US1904904A - Automatic telephone system - Google Patents

Description

April 18, 1933 v. s. THARP Er AL AUTOMATIC TELEPHONE SYSTEM '7 Sheets-Sheet l Original Filed Jan. '7, 1929 HOlOFN/VOD 0l MSMQQN U `April1s, 1933. v. s. THAR'D am. 1,904,904

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. '7, 1929 7 Sheets-Sheet 2 POLAR/IED X OFF/cf Claret-Lr: e E. Lomax.

April 18, 1933- v. s. THARP ET AL AUTOMATIC TELEPHONE SYSTEM 7 Sheets-Sheet 25 Griginal Filed Jar). 7, 1929 UTB-1F11 E. Thap Elan-'aune .EL MAJ-415m; y

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April 18, 1933 v. s. THARP ET AL.

AUTOMATIC TELEPHONE SYSTEM '7 Sheets-Sheet 4 N 0%.. 1mi lll www Em www www u www N MQ mswkm .m

April 18, 1933. v s THARP ET AL 1,904,904

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. '7, 1929 7 Sheets-Sheet 5 z oFF/cf UWE? E. Thal-I Clarence E. Lnmax April 18, 1933 v. s. THARP Er AL AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. '7, 1929 7 Sheets-Sheet 6 dmwllwlm. Milli.

nUEr-Llnrs' Uu: nr 5. Thap Clarence E'. .Lomax lApril 1s. -1933f v. s THARP n M 1,904,904V

AUTOMATIC TELEPHONE SYSTEM original Filed Jan. '7, 1929 7 Sheets-Sheet 7 YaFF/cf C2 l -...E04 j Patented prl8, 1.933

UNITE-n f c l l vieron s. Timm, or' n'LMHUnsT, AND'CLRENGE E. LoMAxoF/oax- Plink, L'LLInos.

I Assreivons BY MEsNE Asseivmajnrs; To Assocmrrnn nnncrrnliofnaomronins Y i 1Nc.,.or sarcasm-immers,AcoaPoRATzoNoF DELAWARE AiIroMATicf TELEPHONE SYSTEM f Applica-tion mea January a, ,1929, serial No; 330,343'. 'nenewkiseetemteflii; 1931;.: p

-The present invention relates in general to y mnlti-ofice telephoneV systems, .but isconcernedlmore particularly with telephone systems in which callsare extended through the medium Vot automaticswitches. The mainV features of theinvention `relate to multi-.ollice systems in which a calling subscriber may be charged for completed calls according to the ,e actual durationof the call and also according 13 to` thelocationof the office or exchange inr which the -called line terminates.V

Ininultioflice telephone systems it is. sometimes desirable to make` a fixed charge for,

`completed `calls withinan exchange orbetween several exchanges' relativelynnear to# gether `in the same area or zone, ,whilec'alls from exchanges in one zone to exchanges 1n-l 'a diil'erent zone-may be `charged `for on the Y, basis loi" the durati'onof` the call.

20 A suburban servicemay be provided whereby calls will be extendeddirectly by amanual operator to a subscriber'in a semi-distant exchange without setting up the usual toll con-v It is customary to make a greaterl charge for calls of this type than is made forA calls between subscribers .in the same townorA system of exchanges. The additional chargeV nections.

may be made by keepnga written record of each call `or by providing. a means 4by `which 3U tlie'operator may Acause the subscribersmeter toV register additional call units. l The latter f method is preferable as it eliminates the necessityofverifying the number of the'calling' Vline. 'i

he present invention is particularly effec-v tive in a system ofthe-above type, as itprovides for automatically` registering the proper. Echarge for local and inter-zone calls,'

and also provides asimple means whereby an` 40- operatormay malrean additional charge on.

suburban calls.

` One object of the invention is toimprove systems oflthis general` characterpby pro,

l viling simplified circuitslby which the meter-Q 45 ing operation may be accomplished.

Another object' of the inventionfis to` provide circuits whereby calls may be extended automatically'from one exchange to another r through an intermediate exchange, the meter! '50i ing. operationbeing effected by apparatus in the intermedi,ateexch-angeV which in'turnf'i's a controlled from the termiatingexchajgnge. I

Another objectof'the inyention ist'ojprovide a'means whereby an operator ati a manualor toll 'board' may position the `ref)eater through which a call is extended-from an out@ lying exchange VV'so that meter registrations will automatically be inereasedwhen thecall is furtheriextended to semi-distant" xg, change."A 'l' n Y practical..

The foregoing features together others not specificallymentioned willbe mere-1 fully pointed outhereinafter. v Y

The accompanying drawings comprising Figs. l to 9,"in`clusiv'e, shew-.by meansoflthe usual circuit diagrams,` a' Asullicient' amount of,

equipment in fa telephone system Vvembo'dyi/'ng` the features ofthe invention to enable` the-f inventionto; be understood;

, Forthe purposeof thisdescriptionitis assumed that'theequipment 'embodying tliefV invention is locatedl in three separate .1 exi" changes which `will be designated as .oflices X,2Yand Z, respectively. Itis to be "under' stood, however, that the rapplication ofthe invention is not limitedto thisparticularvar rangement but that it maybbeused with other y combina-tions' of `equipment and in systems V` comprising a different nui'ber of exchangesjj from that described herein. L L

y rig. ianathat portion einig; 'saying the leftofthe heavy broken'line equipment llocatedfin X oilice.V Fig.` 2 tothe right ofthe-'heavy broken line fand vFigsJBQ l 4:,6 and 7` show equipment located inf Yfof-f f fice.v The equipment in Z oiiicefis- Shown in' Fig. 5.- F 1g. 8 shows the method of straps- Y ping the test contacts of the banks of switch? i ing connector C off Fig. 1.` Fig; 9""is a layo'ii't',4

diagram showing-.how the sheets on which? i .Y Figs. l to 7,` inclusive, are'drawnfshould'be placedtogether in lorder tobe undeifstonfidi best;

Referring particularly to` Fig-LA and AQ? a represent ordinary automatic 'substatio'iisf equipped with usual talking, "signalling K and impulsing instrumentalities rand individually connected to line switches LS and LS1, respectively. The line switches are of the well known rotary type provided with a meter .controlled over a separate wiper of the switch.

Mechanically, connector C is of the well known Strowger vertical and rotary type. The circuit is similar to the ordinary switching rotary connector with modiications to provide a quick switch-through on trunk calls. This feature is superior to the switching-through methods used in previous connectors since the quick connection to the succeeding switch minimizes'the chances of mutilating or losing a dialed vdigit which might occur in case of delay in extending the trunk.

. In Fig. 2 is shown an outgoing repeater OR and an incoming connector C1 associated with the end of a` trunk terminating in X oiiice. rThe 'incoming repeater IR and Voutoutgoingirepeater OR1 are associated with the other end of the trunk inYotlice. The circuit of repeater ORl is similar to the ordinary loop repeater modified by the addition of a relay whose function is to provide a special means of metering.` Connector C1 is identi- Ycal with connector C. Only that part of the erating loop circuit is switched to a simplex i for metering purposes.V This selector is in holding circuit. Metering impulses are repeated vback tothe calling line by removing the potential from the simplex holding cir- 1 cuit.

Repeater OR1 is' connected with the trunk only when a call isextended therethrough,

and inY this case, re eater TRis disconnected from the trunk. epeater OR1 extends a g; loop circuit overV the trunk to operatecon- 4 nector C1 Y1n the usual manner.

peaterV 1s also arranged for metering over f This retheV fourthv conductor of the incoming trunk. Referring to Fig. 3, incoming selector S iis `an ordinary Strowger type selector provided witha separate conductor and Wiper the same office and is directly associated with incoming repeater IR. The loop extended 5 bythe repeater controls the operation of the selector-'in the usual manner, and when an idle trunk is found, the loop is extended to the succeedingswitch free Aofany connec- ,l tions-in the selector.

Fig. 4 shows an outgoing repeater, OR2,

and an incoming repeater TR1 associated with a two way trunk. These switches are assumed to be in Y oiiice, the associated trunk extending to Z olice. Repeater OR2 is accessible to both local and incoming selectors in Y otice. Associated with and a part of repeater CB2, is a time pulse metering device M consisting of al rotary switch RS and asso--` ciated relays. On calls extended through the repeater, the operation of the time-pulse device under control of the interrupter INT causes metering `impulses to be transmitted back to the calling line at centain preestablished intervals. On calls to an operator the rate at which metering pulses'are sent out can be increased to twice` the normal rate under the control of the operator.. As

shown, the repeater is normally disconnected from the trunk, but when a call is extended thereto, the cut-olf relay of theV re-v peatertransfers the trunk from incoming repeater TR1 to repeater OR2. l

Repeater TR1 is a simple repeater operating over a loop to which battery andl ground are connected atv thefdistant office'.

The repeater extends a loop to'incoming selector S1, and controls it in the usual man ner. The circuit of selector S1 is exactly the same as that of selector S shown in Fig. 3.

Fig. 5 shows equipment located in an exchange of the type in'which dialed impulses: are repeated by the first selector to succeeding` switches of the train.

Incoming repeater TR2, normally associated with the trunk operates over the loop extended by repeater CR'2 and' extends a control circuit to selector S2. Dialed impulses are repeated as ground impulses over a conductor of the trunk while a holding circuit ismaintained over the othertrunk conducf tor. When a call extended through the repeater is answered, a ground potential placed Y on one trunk conductor by the connector op- Y This relayv erates a relay in the repeater. short circuits a part of the winding ofthe relay controlled by theloop from the preceding switch and thereby increases the current flow in the trunk. They increase in current flow is used to operate the metering equipment in the preceding switch.

Selector S2 is mechanically similar to the previously described'selectors S and'S1. The circuit, however, is of the well known' type used in the systemof Siemens & I-Ialske.

Selector S2 hasaccess to theusual switch train in .an oiiice of this type comprising selectors S5 and connectors C3 which, being well known, will not be described in detail.

Succeeding selectors may be identical .with

selector S2. A connector which will operate.

satisfactorily in this system is shown on page 46 of the illustration section of Dr. Fritz Lubbergers book Die Fernsprechanlagen lio Bfr

Mit Whler-Betrieb (Automatische Tele-` phonie, third edition, 1926. Y

A"Selector S2 also has access to trunkste'rminating in an operatorsposition',a part of i theoperatorls answering equipnient,.OA,'be-

ing shown. It is assumed that all tolfl and suburban calls for the system will be handled atthis-oper-ators position which is located in Zoiiice. n y An operators calling circuit, 0C, Valso has` access tothe trunk to4 which repeater IRE' is connected. V'When the trunk is used `by'the operator the repeaterisA disconnected,y and when the repeater is in use the operators cir; cuit is disconnected and the operatoris' informed-by 'a usual Visual signal offthe busy conditi'on'of the trunk. Calls from substationsfsucli-as A4 in Z olice to substations in X-and Y oflicesfwill be completed bythe operator.y The operator extends calls over` the, trunk by means of al loop toy whichVV batter'y fand ground are connected at the man ual position. i

In Fig." 6, selector l by a rectangle, isY identical with selector S. Ag represents substation vin Y otiice ter- Ininatijng'in rotary line L'switch VLSg Which inA tury'has access toselector SQ.' Substation A2` and line switch LS'Z are exactly the same as previously described substation A and line sWitchLS.' l y v"In 7, C2` represents alocal connector of the ordinary Strowger type arranged for` fourth wire metering. The connector is assunied to be in "Y cnice-land has access to subscribers' lines of whichsubstation A5 terl-f4 minating in rotary line switch LSI is one,` The connector is accessible "inthe banks of local selector S4 and incoming selectorsS and S1 Aall'in vY oHice. i Substation 4AaQand -line switch DS3 arethe same aspreviously described substation A and line switch LS.Y

The Various units: ofpequiplnent and their locations -with relation to. each other Vhave "been briefly described. The arrangement and,

operation ofthe, system as a whole will now befconsidered. n l i Olice `X is assumed ,to be a branch exchange connected bymeansof twoconductorftrunks with loilice Y,`a main exchange. Office Y is provided with: trunks to other main` exchanges such asuZ cnice.` Inter-oiiice callsf originating in X,oiiice Will be routedv` Ythroughequipment in Y oiiice in aA manner comin-only known-as tandem trunking-.

l'The equipment Vin X and Y oiiices is of the twowire type in which kthe Various `switches. are directly controlled by the calling zsubsoribcr over the two sides ofthe line in serieslV Eqtiipnientfinthe Z office-is of the type in whficliftheist' selector only is directly con-` trolled byythev calling"1 subscriberl oyer the two sides of' the line in SeriesTSuCceeding' switch-es 'are controlled by impulses repeat-M ed bythe vfirst"selectorfand transmitted severi'.

one sidelofithe tr.unk.xfV i Calls may be completedfautomaticallyin:

'and between Xand oliicesrand ffrom'either v of these oliices toZ oliice:.-Localfcallswin office may be. completedautomaticallybruti` calls from .this office to .feitherf X are completed manuallyLwone meter registration is made for each# coinpletedl callregardless of duration. lOna-calls: c

from 'eitherfof theseoiiices to asubscribei's y i `inZ oiiiee, one ineterregistration is made as? Vsoon as the call is answeredwithl an; addition!-v 'i al registration for each time. unit over-"thc basicv time interval. The time intervalmayf be set within any reasonable'limit. f Locali. f calls' in the Z `ollic-zfinay be' metered lby any" of the methods ordinarily-used in exchanges: of this type.. Y' f' Suburban calls, p ers in `other nearby cities `of thisfsystemor p A Qthersystems are completed by afmanualor Si which is representedr toll operator-in ZoiiceJCa'll's of this class; originating kin X jor YV` offices 'arerextended over rthe regular inter-ofiice trunks I andA through-the switch train at vZ ofiicetothe-ly manual or toll position. Thev operator may position the repeater at Y oiiiceithrou'gh which? the call was extendedso'that the metering` charge ordinarily registeredfforcalls to Z55 oilice will be doubled. f

Having explained the object vention and the apparatus employedfthe: operationsinyolved'in setting; up .various connections in a system of jthis type will new? bcdescribe'd inldetail.l 1

'Assumin' -first that the subscriber'atsub-Z station A Fig.1).in Xoiice' calls'thesub'f; scriber A4 inA Z 'office (pF `ig.5).1{VV'hentheV ductors of the vcallinglline and line-switch;

that is; @aus te jlitsefitfV esi or alle in;

LS 'searches for an idle trunkinthelusual manner. When an' idle trunk isencounteredf,

for example, the trunkco'mprising conducf" l tors 18to 21,'inclusive,'the calling loopfis exif tended to line relay 103 of connector Y Line relay 103, release relay 104.v and# change-overurelay 105 of the connector' are energized `in the usual manner. Relay 104i connects ground to the release trunk at arma-- ture=130A to hold the cut-oil'lrelay-ofthe linev` switch in operatedposition;V Relay 10A-alsof? closes a part vof the impulsing circuit at armature 132, relay 10.5 disconnects ground from 12a ture 181. V-At contacts controlledby arma Y* f the low-er Vwinding of relay 103'anfd5 connects' thereto vanother ground Von. which ,the-diet` l' tone is superimposed?? AtarmatureV 134 fre= l lay 4105V connects the-impulsing circuit'to? ve`r tical `rnagn'etrllQ and at arm-ature'133 con-'f d .nects its own lower winding toathe'impuls ingfcircuit in'parallel Awith?thevertical mag'- net.` YThe" foregoing operation takes place"v 1'65A receiveris lifted at thesubstation A, theV 1 usual loop circuitis cl-osedover the twocon'fhv when the receiver at the calling substation is lifted and the connector is then ready to receive the dialled-impulses. It. will be assumed that the calling subscriber now dials the digit The calling loop will be opened ten times and line relay 103 of the connector will respond by deenergizing and reenergizing with each interruption of the loop. With each deenergization 19, 0f relay 103,.the. vertical magnet will operate in the usual manner and raise the shaft one step at a .time until Vthe wipers are opposite the tenth level of bank contacts. The initial energizing winding of relay 105 is short cir- :ti cuited at .contacts 119 of the off-normal `V springs which closed on the first vertical step. Relay 105! does not -deenergize at this time since vits lower winding isconnected in parallelwith the vertical magnet and due to its 2,9; slow releasing character, the ground impulses tothe vertical'magnet are sufiicient to keep it energized during the period of impulsing. Shortly after the last impulse of the series,

relay 105 deenergizes and disconnects its 2.5; lowerv winding from the impulsing circuit at armature 133, and at armature 134 switches the impulsingcircuit to rotary magnet 113. Upon restoring, relay 105 disconnects the dial tone ground and reconnects the ordinary .39.: ground to the lower winding of relay 103.

Relay 104 being slow to release also remains energized during the series of impulses when its circuitis opened by the impulsing of relay 103.v K

As the wipers are stepped to the tenth level, the shaft springs .operate and contacts 122 close a part of the circuit of relay 101, which,

A Relay 107 deenergizes, opens its ownlocking.

however, does lnot operateat this time. part of the metering circuit is also lopenedby I the shaft springs-at contacts 121.

l It will now be assumed that the tenth level ofthe connector banks is equipped with four trunks terminating inthe repeaters such as OR, and that these trunks are connected to 45.-

, level. vThe subscriber now dials theA digit 1. Relay 103 Vresponds in the usual manner and the rotary magnet is energized-v o'ver a circuit including armature 131 i of relay 104, armature 134 of relay105, armature 143 lof relay 108, winding of relay109, and Varmature 157 of relay 111. Slow release relay 109 energizes in series with the rotary magnet and at armature 145 opens a point 1n i the circuit of the lower winding of relay'110.

At armature 146 a Vcircuit is closed for theV upper winding ofrelay 110, and at armature 147. a pointin the circuit of relay 107 1s opened. The utility of the last operation will be described in more detail later on. ,l Y

. Relay V 'operates' and atV armature 148 closes a point in the circuit of its own lower winding;.at armature 149 connects test wiper 117 to test relay 108; ,atarmature' 150 closes 5.513 a point in the locking circuitof its own ulp-v the first four sets of bank contacts of they per winding; at armature 151 closesy avcircu'it for the rotary magnet independent of ther contacts of the relay 108; at armature 152 closes a point in the circuit of relay 107 and:

at armature 153 opens apoint in the busy tone` circuit. Y

' If the trunk on which the wipers stop is busy, test wiper 117 will find a ground'fpo-v tential. Test relay 108 will operate from this,

one, slow release relay 109 deenergizes. lIfhev lower winding of relay 1170 is then connectedl to control wiper 118 by way of armature 145 of relay 109. Relay 110, however, has no function to perform at this time. At armature 146 relay 109 opens the initial energizing circuit of relay 110 and at armature 147 closes a circuit for relay 107 including armature 152 of relay 1 10 and the' interrupteif springsof the rotary magnet. Relay 107 ,op`

erates and armature 139 closes a circuit for the rotary magnet including armature 157 of relay 111, and at armature 140 closes a'- locking circuitfor itself including the interrupter springs of the rotary magnet. .The

rotary magnet energizes, steps the wipers'to the next setof bank contacts, and' opens the circuit of relay 107 at its interruptersprings.

circuit, and opens the circuit ofthe rotary magnet which also deenergirzes. If the Vnext trunk is busy, the above described operationl is repeated, relay 107 and the rotary magnet alternately energizing anddeenergizing to step the wipers ahead a step at a time.

If all trunks of the group are busy, the wipers are stepped to the set of contacts following the last trunk of the group. Inthis'` case the bank contacts with which wipers 117'V and 118 are engaged arestrapped together and connected to ground 4as shown in Fig. 8.

Relay 108 willr remain energized from this' ground over the test circuit previously traced. A' current will also flow in the lower windingl of relay 110 over a previously ltraced 'control a previously 'traced locking circuit for reg lay 108 including contacts controlled by armature 149 ofrelay 110 and armature 141-ofy relay 108,v opens the circuit for relay 4107 at armature 152 to prevent that relay from again energizing-and operating the rotary magnet, and at armature 15.3 closesa part of the busy tone circuit. The busy tone is now givento the callingsubscriber who is thereby informed that lall'ftrunks are busy at this time'. 'l y 'If a trunk hadV been idle, for example, the trunk comprising conductors `167 to 1.70, inclusive, terminating inV bank contacts 159 t0 162, inclusive, the wipers would stop on these contacts, the'operation being as follows: f

VAn idle liner is marked'bybattery poten- .tial Vonthe testcontacts. If the lirst trunk is idle, wiper 117 encounters the -batterypotential on the test contact andfrelay 108 does tnot operate. Shortlyafter theflast rotary impulse, relay 109 restores. 'I`l","l1oweVer, Vbusy trunks had been tested previousto find- Iingtlie'id'le trunk, relay 108 would be energized and relay 109 deenergized as previ-` ously described. Relay 108 thendeenergizes `when wiper 117 encountersrthe batterypoten- 'tial .on the test wipers; ith'both relays 108 and 109 restored to normal,the circuit of relay 110 will be openand relay 110 deener- Ygizes. VA'circuit may then be traced from battery on uthe test contact, wiper117 armature* 149 of relay 110, lower winding of relay 111, to ground at armature-130 of re- -circuit and `at armatures 154 and 158 connects #the talking conductors of Vthe uconnector to .wipers 115 and l116;at armature 155 connects test'wiper 117 to the release trunk; at armature `156 .connectsits own upper winding to the release trunk and closesa circuit Vfor IIrelay 101, including contacts l122 of the operated shaft spring, and opens the circuit of the rotary magnet at larmature 157. The upper winding of relay 111 now maintainsit in operated position. Relay 101* operates and, at ycontacts controlled by armatures123 'andf126, switches the conductors of the callloop from relay 103 .to Wipers 115 and .116;fat armature 124 connects meter conductor-21 to wiper 118; and at armature 125 opens apoint in the circuit of the release mag- 'net. After relay 101 operates,`relays 103 and f 104 :(leenelgize. Relay 104 being 'slow to i 'i .restore, will maintain theholding ground' on the release trunk until-a ground is'returned by the switch ahead. f These relays upon *restoring also close points in the release circuit at .armatures 129 and 131. The calling line loop is now extended directly'to line relays 202 of the repeater OR by way of Wipers 115 and 116, contacts 159 and 160, v conductors 167 and 168, lefthand Windingsof repeating coil R, and contacts controlled by armatures 212 and 213 of relay 20,1. Metering conductor21 is extended' by way 'of Wiper 118, contact .162, `and conductor 170 to a contact at armature 215 of relay 201.V

Release trunk conductor 20 is extended by j way of wiper117, contact 161, conductor 169,

lay104. Relay 111 operatesover the, above `operates over the `loop circuii-gextenddmby `right hand winding of repeating,coiljRgxare' ,connects the ground to `the *releasef' to contacts at armature 219of relay 204, andl thence through normally closed contacts 130 `of relay 104 in incommgconnector C1, 'to

relay 205@ `Relay 104* corresponds Withrelay 104 vof connectorV 'Relay 104 of con-frm 'nector C, as previouslyy explained, hasmainv j tained a ground on releasetrunkfor a short interval after the vconnection is Y extended.

Relay 205 operates from this groundand switchesrtrunk conductors 207 and '208 from i75 the incoming connector C1 to talking conductors of the repeater'OR.' Y Y' Y Relay 202energi`zes over the calling loop and at armature v216 l closes a point vr'1n the vj loop circuit tothe repeaterIR inthe vdistant oiiice,"and1at armature 217 closes an obyious vcircuit Vfor relay 204. Relay 204 operates `and atarmature v219v connectsy ground to the Vrelease trunktohold the lpreceding switches rf vin operated position Aand to keep relayf-205 j energized afterrelay 104'ofconne1ctorGldeenergizea At armature 220 relay 204: lso

closes a `circuit for the upperl win'dirigslof relay 203 including!armature,` 211101? "relay the high resistance in the circuit. y

Line relay *236 of incoming 'l repeater *,"IR

the repeaterOR. This circuit jmay'betaced as follows battery,:upper windingof :relay 236, contacts controlled'by armature 245 of e relay 234,1upper left hand winding `of-*ref Y peating coil R1, armature268 of'cut-oli relay M y 261 in repeater OR1,gthence voverthe'ftrunk 105.

conductor 207, `armature 223y of relay 205 in per right hand Winding of repeating coilR, upper winding o'fpolarizedrelay`201, lower ub mature 221 of relay 204, armatureV 2240i? 're'- lay 205,'thence over trunkconduc'torl-208y- ,Y armature 269 of relay 261, leftha'ndwinding of repeating coil R1, contacts controlledby armature 246 of relay 234, lower "Winding of relay 236 to ground. Relay'236 on operating closes a loop circuit to the succeeding Switch at armature 248 and at armaturef249 ycloses,

an obvious circuit for relay .231." VRelay 231 operates andv at armature 5238*' connects,"120 ground to y release trunkfconductor 252,v 2a branch of which extends'through'the lower winding of 4polarized relay 235.` VRelay' 235 does not operate atV this time, howeyer,fover its lowerwindin'g alone( At`armature239 125 -relay'231 disconnects relay 261 of repeater OR1 from release trunk conductor282'-of 'the trunk incomingto thft repeater,war1d conductor to mark the repeaterbusy.

trunk in the usual manner.

The loop Vcircuit extended by the repeater armature 361 of relay 305 in selector S, low- .ergwinding of relay 301 to ground. Relay 301 operates over the above-traced circuit and at .armature 351 closes anobvious circuit ltor relay302. Relay 302 operates and closes the usual impulsing circuit.

Thus the subscriber at substation A upon dialling the two digits 0 and 1 is connectjed with incoming selector S in Y oiiice .through repeaters OR Yand IR. The subscribers'loop controls relay 202 of the re.-

vpeater OR. Relay 202 controls the loop over whichrelay 236 of repeater IR operates.

x-Thetwo loops are inductively connected by repeating coil R. Relay 236 controls the loop over which. relay 301 of selector S operates. This loop is inductively connected vwith the loop between repeaters OR and IR by repeatingcoil R1. y Y

. It will now be assumed that the third digit dialled by the callingsubscriber is the digit 0, vRelay 202 of repeater OR responds `to each interruptionof the calling loop, devenergizing and reenergizing ten times. With each deenergization of relay 202, the loop circuit to relay 236 of repeater IR is opened and relay v236 deenergizes and reenergizes' in response.l VEach deenergization ofrelay 236 cpens the loop circuit of relay 301 o selector relay y301 deenergizing and reenergizing in response tothe interruptions. VThe impulses from the calling device are thus repeated to the incoming selector inthe distant oliice.

lSelector Sis of the ordinary Strowger type whose operation is well known in the vart. It is therefore thought unnecessary to describe its operation in detail. -Relay 301 Vresponds to the dialled impulses and the ver tical magnet operates tof'step the wipers to the tenth level. Relay 304 and the rotary 4magnet'then cooperate to step the wipersonto the bank contacts and hunt for an Aidle When an idle trunk is found, for example the trunk comprising conductors 329 to 332,' inclusive, relay` 305 operates, disconnecting line relay 301 from the control loop and switching the loop .through the succeeding switch.

The loop from therepeater IR is thereby extended to the line relay 404 of repeater AOR2, circuitsof which may be traced as follows: battery, upper windingof relay 404, contacts controlled by armature 416 of relay 405, upper left hand winding of repeating coil R3, trunk conducto-r 329, bank Contact 321, wiper 311 of selector S, armature 358 of relay 305, trunk conductor 250, thence through the loop in repeater IR over which relay 301 previously operated, trunk conductor 251, armature 361 of relay 305, wiper 312,i`

bank contact 322, trunk conductor 330, lower left hand winding of repeating coil R3, conp tacts controlled by armature 417 of relay 405,

through the lower winding of relay 404 to ground. Release trunk conductor 252 upon C which ground is rplaced by relay 231 of repeater IR is extendedby'way of armature 360 of relay305,wiper 313, bank contact 323, trunk conductor 331, normally closed contact winding of relay 407 to battery. Metering conductor 253 is extended by way vof armature 359, wiper-.314, bank contact 324, .trunk conductor 332 to contacts at armature 418 of relay 405.

traced loop circuit and at armature 412 connects the upper windingo-f relay 402 to trunk conductor 428 by way of the upper right hand winding repeating coil R3 and armature 425 5 Y of relay 407. At armature 413 van obvious circuit is closed for relay 406. Relay 406`opcrates and at armature'421 closes a point in and armature 457 of relay 453 through the 'T80 Y i OR2. Relay 404 operates over the previously the circuit of relay 405, at armature 422vcon- -nects an additional groundY to release trunk conductor 331, at armature 423 connects ground to trunk conductor 429 byl way of lower right hand winding of repeating coil R3 and armature 427 of relay 407, and at armature 424 closes a point in the circuit of relay 401. .I

The loop circuit is thus extended to revpeaterfIR2 Vincluding lower winding vof relay 503, contacts ycontrolled by'armature 513 of relay 502, left hand windings of repeating Vcoil R5, armatures 511 and 512 of relay 501,

trunk conductors 428l and 429, armatures 425 and 427 of relay 407, right hand windings Vof repeating coil R3, to ground at armature 423 of relay 406, and to battery through the upper winding of relay 402. Relay 402 operates over ythe above-traced circuit and opens a po-int in the circuit ofY relay 405'. Line relay 503 of repeater IR2 energize in series with relay 402 over the previously traced circuit and at armature 514 removes ground from th-e impulsing conductor ofthe repeater, and at armature 515 closes an oby vious circuit for relay 504.v Relay 504 operates and at armature 516 closes a point in the circuit of relay 506; at armature 517 closes a point in the circuit of relayY 505; at armature 518 closes a circuit from ground through relay 507, conductor 510, oftnorinal contact 539 of selector S2, windings of relays 531 and 533 to battery. Relay 506 is not on the impulsing lconductor of the trunk.

i `Relay 505 does not operate as `thecircuit is opened at armature515 .of -relay :503. Relay ,507, however, operates over the above-traced circuitand atarmatures'A 524 and 525 connects trunk conductors 508 and 509 to the repeater. `.The visual signal 582 operates from ground on .signal lead 581 to inform the `operator 'that the trunk is beinglused.

" lRelays 531 and 533roffselector VS operate in '.serieswvith relay507`in the circuit previouslyV traced.v Relay 531, uponoperating at armature 540conneots impulsing-rela-y 532 jtov Vtrunk conductor 508, at armature 541 con- -nects itstownlower Winding to trunkco'nf :ductor 509,-and atV armature 542 opens a point inthe circuit of the release magnet andn closes a pointlin the `vertical impulsing circuit. Relay 533 upon operating. atarmature 545 connects relay5'34- to test Wiper 554, lat armature546 connects its own lower Winding and upper'Winding in series with resistance i536 to control conductor 510,* and at armature 547 closes a. point in the rotary circuit.

Incoming selector S2 VisV now readyatore- 'ceivey the calling subscribers fourth digit. Assuming Vthat-the `digit nine is now ldialed, the interruptions of the calling loop will be 'repeated byrepeatersV ORy and IR as. pre- 4:viously described lto relay-404 of repeater ORL. Relay'404deenergizes and reenergizes in? response tothe repeated impulses. vWith `each ideenergization of relay 404,1the previouslyvtraced loop circuit of relay is opened at the armature`412 of frelay 404.

With each deenergization of relay`404 a circuit is closed for relay 401 at armature '413, this circuit also includes armature 424 of relay 406. ARelay 401operates on the first deenergization `of relay 404 andremains energized during" the series ofimpulses due to its slow release character. `Relay401v closes a holding.; circuit for the floweriwvinding of relay 402 at armature 408. Relay'402- therefore remains energized when its initial enen vgizing circuit is interrupted atthe contacts ofrelay 404; Shortly after the last impulse Vof the series, relay 401'deene`rgizes and opens the holding circuit of relay 402 energized-over the loop. Y Y

As relay 404 opens its upper contactsI in response to the dialled impulses, the circuit of relay 503 ofrrepeated IR2 will be opened a like number of times land relay 503 will respond. With each 'deenergization of relay 503, a circuit Will be closed from ground,-

armature 514 of relay 503, upper right Yhand Winding of repeating coil R5, armature `524 of relay 507,;trun'kconduotor 508 to selector Slj, armature 540 of relay 531, -Winding of relay v532 ,tol battery. A lcircuit for relay 505 is also vclosed from grounded armature 515 of relay 503 and -armature1517 of relay A504. Relay 505 operates on theirst impulse .and l:remains operatedA throughout :the 'series of impulses ,due toits slow` release construcr tion.jf-;Relay 504 is also yslovvto releaselfa'nd -remainsoperated lwhen. its circuit is momen-,N Renyteml above .traced circuit Ain response. totth'e-fvre- Y '.peated impulses-and closes the 1circuit of the 'vertical magnet a: like number oftinies.: .The -lveitical magnet `operates fand steps fthe switch yfshaftand `Wipers 'upto' the calledlevel.; ffllhe '30 olnormalv-'springs 539` and 1557"- operate' on the rst `verti'c'alstep of thelshaft fopeningthe initial energizing circuit ofrelays531` and '533iA `Relay V533,remainsenergized overt'he previously traced lockingfcircuitincluding.imi

its upper` andlower xvlin'dingsl and'V `resistance 536 in series.'-V Relay531 remainsope'rated during the series'of impulses, it'slower Winding beinge'nergized 'rol'n-batteryy vvon trun'kconductor 509. l e Y y Shortly after the lastlim'pulse of theseries', relay 505 of repeater-TR2 'deenergizes and Vopens the holding circuitof relay 531` which 'also deenergizes". Relayf531 on'fdeenergizing closes the usual rotaryv stepping y,circuit-and selector S2 searches foran idletrunkfi-n the l usualmanner.y j- [f On," reaching-an idle trunk `which willfbe Yassumed `to' -be that comprising vconduct'ons i561 *to 563, inclusive, `terminating von A"contacts'558 to 560, inclusive, relay534 'Wfill operate over a-circuit includingrelays-inthe succeeding A'switch `corresponding to relays 531"and533 of Vselector S2. Relay534po1rop erating ati armatures 548 and 549 switches trunk condu'ctors508yan'di509 through to conductors 561 land 562 by Way of wipersr552 e and 553 and contaets558 and559. Y f- 'if f g The trunk comprising conductorsl I 561to 563, inclusive, 'extends tov a'regularselector vS5 of the localswitch train of office JZ. "This trainniay include one or more ranks Jof Aselectors and a-rank of connectors. the resi l `Inainder ofthe digits are dialled by theca'lling subscriber,i'relay 503 of repeater I'RZTIesponds andrepeatsfthe impulses to` the lsuc# ceeding switches* in' thev same manner as Idej-` scribed for selector S2. SeleotorSZ-icannfot operate from these impulses r,since impulsing relay 532," is disconnected from the trunk at armature 540 ofrelay 531 `and the energizing circuit vof relavi'5'31 is'open at 'the operated off-normal spril'gs.` v g -g Thefreinaining digits operate 1 the f inter-f; f mediate selectors andthe 'connector' in afinanf- 125 ner WellVV known Vin the fartto connect with the/Wanted line suchv as A4." lIf'fthfe'lineis busy, a busy tone will lbe returned? by theflconiV nector to informthe 'calling partyf that" the Wanted line is :not available Whereonfthe C SI5 calling subscriber will replace the receiver. Ifj the wantedfline-is idle, the connector will signal the called' station in the usual manner andreturn a ring-back tone to the calling subscriber.

When the called subscriber answers, the ringing current is cut-olf in the usual manner and the connector Vplaces aground on the upper trunk conductor. This ground extending back through `thelocal -switch train'over conductor 561, contact 558, wiper 552, armature 548 of relays 534 in selector S2, conductor 508, armature. 524 of relay 507 in repeater IR2,farmature 516 of relay 504, armature 520 of relay 505, resistance`523 to relay 506. Relay 506 operates and at armature l526 closes a circuit for relay 502 including armature 518 of relay 504. Relay 502 operates and at contacts controlled by armature 513, disconrnects the lower winding of relay 503 from the -controlloop and connects the upper and low'- `er windings in series across the loop.

As previously described, relay. 402 energized over vthe control loop in series with the lower winding of relay 503. When both windings of relay 503 are connected in' the circuit, the current ow in relay 402 is reduced and relay 402 deenergizes. Relay 402 on deenergizing closes a circuit for relay 405 at armature 409 and the armature 421 of relay 406. Relay 405 operates and at contacts controlled by armatures 416 Land 417 reverses battery .over the loop vfrom repeater IR'by means of the usual reversing circuit. Relay 405 at armature 414`closes a locking circuit 'for itself; Aat armature415 vcloses a point' inthe circuit of relay403 which has no connects metering conductor 332 which extends back through selector S to metering conductor 253, to a Contact in the left hand ,Y bank of rotary switch RS through resistance 436; at armature 419 removes Vground from the right hand bank contactsof rotary switch RS; and at armature 420 connects a lead from the interrupter to the rotarymagnet of rotary switch vRS. Interrupter 'INT is adjusted to send out. ground impulses at predetermined intervals. Each impulse 'causes the rotary magnet 434 to energize. When the rotary magnet deenergizes after each impulse, wipers 430 and 431 are advanced one step in a counter clock-wise direction. On the first rotarystep, battery is connected to a meter lead. 332k by way of wiper 430, Contact 432, resistance 436, and armature 418 ofrelay405. The rotary switchcontinues to step as long as relay 405 vis energized Vand at each ltwenty-fifth step, closes the above-traced circuit for the meter lead. It is obvious that the interval between metering impulses can be varied by' adjusting the speed of the interrupter or by attachingthemetering conductor to other bank contacts. p,

As vpreviously;-mentioned, relay 405 refunction at -this time; at armature 418 verses the directionof ycurrent flow in the I control loop. The loop ras previously described,includ'es the upper winding of potrolled by armatures 245. and 246 reverses the Y trunk conductors 207 and 208 with relation to relay 236, at the same time connecting the upper winding of relay 232 in series with the upper winding of relay 236., Relay 232 op- Verates and at armature 240 disconnects its? upper winding from the previously men-l tioned series circuit and connects 'the upper winding of relay 236 directly to the loop circuit; atl armature 241 closes a locking circuit for its lower winding to ground inthe'- release-trunk; and at contacts controlled by armature 242 disconnects the lower winding of relay 236 from the trunk and closes a short circuitaround condenser 237 including armature 245 of relay 234. The trunk circuit has now been changed from .the loop type to the simplex type. The upperi winding of relay 236 is now connected with both conductors of the trunk by way of armature 240 of Y relay 232, contacts controlled by armature 243 of relay 233, contacts controlled by armature 246 of .relay 234,v and the short circuit around condenser 237 previously closed by relay 232. Relay '236 remains operated 'over a circuit which will be described hereinafter.` Y y 'f Relay 233 is connected to meter leadk220 and operates with each metering impulse transmitted over the lead from repeater OR2. Relay Y 233 on operating, at contacts controlled by armature 243,disconnects the upper winding of relay 236 from 'the trunk conductors and connects it to a holdi'ngground. The simplex trunk is therefore cut dry with each metering impulse, that is, battery through the upper winding of relay 236 is disconnected. l f

VCurrent flow was reversed inthe control loop extendingvfrom. repeater OR by the operation of relay 234'in repeater IR. The reversal of current liowv in the loopV which includes the upper winding of relay 201, causes the two windings of this relay to assist cach other and the relay operates. Relayr 201 on operating short circuits condenser 209 at armatures 210r and 214. A branch of the short circuiting lead extends through the lower winding of relay 203 to ground. Ground through relay 203 is thus connected to both sides of the trunk and serves to maintain relay 203 and also relay 236 of repeater IR energized over a simplex circuit including both trunk conductors. vRelay 201 at varmature 211 also opens the initial energizing winding of relay203, and closes alocking circuit for its own lower winding by short circuiting resistance 206; at contacts controlled by armatures 212 and 213 reverses the current flow over trunk conductors 167 and 168l in the usual manner; and at` armature 215 closes a point in the metering circuit including conductcr170. Y

As previousy described, metering impulses transmitted from repeater @R2 cause the periodic operation of relay 233 ot repeater IR which on operating` cuts the simplex trunk dry byV disconnecting Ybattery which is fed tothe trunk through the upper winding of relay 236. Each time battery is disconnected Afrom the trunk, relay 203 ot` than theV unit charging interval-,the second" revolution of the wipers of rotaryfswitch RS associated with repeater OR?A will cause thiz meter to register again. Thus at vregular pre-determined intervals during the course of the connection, the meter will be operated to registerthe charge on the basis of duration of the'call.

tjthe termination ofV the conversation both subscribers will restore their receivers. li the called subscriberhangs up lirst, no-th" ing happens, as the connector is ordinarily arranged for release by the last party. The connector, however, maintains the ground on the upper trunk conductor so that the'callsubscribers meter will continue to reg ister until the receiver is restored. lVhen the calling subscriber restores the receiver at substation A. the Gallinoloo will be opened at the switch hook springs inthe usual manner.` Relay 2020i repeater OR which wasenergized over the loop will retract its armatures, opening the simplex circuit to'repeater IR inthe distant oiiice, and opening the circuit of relay 204. .Relay 204 restores, removes ground from the release trunk conductor 169, opens, the holding circuit oi2 relay 201, and opens a point in the simplex circuit'to the switch ahead.V Relay 205 deenergizes assoon as ground is removed from the release trunk and switches the trunk conductors 207 and 208 back to incoming connector C1.

tors in the normal manner. Relay 203 ref stores when the second point Vin the simplex circuit is opened by relay 204.- The repeater is now in normal condition.k x 1f i `The removal of ground fromthe release Relay 201 restores and ref connects line relay 202 to the 'trunk conclue-' trunk asabovedescribed causes relays 111 ,i

and 101 of connector C, and relayr3 oflin'e switch LS to deenergize. Relay 111 on re- 4 storing disconnects the line wipers from the talkingconductors, connects test wiper 117V,

in the normal testing circuit andclosesa point in the circuit ofthe rotary magnet. Relay 101 on restoring switchesthe trunk conductors back to line relay 103,A opensa point in the' metering circuit,v andcloses `a circuit for the release magnet including armature 129 of relay 103, armature 131 Aof relay 104, andV operated oi-normal spring contacts 120;V Release relay 114 energizes and permits the switch shaft andwipers to restore to normal in the usual'mannen Theshaft von reachingits normal position opens the circuit `ot. therelease magnet-, at the o'tl'fnormal` springs, and closes a part of the normal energizing circuit otrelays v104 and 105.

` Relay 3 of theline :switch LS restores and reconnectstlie 4line conductors to line relay l 233-restores1f `Relay 236 opens the loop'circuit to the succeeding` switch and also opens thecircuitbfrelay 231. Relay 2,31 deener-V` V4 and' `ground respectively. i The wipers re-l l mainfon .thecontacts of the trunk Just used..V

W hen. the control" loop isV openedin regia-es and removes ground trom Vthe release trunk conductor'- 239 and also disconnects rebusy condition being removed, repeater ORl rcan now -be seized for another call. Ground being removedA from the "release trunk, re-

lays 232 and 235 deenergize'. Relay 232 on Y,

restoring changes the simplex holding cir cuit back to a loop'circuit and opens itsf o wnholding winding. Relay 235 on deenergizing Y Vopens the circuit of relay 234,-which restores and connects relay 236 to the trunk conduc- A tors in the normal manner.V

The removal Voi. ground from release trunk Y conductor permits the restorationvof relay 305 of selector'S; Relay 305 closes the usual Y circuit for the release magnet which causes r- The holding loop for relay'404 of repeater OR; being openedV at repeater IR, this relay deenergizes.V Relay404 opensl apart of the loopfcircuit to the 'switch' ahead and opens the circuit of relay 406. Relay 406 deenergizes and opens thecircuit` of relays 401, which operatedV momentarily when relay 404 deenergized; opens the holding circuit `of relay 405 and removes the Vadditional holding The release lease trunk 'conductor 282 of repeater 0R,L 490 V from ground and connects it to relay261. The

1110V f Y ground from the release trunk to the preceding switch.

Relay 402 deenergizes inmediately after the release of relay 401, its initial energizing circuit being open at contacts of relay 404 which has deenergized. Relay 407 deenergizes as soon as ground is removed from the release trunk and switches the trunk conductors back to incoming repeater lRl. Relay ,405 deenergizes and opens a point in its own holding circuit, opens a part of the circuit of relay 403, disconnects metering conductor 332 from pulsing mechanism M, connects a ground tothe right hand bank contacts of rotaryswitch RS, and disconnects the interrupter lead from the rotary magnet. lf the wipers ot rotary switch RS are in their home position no action takes place; however, if the wipers are in any other position a circuit for the rotary magnet will be closed includingarmature 419 'and' normally closed contact of relay 405, right hand bank contact of switch RS, wiper 431, and rotary interrupter springs 435. `The rotary magnet energizes, opens its own circuit at the interrupter springs, and in deenergizing steps the wipers ahead. This operation 1s repeated as longv as wiper 431 encounters a grounded contact. wWhen the home contact is reached, no ground being found thereon, the stepping operation ceases. All relays of repeater @R2 having restored, the switch isl now in normal condition.

The loop circuit for relayV 503 beingopened at repeater ORz, the relay deenergizes and opens the circuit of relay 504, and closes a circuit for relay 505'. Relay 504 deenergizes, opens a point in the circuit of relay 506, opens the circuit of relay 505, disconnects signalling lead 531 from ground and connects it to cutoff relay 501, and removes ground from relay 507 and control Ylea-d 510 to the selector. Relay 505 deenergizes, the' momentary energization when relay 503 restores has no utility. Relay 506 deenergizes and opens a point in the circuit of relay 502. Relay 502 deenergizes and again connects the lower winding of y relay 503 tothe trunk conductors. Relay 507 restores and disconnects trunk conductors 508 and 509 from the repeater.

In selector S2, relay 533 deenergizes when ground is removed from control lead 510. Relay 533 disconnects relay 534 from control wiper 554 and closes a part of the release circuit. Relay 534 restores, disconnects Vwipers 552 and 553 from trunl7V conductors 508 and 509 and completes the circuit of the release magnet kincluding operatedcontacts 557 ofthe oli-normal springs. The release magnet energizes, the shaft and wipers return to the normal position in the usual way.,-

and the circuit of the release magnet is again opened at the off-normal springs.

The local switch train following selector S2 releases m the'well known manner.

It will now be assumed that the subscriber at substation A in X oliice desires a connection with a subscriber in a nearby town to which a suburban service is maintained. The calling subscriber dials the digits required for reaching selector S2 asY described in the preceding connection and is connected with selector S2. Assuming that the subscriber now dials the digit 0, selector S2 operates as described beterel and selects an idle trunk on the tenth level, for example the trunk com.- prising conductors 564 to 566, inclusive, terminating on contacts 555 to 557, inclusi-vc, leading to operators position OA.

It will be recalled that selector S2 extended a ground through relay 534 over control wiper 554. VThis ground extends byk way of contact 550, conductor 557, through the short circuit around the upper winding otrelay 572 including armaturesr57 3 and 575 of relays 571 and 572, respectively, t irough the lower winding of relay 572 to battery. Relay 572 eneroizes and opens the short circuit around its upper winding. Relay 572 remains enerfrized over both windings in series and' at armature 576 closes a circuit for the supervisory lamp including armature 57 470i relay 571. he supervisory lamp now burns to inorm'the operator that a call has been eX- tended.

To answer the call, the operator inserts the answering plug of a regularcord in the answering jack and establishes a talking connection with the calling party in the usual way. rllhe insertion of the plug into the jack also closes an obvious circuit for relay 571 which operates, opens another point inthe short circuit around the upper winding ot relay 572 and opens the circuit of the super-4 visory lamp. The supervisory lamp is now extinguished at all positions in which the trunk is multipled, indicating that the call has been answered.

The operator determines the number of the wanted subscriber and extends the call by means of the other plug of the answering cord. Y

When the calledV subscri1 er answers,` the operator is so informed by the usual supervisory sien als in the cord. The operator then momentarily depresses the meter key, which connects ground to trunk conductor 564 at contact 577. Relay 506 ot repeater IR2 operates from this ground in the same manner as when the connector placed a ground on the upper trunk conductor. Relay 502 operates and connects both windings of relay 503 in series in the control loop whereon relay 402 of repeater deenergizes as previously described. Tlie operationv of relay 405 and metering device M takes place in the same .manner as on a call to a subscriber iny Z otlice.

The-.operator then releasesrthe meter key which removes the ground from conductor 564 Y whereon relays 506 and 502 of repeater IR2 restore. The lower winding only of relay 503 is now connected in the control loop and relay 402 again attracts its armatures. Relay 405, however, remains locked up through its` upper' armature. Relay 402 on energizing closes a circuit for relay 403 including armature 415 of relay 405 and the upper ar` mature 409 of relay 402. Relay 403 operates and at itsrupper armature closes a locking circuit for itself independent of thecontacts of relays 402 and 405. RelayA 403 at armature 411 connects another contact of the left hand bank of'rotary switch RS to the meter lead 332. `With each revolution of theA wipers, two metering impulseswill be transmitted as wiper 430 passes over` contacts 432 and 433 ofthe bank. rIhe metering impulses are repeated back tov the calling g subscribers meter in the same manner as previously described for calls to Z oice subscribers.

At the termination of the call,.the'oper ator receives the usual cord supervision when either party .hangs up.k The operator then removes .the plug from the answering .jack and the switches restore to normal as previously described. Y i i 'I'he operations involved in setting Vup a call from the subscriber atsubstation A (Fig. 1) in X oiiice to the subscriber at substation A3 l7) in Y ollice will'nowbe. considered.V The subscriber at substation A lifts the receiver and dials the digits O and1 calling loop through repeaters OR and IR t0l selector Sf exactly as described for a call to Z oce. rIihe third digit operates selector S which selects an idle trunk as previously described. It will be assumed that the third digit dialled was 9 and that the wipers of selector S stop'on contacts 325 to 328 associated with the trunk comprising conductors 325 to 328, inclusive, terminating in connector C'g (Figi'). l

Connector C2 is an ordinary Strowgertype connector, the operation of which is well known in the art. It is therefore thought unnecessary to describe its operation in detail. When selector S switches through, the control loop from repeater IR is extended t0 line relay 702 of connector C3. Line relay 702 and release relay 703 operate in the usual manner. The subscriber then dials the last two digits of thev called number, theinterruptions of the loop being. repeated by repeaters OR and IR as previously described.

Line relay 702 of connector G3 operates in response to the repeated impulses and completes the usual vertical and rotary stepping circuits. The wipers 735, 736 and 737 of the connector Awill be advanced to the contacts of the called line .which will be assumed to be contacts 738, 739i`and 740 associated will encountera ground `on contactV 740 and test relay 7 0610il the connector will. operate."

which permits the back contacts to open but L prevents the front contacts from closing. This. cuts od the normal battery and ground connections from the line but d oes not close through a. circuit to the wipers. i

When the calledA subscriber lifts the receiv-v er at substation A3, a direct current circuit is closed for the upper winding of ring-cutofi' relay 705 of the connector.V Relay 705 Ifthe called'linev is idle,

operates and inl the usual manner cuts oli' the ringing current and connects the talking conductors through to the baclt-bridgeirelay 701.

Relay 701 feeds batteryand ground to the called line. and operatesover Vthe calledv subf scribers loop. Relay 701 on operatingreverses the trunk conductors withv relation'to line` relay 702 Vwhichreverses the direction of the currentflowin the control loop. `Relay 2350 repeater IR operates when-the current flow is reversed in the control loop,` and'.

changes the control loop between repeaters @Rand IR to a simplex holding-circuit as described under calls to Z oliice.` As inthe previously described connectioinrelay 236 through its upper winding and relay 203 through its lower winding are energized in series over the simplex circuit.

When relay 705 of the connector operates it also connects battery to metering conductor 344 through resista/.nce 709.*Y VRelay 233 of ref peater-IR operates vfrom this battery,- closes Va holding circuit for relay 236 and cuts oflthe battery from the simplex circuit. Relay 203 of repeater OR deenergizes and closes the metering circuit as previously described which causes the meter associated with line switch LS to operate. i

During the conversation the voice currents will be transmitted over the dry simplex circuit to repeating coil R by which Vthe simplexcircuit is inductively connected to the calling subscribers loop. Atthe end ofthe. conversation, both subscribers Willrestore their receivers andthe switches will release Y in the Vmanner previously described. It is the calling subscribers meter]V will register only'once on calls from X to Y oilice. g i The connections dealt Vwith,up to this time have involved trunl'ring between two or more offices. The operations involvedV in a Vcall from substation A to substation A1, v bo-thin y X office will nowbe considered.

1 When the subscribe-r at substation lifts the receiver, line switch operates as previously described and selectsan idletrunk which will be assumed to be the trunk terminating in connector C. Connector C responde to the rst digit in the same manner as described under trunk calls and steps the wipers to the called level. It will be assumed.V

that the digit 9 is dialled and that the wipers are raised to the ninth level. Y The operations so far have been exactly the same as for trunk calls except that the shaft springs are not operated when the shaft and wipers reach the ninth level. The connector now responds to the second digit which will be assumed to be a 5 and the wipers are rotated into engagement with contacts associated with line 95. This line for example may be the one comprising conductors 171, 172 and 173 terminating on contacts 163, 164, and 165 and leading to line switch LS', associated with substation Al. Contact 166 of the banks is multipled with Contact 165 on individual lines.

1f substation A is busy, test wiper 117 will encounter a ground onv contact 165. Referring to the first connection described, it will be understood that relays 109 and 110 of connector@ are-operated during the rotary iinpulsing. Relay 108 which is connected tothe test wiper by way of contacts controlled by armature 149of relay 110 operates from the ground encountered by the test wiper. As contacts`165 and 166 are strapped together, wiper Y118 will also encounter a ground. Shortly after the last rotary impulse relay 109 deenergizes and at armature 1115 closes a circuit for the lower winding of relay 110 to ground on wiper 118. As previously eX- plained, the two windings of relay 110 oppose each other and vthe relay deenergizes. Relay 109 on deenergizing also closes a point inthe circuit of relay 107 but this relay does not energize since its circuit is also opened at armature 152 of relay 110 which is now deenergized. Relay 108 on operating closed a point in its own locking circuit, closed a point in the circuit of the upper winding of relay 110, opened the rotary impulsing circuit, and closed a point in the busy tone circuit. Relay 110 on deenergizing opened the circuits to both its upper and lower windings, disconnected the test wiper from relay 108 and closed a point in the locking circuit of that relay, removed the shunt around the armature lil-3 of relay 108, opened a point in the circuit of relay 107 and closed'a pointl in the busy tone circuit. Busy tone is now applied to the lower talking conductor to inform the calling subscriber that the called line is not available at this time. The calling subscriber then restores the receiver and connector C and line switch LS return to normal as previously described. y

In case the called line is idle, the ltest wiper will find battery potential on the testcontact and relay 108 will not energize. When relay 109 falls back shortly after the last rotary impulse, the circuit of the upper winding of relay 110 will be opened. Relay l110 on deenergizing switches the test wiper from relay 108 to the lower winding of relay 111. A circuit is thus closed from ground 4on the release trunk, contacts controlled by armature 155 of relay 1 11, armature 141 of relay 108, lower winding of relay 111, armature 149 of relay 110, test wiper 117, test con'- tact 165, conductor 173, winding of relay 3 of line switchy LS1, interruptor springs 17 winding of magnet 5 to battery. Relay 111 operates over the abovetraced circuit and at armatures 154 and 158 connects the line wipers to the ringing equipment; at contacts controlled by armature 155 opens a part of the circuit of its own lower winding and connects testy wiper 117 to they grounded release trunk; at armature 156 closes a locking circuit for its own upper winding; Vand at armature 157 opens the circuit of the rotary magnet. v

Relay 3 of line switch LS'l energizes in series with relay 111 and mo-ves its arma-` tures far enough to open the back contacts but not enough to close the front contacts.

The complete stroke of the armatures is pre-V ventedby a mechanical locking device controlled by line relay 4E and is well known in the art. r1`he partial'operation of relay 3 disconnects the normal battery and ground connections from the called line. y

Ringing current is now automatically sent over the line at intervals controlled `by the ring interrupterto operate the bells at substation Al. It will be noted that the ringing circuit includes theV lower winding of relay 106, and that during the silent period aV ground is connected to the lower trunk coii- Y ductor. When the called subscribed at substation A1 answers by lifting the receiver, a direct current path is closed over which relay 106 energizes, Relay 106 on energizing, at armatures 135 and 138 opens the ringing circuit and switchesthe called line loop through to back bridge relay 102; at armature 136 connects battery to metering conductor 21; and at armature 137 `closes a locking circuit for itsown upper winding. Relay 102 feeds talking battery to the called subscriber and operates over the called subscribers loop. Relay 102 on operating Vreverses the trunk conductors with respect to line relay 103 by means of the usual reversing circuit. The reversal of battery has no utility in this connection. The meter associated with the calling line switch LS energizes from the battery on the metering conductor.

At the termination of the conversation, both subscribers replace their receivers and the switches release-as previously described.

The meter associated with line switch LS Y remains energized throughout the connection and consequently registers only once for J. i Y the call.

A call from the operator Z otlice toa subs'criber at substation A will now be described. The operator observing that the trunk circuit OC is idle, inserts the calling plug of a armature 511 of relay 501, trunk conductorV 428, armatureV 425 of relay 407 in repeater OR2, upper rightliand winding of repeating coil R4 `associated with repeater IR1, upper winding of relay 451, normally closed lcontacts controlled by armature 456 of relay 452, lower right handwinding oi repeating coil R4, arma-ture 427 of relay A407, trunk conductor 429,'armature 512 oi'relay501,

lower left hand winding ot repeating coil R6 to ground. Relays 591 and 451 operate over the above circuit. Relay 591 on operating opens the short circuit around condenser 584 and this opens the loop through the operators cord circuit extinguishing the supervisory lamp (not shown). Relay 451 onoperating closes an obvious circuit for relay 453 and also Vcloses a part of the loop circuit to the line relay of incoming selector S1. V Relay 453 on operating at armature 457 opens the circuit of relay 407 and grounds the release trunk of repeater OR2 to mark that repeater busy; at armature 458 completes the loop circuit to selector S1 including the Vupper winding of polarized relay 452 and impedance coil 454; and at armature 459 closes a circuit for Jthe lower winding of relay 452. Relay 452 does vnot operate at this` time as its two windings oppose each other.

l .Selector S1 is exactlythe same as selector S previously described and, therefore, its

operation will not be described in detail. The lineV relay energizes over the loop ex-V tended by repeater IRl. The selector is now ready to receive the iirst digit.

In order to dial, the operator presses the dial key which is a locking key. At contacts 586 and 587 the battery feed to the control loop is transferred from the lower winding of relay 591 to resistance 583 through the impulsing contacts of the calling device or dial. A locking circuit for the upper winding of relay 591 is closed at contacts 585 to keep this relay energized during the dialing so that normal vsupervision will be given in the cord circuit. The operator then dials the lirst digit. Assuming the first digitto be an 0, the control loop is momentarily opened ten times. Relay 451 oi" repeater IRl responds to the interruptions and' at in turnrepeats the'int armature 458 interrupts the loopto selector S1 a like number of times. TheV line relay of selector S1 responds to the loopl interruptions in the usual way and the wipers of the y i selector are advanced to the tenth level. The4V switch then cutsV in and-rotates the wipers@ Y into engagement with the contacts of an idle trunk, for. example contacts471 to474, in-

elusive, associated with the trunk compris-f` ing conductors 280` to `283, inclusive, termi# nating 1n outgoing repeater 0R11, l

. The control loop is thus extend ld from refM way. of wipers 461 and 462, contacts 471"a1 id"472;l

peater IRM through selector S1- by trunk conductors 280 gandf28l, right lhand windings of repeautingv coil R2 of repeater y ORl, normally closed` contacts controlled by` armatures 271 and Y272 of relay 263, through the upper and lower windings oirelay264y l tov battery and ground'respectively. The r`e lease trunk -is extended from the selector by way of; wiper 464, contact 47 4, conductor 282,

armature 239 of relay 231 of repeater IR, to y -relay 261 of repeater ORl; Re'lay`261oper--V ates and switches trunk, conductors 207 Vand 208 from repeater IR to repeaterORll The `metering conductor is also extended'from se-A y lector S1 by way owiper 463, contact 473,` V Y and conductor 283 to repeater @R1 but has no utility in this connection.` Relay 264 operates over the loopV extended from repeater IRM' closes an obvious circuit for relay 2,651'and completes a loop circuit to the line` relay `of incoming connector C1, including trunk co-n ductors 207 and 208, armatures 268 and ,269i of relay261, armature 274 of relay 264,1ett hand windings of repeating coil R2, resistance 267 and upperwinding of polarized relay 262. ground on the release. trunk toholdup `selector Sl and to maintain relay 261 energized, and closes a circuit for the lower wind-y Relayl 265 operates and places.'` 5

ing ofrelay 262. Relay 262 does not operate. y

at'this time as'theV two windings opposeeach V n 1 1,10

' i 1 A r ConnectorCl is exactly the saine as lconnector C and it is therefore unnecessarylto ex.-`

plainits operation in detail. Tlieline relay,

corresponding to relay 103 ofconnfector C, energizes over the loop extended from repeaterjOR]L and` closes the circuit ot--relay 104 which corresponds to release relay 104 of connector@ Relay 104 grounds the release trunk of connector C to mark `that switchbusyvand opens` the circuit of cut-oli" relay` 205. `The second and third digits are now vdialled by the operator.` The loopinterrupti-ons are repeated by .relay 451 of re-` peater IRl to relay 2640i repeater ORlywhich. err'u"` tions. V,to the line l' relay of the manner and eladvancedto relay of connector C connector responds'i; wipers 116^ an the contacts of the assumed to be' cont high wiufbe. i

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