US2019467A - Centralized traffic controlling system - Google Patents

Description

Oct. 29, 1935. w. w. WENHOLZ CENTRALIZED TRAFFIC CONTROLLING SYSTEM Filed Jan. 28, 1951 INVENTOR ZU. 110m Patented Oct. 29, 1935 I UNITED sTArss CENTRALIZED TRAFFIC CONTROLLING SYSTEM Walter W. Wenholz, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application January 28, 1931, Serial No. 511,829

17 Claims.

This invention relates to centralized traffio controlling systems, and more particularly to a system of the unit line wire type, as distinguished from the system of the selector type.

In accordance with the present invention, it is proposed to control a distant switch machine over one line circuit, to control signals associated with the track switch operated by such switch machine over another line circuit, and to indi- 101; cate whether or not the track is occupied by a passing train and whether or not one of the various signals is indicating proceed, this through the medium of contacts at said track switch location, which open the line circuits used for controlling the switch machine and signals. It is of courseapparent that if the clearing of a signal were to open the line circuit controlling such signal for indicating purposes, such signal could not be maintained clear without the provision'of suitable stick means. Also, if the clearing of a signal were to be indicated over the circuit used for controlling the switch machine, this switch machine control circuit would not be available for indicating the passage of a train over the goztrack switch; also, switch machine operation could not be indicated over the signal control circuit, because the signals must be held at stop to operate the switch machine.

In accordance with the present invention, it so, is proposed to indicate over the switch control circuit the occupied or unoccupied condition of the detector track circuit associated with the track switch, and to indicate over the switch machine control circuit both the occupancy of .535 this detector track circuit and the clearing of the signal, from which it is apparent that, if the switch machine control circuit is open and the signal control circuit is closed, the switch machine control circuit must be open by reason of 49*; the fact that one of the signals is at proceed.

Another feature of the present invention resides in the provision of means for indicating an inconsistency between the signal control relay energization and the indicating condition of the 415;, signal controlled by such relay.

' Other objects, purposes and characteristic features of the invention will in part be more specifically pointed out hereinafter, and will in part be obvious from the accompanying drawing.

50:- In describing the invention in detail, reference will be made to the accompanying drawing, which shows conventionally the circuits and devices at an out-lying track switch location, and shows conventionally that portion of the central 55 office equipment for controlling the switch and signals at such location and receiving indications therefrom.

Referring to the drawing, the track rails of a railway system have been shown by the reference character I, which rails are divide-d into 5 track circuit sections by insulating joints 2. These track sections are each provided with a track circuit in the usual way, of which the detector track circuit containing the detector track relay DT and a track battery 4 have only for w convenience been shown. Only a portion of the. railway signalling system has been shown in the drawing, which portion includes one end of a passing siding PS and the end of a single track section 0. Traflic may move from the single 1 track section 0 into the side track of the passing siding PS through the medium of a track switch SW, which is preferably power operated, as by the switch machine SM.

Although the signalling system to which the 20 present invention is applicable may be a signalling system of the double track type, in which trafiic moves only in one direction oneaoh track, the invention has been shown applied to a single track railway system in which traflic may move 5 in either direction in response to signal indications, this single track section being signalled by a signalling system of the absolute-permissiveblock type.

This A. P. B. system preferably includes a main starting signal I and a dwarf starting signal 1 which signals govern the movement of traffic ofi of the main track and the side track, respectively, into the single track section 0, and

this track switch SW also has associated therewith a main entering signal 8 and a take-siding signal 8 These signals 1, 1 8 and 8 are controlled in accordance with trafiic conditions in advance, as through the medium of home-anddistance relays 'IHD and 8HD, and are further 40 manually controlled by the signal control relay SZ, the main track and side track signals being selected in accordance with the position of a manually controlled switch machine control relay WZ and a switch machine repeater relay WP.

In order to indicate through the same circuits used for controlling these control relays SZand WZ the condition of occupancy of the. detector track circuit, as well as the initiation and completion of the stroke of the switch machine, a relay OS controlled through the following circuit has been provided:beginning at the terminal or of the way station split battery, depending upon whether the switch machine SM is in its locked or in an intermediate position as manifested by the switch machine repeater relay WP, contact Ill of this relay W'P, wire ll, front contact it of the detector track relay DT, wire l3, winding of the relay OS to the midpoint C of said battery. This switch machine repeater relay WP is energized by the following circuitzbeginning at the terminal or terminal depending upon whether the switch machine SM assumes the main track or the side track position, switch machine contact !5, wire l6, winding of the relay WP to the midpoint C of the way station battery.

The switch machine SM is preferably cut out of service in the event that current has been flowing through the switch machine motor for too long a time or an excessive amount of current has been flowing through this switch machine, and for this purpose the cut-out relay CO and the associated thermal relay TR have been provided.

Referring now to the central office equipment, this central office, or dispatchers ofiice, has been conventionally illustrated by the dotted rectangle DO, and in this central oflice the entire railway system is preferably reproduced in miniature, as conventionally illustrated by the miniature passing siding ps corresponding in every detail to the actual passing siding PS; In this central ofiice D0 are located the necessary levers for controlling the various switch machines and signals, and in the particular arrangement shown only the signal lever LS and the switch lever LW, and their associated-cont-acts and relays have been illustrated. The signal lever LS is connected to the signal control relay SZ through the medium of the line wire 20 and includes in series therewith an indicating relay IE and the switch lever LW is connected to the switch control relay WZ through the medium of a line wire 21, which has included in series therewith an indicating relay 1R located in the central ofiice DO. The indicating relay 1R has associated therewith a slow acting repeater relay RR which is slow to pick up.

The switch control lever LW is normally left in the main track position, in which it has been shown, and in which position the switch control relay WZ is energized toward the right through the following circuit: beginning at the terminal of the central office split battery, switch lever LW, wire 23, winding of the indicating relay 1R line wire 2i, front contact 24 of the relay OS, wires 25 and 25, back contact 2'! of the relay SZ, wire 28, winding of the relay WZ to the common return wire C connected to the midpoint of the central oiiice battery. Also, under normal conditions of the apparatus the cut-out relay CO is energized through the following circuit:-

beginning at the terminal of the way station battery, wire 3i contact 3! of the thermal relay TR, wire 32, winding of the relay CO, wires 33 and 34, stick contact 35 to the other terminal of said battery. The current thus flowing through element I05 is insufiicient to cause it to open the contact 31.

Although the normal circuit for the switch machine including the normal wire N appears to be closed, this circuit is broken within the switch machine SM, this switch machine preferably being one of the type shown in the patent to Howe No. 1,466,903 dated September 4, 1923, wherein the operating circuits are broken upon completion of the stroke of the switch machine. It is believedthat the novel features of the system as well as its operating characteristics are more readily understood by considering the operation of the systemfwhich will now be taken up.

Operation It is, of course, understood that the track switch SW assumes its main track position, and let us further assume that there is an east bound train moving in the single track section 0, and that the operator wishes this train to move into the main track of the passing siding PS. In order to accomplish such east bound train movement, the operator will move his lever LS to the right, thereby energizing the signal relay S2 to its right hand energized position through the following circuitz-beginning at the terminal of the central office split battery, signal contact LS, wire it winding of the indicating relay 1R line wire 2%, front contact ll of the relay OS, wire 52, winding of the relay SZ, through the common return wire C connected to the mid- 20 point of the central oflice battery.

The completion of this circuit will of course energize the relay SZ to the right, thereby lifting its back contact 21 and opening the circuit for the indicating relay IE and thereby allowing the contact 5 1 of the indicating relay IR? to drop to its retracted position and opening the circuit (from minus, finger 44 and front point, wire 8|, lamp EI, wire 80, lever 45, wire 19, finger lit and f-ront point, wire l3, lever H, to plus) for the eastbound indicating lamp EI, which circuit would have been closed through the medium of the signal lever contactde and the front con. tact 46 of the indicating relaylR fromwhich it is apparent that the east bound indicating lamp E1 is still extinguished. With the signal relay SZ now assuming its energized position the signal it will be cleared through the following cirdu'it:" beginning at the terminal of the way station battery, front contact 48 of the detector track relay DT, wire 49, front contact '50 of the relay SZ, wire 5!, polar contact 52 of the relay SZ assuming its right-hand position, wires 53 and 54, polar contact 55 of the relay WZ, wire 56, neutral contact iii of the relay WP, wire 58', ,polar con,- tact 59 of the relay WP, wire "(ilL'neutral contact iii of the home-and-distance relay BHD, polar contact 62 of the relay 'BHD, assuming its solid line or dotted line position depending on trafiic conditions ahead, and through the clear or cautionwire for the signal 8 conventionally shown by the dotted line 63.

Clearing of the signal 8, by the opening of its semaphore contact 66 will break the energizing circuit for the signals-at-stop relay M, the circuit for which relay may be traced as follows: beginning at the terminal of the way station battery, semaphore contact 61 of the signal 1 closed only when this signal assumes the stop position, wire 68, signal contact 69 of the signal 1 closed only when this signal i is at stop, wire to, contact 66 of the signal 8, wire II, contact 12 of the take-siding signal 8 closed only when this signal a is at stop, wire 13, windingof the relay M to the other terminal of the way station battery. g

The breaking of this 'circuitat the contact 66 causes the :relay M to assume its deenergized position, thereby eifecting closure of'its lbackrcontact i5 and effecting reenergization of the indicating relay 1R (through a circuit including plus, lever LW, wire 23, relay 1R wire 2|, finger 24 and front point, wire 25, finger I5 and back point, wire '28, relay WZ, to common) thereby completingthe following circuit for the east bound indieating lamp EI:-beginning at the terminal of the way station battery, contact H of the lever LW, wire 18, front contact 46 of the relay 1R wire 19, contact 45 of the lever LS, wire 88, indicating lamp EI, wire 8|, front contact 44 of the relay 1R to the other terminal of said central oflice battery.

In response to this clearing of the signal 8, the train under consideration may, of course, move from the single track section 0 into the main track of the passing siding-PS. As this train passes the signal 8 and treads upon the detector track circuit containing the track relay DT, this track relay DT is deenergized, thereby opening its contacts I2, 48 and 65. Contact 98 is included in the clear and caution circuit for the signal 8, so that the signal 8 will be actuated to its stop position; the contact 55 is included inthe clearing circuit for the take-siding signal 8 and the contact I2 of this relay DT by its dropping opens the energizing circuit for the relay OS, which in turn breaks both of the line circuits 20 and 2| through the medium of its contacts 4| and 24.

Simultaneous breaking of the two line circuits 20 and 2| causes the indicating relays IR and IR to simultaneously move to their deenergized position. Dropping of the indicating relay 1R effects extinguishment of the indicating lamp EI and energization of the slow acting repeater relay RR, but by reason of the slow acting characteristic of this relay RR its contact 83 will for a time remain in its retracted position, thereby momentarily completing the following circuit for sounding the bell, or other suitable audible sig-= nal, BL:beginning at the terminal of the central ofiice battery, contact ll of the switch control lever LW, wire I8, back contact 3-6 of the relay 1R wire 84, back contact 85 of the relay 1R wire 88, back contact 83 of the repeater relay RR, wire 87, bell cut-out key 88, wire 89, winding of the bell BL, to the other terminal of said central office battery. Completion of this circuit sounds the audible signal BL and after a short period of time the contact 83 will have been operated to its attracted position, thereby completing the following circuit for the detector track circuit occupancy lamp I:-begin.ning at the terminal of the central oflice battery, elements 11, 18,46, 84, 85, 86, 83, and 99, track occupancy indicating lamp I, to the other terminal of the central office battery. The operator at the central ofiice is therefore informed by the extinguishment of his east bound indicating lamp EI that the signal 8 has been moved to the stop position, and has further been informed by the sounding of the audible signal BL and the illumination of the indicating lamp I that the train in question has entered upon the detector track circuit containing the track relay DT.

As soon as the rear end of the train under consideration passes off of this detector track circuit the delay OS is energized and the contacts 4| and 24 are reclosed. Reclosure of the contact 9| effects reenergization of the relays IR and SZ, but reclosure of the contact 24 will not effect reenergization of the relays IR and WZ, because the signals-at-stop relay M is now again energized, the signal 8 having been moved to stop, so that the contact I5 of this relay M is open, as is also the contact 2'! of the relay SZ, so that the indicating relay IR remains deenergized. With the relay IR in the central office DO deenergized and the indicating relay IR in the central oflice DO energized, none of the indicating lamps I,

WI or EI in the central ofiice can be illuminated, as is readily apparent by observing the circuits for these indicating lamps.

As soon as the train in question has moved beyond the danger distance signified by the stop 5 position of the home-and-distance relay 8HD, this signal 8 will be moved to caution, and with the signal 8 at caution the opening of its contact 66 will effect deenergization of the relay M, thereby reclosing the circuit including the line wire 2| 1 and effecting reenergization of the indicating a relay 1R With the indicating relays IR and IR both energized the east bound indicating lamp E1 is again illuminated through the medium of the circuit heretofore traced. From the fore- 15 going consideration it is apparent that a continuing indication of the occupancy of the detector track circuit containing track relay DT is indicated by continued illumination of the track occupancy indicator lamp I, and that the g0 movement of any one of the signals I, I 8 and 8 from the stop position is continuously indicated by the indicating lamps WI or E1 depending uponthe direction governed by the signal which is assuming a proceed position. Further, it will be 25 noted that the signal 8 could not be cleared or operated to caution unless the relays WZ and WP, which respectively control, and are controlled by, the switch machine SM, assume corresponding positions.

For a train moving in a westwardly direction from the main track of the passing siding PS into the single track section 0, the operation of the apparatus is identical to that just considered, except that the polar-neutral signal control relay SZ is energized to its left hand position, thereby completing the following energizing circuit for the signal 'lz-beginning at the terminal of the way station battery, front contact 48 of the detector track relay DT, elements 49, 50, 5|, 52, 40 92, 93, 94, 95, 98, 91, 98, 99, I89, the caution or clear wire for the signal I conventionally'indicated by the dotted line IOI, to the other terminal of the way station battery.

Let us now assume that there is a west bound train on the side track of the passing siding PS and that the operator, or dispatcher, wishes to allow this train to proceed into the single track section 0. The operator will of course first place the signals in the stop position by operating the signal lever LS to its middle position, this in order to allow certain time or approach locking means to function to permit operation of the switch machine, this time or approach locking means having for convenience been omitted from the drawing, but being shown in the prior application of Wight Ser. No. 120,423 filed July 3, 1926. The operator will then move his switch lever LW to the dotted position, and thereby will operate the switch control relay WZ to its left hand dotted position through the circuit heretofore traced, except that this circuit is now energized by current of negative polarity.

With the polar-neutral switch control relay WZ operated to its left hand position, the following circuit for operating the switch machine SM to its reverse take-siding position is closed:--beginning at the terminal front contact I03 of the relay CO, wire I84, heating coil I05 of the of the switch machine SM to its take-siding position,sandwhen the switch machine SM has completed its operating stroke and has been locked up the circuit just tracedis again broken by contacts associated with the switch machineiitself. The contact l5 in theswitchmachine is moved to an intermediate position upon initiation of movement of the switch machine and remains in the intermediate position until "the switch has completed its operating stroke and has again been locked up, at which time this contact assumes its other extreme position, so that the switch machine repeater relay WPis deenergized as soon as the switchmachine SM is initiated upon its operating stroke.

'This dropping of the relay WP reverses'the direction of current flow through the relay '05, so that this relay OS is momentarily deenergized because the magnetism within its core structure must pass through zero and thereby momentarily drop its armature. This momentary dropping of the armatureof the relay OS efiects momentary opening of the "contacts 24 and 4l,but since the signal lever LS is in its intermediate position the opening of the contact'M serves no'function at this time. Momentary :opening of the contact 24 will eifect momentary deenergization of the indicating relay "IE and this momentary deenergization of the indicating relay IE 'will effect momentary sounding of the audible signal a BL and momentary flashing of the indicating lamp I, all for reasons heretofore explained and stating it'briefiy is accomplished by dropping of the contact 8'5 of the relay IR and picking up of the contact 83 of the repeater relay RR, there being a slight additional delay in the operation of the contact 83 after operation :or the contact '85. Also, if desired the relay RR. may be sufficiently slow acting as compared with the relay OS that no flash of the lamp I is-given-at this time. As the switch machine completes its operating stroke the switch machine repeater relay WP is reenergized, but at this time is energized to its left hand position, and the reenergization of the relay WP again eifectsmomentary deenergization of the relay OS, this becausethe direction of current flow in the relay OS is again reversed.

The operator having now been informed of the completion of the stroke of the switch-machine, and since, as has been assumed, he desired to set up west boundtrafiic off of the si'de track of the passing siding PS,he will operate' his-signal lever LS to the lefthand position, thereby energizing the signal relay SZ to its left hand energized position, under which condition "the follow- 'ing circuit for the dwarf starting signal I is -closed:beginning at the "terminal of the way station battery, front contact 48 of the detector track relay DT,"elementS lQflSDQ-B I 52,"-92,

IH, '91, 96, 95, 94, ll2,"frrit contact l'l'iof the 'home-and-distant relay II-ID, polar contact "114 of this same relay throug'hthe clear or caution wire for the dwarf signal'l depending on theex- 'tent of unoccupied track ahead as manifested by the position of the polar contact N4 of thewrelay 'IHD, through the mechanism of the dwarf :signal'1' ,'to the other terminal of "the way station battery.

Clearing of this signal "i will allowthe train to move off of the side track into thesingle track section 0, and this movement of the train will be indicated through the medium of the track occupancy indicator I in the central ofiice DO,

*andalso the clearing o'f'the signal I will bein- "clicated at the central ofiice -through the medium of indicating relay 'IRP.

of the west bound rindicatorWI, this signal lamp WI'being controlledthrough'the medium of the wire '-I I5 insteadof wire "80 of'the circu'rtahenetofore traced for the indicating lamp :EI. 'Itiis readily illIldBI'StOOdthLt the take-siding signal :8 5 is controlled in -accordance with the positionof the relays SZ, WZ and WP and in accordance with theipositioniof'the contact'iiE of :the detector track relay'DT, all a manner readilyfindicated by the contacts of these various relays. Attention is particularly directed to the-fact that none of the signals 'l, i -8, or 8 can be clear unless the relays WZ and "WP, respectively 'controllingyand controlled 'by, the switch machine iSM, assume corresponding positions. ;'It will be noted that fthese'various signal circuits include neutral contacts of the switch machine relay WP but do not'inclu'de neutral contacts of .the switch machine control relay WZ; theneutral contacts of'the relay WZ have been omitted 'forthe reason'that the relay WZ =is'at timesndeenergized, as "for instance whenthe signals are at stop and the contact'15 of the relay'Miassumes its raised position. Further w'ithrelayiSZ 'energized'to clear a signal the contact Tlisopen, 5 under which condition it is apparent thatthe signals could not be cleared if neutral front-contacts of the relay WZ were included'in the :signal control circuits. The signal circuits are .so organized'that polar contacts of .the'relays -WZ and "WP must assume corresponding positions, so'that if the switch machine should not complete its stroke or s'houldnot at all'respond to a change in'the position of its control relay WZ, it would result .in holding all .of the signals as-- sociated with the track switch SW at stop.

Applicant has thus provided acircuit arrangement in which the condition of'track occupancy is transmitted over one line circuit, namely through the medium of the indicatingrelay IE o and the condition of :track occupancy as well as the condition of signal clearingis indicated over another line circuit, as through the medium It is therefore ,possibleto interpret at the central oifice the indicat- 5 ing condition of 'thesignals located at'the distant track switch, this by comparing "the ':indications received over the two line circuits, -which comparison is accomplished'through the medium of the slow acting repeater relay RR and the V various contacts associated with the relays/IR},

IE and RR.

Having thus shown and described one rather specific embodiment of the present invention, it is desired to be understood that the particular circuit arrangement illustrated in the drawing has not been selected for the purpose OfiShOWiIlg the scope of the invention, nor has 'itbeeniselected for the purpose of illustrating the eonclaims.

What I claim asnew is:-- I. In a centralized traffic controlling system,

in combination, a central officeianda distantztrack 5 switch, signals associated with said track switch, a switch machine ior operating said track switch, aiswitch control circuit including the contact of a lever and for controlling said switch machine, r5 9. signal control circuit including the contact of a second lever and for controlling said signals, means for indicating occupancy of a section including said track switch over said signal control circuit, and means for indicating over said switch control circuit the proceed condition of 'a signal when a section including said track switch is unoccupied.

'2. In-a centralized traflic controlling system, the combination with a central ofiice and a dis- ]5? tant track switch, signals associated with said track switch, and a switch machine for operating said track switch, of a switch control line circuit including a contact of a lever and for controlling said-switch machine, a signal control line circuit including a contact of a second lever and for controlling said signals, means in said central office for indicating the continuity of said signal control circuit, means in said ofiice for indicating the continuity of said switch control circuit, means 255: for opening said signal control circuit during occupancy of a section including said track switch, and means for opening said switch control circuit when all of said signals indicate stop and the section including said track switch is unoccupied providing said signal control circuit is energizedJ g '3. In a centralized traffic controlling system, in combination, a central ofiice, and a distant track switch, signals associated with said track switch,

351: a switch-machine for operating said track switch, a switch control line circuit for controlling said switch machine, a signal control line circuit for controlling said signals, means in said central office for indicating the continuity of said sig- 40' nal control circuit, means in said office for indicating the continuity of said switch control circuit, means for opening said signal control circuit during occupancy of a section including said track switch, a signal control relay in said siga.nal control circuit,- and means for opening said switch control circuit when said section is unoccupied and also said signal control relay is out of correspondence with the signal controlled by said signal control relay.

59?; 4. In a centralized traffic controlling system,

the combination, with a central oiiice and a distant track switch, signals associated with said track switch, and a switch machine for operating said track switch, of a switch control circuit Gincluding a switch lever contact and for controlling said switch machine, a signal control circuit including a signal lever contact andfor controlling said signals, means for indicating occupancy of a section including said track switch toe over said signal control circuit, and means effective if said signal control circuit is energized to clear one of said signals and to render said switch control circuit effective to indicate if such signal has been cleared.

5. In a centralized trafiic controlling system,

the combination with a central office and a distant track switch, signals associated with said track switch, and a switch machine for operating said track switch, of a switch control line circuit including a switch lever contact and for controlling said switch machine, a signal control line circuit including a signal lever contact and for controlling said signals, means for opening said switch control circuit when all of said signals indicate stop, means for opening said signal control circuit when said track switch is occupied by a train, a signal-at-proceed indicator at said central ofiice rendered effective when neither of said control circuits has been opened, and a track switch occupancy indicator 5 rendered effective if both of said line circuits have been opened.

6. In a centralized trafiic controlling system, the combination with a central ofiice and a distant track switch, signals associated with said 10 track switch, a switch machine for operating said track switch, a switch control line circuit for controlling said switch machine, a signal control line circuit for controlling said signals,

both of said line circuits have been opened, and

means for selecting a particular one ofsaid two indicators depending on the position of a control 25 lever for controllingenergization of said signal control circuit.

7. In a centralized traflic controlling system, the combination with a central oiiice and a distant track switch, a signal associated with said 30 track switch, a switch machine for operating said track switch, a switch control'circuit including a switch lever contact and for controlling said switch machine, a signal control circuit including a signal lever contact and for controlling-35 said signals, and means for indicating occupancy of a track section including said track switch over said signal control circuit.

8. In a centralized trafiic controlling system, the combination with a central office and a dis-' 4g tant track switch, signals associated with said track switch, and a switch machine for operat. ing said track switch, of a switch control circuit including a switch control lever and for controlling said switch machine, a signal control cir- 45 cuit including a signal control lever and for controlling said signals, and means for indicating over said switch control circuit the proceed condition of a signal when a section including said track switch is unoccupied. 1

9. In a centralized trafiic controlling system, the combination with a central ofiice and a distant track switch, a signal associated with said track switch, a switch machine for operating said track switch, a switch control circuit including the contacts of a switch control lever for controlling said switch machine, a signal control circuit including the contacts of a signal control lever and for controlling said signals, and means for indicating over said signal control circuit the 50 initiation of operation and the completion of the stroke of said switch machine.

10. In a centralized trafiic controlling system, the combination with a central oflice and a distant track switch, signals associated with said 5 track switch and a switch machine for operating said track switch, of a switch control circuit controlled by a track switch lever and for controlling said switch machine, a signal control circuit including the contacts of a signal con- 70 trol lever and for controlling said signals, and means for indicating over said switch control circuit the fact that said signal control circuit is energized and a signal has responded to such energization. 75

11. In a control System for railway switches and signals, the combination with a local office and a distant way station, a power-operated railway track switch at said way station, a signal for governing traffic over said track switch, a lever in said ofiice for controlling said track switch, a lever in said office for controlling said signal, and an indicator in said office controlled to be energized when said signal is clear and including an energizing circuit closed only if said switch machine lever assumes an operating position and said signal lever assumes a signal-clear position.

12. In combination, a track section including a railroad track switch, a signal for governing trafilc over said track switch, a switch machine for operating said track switch, a switch control lever, a signal control lever, a switch control circuit energized in accordance with said switch control lever for governing the operation of said switch machine, a signal control: circuit energized in accordance with said signal control lever for governing the operation of said signal, and means opening .both said switch control circuit and said signal control circuit to indicate an occupied condition of said track section,

13. In combination, a track section including a railroad track switch, a signal for governing trafilc over said track switch, a switch machine for operating said track switch, a switch control lever, a signal control lever, a switch control circuit energized in accordance with said switch control lever for governing the operation of said switch machine, a. signal control circuit energized in accordance with said signal control lever for governing the operation of said signal, means contemporaneously opening both said switch control circuit and said signal control circuit when said track section is occupied, and means responsive to the open condition of both of said circuits to indicate when said, track section is occupied. V

14. In combination, a track, switch, a signal for governing traffic over said track switch, a switch machine for operating said track switch, a switch control lever, a signal control lever, a normally energized switch control circuit which is energized in accordance with the position of said switch control lever for governing the operation of said switch machine, a signal control circuit energized in accordance with said signal control lever for [clearing said signal when said circuit is energized, means opening said switch control circuit when said signal control circuit is initially energized, means for reclosing said switch control circuit when said signal has cleared in response to energization of said signal control circuit, and means responsive to the energization of both of said control circuits for indicating the clear condition of said signal.

15.v In combination, a track switch, asignali for governing traffic over said track switclna: switch machine for operating said track switch,

a switch control lever, a signal control lever, a: normally energized switch control circuit which 5 is energized in accordance with the positizm or said switch control lever for governing the opera;- tion of said switch machine, a signal control cir cuit energized in accordance with said ml: control lever for clearing said signal when said; 10 circuit is energized, means opening said switch control circuit when said signal control circuit is initially energized, means for reclosingisaidv switch control circuit when said signal: has cleared in response to energization of said signal! 15 control circuit, means always effectivetos opens both said control circuits upon the occupied; more dition of a track section associated with said track switch, means responsive to the energize,- tion of both of said control circuits for indicating 20' the clear condition of said signal, and means. reisponsive to the deenergization, of both. of. said control circuits for indicating the occupied cone dition of said track section.

16. In combination, a track switch, a switch 25, machine for operating said track switch, aiswitclr control lever, a normally energized switch.- con-- trol circuit which is energized in accordancewitlr the position of said switch control lever for gov.- erning said switch machine, over-load means. tor 30 said switch machine effective to remove 1311816011 trol of said switch machine from said: switch: control circuit when an over-load condition occurs.

a detector track section associatedv with said: track switch, means effective upon the occupied. u-r. condition of said track section to open said switch control circuit, means responsive to the deenergization of said switch control circuit to restore the control of said switch machine to said switch. control circuit, and. means responsive to the de- 4 energization of said switch control circuit to indicate at said switch control, lever the occupied condition of said detector track section.

17. In combination; a track section including a railroad track switch; asignal for governing trafiic over said track switch; a switch machine for operating said track switch; a. switch control circuit for governing the operation of said switch machine, said circuit including a current source, lever contacts, a switch control relay and con- 5 necting wires; a signal control circuit iorgoverning operation of said signal, said circuit inclu.ding a current source, lever contacts, a signal con.- trol relay and connecting wires; means opening said switch and signal control circuits when said track section is occupied; and means responsive to the contemporaneous deenergization of both said control circuits to indicate the occupied condition of said track section.

- WALTER W. WEN'HOLZ, I,

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