US2364146A - Automatic telephone system - Google Patents

Description

'Dec- 5, 1944. A. E. JOEL, JR 2,364,146

AUTOMATIC TELEPHONE SYSTEM Filed Jan. 8, 1944 7 Sheets-Sheet l am; .l

/V/ENTOR 14.5. JEL, JR. S

ATTORNEY Dec. s, 1944. A. E. JOEL, JR `2,364,146

AUTOMATIC TELEPHONE SYSTEM Filed Jan. s, i944 'I sheets4sheet 2 A LIM SWITCHES /NvENroR AEJOELJR ArrQRA/E Dec. 5, 1944. A. E. JEL, JR 2,364,145

AUTOMATIC TELEPHONE SYSTEM y Filed Jan. 8, 1944 7 Sheets-Sheet -5' LINE SWITCJ /NvE/voR A E JOE L, JR

ATTORNEY A. E. JCEL, JR

I AUTOMATIC rTELEPHONE SYSTEM Filed Jan. 8, 1944 '7 Sheets-Sheet /NvE/vro/P ,4. JOE/JR By www 'ArroRA/E De 5, 1944- A. E. JOEL, 4R 2,364,146

AUTOMATIC TELEPHONE SYSTEM Fi1ed'Jan.'8, 1944 '7 sheets-sheet 5 TEHMlA/WNG Pil/AMM LINK .SW/TCH RECORDER LINKS JU/VC TOR JUNCTOR /NvE/VTOR A. EJOELJ/P ATTORNEY Dec. 5, 1944. A. E.. JOEL, JR

AUTOMATIC TELEPHONE SYSTEM 7 Sheets-,Sheet 7 Filed Jan. 8, 1944 HHH! I IH HH V WVM/TOR l AE. JOEL, JR

BM? W l "ff ATTORNEY Patented Dec. s, 1944 AUTOMATIC `TELEPHONE SYSTEM Amos E." Joel, Jr., New York, N. Y., assgnor to Bell Telephone Laboratories,` Incorporated, New York; N. Y.a corporation of New York s Application January s, 1944,seria1tNo. 517,496

7 claims. (c1. 179-22)` This invention 1relates to` telephone' systems and particularlyto small capacity automatic telephonesystems. b i

` An object is `to simplify and improveV the operating characteristics `of suchsystems and to secure a maximumpse ofthe various `connecting circuits and switches in` these systems.

Heretofore various systeinshave been used in which cross bar switches have been employed ,with` linking circuits between them `to establish connections between calling and called subscribers in small capacity systems of the so-called community dial oice types. In such systems the connecting links between switcheswerenot always usedrto the full capacity due to inherent characteristics `of the sequence circuits for assigning paths for succeeding calls used in the past. In suchprior systems it was also the practice in order to detect busy conditionsto connect withthe sleeves of, the called lines directly; in the case of trunks to connect directly to succeeding trunks to testthem until an idle trunk lwas `found; and in the case oflinks between cross barswitches to detectbusy conditions and `detect `complete idle paths by `means, of common marker .circuits which seize and `test allsleeve leads at a common point. b

The present invention is applicable `to small capacity automatictelephone 'systems of this general character in which cross bar switches are employed in various linkingarrangements. If the invention'is applied,` forexample, to a one-hundred line automatic system using cross bar` switches it may take thefollowing form.` In such acase the system will include cross bar switches of the well-knownjtype in which the connections are establishedI between contacts arranged `n a coordinate formation by operating one of a plurality of select magnets for selection in one coordinate Vdirection and by operating one of a plurality of hold magnets for selection in the other coordinate direction to establish a connection betweenythe contacts at thecorresponding cross-point. f The arrangement may include l a line switch for each group of ten subscribers lines, a secondary switch divided inten sections, in each section of which a primary link terminates from eachVof the ten line switches, a group The inventive Yfeatures of this arrangement are as follows: Inestablishing `a connection from a calling subscriber to `ajunctor, circuit, the hold magnets of the line-switches and secondary switch control the choice of a connecting path through an idle primary linkand anidle junctor circuit,

`while the select magnets'in the secondary switch are arranged to, control the selection ofa first idle pair comprising a primary link and an idle junctor circuit. K

Anotherfeature is a preference arrangement of the choice of a path from the junctor circuit to a called subscribers line. In case the called line `is in a line switch other than the `one in Which the calling line is located,` a terminating link associated` with the chosen incoming branch of the junctor circuit is Aemployed for establishing the connection over a primary link to the called line. On theother hand if the called line is in `the same line switch as `the calling line this preference arrangement provides that any other first i idle terminating link and primary link are chosen for the, establishing of the connection to the called line.4 The advantage of using this preference `scheme of connectingup called lines is that Afull mon registers for the establishing of connections to called lines and another featurerelates to the `establishing of a connection to acalled line from a junctor circuit by having the chosen register select the cut-01T relay of the called line. lf this `line is idle as indicated by the releasedfcondition of the cut-olf relay the establishing of the connection is initiated from the line to the'outtfeet, made to originate a call to this particular junctor." If the cut-oir relay is operated, indicating that the called line is busy, a busy signal 3 will be transmitted through the register to the calling line. s s

If certain line switches" are\provided with 4groups of outgoing trunks or hunting line groups inplaceoi` single subscribers lines, the register will select the cut-on relay of the rst trunk in the desired group and if this trunk is busy, a connection will be `extended through the operated cut-off relay. to the next succeeding cut-off relay `until an idle trunk is found when the connection to this idle trunk is established from the junctor circuit` in the same manner asin the case of single lines over the secondary and terminating switches.

This invention has been illustrated in the accompanying drawings in which Fig. 1 shows in diagrammatic form a switching arrangement in accordance with the applicants invention appliedto a one-hundred line private branch exchangesystem.

Fig. 2 shows the'plan` of assembling the succeeding drawings, Figs. 3 to 8 which disclose the one-hundred line system circuit details'to illus-- trate the applicants invention applied thereto. Referring now particularly to-Fig.\1 the ygenthe system may be arrangedastfollows: .Two-l0,

subscribers lines I3 and I4 in the two switches and corresponding selectmagnets-for all vsucceedingpairs in succeeding levels of the two=`stitches- 'Each of the" switches Il)V and -Il is 4providedwith Vten primarylinks arranged `in pairs' such as the vprimary link I 5'from switch* I 0 and primary* link e I 6;' from"l switch I I and nine V'other identical pairs lofprimary links: Each "link vis `controlled by -a corresponding-*hold Y`magnet, such as' I'I,for link i5: 4For this-arrangement to accommodate onehundred subscribers lines there-would beprovided ive' additionalA pairs 'of line switches, f the ftl'i pair'being shown-fat'l 20 and 2 I.*- This would makeatotal of` one-hundred 'primary links out- "going from the ve pairs ofr lineJ switches for the Ahundred subscribers lines. These primary" links terminate i-n VaV `scr-'called originating and-termi- ',nating `secondary `linkfswitch 22" 'whichL is f divided 'intenA vertical sections,y the -first fsection 23 and the last section 24 beingl indicated-with one primaryflink AfromA -eachiline switch-terminating 4in f* "anindividual' vertical-sectiona- For examplefthe succeedingv pairs ofl primary-.links terminaterinthe "same mannerlin thesucceeding nineisections.,V In .the -unctor circuitas .Wiube descrbed ,here vvthissecondaryilinklswitchclz eacn.leve1;,is..con"'50` "J t trolled.y by a.corresponding selectimagnetysuchgas :129; `for` example; ifor fthe dirstllevelt` Eachsection .ofithesecondaryllink switcht22 isprovi'ded with a pair .of .linksappearingcas iverticals,.,one ,link fora .mextendingpalls from.. the,primary links anddesig- .znated as: an originating.linksuchfas 3U ,for .tlrie first section 23 `and.y .the companion' linkI for 4exis controlledy by a.correspending hold magnet,

h 33 for terminatin 1ink'3`I. Each of theseV Suc as g 'i65athegrecorderahas. receivedthmdigits is that.a

originatinglinks terminates in anindi-vidual junc- .tor circuit. .For example, theoriginatingilirik 30 from section 23 extends to-junctorcircuit34 and the loriginatingflirik 35 extendsfto junctorcircuit 36. These junctoncircuits haveonlybeen indi. n

c 70 mmatesin Ythercorrrespon,dinghorizontal flcvel liin cated by boxesy andfre'present 'the first and the last junctor circuits'fof a possible group vo f ten. The originating links may also bejcalled incoming' branches to the 'junctor' circuits which'are also provided withoutgoing branchessuchasyfor ex- 5` primary link switch 40.

branch-38 for junctor circuit 36.' Asvthere are I ten junctor circuits, there would be ten corresponding outgoing branches which, in turn, terminate in verticals in a so-called terminating In the switch 40 the terminating links 3l and 35 and intermediate links terminate as horizontals. This switch is therefore provided withften .select magnets such .as for.example; selectmagnets 4I ifortthe link 3I and a hold magnet is provided for each outgoing Wbranch` from a junctor circuit such as for example magnet 42 for the outgoing branch 3l.

-yvr-`Fr`c1fn---ea`ch v junctor circuit there is arranged a eral arrangement of the switches..and circuits of.l :j

x15 'andfleads-'fliiforlfjunctor circuit 36. These leads by 10 cross bar line swtchesrIIl-iand -I Ifwarerarranged side by side with tenl subscribers lines terminating in the horizontals of each switchwith i a select magnet, such as I2, for the first :pair;pf1A

seriesoffleadssuchas 45 from junctor circuit 34 foreach junctori-circuit terminate as horizontals `in a corresponding level in two recorder link switches '48 an'd"49:" These switches have a comi monffselect magnet for each level, such as, for

example, select magnet 50 for the level in whichA vthe'leaclsl 4'5 from junctor 34- terminate.` Corresponding vertical -leads "from eachrecorder link switch kterminate in a corresponding-recorder suchasrverticals -52 from linkiswitches-48 and 49 terminate in -recorder-53while Ivert'ficals'54-terminate inrecorder 55"'*thus providing-five recorders for the two `recorderdink switches 48 and' 49. yThis disposition ofthe-leads in Vthe 'two recorder *link' switches is necessarys as each group inac- *cordance withthe-present scheme contains 'four leadsffrom.each-recorder link switch: `Supple- Am'entary common control-leads and relays are indicatedl by the box '56 Vand 'corresponding leads. A commonallottericircuit andI apparatus-'are indicatedby the box 51' and correspondingv leads.`

fby testing it it is ,determinedthat the-junctor34 is'idle withzits-originating link 30-an'd thev primary link, such as I5, is also idleythe selectmagnet'"2$l` operates:followedbyithe operation oflhold Illagnet 32 which in turn is followed bythe opera- '45 tion of the associated holdmagnet IT; Theihold 'magnet'I'I in the primaryline switch'IIl andthe `select ,magnet .29 in the secondary'linkswitch 22 are employedfor the testing of this connection to ,inaften An idle Arecorder is now'iautomatically "selected and Aconnected,"ior example,"recorder53A over leads '52,` through the recorder; link' switches 48' and 4.4 9 and leads '(45 'for connection to the 55,..iunctorcircuitj34l I'he usual dial tone'is then ;select magnet., :fori exampley lill.,-` ,-for. .line switches ..2Il.-andy. 2 I is actuated asfitfwould represent the -1eve1 :in'whichthes desired sulascifibeisg;line, is rlocatcdisuchz as `forexaJnple,l line-I ...which aterz lineswitchnz0'Lthislselectrmagncteisfoperatcda over attest leadtnroughi abackzcontact of; Jthe cuteoff relay yof the .called subscribers-lineprovidedithat this ;-subscriber-s.:.line :is iidle.. .wltzrslirollldz be obample branch. 3T for ,juncto#,.cirutffrsk and"'75 servedfthat;nthisasathe calledilineiselocated cause the `a une switehether than' the""`1iiieswitehfin `.wnieietheeeiiing `une is located, that is, in the example chosen, the' called line islocated in line switen zo; while the 'eating une is leeeted in une switch'4 Il). Under these circumstancesV as will be described hereinafter, the path over which Athe connectionfrom the junctor 34 to this subscribers` line `6`| will extend over the outgoing branch trunk is immediatelyfound by this means where- 31 from the junctor through the terminating `primarylink switch 40, terminating link 3|,

threugh section 23 ofthe switchi 22, the primary linkf25 and throughline switch 20 to the sube senters Vune el; This wilr be the preferred choice, provided the path through the terminating primary link`3| is idlejas the arrangement the test"` indicates that the terminating primary link 3| is busy thetest seduence circuit arrangement to test for an idle set of links comprising any other idle terminatwill r continue in a regular are further identied by explanatorylegends. A

`upenthe connection is extended to the trunk in the same mannerfasto-an idle called line,` thus eliminating Vthe `actual seizing of a trunk for testing. n 1 l i i l Referringnow to the detailed circuit drawings ofthisdsystemiasdisclosed "in Figs; 3 to 8,'the reference charactersused inFi`g ."1`ar e retained as `rar as `applicable these figures designating the various corresponding partsin Fig. 1,` which call, will first be traced through these drawings from the calling subscriber No.' 1 of line` |3 to the called subscriber 81 oflinel illustrating the connections `establishedin the "case where the called line is located in aline switch other than the one in which the calling line is located. This will be followed by a` descriptionrelating to a case where both the calling subscriberXNo; 1`)` and the called subscriber (No. 11) are located in the saine lineswitehend this in turn win be followed by av brief de scriptio'nfof a trunk or line i Y hunting `callirorn a calling subscriber.

If it is assumed that the subscriber No. -1 calls,

` a circuit is completedfor the line relay 300 from ingrprimary link and its companion primary link e inl any other section ofia switch 22 throughline switch 2|). On the `other hand, if the called line had been locatedin the same line switch I0 as the Vcalling line, it is evident that the correspondingprimary link 3| eouldfnot be usedasthe companion primary link I5 is` already used for the 40 calling `line connection,` and in this case, any

other free pair` ofl a terminating primary linkand f a primary link in any other section `of switch 22 willbe used `for the `call tothe subscriber inline switch I0` v,in accordancefwith the regular se- `quence circuit arrangement.` This test for availi able paths will becontrolled primarily by ground connections at the `backcontacts of the hold magnets in `the associatedline `switch as will be described hereinafter., i l lAs to the testing relating to the idle orbusy condition of a called lineit was stated that for ,the operation of the desiredselect magnet inthe line switch the test wasf effected over a test lead threughthe back contact of the `cut-off relay for the called` line and, that` if the called line` was 4idle `the connectionwas l established. However, if the called line is busy its cut-off relay is operated and in this` case the testlead willbe extended through a front contacter this cut-off relay and `usual busy signal to be `transmitted back to the calling line. l l

lntthis system certain groups of linesmay in'- `stead of beingconnected to` individual "subscribers` lstationsbe arranged as trunks leading to a distant oflice or a hunting group` of subscribers stations. l,In this case if a connection is desired' with such a distant office, trunkorline hunting isarrangedso that when the rst trunk inthe groupleading to this distant office is tested and f foundbusy `due `to the associated cut-oir` relay being operated,\the testllead isextended to the i i rout-off relay'of the next succeeding trunk in this n.group and if this trunk is busy` thetest lead is further extended through` theassociated cut-#0E relay 3H, to ground; That is, anyone of the; primary links from line switch I0 such as for ex.

Vsubscriber No. 1 through line switch l0. `operation of the select magnet 29 closes the cir- Acuit forthe allotter500 for the allotting ofa Y connection from the calling subscribers line over battery, winding ofthis relay, contacts of thecutol relay 30|', over they calling` subscribers loop and' line I3 to ground at contacts of cut-offrelay 30|". The operaticin` otthis line relay causes the operation of the associated select magnet |2` from `battery through the `winding of this magnet,l a

` front contacter line relay 300 and corresponding back contacts "of` line relays rfor the subscribers terminating vinline switches I9 and such as line relays "i303 *and 304;` withfthe ,exception of the `line relay 305` forli'ne" |4 over the common lead `l|||f|`th`rou`gh contacts of one or all of the recordercircuit relays such as `'|00 and/or 10| over ajchain circuit through contacts of relay |02 representing the fth recorder 55 and relay r `|03 representing the first recorder` 53 and contact of intermediatejrelays for intermediate recorders to` ground. `It should be observed, of

course, that the select magnet I2 can only operate if a recorder is available `andino other recorder is originating a" terminating `call through the switches atthis time due to this chain circuit. Select magnet I2 closesan obvious circuit for the yrelay tit,` common to the line switches I0 and ||,"and' this relayin turn closes a circuit `for the operation of relay 3|`|jwhich is individual to `tlfleiline switch l0. rThis circuit may be traced from battery through the back contacts of relays corresponding to relay 3|6 for the intermediate fourpairs of line switches and the front contacts of relay 3|6, winding of relay 3|?, contacts of l Vline relay 30|) and" the` chain circuit previously described `to ground at contactsl of` recorder relay i 103. Relay 3|`| closesla `circuit for the operation of the select `magnet 29 inthe switehrzz, which is associated with'the level in which the lprimary links from the line switch I0 inwhich the" calling line is located'terminates. The cir-` cuit for this select magnet-,29 may be traced from battery; winding of select magnet 29, contacts of ample link I5 terminating in section 23 of switch 22 may be used for extending a connection` to The y relay toa next succeeding trunk.-This testing arrangement is arranged` so thatothetrst `idle a rfprimary;linkfandianaoriginatingflinki to` raffree junctor. zcrcuit. .f .-This. criouitjfor theL starting. of

the;allottenextendsfromfground; contactsofere- 1ay1i50-| self(interruptmgfcontactsfand lwinningfof the .stepping magnet 52,-zcontacts of, relayu 504; towbattery at contactsyof selectemagnetl-ZS.; This causes the stepping magnet 502 to operatevand release under control; otiitsselfeinterrupting lcontacts :to -advancethefbrushes `50 5-vandf 50,6.-to .Search Lori an--idlepath fto.; an idleliunctor. This. path `is found'by the idlerconditiorr. of atholdmagnet in line switch l 0.- fand arnold-.magnet in .the switch 22. If, forfexample,f,the holdfmagnetdrand the hold magneti 32 .are idle `ascii-cuit Ywill bei complete as -follows: frliromillattery Winding...of relay 50|, brush 506 after. ithastaken-one step, -over the irst. .terminal, contactsfiofwthe. .hold magnets 3.2,. :contacts of'l relayl t1, to ground r`ett-.contacts of the hold magnet IJs-:Relay 50|in .operating opens. the.stepping;cireuitl for themagnet 502 which nowstops:and.permitsthebrushes.505.and 506,to remainon their respective terminals; The hold magnet 32 ...is now Aoperated.,- .from l.battery through the winding of .-,this magnet, the :connection at the.rstterminaLthroughbrush505,.con

tacts of relay 50|,.toground. .V1.Magnet32inoper- .atingfopens the original circuitforlthe stepping magnet 502. and closes a., connectionM through .the section 23 o f switc`h522fat thecrossz-pointU9;to .connect the primarylink l'5..to.the originating link,r 30 to, establish -a connectionto .the idle juncpresently,'be-.describedlmIt.there are-tas assumed fit1-ef recorders r providedefor-the tten..iiunctors` fthe 5. recorder..preference:relayssl(lll` andslfl andthree 1.0 recorder intermediate; relays.J .aref provided and iwiredlso that.the-,tenoutgoing,branchesisuchtas,45;.andl8 and others ,are ldividedin pairson .the selection for: 1.cache-pair.oi; a.-pre-ferred, recondenand. if this is ,busy .enybther idle .recorder A/maybe chosen inta' sequencechain. arrangement. provided by4 these-T. relays. i'Ihis Iselecton isv ,initiated 'when thisselect magnet 50-:in theweconderlink switches fi$3..\.and..Minislv operated. In ,this...case.therefore l5 when .thisselect magnet. is-operated and th e,pre

ferred recorder is idleias, indicated. bythe preference .relay .100..heing .released the .recorderi53't be chosen] b'ythe o`peration.. of the hold.. magnets 71.0.6;rv and. 1.0." .which will .thenconnect this recorder 'zo to the outgoingbranch,llotjunctor..34-overleads 5.2.k -The .circuitin 1thiscase willbe 'irorigba'ttery windings vof .these .hold magnets'Mdand v[01 ,conf

tacts ofrelayjail inrecorde'rll, contacts.' otrelay `1ML and.. select magnet 50( to groundas. supplied when this selectl magnet'. ,isopera'ted through .tor 34 Y and. anotheri circuit. furthe operation .o'f n thehold magnet Iflyfrom battery'. .thmughthe 4wfindingof this magnet. over. thesleeveconnection established .at-the. point-,5.01 contactsof. relay-15.0.1 to ground.; The 4operation of.fhold. n1agnet, `.'I.1 closes .a connectiony atlthe: crossepcintto connect the calling. lineA l3to'the v`junctorf3ll oyerthe links|5 and.3'0.. This.connectionalsoauses the operation of ,thecut-.of relay lfrom..battery ,through the winding. of this relay over Lthel. sleeve connection at pointsLlZIlfandf- 509,. contactsof :relay, l to'ground..` It,..shou1dbe k.notedthat Lthe relay50| is slow to;re1ease anderemainsoperated afterits circuit 'isopened at contacts of the ,hold magnet 132 to. permit relay.i30=.l..tol .operate vand Ito thereafter v permit line.frelay.'f60.0 n.theljunctor 34. to .operate from abattery and..,g1'.oundf.through the windings Lof. j this, relay overicontacts. of relay 60.1 and .the ...tQD- and ringcon'ductor over .crosspoints 509 and.`,320.` and/links30..and` l'gandlline I 3f vthrough .the y.loopat ,the subscribersf. station No. 1, and to.. l permit this .relay Lto .operate relay 602 over., an. obvious.- circuit to provide alho'lding .ground .for holdV magnetsl'BZ. and, ILandcuteof relay1'30l. .over the sleeve connectionnthrough cross-.points 509 f and *.3 20.-. I v.The v,cuis.o.,.1,e1ay.3.0 I opensthe circuitforthe line .relay i300 4andalso .the .circuit .for -select magnet` |'2 which...now,; releases.. Select magnet i l 2 .causesnthe release .io`f relays `3 l 6 and`3 ITI.4 and select ,magnet."29. .Itshould be observed Lthatthe circuitfor closing theconnection for..v operating the. hold-.magnet 3.2. .also `extended over .the sleeve.. of. link 301to .the recorder linkiswitches 48 `and49for the .extending of. .a connection .td i anlidlek recorder; ..As...the liuncto`r3l. is .th-e, onechosen by. theilinls 3,40 l a; cir,-

cuitjfor, .the. select magnet .150,y ...intheser .recorder linlcswitches.is1therefore establishedtatvthis time, .that is, beforefrelaye2;:iszoperated; this .circuit extends.- .trom -battery,-. windingwof magnet `5,0, contacta ot relays A0025 and :.601 the -sleevefconnecl- `tion overl ,l link 1.23.0;Pbrush .505.i-,andifthe connected terminal -1-to I groundffat-slcontactsf. of.. relay .45.01. l

5 at-contacts pif-rel y 1'substitute'groundatitsfcontacts.for'holding the a chain. circuitextendingithrough contactslof the remaining .selecte magnets of. switches.C48,` and49.'

On thisj basis', the E,same .re,corder""5`3l.vvould have beenchosenalso .asa preferred recorderby the y1 30 next succeeding'4 selectv magnet lwhilej'the .other y four pairsfof-selectmagnets wouldV have chosen aecorresponding,preferred,recorder..v In casethis preferred .recorder .213; "had .been busy. relay 100 would have. been .operated and l.the next. recorder '$5 suchasfor example recorder55iwouldhavejbeen chosen.' if. the associatedpreference. re1ay";T0`l had beenrelease'd by operating the corresponding 'hold magnets s uchas"108,and1100' connecting the junctor`3'4` to that .recorder over leads 54. "If it :140 is assumed `tl'ienithat'the recorder "53;is Lseized relay. T00 i'sfimmediately. operated to makefjthis recorder busy and'to "circuity 'for holdi magnetsll and T0 magnet 5'0 releas 'l and select es, on the- `olgg'eration o'f re1ay..602 described hereinbefore; Circuits are now com-Y pleted for preparingtthis recorder, l'for 'reception of"the' de`sired subscribers .nu'mberSJ "The `imme diate ,effect of'. the i closingv :of the connection through` thecross-pointsl I0 'andil'l isfthej operation of relay 50| frombatterytvindingof'relay Ithrough' cross-point'l 71.0, contactsof relay180l to" ground. Relayjl 0il inoperating releases relay "'ibutfrel'ay "602 ismaintained operated`over Athe 'sleevej'leadrthrough cross-point" Tl 0i to', ground ay* '2. Relaywlt supplies a established coniiections'sti'iroughl to-t'he' recorder -in'fplaceof thegrcundsuppliedbyrelayB025 The recorder circuits have "not "beens'hown'y in comit--seemsr-unneces`sary to" burden zthe '-idescription with anything but I the essential parts for a clear understandingofthe'applicants l 55 tcausenthe aboveementioriedirecorderibusylrelay Fliitofbe-ioperatedirombatteryf-wndingfofethis irela'yitoca ground! atthe recorderlcircuit indicated r-merelyibya boxd. v

,-', .At.;dia'1 ".tonecisinow transmitted @tol the A'calling f7() isubscriber overatheiiringftconductonvtronicthereprovide ?Ilobvious holding .lmay'A now dialthe desiredlnumber comprisingja 'tens and a units `digit and aringing digit by operi ation and releaseof relay-8&2 tocontrol theusual a recorder relayslin. hox`804.. Dial tone is removed from `the ring conductor afterthe rst digit-is dialed. When al1 digitsjthave` beendialedtthe associated relay 103 `for this `recorder isyoperated v l over a circuit from `batterygat thebox 804through `contacts of relaysV 806 and, 800., winding of relay 103 over the chain `circuit of other corresponding l relays of `other recorders `such as 102 to` ground.

The tiperationofrelay10?` now causes the opera- `tionbf` a numbertof `relays such as `808l frornwloat- 'ter'y throughfthe Winding oft this relay to a ground at contacts of` relay 103., Relays802l andf809are, `also opera'tedover` thesame circuit.` Relay. 80,2 .now releases relay` 602,1n preparation for `the l l selectionrof apath to thecalled` line..Relay 504 is also operated `over an ,obvious circuitu on the `opera-tion of relay 1I23` ,Ifitisassumedthat for `examplethe line 6I forhsubscrber `No.` S51-accessible through line switchll is called, the correo sponding tensrelay 1I2 isoperatedlfrom battery `It may be notedthatlsubscribers linesneed `not belconnected to line switchesr in numericalorder `since each such'linenumber lead may be cross- `connected fromrelays 1 I2 `and 125 toanyucut-off relay such as relays `304|` and 4I0.` `Select magnet i $30 in operatinglcloses` an operating circuit for the l associated `relay 4I Land; this `relayyin turn closes a` circuit for the relay 4t2 `which lidentifies the line switchinwhichrthe called line: is located..` The .'circuitlfor relay 4I2, maybe traced from battery through the `contactsoffrelay `4II,` winding of relay `4I2.` contacts of. relay 4I I, contacts of relay 1I2 Lto ground Itwillklnowhbe noted that as the ,called subscriberls line` is locatedin a line switch other than the `one in; which the calling `,line is located, the terminating `link 3l, which is,` the Cmpanion linktothe originating link30 used by the calling` line connection will .be `chosen for" the extension of` the `connection to the called line as well'asthe primary` link 25from which Athe connection `may `be l extended through switch 20 to the called line -proyidedof course that these links o are id1e.` If l these links v are l idle, which is indicated bythelreleased conditionof hold magf nets `4I4;and5I2 alcircuitais nowclosed on the operation; of relay4I2 `from,groundbat `the hold fmagnet 4I4, which represents the link 25` for the `Operation of the select magnet 4 I, which represente theterminating unkl `aravaca 4o. ,This circuit may be tracedjrombattery through the winding of this `select magnet, contacts of the hold Vmagnet v3,3, `contacts ofV relay I0, 1602 and 150|, contacts of relayV 504, contactsmf relay 4I2 l to ground at contacteer-hold magnet 4|4. This v causes `the `operation:oil` relay `8|!) from battery, `armature and frontlcontact of theselect` magnet 4I, `contacts of relay 103, Winding of relay 8I0 to ground. i It should beobserved `also `that the select magnets I0 Hof switch 22is operated on the operation of relay l 4 I2 :fromground through con, `tacts of `this relay, `winding of `select rnagnet5I0,` l to` battery through a chain circuit throughother select magnets o of switcho22 which indicatesf :that

i .the a plenary` itinigavigegyvilll be liseamrhis select `magnet inturn `operatesfrelay 801"from the bat- 4tery contacts throughfchain circuit over other `selectfmagnets,contactsof relays 504 and 103,

throughthe Winding ofrelay 801 to ground. The operation of relay 801 wouldnow release the. relay 809;,but as this relayis slow in releasing, it will beheld over long` enoughso `that on .the operationloftheselect magnet 4I andrelay 8I0 the` `laattery from `contacts l of `select magnet, 4 I will `have timeto establish the holdingcircuit for this relayl 899` overA the` circuiti` traced for relay 0 I0 and through the armature and front contact and `thelocking winding `of relay 809 to ground at contactslof `relay 100.v Consequently, relay`i800 will be held operated even through relay 801 is operated@` An operating` circuitis now closed by l relay 8| 0 for the holdmagnet 42 for switch 40 to establish a connectiontotthe outgoing branch 31 of junctor 34.` This holdmagnet circuit may be, traced `from batterythrough the winding of thiehold magnet through the `cross-point 1I I contacts of `relay 8 I 0` to ground... Ihis ground from relayl 0 now extends through the cross-point 6 I 2 forjthe link 3l` over thesleevecircuit to battery through the hold rnagnet` `33 of switch 22 to `establish a connection at .the cross-point 5I4 over link 25 to the line switch 20. The same `ground `is also extended`V at thelCrOsS-point `tilt over the sleeyeforthe operationoot the holciM'mfag` `net M llin'the lineswitch `2l)tolcloseaconnecticn Lbetweentthe rlink `25` 1and the called subscribers line 6I at the cross-point M5; rIfhus in'thisf` `case the link 3l ,which `is the'companiol'rof` link 30 is chosen ffor the establishing ofeawconnection to the called `lineas the `called line; is located in a t neswitch otherzthanfthe one in which the vcallingline waslocated.; l: l l

U If we non` pause inltracing thefsucceeding cir ,cuits under thesefcircumstances toconsider the conditionfunder which, this companionhlink 3I lcannotloeused which will be the `ease if the` `called line `was locatedlin thesamelinejswitch as the l .callingline. It is eyidentthat this link `cannot be used in this connectionas there will onlybe one ayailable .path to .the switch' I0 oyerlthe switch 22 `through section4 231l under, these circumstances and asA this path has already beenfusedby-the calling.subscriber. `'I'hat ist, the link. `I5l was used toextend a connection from the calling s'uloscrilrler` tothe junctor 34.oyer, the originating link 30. It

twill `be recalled thatin tracing the previous connectionfor choosing the terminating link 3|` that therelayl S091 washeld energized. If the called if line is located in the same line switch las the call' ing line the 4corresponding select .magnet 4I :will

not operate as there will be .no ground for this select magnetsuppliedV at `.the hold vmagnet I1 "of theline `switch I0 as thisfmagnet is already fopllerated.` Consequently the test must be Vmade 4for `otherholdmagnets in switchIIl to provide another primarylink and` another terminating primarylink. .a ,o N i lIl'iere` willltherefore beV no circuit `for relay 310 to operate this relay beforerelay 1809has chance `to releaseon the,` operation of relay 8,01.` When this takes places,a circuit is completed` for ,the

operation ofrelay 52,0; from batteryuwinding of this relaycontacts of relays 800, 809 and `801` `to :ground at thelrelay 1133.` `Whenfthisrelay 320 is operated, a` circuit may nowbe traced` for the choicefoof otherlpathsltosbedeterminedlylby the operation of another select magnet in the ter `fminating primary .link switch and the operation Aof relay 8| 0. For examp1e, if" thehold magnet 32I foi-.another linklointheswitch` I0 isidle, there will bei a ground v"fromthefa-rmature-and backl f acercara *lay'f'ilil fand thisrcauseszfth'e line 'relay`600 to 4reoperate from the-callingA line and this relay-closes `a holding"circuit'iorthe -relay1602 and also for `linie re1ay-`8l2 Ain thef recorder, from battery circuit ythrough other's'elect magnets in :sw-itch A4i). y

Whenjhis select magnetflfoperates; the/circuit formerly closedA from uba-tteryfat `contacts Zof se- `lect magnetg4l for'the operation of relay 8I|l-now extends through-contacts-- of vselect magnet 6-20 1 to cause the relay -8 |'ll`^^to-^operateA and this relay now completes themonnectionfor the new ypath by^theoperationof ythe holdrnagnet -42-,I and in this case -theconnection extends' -over 'l the f terminating link-V j62 2r" throughv cross-point 623i to Operatethe hojld magnet- 52'2' in the-sectijcn- 24 of switch-22': Thismagnetclosesa circuit at cross- -point` 52 Sffor the operation-of 'thelassociatedhold magnet- ;32 I" for] the' primary link-`-5-24` i through cross-point 36 -to-r thekn calling?" subscrilcerds-J line which may-in this case -be'-for example the called vsuloscriber=No' 10 overthefc alledline-3\21. Thus ity will be-gscenf thatfunderthese;v circumstances another` idleconnecting-pathincluding a termi.-

natingylink and a primarylinkare choseneby the operation ati-switch 40 to-the'fbranch 3T=fof1the In either case, of vtheabov e'two'i'zy1 aes lof conneetionsL the completionn of Athe calli' 'from this case 4where l-in'el :was-chosen lastite-called' line is considered-the operations iwilli proceed as-'follows ItwillfbeL-notedthat when-the hold* magnet therelaygl. g However; 'before-relay afl-Ghasa chance torelease 'the operation of cut-offh relay 4H! closes a circuit for "theestarting lof' the ringing of the called', subscriber and-for releasing the recorder. -To jthis; end this- -circuit causes the Windinggof` this relay;- contactsvof relay-81|),

lead to iground in the`-recorder boxf 884; Relay 8093 new` locks overf its own'armature and Contact togf'ya common ground in the'recQrder and the j ringing-pick-up'relayrf- 80 Iris-'now Qperatedgfrom I battery;through` the-Windingof thisrelay and: its own makebefore-brealgi contactsbofithe busyfrelay 806 and; relay; 80|)L tcthetcommon `ground to Lstart thef ringing.; A Burr-,ging*newI takesplace 80|, `816;- 180|', llgl''through the cross-point |'I0=0f*switch^48','contacts of' line relay 600f`to ground. The incoming branch of the junctor "from Athe calling :lineis fnowbeing held from the called subscriber No-.81 answers this'call, trip relayl 816, loperates-'to discontinue the ringing which Acauses line` Arelay 8 I 2"-to release and in turn causes the release `of relay-6M which now con- .lf-nectslinerelay- 6M? to-thecall'ed line causing `this relay tof-operatewhichin' turn operates relay =6I6.y This relayI in/ operating reverseslthe polarity oi"4 the tip and' *ring conductors of' the callingl ysubscriber4 4to permit equipment well "w a'lmownin-thefart but not-shownfto-start charging fora completedcall. Thefcalling subscriber N'o-.1 -1 yandcalledv subscriber Noi fSL-are' now' connected respectively inl the junctorsfor 4talking 'over-fthe condensers 625 and '-626.1 f The outgoing c jjbranchy of the junctorffrom thefcalled'line is now being-`-heljd from ground on relay 602 through relay- GID. Relay 812` in releasing vcauses the release of the-remaining relaysin'the recorder and `the holdYmagnets-in the recorder link switches e `all!! and'I 49 `andV returnsthi's apparatusY to normal.

over the tip` andl ring conductors over: contacts of relay 8 0 Igin ythe usuahmanner o ver circuits not shown but); "indicatedby the-lboxwl. MRinging -tripjrelay' I 6' vis associated-with "tip aimgl ring-conductors in the usual manner through bozgl. The relay 800 "also 'releasesthe relay "103 which releases; relayf02-,2wh-ichfin turngreoperates relay ignfiunctor .-fiflzfrcrn battery -windingofn this'rei'ay f conductors -from -thevrecordei'gthrough `the -juncringing'currentoverethe' tip*andfringconductors Whenl ther calling party hangs up his receiver, relay fof' the; junetor 'releases 1in turn-releasing"- Arelay 60 2 which releases hold magnetsV 318, 508;"42f15l2' and 4I`4. Considering-now the coniition's arisingl if the called subscriber o No'. 8`1 had been' busy `the opera'tions'would lhave^`been as follows:` -At the time the recorder has `set i up the-'circuits preliminary to the selection of" available-paths'from the junctor 4tothis line the' cut- 'fof relayl` 2`I0 :would have been foundv operated. 'Thus when the unit ground was-'applied at the recorder` due to thefop'eration ofthe tens-relay 'II 2 this groundfwould under these circumstances close acircuit for the'operationof i the busyr'elay .llvoverfa circuit `i`ror`nbattery"through one winding; of this relay; contacts oli-'relays Bill and 103,

. ycontacts of cut-01T relay 4H), back over the unit lead forthis `subscriber through the tens relay 'I'IZto ground at the recorder. 'This `lousy relay` busyL tonefromabusy-tone source through con` tact' ofrelay' 80| Ytogthe ringconcluct'or'of` the callingflineel#tothecalling'sllbscriber No. 1.

`In case thelcallvhad beenj-directedlto-ia distant exchange over-anidle outgoing'trunk `in placey of toa subscriberfsuch'fas No. 18`1yor;No'. -"10,' the procedurewouldv beth'eA same--except"` when a ground is appli-edon` a unit "lead" this- Vunit lead would represent `the whole grouwofitrunks which Imayl appear onf horizontal levels Yof any of4` the line switches whichhave-theirrelaysV corresponding torelays 4112 andi 3I;.'I:"operated over-thc same ljeadif'ljl 34 or 1"-I4 from theitenswrelaysf `If,j for example, trunkffNoz -91i'is 4busy' when lea'd 425 receivesgground duegt'o` the 4operation of-tl'1e'-te'ns relay;A `I25t vwhich represents the", tens digitsl 0f the --flrst trunk-in the"Y group;` the associated cutoff relay 426 is operated: Hence this 'ground ff1ead1425 is extended to #the contacts of the cutoffgrelays` off the next succeeding-trunks.' and fur.-

therextended overthecontacts' of j succeeding cutl-offrelays -ifthe associated' trunks are; busy until an-idle trunk is found; i When such a trunk vfound-tins'groundedleadcauses thel operation `asegure of the associated select magnet, forexample, if all but the last trunk No. 100 are busy, the select magnet 428 will operate in the same manner as any other select magnet. From this point on the procedure is the same as in the case of the selection of a connection to a called subscribers line,

"that is, the particular trunk selected will be conswitch for selecting a rst idle such pair for the sections, a cross bar terminating. primary switch,

registers, groups of lines,each group appearinglin a separate line switch, a group of` primary links originating in each line switch, each link terminating in `a separate section of said secondary switchjunctors each having an incoming branch originating in a separate section of said secondary switch and having` an outgoing branch terminating in the terminating primary switch, terminating links originatingin lsaidterminating primary switch and each terminating in a separate section ofthe secondary switch for connection to a companion primary link in each group of said links. means responsive to the seizure of a calling line for` establishing a connection from said line through the associated line switch and over an idle primary link and the companion incoming branch of an idle junctor through the corresponding section of the secondaryswitch, and thiough calling line to the. seized junctor extends if said links are idle and `said means being operative if said links are busy to extend the connection through any other iirst idle pair of terminating and primary links in any other section of the terminating switch while in either case said means is operative to thereafter extend the connection to the called line, through the corresponding line switch.

2. In a telephone system, cross bar -line switches having selectmagnets and hold magnets, cross bar secondary switches having'select magnets'and hold magnets, groups of lines-,each group appearing in a different line switch, a group of links originating in each line switch and terminating in separate sections ofsaid secondary establishing of said connection.

3. In a `telephone system, cross bar line switches, a cross Ibar secondary switch, a cross bar terminating switch, a group of lines appearing in each line switch, primary linksl outgoing from eachline switch, one-of said links from each line switch terminating in a separate section of the secondary switch, junctors each provided with an incoming branch terminating in .a separate section `of the secondary switch and having an outgoing branch terminating Vin the terminating switch, terminating links `each originatingl in the terminating switch and terminating in a separate section `of the secondary switch, means responsive t0 theseizure of aline for establishing a connection over a rstidle pair comprising an idle primary link and the incoming branch of `an idle junctor` through the corresponding line switch and section of the secondary switch, ,means'controlled by impulses received from the calling line over the path tothe chosen junctor comprising `said` primary link and incoming branch for establishing a connection fromthe outgoing branch of the junctor, over a terminating link and a primary link to a called line through said terminating switch, secondary switch and associated line switch, means operated `during the establishing of said last connectionfor directing it over a path including the `terminating link terminating in the same' section of the secondary switch asthe incoming branch of the chosen junctor if this terminating link is idle, and the called line is loi cated in aline switch other than Vthe one in which the calling line is located while if .this terminating link is busy or if the called line is located in the same line switch as the calling line, said lastmentioned connection is directed over a pathincluding a `rst idle terminating link of the rei `links outgoing from each line switch, each link from a line switch terminating in a different section of said secondary switch, junctors'each provided with an incoming and an outgoing branch, the incoming branches terminating in diierent sections of the secondary switch, the outgoing branches terminating in the primary terminating switch, terminating links originating in the primary terminating switch and each terminating in a separate section of the secondaryswitch, means responsive to the seizure of a calling line for establishing a-connection from said line over i a primary link and the corresponding incoming switch, junctors each having an incoming branch originating in a separate section of said secondary switch and an outgoing branch, means responsive to the seizure of a calling line for establishing a connection from said line over a link anda corresponding incoming branch of a juncto-r through the associated line switch and associated section of the secondary switch, said means including circuits controlled by the hold magnets of lthe two switches for establishing a connection overa pair comprising an idle link and the associated incoming branch of an idlejunctor and circuits controlled by the select magnets of the secondary branch of a junctor through the associated line switch and associated section of the secondary switch to the junctor and through said junctor to a register, said means including circuits cons trolled by the hold magnets of the two switches involved for the' establishing of said connection over a pair comprising an idle incoming link and the incoming branch of an idle junctor, and circuits controlled by the select magnets of the secondary switch for selecting a first idle such pair for the establishing of said connection,means controlled by impulses received over said calling line in said register for establishing a connection from said junctor to an idle called line, said means 8 azaamc including circuits controlled byfholdmagnets' of the line switch in whichlthecalled 4lineislocated and ofthe secondary switch to select a path including thelt'erminating link inthe same section of the secondaryswitch in'4 which the incoming branchifof lthejunctoremployed is located if this path is idleiand` if the-called line is locatedin a linezswitch.y other than the line switch in which thef'callingl line is located, while if this path is busy orif the called line is located'in `the same linefswitch Vas thecalling line another idle path for thefestablishing of this connection is chosen including another terminating link andfanother primary link.

5; Ina telephone system, `cross bar switches, lines, a cut-onc relayassociated with each line operative if 'the associatedline is busy, junctor circuits, registers, means vresponsive to the seizure ofY a calling line for actuating said cross bar switches to establish a connection from said call ingline to van idle junctorand from this junctor to an idle register, means responsive to impulses received in said register from said calling lirie for establishinga connection to the cut-off relay of a called line, means operative if the called line isbu'sy as indicatedby the operated condition of the associatedV cut-oir relay to transmit a busy signal to 4the calling line, means in said register operative'if the calledline'is idlelas indicated by the-released condition of said cut-01T relay to actuate said cross bar switches to establish 'a connection from the chosen junctor to said called line. v

6. In a telephone system, cross bar switches, callinglines, trunksarranged in groups, a cut-off relay associated with eachtrunk operative if the associated trunk is busy,` junctor circuits, registersjmeans responsive to the seizureof a calling line for actuating said cross bar switches to establish a connection from said calling line to an idlejunctor and from. said Ajunctor to. an idlel register, means responsive to impulses received `in said register from said called line for vestablishing a connection to the cut-01T relay of arst trunk in i any desired group, contacts on said cut-off relays for extending said connection from the rst'cutoff relay if the associated'trunk is busy as indicated by the vactuatedcondition of said cut-off relay, to contacts of Vthe next succeeding cut-off relay until an idle trunk is found as indicated by thereleased condition of the associated cutoi relay, jmeans operativeaslindicated 4by themes leasedcondition. of the cut-off relay .of afrstfidle trunk to` actuate said switches Ato -establisha conf Y nection fromthechosen` junctor tothe said rlrst idletrunksA y d ,l

'7. In a telephone system, cross .bar line switches,

a crossr bar secondaryswitch .divided'in sections,

a cross ba'r'terminating primary switch, registers, groups of lines, each group appearing; in a sepagrate line switch, fa group of primary 'linksorigi nating in each line switch, 'each link terminating in a separate'section' of said 'secondary switch,`

junctors each,v havinganv incoming branch-'origi nating in va separate section of ysaid secondary switch and having an outgoing branch terminati` idle primary link and the companion incoming branch of an idle junctor through the'corresponding section of the secondary switch,and through said junctor to an idle register, means responsive to dial pulses received in said register over said connection for selecting and connect'- ing la desired` called-line to saidv calling line including means for causing the said register to seize the selected called line to originate a connection to the outgoing branch of the chosen junctor with the connection extending from the line switch associated with the called line and primary linkappearing in the same section of the secondary switch if the called line is located in a li ne switch other than the lin'e switch in which the calling line is located,'through the ter'- minating link and terminating 'primary vswitch if said links are idle or 'if the called linefis located in the sameline switch as the calling line or if said links are busy toveXtend the connectionover any other rst idle pair of primary and terminating links in any othersection of the secondary switch while in eithercase the same said means as used for establishing a connection from the calling line to the incoming branch of the junctor is operativeto extend the connection from the called line to the chosen junctor. Y i

- AMOSE. JOELJR.

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