relay ZAG.

Let us now observe how the relays XRI and XRZ are controlled so as not to be deenergized due to dropping of the home-distant relay of the associated starting signal when that relay is dropped due toa tumble-down of signal relays started from the opposite end of the single track section but is deenergized if a train passes the associated starting signal and deenergizes itsassociated home-distant relay, 'I'his same construction also prevents the dropping of the relay XR! or XRZ due to the manual clearing of a starting signal at either the same end or the opposite end even though such clearing of a starting signal will cause a tumble down of homedistant relays to take place. The relay XRI is normally energized through a circuit including the front contact 552 and the polar contact 562 in its right-hand position of the home-distant relay ZHD and upon deenergization of the homedistant relay 2HD may be energized through the back contact 552 of this relay and the front contact 511 of the approach relay AEI. Since the entrance of a train into the west end of the single track stretch deenergizes both of these relays ZHD and AEI (unless relay AEI has been previously deenergized due to dropping of the relay MI) the relay XRI will be dropped due to such entrance of an east bound train in that end irrespective of Whether or not one of the starting signals S2 or S2A had been previously cleared.

Dropping of the relay XRI will through the medium of the code type communicating system above referred to cause the code responsive relay IXRI to operate its contacts 5I to the right, where they will remain by permanent magnet stick action. The dropping of the relay XRI will initiate the code communicating system by momentary opening of the starting circuit at its contact 531, and the closing of back contact 591 will generate the proper code element to operate the relay IXRI in the office to the right, which by closing contact 6I will energize indicating relay X. The picking up of relay X by closure of its front contact 63 will close an energizing circuit for the indicating lamp IX to manifest by its illumination that the single track section is occupied. If desired the relay X may be omitted, in which case the contacts BI and 52 in multiple (Fig. 1A) or in series (Fig. 3) will be included in the energizing circuit of the indicating lamp IX.

In a similar manner and through the medium of this communicating system the indicating relays IRI and IRZ are operated to the right to illuminate their respective indicating lamps Il and I2 through contacts 65 and 65 of these relays When the detector track relays DTI and DTB, respectively, are dropped, as by track occupancy. For instance, the dropping of the detector track relay DTI may initiate the communicating system by momentarily opening the starting circuit through the medium of its contact 681 after which the closed lcondition of contact 691 will transmit vthe proper code element to operate the indicating relay IRI to the right to illuminate the lamp II. ince theapparatus and signals associated with track switch SW2 are identical to vthose associated with the track switch SWI they have been assigned like reference characters having distinctive exponents, prefixes ,and suXes.

Operation of Fig. 1.Let us assume that .there is 1an .east-bound train occupying the main track of' the passing siding PSI which is about to pass through the single track stretch, and let us observe how the presence of this train in the single track stretch is indicated by the illumination of the indicating lamp IX so long as any part of this train occupies the single track section. In order Ato allow such train movement the starting signal S2 must first be manually cleared. The operator in the central oice O will operate .a suitable lever LGI which in turn will through the medium of the code communicating system heretofore referred to, cause energization of the east-bound signal control relay RGZ (R signifying right-hand direction). The energization of the relay RGZ closes its front contact IBR resulting in the energization of the signal relay 2G. Picking up of this relay 2G causes deenergization of the signal-atstop relay MI which in turn by the opening of its contact 421 causes deenergzation of the home-distant relay 3HD and also causes deenergization of the approach relay AEI. Dropping of the home-distant relay 3HD places the signal S3 in its stop position and by the opening of its front contact |53 causes deenergization of the h-ome-distant relay 5HD. Dropping of the relay 5HD places the signal S5 in the stop condition and by the opening of its Contact I55 causes deenergization of the home-distant relay 1HD, which in turn prevents either of the starting signals S1 or STA being cleared. Dropping of the approach relay AEI did not accomplish any particular function except to open its front contact 511 which becomes important only upon deenergization of the home-distant relay 2HD.

The picking up of the signal relay 2G by the opening of its back contact 312 opens the energizing circuit for the red lamp of the signal S2 and by the closing of its front contact 312 causes energization of the green lamp G of this signal S2. This is based on the assumption that the home-distant relay 2I-ID is energized to its right-hand positive position as would be the case when the single track section is unoccupied, rIVhe east-bound train in question may now, in response to the clearing of the signal S2, move into the single track section and when its rst axle enters the detector track section containing the detector track relay DTI this track relay Will be deenergized and by the opening of its Contact 3|1 will deenergize relay 2G- and place the signal S2 Ain its stop position, but this will not cause the illumination of the indicating lamp IX 'Ln the central o iiice O because the single track section is not yet occupied and will not be occupied until the train has passed over the switch SWI. this connection it may be pointed out that the switch SWI may also .be controlled from the central ollce O through the medium of a lever LWI and the code communicating system and through the medium of switch control relays INW and I RW which control the switch machine SM through the medium of circuits conventionally shown by the dotted line 261.

As the train proceeds into the single track section it will cause deenergization of the track relay 2T, which in turn by the opening of its contact |22 will cause deenergization of the home,-

InV

distant relay 2HD. The dropping of the relay 2HD by the opening of its front contact 552 Will break the energizing circuit for the relay XRI, the auxiliary circuit for this relay also being opened at the front contact 5T1 of the approach relay AEI. Dropping of the relay XRI and its contacts 581 and 591 causes a code to be transmitted to the central olice resulting in the operation of the indicating relay IXRI to the right. This will in turn cause energization of the indicating relay X and the illumination of the indicating lamp IX.

As the east-bound train proceeds through the single track section and passes the signal S4 it will cause deenergization of the home-distant relay 4HD and will cause energization of the directional stick relay SRA for reasons heretofore pointed out. This will cause reenergization of the home-distant relay ZI-ID, but at this time the relay ZHD will be energized by current of negative polarity and to the left so that even though the front contact 552 of this relay is closed the energizing circuit for the relay XRI remains open because the polar contact 562 is in its left-hand position. As this east-bound train passes the signal S6 it causes deenergization of the home-distant relays BHD and causes energization of the directional stick relay SRS. Since the energizing circuit for the home-distant relay SI-ID has included in series therein the approach relay AES this approach relay AE3 is also deenergized and dropped away. Since the home-distant relay THD was heretofore deenergized by reason of the tumble-down effect the indicating relay m2 at the east end of the single track section is now deenergized and this causes the code type communicating system to be initiated by the momentary opening of the contact 582 of this relay XRZ. Also, the closing of the back contact 592 of this relay XE2 transmits the proper code element` through the medium of the communicating system to operate the contact 62 of the relay IXR2 in the control chce to the right-hand position. This results in a second energizi-ng circuit for the indicating relay X being completed. As the train proceeds in an eastwardly direction and entirely passes out of the block Y the home-distant relay 4HD is again energized (with negative polarity in this instance) and by the closure of its front Contact I54 completes the normal energizing circuit for the relay 2HD which results in the return of the polar Contact 362 and 562 to its right-hand position resulting in the reenergization of the relay XRi. The picking up of the relay XRI transmits a code to the central office resulting in the operation of the indicating relay XRI to its left-hand position. Since, however, the indicating relay X is now energized by a circuit including the closed contact 62 of the relay IXR2, the indicating lamp IX remains lighted; manifesting that the single track section is still occupied.

As the train in question proceeds in an eastbound direction and passes the signal S8 it causes deenergization of the detector track relay DTB, which in turn, for reasons heretofore described, causes illumination of the indicating lamp I2 in the central office. As the last Wheels and axles of the east-bound train pass out oi the block Z,

and assuming that the operator has in the meantime returned his lever LGI to the stop position to deenergize the relay RGZ, the home-distant relay THD is reenergized (as are also home-distant relays IHD, SHD and 5HD) by current of positive polarity. This results in energization of relay IXR2 and the transmission of a code to the central oiiice resulting in the return of the indicating relay IXR2 to its left-hand position, which in turn causes the indicating lamp IX to be extinguished manifesting that the single track section is no longer occupied.

If the operator has, however, not returned his lever to the stop position the home-distant relay THD is not reenergized. In this case, however, the home-distant relay BHD and the approach relay AES included in series therewith are reenergized as soon as the train has cleared the detector track circuit to reclose the contact |18 of the detector track relay DTS. With the relay AE8 energized and the home-distant relay THD still deenergized the relay XR2 is reenergized through a circuit including back contact 527 of the relay THD and the front contact 5T8 of the relay AES. This will result in the deenergization of the indicating relay X in the control oiiice and in extinguishrnent of the indicating lamp IX. In a similar manner as just described the indicating lamp IX is also illuminated during the westbound passage of a train through the single track section.

There may be instances where it is not desirable to provide supervisory manual control over the starting signals but at the same time desire an indication of the condition of occupancy of the single track section. In this event, the signal control relays GZ and their contacts I8 and I9 would be omitted as would also ybe the contact 42 of the relay M, In this case the auxiliary circuit for the relays XR, and including a back contact 55 of the home-distant relay of the starting signal and a front contact 5T oi the approach relay AE, would be entirely omitted. Such an arrangement has been illustrated in Fig. 2 of the drawings. In this modied form of theV invention the tumble-down function is started when the train passes the starting signal and since this deenergizes the home-distant relay for the starting signal at the far end, this will by the opening of the front contact 55 of such home-distant relay resuit in the deenergization of the relay XR at the far end and in the illumination of the indicating lamp IX. The home-distant relay for the starting signal at the exit end of the single track section will, of course, remain in the deenergized condition until the train has entirely departed from the single track section at which time this home-distant relay is reenergized and the indicating lamp is extinguished.

In many instances there is only one pair of intermediate signals. Such an arrangement has been illustrated in Fig. 3 of the drawings. By referring to Figs. 1A, 1B and 1C it is readily seen that if only one pair of intermediate signals is employed, the home-distant relay for the starting `will not return to its normal positively energized condition until a train which entered that end has passed entirely out of the single track section. Also, the home-distant relay for the starting signal at the exit end is deenergized through tumbledown action when a train enters the entrance end and remains deenergized until the train has entirely departed from the single track section. In other Words, if the relays XRI and XE2 were conrolled as indicated for the relay XRI in Fig. 2, then the contacts 5I and 52 instead of being connected in multiple, as shown in Fig. 1A, could be connected in series, and if so connected the indicating relay X would be energized so long as there is a train in the single track section, irrespective of the direction of movement of the train through the single tracksection.. AsystemY so constructed has been illustrated inl Fig. 3` of the drawings. In this construction, althoughv the tumble-down function takes place when the train passes the star-ting signal and before it passes over the track switch, the indication of occupancy by the illumination of lamp IX' does not take place until the train'` has actually entered the single track section justfbeyond this track switch. This is true even though the home-distant relay for the starting signal at the exit end drops before the train has actually entered the single track section because the indication is not given by illumination of lamp IX until the home-distant relays for the starting signals at both ends of the single track section are in their non-clear (positively energized) condition. Also, this indicating lamp IX is extinguished the moment the last axle leaves thev single track section and when the train still occupies the detector track section at. the exit end.

The applicant has thus illustrated conventionally and described rather specically three embodiments of the present invention. It should, however, be understood that these illustrations are merely exemplary' of the nature of the invention and that various changes, additions and modications may be made to adapt the invention to thev particular problem encountered in practicing the invention without departing from thel spirit and nature of the invention, except as demanded by the scope of the following-claims.

What is claimed as new is:

l. In combination, a single track section divided into blocks and connecting two passing sidings, a starting signal at `each end of' said single` track section for governing` the movement of traiiic into said section from that end, an entering signal at each end of said single track section for governing the movement of traffic out of said single track section and into the connected passing siding, intermediate signals for governing traflic in each direction through said single track section, there being one such intermediate signal at the entrance tol each block', a home relay for each startingv signal and each intermediate signal, a track circuit for each block each including a normally energized track circuit, a circuit for each home relay including a front contact of the track relay of the block in advance and a front contact of the home relay for the signal next in advance, manually controlled means for each end of said single track section to normally hold said starting signal for'that end at stop and which if operated allowsclearingof such signal dependent upon the energized conditionV of its associated home relay and simultaneously therewith deenergizes the home relay for the lrst opposing-signal, whereby the clearing ofY a starting signal at one end of said singleY tracky section successively deenergizes the home relays for all opposingr signals, a central oflice, an'indicating lamp in said central'omce indicating by its condition of illumination the condition oi"` occupancy of said single track sec,-` tion, and means governed by the condition of energization of said home relays for said starting signals for causing the illumination of said indieating lamp when a train occupies said single track section, said means acting to preventthe illumination of said indicating lamp when one of saidhome relaysis deenergized due to the manual clearing of a starting signal.

2. In combination, a single track section dividedl into blocks and connecting two passing sidings, a starting signal at each end of said single track section forgoyerning themovement ofltraf fic. into said section from. thatl end, an enteringl signal at each end of said single track section for governing the. movement of traffic out of said single track section and into the connected passing siding, intermediate signals for governing traiiic in one direction and intermediate signals for governing traiiic in the other direction through said single track section, there being one such intermediate signal at the entrance to each block, a home relay for each starting signal and each intermediate signal, a track circuit for each block each including a normally energized track circuit, a circuit for each home relay including a frontk contact ofthe track relay of the` block in advance and a front contact of the home relay for the signal next in advance, whereby the entrance of a train into one end of said single track section successively deenergizes the home relays for all opposing signals, a central office, an indicating lamp in said central cnice indicating by its condition ofV illumination the condition of occupancy of said single track section, an approach relay at each end of said single track section' included in series withv the home relay for the rst opposing signal, and means governed by the home relay and the approach relay at a particular end of said single track section for governing said indicating lamp to illuminate such lamp when said single track section is occupied.

3. In combination, a section of single track connecting two passing sidings, signals at each end of said section governing train movements into and out of said section, intermediate signals in saidv section for governing the movement of traffic in both directions in said section, a signal relay'ior each signal except the last for each direction of tra-flic energized normally through a front contact of the signal relay of the signal next in advance, a directional stick relay for each signal except. the iirst for closing an energizing circuit, for the signal relay for the signal next in the rear if the block in advance is occupied by airain moving in a direction to be governed by such signals, an approach relay at each end of said section included in series with the signal relay'of the first opposing signal, a central oflice, an indicating lamp in said central oice indicating by its condition of illumination the condition of occupancy of said section, and means governed by the signal relay of the lirst signal and by its associated approach relay for each direction of traiiic for governing said indicating lamp to give an occupancy indication only when said single track section is occupied.

4.- In combination, a section of single track connecting two passing sidings, signals at each end of said section governing train movements into and out of said section', intermediate signals in4 said section for governing the movement of traffic in 4bothdirections in said section, a signal relay for each signal except the last for each'direction of trahie energized normally through a irontV contact of the signal relay of the signal next in advance, a directional stick relay for each signal except therst for closing an energizing circuit for the signal relay for the signal next in the rear if the block in advance is occupied by a train moving in a direction to be governed by such signals, an approach relay at each end of said section included ingseries with the signal relay of the rst opposing signal, a central ofce, an indicating lamp in said central office indicating by its condition of illumination the condition of occupancy of said section, and a relay for controllingk the energization of said indicating lamp energized by two circuits one of which inciudes a front contact of the signal relay of said first signal and the other of which includes a front contact of said approach relay.

5. In combination, a section of single track connecting two passing sidings, signals at each end of said section governing train movements into and out of said section, intermediate signals in said section for governing the movement of traine in both directions in said section, a polar relay for each signal except the last for each direction of traflic energized normally through a front contact of the polar relay of the signal next in advance, a front contact of a track relay of the next block in advance and by current of positive polarity, a directional stick relay for each signal except the rst for closing an energizing circuit for the polar relay for` the signal next in the rear energized by current of negative polarity if the block in advance is occupied by a train moving in a direction to be governed by such signals, an approach relay at each end of said section included in series with the polar relay of the first opposing signal, a central oflice, an indicating lamp in said central ofce indicating by its condition of illumination the condition of occupancy of said section, and a relay for controlling the energization of said indicating lamp energized by two circuits one of which includes a front ccntact of the polar relay of said rst signal and the other of which includes a front contact of said approach relay in series with a back contact of said polar relay for said rst signal.

6. In a single track railway system signaled by absolute-permissive-block signaling, the combination with a single track stretch connecting two passing sidings, signals including a starting signal for each end for governing the movement ofV traflic into that end and one or more intermediate signals for governing traflic in each direction through the stretch, a signal relay having polar and neutral contacts for each signal, a normally closed energizing circuit for each signal relay except the last including a front contact of the signal relay for the next signal in advance, a directional stick relay for each intermediate signal, a second energizing circuit for each signal relay except the last including a front contact of the directional stick relay for the signal next in advance, means for causing successive deenergization of said signal relays for one direction of traffic when a train moving in the opposite direc-y tion enters said stretch, and for energizing each directional stick relay as such train passes each intermediate signal, a track occupancy indicator for indicating occupancy of said stretch, an approach relay for each end of said section included in series with the signal relay for the first opposing signal, and means for controlling said indicator including one circuit through a front neutral contact and a polar contact of the signal relay for a starting signal and another circuit including a back contact of such signal relay and a front 'contact of its associated approach relay.

7. In a single track railway system having a stretch of single track between two passing sidings with starting signals for governing the movement of traiic'into said stretch in each direction together with intermediate signals in the stretch, an absolute-permissive-block signaling system with superimposed manual control having relays associated with said starting signals for governing the indication of such signals to permit one or the other to display clear in response to manual control and at the same time cause the opposite starting relay to remain at stop, said system also permitting either starting signal to display caution or clear for a following train with one or two blocks spacing respectively, a single track indicator for indicating when illuminated the occupied condition of said stretch of track, and means controlled by contacts of the relays associated with both said starting signals for illuminating said indicator whenever either starting signal displays caution or stop due to the presence of a train in said stretch, said means being ineffective when a starting signal indicates stop due to said manual control.

8. In a single track railway system having a stretch of single track connecting two passing sidings, a starting signal at each end of said stretch for governing the movement of traiiic into said stretch from that end, one or more intermediate signals for governing traino in each direction through the stretch, said signals acting to divide said stretch into a plurality of track sections, track relays for each of said track sections, a signal relay for each of said signals, an energizing circuit for each of said signal relays controlled by front contacts of the track relays for the track section next in advance of its associated signal and in accordance with trafc conditions in advance of that section, manually controlled means associated with each starting signal for holding that signal at stop but acting when operated to allow such starting signal to clear and at the same time to deenergize the circuits for the signal relays for each of the signals governing the opposite direction of traiiic, a single track indicator lamp in a central cnice for indicating when illuminated the occupied condition of said stretch, a communication system extending between the central office and said starting signals, indication circuit means associated with each starting signal for transmitting a track occupied indication to said central olice only when its signal relay is deenergized due to the presence of avtrain, said indication circuit means being ineffective to transmit such indication when its signal relay is deenergized in response to a manual control for allowing an opposing starting signal to clear, and circuit means in the central cnice responsive to the reception of a' track occupied indication over said communication system from either of said starting signals for energizing said single track indicator.

9. In a railway system having a stretch of 'single track connecting two passing sidings, a starting signal and one or more intermediate signals for governing traffic in each direction through said stretch, said signals acting to divide said stretch into a plurality of track sections, track relays for each of said sections, a polarized signal relay for each of said signals, an energizing circuit for each of said polarized signal relays controlled by front contacts of the track relays for the track section next in advance of its associated signal and in accordance with traic'conditions in advance of that section for normally energizing said signal relay with positive potential, a directional stick relay associated with each of the intermediate signals for applying negative potential to the energizing circuit for the polar signal relay for the signal next in the rear while the track section in advance of that intermediate signal is occupied by a train which passes it in a direction governed by such intermediate signal, manually controlled means associated with each starting signal for holding that signal at stop but acting when operated to allow such signal to clear and at the same time to deenergize the circuits of the signal relays for all signals governing traffic in the opposite direction, an approach relay associated with each of said starting signals and included in series with the polarized signal relay for the first intermediate signal governing trailic toward the corresponding siding, a track indication relay associated with each of said starting signals, circuit means for each of said indication relays for energizing that relay when said signal relay for the associated starting signal is energized with positive potential, said circuit means also energizing said indication relay if such signal relay is deenergized providing the associated approach relay is energized, whereby each indication relay is deenergized whenever a train is approaching v`the corresponding siding within the adjacent track section or is travelling away from the corresponding siding within the first two track sections of said stretch, a single track indicator in a central oiice for indicating when illuminated the occupied condition of said stretch as a whole, and circuit means efiective to illuminate said track indicator when either or both of said indication relays is deenergized.

10. In a single track railway system having a stretch of single track connecting two passing sidings, signals for governing traffic over said stretch of track in both directions including a starting signal at each end of the stretch and one or more intermediate signals dividing the stretch into track sections provided with track relays, a signal relay for each of said signals, an energizing circuit for each of said signal relays controlled by track relay contacts for the track section nent in advance of its associated signal and in accordance with traiiic conditions in advance of that section, manually controlled means associated with each starting signal for holding that signal at stop but acting when operated to allow such starting signal to clear dependent upon the cnergized condition of its associated signal relay and at the same time acting to deenergize the circuits for the signal relays for each of the signals governing the opposite direction of traiiic, a single track indicator lamp in a central oiiice for indicating when illuminated the occupied condition oi said stretch, and circuit means controlled by the signal relays for said two starting signals for energizing said indicator lamp only provided both of said signal relays are deenergized, whereby the manual clearing of one of said starting signals and the resulting deenergization of the signal relay for the other starting signal fails to eiiect the energization of said track indicator.

11. In a centralized trafc control system for a single track railway system having a stretch of single track connecting two passing sidings, a starting signal at each end of said stretch for governing the movement of traffic into said stretch from that end, at least one intermediate signal for governing traiiic in each direction through the stretch and acting to divide said stretch into two track sections, track relays for said track sections, a signal relay for each of said signals, an energizing circuit for each of said signal relays including track relay contacts for the track section in advance of its associated signal and controlled in accordance with the signal control relay for the next signal in advance governing traffic in the same direction, a communication system connecting a central oliice with the ends of said passing sidings, manually controlled means effective through the medium of said cornrnunication system for holding said starting signals at stop but acting when operated to allow one or the other of said starting signals to clear dependent upon the energized condition of its associated signal relay and at the same time acting to deenergize the circuits for the signals relays for each of the signals governing the opposite direction of traiiic, a single track indicator in the central ofiice for indicating when illuminated the occupied condition of said stretch of track, indication means associated With each starting signal for transmitting an indication over said communication system to said central oiiice when its signal relay is deenergized, and circuit means in the central oiice for energizing said track indicator only in response to the reception of an indication over said communication system that said signal relays for both said starting signals are deenergized.

CLARK A. PICKELL.

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