Патент USA US2396134код для вставки
2,396,134 Patented Mar. 5, 1946' ’ UNI TED STATES ' ~ PATENT; QFFmE 2,396,134< REMOTE“ ("JGNTRGE SYSTEM" The Union Switch & Signal Gunman-y,v Swiss- > vale,-Pa.,, a corporation‘ of, Bennsxlvania. ApplicationDecem-ber 17, 119453;, Serial; No: 514,641‘ V 18v Glaimsc (c1. mgr-ass): My- invention- relates to ‘remote control ‘sys toms,- and more particularly to centralized ‘traffic control systems for railroads for'the control of railway signals or other tra?ic controlling‘devices from a central point of control: such as a train dispatcher’s o?ice; and‘ for'the, indication of such devices or of train movements ‘at the control o?ice. The transmitting’ portion of the system ‘of ‘my invention is claimed in my‘divisionalapplication, Serial No. 561,563; ?ledv November’2, ’1944,_ for Transmitting apparatus for remote control sys tems. ‘ One’ object of‘ my invention isthe, provision of a system» suitable for the direct control of‘ un attended manual block signals employing" cur rentsof such-a ‘character that they'maybe trans bytrain'iorders, supplemented by ‘manual control‘ 'o'f-ithe: signals. of’ my inventiondprovides facilities by which ‘the signals“ at ‘each of ten stations-“may- be selectively controlled‘ to give-proceed; permissive 'or- stop in di'cationsiiby the lighting of the lamps-G, Y‘ or respectively of the signals and; RH, in re sponse tothe operation of suitable push "buttons PS‘ and" PF‘at the control 'o?‘rce, and. also pro vides‘meansrfor lighting selected indication lamps Eat the o?ice to’ indicate whengthe corresponding signals are at stop; each‘ lamp; being lighted automatically-when atra-in enters. the correspond ingudetectorsection. their‘ use for other communication purposes; cation'transmitting-relay Ll‘; At?ve 'of‘t'he sta 20 ti'ons, adjustable connections are made to contacts a1 and‘ e-‘of‘relay‘Rl' to render relay>R3i responsive to line ‘signals ‘when relay RI is energized. ~At theremaining- ?ve stations; the connections are shifted‘to contactsw and‘ c ‘of relay R2 to render relay R3; responsive to line“ signals when relay R2‘ is energized. Each selector relay R3 is‘ ar ranged‘. to’ he energized‘ through "a recti?er unit I'll, when‘ the unit is supplied with ‘alternating in which the codes-comprise- di?erent sequences of impulses of alternating "currentsof 'diiferent frequencies‘ within a hand of frequencies prefer ably in the voice frequency range or at least in'a range- which is‘ suitable for transmission over 7' ' proceeds; ' ' _ control relays 1LHS,_RHS and 'DS, and an indi of a system for communicating by code between a- controlo?'ice and, a plurality of’remotestations; Other objects, features and purposes of‘my invention will ‘he pointed out as the description , three»selector-‘relays-Rl, R2 and R3,_ three signal Another’ object of my-invention is the provision existing telephone‘ circuits. _. ‘ The apparatus provided at each-1 station includes mitted at times over existing railroad" com-mum' cation circuits without interferingmateriallywith ‘ "In-its'speci?c embodiment; asshown, the system ' current from“ a! tuned’ circuit comprising a coil -" ; l2 and a condenser Ch. ’ ‘Each-such tunedj circuit is adapted to- pass su?i'cient current to energize the» associated relay only‘ when supplied ‘with current of‘ a particular ‘frequency received over ' I shall describe one form of apparatus ‘em-‘ the‘ line-wires andYZ. In the system as shown, bodying my invention, and shall ‘then. point ‘out ‘-‘ the control of ten- stations 'is-contemplatedg, and a the novel features thereof'in' claims. band of3 ten- frequencies ,?- to fill1 is used, ?ve Referring to the accompanying drawing, the of'whi’ch; namely, the frequencies ft to‘ ii, ‘are reference" characters Y and‘ Z‘ designate a pair. of line wires which ‘it is to be understood. provide a telephone circuit extending, from ,a control o?ice at which the apparatus atthe left of the employed to select the-stations; 1 etc: indicating the frequency to- which each tuned drawing is located, through aplurality of stations situated‘ at spaced points alonga stretchffof. raiL' way at each of which stations a,’ pair'of manual block signals LH and RH islocatedl as indicated by the trackv diagram, eachstation beingv provided with apparatus similar to that. shown at the right of‘ the drawing, having aiconnection to the line wires Y and Z asshown. It may be- assumed that, the stretch is not, provided; with. track , ‘ circuits except for a short detector section ‘B at each station having a track .itelayy for: the . In; the-drawing,‘ the reference» characters’ fl, f2‘, circuit isresponsive; are; adjacent the cir cuit: ‘the circuit for relayiR3‘, for example; at, the station shown; being selectively responsive to' the freuuency?i.v ' ‘ ‘ a ' p' The ‘relays-'R‘Iiand Rzare direct current relays ofthe biased polartype which" respond selectively to the steady‘ component of the current supplied to the line wires 'Y_ and Z, a reactor 13 being in terposed! in’ the line connections, relay- RI’ re spending only when linewire Y positive'and relay' 1R2" only’ when line wire- Y is‘ negative; with respect t'o-l'ine wirejZ. At. each of; five stations; relay‘ vR31 is arranged to respond to a diiierent control of-the-signalsand for'indicating theimove one volF-the frequencies flf to 15'» provided relay R1 ments ofv trains past the stationsyand that train movements through the stretch are'governedl prii» 55‘ is: picked up; the line connection» for the timed 2,396,184 circuits including contact a of relay RI as shown. At each of the remaining ?ve stations, relay R3 RHS are both in their released positions, an im~ pulse of current of a selected frequency in the is responsive to a di?erent one of the frequencies band fI—fI0 will be supplied to the line wires fl to f5 provided relay R2 is picked up, its tuned over back contacts e of relays LHS and RHS, circuit being adjustably connected to contact a 5 front contacts b and c of relay LI, back contacts of relay R2, and it follows therefore that the re b of relays RI and R2, coil I5 and condenser C4, lay R3 at any one of the ten stations may be se the impulse terminating with the release of relay lectively energized by a single impulse of pulsat LI, which relay is slow acting. Relay LHS or ing current having one of two polarities and one RHS’ is released automatically following the re of ?ve frequencies. ' ‘ ‘ ' 10 lease of relay TR by a train, and since relays LHS Each relay R3 is provided with a stick circuit and RHS are slow to release, as shown, relay LI extending from the positive terminal B of a local becomes energized over a circuit closed momen source of direct currentat the station over con tarily which extends from terminal B at back tact c of the relay RI or R2 which controls its contact a of relay TR, over front contact d of re pick-up circuit, as indicated diagrammatically on lay LHS or RHS through relay LI to terminal C the drawing, over the front contact a andlower and the indication impulse will be transmitted winding of relay R3 to the negative terminal C during the release period of relay LI following of the local source. It follows that relay R3 at a the release of relay LHS or RHS. selected station may be held picked up, along It will ‘be seen that since back contacts 11 of with relay RI or R2, after the alternating current 20 both line relays RI and R2 are included in the impulse is terminated, provided direct current continues to be supplied to the line. Under these circumstances the tuned circuits for relays DS, LHS and RHS, which are responsive to alternat ing currents of frequencies f6, fl and f8, respec tively, in the same manner as relay R3, are con nected to the line over contact a of relay RI or R2 and contact b of relay R3, and if a second impulse of frequency f6, fl or 18 is supplied to the line, relay DS, LHS or RHS may be ener gized, while if a second impulse of frequency fl or f8 followed by a third impulse of frequency 16 is supplied to the line, relay LHS or RHS may be energized and relay DS in addition Each of the relays LHS and RHS is provided with a stick circuit including its own front contact a, a back circuit for transmitting the indication impulse, its transmission cannot occur when the line is in use for transmitting control impulses to any of the ten stations. At the control office, the indication receiving apparatus includes a set of ten indication relays KI ‘to KID, of which but three are shown, each ' controlled over a tuned circuit similar to that provided for the station relays but tuned to a 30 different one of the ten‘frequencies II to II II. Re lay KI, having its circuit tuned to the frequency it, responds vto the indication impulse received from the station shown and is then held energized overa stick circuit until manually released, light ing a lamp E I to indicate that the signals LH and RH at the corresponding station stand at stop. The office transmitting apparatus includes ten the track relay TR of the detector track section sets of manually operable selecting contacts, con T, consequently if either relay RHS or LHS is trolled by a series of push buttons PS, for select energized it may be released manually by opera 40 ing the stations, of which for simplicity but three tion of relay R3, or automatically by a train en are shown, namely PSI, PS2 and PSII]; ?ve sets tering section T. Relay DS has a stick circuit of manually operable control contacts, controlled including its own front contact a and front con? by another series of push buttons PFI to PF5, tact c of relay LHS or RHS and consequently will inclusive, for governing the signal control relays be released along with relay LHS or RHS, if en 45 at the selected_station; a set of ?ve relays PC, ergized. Relays LHS and DS jointly control the DR, OR, L andLP for governing the transmis lamps R, Y and G for signal LH, and relays RHS sion .of the impulses, and an oscillator including and DS similarly control those for signal RI-l in the electron tube VT for generating the alternat a well-known manner which may be readily as ing current of the desired frequencies. certained from the drawing. 50 The operation of contact a of any of the push contact 0 of relay R3 and a front contact a of The station apparatus also includes a source of buttons PS opens the stick circuit for the asso alternating current of a particular frequency in ciated indication relay K, and closes a circuit for the band of frequencies f I to 1‘ I0, which source as ' energizing relay PC, which relay is of the polar shown may be understood to be an electron tube stick type and serves as a pole changer to govern oscillator OSC similar to the one including the 55 the polarity of the direct current supplied to the tube VT at the office as hereinafter described. line from a local source having the terminals B The output circuit of oscillator OSC is adapted to and C, as shown. It is to be understood that the be connected to the line wires Y and Z, at times, operation of any one of the buttons PI to P5 ener in response to the operation of relay LI, to indi gizes the upper winding of relay PC to cause it cate that relays LHS and RHS are released and 60 to operate its contacts a and b to the left as that the signals are consequently at stop. When shown to render'the relays RI responsive, while relays RI or R2, R3 and D3 are operated, relay the operation of any one of the buttons P6‘ to LHS or RHS will be released by relay R3, if ener PI Il energizes the lower winding of relay PC to gized, and relay LI picks up over the circuit ex cause it to operate its contacts to the right, to tending from terminal B at contact 0 of relay gender the relays R2 responsive to the steady uI or R2, front contact a of relay R3, front con component of the line current. The opening of tact d of relay DS, back contacts (1 of relays LHS contact 21 of any of the buttons PS disconnects and RHS through relay LI to terminal C, and is the circuits controlling the indication relays KI held energized over the stick circuit including to KID from the line, rendering these relays non its own front contact a, and extending to termi~ 70 responsive to the control impulses. The closing nal B at contact 0 of relay RI or R2. When re of the contact 0 of any ‘of the buttons PS com lay LI is picked up by a control impulse in this pletes a connection from the line wires Y and manner, its energizing circuit is opened as soon Z to the output coil I6 for the oscillator VT, as the line becomes free, as indicated by the re through a recti?er I8 and a condenser C5, while lease of relay RI or R2 and if relays LHS and the‘closingv of contact d of the operated‘button r‘ 3 aaearac PS; completes a; tunedi circuit: including? coil: l1 and: condenser (it for: controlling the frequency generated by the; electron tube VT; and delivered tow the line by. coil: to.‘ Contacts: dot: buttons. s-ivezindicatlnn, whileBEt andlmcon~ troli relaysv LHSI respectivelytand: relax DS in addition, to- cause the selected‘signal:t'lrv mdi‘cate proceed. ' 'I j PSt- toPSliI are each connected to a. different. tap (‘In relay Assuming: OR willthat be shunted button. PF-t by the is new closinguo?the‘ on coil [1: to cause the: generation. oi'ja, different one of theirequenciesifl to f5-,._ respectively, but tons PS6: to PSI 0: being similarly‘ connected to cause. thee generation , of the same frequencies; Hayingzthusdescribed the various components or the: system of: my invention, I shall. now ex plain: its mode ofv operation, assuming ?rst that" with the. apparatus as shown, the operator de-i push button contact.’ 0 and; will; release; opening its trolled contact by. bthe": in buttons the circuit PS6! fortocondenser PSlill‘; andi'com GI pleting attuned ‘circuit- atrits baclc contacttcxfronr the upper terminaliof-coil' t1’, condensencii front contact 11' of; relay: L.’ and: contact; a: ofi button: PF I! , to: the terminal‘ of coil li‘li marked ‘IF, cans» sires‘ to obtain a recall indication from the sta— i'ng‘ tube _V~T to- deliver current: of frequencwf?td tion shown to verify: therfactthat thesignals are at2stop; Hewill ?rst operate buttonv PSI, releas erg-izeslrelay‘ Ll-i at the‘ selected station. I Thezrez- ‘ the 1 line to energize relay DSI, which: turne en; ing relayKl: and thereby cancelling the existing indication displayed by lamp Eli, and operating lease of? relay ORi- deenergizes relay which; re~ leases after a brief? period-to terminatestheime pick up thedetector relay DR, provided the os pulse ofv frequency fl to energize“ relay'reKlli and‘ pulse, releasing relay» DSL, Relay- ]; deenergiizea relay PC‘rto normal, as shown. The oscillator tube VT will'be set.‘ into operation to supply cur- 20 relay LP which- releasesafterasecondi briefiperll rent‘- to: the line wires of frequency fl over the steady-"line od, in’ turn current releasing:thereby relay DRY ‘ releasing» tointerruptl relay‘v Rf, connection to coil I8 including contact cv of but The release» of‘ relay LP’ extinguishes lamp-GEE’ ton- PSI and recti?er I81. Contacts» d of relays indicating the return o?the con-trot» apparatusito RI and- R2 at each station are now‘v open and‘ the , alternating current delivered to- the line is prin 25 normal, whereupon button PF? may‘ be‘ released, while' the release of relay Rt deenergizesj relays cipally dueto thecapacity between linewires Y R3 and Li and‘initiates the-retu-m indication inr and This, however, is' of a value su?icient to cillatordelivers theproper- voltage and its con light the lampEl. nections to? the line wires are intact so as-to in clude the» line capacity in its output circuit. When relayDRIpicks up, unidirectional current is suppliedv to’ the‘ line- circuit including the relays El- and R2‘, over-the‘ connection from terminalsv ton Assuming P-S-l assabove next‘ that described the operator'presses and then after‘ree leasingibutton PSI presses button-PFZ'or P‘Fil; are impulse" of" frequency IT or I81 will be delivered‘ to the line for’ the duration of= the release period‘ relays illustrated by the relays L and LP which duration of the release-period of relay'L‘, to op» ~ ' ‘ ‘ ‘ B: andC-at contacts a and b of relay PC, contacts I : of relay'L to operate relayLHS or'RHS; which‘re lay will then'be‘ held energized over itsstick' circuit‘ b» and c' of‘ relay DR through the direct current includingL front contact a of'relayTR', butrelayi relay OR and coil [9 to the line wires Y and Z, Ll will not be operated and no’ indication imé thereby picking up relay'OR and also'the relays pulse will be transmitted, consequentlylamp-Ell‘ Rt‘ at all" stations to‘ open their contacts ‘him the will remain dark; , indication circuits, and to close- their contacts a, so If- button" PF4 or PF51 is operated'in; place of=' that relay R3-- at the selected station also picks button PFZ or PF3, an impulse of’frequency?‘ or‘ up; The closing of contact a of relay OR ‘com ~J‘8 will likewise bedeli-veredto the'line- fen-the plet'es a- circuit for energizing’a chain of' timing erate relay LHS or-RHS, but in this~instance=a= pick up successively, the closing" of contact a of tuned circuit will be completed upon the-release of relay L' including coil: I1, condenser 02} back‘ contacts 0 and; b of relays 0R1 and'~L; frontfcons» tact cv of relay LP‘ and contact‘Z'rof-‘the-operatedZ relay LP lighting a' control lampCE and corn- ‘ pl‘eting' a- local stick circuit for relay DR; It'will becnote‘d that the tuned circuit including coil l1 and‘ condenser C‘! which was completedv initially over back'contact b of relay-1GP» is now“ completed over front-contact‘ b of‘ relay OR, and that con-_ tact‘ e of relay DR provides a connection from coil" l‘B-tov the line in parallel with contacts 0 of button, so that‘ an" impulse of frequencyft‘ be delivered to the-line for the duration otitllev release period of- relay LP to operate relay DS; which relay will then be held energized ovenits buttons PS‘. i. It will be also notedv that if two of the buttons PS‘ which control di?erent frequen- - cies'are inadvertently operated at the same time, a portion of; the coil [1 will be short circuited by their" contacts at to’ prevent the generation of \ alternating’ current by the tube VT, the selection of more than one relay R3? at a time being thereby 60 prevented; , ' - When‘ lamp CE‘ becomes" lighted", the operated" button P'Sl may be released. The opening of its‘contact‘ d terminates the delivery of the alter nating‘current‘ component‘ of the" impulse, relays ' OR, L; LP, DR at‘t'he oflice, and relays RI and‘ R3" at the selected" station remaining energized‘ due? to" the flow of unidirectional current in the" line circuit. The operatorwi'll now pressv one of the buttons PF! to 2E5‘. Button PF! controls relayDS only; for the purpose of‘ initiating a‘ return indication when the signals. are" at stop. Buttons PFZ and PF3‘ control’v relays‘ IJHS‘ andv RL'HS, respectively,‘ to, cause- the‘selccted 'si‘gna'rto display itsrpermis is stick circuit including- ,contact' c‘ of‘ relay- 133$ or RHS. In this‘ case relay Lt isnoti operatedS because its circuit is opened‘ at back’contact-d‘ of; relay LHS orR-I-IS.prior to the'closing'of front‘ contact 12‘ of relay’DS, and therefore no‘imzli'cati‘onv impulse is transmittedand lamp‘ E‘I remained‘arl'r; It will be seen that relay Ll is“ operated by‘relay“ DS to? initiate a return indication impulseonlys when the operation of" relay DS‘ i‘s-jd'ue‘to” the‘ operation of button PM, as herei-nbefore dew scribed. ‘ ' ' ’ ' It will also be seen that after the signal'IlH? or RH‘ has been cleared, it may'be'put' manuallytoi stop and the return‘ indication initiated’ to/li’ght‘ lamp El by pressing buttons PSI and‘PFl, or‘ it will‘ be put automatically to- stop thev lamp El‘ lighted, due to the release of the trackrelayTR when a train governed‘ by the signal enters‘ sec tion T, in which case the signal‘ will remain- at stop, due to the release of-thecstick‘ rel‘ayLHSbr RHSiaftersection T is vacated; , v ' , - Although I have herein shown‘ and‘d‘escrlbli'i'lx 4 ‘2,396,134 only one form of remote control system embody‘ wires, corresponding circuit elements at di?erent ing my invention, it is understood that various I stations being tuned to different frequencies‘, a changes and modi?cations may be made therein within the scope of the appended claims without departing from the spirit and scope of my in holding circuit for each second line relay includ vention. , r ' Having thus described my invention, what I claim is: 1. In a remote control system, an omce and a plurality of stations connected by line wires, two ing a front contact of the associated ?rst line relay, a plurality of control relays at each sta tion having holding circuits controlled locally and having energizing circuits including front contacts of both line relays at that station and also including tuned circuit elements rendering each control relay at a station selectively respon line relays at each station, one of which is re sive to alternating current in the line wires of sponsive to direct current in said line wires and a frequency different from that to which the the other to alternating current of a distinctive other relays at such station are responsive, and frequency, said alternating current line relay be control means at the omce for supplying current ing connected to the line wires over a front con 15 of said distinctive character to the line wires for ' tact of the direct current line relay through tuned a brief period to energize the ?rst line relay at circuit elements responsive to a frequency to each station and for supplying a series of im which the corresponding circuit elements at other pulses of alternating current, each of a different stations are non-responsiva'a holding circuit for frequency, to the line wires to selectively and each alternating current line relay including front 20 successively energize the second line relay and contacts of both line relays at that station, a plu one or more of the control relays at a selected rality of control relays at each station having station during such period. holding circuits controlled locally and having en 4. In a remote control system, an ethos and a ergizing circuits includingfront contacts of both station connected by line wires, a line relay at line, relays at that static-n and also including 25 the station, a selective communication channel tuned circuit elements rendering said control re for controlling the line relay including a source lays selectively responsive to alternating currents of alternating current of controllable frequency of different frequencies in said line circuit, and at the o?ice, said line wires, and tuned circuit control means at the of?ce for supplying direct elements resonant to a particular frequency, current to the line wires for a brief period and for manually operable selecting means at the office supplying two impulses of alternating current of including a relay for establishing said channel selected frequencies to the line wires successively and means for supplying alternating current during such period to selectively energize a par thereto of said frequency to energize the line ticular control relay at a selected station. relay, circuit means for maintaining both the 2,. In a remote control system, an of?ce and a oflice relay and the station line relay energized plurality of stations connected by line wires, said after the manually operable means is released stations being arranged in two groups, a polarized and the delivery of alternating current to said relay at each station responsive to steady current channel is thereby interrupted, a plurality of in said- line wires, the polarized relays at the sta controlrelays at said station, control channels tions of one group being responsive to line cur 4 o for selectively energizing said control relays by rent of normal polarity and those at the stations alternating current from said source, following of the other group to line current of reverse po the release of said manually operable selecting larity, another line relay at each static-n respon means, each such channel including a front con sive to alternating current of a distinctive fre tact of said line relay and tuned circuit elements quency and connected to the line wires over a “3d rendering each control relay responsive to cur front contact of the associated polarized relay rent of a frequency different from those to which through tuned circuit elements responsive to a the line relay or the other control relays are re frequency to which the corresponding circuit ele sponsive, manually operable control means at the ments at other stations of the same group are not office effective when operated to release said o?ice responsive, a holding circuit for each such alter 50 relay, and timing means responsive to the release nating current line relay including a front con of said onice relay effective to supply an impulse tact of the associated polarized line relay, a plu of alternating current of a particular frequency rality of control relays at each station having selected by said control means to said control holding circuits controlled locally and having en channels to selectively energize a particular con— ergizing circuits including front contacts of both‘ : trol relay, and to then release said line relay. line relays at that station and also including 5. In a remote control system, an o?ice and a tuned circuit elements rendering each control re station connected by line wires, a line relay at lay at a station selectively responsive to alternat the station, a selective communication channel ing current in the line wires of a frequency dif for controlling the line relay including a source ferent from that to which the other relays at such‘ I of alternating current of controllable frequency station are responsive, and control means at the at the office, said line wires, and tuned circuit ele office for supplying steady current of a selected ments resonant to a particular frequency, manu polarity to the line wires for a brief period and ally operable selecting means at the o?ice includ for supplying two impulses of alternating current ing a relay for establishing said channel and of selected frequencies to the line wires during means for supplying alternating current thereto such period to selectively energize a particular of said frequency to energize the line relay, cir control relay at a selected station. cuit means for maintaining both the office relay 3. In a remote control system, an office and and the station line relay locally energized after a plurality of stations connected by line wires, the manually operable means is released and the a ?rst line relay at each station selectively re 70 delivery of alternating current to said channel is sponsive to current of a distinctive character, a thereby interrupted, a plurality of control relays second line relay at each station connected to the at said station, control channels for selectively line wires over tuned circuit elements to render energizing said control relays by alternating cur such relay selectively responsive to alternating rent from said source, following the release of said current of a ‘particular frequency in said line 75 manually operable selecting means, each such‘ , 5 2,896,134 to a different frequency of ‘current from said source, means responsive to the operation of each channel including a ‘front contact of said line relay and tuned circuit elements rendering each set of selecting contacts for preparing said chan nels for communication between the office and control relay responsive to current of a frequency , different from those to which the line relay or the corresponding station, and for closing a cir cuit for said timing relay, a plurality of sets of the other control relays are responsive, manually operable control means at the o?ice effective manually operable control contacts at the office, when operated to release said oiiice relay, and including one set for each control relay at a sta tion, for controlling the frequency of the current supplied by said‘ source, and means responsive to the operation of each set of control contacts for timing means responsive to the release of said o?ice relay effective to supply successive impulses of alternating current of different frequencies selected by said control means to said control opening the circuit for said timing relay and for rendering said source effective during the release period thereof to supply current from said source to the prepared channels of a frequency to which channels to energize a selected plurality of said . control relays, and to then release said line relay. 6. In a remote control system, an o?ice and a - station ‘connected by line wires, a line relay and a the corresponding control relay is responsive. control relay at the station, selective communi cation channels for controlling said relays each 8. In a remote control system, an office and a plurality of stations connected by line wires, a including a source of alternating current of con trollable frequency at the office, said line wires, and tuned circuit elements resonant to different frequencies, the channel for-the control relay plurality of communication channels including 20 said line wires and a source of alternating current of controllable frequency, a plurality of sets of manually operable selecting contacts at the ofllce, including one set for each station, a‘chain of local holding circuit for thelcontrol relay includ timing relays at the office, a plurality of control ing a back contact of the line relay, manually operable means at the o?ice for establishing said ' . relays at each station, each responsive selectively to a different frequency of current from said channels one at a time for brief periods and for source, means responsive to the operation of each supplying alternating current thereto to which set'of selecting contacts for preparing said chan said relays are responsive, means responsive to nels for communication between the o?ice and the one operation of said'manually operable means corresponding station and for energizing the re for supplying to said channels alternating cur’. lays of said chain, a plurality of sets of manually rents of-both frequenciesto energize the line re operable control contacts at the oilice, including lay and the control relay, and means responsive one set for each control relay at a station,rfc-r to another operation of said manually operable controlling the frequency of the current supplied means for supplying to said channels alternat ing currents of only one frequency to energize the , ,= by said source, and means responsive to the op eration of each set of control contacts for re line relay only and thereby release said control leasing said timing relays one at a time in order, and means effective during the release period of 7. In a remote control system, an office and a said timing relays for supplying current from plurality of stations connected by line wires, a plurality of communication channels including 40 said source to di?erent ones of said prepared channels one at a time to successively energize said line wires and a source. of alternating current a plurality of said control relays by currents of of controllable frequency, a plurality of sets of including a front contact of the line relay; a , relay. ‘ . manually operable selecting contacts at the o?ice, including one set for each station, a slow release timing relay at the office, a plurality of control 45 relays at each station each responsive selectively different frequencies, dependent upon which set of control contacts has been operated. ANDREW J. SORENSEN. '