US2358529A - Telephone system - Google Patents

Description

Sept. 19, 1944. w. MUYLDOONE TAL TELEPHONE SYSTEM Filed June 5, 1943 2 Sheets-Sheet 2 r v mmm. W 00 E Tu N N n R w w 0 MMS. Jr 2 mm Patented Sept. 19, 1944 TELEPHONE SYSTEM*- g WillianfihMuldoon,;Hempstead,;,andglimoldj l Control Instrumen NI Y.;-a earpqr paabf'Newyarki I g N I Applimatiu'm'June 5, 194s, seria1 No; 483,7:48f'e (o1; fleas)- This" invention relates td improvements' in'tele phone systemsand; hay particular reference to a full automatic inter-communicatingasystem;

An object of" the invention is to provide animproved and-simplified systenrwherein theuse ofrelays individual to each subscribers line is eliminated by having a" linefinder switch in- V dividual to each trunk-circuit employed; which finder, upon preselection of its trunk circuit-in preparation for-receiving a; call to beinitiated'fat anyone of these subscribers stations, is operated until its wipers engage-the terminalsof aline-at which a calling condition exists; where-' upon the finder connects the callingline to said: trunk circuit, and switching" means :common to" the various trunk circuitsdsthenactivatd'to' preselect another and" idle trunkand it'sjassociated finderfor use inestalohshingaconnec tion forasucce'eding call; H r

Another objectjis to providea systenr'wherein' alinefinder in aitrunk circuit is made common to a plurality of subscribers lines; and provided in said circuit withiimprovedmeans to control it line hunting operation and'seizure of xline" upon which a calling-condition exists.

A further object-'istoprovide a trunli'ci'rcuit with a linefinder common toa plurality ci ca-lling lines, which finder has a normal position from which it ismovedin a hunting operation by a relay, als'cyin said trunk circuit; j, which is energized 1 when said trunk; circuit is taken 1 for useyand which is thereafter controlle'df tore-i store said fiIldEI"tOitS'1101111311"ILlOSIllJlOl']; at the conclusion of'a'call.

The inventive "idea involved" is capable" of receiving a variety of expressions a preferred on'e' of' which is-shownin the accompanying'drawings; but it is to be expressly understood'that' said drawings are employed merely "for the :purpose of illustrating the invention as a whole 'and not to define the limits thereof; reference'be i-ng' had to the appended claims for this purpose." 7

In the drawings; V g

Figs. 1 and 2, whena rrangedside by 'side' in vertical" position, illustrate diagrammatically a system embodying the "features of the present invention, the dotted lines extendingbetween various parts of". the apparatus indicating me chanical driveconnections; therefor: v v

"As illustrated in the drawings,.theitrunliicirl cuit is inthe condition existingatthemoment of its preselection" resulting from a" call pre-: viously made over anothertrunk; andis so.pre-j selected for the purpose of; handling .thefnext call. to be initiated,.for exam le; at thef'sfiloscriloers f's'tationi A whichifde sires-a connectiona v y g #11 conductorloo of saidfpreselected trunl aeeprdaneewim the"- present invention; I immediately upon thepreselection of the circgu'it herein shown by the trunk selector or allottr' switch' 'I ;S r' its' 'a'ssociated rotary line fin ers; File/started fr'om a normal-position to seel'r th'e terminals; of a{-subscrili'er sfli'n' o nf whieh a' cal-l w-illloe subsequently initiated-f The-find 'ontinues itsfiunting operation-until o e of -s--wiprs encounters aterminal of a call'm' line;--sucll'-as A whereupon--the fi'nder stops and-the selector-'switch T-f SE ir'nmediatel'y op'e'ratesf-assuming at last' 'one; 'f 'the' other-"trunks servi gthe system is idle; v I select the=latter=trunkfor *th-acall-inltiated subsequently tothat; at sta n A: Iffal'l trunks are-busy at the momen witch T; 1S5 awaits an idle condition onneof hem beforestart j ingdtsi pmsaeeene; operation; Upon receiving a dialing tone? at station Af series- Vof ir'n'pulses are transmittedf toa two rnotion selector-switch s: s2 (Fig; 25 and assumifi tli'eetati' n--B being called toy-be idl a ringing signal' sf'operated at said station, and--'tlie renioval of th'e' telephone thereat from its sw-itclrhool oompl'etesthe con nectionto-station v 1 V individual; tothe--*'tri1nkfcincuit shownj is started 7 established from g-rour-idf at} the trunle selector;

relay I04; which;- is "slow-release; through the, windingofl said relavf wiper and terminal I03; conductor; I052'winding of finder-control relay Hi6; conductor=- I01; uppermost-back contact of 1ew-r 1e se- 1ay11 08 1- and lower back' contact of low-impedancerelay 109' to battery. Relays l 0'41 and: I 06 emaana the operation' of the f ormerf relay prevents further en'ergiza-Z tion of the;slow release stepping magne I"! ll' of' the 'trunkselector: T: S; which would otherwise operate over a circuitextendin'gi from"; ground through; the" self-interruptedswitch I'! l winding of magnetfllfl; conductor H 2; the lower" most backf contact ofrelay-1J0!!!) conductor 113;; and the jcontactj of {relay I 045" to battery: However; since saidfhack' contact is; ow opengsaidcircuit is 1 notjfjestablished" and the wiper 10-2 trunk selectonremainls 'on thef termina select another idle trunlg;

The energization of the relay I06 in the preyiously described circuit, closes another circuit for operating the motor I I4 that drives the shaft bf the line finder L. F. on which is mounted the wipers H5 and I I6 of said switch. The circuit for thus operating the motor I I4 extends from the negative side oflbattery N1," the back con tact of the slow-release, high-impedance relay I I8, motor H4, and the lower front contact of relay I06 to the positive side of battery. The rotary wipers II5, I I6 are started from their normal positions and continue to rotate until the wiper I I 6 encounters a potential on one of its terminals indicative of a calling condition on a .15, V at station A, the subscriber theretat having now removed the receiver from its switch hook; When this occurs, ground is connected to the impulse sender at the station and also to one side of the subscribers line which shall be assumed tobe time said wipers complete a revolution and pass over said positions; During theclosure of said switch ;I I9, it connects ground. to the conductor I05 through said resistance1l20 for the purpose of controlling the restoration of the line finder to normalat the conclusion of the call, as will later appear. Itis also noted that the impedance of relay: I I8 is approximately seven times greater than. that .of relay I09; and, due to; this, said impedance diminishes the current surge and. reduces, to apoint below the audible range, the inductive couplingoccasioned by the line finder wiperspassingover the terminals of a busy line during the hunting operation.

In said hunting operation is evident that the wipersthereof may engage terminalsof one or more busygcalling lines each connected to a busy trunk. Under such circumstances, it becomes necessary to prevent energization of relays I09 and l I8 of the trunk associated with said line'finder andto also avoid the release of relay I09 of thebusy trunk. This is accomplished bythehighand low resistances of said relays and a. seriesline resistance in the busy calling line. Thus, when the wipers of thefinder of the preselected trunk passover the terminals of abusy line relays I09 and] I8, in series, of said of thefiine nhder, it,

finder of said trunk will pass over the busy line terminals. The call at station A now having been initiated,

as previously stated, when the wiper II6 of the line finder engages the terminal individual to said line, voltage is applied to relays I09 and H8 which,*at this time, are not in parallel with relay I09 of a busy trunk, and acircuit is now established extending from battery through the windings of'relays I09 and H8, the upper front contactof; the now .energized relay I0 6, wiper .IIB andthe terminalengaged thereby, resistor I2I, andthrough the impulse sender andupper contact ofswitch hook atstation. A, to ground, The

Y greatervoltage drop acros the high resistance finder engaged with the terminals individual to trunk are momentarily in parallelwiththerelay I09 of the busy trunk. Thislatter, relay is in series with the busy station line resistance and is the only one ofthe two relays I09 and I I8 of the busy'trunk that is energized, as willpresently appear. The parallel condition Of relays I09 and II8 of the preselected trunk with relay I09 of the busy trunk does not, however, result 'in the release of thelatter relay I09 since thetotal re-. sistance of relays I 09 and I II 8 of. the. preselected trunk is several times greater than that of the re lay I09 of the busy trunk so that'the voltage drop in the latter relay, due toshunt'ing, is not sumcientto cause it to reieaseipn the other hand,

I thehigh resistance relay'II8 isadjusted to operate only on the highervoltageiexisting'acrossit when inseries connection with the low resistance relay I I8 will. cause this relay. to energizeand.

thereby, at its back contact, open the operating circuit for the motor H4, and said motor then stops with the wipers H5 and H6 of the line the calling line. Although therelay I09 is in series with the energizing circuit of the relay,

II8, it will not energize until relay II8 has oper ated, at which time the latterrelay short circuits itself through the conductor I22 and its front contact. This action raises the voltage sufficientlyto cause energ'izationof relay I09 through the front contact of relay I I 8, and when relay I09 operates it temporarilyopens, at its lower 1 back contact, the energizing circuit for relays I04 and I06, and establishes a circuit from ground through the winding of. relay I08, and through the middle front contact of relay I09 to battery.

Relay I08 energizes and, at its upper back contact, permanently breaks said energizing circuit for relays. I04 and I06, causing the latter to remain in released condition until the call-is terminated. r

'Afdial tone-is now impressed upon the subthrough the source:200, conductor 20 I, the closed contacts 202 of the selector switch S. S., conductor,

203, the lower back contact of. relay I06, conductor I23, the back contact of relay 204,.conductor 205, the upper back contact of slow-release relay 206', wiper II5 of the line finder, conductor I24, and through the condenser and receiver at .7 battery. thereat to the contact of said relay from whence a circuit extends over the conductor I25, similar to conductor I I3 of the present trunk and leading to an idle trunk, the lower back contact of relay I08 of said idle trunk, the conductor I26 connected to the latter, which corresponds to the" conductor II2, the winding of stepping magnet sesame:

Ho, and its interr pter-I11 t"o=-gr ound:1 Magnet I i 0 is{ energ-ized;causing: its wiper- 102 to' engage terminal 1:21: individiial' tb another Ir pn s trunis-ie busy; relay! 0a tliered'f wni been er'gized; and therefre no circuit will he establi-slied thrbn'gh its-"upper" back -eentact to operate 'initiatesthe operationof" the" line 'firfder associated with said trunk. From the 'foref'goi-ng it will be apparent that if all trunksshonld 'be-busy atfa ny given monienti, all "e; the relays I 08thereof will*beenergized} em; 1315 a; consequence; the energizing circtiit for"the'stepping' magnet H0 7 be opemat the owercontacts-Oran? said relays f I'08fandfthe trunk selector will remain in operativenntil" one Vofsaid back contacts is closed bytherelease of" tl'reassociatedrelay I08 atthe termination of a callover'the'trilnk in which-said relay-is located, 'lherr; the trunk" selector operates, as described; tofindiandipreselectthetrunk whichhasbeconie'idla' Returning now to thecondition where theisub= scriberatstationAreceives the'dia' ltone, the imp' xlse sender "at fsaid station is now operatedby the subscribert'o send'f iinpiilses over the" 'signal= ling circuit to operate the js'electorfsw'rtch' is S; tofl es'tablish' a' connecti'on t' Atfili'S time', relays l08fanj l 09are energized', aiid relay l08,"heing slow toirleas, doesnot de-j energize during j transmission 7' of the jimpulses. Thefirstandfsucceedingjimpulses if any, ofth'e series: cor e ponding: toftl'i'eitens digit off'th calld line causes thesuccessivei elaseia d 'operatien resultsfin theestablish' ent oflann'ergizinhir ciiit fo 'relay zosextending iremf gronndthrough the winningiorise dfreie 'wer' from contact-of rela Ii'lflfanld' the: ii'p'per'fhackhontact. of'ilay ijwtcibatteryqsince relayzne is. -owito release; sm-meme 'enereiz'e d euring transm ssion" or the firstiser es er'mip nsesenditnen rleases'atffthe cdhclilsidn thereof. "In; response to th fi'fst pu szeir an'smttedqrele jme reieesesjeriais again bfiififiedlialidfilflfifl it's perationi -iiirc'tlilfis GS- itemisned ferjthe; vertical; stepping magnet :01 or the selector STSi, ext 'ni irohi ground through the, windingl bfi'mag' iiti201T tne'upper Closed. 'c'oxitaftf'offtlii contact bank; orpil 208, tact'fizca er'relay 20fi'a'ndthe upper front Contact? erire ay "we; to battery, The; en} erg ze timeff;iiaener2t!reseense to the 16: suref'ofi saidfciic f operates itsfarmature' and eye the: sharr'z'lnjcf "the sei f u' t e sive iifipnls'efs'lioiilditherebe more, i; an oneiin tnegjfirstsejries 'aiissthe 'iiiegiietinrte 'b'e Sim:

ne'ntito the? shaft 2.! uiuhtirtn e wip rs-,2 "and .2 zi erneegby, Sara "shaft ar'fas'sociatedf with the ll'iori z ontalgrow er terminals of ithe. switchbank in which'the ilineebefnfcallediis'.located? the ca lled line" B:

i A t first vertical steppir'fgbp'eration or maefierm;

theicamz 2 .1.3"; controlledibyithezishaitni flgohere.

ates tdaopemthef'ccntactsfl0liofitheicontact pile I Zthandtclosethe remaining contactsvzthereinathe opening: or' contacts. 2.0.2; disconnectingzthei dial tone:fr'o'mzthercallingdine: i t Jlpons completioni of: the; transmission:- of? the firstiseries ofiimpulses; ,corresponding to' the tens digitxofz th'e;:ca1led;'line; relay; 206;; releases,. the circuitithereforrbeingtinowi bTrokenaatz thesupper backeontact of;relay;; I09 which now; remains B11? ergizedgawaiting,:the transmissionltofi the second series oftiimplllseszcorresponding ito theunit'edigit of;.the:calledfline When relay 206=-releases;and before: the secondiseriesiof impulses isstarted; the horizontahor: rotary stepping imagnet 2 I5 of thetselector switch-. S.; S. isioReratedvoven-a; circuit v extending from ground through the -.wind ing; of said=magnet thee-now: closed; contacts 2 l fiof the cpntact= pile 2.l 4; the lower. closedcontacts; 2 ofethe: contact pile 208, theeback lcontact .2-I ,8. f relay 208; and the; upper front contact of relay [09410, battery. 7 Energization of themagnetfli in this circuit ecauses. :Shaft '2 l 0;: of; the: selector switch to rotate one step; thereby operating-ewe pilee 2-0 8; i and reverse; the positions-1 of "Tthe: other contacts 2- in said pile in preparation? for receiving thersecond series ofximpulsesr. Theron'eningqof the contacts 2 I1 bygtherlcannflil breaks the above,-

described genergizingi circuitior-zmagnetfl-l 5.- V v -The second series ofiimpulseszissnowptrans-a mittedirom the calling;station;and:v relayg' I09 responds; tOLthGSE impulses :aszbefore, Upon-first deenergizationziofi relay" l09; relay- 206 isiagain energized, as previously. described; andiwhemthe frontcontact. 209iofzisai t relay is closedandirelay; l 0.9 -;is :againxzenergized; an; operating;;circuit fort mag-net; 2l5: is" established: extending' from groiimizthroughi theyvinding of said magnet; cone- .tactsu2l 6. ofrthe pi1e;2l 4, :contactsi22mofatheipile 208., the 'front contact. 209. of relay-'206,.eand:tlie upperfront contactof: relay: l09itoibattery; Mag;

net -2 l5 ithus operatesiinwresponse tothe second: I

series "of impulses to erotate the shaft: 2 ll0;:of:the selector switch so r that the wipers 2l I: and" 2.12 are alsorotated horizontallytoiengagewith the terminals of thecall'ed line in accordance-with the number-of impulses-transmitted inisaid sec! ond series: J Y 1 I I It-w-ill first be assumed that the- 'calledstation B is idle; in which e'vent relay-206, -after a-slight interval, releases at the conelusion of the second series of i-inpuls'esi However; while relay 206 15 still energized," acircuit is established for relay 204 extending from grotmd through the winding thereof, 1 and the-closed contacts 221 -of-rel-ay 20i;

to battery.- *R'elay 204- energizes-and'is thereupon locked ina-'circuit through-it's windingand lower front-contact,the upper 'frontcontact of relay I08 and the lower back contact -.of'-relay-"22-2 to battery. 'Aifterthislocking' circuit;- has been es: tablished; relay 206 thenreleases;- Energization of relay ZMcormects a-ringing--voltag'e to the called line over the circuit-extending from bat"- tery throughthe interrupter-'canrni; the upper front"'contact' of -relay 204; fback contact 224* of relay 20$;upper' back contact-of relay 222;wiper 21 2 pfth'e switch Szf S and the engagedtermina'l 225, to ground through 'the" rin'ger 'and" lower switch hook contactat" station E: A portion of this" ringing voltage is fed back to the receiver ofthe callinjglinethrough the resistor 22B; up e back contact of relay 206? andlinefinder-wiper l'i'ifto th'efcondenser and" receiver at? station A.

Remover of tfi "receiver atthe hailed Station in; response to ithecringingss'ignal closes a path for energizingi:relay. z222 which extends from ground atzthecupper: contact of the switch hook; the impulse sender 'at said station, .resistor- 221; terminal 228 and wiper:i2ll engageduthereby, winding of relay222z-and. their-lower front contact of relay 1 I 09 to battery. EnergizationpL relay! 222v disconnects the ringing circuitifrom. the interrupter cam 223 to the I ringer at" station B and also opens, at its lower-back contact, the holding circuit for relay204 which'there'upon releases; A talking connection between the 7 calling' and'calledlines'is now/established, over the trunk-conductor I through-the wipers-l l and 2l2-of the line finder and selectorswitches, respectively, and the'upper back contacts of relays 204 and 206.--

the called 'linehappens to' be busy' when wipers 2H and' 2l2 of thejselector switch S.-S. engage the;terminals of said line, relay 222 will be energized-in the previously described circuit therefor,-since the pull-in voltage of this relay is low enough to cause it to operate-even when paralleled by the relay H19; of the: trunk connected to-the busy called statiom Relay 206, instead of releasing because'of the idle condition of line B,

will now be locked in a circuit extending from ground through the winding of'said relay,'its lower front-contact, and thelower front contact of relay'222 to battery. 'A busy'signalnow will be connected to thecalling linesfrom' the source 200 through the interrupter-cam 229; upper front contacts of relays 222 and 206, and. fromthence over the conductor [fill-and line finder wiper H5 to the receiver atstation'A. a r .7 .The release of theitrunk arid itsassociated equipment is under thencontrol ofithe calling subscriber so .thatithe replacement of his receiver on lthe-switch hook, either upon receiving a busy signal-i011 at .the: termination-pi a call, has .the effectof restoring the. trunkcircuit to .its idle condition. a; When-5:2 the, receiver is,-. replaced;

ground at the calling station is removed from the terminal Jengaged-xby wiper 1 I16 randjrelay. I09 thereupon releases, causing the release of relays I08, and. 222. .Inthecasewherethe called, line wasbusy, relay;206 was jenergized in a holding circuit -byrelay-222. and. therefor restoration of the latter relay opens said holding circuit'for relay 206, which then also releases. Upon release oirelay {08, acircuit is established for the finder control relay I 06 extending from ground through the switch;l IQ of the line finder, which is then in its closed or off-normal position, resistor I20,

winding of relay I06, upper backcontact of relay 108, andlower back contact o f relay I09 to battery. As previously described, ;e nergization of relay 16 causes theoperation of motor H4 and the wiperso f the llngfirider switch are then rotated until their normal positions are reached, whereupon switch .II Q is mechanicallyopened, breaking the circuit of relay I06 and thus bringing the line, finder torest at normal position, with relay I06 released, i c The restorationof selectorswitch S. S. also occurs whenrelays flit and llm are released. A circuit is thereupon closed extending from ground through the win ding of v horizontal release relay 2330, contact 23l ofl the pile 2, contact 232 cf thefpile majconta'cczas 'ofthe'pile 2, the middle back contact offrelay l08'and the upper back contact of relay l09 ,t o battery. Relayf23l) energizes to releaseithe holding -pawl 234 from its ratchet 235 and the, shaft ml 'of the selector switch is then rotated counterclockwise by a restoring spring (not shown) tolikewise tumthe wipers 2| Land 2|2 so, that they-,become disengaged fromthe terminals of: the called line; Whengshaft 12 ll has :returned Wits normal horizontal or rotativepositipmit TSfiores;cam1 -2|9 so th th p i n .02 theco aets i lt e m e 208 areagain reversed f closure ofthe-com tact 236,,inthe pile), an energizing. circuit is established for the ;;verti ca l release relay 23] through saidcontact 236,;gqntact 233 ofpile 2i 4, the. middle back contact .of .relay 108 and upper back contact of relaylllfltobattery, Relay 231, upon energizing, relea ses the holding pawl-238 from engagement with theshait 2 t0 and the lat; ter then movesdownwardly to its normal position and upon reaching the same, operates thecan; 213 topermit th contact pile 2M toalso restore to normal. The circuits for the release relay 23b "and 23] are now openecl and said relays are de-energized, The trunk circuit is now restored to an idle conditionand ready-to be preselected for anothercall; 5 p 7 What is claimed is: r ,7 7 M Z: 1. In a telephone system calling and called subscribers lines, ,a pluralityilof trunk circuits, line finders each individual one of said trunk circuits, means toopcrate theline'finder of one trunk to seek a calling line, a trunk selector responsive to the seizure "of said calling line bysaid finder for .preselecting' another trunk and its finder and to startthe ma m a hunting oper-, ation for a succeeding call before said call is initiated, and means thereupon operableto connect said'calling and called lines over the first named ;2.In a 'telephonefsystern, calling and called subscribers? lines, a plurality of trunk circuits;

line; finders each individualto. one of said trunk circuits; means to operate the line finder of one trunk tof'fs'eek a 'ca11ing1 line, means in the latter to prevent the line finder thereo f' f'rom seizing another calling line c'onnected'to a busy trunk,fa}t1unkselectof responsive tothe seizure cf the first named calling'line by's'aid'lfinder' for p'reselecting anothertrunkfforfa succeeding call, andiimpulse r 'sponsivein eans' operable to con:-

nect said callingffaridcalled'subscribers lines. 'In 'a telephone system; f calling and called subscribers'fliries, a'resi'stancefineach calling line} apluralityldf trunk circuits, line finders each in dividual'toio'ne of saidltrunk'circuits, means to operat the line findenof one trunk circuit to seek a calling line,'nieans including vari'ations in resistancesiinjsaid,trunk circuit and the resistance in V a previously busy calling ,linej cooperating toj'prevcnt said seeking finder from seizing said busy calling line, and impulse responsive meansjoperablefjafter seizurejbf the first named calling line" by; said "line finder, to "connect; the latter line to saidcalledline. V r 'j '4."Inf'a telephone' system, calling and called subscribers lines, a';resis;tance in each calling line, a plurality of trunk,jcircuits,' line finders each individual to one ofsaid'trunkfcircuits means to operate the line finder of onejtrunk circuit to seek a calling, line, a high resistance relay insaid trunk circuit responsive to 'aj'calling' condition of said calling, line tostofisaid 'finder on the term'inals of said line, allow resistance relayin series with said high lres'istance'relay; said high resistance relay, when series jwithj the j line resistance of a previouslybusy calling line, preventing the seizure by'said finder of said busy fcalling line,. andfi mpulse iresponsive' syiritching means to connect the first named caning and called lines.

= uponeconclusion or: the call by the calling subi -:5.: In ha -telephone :sy'stem,: :calling: and ,called subscribersfilinesgailmeresistance inieachrcalling i-lineiaiiplural'ity of trunkmircuits; line finders each 'cindiviiiu'al i to one ofrsaid trunk circuits means to rel-ayjoperable to hold said calling line, "said high 1 resistancej-rlay, when: in series -withi'the' 'l-ine resistance-oi e; previouslyf busy calling line, pre venting the si-zure 'by said finder of said busy calling line switching means operable upon seizure cf the-"first named calling line by said finder to {preselect another trmik fon a succeedi-ng -call,fand switching m eans thereafter responsive to impulses transmitted 'f rom' said first named calling line *tcx'connect thesame toacalled line; Y

1 6. In-a telephone system, calling and'called sub s'cribers lines, aplurality of trunk circuits, a line finder "individual 'to each i of them, switching means operable upon 'seizuredf-a calling line 'by *a finder of one of said circuits to preselect an idlearunlvfor -a succeeding callpm eans resporisive to the selection ofsaididle trunk to initiate the operation of the :finder -associated therewith before said succe eding'call is'i nitiated,

' said idle trunk to initiate the operation of the finder associated therewith before said succeeding call is initiated, and other switching means responsive to impulses transmitted from the first named calling line to connect the latter to a I called line.

8. In a telephone system, calling and called subscribers lines, a plurality of trunk circuits, a

10., In a telephone-*system; calling and' called subscriber's :lines; a plurality -of trunk circuits, a line finder individual; toieach of them, switching means Y common to: said trunks and operable upon seizure of a calling line -by one of said finders to preselect "an idle trunk for] a i'succeed'ing call, -means+to:prevent'operation 'of', said switching means should allisaid'ztrunks "be busy, means to rinitiateisaid =preselecting soperationiwhen one of said trunks becomesridlepmeans responsive to the isele'ction' rofzsa'id idle trunk .-to initi'ate the operation zof the finder' l associated. :athere'with before :initiation: of saidsu'ccee'ding call, 7 and impulse rresp'onsive means for connecting saidcalling :lin'e tosaidscalled lineg' :v '1 211. In a"telephoneisystenr, callin-gran'd 'called subscribers: linesga plurality of trunk "circuitspa iline' finder individualito 'eachiof :them, a rotary trunkrselector common tos'aid trunks and actuated; uponiseizure' of a?*callin"g 1ine bythe finder "of one or said trunksfitoipreselect an idletrunk fora succeeding call, 'm'eans to 'prevent sai'd trunk selector froin operating' should all of 'said trunks be busy,":n1'eans t initiate the= operation of said selector, when one of i said trunks i becomes idle, tolpreselectrsa'id :trunk', meansefrective upon comple'tion of said "election-'--to' startf operation of the fi-nde'r of th "tter trunk heforeinitiation of said sllcceeding'nal-l, arfdinieans to cdrhfiltthe connection between said calling and called lines over the first named trunk.

12. In a telephone system, calling and called I subscribers lines, trunk circuit serving said lines, means to preselect one of said circuits for use by a subsequently initiated call, a line finder, means responsive to the preselection of said circuit to start a hunting operation by said finder and to continue such operation until a call is initiated on a calling line, means to thereupon lin finder individual to each trunk and having 1 a normal position, means to preselect one of said trunk circuits for connection to said calling line prior to the initiation of a call on said line, means responsive to such preselection for starting the operation of the associated line finder from its normal position to seek the call to be initiated, means operable upon seizure of said calling line, after said call is initiated, to actuate said trunk presel-ecting means to select another trunk for a succeeding call, and means to thereupon complete the connection from said calling line to said called line over the first named trunk.

9. In a telephone system, calling and called subscribers lines, a plurality of trunk circuits, a line finder individual to each trunkand having a normal position, means to preselect one of said trunk circuits for connection to said calling line prior to the initiation of a call on said line, means responsive to such preselection for starting the operation of the associated line finder from its normal position to seek the call to be initiated, means operable upon seizure of said calling line, after said call is initiated, to actuate said trunk preselecting means to select another trunk for a succeeding call, means to thereupon complete the connection from said calling line to said called line over the first named trunk, and means to restore said line finder to its normal position stop said finder on the terminals of said calling line, means responsive to the seizure of the calling line by said finder to again operate said circuit preselecting means, and means to complete the connection between said calling line and a, I

called line. a

14. In a telephone system, calling and called subscribers lines, trunk circuits serving said lines", means to preselect one of said circuits for having a normal position, means responsive to use by a subsequently initiated'call, a line finder the preselection of said circuit to start said finder from its normal position in search of a call to be thereupon stop said finder on the terminals of the calling line, rneans to complete said call to a called line, and means to restore said finder to normal at the conclusion of said call;

15. In a telephone system, calling and called subscribers lines, trunk circuits serving said lines, means to preselect one of said circuits for use by a subsequently initiated call, a line finder having a normal position} means responsive v to the preselection of said circuit to start said finder from its normal 'positioniin'search of a call to be subsequently initiated and to continue such hunting operation until such call is made, means to thereupon stopsaid finder on the terminals of the calling line means responsive to the seizure of the calling line by said finder to again operate said circuit preselecting means, means to complete the connection from said'calling line to a called line,.and' means to restore said finde to of the first namedqcalling line by said finder for preselectingianotherl trunk for a succeeding call, ,means responsiveto the preselection of said other .trunkto immediately start its associated .finder on a hunting operation; without awaiting'initiation of said succeedingcall, and means to connect said calling line to aacalledline. -1'7. In :atelep'hone system; calling and called subscribers lines, a resistance in each callingline,

' a plurality of trunk circuits, linefinders each indivldual to one .ofsaidjtrunk circuits, means to Itrunk ;to'; prevent the line finder thereof from .seizlngLanother calling'lin'e connected to a busy trunk, a trunk 'sele'ctor responsive to the seizure =2 i operate theline finder of one trunk circuit to seek a calling line, means includingvariatlonsin resistances in said trunk circuit and'the resistance in -a previously busy calling line cooperating to prevent said seeking finder from seizing said busy calling line; meansitostop said finder on the terminals of the first named calling line, means responsive :to;such' seizure vto preselect an idle trunk circuit for a succeeding call, means operable upon such preselection to start a hunting operation of the finder associated with said idle trunk without awaiting initiation of said succeeding call, and means 'to connect said first named calling line to azcalled line. i I

18. In a telephone system, calling subscribers lines, a resistance in each line, a trunk circuit, a finder for connecting a calling line through said circuit to a called line; a high resistance relay in said trunk circuit-responsive to a calling condition on said calling line to stop said finder on the terminals of the latter line, a low resistance relay in series with said high resistance relay, the latter relay, when, in series with the line resistance of a previously busy calling line, preventing seizure of said busy line by said finder and means operable through saidtrunk circuit to connect said calling line to a called line after seizure of the former by said-finder.

WILLIAM J.- MULDQQN. v HAROLD 'r. STENHAMTMER.

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