US2394080A - Remote control system - Google Patents

Description

Feb. 5, 1946. R. M. LAURENSON REMOTE CONTROL -SYSTEM 2 Sheets-Sheet 1 Filed June 10, 1944 I NNMM IN VEN TOR I HobemMLaa ezzwoa. aim

\NNN MN NNBN w w mm H15 ATTORNEY Amwm Feb. 5, 19 46. I I R. M; LAURENSON 2,394,080 I REMOTE CONTROL SYSTEM Filed June 10, 1944 2 She etsShee t 2 IN VEN TOR *{Ifaber/Mlaumnron a Clam H15 ATTORNEY Patented Feb. 5, 1946 UNITED STATES PATENT. owes REMOTE-CONTROL SYSTEM RobertM; Laurenson, Elkhart', Injd; assignor' to The Union Switchand Signal" Company,"Swissvale; Pat, a corporation of Pennsylvania= Application June 10, 1944; Serial N0..-539,.643

I 11 Claims."- (Cl."177 353) My invention relates to remote control systems, and more particularly'to centralized traflic controlsystems for railroads-for the control of rail Way signals and other trafiic-controlling devices from a central point such as a traindispatchers ofllce; and for the indication-of such devices or for reporting-train movements at the control oflice:

One object of'my. invention is theprovision of a-codeisystemfor communication between the control-office and-ax. plurality of field stations employing codes which comprise series of impulses of alternating. currents, the frequency of, which-is in a range suitablefortransmission over existing railroad communication 'circuits withoutinterfering with:v their use for other purposes.

My" invention includes the provision of coding units-comprising chains of counting relays 10-, cated at the oflice and at each station forcount ingthe successive "steps of a code, together with anoperators control board at the oflice having a pluralityoftindividual panels each containing the control levers and. indication lamps for a particular station together with agroup of'individual selecting. and indication. relays 1 and a starting push button bymeansof which the delivery of a :code to such station is manually initiated.

Twov oscillators or generators of high frequency currentsare provided at the office, one'of which serves to select the stations and may be adjusted to deliverdifierent frequencies to which the coding units at different stations are selectively. responsive, while the other oscillator is arranged to deliver .a fixed frequency toHwhich control ap- Daratus at. any station. selected by its assigned frequency is responsive. Eachl station is provided with an. oscillator adapted to deliver either of. twoirequencies, one of. which is fixed at a value to whichsindicationapparatus at the office is responsive, while theother varies from station to stationand serves for station identificationat the office. Each of the codes .usuallyflinvolves three frequenciesand comprisesaseries of impulses of a station selecting frequency whichop crate; countingrelays at a particular station to establish two series of channels sequentially over which impulses of two other frequencies are transmitted for control and indication purposes.

Onefeature of my invention resides in a novel arrangement. of the selecting relays for the dif-l ferent' control panels whereby the different codes are initiated one at a time in order without. inter-v ference- This is. accomplished insuch a manner.

stored for-transmission. The codes are initiated either manually by the operation of starting pushbuttons at the office, or automatically-in response toidentifyingijimpulses, received fro-mthe stations; b-utinieither'casethe selection'of a particu- 1aI'QCOd"fOr1 transmission: is effected by the operationwofia noveli'systemofaselecting relays "located. attheyofiice and-interlocked-locally so as to preventxinterference independently of line conditions:-

Otherobjects, features and purposes of my invention i will be hereinafter pointed out.

I- shall describeoneiorm of apparatus embodyingnmy invention and shall then point out the: novel :features {thereofin claims.

Referring to the accompanying drawings-Figs. 1 and-2 taken together show one form of remote control system embodying my invention, Fig. 1 showing the-officeapparatus for the transmission of codes of four steps each to three or more stations,-together-with the individual control paneliora station No; 2 in its entirety and portions of the control'panels for two other stations-Nos.- 1 and:3-in order'to illustrate the mode of operation of-the circuits forinterlocking the panels. Fig. 2 shows. :the apparatus at a typical 1 field station. Similarapparatus, differing only as-to the frequencieswused for station selection and identificaseveral stationsmay be connected to the line wiresin any. desired order.

, traffic control sy-stem may be advantageously station as long was another. stationJ has a code used I have chosen-,for.illustration a relatively simple application, comprising the control of successivel pairs of. manual'blo ck signals LH and RH;

as shown in 2, located at spaced points along a stretch of railway track. The system as shown is also arranged to indicate at the oifice the positions ofpairs of polar stick control relays LHS and RHSprovided .for the control of the signals,

and .to also report the passage of trains-through short detector track sections T at the signal lo'ca tions. Theoffice panel for each station includes a three-position signallever such as the .lever 2SG, -Fig. 1, opera ble-to a right-hand and a lefthandreverse .position to effect the operation of V the correspondinglsignal control relay RHS Or LHS to its reverse opposition, and to its normal center position to restore these relays manually to their normal positions. h

'Each detector track section T iskprovided with the usual normally energized track circuit having a track relay TR, and eachtrack relay TR controls'a stick repeating 're lay TS, arranged in a well-known manner so that each train movement past a clear signal restores itpto stop and requires cleared.

7 the return of thesignal control relay to normal v by lever operation before the signal can be again To simplify the drawingsI have shown the various circuits as extending only to the terminals of the local sourcesof current, thesebei'ng identified by thereferences B and C, respectively; Re-

. lay TS, for exampla has a pick-up circuit extend-' ing from one terminalB of the localsource of current at the station over the normal contacts dfo f relays LI-IS and Rl-IS; through the Winding ofrelay TS and over front contact a of the track. I relay TR to the other terminal C of the same.

source. When relay LHS or RHS is reversed, the closing or its right-hand contact b completes a'circuit over front contact or e of relay'TS for clearing the corresponding signal LH or RH.

Relay TS is held energized over a stick circuit extending to terminal B over itsown front con;

tact 1 until a train enters the detector section to release relay'IR, whereupon the signal is put .to stop due'to the release of relay TS by relay TR.

i As shown in Fig. 1, a group of indication stick relays TK,LGK and RGK-is provided for each anel, which relays are controlled by code impulses asdetermined by the positions of relays TS',?LHS. and Rl-IS at the corresponding station.

lays are made slow to release by the connection of electronic rectifiers across their terminals, as

shown, and serve both to' count the impulses and p to time them at a suitable :rate. An auxiliary relay 0A serves to initiate the operation of the counting relays and to time the intervals between successive codes. Oscillator OSI is' adjustably arranged to generateany one of a plurality of related frequencieaidentified as fll,

.fl2, H3, etc., by connecting tuning condensers such as CH, C12, CI3, etc. thereto overback "contacts a of different relays SP. Relay OAis normally energized over a circuit extending from terminal B at'front contact of relay ISP over front contacts 1 of all the SP relays in series and over back contact a of relay '04 through relay 0A to terminal CL Ifrelay -2SP, for example, be-

comes released, the circuit for relayOA is opened and prior to its release a circuit is closed from 1 terminal l3 over back contact 1 of relay 2SP, back co'ritactjg of, relay O4 and-front contact, a of relay 0A through relayOI to terminal'C, over which relay OI is picked up to'begin the first code step.

Contact 'e of relay 0! then connects oscillator OSI to theline'wires Y and Z through a suitable band pass filter BP and transmitting amplifier TA'I to impress current of the frequency generated thereby on theline wires Y and Z; Since I condenser Cl 2 is connected to oscillator OSI over back'contact e of relay ZSP, this current is of the frequency in in the case described. Relay 0A releases after a suitable period, opening the circuit for relay 0! and closing a circuit at its back contact a including front contact a of relay 0| These indication relays control a group of signal indication lamps LE, NE and RE associated with trols 'a normally energized starting relay such as Y the relayZST, by means of which a code may be manually initiated for delivery to the corresponding station. The selec tion of a particular panel is governed by groups of serially inter;- lecked relays shown in the upper right-hand por-' tion of Fig. 1. Each such group includes a se lector relay such as the relay 28, which is of the stickpolar type and may be operated locally to reverse either by releasing the associated startingrelay or by thetransmission of a station identifying impulse of a distinctive frequency from the associated station,

Eachselector relay S controls a normally energized repeating relay, such as the 'relay ZSP, therelease of which is adapted to efi'ect the energization of a delivery relay such as the relay 2D, by means of which the corresponding signal lever and group of indication relays are selectivel y associated with the line circuit, one panel at a time. 7 i

[Althoughthe system may readily be modified toernploycodes having any desired number of steps asshowmit is arranged to use codes having four steps only, since these are sufficient to illustrate my invention. The code steps are formed by the transmission of a series of stepping impulsesggenerated by an oscillator OSI and de,

livered by steppingmeans comprising a chain of counting relays OI to 04, inclusive, These reover which relay O2 is picked up; to begin the second code step. Contact e of relay 02 opens anddisconnects the oscillator OSI from the line to terminate the'transmission of the impulse of frequency 112. Relay of then releases in turn, opening the circuit'for relay O2 and completing one for relay O3 over back contact a of relay OI and'front contactdof relay 02, thereby causing relay O3 to pick up. The closing of front contact e of relay 03 causes oscillator OSI to deliver current of frequ ency fl2 to the'li-ne again, oorre- 7 sponding to the third code step. Relay O2 in its turn releases to pick up relay O4,'which terminates the transmission of current of frequency H2, thereby beginning thefourth step. The code steps thus comprise alternate periods of energization and deenergization of the. line circuit by current of a selected frequency; During these four steps four control channels may be sequentiallyestablished over "contacts b of relays O! to O hfor the transmission of control impulses of a given frequency fill, and at the same time, four indication I channels are established over contacts c and d of these relays over which the indication relays are controlled in response to received impulses of a second given frequency f2ll.

V In the foregoingit has been assumed that the repeating relay 2SP is the only one released. The delivery relay 2D in this ,case is energized over back contact gof relay ZSP, and'if lever 28G is inits normal position as shown, a circuit is closed on thefirst step of the code from terminal B at contact b ofrelay 2D and the center contact of lever- ZSGover contact b of relay OI through the primary winding of an impulse transformer VI to terminal 0. A transmitter relay TI of the biased polar type, is connected across the secondary winding of transformer VI and operates in response to thecurrent'induced theretransmission of the preceding code will beccr V rectly indicated at the ofiice. even though the v change occurs after the correspondingcode step is transmitted.

"Having thus described the "different components of the system of my invention, I shall now explain its operation under different assumed conditions." V V I I shall first'assume thatwith the apparatu in its normal condition as shown, the operator wishes to clear signal 2HR at station No.2 and :released, a circuit is completed from thelmiddle.

"terminal of the ofiice source of current through the lower winding of relay 28 from right to left and over contacts b of relay 2ST and button :ZSTB to the negative terminal 0 of the source,

thereby reversing relay 28. Under the condi- 'tionsassumedthe indication relays RGK; and iLGK are both energized over stick circuits extending to terminal B over the normal contact 1) of, relay 2S. and the stop indication lamp NE fislighted over the front contacts b of relays RGK :andfLGK and backcontact a of relay '2D." t :reversal of relays 2S therefore releases'relays lRGK and LGK and extinguishes lampN E, the panel lights remaining dark until new indications :are received; The opening of the normal con- :tact a of relay 2S deenergizes relay ZSP, provided :all similar relaysfat theright, such as relay 3SP, :are picked up. Relay ZSP releases 'after albrief 'period and connects terminal B at its back conztact b tothe front contacts'a and b of relay I SP and thereby prepares circuits "by which the re.- ilease of any similar relay at the left of relay 28-1? :is prevented in the event the corresponding sej lector relay such as the relay ls becomes 're versed. It follows that with relay ZSP or 3SP released, relay ISP is maintained energized rezgardless of the position of relay IS. Acircuit is now closed from terminal B at front contact 9 of relay lSP over back contact g of relay 2SP through the delivery relay 2D to terminal C, and

relay 2D picks up, all other relays D being held released. A tuning circuit is now completed for oscillator 08! over front contact e of relay ISP and back contact e of relay ZSP through condenser Cl2,oth'er similar condensers such as C and CB being disconnected from oscillator OSI. The dropping of contact .1 of relay ZSP deenergizes relay 0A and energizes relay 0], whereupon relay OI picks up closing its contact e to'im-' press an impulse of frequency fl2 upon the lin wires Y and Z as hereinb'eforeexplained. v

When relay Oi picks up, and prior to-the releaseof relay 0A, the starting relay 2ST is :reenergized over a circuit extending from terminal B at contact f of relay 0A over contact J of relay 01, front contact 0 of relay I SP, back contact 0 of relay ESP through relay 2ST to terminalC at contact a of the starting button ZSTB,

relay IST completing a stick circuit" by closing its oWn front contact a. a '1 At the selected station relay R! of Fig.2 picks gara e pleting a stick circuit. at its own front: contact (L Relay LB maintains relay l energized ;over

'a stick circuit'includingfront contacts a of relay TS to energize transformer V3 on thisstep,

consequently relay T3 operates to deliver an impulse of frequency I20 to the line'to which the oflice line relay R3 of Fig. 1 responds. Relay R3 completes a circuit from terminal'B at its'front contact cover contacts c of relays 0A and 0!, contact -c of relay 2D through, the upper winding of relay IK to terminal c. Relay which is of the polar stick type, is thereby energized momentarily in'th'e normal directionas shown.

Relay OA now releases; deenergizing relayOl andcausing relay, O2 to pick up. Relay O2-by opening its back contact e terminates the first impulse Of-frequency H2. 'Thestation line relayRl of Fig.2 therefore releases, com leting a circuit at its back contact a over front contacts c of relay LB and contactd of. relay l to pick up relay 2, and opening the stick circuit for relay I, which relay therefore releasesjat the beginning of the second step, whereas the corresponding oflice relay Oi serves as a timing relay and its release marks the end of thesecond step. Referring now to Fig. 1, when relayQl releases relay 02 becomes deenergized and relay 03 picks up to begin the third step, andby closing its front contact e impresses a second impulse of frequency fl 2 upon the line. .7

At the selected station, relay RI, Fig. 2, picks up 'to energize relay 3 and to hold relay LB picked up, 1relay2 releasing at the beginning of the third'step, .The closin of front contact b of relay 03, Fig. l, completes a circuit'for transformer VI over the right-hand contact of lever 28G extending to terminal B at contact I) of relay 2D, causing relay '1! 'to supply a control R2 and contact 0 of relay 3 through the lower" up in response to the'impulse of frequency ji2 Winding of relay RHS to terminal C. to operate relay RHS to reverse. The'closing of front contact d of relay 3 at the selected station completes: a circuit over contact 11 of relay LHS to energize: transformer V3 causing relay T3 to supply an.

impulse of frequency 120 to the line thereby en-- ergizing relay R3 in Fig. 1 'to complete a circuit from terminal B at its contact a over back con-' tacts c and d of relays 0A and OI, front con tact .d of relay 02, contact c.0f relay 03, contact: eof relay 2D through relay LGK to terminal C. Relay aLGK therefore picks up, and completes a temporary stick circuit at its contact a over contact 9 ofrelay. 2D extending to'terminal B over back contacts d ofrelays O4 and 0A in multiple. 1 Y

When relay O2 releases, relay 03 becomes deenergized andvrelay O4 picksv up to begin the fourth step opening its contact e to terminate the impulse of frequency fl2. Relay RI, Fig. 2, releases to pick up relay ,4, releasing relay 3 and deenergizing relay LB. In the code being described the control and indication channels re main open on this step. When re1ayO3, Fig. 1,

releases to terminate the step. circuits are closed over front contact f ofrelay 04-, front contact d of relay ISP, back contact d of relay ZSP, front contact b of relay 2ST through the lower winding of relay 28 to terminal 0, restorin relay 28 to normal. The closing of the lefthand contacts a and b of relay 2S reenergizes relay ZSP and establishes the normal stick circuit for relay ZLGK. Relay 2SP picks up and by opening its back contact :7 releases relay 'ZD'lJO disconnect lever ZSG and the associated indication relays from the counting relaysand to complete a circuit at contact a of relay 2D to light lamp 2RE. 7

Relay 04 now releases and the dropping of its contact a shiftsthe circuit for relay GA to the branch including the front contacts 1 of the relays SP. If all of these relays are picked up, relay A remains energized and the oifice apparatus remains in its normal condition as shown until the nextcode is initiated. At the-selected station relays LB and 4 of Fig. 2 release in turn, completing the restoration of the system to its normal at rest'condition. i a

if at this time one of therelays SP of Fig. 1 is in its released position, relay OA becomes -.deenergized when relay (34 releases, and relay OI becomes energized over back contact 9 of relay O4 and front contact a of relay 0A to deliver the first impulse of a second code to the line Wires Y'and Z. If this is delivered to a different station, the successive operations of relays RI, LB and I of Fig. -2 will be similar to those already described, but if it is delivered to the same station as the preceding code, relay R! may pick up before relay LB releases, in which case relay 4 will be in its energized position and relay I will pick up overthe front contact b of relay 4.

I shall next assume thata train moving toward the right passes signalRI-I of Fig. 2 at clear releasing relay TR, which relay 'in' turn releases relay TS. Relay TS releases relay ST,thereby energizing relay STP and causing relay T3 to deliver an impulse of frequency I22 to the line to selectively reverse relay 28 .of Fig. 1. Relay 2S releases relay ISP to initiate the transmis-' sion of a code similar to the one already described, except that the starting relay ZS'I'has not been released, and the indication impulse of frequency f20 by which relay R3 is operated is-delivered on the second step instead of on the first clue to the fact that relay TS is now in its released "position. This impulse is supplied to the lower winding of relay TK by relay -R;3 causing relay TK to reverse and lamp TKE to becomelighted. The signal indication lamps are extinguished for the duration of the codeasin the preceding example.

I shall next assume that the operator restores lev'e'r ZSG tonormal and operates buttonZS'IB to initiate a code in which an impulse of frequency flu is supplied on the first step restoring relay RI-IS to normal. The indication relays 'LGK and RGK in this case are picked up by the impulses received on the :third and fourth steps, lighting'lam'p NE. When the train vacates'the detector section to pickup-relay TR, Fig. 2,:relay TS "picks up over the normal contacts a of relays LHSand RHS and initiatesa code including an indication impulse on the first step which restores relay TK of Fig. '1 to normal, extinguishing lamp TKE.

The operations involved in the controlof signal LI-I are similar to those for signal RH and a description 'of these is deemed unnecessary.

ventlng interference, ithas already been pointed out that a station can deliver its identifying impulse of a frequency in the band j2I-f23 either when the system is at rest or when a code is being delivered to another station. If relay ST of 2 at any station becomes released while a code is being received at that station, relays ST and STP are held released as long as relay LB remains picked up so that the station identifying impulse is stored for delivery following the release of relay LB at the end of the code.

The oflice starting buttons STB, Fig. 1, are free to be operated at any time. The release of any of the selector repeating relays such as relay 2SP prevents the release of those at the left, but any relay SP at the right of one which is released is free to release while the system is in opera tion. This howevercauses no interference because the release of any relay SP interrupts the circuits controlled by the similar relays at its right.

Assuming for example that relays IS and 3S reverse during the transmission of a code initiated in response to the release of relay ZSP by relay 2S.as hereinbefore described. Relay 3SP releases but relay ISP is held energized over the reverse contact a of relay IS, its own front contact a and back contact b of relay 2SP. When relay ZSP picks up following the restoration of relay 25 to normal at the end ofthe code, relay lSPis maintained energized over front contact I) of relay ISP and back contact 22 of relay 38F, and relay 3D becomes energized to deliver the second code. If relay 2S reverses again, relay ZSP is held energized over a branch .of the circuit by which relay ISP is held energized and these relays will release together at the. end of the second code. Relay ISP then completesa circuit for relayflD and opens the circuit for relay ZD. It follows that the third code will be delivered by relay ID after which relay ISP is reenergized so that the fourth code will be deliVeredbyreIayZD. It will be clear that if relay 3SP releases :again. during the transmission of the third or fourth codes, the fifth code will bedelivered by relay 3D. It will beseen,'therefore, that .inthe event that changes in traflic conditionsoccur so frequently as to cause continuous operation of the system, the codes are transmitted in a fixed order and a second code cannot be transmitted to anystation as long as 'oneis stored for-transmission to another station and the delivery relays D operate one at a time in'sequence through repeated cycles.

The system operatessimilarly in respect to the order of transmission of codes initiated by operation of'the ofiice starting buttons, with one excaption. It'may happen that a starting button such asZSTB is operated while a code is being deliveredto the corresponding station thereby-releasing relay 2ST, and preventing the restoranon-oi relay 28 to normal'when relay04 picks up on the 'last step and causing the indication relays LGK and RGK to be released by the opening of contactd of relay Oh when relay 0A picks up on .the last step. Rela 28? remains released, holding relay 2D energized and relay OA becomes deenergized when relay O4 releases at the end of the code,.thereby causing the countingrelays to operatethrough a second cycle to deliver a secondc'ode from the same panel. This insures that if lever 28G and button "2ST-B are operated during transmission of a code from the correspondingpanel, a ,second code includingcontrol impulses corresponding to the last operated posi- Although ,I have herein shown and described only one form of remote control system embodying my invention, it is understood that various changes and modifications may be madetherein 7 within the scope of the appended claims without departing fromthe spirit andscope of my invention.

Having thus described my invention, what I claim is: v V

1. In a remote control system, an office and a plurality of stations connected by line wires, a

plurality ofchains of counting relays including one at the ofice and one at each station the relays of each chain being operable one at atime in a given order, a series of control relays at each station, a plurality of manually operable lever contacts at the ofiice including one for each controlrelay, a pluralityiof station selecting relays at the ofiice including one foreach station, means including contacts of corresponding counting relays at the oiiice and at a selected station for establishing a series of control channels each such channel including said line wires and selective circuit elements renderingthe channel effective for the transmission of alternating current of a given frequency only, means controlled by each tive frequency over'said line wires, means-selectively controlled by the impulses of said distinctive frequency for operating thecounting relays at the selected station only to sequentially estab lish said control channels, and means governed byosaid lever contacts for supplying alternating current of saidgivenfrequency to selected ones of said channels to operate the corresponding control relays. 4 r

2. In a remote control system, an oiiice and a plurality of stations connected by line wires, a

plurality of chains of counting relays including i one at the office and one at each station the relays of ,each chain being operable one ata time station selecting relay for initiating the operation 1- of the ofiice counting relays and for transmit: ting impulses of alternating current'of a distincsaid line wires, means ateach station for at in a given order, a series of control relays at each station, a pluralit of manually operable lever contacts at the office including one for each con- 'trol relay, a plurality of station selecting relays at the office includingone for each station, means including contacts of corresponding countingre-' lays at the office and at a selected station for establishing a series of control channels each such channel including said line wires and selective circuitelementsrendering the channel eifective for the transmission of alternating current of a given "frequency only; means controlled by each station selecting rela for initiating the operation of the oflice counting relays, means controlled'by the ofiice counting relays for transmit- .ting impulses over said line wires of alternating current of a distinctive frequency characteristic of --a particular selector relay, means selectively I controlled by the impulses-of said distinctive frequency foroperating the-counting relays at the corresponding station onlyto sequentially establish said control channels, means governed by said levercontacts for supplying alternating current of said given frequency to selected ones 'of said channels to operate the corresponding 'control relays, means rendering said selector'relays eifective only one ata time to determine the fre-' quency of the impulses for operating the station counting relays, and means for operating each selector relay.

7 2,394,030 tion of lever ZSG willbe transmitted in its en 3.' In a remote controlsystem,an ofiice and a plurality of stations connected by line wires, a

plurality of chains of counting relays includin one at the ofiice and one at each station the relays of each chain being operable one at a time in a given order, a plurality of selector relays at the office including one for each station, a series of indication relays at the office for each station;

means including contacts of each selector relay for establishing a series of indication channels office counting relays and for transmitting impulses of alternating current over said line wires of a diiferent frequency characteristic of a particular selector relay, means selectively controlled by the impulses of said diiferent frequency for operating the counting relays at the correspond ing station only to sequentially establish said'indication channels, means at such station forsupplying alternating current of said given frequency to selected ones of said channels to operate the corresponding indication relays, means rendering said selector relays effective only one at a time to determine the frequency of the impulses 'which operate the station counting relays, and

means at each station for at times Supplying'an impulse of alternating current of a distinctive station identifying frequency to the line wires to operate the corresponding selector relay, V ,4. In a remote control system, an office anda plurality of stations connected by lin wires, a series of selector relays at the oflice including one for each station each selectively responsive to impulses of a different frequency transmitted over times transmitting animpulse over the line wires of the frequency to which the corresponding selector relay is responsive to selectively operate such relay, step-by-step means set intooperation when any selector relay is operated for establishing a series of indication channels sequentially between the Office and the corresponding station only, means at each station for transmitting indication impulses of a distinctive frequency over said channels when established, a plurality of groups of indication relays at the ofiiceg'and means controlled by the operated selector relay for selecting a particular group of indication relays for'operation in accordance with that series of said indication impulses which are transmitted from the corresponding station.

5. In a remote control system, an oflice and a plurality of stations connected by line wires, a

series of groups of relays at the office including one group for each station each group including a selector relay of the stick polar type, arepeate ing relay and a delivery relay, an energizing cirlcuit' for each repeating relay including a nor mallyclosed contact of the associated selector,

relay, a stick circuit for the repeating relay of each group except thelast of the series closed upon the reversal of. the associated selectorrelay provided the repeating relay of any succeeding group is released, an energizing circuit for each delivery relay including a back contact of the associated repeating relay the circuit for the delivery relay of each group except the first also aseacse including front'contacts of the repeating relays of the preceding groups of the series-and means set into operation upon the release of any one of said repeating relays for establishing aseries of channels selected by the associated delivery relay for communicating between the office=and the correspondingstation over said line Wires.

6. In a remote control system, anoflice and a plurality of stations connected by line wires, 2. series'of groups of relays at th oflice including one group for each station each groupincluding aselector relay of'the stick polar type, a repeating relay and -a delivery relay, an energizing circuit for each repeating relay including a normally :closed contact of the associated selector relay, a stick circuit for the repeating relay of each group except :the last of the series closed uponithe reversal of the associated S81E91 tor relay .provided the repeating relay of any succeeding group is released, an energizing circuit for each delivery relay including a back contact of the associated repeating relay the circuit for the delivery relay of each group except the first also including front contacts of the repeating relays of the preceding groups of the series, starting means for each group for reversing the selector relay of such group, means set into operation upon the release of the repeating relay of any group by its selector relay for transmitting a distinctive series of impulses over said line wires to the corresponding station, means controlled by said impulses for establishing communication channels between the ofiice and such station over contacts of the operated delivery relay, and means for restoring each selector relay to normal in response to the transmission of a predetermined number of. impulses.

'7. In a remote control system, an oflice and a plurality of stations connected by line wires, a series of groups of relays at the office including one group for each station each group including a selector relay of the stick polar type, a repeating relay and a delivery relay, an energizing circuit for each repeating relay including a normally closed contact of the associated selector relay, a stick circuit for the repeating relay of each group except the last of the series closed upon the reversal of the associated selector retions at such station for operating :the selector lay provided the repeating relay of any succeeding group is released, an energizing circuit for each delivery relay including a back contact of the associated repeating relay the circuit for the delivery relay of each group except the first also including front contacts of the repeating relays of the preceding groups of the series, starting means at each station adapted to transmit a station identifying impulse of distinctive character over said line wires to reverse the selector relay of the corresponding group, means set into operation upon the release of any repeating relay for transmitting a distinctive series of impulses over said line wires to the corresponding station, means controlled by said impulses for establishing communication channels between the ofiice and such station over contacts of the operated delivery relay, and indication means at the ofiice responsive to impulses transmitted over said channels. I

8. In a remote control system, an office and a plurality of stations connected by line wires, a series of selector relays at the ofiice each responsive to impulses of a different frequency transmitted over said line wires there being one selector relay for each station, starting means at each station responsive to a change in condirelay therefor by transmitting a station identityin impulse .over said line wires of the frequency to which the selector relayfor such station is selectively responsive, step-by-step means set into operation :when one or more, of said selector relays is .operated'forestablishing a series of indication channels sequentially between the ofiice and the corresponding stations only one station at a time, means ateach station for transmitting .a series of indication impulses over said channels when established, a plurality of groups of indication relays at the office, means controlled by each operated selector relay for selecting a particular group of indication relays for-operation in accordance with the impulses transmitted" from. the corresponding station, and means for restoring each, operated selector relayto its normal position following the transmission of the last impulse of such series.

'9. Ina remote control system, an oifice and a plurality of stations connected by line wires, a series of selector relays at the ofiice each responsive to impulses of a difierent frequency transmitted over said line wires there being one selector relay for each station, starting means at each station responsive to a change in conditions at such station for operating the selector relay therefor by transmitting a station identifying impulse over said line wires of the frequency to which the selector relay for such station is selectively responsive, step-by-step means set into operation when one or more of said selector relays is operated for establishing a series of,indication channels sequentially between the ofiice and the corresponding stations only one station at a time, means at each station for transmitting a series of indication impulses over said channels when established, a plurality of groups of indication relays at the ofiice, means controlled by each operated selector relay for selecting a particular group of indication relays for operation in accordance with the impulses transmitted from the corresponding station, means for restoring each operated selector .relay to its normal position following the transmission of the last impulse of such series, and means at each station for delaying the transmission of a second station identifying impulse over said line wires due to a change in conditions at such station occurring during the transmission of indication impulses from such station until the selector relay responsive thereto has been restored to its normal position.

10. In a remote control system, an office and a plurality of stations connected by line wires, a seriesof selector relays at the office each responsive to impulses of a different frequency transmitted over said line wires there being one selector relay for each station, starting means at each station responsive to a change in conditions at such station for operating the selector relay therefor by transmitting a station identifying impulse over said line wires of the frequency to which the selector relay for such station is selectively responsive, a series of repeating relays at the office including one for each selector relay, step-by-step means controlled by each repeating relay when actuated for establishing a series of communication channels between the office and the corresponding station only over said line wires, means for actuating each repeating relay in response to the operation of its selector relay arranged to render said repeating relays effective only one at a time in a fixed order when a plurality of said selector relays are'operated, means for transmitting impulses between the office and the selected station over said communication channels when established, and means for registering such impulses.

11. In a remote control system, an office and a plurality of stations connected by line wires, stepping means at the ofiice and at each station for establishin two sets of communication channels between the office and stations including said line -wires,' means comprising selective circuit elements tuned to different frequencies at the dif- V ferent stations for rendering the stepping means at each station responsive only one at a time to impulses of a distinctive frequency received over I 'said line wires, a 'group of control relays at each 20 ated selector relay lected station responsive to impulses of agiven frequency transmitted over the one set of channels and for rendering a selected group of indl-' cation'relays responsive to impulses of a second given frequency transmitted over the other set of channels, a selector relay at the ofice for each station, means controlled by each selector relay when operated for operating the'office stepping means to deliver two' series of impulses of different frequencies to the line wires including one series efiective to operate the stepping means at the corresponding station only to establish said channels and another series efiective' to operate the control relays at such station over the chan-' nels thereby established, and means responsive to the operation of said station stepping means for simultaneously transmitting a series of impulses of said second given frequency to operate the indication relays associated with the operover said other set of channels. ROBERT M. LAURENSON;

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