US2394971A

US2394971A - Remote control system

Info

Publication number: US2394971A
Application number: US553395A
Authority: US
Inventors: George W Baughman
Original assignee: Union Switch and Signal Inc
Current assignee: Hitachi Rail STS USA Inc
Priority date: 1944-09-09
Filing date: 1944-09-09
Publication date: 1946-02-19
Anticipated expiration: 1963-02-19

Description

'FeB. 19,1946.

G. W. BAUGHMAN REMOTE CONTROL SYSTEM Filed Sept. 9, 1944 2 Sheets-Sheet; 1

bu? Q IN VEN TOR Georgell/flazlglzzzzan HIS ATTORNEY Patented Feb. 19, 1946 UNITED STATES PATENT OFFICE 21394371 v v I George W; Bau 'hman, swissyale, Pa, as i'g ior to The Union- Switch a Signal Company", Swissg 7 Claims.

- My invention relates to remote control systems, and more particularly tothe line or communica tion circuits for such systems.

My invention is'an improvement upon that disclcsed in Letters; Patent of the United States No. 2,350,668, issued June 6, 1944,- to George W. Baughman and? Norman F. Agnew, for Remote control systems; and. upon that disclosed in an application for Letters Patent or the United States, Serial $10,552,504, filed September 2, 1944, by Lloyd- V. Lewis.-

one object at invention is the rovision of *meansror interposiiiga carrier current or radio channel in the line connectingthe o'filce' and sta-' tionsin a remote control system, using only one either line to the ofice over the same radio channel.

Similar reference characters refer to similar parts in each of the views.

It is to be understood that the remotecontrol system employed herein is of the time code frequency channel for the transmission of codes in two directions Another object of my invention is the provision of means for transmitting carrier current codes in either direction between two stations, in which a sensitive receiver at each station, responsive to highly attenuated signals received from the other station; is arranged so that it does not re;- spond to signals transmitted from the same sta-' tion regardless of their strength or frequency, together with means for establishing one waytransmission in the event codes are initiated at both stations at the same time. Y I I shall describe two forms of apparatus embody ing y invention and shail then point out the nove'l feat'ures thereof in claims.

Referring to the accompanying drawings, Figs, 1A and 1B, taken together, show one form of remote control system embodying my invention in which codesignais are transmitted by radio in two directions between the control oflioe, shown inFi'g'. 1A, and a repeaterstatiom'shown in Fig. 1E, and connected to line wires Y'I-Zl over which the codes are transmitted between" the repeater stations and a plurality of field stations, of which one is shown. V

Fig. 2A shows a modification of Fig. 1A in which the apparatus for repeating the codes which originate at the office to the stations as radio signals and for repeating codes received as radio signals to the oiiice is contained in a first repeater station located at a distance from the office and 7 connected thereto by the'line wires Y-Z.

, Fig. 2B shows a modification of Fig; 1B in which a repeater similar to that of Fig. 1A is arranged to repeat the codes received from theoifice as radio signals intoa second line Y2Z2 as well as into line iii- 21, and is also adapted to repeat indication codes received from field stations on type, employing coding units CU at the oflice and at each field station for transmitting and receiving the codes such as is shown in Letters Patent of the United States No; 2,229,249, issued January 21*, 1941 to Lloyd VaLewis, for Remote control systems; but with the line circuits arranged as shown in Patent No; 2,350,668, hereinbefore re* ferred to. As shown in Fig.- 1B the line relay R at each station is of the biased polar type and is normally energized over the line wires Yl--;Zl by current from a line battery BI The control codes originating at the o-ffice are transmitted over this line by periodically interrupting the battery current in the same manner as in Patent No. 2,229,249, but the indication codes originating at the stations are transmitted in a different man ner, namely, by periodically connecting the line wires together through a low impedance comprising the filter coils L]? at the transmitting station, so as to vary the current delivered by battery Bl inaccordance'with the code. These codes of current-variations are receivedat the repeater station by a polar line relay IR connected to the line through-altransformer 40 and thereby rendered responsive to the linecurrent variations. Relay iR, is of the magnetic stick type arranged to be held in its last operated position when deenergizedand normall occupies the position in which its left-hand contacts are closed, as shown.

The repeater station apparatus as shown in Fig; 13 includes a pole changer relay IPC by which the polarity of the current supplied to the line is reversed during the transmission of an indication code, together with a group of slow release relays LA, LB and LC, a stick relay Z, and carrier current transmitting and receiving relays ITC and 1GB; in addition, an electronic oscillator OSG'is provided for generating alternating cur-- rent of a suitable carrier frequency which is passed through anam plifier and delivered over the tront contacts ofrelay ITC to a radio antenna Al. Belay ITQ repeats the code operation of relay IR. and delivers the indication codes to antenna Al for retransmission as radio signals. Relay, ITC} normally occupies a released position, as shown, in which antenna Al is connected over its back contact is through an amplifier to relay TCR; which relay is responsive to codes of radio signals received'from the office, and by the operation of its contact a retransmits them over line YI--ZI to the field stations.

The coding apparatus at each field station comprises a master relay M, which when energized places the station apparatus in the transmitting condition, a transmitter relay T which is operated periodically when relay M is energized, to deliver the indication code. to the line, aline relay R of the biased polar type responsive to the codes delivered to the line relay ICR and also to those delivered by the associated relay T, and a coding unit CU comprising selecting apparatus for decoding the received codes and which also governs the operation of the associated relay T.

Controlled by the coding unit, but shown sepa The apparatus at the control office, Fig. 1A, is

generally similar to that at the stations, comprising -a master relay-OM, a transmitter relay OT, and a receiving relay OR governing a coding unit CU. Certain of the coding unit relays are shown separately in Fig. 1A, comprising the relays OLI, L2, OLB, OLBP, OI5, PC and PCP, all of which function like the similarly designated relays of Patent No. 2,350,668. In addition, an electronic oscillator 050 and an amplifier AMP are provided for delivering carrier current coded by the operation of the contact b of a relay TC, to a radio antenna A, relay TC repeating'the code operation of the office transmitter relay OT. Relay TC normally stands released, and then antenna A is connected over its back contact b through an amplifier to the receiving relay OR, which relay is thus rendered responsive to the indication codes originating at the stations. An auxiliary relay TS is also provided, by which relay OR is controlled on the'first step of an indication code as hereinafter explained. As pointed outin Patent No. 2,229,249, each code comprises a series of steps, usually sixteen in number, each step being relatively long or short to provide code character. The first step oi each'control code transmitted from the ofiice is a long step, and the code is thereby rendered distinguishable from indication codes originating at the field stations in each of which the first step is relatively short. I

In the control codes delivered by relay ICR, since the line is normally closed, the odd-numbered steps correspond to the line open, and the even-numbered steps to the line closed condition. On the other hand, the carrier current circuits are normally open, and the codes are opposite in phase, current being supplied to antennas A and Al on the odd-numbered steps and not on the even-numbered steps. In the indication codes delivered to the line circuit by relay T, the oddnumbered steps represent an increase in the line current above normal, and the even-numbered steps a return to the normal value of the line current.

I, shall now describe the operation of the apparatus of Figs. 1A and 1B, assuming first that relay OM becomes energized to initiate the transmission of a controlcode. The closing of front contact e of relay OM connects the transmitter relay OT to the coding unit to cause relay OT to operate periodically in accordance with the code. When relay OT is energized, its repeating relay TC becomes energized over a circuit extending from one terminal B of a suitable local source of current over contact I) of relay OT through relay TC to the other terminal C of the same source, and relay TC delivers the code as carrier current impulses of the frequency generated by oscillator 030 to antenna A. Relay OT also completes a circuit from terminal B at its front contact f over contact h of relay OM through the lower Winding of relay OR to terminal C, so that relay OR is operated locally in accordance with the code, energizingthe timing relays OLI, 0L2, OLB and OLBR in the usual manner. Relay PC is not operated, its circuit being open at contact 9' of relay OM, and consequently relays PCP and TS are not operated.

The radio signals transmitted from antenna A are received over antenna AI to cause relay ICR to respond and to retransmit the code by the operation of its contact a to line YIZI, so that the line relay R at each station responds in accordance with the code generated by the ofiice transmitter relay OT. Each time relay ICR operatesit completes a circuit fromterminal B of the local source of current at its left-hand contact b through relay LB to terminal C. Relay LB picks up in response to the first operation of relay ICE and is held picked up by intermittent energization until the code is completed. Relay LA is steadily energized over the normal contact b of relay IR, and as soon'as relay LB picks up it completes a circuit from terminal B at a contact a of relay LA over contact ,I of relay LB through relay LC to terminal C so that relay LC picks up and is held energized until the code is completed. I

Since relay IR is operable to reverse in response to an increase in line current, the effect of the opening of the line by the first operation of contact a of relay ICR isto tend to operate relay iR to the left to the position it already 7 occupies.,, Whe'n relay LB picks, up, its contact d shunts the upper winding of relay IR connected to transformer iii and contact b of relay LB completes a ,circuit from the middle terminal O of the local source through the lower winding of relay IR over back contact J of relay IPC to terminal C at contact b of relay ILB, whereby relay IR is held in its normal position until the transmission of the code by relay ICR is completed.

Assumin neXtthat a code is initiated by the energization of a station relayM when the system is at rest with relay OM released. Contact 7' and k of relay M reverse the connections to relay R and contact is of relayM also completes a connection from line YI over contact d of relay LB? and contact b of relay E to line ,ZI. Contact e of relay M connects relay T to the coding unit and relay IT picks up and releases periodically in accordance with the code, the first step of which is relatively short and is terminated by the release of relay T following the energization of relay LBP, the latter relay being controlled like relay OLBP shown in Fig. 1A. After relay LBP picks up the line wires YIZI are connected together over contact b of relay T and the circuit for' relay R which when relay M is energized includes back contact b of relay T, is now open. When relay T releases, relay R pick up only if the line current is of the reverse polarity with line ZI positive.

At the repeater station the initial increase asoaa'zr i11 current. due tax the operation of ME causes; relay; IR: toare'verseg. completing a fimmterminalBi oyer its'z'reverse contact a and back: oontaotl am: relay EB throughrelayJiTC t0fiml1limI ,LSth3t relay l-fllcihecome energized supply current from; oscillator QSE: to: antenna Alla; At the same;.tirae a.eimmiliv is closed from terminal; E at; the righlthamfli contact; I): of. relay: l-CB: over the;- reyerse. contact a; ct relay and frorilzfcorrtactb oinelay LAL through relay [PC to terminal) G1;v and reIay IPG pickstup; The operation of the. contaots b audio; of relay LPG reverses the Itne:- polarity as: required; tor the continued operation of relay R at 'the trans-- station and: at the stametimereleasesrelay Rat ea'ehother statiom at hasnot-heen operatedi RelayLB now pibltsup oven the circuit from terminal B atthe reverse contact 0" or relay DR; and contact e of relay iPCt'throug-h relay-EB; to terminal and relay LG picks h m-over contact of relay LLB- RelaylR is held reversed during the reversal of the line polarity-by relay l'P-G because its" upper wind ing is temporarily shuntedover front contact 0' of relay and.- backcontacts 0 of relays LB and EC, and its lowenwindin-g istemporarily energized in a direction to hold it reversed over the circei-t extending from terminal B at hack contact a: of relay orLC over front" Contact 1" oi?- rel'ay FPC through the lowerwinding of relay IRi to -terminal O: v

The radio impulse transmitted" from antenna at when relayl'lC is energized is received at the; office" over antenna and operates relay OR torreverse; thereby energizing relays 012.15,. 0E2, OL-Bf and OLBP" in. the: usual manner; and completing; a circuit temporarily: from terminal B at the. reverse contact a. of: relay OR over back. contacts 1" ofrelay 013BP T of relay 0M, and 'e. oi relay-01:6 through relay PC to. terminal C; so that relay PC picks. up establishing a stick circuit at it'sfown front. contact a when. relay OIiBl? picks, up. Relay. OR also completes a. circuit temporarily from terminal. B at its. reverse. contact woven contacts 9; of relays. BC, Ofif and OIi-BP throughrelay TS; to terminal. C; R'elfay' TS? picks up. and, completes; acircuit; from. terminal 3 at its front; contact a. over back. con.- tact. 71 qt relay OMthroixgliJthe, lower; wihdi'ng' of relay OR to terminal-0.. The operation of relay TS is timed to correspond. with that of! the. station. transmitter relay T and relay OR is held; reversed; by relay. TS for they same. length. of. time on. the, first step. of. an indication. code. as; it it. were. controlled: directly by relay- '1; and. so. operates its. coding unit CU properly, even. though the initial. radio; impulse received is of; relatiyely brief durationr r This, arrangement. is. provided-(for. the: reason that the first code step as transmitted; by. the: repeater station. is madesomewhat shorter; than the, first step delivered by relay,- T, being terminatedhy thereleaseofi relay IIlCwhen: relay; LB picks upto open its; conttmte.v It follows that whenv relay ill.- releases;-=to; begin the. second.- step, of-. the? code relay- ICE. is already connected to antenna. Ala so: as. to responsive to. the operation of the oflice relay TG: and remains: releasedwnly if." the oflice: apparatus isiin contdit-iom to receivezthei code,.tha-t i'szto say; only: if; relay; QlWhas: not..boen,\ opextolled;. Iii relay; remains; releaseds relay L'R: is:= operated tos'normah by the: releasez'oi .rei'ay 12;. theldirec-i tional relay Z. Tupi over circuit. from:

- temnimilz B: at the: right-hand contact 2;;- ofi relay l CR; thesnor mal contact at of relay tB contact a of. relay. liPCg. contact d: or. relay LG. through 2i; tmterminak. Relay Z by ciosinzg its front. contact b: conditions LTZC to repeat the code: received. from time: field". station. as. a: co.d"'e.-.o:f-a radio; impulses to: which: relay-0a is responsive;

Theroflice: relay Oat Li's. prevented. from picking upi afterrelay OLt. becomes" energized; as explained Patent; No. 25229249; consequently relays Ed? and; 11GB. remainreleased urrti'lv the indication. code transmitted; by relay I: is: complete'd Relays and;- LH are held pickedup:

r by intermittent"- ener'gization over the: normali and: reverse contactm b': ofrelay liR' and con.- sequently relay is: held; energized; until the code is completed, while relays Z' and are held; energized." over stick"- circuits" extending from terminal Eat the right-hand Contact lr oirelay l CR; contact 6 of relay LC, and their resp'ectiye contacts aand windings to terminalC'.

' In; order to minimizethe time intervalibetwe'err successive codes, thacircuits. are so arranged.

thatthecoding uni-ts:are all restored to?- normal.

atthe end oi a complete. indication code at approximately the same: time;v When relay OR at. the ofil'ce' is restored to normal: at the end of arr.

indication code; a relay O1 responds and complet'es: a: circuit from terminal 13 at the. left-hand contact a of relay GR over front contacts 0: of relaysPE and 04d and back contact e of: relay 0M through relay: O IC to terminali whereby relay Q-T'is momentarily energized to cause relay TCIto deliver a: single pulse to antennaA- tor whichme-lay' l mRi-at the repeater'station responds 7 thereby releasing rel ay s lflI-C and Z'. Relay IPC contacts cof relays O I B' and PG and: frontcontact c of'relay PCP, wherehy'rel'ays TC! and [CR are caused to operate to restore the system to normal:

Whom an indicati'on code is initiated as above described; a short propagation time may elapse before its eflfect becomes manifest at the ofiice,

during which relay OM may be energized to initiate" a control code so' that relays PC and OM may picli up together. I'n'this: case relay BC releases due: tothe opening of contact 7" of relay OM in its circuit, relay GM remaining-energized; and relay OT picks up and energizes relay TC, so that when relay I'I Q at therepeater'station releases= during the first step of the indication code deliveredl by relay" T as hereinbefore described, relay" I'CR, picks up opening the line and releasing relay l-PC, but holding re"- lay' LB energizedi Relay 1 I'PQ opens its: front COIltE'Ct-Qil'l'. the pick-up circuit for relay Z and byclosing its ba'ck contact J restores relay I'R'to normals: The long firststep= delivered; by relay IGRZ- prevents theturther operation of the stati'on tra-nsmitter "I and so leaves the ofilce trans mitten OT; in control of the transmission of the remainder ofi'th'e oodei It; will banoted that thedlrectiomofitransmissfomin this case is deter mined by whether the ofl'ice relay OMpicks up or not, the same as when a repeater is not used.

It will be seen that in the carriercurrent system as shown it is unnecessary to employ frequency discriminating circuits to prevent the operation of the receiving relay such as ICR by current from the associated oscillator OSC, since these are connected to the antenna in opposite positions of the transmitter relay 'ITC. follows therefore that the same, or approximately the same, carrier frequency may be used for transmission in both directions and that only one carrier frequency or radio channel is required. Furthermore the system of my invention is suitable for use where the attenuation is high, that is to say, where relatively high transmitted energy and a correspondingly sensitive receiving relay are required.

In the system described it is the practice to provide disconnecting apparatus at each field station, such as is shown in my application Serial No. 468,224, filed December 8, 1942, for Remote control systems, now Patent No. 2,376,569, issued May 22, 1945, whereby the operator at the control office can disconnect the apparatus at any station at will, and thereby prevent interference in the case of a fault. This is accomplished by the operation of a push button PB, shown inFig. 1A, for a period relatively long in comparison with the lengths of the code steps.

If button PB is operated during the transmission of an indication code as above described, relay TC is steadily energized, preventing relay OR from receiving the-code and causing relay ICE to become energized as soon as relay ITC releases to transmit an even-numbered code step. Relay ICR opens the line circuit, operating relay HR: to normal, and releases relays IPC and Z. and relay IPC on releasing holds relay IR normal, so that relay ITC remains released, relay ICR then' holding line YI-ZI open so that relay R remains released to correspond with the steady energization of relay TC. It Will be seen that since the operator is thus able to'reverse the direction of transmission through the repeater station at will, the distant line circuit is at all times controllable from the oflice.

Referring now to Fig. 2A, in this view a modification of Fig. 1A is shown in which the carrier circuit apparatus associated with antenna A is located at a distance from the oflice and, connected thereto by a pair of line wires Y--,Z over which the codes are transmitted in two directions. The ofiice apparatus in this view is arranged in the same manner as when the office and an auxiliary relay TS, which'function like the similar relays of Fig. 1A already described.

The apparatus of Fig. 2A may be used with that of Fig. 13 already described, in which case the communication channel includes three-sections, one including the line wires YZ, another comprising the radio channel including the antennas A and Al, and a third including the line Yl-Zl extending to the field stations, as shown in' Fig. 1B. The first repeater station, as shown in Fig. 2A, servesto repeat the codes between the line YZ and the radio channel, and includes twobiased polar line relays PR and NR connected oppositely across line YZ in series with a relatively high resistance 20, together with a slow acting'relay NP controlled by relay NR, and carrier current apparatus including a transmitter relay TC and a receiving relay CR associated with antenna A as in Fig. 1A. Normally the polarity of the current supplied by battery OB to line YZ is such that relay PR assumes itsenergized position and relay NR its released position, as shown, and. when the line polarity is reversed by the office relay PC, relay NR assumes its energized position and relay PR its released, position. When the line YZ is opened by the operation of relay OT, relay PC releases to complete a circuit from terminal B over the normal contacts a of relays NR and CR and the reverse contact a. of relay PR through relay TC to terminal C. Relay TC therefore repeats the operation of relay OT to deliver control codes to antenna A as in Fig. 1A, to which relay ICR of Fig. 1B or 2B is responsive.

When a radio impulse is received over antenna A of Fig.2A, due to the initiation of an indication code by a station transmitter relay T, relay CR responds and shunts resistor 20 increasing the current in line YZ so as to reverse relay OR,-

whereupon relay PC becomes energized as hereinbefore described, reversing the polarity of the current supplied to line YZ causing relay PR to release and relay NR to become energized. The operation of contact a of relay NR to the right disconnects terminal B from the circuit for relay TC, and causes the slow release relay NP to become energized. The indication code transmitted by relay T is repeated by relays CR and OR in the manner described above in connection with Figs. 1A and 1B, relay PC being released by a relay 016 at the end of the code. In the previous example, the code was followed by the transmission of a single impulse by relay T0 at the office for the purpose of releasing relay PC of Fig. 1B. In the present instance, the restoration of the polarity of line YZ to normal by relay PC at the end of the code causes relay PR to assume its energized position and relay NR to assume its released position, deenergizing relay NP, and the circuit for relay TC is then closed momentarily over contact a of relay NP and contact I) of relay NR, with the same result.

In Fig. 2A the operation of button PB discon-' nects battery OB from the line so that relays PR and NR both are released and relay TC is steadily energized. Relay TC is also energized if relay OT is operated to initiate a control code at the same time that relay T is operated to initiate an indication code, the operation of Fig. 2A being identical with that of Fig. 1A as already described; in these respects;

Referring now to Fig, 2B, the apparatus as shown is arranged for the control of stations connected to a line Y|--Zl which is similar to that of Fig. 1B, and in addition thereto another set of apparatus interlocked therewith is provided for the control of another group of stations connected to a second'line Y2-Z2. In Fig. 2B, the operation of the receiving relay ICR in response to a control code transmitted by the ,ofiice apparatus of Fig.- 1A or 1B causes the delivery of the control codeto both lines by the operation of its contacts a and 0, respectively, and at the same time'operates relays LB and LC as already described in connection with Fig. 1B.

Assuming first that: an indication code is mild-- ated at astation on line YX'-Zl, relay IR. reverses energizing relays ITC and IPC and transmitting a. radio impulse to-the office from antenna Al, as already described. The reversal of polarity in line Yl-Zl by relay IPC releases the line relays at other stations on that line, and those on line YZ-Z2' are released by the opening of the latter atcontact h of relay IPC, until the code is completed. Similarly, the initiation of a code at a station on line Y2-Z2 causes relay 2R toreverse, energizing relays ITC and 2P0, ,con-' tact h of relay 2P0 openingline Yl-Zl. In the event relays IR and 2R. are both reversed at the same time, only relay IPC remains energized, its contacty' opening the circuit for relay 2P6. The release of relay 2P0 places'relay 1R. under the control of line Yl-Zl to continue its operation and restores relay 2R to normal. 7

Inasmuch as relays IR and 2R are operable to deliver codes only one at a time, it will be apparent that only one set of relays LA, LB, LC and Z are required in Fig. 2B. Although the total number er stations "which may be controlled by the apparatus of Fig. 2B is no greater than in Fig."2A, this being limited by the capacity of the ofiice coding unit and being 35 stations in the system described, the repeater of Fig. 2B has the advantage that it may be located at any convenient point in the controlled territory where suitable power supply and maintenance facilities are available to'control stations in opposite directions and it is unnecessary to locate it at one end of the line.

Although-I have herein shown and described only; a few forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appendedclaim s without departing from the spirit and scope of my invention. L

Having thus described my'invention, what I claim is:

1. In a remote control system, a repeater connecting two communication circuits including'fa receiving relay controlledover each circuit for repeating received impulses into the circuit for the other, each such relay being controlled by the other to renderit nonresponsive to repeated impulses, a first and asecond stick relay each having pick-up and stick circuits "controlled over a normally closed contact of one of said receiving relays, means including a normally open contact of the other receiving relay for completing the pick-up circuit for the first stick relay as soon as such relay starts to repeat received impulses into the circuit for said one receiving relay, means responsive to the operation of said first stick relay for terminating the control of the circuit for said one receivingrelay by the other and for rendering said one receiving relay effective to repeat code impulses in the opposite direction through said repeater in the event impulses are received from both circuits at the same time, means including a front contact of said first stick relay and a normally closed contact of said other receiving relay for completing the pick-up circuit for the second stick relay only if said one receiving relay is not operated during the reception of the-first impulse of a code by the other, and means controlled by said second stick relay when energized for again rendering said other receiving relay effective to repeat the remaining impulses of the code received thereby into the circuit for said one receiving relay.

2. In a remote control system, a repeater station including two receiving relays, a. communication channel extending from said repeater station to a. control oflice, a code transmitter at said omce for supplying codes. of impulses to said channel to which one of said receiving relays is responsive, a line circuit extending from said repeater station to a remote station, a code transmitter at said remote station for supplying codes of impulses to said line circuit to which the other receiving relay at the repeater station is responsive, code receivers at the oflice and Sta-- tion, means including contacts of said one receiv-. ing relay for repeating the code impulses re ceived from said channel to said line circuit to operate the station receiver but without operating the other receiving relay 'at said repeater station, means including contacts of the other receiving relay operated in response to the first impulse of a code received from the station for supplying a relatively brief impulse to. said channel to which said oiiice receiver is responsive but without operating said one receiving relay controlled over said channel, and means efiective only if said one receiving relay remains in its non-operated condition following the transmission of said brief impulse for conditioning said other receiving relay to repeat the remaining impulses of the code received from the station into said channel. a

3. In a remotecontrol system, an office and a station, a first and a second communication channel connected byfa two way repeater, including a repeating relay'in each channel each responsive only when the other is in its normal non-operated position for repeating code impulses received from one channel into the other in either direction, code transmitters at a'control ofiice and at a remote stationfcr supplying code impulses to said first and to said second channel respectively, a stick relay in said repeater, a circuit for energizing said stick relay closed in response to an impulse received from said second channel due to the initiation of a code by the station transmitter, means controlled by said stick relay when energized conditioning said station'transmitter to complete its code, means for holding said stick relay energized only so long as the repeating relay in said first channel remains in its normal position, means for locally terminating the first impulse of the code repeated into said first channel to render the repeating relay in thefirst channel responsive prior to the termination of the first impulse received from the second channel in the event an impulse is being supplied by the office transmitter to said first channel at the time whereby said stick relay is released and the operation of the station transmitter is discontinued before completing the first impulse of its code.

4. In a remote control system, a, first and a second communication channel connected by a two way repeater including a repeatingrelay in each channel, each responsive only when the other is in its normal non-operated position for repeating code impulses received from one channel into the other in either direction, code transmitters at a control oilice and at a remote station for supplying code impulses to said first and to said second channel respectively, receiving relays at the office and station responsive to impulses received over said channels, a stick relay in said repeater, a circuit for energizing said stick relay closed in response to an impulse received from said second channel due to the initiation of a code by said station transmitter,

means efiective only when said stick relay is en-,

ergized for conditioning the station transmitter 'to continue the transmission of its code, a holding circuit for said stick relay closed only so long as the repeating relay in said first channel remains in its normal position, means causing the first impulse repeated into said first channel to be of relatively brief duration and for rendering the repeating relay therein responsive during the reception of the first code impulse from said station transmitter whereby its continued operation is rendered dependent upon the non-operation of the office transmitter, and means at the oflice responsive to said impulse of brief duration received over the first channel for locally holding said receiving relay in its operated position for a time corresponding to the duration of the first code impulse supplied by the station transmitter to said second channel.

5. In a remote control system, an ofiice and a repeater station, two normally energized line cir-. cuits including sources of current at said repeater station and extending through different remote stations, code transmitters and receivers at the oflice and at each remote station a receiving relay at the repeater station having a normally closed contact in each line circuit, a line relay for each line circuit responsive to current variations therein at the repeater station, means controlled by the ofiice code transmitter for transmitting codes of carrier current impulses to which said receiving relay is responsive to control the receivers at the stations on both line circuits, means for setting the code transmitter at each remote station into operation when the adjacent line circuit is energized to vary the current therein periodically in accordance with a code, means controlled by each line relay for transmitting carrier current impulses to which the office receiver is responsive in accordance with such code, two stick relays at the repeater station including one for each line circuit each having a back contact in the line circuit for the other, means responsive to the initiation of a code by a transmitter at a remote station for energizing the corresponding stick relay, a holding circuit for each stick relay including a normally closed contact of said receiving relay, means controlled by such stick relay when energized for conditioning the station transmitter to complete its code, means comprising a back contact of one stick relay included in the circuits for the other to cause only one stick relay to remain energized when both are operated at the same time, and means controlled by the officer receiver for transmitting a single impulse of carrier current to which the receiving relay at the repeater station is responsive to release the energized stick relay upon the reception of a complete code at the oflice.

6. In a remote control system, a carrier'current channel for communication between a control oilice and a repeater station, a line circuit extending from said repeater station to a remote station, a code transmitter at said remote station adapted when initiated to deliver a code over said line circuit to said repeater station, a repeating relay at said repeater station responsive to said codes and having contacts for supplying carrier current tosaid channel to repeat said codes over said channel to the office, a stick relay at the repeater station, means for energizing said stick relay upon the first operation of said repeating relay when a code is initiated by said station transmitter, means controlled by the stick relay when energized to condition the station transmitter to complete its code, two slow acting relays one controlled over a normal contact'and the other over a reverse contact of said repeating relay and means dependent upon the continued energization of both of said slow acting relays due to the code operation of said repeating relay for maintaining said stick relay energized only as long as said code transmitter continues its operation.

7. In a remote control system, a control ofiice, a, repeater station and a remote station, means for transmitting codes in two directions between the control ofiice and the repeater station, a normally energized line circuit including a source of current at said repeater station and extending to said remote station, a code transmitter at said remote station adapted to initiate the transmission of a code over said line circuit only when it is supplied with current 01 normal polarity and to continue the transmission of such code only when it is supplied with current of reverse polarity, a line relay at the repeater station for retransmitting such code to the oflice, a receiving relay at the repeater station having contacts in said line circuit for repeating codes received from the oflice to the remote station, a first slow acting relay controlled over a normal contact of the line relay, a stick relay having a pick-up circuit including a reverse contact of the line relay and normally closed contacts of the receiving relay and of said first slow acting relay, means comprising contacts of said stick relay for reversing the polarity of the current supplied to the line circuit when said stick relay is energized, a second slow acting relay having one energizing circuit controlled by a normally open contact of said receiving relay and another controlled by normally open contacts of said line relay and said stick relay, a third slow acting relay having an energizing circuit controlled by front contacts of said first and second slow acting relays, a holding circuit for said stick relay including its own front contact, a normally closed contact of said receiving relay and a front contact of said third slow acting relay, and means for locally energizing said line relay in one direction when said stick relay is picked up and said second or third slow acting relay is released and in the other direction when said stick relay is released and said second slow acting relay is picked up.

GEORGE w. BAUGHMAN.