US2459494A - Line circuit communication system - Google Patents

Description

Jan. 18, 1949. F. w. BRIXNER ETAL LINE CIRCUIT COMMUNICATION SYSTEM Filed Jan. 26, 1948 m 4 BE; m2: 385%: EU zocumn fi IE? ELQEE 55% E55 38 TJ J T {111... new m Pr! v vm m: m illl ill. SN

r SIK V Rr E O N Ta R m y m W M I W M r PIY NEENGU L 3 e V Q m 3m q 5 u f MEIQEOEZS 2Q PS ZOE. Eh QPZQ mum I836 QEQEE U75 SEQ SE28 Patented Jan. 18, 1949 UNIT ED? OFFICE LINE"CIRGUIT GOMMUNICATION SYSTEM Frederick. .Brixnen. Gates, and. William. M.. Barker, Greece, Nl'Yigassignors .t'o'General Railway .Signal, Company; Rochester; Ni Yi ApplicatibmJanuam-ZG, 19.48, SeriaLNo. 4,418.

6 Claims. (01. 177453) 11 l This. invention relates; to. line-circuit communication. systems, and; it more. particularly pertains. to. means for transferring. a; linercircuit. used'for direct. and for alternating... current communication from one pair oifllinerwirestolthe. other.

In a line: circuit communication system. such asa centralized trafiic. control system for railroads,..conveniently termed aCIJZC system, a. central control oflice. governstiafiicv throughx aapan ticular. assigned territory by line circuit communication. ofcontroll and indication. It. is often,

desirable to locate the control oflice in a. downtown office building, on the.like, remote.from the CTC territory with which the. control office is.

associated, inorder to takeadvantage of central ofllcefacilities. Under such. conditionsthe connection. of .the. oiiiceto communication line wires at the. beginningof. the C'I'C'iterritory is often accompli'shed through aerial and/r under ground cable, or the like, which is necessarily somewhat" subject to damage as the result of weather conditions orasxaresult oi damaeeworkmen. the maintenance. of communication. wires which may.v

be. closely. associated therewith. It is therefore desirable to. provide spare line Wires, preferably indifferent cables anddifiierently routed, to which the CTC line .circuit' can. be transferred in. case of loss of continuity through one .pair ofline wires, ,or in case. of other lineicircuit" difiiculties; interfering with the communication of? controls. and indications between. theicontrolofiiceand" the OTC territory with which it is'associ'ated:'

An objectofth'e present inventionis toprovide means responsive to' manual designation" by; an operator" atthe control oifice icr-transier-of a CTC line circuit from one pair ofilin'ewiresto another ina manner was to isolate onepair of line wires at both ends from theotherpair:

Another object of" the present invention-istw render theshifting from one linecircuit=to-the-- other-effective through a carrier repeater station soa s to -effect the transferof thecircuit extend the idle linee wires in. combination with .a. locally" energized transfer stickirelay.

Another. objectof thepresent inventiontistoz useatheline circuit transfer means atthe, repeater. station to: shift .to: "standby repeater; apparatusiin response. to manual; desie'nation at the. control office.

Other objects purposes and. characteristic tea.- tures. of the presentliinventi'on willlbedn. part obj-- vious from the accompanying-drawings, andin part poi'ntedlout as: the description. of the invention. progresses.

is made to the accompanying.drawlngswhich illustrates schematically, with some parts. shown. in

block form,. an organizationior the transfer of. a C'ICdin'ecircuit from one pairtofli'ne wires to used inthe" drawing as representati'ng connections torespectivepositiveand negative-terminals: of. suitable batteries" or other sources of "direct" current.

Inasmuch" as theispecific character ofthe CTC' transmitting" and receiving apparatus for" communication of controlsand-indications-over the line circuit has little "bearing on the presentinvention, for the purpose of simplification of=this embodiment of the-present invention; such appaartus has been-indicated on the" drawings in block form; and it' is'to be-understood that this appaart'us Whichis well known tc== those familiar with the-artis provided according" to the re quirement-s of practicer If desimedythe D. CJ-CTC" transmitting-and receiving apparatus can be-dis-'- closed; for"examplein the patent mew; D5 Hailes et-al. No. 2*,3'99'5734, dated 'May '7 ;'194'6? For this embodiment of the present invention,v it is assumed thatiboth direct current GTC pulsesand alternating current carrier pulses are-trans mitted: over the-dine wires illustrated in the: drawings; The direct currentpulses'arausediior the communication? on controls-and indicationstor a firstsection of the: territory for:which the CTIIG', icontriolcmachinesris providedu and the: car rieri apparatus: is- -u'sed ifiorithe communicationzofza controls and indications over the.linetwiresrandt through :the. first sections otxithe CfIKCL. territory 1 to a suitable. connerteri: station. where: carrier: puises: fiGIEJthG'." communination of? controls are converted .iniinir direct .cunrenin pulses; anntthe.

direct currentzindieation pulsessreceivedxrhy.such.

comzerter 'statiomf-nomcthe: secondrsection; of? the. C'IiC,.territonyr; an t. converted iintotcarrien r pulses fort communinati'om through the: first sectiomofi; therCTC territory and; the: line; .wireszillustratedc in the: drawinga- .toiu theecontrol 5 01116815 It-Jiss Dfzi coursera mattenrofi choiceizasto wthew frequencies; used-.iomcarrier communication oft controls; and indications; and itthaswbeen fGHHdrzfihflfilCfliIIiBI frequency; currents-in; the band from. 10 to-.2G Inca.

are satisfactory, distinctive frequencies bein generally employed for the communication of controls and indications.

Because of attenuation of the carrier pulses, carrier repeater stations are required at intervals for amplification of the carrier pulses, and thus the carrier repeater units Nos. 1 and 2 are provided at the carrier station illustrated in the accompanying drawing for repeating the carrier pulses received from the control ofi'lce into the line wires L1 and L2 extending in the direction of the CTC territory.

Each of the carrier repeaters illustrated in block form in the accompanying drawings is to be understood as including electronic amplification means for amplifying the respective control and indication frequency currents, the'wires Ill and l I being the in-put wires for the communication of controls and the out-put wires for the communication of indications for the carrier repeater No. 1. The wires l2 and [3 are the out-put wires of the carrier repeater No. 1 for the communication of controls and the in-put wires for the communication of indications. The carrier repeater No. 1 is illustrated as being associated with the line wire ILI and IL2 as selected by the position of the carrier repeater transfer switch CTS, such switch being effective in a manner to be hereinafter considered to select between carrier repeater No. 1 and carrier repeater No. 2. It is thus provided that only one of the carrier repeaters is used at a time, two identical carrier repeaters being provided so as to cause a minimum interruption of service in case of failure of the electronic control apparatus associated with any onecarrier repeater unit. the carrier repeater No. 2 can be considered as a standby carrier repeater although means is provided as herinafter considered for manually selecting as to which repeater is to be the standby repeater The wires ILI and IL2? constitute one pair of line wires, which may or may not be in aerial or underground cable, for connection of the portion of the CTC line circuit. connecting the control office and the repeater station, and the wires 2L1 and 2L2 constitute a second pair of line wires, conveniently called standby wires extending between the control oflice and the repeater station to which the line circuit can be shifted as required. It is of course desirable that the respective pairs of wires be routed separately as much as possible so as to reduce the possibility of failure of both pairs of wires at the same time. In a similar manner the wires ILI? and IL2 constitute one pair of line wires connecting the repeater location and the beginning 'of CTC territory, and the wires 2Ll and LL2 constitute the second or standby pair of wires extendingbetween these points.

At the control oifi'ce the line transfer switch LTS is located convenient to the operator of the control machine, preferably on the panel of the control machine, and it is provided as a means for manual designation of the particular pairs of wires and the particular carrier repeaters that are to be used in the line circuit of the CTC com-' munication system. Associated with the line transfer switch at the control office is a line transfer relay LT, the contacts of which directly select as to which of the pairs of line wires extending from the control office is to be connected to the CTC carrier transmitter and receiver at the control office. It is to be understood that the relay LT is used in combination with the In other words particular pair of line wires that has been idle in a manner to be more clearly understood when considering the mode of operation of the organization. In a similar manner, at the beginning of the CTC territory, the relays LIl and LTZ are provided for transfer purposes, such relays being associated with the respective pairs of line wires extending between the repeater station and the beginning of the CTC territory.

Stick relays LTP and LT]? are provided respectively at the repeater station and at the beginning of the CTC territory for transfer pur poses, such relays being controlled by the associated relays LTI and LT2 at such locations. A relay CTR at the repeater station is used to transfer from one repeater unit to the other at the repeater station in response to the actuation of switch LTS at the control oflice. It also is used to select the application of power to the particular carrier rep-eater unit that is to be rend'ered active.

Having thus considered the general organization of the system according to the embodiment of the present invention illustrated in the accompanying drawing, the organization will hereinafter be more specifically considered upon considering typical conditions of operation to be encountered in practice.

Operation It has been illustrated in the drawings that the line wires I Li and IL2 are connected so as to be in use in the CTC line circuit under conditions that may, for the purpose of facilitating the description of the present invention, be assumed to be the normal conditions of the system. Similarly the carrier repeater No. 1 and the line wires ILI and IL2 are in use during the normal conditions of the system.

In accordance with the general principles of operation of the above mentioned CTC system as disclosed in the patent to W. D. Hailes et al. No. 2,399,734, the line circuit is normally energized during a period of rest when no controls or indications are being communicated and such energization can-be traced to connect the positive terminal of the line battery CB to the line wire L2 =at the beginning of the first section of CTC territory, through selections of the CTC apparatus at the control offices, wire L2, back contact [5 of relay LT, wire ILZ back contact 18' the beginning of the first section of CTC territory through selections of the D. C.-CTC transmitter and'receiver at the control office, wire Ll, back contact [4 of relay LT, wire ILI back contact 22 of relay LTP, choke l6, back contact 23 of relay LTP, wire ILI back contact 24 of relay LTP and winding 25 of the impedance matching transformer 28.

it will'lbe noted mm the selecticnthat hasjust been traced for the eonm'ection ofthe control bat-- tery CB to the line wires L1 andLl th'at'there are no line transfer relays ii'I-l' or LTTenergized bythe-iine circuit at* thistiine as such relays areenergi'zed only momentarily-upon shifting to the alternate pair of'lihe wires aswill be hereinafter" considered; In-addition'to the-"direct cur 1 rent CTC circuit connections as hasqbeenjust- CTC transmitter and" andLZL;

The. transmission-Maire carrier currents; however isblocked-in the repeater station by'the receiver to thewires' Ll choke; coils Hiandlland thus rather than being directly" connected through" the repeater station, the control carrier-frequency currents are fed as. in -put to thecarrier repeater No. 1 in which they are amplifiedandappliedas out-put to theline wires; extendingto the CTC territory. Indication carrier current pulsesarefed' back from the C'IC territory to. the control oiiice at a distinctive frequency over the same circuit.

Itis. therefore proyided;thatthe. carrier.current pulses for the communicationof controls are transmitted from thecontrol'oflice and applied across the wires IU'andQ-ITI' lof vth'ecarri'er repeater No. 1. Ifhe wire Lll-of'the. OTC" transmitter at the. control oificeis connectedtc the wire, HJJof carrier repeater No. 1 through back contact I 5 of relay. LT, wire. I.L2 backxccntacti l8. of relay.

L'I'Pand back contact 26.. off relay CTR. The wire Lllof the OTC transmitters. atthe control office is. connected to thewine H offlthecarrier repeater No. 1. at the repeater station through back contact M ni. relay LT, wire. l.L.I.1 ,.backccntact. 2.2 of relay LTP and back. contact 2'! of relay CTR! o The carrier repeater. No. L-isconnected'to the impedance matching. transformer. 28 by a. circuit includingwire |2..of carrier repeatenNd. 1, back,

contactlza of relay CTR, backcontact [9 .of relay LTP; wire iLZZ; back contact 20 0f; relay LTP winding 30 of. the impedace. matching. trans-v former 28,. coupling. condensenCl, winding 3| of the impedance matching transformer 28., .back.

contact 24' 'ofrelay LTP wire ILW, back. contact 23 of relay L'IP; and back contact; 32.. of, relay CTR to the wire [3' of the carrier repeaterNo. 1.

The line wires LI? and. L2 are connected 23; being assumedfto be. in a cable having re1a-. It is to. be understood.

tively lower impedance. that if no impedance matching is required under these conditions, the impedance matching transformer Z8. is not required and the wires LI and L2 are energized directly fromfthe contacts of the relay LTP The condenser C l is included in the transformer circuit as a blocking. condenser for direct current energization ofthe line wires. It will be seen from the. organization as it has been described'up to this pointthat there are rawings is connected in multiplewith' the D. -01- several poss'ibilitiea ottfailune .inrthe integrity? 0:14

the line circuit betweenthe controtoflice and the CTC" territory whicirican cause failure: of- :the. OTC system to operaterproperlm. Qne. of;thesew conclitionsis in the line wiresJLH andiLZ either of which maybecome. open circuited; or. these:

wires may become short. circuited'because of.

damage to the cable.- Similarlythe wires: ILA? and;

IL2 extending f'rom the: repeaters station to the first section of CTU'territory may become. open: circuited' or short circuited torcausefailure of. proper operation of the OTC system. Because of thecarrierrepeater-Not 1' atthe repeatersstation being' 'dependent. upon electronictubea a failure of the electronic apparatus: can interrupt: theservice between the contr olofi'ce and the: OTC territory, thus making it desirable to beable to transfer tothe stand-by carrirrepeater-ap. paratus No. 2.

If failure occurs under any one of'inore of the three above describedconditions, the operator at the control ofiice uponbecoming aware of the failure, may; by actuation of the line' transier switch L'IS-on the control panel of the control machine, cause the-transfer of then C. and

A. (3'. communication line circuitsfromthe-nor-- mal line Wires ILI and lL2 to the standby line wires 2Ll and 2L2 Iirresponse'to the-trail for being rendered effective at the-repeatersta tion, energy isapplied to the standby wires 2-Ll and LL2 so as to complete the-transfer tothese Wires at the location of thebeginning ofCTC territory. Also a transferiseflective to shift from the carrier repeater station-No; 1* to the'sta-ndby carrier repeater No. 2.

the consider more specifically: the manner in; which the above described transfer operation is effective, the actuationof *theswitc'h LTS at'the control office is effective to pick up. the relay LT and. open the connection of the wires LI, and L2 tothe wires lLI and ILZ at 'backcontacts It and Hi, respectively; The shifting of contacts I4 and I51 of relay LT; (upon the picking; up of that relay, connects the wires 2Ll and 2L2 to the wires LI and. L2; respectively. Because of'direct: current energy being, applied bythe D. C'.-CTC transmitter at the control office to thewires Hil and 2L2 through the front contacts l4 and I5 of relay LT, the relay LTZ at the repeater station becomes energized by a circuit extending. from the wire Llat the control .ofli'ce, including front contact 54 of relay LT,wire 2Ll back contact 33 of relay LTP, winding of relay LTZ, back contact 34 of relay LTP, Wire 2L2 andfront. contact l5 of relay LT, tothe wire L2.

Upon the pickingup. of relay LT2,Ithe stick relay LTP is pickedlup by theclosure of front contact 35,. and. the picking up of that relay es-' tablishes a stick circuit extending from in cluding back contact 36' of relay LTl, front contactii'l of relay LTP. and winding of relay LTP, to By this stick circuit, pickup contact 35 is shunted out, and it is provided'that the restora-. tion. of relay LTP can be accomplished only by the subsequent picking up, of the relay L'Ii at a time when an operatoratthe control office designates the restoration to the former line circuit by the restoration of the switch LTS to its normally open position. The picking up of the relay LTP, by the openingofback contacts 33and 3 4- deenergizes the relay LTZ and thus provides that" the. relay LTZ is disconnected from the line circuit and. dropped. away immediately subsequent to the picking up of relay LTP.

The closure of front contact 34', ofrelay' LTP provides that direct current energy is applied from wire 2L? to the wire 2L2 through the choke l1 and front contact [9 of relay LTP. Similarly the wire 2Ll is connected to the wire 2L| through front contact 33 of relay LTP, choke l6, and front contact 23 of relay LTP. It is thus provided that direct current energy is fed from the control battery CB at the control office through the back contacts 38 and 39 of relay LTP to the winding of relay LT2 at the location of the beginning of the first section of CTC territory. s n

The picking up of relay LT2 by the closure of front contact 48 causes the picking up of the re lay LTP which is maintained picked up by its stick circuit extending from including back contact 4! of relay LTI front contact 42 of relay LTP and winding of relay LTP to The relay LTP when picked up connects the wire 2L! through front contact 38 to the im pedance matching transformer 28, and the closure of front contact 3c of relay LTP connects the wire 2L2 to the impedance matching transformer 28. It is thus provided by the mode of operation as above described that the D. C.-CTC line circuit is shifted to the standby circuits extending from the control office to the repeater station and from the repeater station to the beginning of the first section of CTC territory.

The carrier current line circuit is necessarily similarly shifted in that it involves the use of the same line wires, and in addition, there is an automatic shift from the carrier repeater unit No. 1 to the carrier repeater unit No. 2. This is accomplished by the picking up of the relay CTR y:

at the repeater station in response to the picking up of relay LTP. Relay CTR is picked up by 'a circuit extending from including the front contact 49 of relay LTP, contact of the carrier transfer switch CTS in its left hand position, and Winding of the relay CTR, to The picking .up of relay CTR, by the shifting of contacts 26 and 21 opens the connections to the wires l and H of carrier repeater No. 1 and closes connections to corresponding wires 43 and 44 of carrier repeater No. 2. Similarly the shifting of contact 32 opens the connection of the wire [3 of the carrier repeater No, l and closes a connection for the corresponding wire 45 of the carrier repeater No. 2. The shifting of the contact 29 opens the connection of the wire I2 associated with the carrier repeater No. l and closes a connection for the corresponding wire 46 associated with the carrier repeater No. 2. Inasmuch as the contacts 23 and i9 have shifted upon the picking up of relay LTP the wires I for provided that the transfer in response to the actuation of the switch LTS at the control office is effective not only for the shifting from one pair of line wires to the other for both the line portion extending between the control office and the repeater station and the line portion extending between the repeater station and the first section of CTC territory, but it is also effective to transfer from one carrier repeater unit to the other.

It Will be noted that the local direct curren power for operation of the respective carrier repeaters is selected by the relay CTR so as to apply power only to the particular carrier repeater that is used in the carrier line circuit. Thus the closure of back contacts 4'! and 48 of relay CTR applies direct current power to the carrier re- 8 peater unit, No. 1, and front contacts 4'] and 48 applies directcurrentpower to the carrier repeater unit No. 2.

If for some-reason it is desired to reverse the order of the association of the respective carrier repeater units with the normal and standby line wires so as to havethe carrier repeater No. 2

normally active when the line wires ILI lL2 ILI and lL 2 are in, use, the carrier repeater transfer switch CTS at the repeater station can be actuated to its right hand position to thus select thatthe relay CTR is picked up in response to the closure of back contact 49 of relay LTP as compared to the picking up of this relay through front contact 49 of relay LTP as has been described.

Assuming that the particular difficulty has been remedied in the line circuits and/or carrier repeater unit that is normally used, transfer can be eifected back to these wires which have been described as beingused under normal conditions.

In order to accomplishthis transfer back to the normal channels of line circuit communication, the operator actuates the line transfer switch LTS back to its normally open position and thus allows the dropping away of the relay LT. By the opening of front contacts l4 and I5, the wires 2Ll and 2L2 are disconnected from the wires LI and L2 at the control oflice, and

the closure of back contacts l4 and I5 connects the wires [LI and IL2 atvthe control office in a manner which has been described when considering the normal conditions of the system. It is thus p rovided that direct current energy is applied from the battery CB to the wires ILI and iL2 at the control ofiice at a time when the relay LTP is picked up at the repeater station, and thus a circuit is closed to energize-the relay LTI extending from the wire Ll at the control ofilce including back contact M of relay LT, wire lLl front contact 22 of relay LTP, winding of relay LTI, front contact l8 of relay LTP, wire IL2 and back contactl5 of relay LT, to wire L2. Upon the picking up of relay LTI, the opening of back contact 36 in the stick circuit for the relay LTP causes relay LTP to be dropped away, and the dropping away of that relay opens the connection through the repeater station that has been established through front contacts 33 and 34 of relay LTP, and closes circuit connections to the wires lLl and IL2 through back contacts 22, I8, Hand 23 to establish circuit connections which have been described when considering the'normal conditions of the system.

Upon the dropping away of relay LTP, the circuit for relay LTI is opened at front contacts 22 and I8, and thus that relay is dropped away to close back contact 36 and condition the stick circuit for the relay LTP so that it can be established upon subsequent transfer to the standby line Wires.

Assuming the carrier repeater transfer switch C'IS to be in the left-hand position as illustrated, the carrier transfer relay CTR'is dropped away upon the opening of its circuit at front contact 48 of relay LTP, and by the shifting of contacts 32, 21, 26 and 29 of relay CTR, the carrier repeater unit No. I is again rendered active and the carrier repeater unit No. 2 inactive. The shifting of contacts l-l and 48 of relay CTR disconnects the local source of power from the carrier repeater unit No. 2 and connects such source to the carrier repeater unit No. 1.

Having established continuityfrom the control oflice including wires, LI and L2, through the re- Meme 1 9 peaten stationt and-the normal-slime, wires 1L] and |L2, witn the relay; H119? it picked up the relaylLTl 1 becomes energizedtthroughl front contents 20 and-.24 and r the t; picking 11p! ofthat relay by the'opening of backtcontact(M provides, for the-.dropping away ofrtherelayLTPH Upon the dropping, away: oi relaytLTRl, the connections from wvires 2L! andu2L2. to. the, impedance matching,-trans.fiormer Zhthrough: frontfcontacts 38.-and 39, or relay-LTB are opened, and the closures-of back; contacts :-20.:and 24s connects ;the wires -IL.| and ALI? to the impedance matching transformer in a manner, which has, been .more

specifically described, whennconsidering the normal conditions of thesystem.-. The opening of front contacts 24 andfld disconnects the: relay L 'lll andycauses that relay to be droppedtaway SGfBrStG close back contact-M tosconditionthe stick oircuitior thet-relayl-LTP so that such stick circuit can .be-established upon subsequent transfer: tOI, the standby wires- 2L1 and ZLZZ. This completes the restoration fromtthe usesoft the standby lineawiresand standby carrier repeater unit No. 2 to the normalline wireswand carrier repeater'unit No; lwWl'liCh are considered to be normally used-ltelecommunication purposes.

Although only a single repeater r station has been illustrated-in this i embodiment of the present invention; it *lSrtO, be understood that as many repeater rstationslmay-be provided as are required in, practice; 1the'stationrillustrated being typical of othen'stationsewhich can bezaddeds It is believed that, it should berreadily apparent that the :mode of: operation" where-a; plurality-of, repeater stations. isinvolvedsisr comparable to that which has been described: inwthat thestandby-line circuit is put-togetherinssteps fromlthe control office, and restoration to the line wireslnormally employedis accomplished in a: a similar a manner.

It is alsoto be understood1thatif the-linelcircuitwis short enoughsotasnot-lto require-la: repeater stationrfor thercommunicationt of carrier current pulsesthatithe repeaterstat-ion canbe eliminated, land-under; SUChmCOIlditiOl'lS the respective rnormal L ands-standbypairs of; linenwires are unbroken between the control oificeaand, the beginningiof the CTC territory; Under such conditions the line. transfenmelays LTI and LTI will be energized directly from the control office through the respective normal and standby pairs of i line :wireawitin which theyiare associated.

Although this embodiment aoftthe present invention is illustratedas beingapplied to the use of a combination of direct currentand carrier current: communication line-z circuits, it is; to be understoodz thatthe.system'rof'line transfertthat 'isvhereinr discl osed ,is. equally rapplicable to; conditions Where only direct current or only carrier current communication line circuits are involved. If only direct current line circuits are involved, no repeater station is required, and the normal and standby pairs of line wires are directly connected from the control offlce to the location at the beginning of CTC territory. If only carrier current communication line circuits are involved, the line transfer organization is provided as illustrated in the drawing except that a source of direct current is necessarily connected to the wires Ll and L2 at the control office as a means for energization of the line transfer relays LTI and LT2. It is to be understood that such direct current energization would not necessarily have to be steady, but could be selected through a suitable transfer push-button or other momentarily actuated means whereby the direct current would 10 be appliedito. the. line wires ,only, at times. when transferis to-be effected.

Hayingithus describedonespecific embodiment of. the presentlinventionerelatinggto: means for transferring, a. line circuitlofl'a centralized traffic control systemlirom one pair. of line wires to the other, it is desired to be, understood that this form is selected tolfacilitatethe disclosure iof the invention rather thanntonlimitmthenum'ber of forms which thein entionmay-assume, and it is tobe further understood that various adaptations, alterations and modifications. may-be applied totthe specific form: shown to meet the requirements of. practice .without in any manner departing-from. the .spirit, orscope of, thepresent invention: except as limited, by the. appending claims.

What. we claimtis:

1.1 In. aline circuit ;communication system for ,applying,communication, energy toa pair of controlwires atta locationlrcmote iroma control office, ,a normal and astandby pair. of line Wires extending frontthe-.oificevtorthe locatiomtmanur ally operable means at. the l oiiicel for selectively applying energy; to. eitherfsaid. normallort said standby, pair of ulinecwires, normally deenergized transfer and sticktrelays-lat saidlocationnormally eiiective to connect .saidtnorrnalr pai'rtofline wires toisaid control wires; circuit .-means for connecting, said transfer. relay, acrossssaidrstandby pair of line Wires wherebyl saiditransfer relay is .picked upupon theapplication or energy itoisaid standby pair of line Wiresattheofilceiby, saidinanually operable means, circuitmeansforenergizingsaid stick-relayin response; to the picking upi. of said transfer relay, aridmeansresponsive.tothe pick ingup; of said stick ,relay f or disconnecting said transf en 1 rel ay, and. f or 1 transferringlth'e connection of said pair of control wires fromvsaid normal l pair of line. wiresttobsaid lstandby, pair of line wires.

2, In: a ,line circuit communication system of the character.ldescribedtfor applying energy to a pair.- of control 1wires.attallocationmemotelfromia control office, aenorinaltand a. standby pairof line wireslextending fromitheloffice.toithe location, manually, operable means. at .1 theuoffice, for selectivelyapplyingenergy ,tdeithersaid. normal or said. standby. pair. ofeline. wires. a. normally .deenergizedv line transfer .relay at saidilocation associated witheach, pair. of-.1ine.:wiries, ,a. nor,- mally deenergizedtransfer stick..relay atsaid location, circuit-means..forconnecting one, of said transfer relaysrtol sand- ,stanby line wires .throughaaback contaot oflsaid stick relay, circuittmeans-forr connectinglthe other of said/transfer relays =to said: normalalinecw-ires :through. .a front contact of said stick relay, circuit means for energizing said stick relay in response to the picking up of said one transfer relay and for deenergizing said stick relay in response to the picking up of said other transfer relay, and means selected by said stick relay for selectively connecting said control wires to said normal or said standby pair of wires.

3. In a line circuit communication system for maintaining communication between a control office and a pair of communication wires at a remote location, the combination with normal and standby pairs of line wires extending between the control oifice and the location and means for selectively applying direct current energy at the control ofiice to one pair of line wires or the other, of line transfer means at the .loca tion comprising a normally deenergized line of said one transfer relay, and stick circuit means for said transfer stick relay effective to maintain that relay picked up only so long as said other transfer relay is maintained dropped away.

4. In a line circuit communication system of the character described for maintaining communication between a control ofiice and a pair of communication wires at a remote location, normal and standby pairs of line wires extending between said office and said location, a repeater station between said control ofiice and said location at an intermediate point in said line wires, said repeater station having normal and standby repeater units respectively associated with said normal and standby pairs of line Wires, line transfer means including a stick relay at the repeater station selectively governed in accordance with the application of direct current to said normal or said standby pairs of line wires at the control office, local energization means at the repeater station for each of said repeater units said means being effective to energize either said normal or said standby repeater unit as selected by said stick relay, and transfer means at said location effective in response to a shift in direct current energization at the office from one pair of line wires to the other to transfer the connection of said pair of communication Wires at that location from one of said pairs of line wires to the other.

5. In a line circuit communication system for communication by direct current and alternating current energy simultaneously over the same pair of line wires from a control ofii-ce to a pair of control wires at a remote location, a repeater station between said control office and said location, said repeater station having normal and standby repeater units, normal and standby pairs of line wires extending between the office and the location through said repeater station, manually operable means at the control office for selectively energizing either said'normal or said standby pair of line wires, a transfer stick relay at the repeater station effective to selectively connect said normal or said standby wires through said repeater station, said stick relay also being effective to selectively connect said normal repeater unit or said standby repeater unit in the line circuit, electro-responsive means at the repeater station normally connected through a back contact of said stick relay to said standby wires, said electro-responsive means being effective to energize said stick relay in response to the energization of said standby wires by said manually operable means, and means at said location responsiVe to the energization of said standby wires for transferring the connection of said pair of control wires at that location from said normal pair of line wires to said standby pair of line wires.

6. In a line circuit communication system for maintaining alternating current communication between a control ofiice and a pair of communication wires at a remote location, normal and standby pairs of line Wires extending between the control office and the location, a repeater station at an intermediate point in said line wires having normal and standby repeater units, manually operable means at the control ofiice for selectively energizing either said normal or said standby pairs of line Wires with direct current, means at said repeater station for connecting said normal pair of line wires through said normal repeater unit for alternating current communication, normally deenergized line transfer means at said repeater station responsive to the energization of said standby wires at the control ofiice and effective to connect said standby wires through said standby repeater unit for alternating current communication, means at said repeater station for bypassing said repeater units for direct current communication whereby the direct current applied to said normal or said standby pair of wires at the control office is applied eifectively to the corresponding pair of line wires extending between said repeater station and said location, and normally deenergized line transfer means at said location energized in response to the direct current energization of said standby line wires, said line transfer means being efiective when deenergized to connect said normal line wires to said pair of communication wires and effective when energized to connect said standby line wires to said pair of communication Wires.

FREDERICK W. BRIXNER. WILLIAM M. BARKER.

REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,135,295 Stewart Nov. 1, 1938 2,171,751 Jackel Sept. 5, 1939

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