US1493109A

US1493109A - Telephone system

Info

Publication number: US1493109A
Application number: US402631A
Authority: US
Inventors: Jr John Davidson
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1920-08-10
Filing date: 1920-08-10
Publication date: 1924-05-06
Anticipated expiration: 1941-05-06

Description

May 6, 1924;

J. DAvlDsQN, JR

TELEPHONE SYSTEM Filed ug, 10

" Affi( May e, 1924. 1,493,109"

` J. DAVIDSON, JR

TELEPHGNE sYsTM i Filqd Aug. 1Q 1920 3 Sheets-Sheet 2 A/r/g. 2.

/n Venor':

John Davidson ,by Aff);

VMay 6 1924.

J. DAvrDsoN, JR

TELEPHONE SYSTEM Filed Aug. lO 1920 s sheets-sheet W Aff);

Patented May 6, 192,4.

UNITED STATES PATENT JOHN DAVIDSON, JR., 0F TRENTON. NEW JERSEY, ASSIGNOR vTO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application led August 10, 1920. Serial No.` 402,631.

To all fio/wm t mag/vconcern:

Be it known that I, JOHN DAVIDSON, Jr., residing at Trenton, in the county of Mercer and State of New Jersey, have invented certain Improvements in Telephone Systems, of which the following is a specification.

This invention relates to telephone systems and more particularly to systems in which the signals for a plurality of trunk lines extending .between widely separated offices are controlled over a single signaling path common to such trunk lines.

Heretofore some systems of this cliar-acter have been arranged -for manual .trunking only and haveemployed at oppositeends of the signaling path, switching means for teinporarily rendering the common signaling path individual to the various trunk lines served thereby. This individualizing apparatus comprises means for translating into codeY signals the signals initiated by the different trunk lines, means for transmitting over the signaling path thecode signals which are individual to the trunk lines, and means for receiving and translating the code signals into signals individual Y to the respective trunks.

It is desirable to arrange the trunk circuits so that the incoming terminals thereof may be extended automatically to idle responsive means without sacrificing the effi-V ciency of the trunk circuits for speech transmission. It is therefore the object of the present invention to provide improved signaling means for systems of this character .by means of which code impulses are transmitted over a common signaling path forV controlling the associationA of vresponsive means with the incoming end of any one of a plurality of trunk circuits.

For the attainment of the object ofthe in-` vention, there is provided at the originating end of the trunk lines and associated signaling path, apparatus individual to each trunk line vresponsive to the seizure of a` trunk, for setting kup and transmitting a code of impulses over the common signaling path. These impulses are received at' the.

terminating end of Vthe signaling path. and translated into a switching impulse for starting up a plurality' of trunk finding switches for associating responsive .means with the trunk taken -for'use at theoriginat-y ving end af the signaling path.

Apparatus individual to each trunk line is also provided at the terminating end of the trunk lines and associated signaling path for setting up and transmitting over the ycommon signaling path codes of impulses which are received at the originating end of the signaling path and translated into signaling impulses for controlling the operation of a supervisory signal associated with the outgoing end of the toll trunk taken for use, this supervisorysignal being arranged yto operate as soon as the responsive means has been associated with the terminating end of the trunk circuit which has been selected for use,r and to cease operating asl soon as the responsive means transmission.

The invention may be more readily Linderstood by reference to the following description considered in connectionwith the accompanying drawing in which Figurey l yshows thev calling end of acord circuit at for associating responsive means with the terminating end of any one of a plurality of toll trunks; and Fig. 3 shows a receiving and translating mechanism associated with the' distant kterminating. end of the signaling path for receiving code impulses incoming overv the signaling path and for controlling the individual relays of Oftrvnks- 'f Figs. 1,v 2 and 3 arranged with Fig. 2 at the associated group the right of Fig. 1 and Fig. 3 beneath Fig. 2 shows so much of a complete organization of circuits as is necessary to illustrate the manner in which a connection may be established from a toll operators cord circuit in an originating oflice X to responsive means 220 in a terminating oflice Y.

Referring to the drawings, there is shown a toll trunk line L comprising two talking conductors extending from the originating office X to the terminating oiiice Y. At the originating office X, there are provided a plurality of toll cords one of which is shown at F, by means of which a connection may be established with the trunlr line L. The trunk line L may terminate in the oiiice Y in any connecting means desired such as a selector switch, a plug, or in a jack appearing before an operator and also terminates in multiple terminals appearing before a plurality ot' nder switches, one of which is shown at K, by means of which the trunk line may be connected with an idle responsive means 220.

The supervisory signals for supervising the association of the lincler switches K with the terminating ends of the toll trunks and for apprising the originating operator that such association has taken place, may be controlled over a single signaling path common to the trunk lines and comprising a conductor Q extending from the originating ofiice X to the intermediate otce Y, which path is shown as having a grounded return. The signaling conductor is arranged in a well known manner for duplex operation for which purpose there is provided at the ends of the conductor, artificial balancing lines AL and differentially balanced

relays

25 and 25. Each end of the common signaling conductor Q is connected with a commutator for sending and receiving signals. These commutatore are preferably of the well known start-stop type of distributors employed in'connection with printing telegraph systems. Such commutators are disclosed in the Patent No. 1,387,284 to MacDougal and MacPherson, issued August 9, 1921.

The commutator at office X comprises a sending distributor S for transmitting signals over the conductor Q, to the oliice Y, andl a receiving distributor R indicated by the dotted rectangle and of exactly the same construction as the receiving distributor R shown in F ig. 3 for receiving signals tran-smitted over conductor Q from otlice Y, and similarly the commutator at the oflice Y comprises a sending distributor S shown in the dotted rectangle and of exactly the same construction as the sending distributor S shown in Fig. 1 and a receiving distributor R', for receiving signals .from the oiiice X over the conductor Q These commutators at both offices X and Y are of the same construction and a description of the sending commutator S and of the receiving commutator R will be suiiicient. The sending and receiving distributors S and R each comprise a series of stationary rings, some of which are continnous and others segmented, and a common shaft on which are mounted brush arms normally held from rotation by the respective larmatures of two separately controlled release magnets. The outer end of each brush arm is insulated from the inner end so that each brush arm controls two separate groups of circuits. Between the common shaft and each brush arm there is provided frictional clutchmechanism (not shown) by means of which the constantly rotating shaft, causes the rotation of each brush arm when released. The face of the sending commutator S is stationary and is provided with a sending ring 1st, a restoring segment 71, a start segment S, and individual sending segments l to 6 inclusive for controlling the signaling impulses over the signaling conductor Q, and with a common ring 15 and segments 16, 17 and 18 for controlling local circuits. The face of the receiving distributor R is also stationary and provided with a common receiving ring 19 and individual receiving segments 21 to 26 inclusive for selecting a circuit according to the code of signals received over the signaling conductor (d, segments 27 and 28 through which the selected signal receiving circuit is completed, segments 29 and 30 for controlling the circuitoif the associated release magnet BRM and a ring 31 and segment 32 for controlling a local circuit.

At the originating otlice X, the common signaling conductor Q is connected to the common sending segment 14;, while the noi'- mal contact of the differential polarized rclay 25 is connected with the common receiving segment of receiver R, corresponding to segment 19 ot receivei1 R', and the alternate contact is connected with the segment of distributor R which corresponds to segment 29. of distributor R. When relay 2. is operatively energized, the release magnet of the receiving distributor R is energized to release the brush arm of the receiving distributor. At the terminating oftice Y, the conductor Q is connected with the common sending segment of sending distributor S which corresponds with segment 14 of sending distributor S while the normal contact oi' the differential polarized relay 25 is connected with the common receiving segment 19 oi" the receiving distributor R, and the alternate Contact ot this relayY is connected with the segment 29. `When the relay 25 is operatively energized, the release magnet BRM is energized releasing the brush arm 10.

The codes of signalstransmitted over the common signalingv conductor Q, by the sending distributors S, S are determined by the polarity of currentl connected with the individual sending segments 4ofthe respecthe brushes of. automatic selector switches, the selector switch which is associated with the distributor S being shown in- Fig. 1 and.L

designated Gr. These automatic x selector switches are common to a plurality of toll trunk lines andare each provided with SQ y I the trunlrs, the polarities connected withthe brushes a to h inclusive mounted upon a single shaft driven by. a motor magnet' MM initially cont-rolled by start relay 100 con-VA nected in the start conductor or start lead.,

ST common 'to a group of trunk flines. Brushes 0 to h inclusive-are connected directly with the respective. individual lsending segments 1 to. 6 inclusive of .the sending y be utilized, there are provided at the, oiiice distributor S. Brush a yisconnected with VVone lwinding of stop` relay 101y which con-v trols the circuit of the ,motoiLmagnetQMMf and the energization .ofthexrelease magnetY SRM of thesending distributor S. ."Brush b is connected with a vcontact of .relay 102'-for y the purpose of assistingin the control ofthe., p

relayconnected with the corresponding inswitch as will moreV fully appear hereinafter.

Relay 102 and-release relay 103..asso`ciated with the automatic selector switch G are consons which will more fully hereinafter appear. A plurality of contacts equal to twice the number of toll trunk lines to which t-he selector switch Gr is common isassociated with each brush. The contacts associated with the different brushes are mounted at allotted to each trunk line are connected to relays individual to and associated-fwith :the

,outgoing end of the trunlrline. The trunk line L has been shown associated fwith the first two contacts of each ylevel of switch G. As shown. relays individual to the outgoing end of this trunk line .are connected. by means of individual signal control .leads 104, 105 and restoring leads 106 and v'107 withthe allotted contacts accessible totheffbrushes af.

and Z), signal control leads \104.and' 105 being .connected to the respectiveA first` and.\second contacts of thelevel tok which brusheashas l I Lwillbe-.moreffully understood from the dei. access, and .restoring conductors .1.06. and.107

f similarly: connected with theselector switch G. The automatic selecting. switches nare? vprovided Awith' sufficient contacts fto accommodate. 30 trunk lines. Tojtlie. ,contactsgof I the levels to which' brushesc/"toi'hhave y'ac'v Icess,fall 'itted to the v`respective' trunk lines,

are Vconnectedsources of current of positive or negative potential so as to provide distincftive co-de, signals for each of the 30 trunlr lines.

individual sendingsegments of the sending distributor being'determined in exactly the same kmanner as heretofore described incon- .-nection'withy the selector switchy G.

, In orderthat the signals transmitted from the originatino' ofce X of the send-ingv distributor S anc received at the ofiiceY may six locking Lrelays 41 to 46 inclusive having energizing windings connected' with the VVrespective individual l receiving segments 21 l.to-26,-`of the receiving distributor R. When a negative `impulse is transmitted from a particular individual -sending segment' the Qdividual receivin segment willbe energized and :locked -up. `clays 41 to 44 control a plurality of receivingl and selectingrelaysy f 50 to64-inclusive which co-operate with relay 45v to select a signal control-circuit individual to a particular trunk line, while relay .46 controls the polarity of current connected with the selected signal control circuit. The .individuali signal control circuits are con- .nectedwith contacts of relaysj'to 64-in elusive. "Similar equipment is provided -at theoriginating oiiice X for utilizing the signals transmittedr from theterminating office,.-los

Y over ytheicommon signal conductor Q and 4which ,is.-des ignated bythe dotted rectangle R.

The finder switch K shownin 2 is of `'thejwell known rot-ary stepfby-step type and 4,is employed Itoconnect a-responsive means indica-ted by the 'dotted-rectangle 220- with l.the-incomingend ofatoll trunk line L. @This responsive meansmaybe of any deysired character,I for example, an impulse repeater such as described in my copending .application l.Serial No. 402,632, filed August 10,1920. 4 y

" Having in mind this `brief description -of the-,apparatusof' .the system yshown in the drawings, itf-is. thought that.the invention .scriptio-Ii. ofthe operation offthe. system shown, and )therefore a \description ofthe Amethod of extending. aconnection fromA the Y.tollsoperatos `cord circuit F over toll trunk ;`line..L; ,to the. responsive. means-220 shown lil 1.Tl1e operaton-at,..the`- orginatingoiice .in'lesponsegtdalcall incoming toherfpositicn F in the jack J of the idle toll trunk L which is selected by testing in the well-known manner. A circuit is now established extending from grounded battery through the winding of marginal sleeve relay 118, over sleeve conductor 119, through the sleeve contact of plug P, the sleeve contact of jack J, the winding of relay 108 and thence to ground through the winding of marginal relay, 109. Relay 108 energizes in this circuit7 but owing to their marginal nature relays 109 and 118 do not energize atthis time. Relay 108, upon energizing, closes a circuit for relay 115, which circuit may be traced from grounded battery, left armature and back Contact of relay 114, winding of relay 115, frontfcontact and armature ot relay 108 to ground, and also closes a circuit for relay 110 which circuit may be traced from grounded battery through the inner left-hand armature and back contact of relay 111, the winding of relay 110 and thence to ground through the front contact and armature of relay 108. Relay 110 upon energizing closes a locking circuit for itself extending from grounded battery through its inner left-hand armature and front contact, the winding of relay 110 and thence to ground at the armature and front contact of relay 108. Relay 110 also closes an energizing circuit for relay 111 which may be traced from grounded battery through the outer left-hand armature and front contact of relay 110 and thence to ground through the left-hand winding of relay 111. Relay 111 upon energizing closes a locking circuit for itself extending through its inner left-hand armature and front contact, and opens at the back contact of this armature, the initial energizing circuit of relay 110.

Upon the energization of relay. 111, ground is connected to the start conductor ST over the intermediate left-hand armature and front contact e of relay 111, the right-hand armature and back contact of relay 112, and the right-hand armature and back contact otrelay 113, and groundis connected to signal control conductor 105.. over the outer lett-hand armature and front contact of relay 111, the outer right-hand armature and i'ront Contact oit' relay 110, the lefthand armature and back contact of relay 112 and the outer left-hand armature and back contact of relay 118.

Relay 100 now energizes'overconductor ST and closes a circuit for the motor magnet MM extending from grounded` battery throughthe armature, contact and winding of magnet MM, the left-hand armature and back contact of stop relay 101 and the front contact and armature oi' relay 100. Motor magnet MM upon energizing in this circuit advances the brushes of the selector switch G over their respective levels of contacts until brush a: finds a grounded vconductor 105 corresponding to the toll trfunlrwhich has been taken for use by the toll operator.

Assuming that the conductor 105 corresponding to the toll trunk L is the irst grounded conductor to be encountered by the brush a, a circuit is established for the stop magnet 101 extending from grounded battery through the left-hand winding of this stop relay, through the brush a over conductor 105, and thence to ground as previously traced rat the outer left-hand armature of relay 111. The stop magnet 101, upon energizing, opens the circuit of the motor magnet MM and thereby arrests the movement of switch G. Relay 101 also closes a locking circuit for itself extending from grounded battery at the armature and back contact of release relay 103 through the inner right-hand armature and front contact of relay 101 and the right-hand winding thereof to ground. Relay 101 also Acloses a circuit for release magnet SRM of the sending distributor S which circuit extends from grounded batteryV through the ring V15, the inner brushes on the brush arm 9, segment 16theront contact and outer right-hand armature of yrelay 101 and thence to ground throughthe windingof the release magnet SRM. The attraction of the armature ot release magnet SRM upon the energization thereof, releases the brush arm 9 which is thereupon rotated through a complete cycle, at the end of which the brush arm is stopped in its normal position. rlhe brush arm 9, in being rotated, iirst engages start segment s thereby connecting positive current with the common signaling conductor Q.

Brushl arm 9 then' moves beyond segment 16 thereby opening the energizing circuit of, and causing the deenergization of release magnet SRM which restores its armature to normal position preparatory to stopping the brush arm when it reaches its normal position. Upon the assumption that the switch Gr stopped with its brushes in engagement with the first of the two contacts in the several levels allotted to trunk line L, it will be noted that positive current is connected with such first contacts of levels c, d, f, g and h, while negative current is connected with suchftirst contact of level e. `When the inner brushes on brush arm 9 enc gage segment 17, a circuit is closed extending from battery through ring 15, the inner brushes on arm 9, segment 17 and thence to ground through the winding of relay 102. This relay upon energizing closes a circuit extending from grounded battery through the. armature and back contact of relay 103, the armature and front contact of relay 102 over brush b of switch G, conductor 106, winding of relay 113, right-hand armature and back contact of relay 112 and thence to ground through the left-hand intermediate armature and front contact of relay 111. Relay 113 venergizes in this circuit-.and at its inner left-hand armature establishes av contact opens the circuit extending ,over

conductor 105, and at its right-hand armature and back contact opens the starting 1 conductor ST.

As the brush arm 9 successively moves its-'u brushes over the individual sending V,segments, 1 to 6 incluisve, currentsources of the po-larity connected with lthese segments are successively connected tothe conductor. Q. When the brush arm 9 .moves :its p 'necting a holding aground to the conductor brushes out of engagement with segment 17, the energizing circuit of relay 102 y,is s opened and upon the engagement of the. in.-. ner brushes on brush arni9 with segment.

18, a circuit is established for 'release relay 103, which extends from groundedbattery through ring 15, the inner brushes onl arm 9, ,segment 18 and thence to ground through the winding of relay 103. Relay 103, upon its energization, opens the locking circuit of relay 101 whereupon this relay releasesn As the brushes on arm 9 move out. of engagement with segment 18, release relay 103'` is deenergized. When the brushes on `brush arm 9 engage the restoring segment r, current of negative polarity is connectedwithlA the common signaling conductor Q and the selector switch G is now in condition to be seized by another trunk since the trunklineA L is now disconnected therefrom-and the sending distributor S is in normal condition.

Y, over a circuit extending' fromV positive battery through segment s, theouteryset of.vl brushes on arin 9, the common sending ring 14, and the junction point between the wind,-1 ings of differential polarized relay` 25, then'` by one path through the lower winding of relay 25" and artificial line AL to ground, and by another path through the upper winding of relay 25, conductor Q, both windings, of the differential polarized relay 25=and` the artificial line to ground. The operationA of relay 25 establishes a circuit extending; from grounded battery through the alter nate contact of relay 25, segment 29,l the outer set of brushes on arm 10 ofwthere-` ceiving distributor switch R', segment 30` and thence to ground through the winding of release magnet BRM. The attraction of the armature of the release magnet upon the. energization thereof .releases the brush arm 10 which is thereupon rotated through a complete cycle, at the yend of whichtliebruslr arm is ,-.stoppeding-its normal positions` As the bris'h-arnijlOmove's its brushes out of engagementfwitlsegments 29"."and 30,* vthe circuit extending through 'the Winding of rel lease'ma'gnet RRMiis opened, and the magl net, 4fdeenergiz'es permitting the 'restoration of its armature to normal position preparatory to `stoppiiig'ffthe brusharm 10 when yit reaches its normal position. When the brush arm -10fmoves its inner set ofbrushes into enga,gefmerfit"with,they Asegment 32, a circuit is established extending ,from grounded battery, through the ringg31, the inner set 'of brushes-on brush?arm.y 10, segment `32 and thence to vgrou-ndwth/rough the winding yof relay 82. Rel'ayw82fthereupon energizes'con- Y 83,through51fits armature and front contact, whichconducton is .connected in parallel to f the lockingcircuits of vrelays 41 to 46 inclu- -sivel` The armatureofthedifferential polarized relay/25"'l`-remains` in itsalternate posiltion'asglongas positive `current. is connected with theother end-fof the conductor Qk and moves to its normal position whenever,

negativeI current is connected with the other end of" conductor Q."

Thev brush arms 9 and 10are-rotated'syI1-- chronously, and `while brush arm 9 positions itsbrushes-in engagement with segment 3 of the Sending .distributor S to which negative f current is Aconnectedythe armature rof relay 25 moves tof'its lnormal position and brush w ,arm 10 positions itsbrushesin engagement with the-.-recei.ving @segmentl 23. Relay 43 is thereuponenergized over. a circuit extendw ing from grounded battery through vtheno'r-k mal contact of relay25, segment 19 lof the .distributor=R-, the outer setv of brushes on brusharm 10,- segmentv 23 and thence Vto ground A-throughthe lower .winding` of relay ,43. Thisr relay, upon energizing, locks :itself-.to the'. grounded conductor 83, through- `its' upper` winding and its vupper `armature contacts. At-i'tslower yarmature and'front contact, relayA3-closes a circuit extending from groundedbatterythrough the windingsl n of relaysg52 and-fll'which thereupon energize.. Whenfthef-brush arm' 10 `positions its brushes upon the.4 segments 27 and 28, just prior-to reaching .itsv normal position, a cir-` cuitisestablished extending .from grounded` negative battery through the lower armature and back'contact of relay 46, through segment27, the outerset of brushes on brush arm 10,'seginent 28, theslower armature and lback contacty of relay'45, the'lower varmature and back. contact offrelayy 50, the'lower armature and front contact of relayV 51` theupper armature andflback contact of relay 53, the upper armature and back contact of relay 58,

thence 4overaconductory 300 'Y and to ground and iight-handwindingof relav 201. f As soon asbrush'" arm-10 moves-its brushes be- `throughqthe left-hand winding. .of relay 200 n Cdl yond the segments 27 and 28, the circuit eX- tending through the winding of relay 82 is opened and this relay deenergizes, opening the locking circuit of relay 43 and thereby the circuit through the windings of

relays

51 and 52. The circuits of the receiving distributor R are now in normal position in readiness `for the receipt and translation of other code signals. It is to be notedthat during the rotation of the receiving distributor, relays 41, 42, 44,45 and 46 were not energized inasmuch as relay 25 was holding its armature against its alternate contact at the time the brushes on switch arm 10 were passing over segments 21, 22, 24, 25, and 26 connected respectively to these relays.

Relay 200 at the terminating office Y upon energizing over the circuit tracedr through conductor 300, closes a locking circuit for itself extending from grounded battery through its right-hand .winding and to ground through its inner right-hand armature and front contact. The energization of relay 201 is without eiect at this time and this relay deenergizes as soon as the receiving distributor'R reaches normal position and opens the circuit over conductor 300. Relay 200, upon energizing, p also bridges 'the polarized relay 202 across the incoming end of the toll trunk line L, over a circuit extending through the outer armature and Jfront Contact of relay200, and at its inner armature and front contact closes a circuit extending through the right-hand armature and back contact of relay 201, and through the winding of slow release relay 203. The energization of relay 203 is without a function at this time. A circuit is also established from battery at the righthand armature. and back contact of relay 221, through the winding of relay 222, conductor 223 and thence to ground at the inner armature and front contact of relay 200.

Relay 222 energizes in this circuit it relay 221 is at the time deenergized, andcloses a circuit extending from grounded battery through the winding .of starting relay 224, the armature and front contact of relay 222, and thence through the left-hand armature and back contact or" relay 225. and resistance 226 to ground. .Selectable potential is also connected over the circuit above traced to the lowermost bank contact 227 of inder switch K.

Upon the energization .of relay 224, a circuit is closed through the motor magnets 228 of all finder switches whichvare at the time idle. A circuit for the motor'magnet of finder switch K shown in Fig. l2, may be traced from grounded battery through the motor magnet 228, the armature and back contact of this magnet, the outer right-hand armature and back contact of stop relay 229, and thence to ground at the armature'and front contact of relay 224. The finder switches which are started will continue to move their brushes over their respective banks of contacts which are multipled to the thirty trunks of the group to which these finders are assigned until one of the inders positions its brushes upon Lthe sct of bank contacts individual to the trunk line L which has been taken for use. Assuming that the switch K is the first finder switch to engage these contacts, a circuit will be established from grounded battery connected through the circuit previously. traced -to the bank contact 227, thence over brush 230 and to ground through the winding of stop, relay 229. Relay 229 energizes in this circuit opening at its outer armature and back contact the circuit extending through motor magnet 228, and at its inner .armature and front contact closes a circuit .extending from grounded battery through the winding of relay 231 and thence to ground through the inner armature and front contact of relay 229.

Relay 231 upon energizing connectsthe responsive means 220l over itsv armatures and front contacts, brushes 232 and 233 of finder switch K, contacts 234 and 235 with which they are in engagement, thence over

conductors

236 and 237, through the inner and outer left-hand armatures and back contacts of relay 221 to the tip and ring conductors of the toll trunk L. A circuit is also closed at this time from grounded battery through retardation coil 238, the upper armature and front contact of relay 231,

brush 232,' contact 234, conductor 236, the

inner armature and back contact of relay 221, the inner armature and back contact of relay 205, the upper right-hand winding of repeating coil 214, the winding of polarized relay 202, the outer armature and front contact of relay 200, the lower right-hand winding of repeating coil 214, the outer armature and back contact of relay 205, the outer left-hand armature and back contact of relay 221, conductor 237, back contact 235 of finder switch K, brush 233, the lower armature and front contact of relay 231, retardation coil 239 and thence to ground through the winding of relay 229. A circuit is also established at this time for relay 225 which circuit may be traced from grounded battery through the right-hand armature and back contact of relay 221, winding of relay 225, bank contact 240 of nder K, brush 241 and thence to ground through the inner armature and front contact of relay 229. Relay 225 upon energizing opens the circuit of relay 224 which, if

there are no other incoming calls on other trunks of the group at this time, will deenergize opening the starting circuits of all other finder switches which have been started to hunt for the calling trunk.

When relay 231 energized and established a circuit through the winding of polarized,Y

relay 202, relay 202A energized in such a man@ ner as to move its armature into engagement with its lower contact thereby closing a circuit for relays 207 and 208 and slow releasing relay 2.06. 4 slow-to-energize and to diagrammatically indicate this on the drawing, said relay is shown with an arrow passing through its.

armature pointing in the direction in which the armature slowly moves. shown on the drawings with an arrow 'pointing in the opposite direction are slowto-v release. The circuit 'for relay 206 may be traced from grounded battery through the Winding ot this relay, the armature and lower contact of relay 202 and thence to` groundl at the inner armature and iront contact of the relay 200. relay 207 may be traced from grounded battery through the winding of this relay, the normally closed make-before-break armature contacts o this relay, the right-hand armature and back contact of relay 209, the outer right-hand armature and back contact' of relay 210, the armature and lower contact of relay 202, and thence to ground at the armature and front contact of re-KV lay 200. Relay 207 upon energizing closes a` locking circuit for itself through its iighthand armature and make contact, the outer left-hand armature and bac-l; contact of relay 211 and thence to ground over the circuit previously traced through the armature and lower contact of relay 202. Relay 207 thus` remains under the control of relay 202 until relay 211 is operated. The circuit of relay 208 may be traced from grounded battery through theiwinding of relay 212, the outer lett-hand armature and back contact of relay'209, the winding of relay 208, the break contacts of its inner right-hand armature, the left-hand armature and back Contact of relay 207, the right-hand armatnreand i back contact of relay 209 and thence to ground over the circuitJ previously traced through the armature contacts of relay 202. Since relay 207 is slightly slow to energize, the circuit of relay 208 is established before relay 207 energizes to open its left-hand armature contacts. Relay 208, upon energizing, in the circuit previously traced closes a locking circuit for itself extending through the winding of the start relay 212 of sending distributor Sl which relay corresponds to relay 100 of the sending distributor S and thence through its own winding and the make contacts of its inner right,- hand armature, to ground.

Relay 208, upon enerigzing, closes a circuit for relay 220. extending from grounded battery thro-ugh the winding of relay 220 the left-handl armature and back contact of relay 219 and thence to ground at the in-` ner lleftehand armature and `front contact Relay 207 is slightly" Other relays s The circuit of of relay 20,8. circuit a'nd 'closes a locking circuit for itself extending through its armature and front contact, through the windingof relay 219, through the inner right-hand armature and Relay ,220, energizes, in, this L back contact of relay 210, and to ground g at the inner armature and front Contact of relay 200. Relay219, however, does not energize in this circuit `since its winding is shunted by ground at the armature contact of relay 208. The energization of the .start rela-y 212 of the sending distributor starts Y up the ysending distributor in a manner eX- actly similar to the starting of sending distributor- S hereinbe'fore described,` and causes the transmission of a code of signals over the conductor i Q, and through` the polarized relay 257; The sending distributor Sffmakes a complete revolution and after leaving normal position closes a circuit over conductor 106 throughfthe winding of relay 209, which relay upon energizing` opens n the locking circuit of relay 208.V Relay 207 remains lockedthrough the lower; contact of relay l202. The sending distributor Sfjis restored to normal and is ready `for the transmission oflanother code of impulses. The circuit o-ver conductor 106 is closedat thesending `distributor S in exactly the same manner as the-.circuit over conductor 106 isclosedat the Scndingdistrib-utofr S.

The code of impulses is received by the receiving distributor R'and translated ina mannerI exactly rsimilar to the operation of the receiving distributor R previously described and causes Ithe closure of a circuit over `the. conductor 120 to ground through the rightehand` winding of relayv 114. Relay 116 does not, operate at this time over conductor 120 since its circuit which is normally `in parallel with the winding of relay y 114 is opened at this time vat the armature and back contact of slow releasing relay 115. Relayv v114 upon energizing` in this. `circuit closes a locking circuitfor itself extending from grounded battery through its lefthand armature andifrontcontact, its lefthand winding and thence to ground at the l P, conductorv119 and Vwindingof marginal relay 118 to grounded battery.' Theconnection of resistance 117 parallelwithether.l

windings of relays 108 and 109 changes the resistance of the sleeve circuit sufficiently to permit the operation of marginal relay 118 of the toll cord circuit F, which relay, upon energizing, closes the circuit of the lamp 121, which at this time serves to give the toll operator a signal to apprise her of the fact that the finder switch K has associated the responsive means 220 with the incoming end of the toll trunk line L.

In response to the signal given by lamp 121, the toll operator proceeds to operate the responsive means 220 over the toll trunk L. This responsive means may take the form of an impulse repeating device for repeating impulses out over the incoming end of the trunk circuit L at the oflice Y, as fully set forth in the copending application hereinbefore referred to or may be of any other desired form such as an operators head set or indicating mechanism. Since, however, this specific form of the responsive means does not constitute an essential part of the. present invention, further reference to such operation is not deemed necessary herein. Having operated the responsive means 220', the operator initiates the release or' the finder switch K to disconnect the responsive means from the trunk circuit L by releasing the key 122. This key which the operator depressed at the time she operated the responsive means 220', closed a circuit extending from grounded battery directly to the sleeve conductor 119 in parallel with the winding of relay 118 which so increased the flow of current over the conductor that the marginal relay 109 energized. Relay 109, upon energizing, closes a circuit for relay 112 extending 4 from grounded battery through the winding ofrelay 112 and thence to ground through the armature and front contact of relay 109. Relay 112, upon energizing, opens the locking circuit of relay 113 permitting relay 113 to deenergize thereby connecting start conductor SlT and impulse control conductor 105 to the back contacts of the armatures of relay 112.

Upon the release of key 122, the circuit previously traced over sleeve conductor 119,

in parallel with the winding of marginal re-v lay 118 is opened and relay 109 thereupon deenergizes opening the circuit of relay 112, which upon deenergizing connects the start conductor ST, and the impulse controlling conductor 105 as previously described to ground at armature contacts of relay 111.

ln response to the connection of conductor ST to ground, the selector switch G is started to nd the trunk line which is in use, and sending distributor switch S- is started to send a code of impulses over the signaling path Q, in exactly the same manner as described in connection with the original seizure of trunk line L. At the oiiice Y, the code of impulses is received by the receiving distributor R and translated into a momentary impulse of current over conductor 300 individual to the incoming end of trunk line L for causing the energization of relay 201. Since, at this time, relay 200 and slow releasing relay 203 are energized, relay 201 at its left-hand armature and front contact closes a locking circuit for itself extending through its left-hand winding and to ground at the armature and front contact of slow reand front contact of relay 200. The operation of slow release relay 215 closes a circuit for slow release relay 216 which in turn closes a circuit for slow release relay 217 and relay 205. The purpose of the slow release relays 203, 215 and 216 is to prolong Y the interval during which relay 205 is energized. The function of relay 205 is to transmit ringing current from the intermediate oice Y to the terminal oiice.

The energization of relay 216 also closes a circuit extending from grounded battery through its inner left-hand armature yand front contact, through the winding of relay 221, thence over conductor 223 to ground at the inner right-hand armature and front contact of relay 200. Relay 221 upon energizing closes a locking circuit extending from grounded battery through its righthand armature and front contact through its winding and thence to ground over conductor 223. At its inner and outer lefthand armatures, relay 22'1 disconnects the trunk finder switch K and its associated responsive 220 from the trunk L and extends the 'toll trunk L to the windings oi relay 242, which relay may be employed for any desired apparatus such as controlling a signal at the terminaating end of the trunk circuit. Relay 221 also opens the circuit icc previously traced through

relays

222 and 225 causing these relays to release. The release of relay 222 has no effect upon the circuit at this time. g Relay 221 also opens the circuit of relay 229 which in turn opens the circuit of relay 231, releasing the toll line finder K and rendering this finder free to be used in other connections.

'The energization o'li relay 217 connects ground through its left-hand armautre and front contact to the windings of signaling

relays

206, 207 and 208 to prevent any signal from being sent back over the common signaling path by the release of relay 202 during the time that relay 205 is energized.

At the time the toll line finder K was disconnected from the toll trunk line L upon energization of relay 221, relay 202 was 'operated to close its upper contacts by reverse current flowing over the conductors of trunk y L through the winding of relay 242. After an interval of time during which time the slow releasing relay 206 releases due to relay 217 opening the ground connection to relay 206 as previously described, a circuit is closed through the winding of relay 210 which may be traced from grounded battery, through the winding of the start relay 2121 of sending distributer S, the outer left-hand armature and back contact of re` lay 209, the inner left-hand armature and back contact of relay 209, the winding of relay 210, the outer right-hand armature and back contact of relay 208, the righte hand armature and front contact of relay 219, the break contacts of relay 206, the upper contact and armature of relay 202 and thence to ground at the inner armature and front contact of relay 200. Relay 207 is released when relay 202 opens its lower contact. The operation of the' startA relay 212 o the sending distributor S as has already been described starts the sending distributor S for transmitting a code of impulses over the signaling path Q. The lenergization of relay 210 through itsfleft-hand armature and front contact connects ground to the conductor 104 for stopping thebrushes y.of the selector switch associated withthe Ysending distributor S upon the second contacts ofthe banks to which they have access, which contacts are individual to the trunk line L. The energization of relay '210 also opens the locking circuit which has heretofore'been established vfrom battery through the winding, armature and front contactoi' relay 220, the windingv of relay 219,*thev inner right-hand armature and back contact of relay 210 and thence to ground atthe inner armature and front contact' of relay 200.. IAs soon as 4the `code of signals has.

been transmitted over conductor Q, aumomentary impulse is received from sending distributor S', over the conductor 106 ashereinbefore described 'for energizing the relay k209 which relay opens the circuit of relay 210, leaving the circuits at the incoming end of the trunk line in condition for the transmission of other signals.

The receiving .distributor R starting up in synchronism with the sending distributor S causes the locking up of the translation relays associated therewith and, since a code for this particular trunk comprising two positive, a negative, two positive and a negative impulse was transmitted over the signaling conductor Q, a -positive impulse is transmitted from grounded bat,- tery over conductor 120 and to ground through the right-hand winding of` relay 114. This circuit is closed at the receiving distributor R in exactly the'same manner as previously described in connectiony with circuit closed at the receiving distributer R with the exception that since the last impulse of the group is a negative impulse, the relay corresponding to relay y46 is energized to connect positive current relay 118 of cord circuit F thereupon def energizes to extinguish the lamp signal 112 to give the operator a signal that the toll line finder K has been disconnected from the incoming end of the toll line L and that the toll trunkL has been cut through to the apparatus represented at 242.

When'cofinection of the toll trunk line L is no ylonger desired, the operator at the originating yend of the toll trunk remo-ves the plug P of the cordy circuit F from the jack J of the toll trunk, thereby opening the .circuit over sleeveconductor 119,'eXtending through they windings of relays 108 and 109. Sleeve relay 108 now deenergizes opening the locking circuit of relay 110 which upon deeI'iergizin-g` connects ground to the startlead ST forjstarting the selector G. Ground is .also connected to 'the lconductor 104 from the outercrle'ft-.hand' armature of relay 111 over the right-hand'arma'ture and baclr'contacto- `relay-110 andthe selector switch G ylwill,thereforebev arrested 'with its ybrushes 'positioned-upon the second contacts of the levelsto which they have access. The sending distributor -will therefore transmita code lof impulses over the path Q, `comprising 'two positive,I aY negative, .two positive and negative impulses. While these impulsesare being transmitted by the sending distributor S battery is connected over brush b to lead 107, in a manner similar to that in which Vbattery was connected to lead 106, through-,the front lcontact and right-hand armature and right-hand winding of relay 111 to ground. The current throughv the right-hand winding of relay 111 4flows dif-l ferentially with respect to the current throughtheleft-hand winding, and this re# lay therefore releases. The release of relay -111 releases relay 113, and the trunk Lv is then free to be used for other connections. The above impulses are receive-d by the receiving distributor R causing the energization of

relays

43,46, 51 and 52 in thel same manner 'previously described.'-

Just priorr to the return of brush arm 10 of the4 receiving distributor -R to normal 7oy 'y position, a circuit will be closed from positive battery, through the lower armature and front contact of relay 46, segment 27, the outer set of brushes on brush arm 10, segment 28, the lower armature and back contact of relay 45, lower armature and of relay 221 and relay Q21 thereupon deenergizes opening at its left-hand armature contacts, the tip and ring conductors of the incoming end of the toll trunk. The toll trunk isnow in its normal condition and all apparatus associated with the outgoing and incoming ends of the toll trunk and with the outgoing and incoming ends of the common signaling path arein normal position.

What is claimed is:

'1. ln a telephone system, in combination, an originating oilice, a distant oiice, a plurality of trunk lines and a separate signaling path common thereto extending between said offices, means at said originating office for establishing connection with any one of said trunk lines, a rotating switch at said distant oilice for seizing the incoming end of any one of said trunk lines, and means automatically controlled over said common signaling path for initiating the movement or" said trunk seizing switch and causing it to seize the trunk with which connection has been established at the originating oiiice.

2. In a telephone system, in combination, an originating oce, a distant oiice, a plurality of trunk lines and a signaling path common thereto extending between said oiiices, means at said originating oiiice for establishing connection with any one oit` said trunk lines, a group of trunk finding, switches at said distant office for seizing the incoming end of any one of said trunlr lines, and means automatically controlled over said common signaling path for initiating the movement of all idle switches of said group for causing the seizure of the trunk line with which connection hasv been established at the originating oilice.

3. ln a telephone system, in combination, an originating oihce, a distant oilice, a plurality of trunk lines and a separate signaling path common thereto extending between said oh'ices, responsive means at said distant ofiiice, a rotatmg switch automatically,

controlled for associating said responsive means with any one of said trunk lines,

means at said originating oliice for transmitting over the signaling path code signals individual to the dii'erent trunk lines for controlling the association of said responsive means with a particular trunk line, a normally inactive switching device common to the trunk lines for determining the codesignals to be transmitted, and means controlled by a change in condition on one of the trunk lines for rendering the switching device active.

4. In a telephone system, in combination, an originating oiiice, a distant oice, a plurality of trunk lines and a signaling path common thereto extending between said ofiices, means at said originating oiice for establishing connection with any one of said trunk lines, a group .of trunk iinder switches at said distant oliice for seizing the incoming end of anyone of said trunk lines, means controlled over said common signaling path-for establishing a busy calling condition on the incoming terminals corresponding to a trunk line with which connection has been established at the originating oiiice, and means automatically controlled over said common signaling path for initiating the movement of all idle switches of said group for causing the seizure of the trunk line upon whose terminals the busy condition appears.

5. In a telephone system, incombination an originating office, a distant oiice, a plurality of trunk lines and a signaling path common thereto extending between said of# iices, means at said originating oice for establishing connection with any one of.

said trunk lines, means at said originating oiiice for transmitting over the signalingy path codes of impulses individual to the .different trunk lines, a normally inactive switching device common to the trunk lines n for determining the codes of impulses to be transmitted, means controlled upon connection with' one of said trunk lines for rendering the switching device active, means at the distant ofice responsive to said codes of impulses for establishing a busy calling condition on the incoming terminals of the trunk line which has been taken for' use, a iinder switch for establishing connection with the incoming terminals ofany one of said trunk lines, and means automatically controlled over` the signaling path for i initiating the movement of said switch.

6. A plurality of transmission lines, a signaling path common to and independent of said lines, an automatic switch having movable terminals adapted to be automatically associated with any one of said lines, a source of impulses, means for transmit-v ting impulses over the signaling path, and means responsive thereto for identifying a selected line and for automatically operating the switch to associate the movable terminals thereof with said line.

7 A plurality of transmission lines, a signaling path common to and independent of the lines, an automatic switch `having movable terminals adapted to be automatically associated with any one of said lines, a source of impulses, an intermittently operating device for transmitting the impulses over the signaling path, and means responsive thereto for identifying a selected line and for automatically operating said switch for associating the terminals thereof with said line.

8. In a telephone system, an originating office, a terminating oiiice, a plurality of trunk lines interconnecting the ofiices, a signaling path common to and independent of the lines, an automatic switching mechanism having movable terminals adapted to be automatically associated with any one of said trunk lines, means at the originating oiiice for transmitting a code of impulses over the signaling path, and means responsive thereto for automatically controlling the movable terminals of the automatic switching mechanism.

9. In a switching system, transmission circuits extending between-two stations, a signaling path extending between the stations and independent of said circuits, an

automatic switch having movable terminals adapted to be automatically associated with any one of said circuits, means responsive to a changed condition of any one of said circuits to transmit a corresponding code combination over said signaling path, and means responsive to the received code combination to automatically control the terminals of said automatic switch to connect with a circuit having undergone a changed condition.

10. In a switching system, a plurality of transmission circuits extending between two stations, 'a signaling path common to and independent of said circuits extending between said stations, an automatic switch having movable terminals adapted to be automatically associated with any one of said circuits, means associatedk with each of said circuits at one of said stations for originating impulses, an intermittently operating distributor for transmitting impulses originating with any one of said circuits over said signalingpath to the second station for controlling the automatic switch to connect the terminals thereof with a circuit at which impulses have originated.

In testimony whereof, I have signedr my name to this specication this 7th day of August, 1920.

JOHN DAVIDSON, Jn