US1860213A - Telephone system - Google Patents

Description

I y 24, 1932 Q D. A. CHRISTIAN 1,860,213

TELEPHONE SYSTEM Fil May 22, 1930 5 Sheets-Sheet 1 4M I {a t (II) L L I SM? A Fig.4.

cm tsl 0W ZAW. M

May 24, 1932. D. A. CHRISTIAN TELEPHONE SYSTEM Filed May '2 1930 5 Sheets-Sheet 2 SIAF May 24, 1932.

D. A. CHRISTIAN TELEPHONE SYSTEM 5 Sheets-Sheet s Filed May 22, 1950 y 1932- v D. A. CHRISTIAN 1,860,213

TELEPHONE SYSTEM Filed May 22, 1950 5 Sheets-Sheet 4 rdsb r 5 May 24, 1932. D. A. CHRISTIAN TELEPHONE SYSTEM 5 Sheets-Sheet 5 iled May 22; 1950 o c V .k E. 3% w H a .E

V v Patented May 24, 1932 a DAVID ADAM criiusrrnn, or LONJfiON, ENGLAND, AssIGNoR iro simmes afi ens & COMPANY LIMITED,; or ,LoNDoN, ENGLAND r TELEPHONE sYsrEM App1ica'tion'fi1edMay22, 1930, Serial No. 454,712; and in Great Britain May 31, 1929.:

The present inventionrelates to "automatic telephone systems and more particularly to arrangements for settingup connections and exchange interconnections in multi-exchange areas. It -is particularly. applicable to the requirements of rural telephone areas where exchanges may b'eunattended and cheapness is-desirable, but it may also be-used in connection with'si-ngle exchanges.

"lhemain featureof this invention is that an exchange apparatus termed an operator circuit, which is available to a number of connecting circuits, wexercises a watching iunc} tion when a connection isbeing set up and 1 exercises certain other fllIlCtlQIlS in respect of allbut the most ordinary calls. For instance;

thejconnec'ting circuit switches may deal with calls between ordinary subscribers butas regards calls to'party lines theoperator circuit receives impulses to select the appropriate ringing circuit. Thus, the operator circuit receives at least 'as ;many :dialled impulses as are required to determine the nature of the call and when it is obvious that no further control "by the operator circuit of operations at the'exchange is required, it may be m lunged that 'no further digits are recorded or digits may be recorded Without the operator circuit exercising "any control. .The operawith the connecting circuit liorthe purpose of supervision (which :may include call meter- 'unti'l'the calledfsubscriberjreplies or if V heis engaged,the connection is dropped. I The arrangements of the invention permit of several modifications to fitin with the layout of :the area and the numbering scheme employedp'butin general, impulses dialled by a su'bscriber'iare"received at an exchange by the selector of the connecting circuit and in the bpemtor circuitj'thie latter generally use apparatuszconnectedoto'the incomingcnd "associated, an operator circuit being availtorcircuit'mayhowever'remain in connection 'cuit with which an {operator circuit maybe 7 ableto a number of incomingjunctions', and c it may be provided that a junction is only marked free at itsoutgoing end when it-has. an operator clrcuit associated WliJlLliiS11190111 1 mg end, one or more junctions from :an :ex-

change 3 being pro-assigned by having an operator circuitas'sociated.withthem. In 'tl'ie 1 case-of incoming junctions theassociationot circuit are-not called into' use on incoming junction calls, a separat'epath of encryptin I employed. The operatorcircuit performs the watching function previously referred to.

In an area comprising aparent exchange.

andzsatellite exchanges the operator circuits at these exchanges would exercise a discrimination between local .and junction calls; "The connecting circuit at the satellitej excliarige may have two selectors connected-to ltyone giving 7 access to local subscribers and one to junctions to the-parentexchange,"both of which are taken into use and a'junction to the parent exchange is seized when a-call {is originated. ,The operator circuitmaybear ranged then toreleasethe selector thatis not i V required. The operator-circuit records at least suflicient digits to" determine the nature of'thefcall and may inzthe caseofail-ocal call cause the absorption of. digits not required'in settingup the local connection." Al

ternatively, the selector giving" acoess'to the locall ines may absorb any unnecessary digi s.

In a modification the ,operator circuit when taken intouse .mayca'usethe selecting of the conn ectingcircuit toselect a free unc- .tion to the :parent exchange and take into of the junction. Impulses would then be received in the operatorcircuit at th ater lite exchange :and also'at the parentexchange and theoperator circuit will-cease to record :impulses as soon as it is :determlned thatgit is ajunctiOn'calI. If the call is det'ermined to be one for i a 'localsubscriber the. operator -ci'rcuit will release-the selecting.iswitch, and

i the junction and allow the selector to be reset by the remaining'dialled digits.

exchange and then a dialling signal may be given. The digits would be recorded in boththesub-satellite and parent satellite ex changes in the operator 'circuits'which may cease to exercise co'ntrolas soon as it is determined that the callis for the main exchange. If the callis for the parent satellite exchange the junction to the main ex-,

change vvouIdbeLr'eIeasedQ {The operator circuit comprises apparatus for performing functions usually, performed bya connector thereby simplifying the connecting circuits In general the operator circuit connects itself-to a free. connecting 3lI- cult, a number ,Of,-11'lt6I'COIlI1eCt1OI1S between 1 the two circuitsbeing provided over which the operatorfunctions are exercised. The

operator circuit contains digit switches or like devices for recording digits and may be provided with Ineans for-repeating them over the connectingcircuit, the'setting of the digit switches determining what functions are to. b xerc se -w Y 7 The functions, which may be performed by an operator circuit besides therecording of f digits include thetesting of selector'outlets, 1 search over the lines 'ofa P. B. X. group, the

application of ringing current when required,

. the selection and connection of an appropriate ringingI circuit in thecase of party line 7 calls, meteringor suppression of metering and connection of, tone slgnals. It may also for connecting an'ln'coming line with an out- J deal with permanent loop conditions andeffect'the disconnection or a line from the exchangeapparatusand the freeing of the ex- V finder magnets being designated YM, RM

ch ange apparatus Lunder such conditions.

i As'regardsthe connecting circuit this may be of any known typeand provides. means going line and simulates a'cord circuitin a manual system. Thetype of circuitconten1- plated isone having a selecting switch for the selection of, anoutgoing line and in which ais' regards incoming lines the connecting circuit is available in common to a number of subscribers lines over a searching switch such [as a call finder. In, the case of incoming junctions a direct connec'tion to a connecting circuit maybe employed. videdwitha feeding bridge and means for 1 receiving and repeating' impulses and supervi'so 'ryi signals. Y w

f For'the bette'r'understanding of-the inventionreference will'nowbe had to the accompanying drawings which show, hyway. of example, one method of carrying out the invention. the exam'ple taken aruralarea has been assumed comprising a main ex-.

The circuit is pro change of the al type emt loyih serially. related o-motion;se'ilecting switches with' junctions to parent exchanges whichin turn mayhave sub-satellite exchanges connected to them by means of junctions. 'Each sub A'four-figure numbering scheme is employed,

satellite gisdirectly connected only toits pa rent. The circuits shown. aregsui'table for use at either a parent or a sub-satellite ex change, each exchange serving up to lines; 7

the thousands-"digit denoting a particular exchange, andif it is a parent exchange, the digitis also used for its sub-satellites if it has any. As regardscthe parent and. subsatellite exchanges, discrimination between? callstobe completed at a parentor atone of its sub-satellites, takes place according to the hundreds digit.;- Calls from one satelf lite area, that'is, anarea comprising a parent exchange'and its sub satellites to another, are

saj

completedvia the main exchange and oneway junction workingis employed;

In the drawings, Figure 1 shows a sub- U 'scribers line circuit, Figure 2 a connecting 90 ing at a parentexchange from asub -satellite exchange. Figures 3 and-3a showan opera} tor circuit. Figure e 'shows the outgoing end of a junction from, the main exchange to a f parent exchange or y from, a" parent exchange to ya sub-satellite, and Figure 5 a connecting circuit for subscribers lines and lines'incom= circuit terminating the incoming end oflsuch a junction. I The line circuit, Figure l,com

prises EL'COHIblIlBd line and cut-off rela'ycL and the subscribers meter SM and is connected to bank contacts in two=motion..call finders associated with. connecting circuits.

The connecting circuit vfor use onlocal calls -or calls froma sub-satellite exchange and shown in Figure 2 has a two motion callfinder CFManda two-motion connector .CS 1

with magnets for their operation, the call and'ZM and the connector magnets fVMl,

'RMl and ZMI for. the vertical, rotaryfand release magnets respectively. Theconnector has also ahbank of vertical contacts VG,

bridged by a wiper'whi ch partakes onlyin the vertical'inotion ofthe :switch for the control of relay JT and the release of the connector,when required, at th'e end of discriminating digits." The circuitii s provided withfa feeding bridge havingjan --in1pulse relay'AA connected tothe incoming sid'eand ananswerlng supervisory relay YY connect-- the call finder TC and switchingrelays.

I The operator circuit contains apparatus for performing functions usually. performed by the connector,such as testing an outgoing 1ine,'the relay forwhich is designated 11?,

the application and tripping of. ringingicurjrent,,thesring tripping relay, being: designated .TR and; other functions which will ii -sewers be apparent from :the detailed description that follows. Inithe coperat-or circuitiis a .:finder;switch which, when an operator circuit'ais :taken into use, searches for and f'connects it' to a free connecting? circuit; illhis I "switch "has seven wipers and ba-nks :designated A1 to A'Zsand 21SSOClflt'8(1"Wltl1(li3 '18] -asimilarswitch with banks and :wipersdesignated Bl to B7 which is steppedto the position, assumed by atheaformer switch to provide interconnections between rthesoperator circuit and the connecting circuit.

Switch LS-hunts for theplevelain which the sequence switch SS which also controls cir-l cuits for other purposes. The sequence switch has ieightywipers and corresponding banks of contacts. For the sake 10f. convenience, however, wipers 2,14, 5 and 6 are shown dissociated as contacts and are designated "by a fflZLCtlOI], thenumerator indicating the back contact and the denominator the wiper; :the wiper side of'the contact is shown as a solid black rectangle, the contact side as'an open'rectangle. " Wipers 1, 8, 7 and "8are shown'in the conventional manner. Stepzping switches BC and RD are'provided for;

theselection :of a partylin-e ringing code and the intermittent connection of-ringing current overthe connecting circuit to a called local party line. V I i I .A separate entry denoted-by the wires E8, E10, E12, E14, E16, E18, E20 and E22 connects the operator circuit over 'a searching switch to a connecting-circuit terminating an incoming junction from the main or parent exchanges. This connecting circuit shown in Figure 5v is of a similar nature to that shown in FigureQ, but is connected directly to an incoming junction instead of .being'available to a number of junctions. It isxprovided with a feeding bridge and has ,a connector for selecting an outgoing line, the connector having ELVBIillCZLl bank of contacts correspondingto the-bank VG Vin-Fig; ure2. A selecting switch-1C3 connects the circuit to a freeoperator circuit over the wires ES-EQQ and it is arranged that-a junction can only be taken into use-at the distant exchange when it has an operator circuit connected with it. @nly onejunction is pie-assigned at a time and when it is taken into use,'the searching switches of otlier.;connectlng clrcuits search for operator circuits I and when an opera'tor acircuitris nconnected 1 t0RCOIlIlGCtIIlgfilTCIilt, thef unct onztermilnated by the connecting L circuit is assigned for use. .Thus :itiis always assured "thatwa Ijunction taken into use Eon: calls in a direc- :tion from the main lexchange'to' a sub-satellite exchange has an operator circuit con .nectedto ,itsincomi'ng endto receiveimpuljses and to exercise the necessary; control.

For the purpose of the following descrip tion it will be assumed {that the circuits. shown are situatedat, a parent. exchangeafter which consideration will be given 'to the operations which takes place when the circuits are assuinedt be atafsub' -satellite exchanges.

FFOII. the assignment ofa free operatorcircuit ,todeal with a call, an assigneriis em.- ployed. The assigner comprises a one;motion switch with driving, magnet and con trolling relays. A start relay common to -'a j group 0t lines is provided-which when op erated starts the switch searching for a tree operator-circuit. 'VVhen allnejrelay 1s;op-'.

erated, a marking potential is applied to a wire common to' all the lines :inthe level in WhICll the calling 1111618 connected, ithe several marking wires beinggconnected sin 7 multiple. to a switch in all the operatoric rfg cuitsaccessible to aniassignerh for use wit-h the present-invention isis'hown and described in British.Pat-ent332,9O4L- 1 When a local subscriberoriginates acall,

the line relay Lin the line circuit operates and starts an assigner searching for aft-rec An assigner ofthe kind which' is suitable operator circuit. The :connecting :'circuit.

finder in the assigned operator circuit then searches for afree connecting circuit of the kind shown-in Figure Q a-ndlwhen Ifound search for the marked level is made by switch LS. --Si1nultaneously with the search :Eor the marked level, the call finder 1 GF'is stepped untilthe marked levelxbeing reached search overtheilevel ior'the calling line takes place tor circuit where dialledrimpulses are ire-1 ceived by relay A. When the linehas ,been

found, an inr'ipulsev isautomaticall trans: "Initted from the-operator: circuit'to theiconnector "to" step it to level 1 over which alt I fii io V and when found it is extendedto the oiperasearches automaticallyfona 'freejunction 7 to the main eXchangewhence-a dialling signalv is transmitted. Theifirst or thousands digit is. repeated by relay. A to digit switch DSA and overthe-connectorto the main exchange. If'the cal lissnot be-complet-ed over the'main exchange, :but is for a locatsubscriber or a subscriber on a sub-satellite exchange, across.

use

connection to theiba'nk contactof switch -DSA releases the-test relay Pr andefli'ects'the" operation :ofthe connector; release magnet.-

swiah DSA'homesrs Thesecond'digit is-r eceived by switch BSA and steps the connector in accordance swltli the. f numheraof im,

ris

I pulses received: This digit then determines 7 whether the call is to *be completed locally or at a sub-satelliteexchange. If the call is a. local one,-the-.connectoris released. The

.tens digit. steps the connector-to the level in which thesubscribers: line is connected A and switch DSA is also stepped, and the units digit rotates the -connector over .the level to the-contacts connected to. the wantedline and at the same time switch DSB is stepped to determine whether the line isan ordinary or party lineor a line in a B. X; 7 group.

. changeand at the same time'are recorded on 'switchesDSA and. DSB at'the parent ex change. When the called subscribers li'neis found, ringing current is appliedbythe operator circuits-of the exchange-to, which the called line is connected andon his reply,' the I call ismete'red by theoperator circuit of the this junction only is marked free at its outgoing end. On a call fromthe main exchange, the] first digit is taken up in selecting a junction to the required parent ex originating exchange, the parent exchange in" our example.

If the thousands thereator for one on another parent or a sub satellite thereof, the connector is not released and7'the'rema1ning dlgits are repeated over the junction to the main exchange,the digits being'recorded-on switches DSA -and DSB v at the parent {exchanges as before.

I Inforde'r that an operator circuitmay be in "40 7 coming from the main exchange an incoming junction is terminated by a'connectlng ClI'CLllt' readiness to receive "impulses on calls inof the kind shown in Figurefi and one such junction has an operator circuit always connected to it as far as may be possible,rand

change. The second digit is recor-dedinthe operator circuit] atthe'selected parent exchange and is recorded onswitch- DSA and also} steps the connectorL'i This digit being thatlwhich' discriminates between calls to be completed at the parent e'xchange an'd .calls to be completedata sub-satellite, further op eration depends on the digit received. In the .former case, the connector is released 'and'is l e-stepped L I being recorded on switches DSA and-'DSB as before and the line if found free, is rung" from the operator circuit- The operator cirto s'elect the wanted line, thedigits cuit beingtaken into use over wires E8'E22,

no; metering is eflected by this circuit, this being done. at the originating exchange. In

p digit determines that i the call isto be completedover switches at the main exchange, either for a subscrlber stopped.

the latter case the connector is stepped by the hundreds digit toi a level containing junctions'to the sub-satellite and afree junction is seized. .The operator circuitat the parentexchange .is'. released, further impulses being repeated directly over the connecting circuit to theasub-satellite exchange.

As regards a sub-satellite exchange the cir-P cuit operation-is similar, the parent exchange taking the place of the main exchangeasfar as the :sub-satellite-is concerned. On calls incoming from the parent exchange only, two s digitswill be received at the sub-satellite exchange, suitable strappings'on the sequence so for the purposelof effectingthe requiredopis switch in the operator circuit beingprovided erations.

An outline of the operation of the system 'having been given consideration .will now be given to the more detailed circuitoperations. A call originated by a subscriberto the parent exchange willrfirst be considered[ When the subscriber lifts his receiver,-relay L operates. overits winding (1),: the calling loop, and battery'overcontact Z3. Dueto-the .energization of winding (I) alone, contacts Z1 and Z2 only are operated," Contact Z1 closes acircuit-for starting the assigner not shown) in search of a free: operator circuit and contact Z2 connects battery over winding of 'relayLto the test wire in the. call finder 1 multiple. When a free operator circuit denoted by battery I over wiper LS3 is found,

relay S therein operates and the assigner is Relay S on operation I the testing circuit of relayjT. If the concloses. at contact 32 f necting circuit finder i-ncontact'with a free,

connecting circuit,'relay T operates. If the connecting circuit is busy, the circuit over wiper A3 will eitherbeiopen or the wiper will be at substantially earth potential. Relay GMA thereupon operates overback contact tland then toeartheither over winding (II) of relay Tjand contact 82 or over wind-.

ing (I)-ofrelay T'to the busy earth on wiper A3. Contact gmal closes thecircuit of mag net DFA and the magnet interacts with relay necting circuit is found, the circuit of relay GMA. being opened when magnet DFA op: crates, by contact dial. Relay T operatesv GMA to stepwipers A1'A7 until a free con over wiper A3 and vertical ofi-normal co'ntact 0H2 of the call'finder of a freelconnecting. 1

circuit, vertical off-normal contact n03 of the connector of the connectingiclrcuit relay TT to battery and cuts the circuit of relay GMLAat contact t1 stopping further stepping. Relayv TT operates in series with contact 25251. Contact t1 short circuits'wind ing (II) of relay andconnects earth over contacts is and low'resistance winding I to wiper A3 to mark the connecting circuit en- BO gaged in thebanks of other connecting'cirwinding (1) of relay T and locks uppover se ene-113 cuit finders onthe; same multiple" Gontao't'i t2 closes a: circuit "for 'relayi GMB? in series with relay; TA and; relay GMBc-operating; closes the circuit otmagnetDFB-l The mag;- net and'relay- GMB 'Finteract withone another to stepiwipers B14437 untilithiey; occupy similar position with respectyto the banks-- to wipers A-I-A'? denoted by a? battery connection oven wiper; A1, whereupon relay. GMB 1 is shunted and a 1 low" resistance path provided for relay 'TA which operatesandnat contact: tal opens the'circuit'ofrelay GMB;

thereby preventing further stepping f the 16 switch. .The Wipers Ali-A7 and BI -B7 and-they are both in contact:.with leads to theisame connecting circuit -Contacts ta and tatconnect-retard coil RC andiimpulse relayrA respectively to wipers'Aand A and contact m5 relay Q;

Contact 9614 closes a circuit over contactyll for"slow -releasing relay X which operates:

and at contact 001 operatesirelay Y.

ofirela yX at contact 1/1 and another 'cy'cleof operations is then gonethroughby these two relays. Each time relay Y 'operates, contacts 'of this relay {closeand deliver a pulse I to'whichever magnet circuit of the call finder is prepared at the time, relay Y remaining operated long enough for satisfactory mag-- netoperation, due to theislow releasing-propeerty of relay X5} Contact gcZ8- prepares a circuiti'for magnet? LS- which circuit isclosed by contact 1/ at. each operation of relay Y, the :circuit being from earth overscontacts 3 5023; gd3, t l, magnee-12s to battery. Simultaneously with this closure a circuit is closed as) follows earth over "contact 3 lowresista-nce series winding (11) of relay GD, baCkcontactWaQ, iront-:con-,. tact gall, contact t3, wiper A6, contact 'nrlof' 5o {the call seeker, vertical magnetjVMi to: tery. Atjeach operation of re1ay:Y, circuits for operating magnets LS VM'La-reclosed andthe two magnets step their; respective; s v I} By theclosure'ofE contactio5 relayiqDS'op crates 1 in a circuiti including ,armature g'conet tact 3' of sequence switch magnet SS; iw-ipieri SS7 and normal contact. Contact dsIop-E switches synchronously;

f Relay-T T. on operation prepared' the circuit of'the call-finder test relay TGfat c0115 tact 2562 and the holding-circuit of the same relay at. contact #3 and opened. alpoint: in the'call finder release magnetcircuit; and at contact #4 opened a p'oint inthe cone; nector release magnet. circuit and closed "at circuit-for. relay JT over normal contacts of bankzVO and icontacttcl. RelayJT- oper-Q ates and .locksiup aover contact y'tl.

VVllGll wipert'LS2-nis stepped on to th t now-occupy similar positions-sin their banksrelay:- GD operates by means of its windingf (I) over normal contact and: :wiper; LS4 and and "M3 Contact 9612 operates tact marked" over contacts-Z5; and: ll ofthe linei relay and the start wire 'commontmthe subgroup of lines,rrelay M which is cone s nected to wiper LS2 by contact s11 operates- V 5 and locksup over contactsmlafand 9654..

magnet Lsyisopened at contact 713 and at:

.The" circuitE'of magnettVM is openedat con j tactimQrand the call; finderisgbrought torest with; its wipersioppositethe level inqwhichr the calling line isconnected. The circuit of:

front contact: me a circuit prepared foifthe? rotary'magnetRMofthecall lfinder; When i thecall'finderniade itsfirstgvertical-step, con" l tact 0721 closed" a point, in the; circuit? of; re-

lease magnet ZMLand contact-0M vopened the" testing circuitofrelay T; Theanextdmpulsef transmitted by relay I Yptakes effect -,o n the" magnet RM, the circuitbeinggearth ovencontact 1 winding "('11) or relay; GD; front-com tact m2, 'wiper- A7 and bank" contact;- con;

tacts n01, Z05, magnet RMtobatteryand this I and subsequent impulsesrotate the wipers or the call finder; round the level until the;;callingline isz found. Thisline is.indicatediby I the connectionof batteryover winding; .(Il-) of relay L and "contact-Z2.- tothe contact the test bank ofthe callfinde-r andwlren'w-ipe-r: I i Q C reaches this Contact, a circuit is closed't'here oven for; winding ofrelay TG' whifch op crates and atcontact; tcli closes a*holding;c;ir-;

cuit for: itselfby means of:its; inding-(l1) Contact tci connects earth: to. the test; wiper!" C tomark the line engaged and winding I Ofmelay: L no.W;being; fullyenergijzed contact s"Z3,rZ4: and were operated,- the tw'oiormer disconnecting g relay L' from th'e line and the signen, Contact $0.5 opens the'cir cuitIofmagnet RM and contacts 2202 t and $03 connect the? calling line over wipers' A and B of thejcall-k finder andwip'ersA ta-ndA5 ofthe'connect' ing' circuits finder; to retard coil RC; andz-ima pulseqrelayaA in the: operator circuit!" Con-i tact-T1506" opens a point-in; the circuit of the;

release-magnet ZM to guard against -subse,-

qu'ent-releaseof-relayTTQ RelayA-i inothe; operator circuit operates at contact: a2 f operates relay V.

erates magnet Ssu releasin'gnrelay DSa 6911", I

tact (Z81 opensand magnet SSreleasesstejpping theswitchl toits firstcontacts "Relay DSs is now: connected; over; wiper: SS8, .fi-rst bank contact,iront contactj a3, Winding V .of' relay to'earttlr. The resistancet of thiscircuit: does not permit? relay} DS to operate 7 i b t el x;D- n 'rati gnrepares ci cuit relay DSat contactldl and atcontac t 2Z2 con- V nects earth' over contact gdivtjorel'easethe assigner which in turn releases relay On .the releaseof relay GrD the circuit. of "relay Q is opened. Before the armature of this I'QlrllYfWhlClliS slow to release cfalls-lba cln a circuit is completed from" earth over Icon-1: .tact ofthe s'equenceswitch, contacts g1, gall,

battery. I q A '3 Theconnector'is stepped toits first level,

I 'themagnetcircuitibeing opened onthe sub-" V sequent release of relay IQJ The vertical oil- 1 5 normalcontacts 720 1,n02and1 n03 are op 63, wiper: A6,- contact m l of the'vcall finder, Vertical {magnet VMl .ot the, connector "to *erated an'datcircuit isclosed for; the rotary magnet RMl over contact 1101, wiper A7,

contacts 123,0Zr1, y, and the magnet stepsthe "wipers round the level iii-search of a free unctionto"-the ma1n exchange, the stepping being effected by the interrupter relay Y. He-

- lay DR is operated overthenormal bank con-f ,tact and iper DSAG of digit switch DSA and contact i 91 when relay Q releases and at contact drt, operates relay G. Relay DR;

holds' over contacts commoned in the ban-lr of i wiper DSAG corresponding .to2lines in the junction" group except 'the last line.

Contact (Zr?) maintains 'theicyclic 1opera-c --tions of relays X-and Y-on the release of relay GD and contact'clr2closes a circuit including wiper SS 3 in'rpo sition lover which'magnet P DSAsteps; A free junction is denotedbybattery poten "tial on the test bank contact in the connector and when such a contact is encountered, relayj P operatesovers'equence switch contacts g g2, winding; (I) of relay P, wiper B7, relay PP, thetest 'wipera'nd bank contact to bat Q' tery. 1

Relay'P-loclrsjup its winding II) con cuit for switch DSAo'ver contact -1 and wiper contact dr the interrupter'relays X'and Y.

- A signal is now 'sent' forward frombattery overcont'acts; M5, c1, wiper SS1 and con-g tactjl, contact p413, wiper-B4,'contact- 03 3 in f the connecting circuit, the b wire of the juncgij tion to th'e main exchange to take into use selecting apparatus thereat.

Di'allingsignal is' 'now connected the: -main exchangefand'is transmitted over the junction, a wire,'contacts rig 2, wiper'B3, con

tacts 1M2, p258, condenser, wip erAl, the call 'finjderto thesubscribersline. c x The calling subscriber now comn'iences to dial the number ofztlie wanted'subscribenthe race-21s" impulses being received by Al; the

commencement of thej'fir'st impulse, contact a3 fallsback and completes {a circuit over i i wiper SS8 ofthe sequence switch for relay DS; which causes the magnet SS to step the switch,

to its second position. Inthis position the circuit of relay DS:is open at contact all, relay Dc holding duringimpulsing by means ofits 1 second winding in a circuit from earth over; contacts 12,424, windingtll) ofrelayfD, congftactidr2, wiper.SS8 in position 2, magnet ,DSA to battery. impulses are repeated )to 'magnetrDSA over this circuit. At the same timethe impulses are repeated atcontact n ma circuit overwiper SS1 in position2, contact pat, wiper B4 and the junction 6 wire,

to'the' switch connected to the incoming end of lthe junctionto the maineXchange- ,At the end ofr'the impulse train relay A remains; H steadily operated and relay Dxreleases closing a circuit over contact all and wiper SS8 for" steppingYthe sequence switch to position-,3-

ing (I).

Inthe'bank of D Sla5lthe contact cor-T whereuponrelay re-operates' over its wind- 7 responding'tothefthousandslldigit of the holding circuit: of relay ..Pand the further operation of, the circuits now depends on whether'thecallis to ,be completed within" parent exchange and its'sub-satellites is cross- 7 5 connected to a common w re connected to the thesatellite area or-yia them-ain' exchange,

change. The contactto which wiper DSA5 is stepped by the thousands? digit is ac- It will be assumed firstfof all that the call i is for a subscriberconnected to the parentexrf V cordinglyfconnected to the holding circuit of relay. P and when the" sequencefswitch is stepped to its third positiom'a short circuit;-

across relay P, winding (II)fis closedover contacts 3;, p6, and wiper DSA5;v Relay 1P releases and releases relay .PT. {At contact .pt7 earth is 'connectedover contacts a} and t5, wiper B5, -'contacts 11in the, vertica'l'bank,

VC to the battery connected side ofrelayiJT also in paralleltherewith .to contact 7'65, Re

lay JT' releasesand the release magnet-is op tact 2m to ensure complete release ofr thejcona 'erated over Contact j t5'and theaboyetraced Q 7 y f circuit, its'circuitbemg maintalned b-y-con c nectorx "I heeOnnectQr andthe junction to the main exchangeare released, A cir 7 uit for switch *DSA-is closed over contactsfi andptlO. I

*The hundreds? digit is as re ceived b y relay A and at the commencement of the first,

impulse, the, sequence switch is steppedto its 7 r A willjreceive two impulses which willxbe repeated atcontact (12 to magnet DSA which: i i will step its .wipers to theirsecond'contactsQa -At the same time impulses will beirep eate d at" contact al inthe following; "circuit earth over contacts 01, 322,914, d1,-wiper S S1 posifourth position; The .hundredsidigit for] calls to be completed locally isi2 vand relay 50: r for. relay PA overcontacts a, andptll and tion-l, contacts pt3, gall, t3, wiper. Ail,rotary;

off-normal contact-7W1 ofthe call'finder; magnet. VMl to battery and the connector-is stepped toits second level. At the end of? i theimpulse train, the'sequence-switch steps;

to its fifth position inwhich a circuitis cont pleted over contacts s it, t5f'and wiper for release magnet ZMl and the connector;

is released. The digit switch DSA remains with its wipers on itssecond contacts. The tens dlgit is repeated to magnets DSA and VMl in a similar. manner to the hundreds digit, the sequence switch movingto position Gat'the commencement of the first impulse and to position 7 at the end of the train ofimpulses representing the digit. \Vith the stepping from normal of the connector,' the vertical off-normal contacts are 013- erated= and a circuit is prepared over wiper SSl in position 7 ,contacts gate, drl', o3',w-1per A7, connector vertical ofi-normal contact n'ol for. the connector rotary magnet RML; acircuitisalso prepared over wiper- SS3 for mag-- neti DSB J The units digit is repeated to these twovmagnets and the connectorwipers-tare stepped round to the contacts. of

the wanted subscribers line, digit switch DSBI being steppedat the same time. I-f the line is anordinary line, no connection exists over the wipers ofthe-digit switches andthe line istested by relay- P. When thesequence switch moved to position 8 during the re ceipt ofthe first impulse, a circuit for relay. G;

wasclosed atcontact to provide a fleeting t est. During the'slow' release ofrelay G con: sequent on the stepping of thesequen'ce switch-to position 9 at the end:of thedifgit,

earth is connectedover contacts g2, winding of relay P5 wiper B7, relay PB,- the. connector test. wiper and test bank contact.

Ifthe line is free battery potential isfound on the contact and relay P operates and'loclts 7 up over its winding (11) contact p1, con-,

nectingearth to :wiper B7to mark theline, engaged. .Belay PP which is'of' low resistance operates in this circuit'and at contact p791 removes a short circuit from winch ing (11.) ofrelay V Y. I

On the closure ofcontact 325 a circuit exists this relayoperates and locks up over contact pal. Relay G now releases and a ringing. circuit is closed over the ringing generator and wire HG, contacts 1'3, Z7663; wiper B4,

contact oy3, the called subscribers line and bell contactsoy2, wiper B3, contacts @422, 93,

9 2 and winding fl) ofrelay. TR, and the. called subscriber is rung; At the same-time ringingsignalZis transmitted to the calling line overwire BS, contacts 1E5 pa4t g1, got the sequence switch the condenser and wiper-A4; i I

When; the called, subscriber; answers arelay: TR. operates: round the, loop and; locksup wem a a;

c rcuitand contacttriiiopens a point inwt-he es ng, i cuit o he: assign -L Rel y- IV hereup nr p rates; the at ry o ne tion bee- Contact trzfconneets earth yto wiper "B63; to,

oneraterela vY and:.VA; .;t e connecting f ing o'verretard coihRA and contactjal'to the V a wire.v Qontactawli 0l0ses alocking, circuit: e elay VA. overit's Windi g I%) ndcontaotr i5... 'aaQ piieparesfOr the Oper tion of relay ,5 MR;

the circuitbeingcloscd at contact yg ZoffTelay;

which operates roundthe called loop=onr batter;j con11ection being oven retard. coil" RB:

lillBg ChElgllQQ QVQI of contacts wy'2 a nd -ry3z; ,thea l ,93 l Relay MB operates and connects itself: over contact; mr'l, ofhnormalg bank; contacts], and; wi'perqLSl. contacts m5 and 25013 toaearth and at contact WW2 connects batteryrover wiper A2; and the meteringwiper D of-the call, finder to operate the subscribers. meter! SNL.

. Contact 77?)?"3i opens thecircuit oftrelay- V which onrelease initiates the release ofithe operator circuit whichitakes'lplaceas follows contact 211 falling back .disconnectsthesgenerala holding earth and relays 'T. andQTA release in succession, RelayTT in theconnectorsalso,

releases and releases" relay TC which; at; COIl': tacts $02 andytc3 disconnects relayz'A from the:

. calling line." Relay, A releasesl' Relay TR;

is;released at, contactfol-and relay;P at-;.con;-

tact 418. Contact p5, openingrelease's relay PA and contact as relay. D. Atcontactrikvhi ahoming circuit for the sequence switch over; contact M5 and the commonedi contacts in the hankofwiper SS7 isclosed; relay DS and:

magnet-SS interacting to step: the sequence switch to its normal position'where a 'circuit 7 moned contacts, self-interrupting 'contact'ls, contacts 1%, 'magnet to battery; "Switch" LS homes and the assigner testing circuitgis l prepared overcontacts o9 'andtr3r-Relay MR; releases;

homing circuit is closed over 'wiper' 'DSA-l Atrthe'back of. contact al a ub andcontact (Zea for the digit SWlt ChiD SAE j and when that switch-[reaches its normal fposi' tion, al homing circuit forswitch D313 is closed over -Wiper DSB1 and'fc'ontact d865,.

The operator circuit is now at: normal and ready for further use.

In the connecting circuit contactoalfconcontact oylconnectsthe holding and'engag- WA and 5 13 Points in the circuits of f the release magnets ZM'andZM l "respectively? Relay VY locks up over contacts jt2 and g g/ l."

fat the end of theconversationfiwhen the" calling subscriber clears, relay: releases;

releasing relay 'VA; which at contact-141a di'sconnects the; earthconnection from thecall 70 connects the calling line; to relayAAr which' w ieslii nd 31 5 H finder-' 'test wiper.- Contact 004: closesa 'c'ir- V cuitfor'the 'call finder release magnet ZM'oyer' contacts o'inl, t06 and H3, andthe'call finder isgreleased, the magnet circuitbeing opened at contact m1 When-the switch'reaches' its normal position. Relay YY releases when the called subscriberfclearsand at contact I ygjl'releases relay WWVlllCl'l at Contact m l disconnects earthifrom relay PP and thecon- 'nec tor test "wiper andat contact/W5 closes a circuitforfniagnet ZMlover contact h02and tte; Theconnector is released, the magnet r circuitbeingogened Whenthe swltchyreaches normalat contact n02; The-connecting cir- I cuit-is again free for further use. Should circuit 'is closed over contacts mp5 andrvyti one of the subscribers failto clear, an alarm and Wire PLQ VVhen contacts cal and a :"If the called line i whenc tested with the 3; sequence switch inposition 9' is found busy;

relay Pr does not operate and on-the release ofrelay G which takes'plac'e after a brief interval, a busy signal is transmitted over wlre BS, contacts n5,=pa4c', g1,%and;w1per A4 and the calling subscriber clears. Relay Athereupon releases and opens the circuit of relay VWllltlll on;release-initiatestherelease of the operatorand connecting circuits and'theline relay L;

v If the hundreds connection is tobe completed at sub-satellite exchange, the hundreds? digit of which is 8,' relay J T isoperate'dat the end of the digit impulses and'searchfor a' free and available junction in levelrS'is made bythe connector. When the sequence switch moves into position {5, a circuit: is closedover Wiper DSAZa' andi its eighth bank contact for relayjCO which locks up :over contact 001 and Wiper LS4 and at -contact 002 connects earth over contact-2' to WiperDS'At. The eighth contact 'inithebank of-zthis Wiperfland'othercontacts i inithe bankcorresponding to the junction grfou pexcept the lastfin the -group'ar e coin vnuoned tand cross-connected to the common point connected to the relay DR and relay IDR operates. Meanwhile earth 1 over contacts 2,1967, t5, Wiper and contacts 8 ofthe" bank YCjis connected to relay JT and that re-r lay operates and locks up over contacts. 7'61 and tzfl. Contact dr3' closes a' circuit'for starting-"the cyclical operation of the interrupter relays, "contact Zirloperates relay G to prepare the testing?circuit, and Contact vidrl closes acircuit overwip'er A7 for rotary Inagnet RMl to stepthe connector round the i j level-in search ofa'freejnnctionf When a 'free and ayailable junction is found,: relays P. eand' PBopera te andrelay DR "is released andacircuit'is closed at contactpofor relay.

exchange.

W 'uiz l open, "the circuit overthe'second windings of the respectivefline relays L are opened andtheserelays release andc' nnect their line indings'to the lines.

digit denotes that the PT'Which operates and locks The tens o and units? digits are repeated toswitches DSA and D513 respectively and alsoover the junction over contact al, Wiper SS1, contact 'pt or 20%, contact 2M3; wi'per Ba and the out goingbwire; 'At the end 'of the unitsdigit, the subscriber isrung at the satellite When the subscriber answers, battery is connectedto the a Wire and the s gnal 1s re peated overiwiper B3, contactspa2, 1232, 93 andrelay TR. Relay TR operatesand'at contact W2 operates relays VA and VY. Relay Y J T holds over contact 413 4 on'rele ase of the operator circuit. 1 Relay YYroperates over the junction a Wire and if the calloriginater'l i at a sub-satellite eirchange repeats the answer- 1ng supervisory'signal thereto at contact yy Contacts of digit switch'DSB correspon'ding to party line subscribers are common ed and are connected over contact 20613 torelay e 'Rfor the control ,ofswitchfRC which re-e ceives'the additional digit dialled to select a.

particular subscriber on aparty line. '-When a party line subscriber is called, the operation is as previously described up to the reception of the units'digit andthe testing of the line. When the sequence switchsteps to position 9 a circuit is closed over-contact Wiper DSAZ and oneof the Wipers DSB2-8 as determined by the'crossconnections;the"

contactcorresponding to party lines, contact 10613 and relay fR 'Relay R operates'and locks up over contacts rl'and o5, 'and'at con tact r4 connects nagnetRG to contact 9' in the bank ofwiper SS8; Contacts 1112 and 7'3 disconnect the; ordinary ringing circuit and prepare a code ringing circuit. Contact r6;

prepares a circuit for theinterrupter relays.

pulses by contactal. Switch RC is stepped quired ringingcode as determinedby the connection of the contacts in thejbanks of 'Wipers RC2 and R03. VVhe'n' switch RC comes to rest at-the" end of the digit, the seby the received impulses to select the rer que nce switch steps to 'position'll, whereupon a circuit is closed overcontacts ,,"r6and 51' for relay X. Relays X, Y,'and Z interact to o .produce intermittentoperation and relay Y r v acts as an interrupter for stepping s'v'vitchRD over contact pa5,1 'con'iino-ned contacts" and 7 'g' Wiper RC4 and magnet RD, 7 V 1 Contactsv in the banks of wipers Ens-61 are COHIDIOIlCl and connected to' relay RRin suchaway that relay RR is operated'in accordance with the ringing code it is requiredto transmit. Contactsjin thellatter part of these banks are likewise commoned and 1 g- 4 wiper RC1.

nected to relay RT for the" determination of the end or" a ringing cycle. "The contactin each bank prior to these, is connected to Wiper RG2 to distinguish between the codes transmitted over the pair of contacts connected togetherinthebanlrofwiper Then the wiper or switch RD which is earthed over wiper RG3. steps on we. contact connected to relay EB, the relay operates andat contact rrl connects a continuous ringing generator orer wirc RG and contact T3 to the line, the return being over contacts T2 and T62. By this means a code ring is applied to the called line. When the latter part of the bank isreached by wipers BBQ-43. relay RTis operated to provide a circuit tor relay TR over contact-s r62 and r2, the called line contacts 7e, W1 and r251. A: ringing signal corresponding to the code is transmitted to'the calling subscriber ov'er wire CBS, contacts W2, pa l, 91 1 and wiper A l r When the subscriber replies to the/call, re

lay TR operates at the end of a ringing cycle and locks up and operates relays VY and VA in the connecting circuitto switch the connection through Relays AA. and YY operating close a circuit for relay lMR'and the call is metered and relay V released. The

-'-, release of the operator circuit then follows.

On the release of relay Vt-he circuit ofrelay R is opened at contact. 125 and the relay releases and by the talli g baclrof contact 14 closes a homing circuit for magnetR-C over .When switch RC reaches itsv hoine position a homing circnitis closedtor magnet RD over wipers RC4 and RDl. Con-v tact r6 releases the interrupter relays.

7 When one party. on a party line wishes to call another party on the same line, he removes his receiver, dials aspecial number comprising two digits and then calls the wanted party by meansof a hand generator. The first digit of the special number is that denoting a call to be completed without the use of a unction tothe main exchange. The digit is received on switch DSA. and at the main exchange, and the connector and digit switch are released at-the end of the digit. The second digit steps the connector and switchDSAend is such that at the endof the digit when the sequence switch moves into position 5, a circuit is closed'over con 1 tacts 008, wiper DSAS and relay. RL.

RelayRL operates and connects battery over a=-high resistance and contacts rll,'mr2, m2, wiper A2 and wiper D of the call finder to an earthed relay in auxiliary" apparatus connectedina party line between the main distributing frame and the line circuit. Thisrelay which looks up depending on a receiver being off atan instrument. on the party line.- holds relay L in the line circuit by means ot its winding (H) and marl-ts the line engaged in itheconnector multiple and no further as an J19 s gnment otan oper to ir u is inade- Qontact d2 opens the circilithof relay-Y and the leas the perat r and ea t i s circuits follows I The c, Hing llheh pro; 70

ceeds to call; tliei vantedpa'rty by meansof his hand generator. V i I When acallis originated by a subscriberat a sigh-satelliteexchange. unction to the parent erchangeanda junction from the parent mi e to the main exchange is seized as 5 gwore described. g

The line circuits of unctions incoming at a parent exchange from a sub-satellite exchange have a batteryconnection to the metering wire in place of the meter SM. When the junction from the satellite has been found j o by the call finder CF, relayJC operates over its winding (1), contact'srll, and 711142, wiper l T A2, wiper D of the call finder to batterycon-o nectedto the metering wire-in thelinecir cui-t." v Relay JG locks up over its winding ated and releases relay V which in turn brings;

about therelease of relays TT and TC inlthe connecting circuit. When relay TT releases contactttQ connects earth over relay JA and wiper D. of the call finder and this relay operates to the battery connectedto the met'ering wireinthe linecircuit Contactjal changesaover so that supervisory signals-are repeated to the sub-satellite exchange at con *tacts z y'ifi'. a i

- It the call is tothe main exchange, the,

first and jsecond'digits are recorded on switch v BSA in the operator. circuit at the parent ex change as in-the case of alocallyinitiated call. At the end of the second digit, the sequence switche moves into position 5 and relay PT having been operated in position 1 of the sequence switclnia clrcuitis closed over contacts 9966 '02, wiper B6, windings (1-1) of relays VY and VA, relay PP having operated when I the junction to the main exchange was seized.

, The incoming junction -.is now switched through. to the main exchange and on the.

operation of relay AA, earth over contacts jt and c012 and wiper B2 operatesrelay which initiates release of the operatorcircuit.

The remaining impulses are received direct.

on relay AA and are repeated overthejunction to the main GZICl'IfillIgQfit contact da contact I63 being open as relay JT isnot g released on calls to the maln exchange. .Re-

lay VY locks up over its winding (1) and contacts y't2 and aal When the call answered relay YY operates and relay JA a n'sepe a m t release Q ylay??? the answeriiigsupervisory signal is repeated o'vercontacts and y'all to the sub-satellite exchz'inge. The connecting circuit is released when the calling subscriber-clears. At the sub-satellite exchange, the opera- 'tions of the operator and connecting circuits thereat are similar to those described for the parent exchange except that the operator circuit remainsconnected to the connecting circuit on all callsorigin'ated at the sub- "satellite exchange for the purpose of meter ing thecall. The parent exchange takes the pl'aceof the main exchange so far as the subsatellite exchange is concerned.

. When a call is originatedfa unction to the 1 parent exchange and a junction from the parent to the main exchange are seized and it the call is not to be completed over the. s latter junctionythelatter junction is dropped on completion of the first dialled digit. v The second digit then determines whether the call is to be completed'via the parent exchange or i within the sub-satellite itself and in the former case, the operations'are the same as those described for the'p'arent exchange-operator circuit on calls to the niainexchange. In the latter case the digit being assumed to be 8 when the se uence switch ste s to )osition 5 a circuit is closed over wip'erfDSA3 and its V eighth bank contact for relay G0 which looks up over .contact'col and wiper LS4, and at contact c02 con'nect-s earth over contact t0. wiper DSA JE. The eighth contact in the'bank of this wiper is cross-connected to the common point connected to the holding circuit ofrelay Pand relays P and PT are released. Contact 79227 falling-back connects earth over change.

party line, the codc'selecting digit is dealt with in the same manner as described for calls at the parent exchange, When the called subscriber answers, the call is metered and the operator circuit is released. 'The release 01" the connection is the same as that previously described} i The operation of the various circuits when a call is made in a direction from the main exchange to a sub-satellite exchange, will now be considered. Junctions for calls in i this direction. are provided wit-n ne arrange-' '7 ment's shown'in Figure 4m; their outgoing ends, andat their incoming ends they ter-' "minate innonnecting circuits of the kind shown in Figure 5.

These connecting circuits have associated with them searching switches such asICS which search for and connect with a tree operator circuit. 'The arrangement shown issuch that only one connecting circuit has a free operat r G lsubscriber being detached from a tree at contact 661 cuit allotted to it for. immediate use and only when an operator circuitisthus allotted is the unction terminated by theconnectlng circuit marked free toruse at its outgoing end It will, of-coursey-be realized that other arrangements may be provided whereby any.

other number of junctions may have opera or circuits connected to their incoming ends or all the incoming junctions may have operator'circuits connected to them, an oper-. ator circuit wheiiieqiiired for a call received at the exchange from a local or sub-satellite junction for use on such a call.

The connection of the connecting circuit with an operator circuit is made over wires E8E22, the searching function being per formed by switch :ICS inthe connecting c1r- The finder switches of which the wipersoare designated A17 and B1'7 are cuit.

therefore not used on calls in thedirection, ma n to subsatell1te exchange. 7

For the purpose of description Battery over relay TD and contacts '07, tall and 83 (Figure 3) 'is connected to wire E22 of a free operator circuit and earth is connected by acontact g3) of-a group control relay over contacts @655, and high resist;

ance winding I) ofrelayTB.

. If switch ICS is not standing with its wipers in contact with a free'operator circuit, the bank contact connected to wire E22 will be at substantially earth potential, contact o? being open and a'resistance being connected in series disconnected. 7

.Relay GM therefore operates in a circuit overarmature contact elm of magnet DM of switch ICS5 contact i515 winding of relay TB, contacts 2%5; 64b5, gp to earth; Re-

lay-GM which is othigh resistance operates; but relay TB does not "and at contact gml the circuit ofmagnet DM'is closed. The magnet'operates and by interaction with relay GM the switch is stepped until a free 7 w it will be assumed-that no unct1on is ass gned for use.

with rel-ayTDfor it will beoperator circuit is found- Relay GM is now shunted by the low resistance battery'connefl' tron and relay TB v operates over both its windings and opens thecircuit of relay GM netDM. I m

At the front of contact #21 earth'is connected over low resistance winding (II) of 1 r .reiay 113 to mark the; operator circuit en-. gaged and relay TD therein operates. Cona tact H23; connects battery-over a retard-coil and contact abl to operate the group controlrelaywhich at contact gp disconnects earth over-contactsab5 and i 15 and. windingsfll) of relays TB in other'conn-ecting circuits to prevent jsearchby their searching switches. Contact'tb'? opens a point ina circuit for release magnet ZMA of' theconnector (JCS.

Battery is now connectedover retardcoil'RC stoppingfurther drive by inaganeoma "(Figure 3) contacts Mi, 15614, Wine EQQg ed011- tacts 1512.2 and 1021, lt-he j nnction a 'wire, contaot tn2 and relayTSiat the ioutgoingcend of the junction. {Relay TS operateszand $12 tact tel connects batteryoyer rlay EEN to the test a-bank contact got the ijnnotion {the :bank of theselectingswitCh{selector at main exchange or connector ;at -;p arent exchauge)..., vAt Contact tillfith short cincuitiahoutitiher 2 sistance in the %t.est i n circuit: over Wire Y 13222 is removed in order to sIZQflLlGe the potential ion the test hank Contact of sWitCh'l-GS- When the marked {1' unction is taken into use, relay AB operates andrat contact; (1111 releases thegroup controlrelaysothat eanth is again connected at contact ;g;p 1E0 allowirelays GM in the other connecting circuits o reperete. 1 The searching switches ,step jofi in search.- of free operatoricironitsrand ioneibeling found, a further zjiunctionris manked tree ;and

available :tornse. V '1 a As before the case f the =QpQIflhiOn dfith6 circuits shown .in Figures 3, 311, :and when assumedto loeatE-a parent exchange w ll first beconsidered. Figure 4=then vhosws-ithe outgoing end of a rj unction from the main tothe parent exchange. I

lVhen a call tobecompleted 03161 he parent exchange is made, first digit effects the search at the main zexch-angefrfo-r .-a;.-i 12e junction Ito the parent a free junc-ti ing an operator circuit connected :to its in comingaendifor immediate '11SQ,'bQlI1g= denoted V by battery :potential over relay sand-contact, $81 on the :test hank contact. NV hen the junction is ffound qrelay Till-operates looks up overqcontact m1 and at ,contactitnQ disconnectsc relay TS and connects :the a Wire through to the -operatorcircuit eat the parent exchange. 'Relay at-the parent eXch ange operates over ';the "junction .6 Wire toabattery connection .insthemain exchange. Contact ([61 changing over releases ,theggron-p control relay for the assignment ofanother junction and at its front -contac t connectsvhattery over wire E1-8,-andcontact fftd2fto zr'elay A in:theoperatorcircuit. Belay A' open-ates followed "by relay '=V and the sequence switch steps to position 1. Atthe iparent 9XChange contacts: 3 and A :in ithe banklof zwiper are connected to the rcominoned contaots (number 5 onwards) and "Wiiihifihfi -switch in position .1 relay :DS openates-oyer wiper :SS'? and-contact M5,; and the, switch stepsto posi- :tion 3. Whilst-in position 1 :relayHR sopcrates over Wiper \DSA'G rand :atcontact d033,

operates relay X -to;start the jinteractionZQjf relays X and Y'for interrnptenpurposes, Magnet DSA is :now operated :QJQI WlI-JQI SS3, contact- 01w and .interr ptencontact 1 and when it leaves its normal position, rel-ay DR is released and switch SA ahonies, the circuit being overicontactecl sa, wiper "DSAI, contacts ptlO -and%;

When relay AB operated was have ' ers are 1 rotated sto :th

nloscdntacontact 11? 2 oilersientica-l ofienorinal contact o theoQnnectoriCGS or Winding (515) r t n lay 16 which "ope a e dcentrist-vol prepared t e circuit of e r ztiealnmee et 'lihe hun d vdigit is s ow :dialled by the callingsubscriber ail-d takes effect 1 1 rel yAB- Contact a -e- :pea s th impulses re y A gu e- 3)- and contact 0122 mepeats; th6l1'l,:t0 magnet l\A.- .-During impulsig' y 4G i e d byimeans o fsit-s-iwinding (IL); The connector :is stepped in accordance {with the impulses receit'edandionwitsfirst step the-vertical otia normal contacts mil andmtQ \areoperated. I

Contact a opens preventing -re-operation tact Him/2 kcloses 1a point-{in the circuit of the release magIietrZMA. In-theoperator eirciiiit switch DSA is stepped :vbyithe-intermittent .closureiof-zthe circuit ofwrmagnet {BSA tat con- I of irela-y: :Gjat the (end i of :the digit and :con-

tact-a2. atom end eotthedigiit, th q enc 7 switch moves. to position 5. i a

fli nrtherioperation noyv dependsonthe'excliangeetowh-ichthe\Wantedsnbscriher;is:connect'ecl as represented shy-the digit *just meparent exchange, denoted by the hundreds digit 2, vearth :over contacts 7257,. M387, :WlIG V E8,--rotary ofi' no-rinalz contact m of the coni hector, contact 25in the ivei'ticalbank and contact #1122 is connected to rcle'ase mae 'net andithe connector is released- The 'tens digit impulses are again arepeatedr-to 'inagnets MMAvand 'iDsA-iandftheswitches are stepped es -heiorwtheseqneneeswitclnmovingjto:posi- :ti onfi atcthe end=of:theitnain. Thefirst-impulse of the uni-ts"" ttain .steps :the sequence hitI03pQ$i 1 Qn :8 nnd--the':impu1sesre {Liepeatedrby contact oil over avipenSSl in position;8, :eontacts 1116. 55 (PM, 3, Wi E 6, ntact tee andmaenet BMAandthe co e p-' ontacts otithe wanted ine- :Belay 1G one atesa dat'tlieie d ci es 7 digit-the f-seguence g-sw itch; steps to position 19.

The line is noW tested by relay Pr and ii fonnd 1 iree, ineingi rrent :is iapplied ove Wires sand H314. :BelayKTR ope-rates when the ecalled sfibscniber implies and contacts-Z2 4 connects: earth ozver Contact :pZ-av E 3 0 taetmrzto Wind ng a i-openatesaandzat :c ntac 21 nn cts re locking ci-rjcnit -for-rel-ayZ1over itsWinding rand-:centactsflzai, W1 an -M2 1 JGont'act .veit connectsearth to :;the test Wiper to mark thei-ealledrline engaged and contactgoziiopens ezpoin-t intthe (releas m gnet-circuit agai s the releas e-o ;1?eL y l --i 1iich-isefiecte w of relayVZ. new

layANrtorthe incon i gza(Wire-at n a age-2 andgoz3the-con-nector ipers are: disconnected from the operatorcireuit ;a'ndcon-- nected (t-0' zthe feeding bridge and j-relay operates round the oall-ed'doop and closes a eontaetmed gi 'll;'Q0lltl fitvajfil flay [con i .ne tszitsel d rect y t theoutg ing c Wi ea d V nected to relay'DR and relay DR operates I at "contact ayS connects battery over contact abl and relay AN to the incoming a wire to givera supervisory signal at the main exchange, The release of relay T-B'opens the 7 circuit over wire E18 for relay A-atjcontact H93 and the operator circuit releases. Current is fed to the calling line over relays'AN and AB and to the called line over retard coil .AR and'relay' AY; When the'calling sub'- scriber clears, relay AB releases and contact ab?) prepares thecircuit of relaysyG M and v TB for stepping switch ICS and seizing afree operator circuit. When the called subscriber g clears, relay AY releasesand at contact (Ag 2- releases relay 'VZ which'thereupon opens the connections over the connector wipers and at contactoz5 closes a circuit for release magnet ZM'A. The connector is release'dand the cirrelay TJ. Relay TJ' operates and locks" up cuits are restored to normal;

If the called subscribers line. is engaged ivhen tested, a busy signalis transmittedover wire'E20. r 1 V If the called subscriberis connected to the sub-satellite exchange, the hundreds digit assumed in the example to be8, would have resulted in the operation of relay TJ as fol- At the end of this digit, the sequence switch moves'into positionh and earth is connected I over contacts g, M7, M8, wire E8, contact and contacts '8 in the vertical bank. 'tjl to over contacts tjland 726. -Relay CO oper ates over the eighth contactin; the bank of wiper DSA3, c'ontactsf%and 003, and locks up over contact 001, commoned contacts in the:

bank of wiper LS4 and contact tel? Contact 002 connects earth over contacts ifand wiper DSA& and its eighth bank contact cross-con- 7 and starts the interrupter relays atcontact (Z73. Relay DH is cross-connected to 'all-contactsin thebank of wiper DSA4: corresponding to lines in the'junction group except the last "line; v I f Impulsesv are transmitted-over contacts y,

(a1, '08, and wiper E16, contact 1:54: to the rotary'niagnet .RMA which steps the wipers round thebank in search of a free and:available junction to the sub-satellite exchange.

Relay G is operated at contact di l to prepare the test circuit over wire 'E10so that relay P operates when a free junction is found. and operates'to-relay PT. i r

" Contact p3 releases relay DR to prevent I further steppingby' nagnet RMA; Contact relay VZ operates and locks up over its wind-- 6Qing (II) and contacts @227, t)? andaZQ. Con= 122512 closing connects earth to wire'ES and tact ozh releases relay TB and the feeding bridge is connected to the connector wipers; Battery over retard coil AR, contacts ab?) and 12.23, and the 6 wire eftectoperation of i .relay SAB' in the corresponding circuit at elite exchange.

the sub-satellite exchange and the remaining digits'a-relrepeated tothe sub-satellite exchange over contact @513. -The operator circuit is releasedc'onsequent on the opening of con tact $63. The called subscriber isrung from the operator circuit at" thev sub-satellite ex change and when he replies to the call,the answering supervisory relay in the connecting circuit thereat operates and repeats the signal, operating relay A-Y which in turn connects battery overrelay-AN to repeat the signal to the main exchange.

' The releaseof the connection takes place as fora local call.

At the; sub-satellite exchange, similar arrangements are provided but as the operator circuit has to deal with only two digitson calls fromthe parent exchange, contacts 3' and 4 in the. .bank of wiper SS7 are strapped to contacts -1 and 2 as shown by the dotted line; consequently when the operator circuit 1 is taken into use and relay V operates, the

sequencelswiteh is stepped'to position 1 in the normal'manner and then continues to stepdueto the operation of relay DS over ,wiper SS7" and contact tcZ5 untilposition' 5 is reached. J'Theftens digits is received in the operator and connecting circuits and-f steps the connector vertically, and also steps sw1tchDSA," thc sequence switch moving to position 6' at the 'first impulseand to position 7 at the end of the train. "At the end of the units digitwhich steps switch DS-B. and

magnet 'RMA', the circuitfor the latter being over wiper SS1 and contact-a1, the sequence first line in theP. B; Xfgroup is dialled.

Contacts in the banks of wipers 'DSB2'8 corresponding to lines of a P. 11X; group,

except the last line of a group, are commoned and connected to, relay "DR "to permit of searching by the connector. When thecon nector, either CS or CCS, steps onto the first line of a P. Xi-g roup inaccordance' with the number dialled, the sequence switch steps to position 9and the line istest'ed and if free,

v relayP operates.) If, however, it is busy,

relay P does not'operate but relay DR does overt-he conimoned contacts sinfthe switch 1 DSB, wiper -DSA2jand'contact g and the interrupter relays are started and impulses are transmitted over' contactsjclrl and '03 t0 the connector rotarymagnet," relay G being-held by contactfdr-i to'connect relay P to the test circuit. Search and seizure of a free linet'alres place in'the manner described for ayunction from the parent to a sub-sateratesand locksup ove its windings (likentacts jcl and M3 and at contact y'oifl-conncctsre- Provisioni ismadel for ofier-ing trunk. calls to busy'subscribers by a manual operator at.

the mainl exchange.- Whens parent or sub satellite exchange operator circuit is taken 2 into use over a junction: incoming from the direction ottheniai'n exchange, a circuit-is closedover contacts 2257-, 4110, wwQ and r51 forwinding oi relay JC. Relay JG op lay" N over contact tell, wire; E20, contacts tb2 and uzelito the incominga wires. 'When the line of a subscriber Wanted for a trunk call is tested: and found busy, a busy signal l s' transmltted in the ordinary manner and the manual operator at the main exchange may then connect battery'to' the junction at Wirea'nd operate relay N." If the subscriber is at a sub-satellite exchange, the batterycon N in the opera-t er circuit thereat. Contactsm2 and n8 close a talking circuit over Wires pleted in the normal manner.

E20 and E18, contacts paQ a'ndpaii Wires E14 and E12 to the wanted line; Relay G isop'- erated from earth over contacts '01, p2 and 724' and the manual operator offersthe' trunk call and requests both subscribers to clear. When the Wanted subscriber has cleared, rel'a'y' P operates. and the connection is com.-

v The above mentioned talking circuit is disconnected when the called subscriber answers at 0on tacts cal and 2228. r 7

When an operator circuit is taken into use relayV operates and at contact v2 prepares a circuit for one ot a pair of delayed alarm relays and contact o6 closes a circuit for setting into action a timing device.

Earth is periodically "connected to Wire-1'0 and on the elapse of a prescribed period after this earth connection, a momentary earth connection is made to Wire 11'. VVhenear'th is connected to Wire 10', relay SA operates and locks up over contact cal and at contact m2 connects relay ZA to Wire 11. On the elapse of the prescribed period, earth is connected to Wire 11 and if the operator circuit is still in use, denotedlby the contlnued operation of 1 v I H e clrcult and said common control clrculta'ssorel ay V,relay ZA operate'sandi locks up over contact zal'. Contact 2612 connects earth over Wiper. B6 to operate relay inlthe connectorcircu-it (FigureQ-land contact 2413 re:

1 leases relay V. When relay V releases, the

locking circuits of relays SA and ZA 1sire and the connecting circuit remains held until the calling loop is opened. Contact oa5 changing over and contact 'Ufl/G not being operated owing to the short circuit across its Winding (I) and relay JT not being enerchange. r

gizedg. 311i alarm. relay is -'operated over Wire'l PL. (Contact: nil; inzthez: circuit otlrelaySA prevents the thnow out oiiltheqope'rator cir cuit when a: manual; operator atathe main exe I change oli'erstrunk call to asubscrib'er-at a parent of sub-satellite exchange-Uri.

What I claim is: a

l 1. In automatic?telephonesystenr, seabexchange, circuit,. a common CQIltI-O'le ling"circuit,- means forf temporarily associating said circuits, azplurality of trunk? lines extending to a main exchangefmeansi controlled by the association of said circuits'for operatin g said linlc circuit'to find an" idle-one of saidtrunk lines-, apregister, means for setting Silld register 1n accordance with'received impulses and for simultaneously rcpeating' said impulses oversaid trunk lin'e,'

and means for jr'eleasiiigs-aid trunk line when the setting otsaidregister determines that the call is for asu 2; In anautomatic circult, a common controlling apparatus, means for tempora -11y assoclatlng said coniouit, a plurality of trunk lines extending to another exchange, means for operating said osc'riber in". said", sub-ex-e telephonesystem, a link' so I y 1 'mon controlling apparatus with said'link airlink circuit to find an idle one of said trunk 1 lines, a register, means in said common controlling apparatus for setting said register in accordance With received impulses and for simultaneously repeating said impulses over said trunk line, and means for releasing said trunk line when said register is set to a pre determined position.

3'. Inan autoinatic telephone-system,,asub- V exchange comprising a li'nl rfcircuit andi a common control-circuit, means for tempo rarily associating said circuits, a plurality of trunlrlines extending, toa main exchange means controlled by the association of sai circuits for operating said linkcircuitto find? an idle one of' said trunlrlines, afregi ster,

means for'setting said register in accordance with: received l'll'l'PlllSES and for simultane'-' ously repeating said impulsesfover'said trunk line a. source o-f-ringing current, means for disconnecting said'f rlngmg gcurrent' at the common control circuit when said register determines. that the callis'for' them'ain eX- change, and'means formaintaining said linkj exchange answers.v

p'orarily associating said common control-V ling; circuits with said linkicjircu' ts tore s circuits j and j ter received impulses and 't'o controlsaid I circuits," a main exchange, inter-connecting? trunklines between said exchanges, means sponsiye" to a initiationef-fafc alI attire subsatellite exchange for seizing a. trunk line tothe parent satellite exchange and a trunk. line frointhe' parent satellite exchangeto the main exchange, and ineansfor repeating 5.6111 anautomatictelephone systeima sub- 7 satellite exchange and a parent satellite exchange Leach. comprising link circuits and common controll ng circuits, means tor tem porarily' associating said common control porarily associated withv said switch for the control of switching and other operations-inling circuitsiwith said link circuits to reg- 1 ister received impulses'and'to control said responsive to the initiationof a call in the a :sub-satellite exchange forseizingv a trunk line to the parent satellite exchange anda.

link circuits, a main exchange, interaconnecting trunk lines between said exchange, meanstrunk line from the parent satellite exchange to the: mainexchange, means for repeating the impulses dialled by the sub-satellite sub- .scriber to the parent satelliteexchange and 'main exchange, and means for releasing the I connector switch, a common controlling unit temporarily associated with said switch, a

common controlling circuit used in est-abli'shing the connection at the parent satellite .exchange when it is determined by the digits dialled that the-:call is change.

for said main ex- 16. In 'an'automatic telephone: exchange, a

plurality of connecting circuits commonitor a plurality of subscribers, a plurality 'ofcontrolling circuits common to a larger plural-.

ity of connecting circuits, other connecting c rcuits, incoming trunk lines from another, exchange permanently connected V to said other connecting circuits, and means for temporarily associating said controlling circuits 1 with said other connecting circuits.

7. In angaut oniatic telephone, exchange al plurality of connecting circuits common to" c change, a commonfcontroliunit, means re-f a plurality of subscribers, a plurality of con trollingcircuits common to a larger plurality of connecting circuits,other connecting circuits, incoming trunk lines from another exchange permanently connected to said other connecting circuits, a switchindividual to each ofsaid-other connecting, circuits and having access to -.a plurality of 'saidcona 8. In an automatic telephone exchange, a

plurality of connecting circuitscommon to I a plurality of subscribers, a plurality of con trolling circuits common to a larger plurality of connecting 'circuits, other connecting circuits, incoming trunk lines from another exchange permanently connectedto said other connecting circuits, a switch individual to each jot said other connecting; circuits and 65 havingaccessitoa pluralityoffsaid controlf ling circuits, means for operating onel ofsaid V switches to connect the associated connectnectionto apply a potential denoting the idle condition of said trunk at the other exchange, j

and means for disconnecting said relay and" for completing a talking circuit" when the idle trunk is seized.

Y 9. In an automatic telephone system, a connector sw'1tch, 'a com'mon control unit tema volved in the, setting up ot a connection,

it I in meansin said unit forrecordingreceived im-;

pulses simultaneously with the setting of said accessible to said connector, and means for modify ng the controlling functions oi sa d connector,individual, party, and trunk lines l unit inaccordance-with'the class of the line indicated by the setting of said recording means.

10, In anauto natictelephonc system, a.

andineans controlled in accordance with the setting-[of said register for transmitting sig nallingcurrent' through said switch when'an ordinary-line is called, for transmitting coded signalling current through said switch when a party line is called,'and' for preventing the f transmission of signalling'current when a trunk line is called.

. 11. In an automatic telephone system, a

change for extendingconnections to a main exchange or to subscribers in said sub-jexsponsive' to the initiation of a call for tempo; 7

rarily associating said'unit with said con nector, means in said unit forcontrolling said connector to find an idle trunk line ex tendingto the" main exchange, a register,

means in said unit responsiveto impulses transmitted by the subscriberinitiating said call for oaeratin i said re ister and 'for re;

line, and means for, releasing said trunk line said sub-exchange.

1 15 peating the impulses over the selected trunk when the impulse recorded by said register determine that :the wanted "subscriberis in av n"ADAMcHnisTiA V

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