Reference / Paper · 1923
Automatic Telephone Systems, Vol. 2: Auxiliary Services and Private and Branch Exchanges
Private and branch exchanges in Strowger practice.
Reference / Paper · 1923
Private and branch exchanges in Strowger practice.
Volume O'wo AUTOMATIC TELEPHONE SYSTEMS TELEPHONE H^STEMS By WILLIAM* AITKEN,'M.I.E.ii., A.Am.I.E.E.. Volume Two AUXILIARY SERVICES ANET PRIVATE AND BRANGI! .EXCHANGERS LOWDOjl, ERVESp LIMITED « BOUVERlfe ^TRfiET, Efldl4 1926 Itiule i^Gn^t BpHata^ Ntiu. tCo^ Ltd^ BMHMmOR PRE5^ACE The May in issuing the second part ot iniytircm& is i^grettea. This has been caused by the very intrictf^ nature of the work, on which only draug^lrto* men of the highest qualifications could be employed. The delay is also partly jlue^td somb of the important systems not being sufficiently advanced for publication. This, with the gr^t accumulation of interesting matter on large multi-offioe systems, h^ made it necessary to issue the remaining matter in two volumes. Vds in. will follow Vol. II. with only a very brief inteiwal. It is heped^that • • One firm uses an arrangement of diagrams edSentially different from all the otl^era.. In Vol. I. these were converted to the generally accepted form. This lias not found favour. In the case of diagrams, Figs. 86 to 90, both forms are shown on the same shgst, so that readers can form their own opinion regarding their respective merits. ^In one or two oases no conversion has been made. “ Bus-routing*’ of cir0uits is appljoable in»botli cases. The author desires to express his indebtedness and thante \o Col. T^ . Purves^ O.B.E., M.I.E.E., Engineer-intChief, G.P.O., and the officials of the^fferent <;^n)q>a^es whose work is described, for valuable assistance rendered. LomoN, June 1923. W. AITKEN. 1iOLrTLir?E OF CONTEI^T^ Of’A^lIjMES j. AND III. VOLUME- — — princi|Xe6^ Dial ImfulsI Si^bbs. — lepho^e inatruments. Sm>woEB System T. M. Co. A. E. —Switohiag apparatus-hunger and rotary lin% —Vertical and rotfi^* selectors and oenneotois, —Rotary ttumeotomr — and their rejMters, trunk oflanng, apparatus anj apparatus. — Rotary sdectors and oonneotors— switche^Y^^^ ^ Siemens' rstem ^Rotary Discriminators—Fault and group truzik apparatus and —^Rot^ switches—ContinuouB drive—lin^ todera— MAOHiEE-swiTOHma Systems (W. E. 200-line —Sequence switches— —^RdVerwve impulse —Apparatus and control—A 100,000-line Rotary system—^Lamp call-mdioator system, system — 500-line switches, construction and — Horizontal-type sequenoe switch —Line-tnders— Lorimer system—Apparatus and The SsTa^k of the ^Lrt, defimtioius ^T^ (A. Co.). : e/Vitobes oiiouita circuits S3 ^Testing line ala:pi]a^^>Ating, offering, circuits. Co.). selectors ^Registers circuits Pcuiel circuits ^Metering, circuits. ^MEBioAN Automatic Telephone Co.*s System. Relay System. —^Apparatus and circuits. Coventry Automatic Telephone System. —^Apparatt^ and drcuits. Standard Terms and Definitions. volCme Ilf. Automatic Systems in Large Multi-Office AREAS.r-Inoreasing the capacity of standard switcbem— Switches with a plurality of sets of wipers ^The Director system (A. 1^^. Co.) A^bcss tq large groups of trunks by standard switches Secondary line switches in trunib, with repeaters-^ The panel system, with 500-Une switches (W. E. Co.) ^The Swedish Ericsson Company’s systei^ with rotary and radial 500-line switches. — — — t —Working between manual and automatic (A. T. M. Co.) —^FuU auto^^matic wjth control from a manual board (Siezn«^)~^^uiction8 between manual and autdlnatio —Ke^oajd senders-^all-indicator systems—^Rota^-switch system (W. £. Co.^ Panel, 500-line switch system (W. E. Co.)—C^tral Control in Semi-anttmatio systems—^Automanual system A. T. Co.) — system (Siemens) —^The^Christensen automatic distributor—Unattended —Order-wire working. Metering or Registering Telephone Calls. —^By reversed Sattery—By increase of ourrsMt—Zone metering—^Telephone unit—Cumulative metering. Trunk or Toll L^ Working. — perating without T. MT 06.)—fii^-^Qyquenoy Semiautomatic Systems. offices offices (C. ^Traffic-distributor offices oiSSrators toll lines ringing-hiantom or superimposed working. —^Multipling-^Distributing and slipping—Over£k>w switdies. Layo|tt and wiring. » Wiring Sohebceb. |*otvBR Plant. Tbafvio. — —^Rptary ^^tish £. M. EricSion avj^oi&atio system, usiiiK oordi|^ and plugs and radial switches with horizontally wii^ banks ^By-path systeii2i, *eto.; etc. IfxaOBMUNiioUB SYiTBSM — s&NQj^ LIST OF SECTIONS’ Eqttipment in SubsoriKers’ pfl^pes . • • ^ • Extension Instruments.^ Wall Sockets and Plugs ,* ^ S . • M Simplg Extensions .a Ex^enedon Lyie with Intermediate Switch • • 8 t> • • . 4 o »» Coin Boxes. On Direct and Party Lines Post Office Circuits f . ISm M f. o M „ Circuit with Tone Signal Sub-station Call Meter 7 99 8 Party-Line Working . ^Frequency Selecting Connector Circuit (A. T. M. Co.) 9 99 .0 M Discriminating ligr the Selector (A. T. M. Co.) .1 „ Frequency Selector (A. T. M. Co.) Reverting Call Switch (A. T. M. Co.) .8 f» (W.E.Co.) .8 „ .4 „ Lines multipled over a Plurality of Groups of Connectors Look-out and Re-ringing Circuit 8 99 1 ... . . . . . ,6 .7 Si]^ Switchboards. . .... • •. ...... Selective signalling 99 . . . Up to 25 Lines. .8 9» 99 25 to 60 Lines .9 9f 99 10-line Cordless * . . (Post Office P.B.X.) „ ,, ,, 56 60 66 68 ,, Branch and other Small Offices. Typical Arran^ments • British Post Office and Traffic Facilities * 99 • • • * * Automatic District Offices in a Manual System Main and District Office Alarm Apparatus Branch Offices. Full and Restrict^ Servio% With Direct and Party Lines 99 « 99 Local Connections without utilising Trunk to Central Another circuit 99 99 with Rotary Switch • If 99 „ 99^ Connector operated from Selector or Toll Operator „ Access to 9'*GeoupjDf Trxmks on a Plurality of Levels (A. T. M. Co.) „ •Final^Selectors for Indi'^dual Lines and small P.B.X.’s and for large • on a Plurality of Lev^ (Siemens) • A Small All-relay Office (A. T. M. Co.) 99 Private Automatic Installations in Works and the like A. T. M. Co.’s P.A.X. System 99 , . . * ..... . . * . ....... ........ . . 99 ^99 ‘ 99 99 99 99 •f f* 99 99 99 99 99 99 Double KumbeHS’ick-up Siemens Autophone Sjptem. 190 lines 99 i ,9 99 99 • 99 . • . « • •81< 7 ^6 83 88 links 92 .•104 . . Alarm. . a. ^ 107 • %09 .a 111 % . Interce] Interceplion. *5 * * • 99 101 . . . ^200 lineal. PoWef and Aldnn Circuits . S A 99 99 . Switches. Connector Circuit ^ 99 Selector Circuit „ 2-wire Repeater ^ . . and Manual Service Special Services M Code Calling using Selector Levels 99 99 modified Code-Calling Circuit Miscellaneous Ser^cea. ^ Watohxnm’s. Fiijp . . . W73 75 77 • • 99 . ..... .... ..... ...... ' 99 . . • . « Secretary 116 118 122 124 Autmi^tio Inatalktioiw in Worto md the like. BelevJink Syetam (B. A.*r. Oo.) ^ „ ” /•Setoot-O-phoM Syeteift Pettifiw A^ernmw 48 . .. 49 „ A Oiieoit <5f the Bteveoe’ BJrstem „ Coueh System. Pr. Tele, and Baeo.TCo.. Village Automatio Efobaage (Siemens) •I'c Connector SB 88 „ Junction worki^ 47 . ' s . ^ „ „ „ Common Apparatus Routine Tester ' Power Plant ^ Objects and AdTantages (A. T. M. Co., A. E Co.) We Community ExchangessC Types to meet Different Requirements ^ ^ 68 * • rirtnnftGtor Connector 69 Automatic Voltage Regulation 6Qe Circuits for various Services 61 \66 . . . • • . . . • • ‘ ’ . • ...... ..... SUPPIiSaiBNl? TO Vox.. I 68 68 Bntislf Post Office Dial No. 8 New Design of Wall and Table Telephone (A. T. M. Co., A. E. Co.) 64 „ with H.M.T. (Siemens) 66 An Impulse Equalising Device (A. T. M. Co.) 66 c Coni?Jinser Pevioe to repeat Impulses to Switches (Laidlaw) 67 Ah Impulse Converter (R. A. T. Cb.) 209 213 215 219 . 222 .<^226 . . . . • USX Off ILLUSTftATldNS F|^f EEftlfOIlmK MVU XMJU«7 TV \fJl, „ „ M „ 1 2 3 4 , „ f „ 7 „ „ „ „ „ 8 9 10 11 12 « 13 • • „ 13a „ „ „ 16 17 18 19 20 21 ft „,g (Siemens) 27 „ ::3i ,f ^ 42 3 . . . 4 5 , • 6 6 • . 7 . .... ...... (W.E. Co.) A 4-way Switch 8 8 ® 10 s Intermediate Switching Set (A. T. M. Co.) A Battery Indicator (Drum T5rpe) (A. T. M. Co.) •If 12 Post Office Circuit of Bell-set No. 4, with ^-position Switch ft „ with 4-position Switch Explanatory Circuit of above — 13 14 16 18 19 21 • ^ Wall Instrument (A. T, M. Co.) Table Instrument (A. T. M. Co.) M „ 22 23 • 28 89 31 p. ff t, ff „ •• f, * • „*(W.E.Co.) P.O. Circuit for two parties Look-out and re-ringing (A. T. M. Co.) , Slow-acting alternating and D.C. relay (W. E. Co.) 4-party Selective ringing Circuit (W. E. Co.) . Detail of il^^d Sabnri^tion Switchboards to 25 Lines Sapadty (Pofl| Office) M "to to 60 LuAb oapaoif^ (Post Office) 32 35 37 89 .41 l^w-f|equenoy Instrument Circuit (Leioh) mgh f^quenoy Instrument Circuit (Leich) Harmonic flinger (Dean) „ Details (Dean) „ Circuit (Dean) Converter (Dean) pf Frequency Meter (Hartmann Detail of Electro magnet — M . . a 87 as 39 40 41 1 .a t ’ 29 30 81 32 34 36 36 . „ Party Lines „ Frequency Selecting Connector (A. T. M. Co.) ,T Oiscriminating by Selector (A. T. M. Co.) „ Frequenc;f^electqr (A. T. M. Co.) „ - Keverting Call Switch (5\. T, M. Co.) . 26 * M Coin Box „ Explanatory Circuits (A. T. M. Co.) „ Wall Instrument (A. T. M. Co.) M Table Instrument (A. T. M. Co.) „ With Tone Signal (A. T. M. Co.) „ 2ft . (W.i;,Co.) ^ Simple Extension (A. T. M. Co.) Table Instrument Circuit (A. T. M. Co.) Main Instrument with two extensions (Siemens) „ Wall Instrument (Siemens) „ Table Instrument (Siemens) „ Secrecy Switch (Siemens) Main Instrumei^t and simple extension. Table Instrument (W E. Co.) „ and two extensions (W. E. Co.) • Sub-station Call-meter 24 ^ Wall Sooketa and Pl'ugyt^. T. M. Co.) f^ion^Vilew •41 • 42 42 48 43 44 44 45* 50 ' I'**' " yi /S - . . ' » ' . Bubnifcttiipii Bvdtohboifds^ 44 44 46 47 A Dt6p Indiofttdr „ *e' • » 0* . • C<l) . «Axi E^reball InHioator /W* ^ . . 65-liniM oa6a£ty (PosrOffi^e) CoidleBS with Negative Gearing Sigilal8d(Poat Office) „ Positive (Rearing Signals (Post Office) c • BraiEgh and other Sub-offices . ,, M o „ 4i 49 ^ — „ An Exchange Sgstem with Satellites «> Typical Branch and other cmffll Offices . »> c 61 . . ,, r <j* ^ Manual Working c Sn^ Central and Mixed Services (Community) A District Stations through to a Maifoal Office. Circuit*^' MA.niifl.1 through to a District Station. Circuit „ 64 56 < c^ . . .c „ „ *62 Transfer worldng of District Station. ‘Circuit 64 6$ 69 70 « • ‘-r . ' 71 72 Unattended District Office Trunking (ArT. M. Co.) Branch Office Supervision at Main Office (A. T. M. Co.) Branch Office with Service Discribiiziation (A. T. M. Co.) With Direct and Party Lines. 300-line Connector (A. T. M. Co .) 66^ . 56a . 57 58 59 60 Multi-office System. .73 ..... ...... fl Lay out System with Switching-Repeaters. Satellite Office Main Office 77 77 79 82 84 . 61 „ ,, Loc^ Connections without utilising Trunks to Central 62 Method Alternative 63 ,, o* t MA** »# ^using a Rotary Switch 64 65 A*P.B.X. Connector accessible to Selectors and Operators (A. T. M. Co.) 66 ^ A Branch Office 1 -digit Cbmiector, giving access to Large Groups (A T. 67 A Branch Offide (Final Selector) Connector (Siemens) 68 „ Fo^ Individiial Lines and Small Groups^ of Trunks (Siemens) For Large Groups on a Plurality of Levels (Siemens) 69 ,, 70 P.A.X. An All-relay Small Office Ciw^iit (A. T. M. Co.) 71 P.A.^. (PrivatciAuto. Exchange) lOO-lines (A. T. M. Co.) 72 „ Connector Circuit (A. T. M. Co.) 73 o Sflector Circuit (A. T. M. Co.^ c74 B.A.X. (Branch Auto AExchangp^ 2-wire Repeater (A. T. M. Co.) M. (A. T. Co.) Working 75 „ Manual ^ Cord Circuits (A. T. M. Co.) 76a ,|C \p * 086 M Co.) 0-89 93 94 94 97 99 104 Folder, facing . ..... 107 109 111 112 • « P.AvX.an4B.AVX. 76 76a 78 7fl^ * 80 ^ 81 82 « 88 84 86 91 92 93 ^.A.X. ^100-lines. i, t *» Siemens Autophone No. 2. Rey diagram Discriminator for 200 Lines. . . . # . . Siemens Autophone No. 2. KeyDiagXtoi Control and Alam Greuits. Siemens Autophone No. 2 „ Key Diagram Power Cumuts. Siemens Autophone No. 2 IQjdline No. 2 Autophone (Siemens). General view Dynamptox for above ^ -CM 127 128 129 129 Greuit - Circuit Folder, facing ...... . . .... 93a Pynamotoi^for VillMe Exchai^ oO-line Relay Sys^p l^-out (R. Aj^. Co.) . 50-line Relay C^uit (R. A. T. CoJ . * „ Manual working with Main Office (ift A. T. Co^ M Trunk Co C.B. Office (R. A. Tf Cg. ) ^^tem isl . <64 95 96 97 116 119 128 125 . ^ 90 115 415 . ftft 87 88* 89 < c Special Services. Conference Circuit. 46 Volt (A. T. M. Co.) „ „ 12 Volt (A. T. M. Co.) . Alternative (A. T. M. Co.) „ S, Code Call (A. T. M. Co.) . „ Using Selector Level M „ „ A modification . Watchman’s (A. T. M. Co.) . Fire klarm (A. T, M. Co.) „ Secretary’s (A, T. M. Co.) M Double-number Pick-up (A. T. M. Co.) „ „ „ H ' M „ M „ M c 77 4 Vi'?, • Polder, /doing • 4'' • 135 136 137 137 142 146 146 U6 : . jji^A^ifc. ;'96 Bcl^’» 0 -Phoiie Oiryuit <Peti4gr0W ik Mwinum) «, /£iiiwl immgenie^ .^ . • « .* » I&slJ^eait ••.*•••**#* ^ A Stevena* * fSrcuit y 4 lOO-pSint IKal. Couch System (Pr. Te]e.«aiia Elec. Co.) lOli s: * * . •• • • • ^« • . , 104 105 118 100 107 108 108 110 111 Couch System (Pr. Tele, and Elec. Co.) ^-Selector, front ^ew. tew viemf. CShioh System (Pr. Tele, and Elec. Co*) ft ft Couch System (Pr. Tele, and El|c. Co.) Instrui]Q8|nt. ft VQlage Automatic Exchange ffiRemens) * Front 50-lina Rack. ft . f, ft *,t ft ft f, 113 • IjC 115 116 117 118 119 120 ft Rear* — ft To Trunk Office . „ „ „ • • • 151 lol 151 151 . ^ • • * 154 Un Folder, facing • ^ *•••*• * . . . * . . . . ...•». . • * • ^ . • ........... ............. . . * . . • • . • . . . ^ . . Folder, /going . . . 108 AOO 107 168 • 169 Folder, 176 f . 178 181 Folder, /ooing 186 184 ^ISS . . Network Type Lay-out Connector C&cuit Automatic Voltage Regulation Typical Circuits 148' . ....... ... ...... ........ ........ ......... — ........ . Dynamotor . ' . 124 • . . 147 148 , lA . „ „ „ „ „ • . • • ^ Party-line Working (Siemens) Common Apparatus Circuit (Siemens) Jimction Alarm Circuit (Siemens) Routine Testing Circuit (Siemens) ,f „ Power Circuit (Siemens) „ Petrol-electric Generator (Siemens) . „ Power Board. Front and Rear (Siemens) C.A.X. Community Automatic Exchange (A. T. M. Co.) , Isolated Office Lay-out I 2 I0 * „ • 1216 „ Tandem Office Lay-out 421c , „ Radial Type Lay-out 121d 122 123 123a . * . . C.B.S. Junction •. „• Junction. Without Supervision Magneto ^ V, „ •With Supervision ff .. . . Bothway C.B. Junction ^ . . . _ Connedtor (Final Selector* Circuit ,? ,4 • * ; . i* . 1 1#T ' . .« « » . • • • Fglder«/aoing ^90 190 196 190 196 198 199 206 Supplement to Vol. I. 125 P.O. Standard Dial No 8. Front View. 126« „ Interior 127 128 „ Section % Parts 130 „ Impulse Qp^lograms 131 New Design Wall Instalments (A. T. M. Co., A. E. Co.) 209 209 210 •210 211 212 213 214 214 214 215 » 216 •217 . 432 133 134 135 136 1«7 138 139 140 Details ......< ....... ....... New Design of Table Telephone (A. T. M. Co., A. E. Co.) „ Details New Design of Wall Telephone with H.M.T. (Siemens) New Design of Table Telephone with H.M.T. (Siemens) Circuit for above An Impulsd Equalising Device. Circuit (A. T. M. Co.) Condenser Deviae to ^peat Impulses. Circuit (iLaidlaw) An Impulse Converter. Circuit (R. A. T. Co.) I •••• . * ^20 222 225 EXTENSION LINE WORKING LINES WITH METERS A*ND COIN-BOXES ySecdori i ! EQUIPMENT IN ^TUBSibftlBllRS** (^FICeI ^I%e0e lure sometivies spoken of sub-station equipments. Impulse-dials are ^escribed 4 to 7, VSl. I.* inclusive, and instruineiits and tiieir circuits are described in Section 8/ in the latter these (Mic» however, sboWn in cbnmection wfth direct lines only.* ^ ' Exteaeibn^ Instruments* ^DifiFef'ent types of service may be given to extension in-< be in paraUe^ on the same Jj^ne stiruinents. one only, howe^es, Jwo instrumenfig sho^dAbe fitted with a bell to receive calls, the second instrument being called on a separate A fe^ circuits of standard arrangements foUow. bell and push circuit. # Wall. Sockets .and Plugs. ^Fig. 1 show^aq arrangement for use on the A. T. M. Cb.’s • 'in Sikitions — ; , — system* A plurality of wall sockets can be fitted, three being shown in the diagram. Each socket has one break contact, shown at e, and this contact is opened when a plu^is inserted. A bell and condenser may be fitted at each socket, or at one socket only if alj^dalls, when tim plug is not in a socket, are to be feceived at one ppjpt only. ibSve the strap connection, c, jombd across to puts the bell in.circuit. of one station, must A plug is associated one instrument whicji caif be carried from^oint^jo poiiffc as required. It will be noticed the contacts of the s,witob8s aredn series, th^wtre then connecting to a cemmon circuit '.^atJUPMENT IN' 2 ^ to all the bell|. 0 , _ The aocket next the exchange line 1;^ two tenninalB strapped by a wir^d, to complete the series circuit. If we assunle ^l^t socket h oi)^y has tj^eca^ied^ tion e made, then a c^U will %e leceifed fr&m thb exchange on bell 6' over ciroi^ If the plug P is inserted in the socket A, then £u call will be received on bell B' V^nd t^ oi^euit/ ^ will be e;pened to the dbher bell. Circuit 3 is the speaking circuif. • A call ma^ be ipade from any one of the sockets by the impulse-dial. ^ ^ Fig. 2 shows a corresponding^rrangement on the Sieimns System^ A bell-ijpt* including f ^ Fiq. c 2. —Exteksion Lines (Siemens). Table Telephones with Wall Sockets and ITlog. « • The point which is to receive calls when the plug iVnpt ifiiterted njust h«(jve the {Ubrap comection, c, across. The bell circuits ijsre again throf^h The circuits a^e numbered as before, 3 being the microphone circmt sefies contacts e. and 4 the receiver circuit. At B is shown an explanatory circuit. the line, and the In the* two systems mentioned two bells must not be in parallel This prevents the circuits stawn^tthe necessary precautions are takeij to prevent this. possibili^ of prei&atur^ ^/ripping of 4;he exchange ringing ^hen a. subscriber is being called/, an iijducti^S3oil, is fitted at each socket. m or interference* with the diaUing impulsesf owing to condenser bridges on the line. A cdrresponding arrangem^t forcthe W. E. Co.’s system is shown in Fig. 3. In this 'system the ol^ectidn to bell and condeihtei; bridges is not so ^eat,end this Simpler cireiiit iiS' . Fig. 3, —Extension Lines (W. E. Co.). Table Telephones with Wall Sockets and Plug. The diagram cifcuits are numbered, to agree with the previous diagrams, and the explanatory circuit at B will make the arrangement clear. between terminals 2 and 3. ^ j MamStt • * Fig. 4. —^Extension Lines (A. T. M. Ext9HtZ» Bxi9n»1* j Explanatory ClrcMiJt* c . • Subscribeb*s Tab^ anj> Wi^Sars with SmFts * Extensions. . ^ Co.). B a wall instruitfent is fitted at the main offioe. At C is an explanatory cirouit. A pushbutton switoh is fitted at the niain ofiSoe for each extension instrument, and a trembler bell is fit^^t*«a!bh extension, current for ringing these being drawn from the central batte^ cxoha^e line.f Whep^ a c|tll is received for an extension office the switch is pressed, and* when the extension receiver is lifted t^e instrument is connected ih paralld across the exchange line. When the main or first extension telephone is in use the polarised bdl is cut out of pirouit, but when the second extension is in use, the bell and wondenser are a shunt across the mrcu|t. * The extension instl^iiments are wiirMl according to diagram (Fig. 5). ^eprinci]plecircuitsto{Fig.4%reniimbereda8folloi^s«: ^ t. Einging circuit for inward calls. ^ maVn station. Di^ii^^*from the main statimv 2. OaOhig or imorophone cuouit opens drbuit if* ' M du^ impulsing. Short-^rouit about receiver and,transmitter ]^inging cir^u^ to call ex^nsitiiii Noi 1. 5. Binging circuit to call extension Ko. S. ' Kg, 6 shows a Siarpana oircuit for a main instrument and two extensions. Apolafised A dial is fitted at each station so bpll andVn induction coil are at the main station only. cWft are recdv^ at the ^ivward point, |^ny iroip originated be carf calls outward that then toeing drawn switch, station, and any extension can be oalled by pressing a , and at B diagram, wiring a i^sjiown At A bell. pver the exchange line t(^ ring a trembley 3. 4. cu^t Exten&ion. 1 Aa, 7.—E*xtbn8ion Lmas {SncMBNS). • X Main Set. SniM.B Extbnsions (Wau, lNSTB<rjtBin!).r 0 An exj^anatory one. The oirouits are numbered in a manner corresponding to the previous dij.gram, btit^in the case of ourcuit 3 the receiver oircuit is opened instead of being shortcifoi£tea. *• . •Ii/fig. • . . showh anotlfer simple oircuit with a bell at the maip station for inward Wall instruments are used throughout each instrument. Again, there is a push-button switch at the main instwftnent for each extension and a trembler bell at each extensira operated by ourreni drawn ovei?^ the* exchange line. Outward calls can Ife originated from any instrument bj Th^ birouits are^nunjJjered as describ^ for Fig. 4, the recover oitouil TtwOvided. the calls, that at the extensions being short-circuited. There is an ijiduction coil at • being 6p^ed whilst dialling. In Fig. 8iis shown a rimilar circuit ananged fof tables insi^ments throughout, bul . fesembliug Fig. 7 in that tbete is j bell an# induction coil alythe main instrument only. Sien!^ ^V* Aows 8^ “““ ““t^rnent aaiother « 11 circuit, but having a secrecy switcl^ so that wh«B for the,ex!ei^on, thg push apdtoh is preamd to call tl^AMi^^iId fh! secrecy switch operates th«exiw»sion.^andlhe when th« extension ‘calfi wrthqpt being overheard at the main conversatipn. ? i“^T f??*®“““ instrument only, but an induction tostruaen^*”***^ Kg. 10 a W. E. Ck). sirgple extension using table ^ instrument only. A polarised' Main Set* A at each instnSment “T *.“**^™®“*induction coUinward at the main instrument is*cpmmon only- for the extension. coil is fitted at ertsh ^ Extension. fn^ converse over the The switch should.be Jt opens •circuits 1 and f. There instrument. callm dial is At the main instrument is fitted a push^itch for calling to it th^^t^on bell,*opOTated.by current drawn over the exchange line. is showffthe Wiring dia^am and at B an explanatory diagram. numbered simUarly to the p^receding simple extension ciilaiits, and are »8 foIWs*'^'”** Atl !• ^ Binging circuits for inward calls. microphone cJcuit of main stiftion. xwoirit 8, Short-circuit*about r^Seiver during impukiilg. Dialling from the m4in statioif opens Citt^efon 2. Extensi^ 1. MainSet. SarH^mSxt^f, |r;x2jr^ “ “1K. JJ Dm/SwkcH Cable finam. B flame-^proof a^2•4^f Explanatory. TfTOTT-/ ^ I Fio. 11 .—Extension Lines (W. E. Co.). Simple Extensions. Table at E^ktensions.* Wall Instbdmbnt at Main, • • Extension. -- «> : 'fs Cabk,enam, A fkune'^proofy DMknii ir explanatory. ^ ^^ ^ ‘ ^ Hfl'CMNBlON liDraS C0(f, .* F~ I , SUKiB ^J^CCTNSIONB. TaBU TwaramniniB Wall Jnbtbttkbhts A^ExKBNSioift. fi b; aip HI .nr ' IP MATES' T^/lTa « Bin^ng oirouit to call extension 1. Ilg. <11 shows a (limilar ^cuit f<;»r fwo^extei^on instraments, tha(^ at the mAhi heb^ i wall set and at ea6h extension actable set, The circuits are numbered as in the previous diagram. Circuity 6 is tha£ of thjB sedend 4. ^ » ^xtensioh bell. " ' c • Pig. 12 shows a W.cE. Co. arrangement with a table set at the*i]^n office^ and a wajl set at the extension. The polarise*d bell at tbe^extensipn is 16ft disconnected. The extension There is an induction coil at each is called by a trembler beU operated from the main office. r The princip&l circuits are numbered as for tfife previous diagrams. iiullrument. c Section *3 Itxf&NStlON P>T«aR WORKING WITH'IKfrERMEDIATE Post OfBce Bd|B.Set, No. 4.—There is a main ofiSoff THROUGH SWITCH and an extension on aii>*exohang6 Vtrtioal SeeUoii H ifontal ftf Fig. 13. —Four- way Key (A. T. Fig. 13a. — Intermediate Switohino Set as USED BY Post Opfioe (^. M. Co.), M. Co.). line. ^ The main instrument is equipped witli a dial so that outward calls may be originated. The switih is pim^^rily designed to give secret service when the main or extension is tnlfrir^g (a) Normal Fmitira (Section). Drum or Morlng Part. Fio* 14 .—Dbxtm Imdioaiob (A, T. M. C<^^. ' ^e exchange, but it oanJbe adapted for non-secret w(yking. This bell-set was ofiginally designed by the apth<5r, thf 4-way switch ^own*in Fig. 13 being used, and irvm battery to indicator (Fig. 14). * * • tt- . ,3 fob tip Johobd Wobking. Autoii£tic fob 4a No. Bbu:.-S®t OmoK Post .— 16 Fitt. ' cibows a Post OfEioe Slg. lasing a 3-pofiltioa key, aad Vig, ^ ^•In^g! diagrai^, ^ a Pd«^ Fig. 17 is jm e}q>lanatoFy^irouii lor koth these * three living the circuits siniilarly^np^ I Office eiioiiit iisiqg a 4-po6itio{i ,8\!fftoh. lil^the (&rctlits completed in the difiprent positions of the switch ar^ as follows — ;— the exchange, extension line dn bell. Position l.-^l^ain connected to extension, exchange on be]}. Potion 2.-*^Exchange4)o extension,•circuit to mStin cut. '^Normal . cojinected Positim 3 (dpriihga^ 1 and 3 hctuated). Exchange held. bell. —^Main to extension, exchange on extension* Poinisr to position 1 sti springs normsi Msm is Exchange, Extens/^n on Extension BeM, • * • 2 springs 2 and 3 actuated Main to Extension, Exchange on Extension Belt, m hotdt • m • • 1,Z 3 3 ^ • • Exchange to Extension, *^••*34*4 Fig. *16. mm —Post Office Bell-Set No. 4. Joined up for Secrecy. • • • In Fig. 16 these are as follows Normal, ^Main to exchange, extension on extension bell. ^ Position 2 {spring sets 2 and 3 o/ctnated ), Main to extension, exchange on Jbel^. Positim 3 (spring sets 1, 2, and 3 admited), Exchange to extension, exchfij^ge h^d« Position ^ispring set 4 at^mted), Exchange to 'extension. : — — — The circuits are numbered as follows — : Binging circuit of exchange line on bell at main. (over 2 1 ). Talking circuit to main. 3. Extension line on extension bell. 1. 4. Glenerator circuit for calling extension. 5. 6. Exchange on e:!(tensi(>n bell. Extension on main MU. ' 14 ' A.-* Switch Lever NormaK - MBin Tehphone on £icfjfin^t Extension on Exteipston Ml* ^ ^ , • Uutonwtkf^kphoneiktManrSet ^ A line ^ ''* ’ From p a cl To Extension*^ Exchan^ , 5 line . B.- Switch Lever in Extensiqn Pp^it^irfn. -Jk 1 ^ Extension ^3 Ball 0 1 Indicator 4 Bline — Ato/n on Extension, Exchan^ on Extension Automatic Telephone A Ime . ' T ^nenator ' ML A hne 6-7’B ^^rom c Exchange * Extension • Bell, *^ 1000 *, . B hne ^ s C." Switch Lever !n " Main Set to Extension, Exchange Held ” Position. ^ ' A line , i-r- ^ From m A line Automatic Telephone at Main Set % Generator S 7-6 , Contacts Generator Winding Exchange Extension s 2mf. Extension Local Battery Mh 1000 ^ Btine • • * !• Bline B 6>7>B I'l .-Switch Lever in *Extension to Exct^nge** Position. fht»:^E^ay smadeshw^acting ^ A )k * by shortdrcuitlngone wmding, m This ffevente the dignallirg tmpuhes actuatmg the ^ — j — 10 T»jr— , • Extension ^ Man Indicator I From ML Aline Generator Contacts , ExcEangt To , Extension , B line * B line 17 ^-^Post Ovwi^ BfeL^SsT ^o. 4» fjsED #r.B A^matio Woeking. c riTOnxiTpa. , r-r n Ficr. • * ExelanatO&y e 7. 11. Sxtmision talking to maii^ ^Oeneratgr circuit to call^extension (same as 4). Exchange line holding* circuit. * ^ la Exobange\o extension line, talking circuit. * Condenser 12. sh^nt across SO-^fhm coU ot relay. bndgetj across loop (i.e. across circuit 10, by Release of relay when the^extension receiver isj«placed)f* ^e vol^e of the battery for tblking between the main and the extension should^be van^ acoo^ to the resistant Jf the line. Fey particulars see^the figures on the diagram. When the s^toh is t<ibe used for non-seoret working, a strap is connected between^e tormina s .^nd A and bqfween B and B'. (Tircnit 13 then connects the main instrument m parallel with the exchange-extension circuit. w FiniBB WHIli Section 4 r DIRECT AND ^ARTY LINE% FifTED WITH COINBOXES * r. ^ r • For ^11 offices, hotels^ and other public places, where the Ujser ^ust pay for ei^h conversation, such coin boxes are very^ desirable. Party-line working also a very suitable field for them, because a meter at the central office could not readily bl^fknade ^LLJ ^ to differentiate betwben two offices which might be rented parties' having no i^lationship one g y ^ g ^ M other. r , 8uo 4 e^^iipments it is essential that it a client be able to call the exchange without fee, and also be able to call the party wanted, and, if the line is engaged, pay ho fee but if the party replies a fee must then be paid. The party called must be r cti ; able to 'indicate telephone, but it attendance at the fnust be impossible to his carry on a conversation until the fee is system designed by the Auto- paid. A matic Electric Company, Chicago, is the only one in general use. Fig. 18, showing a circuit of an arrangement based on the above system, l>y the A. T. M. Co., is used as an explan|.2/ atory diagram. The essential apparatus, in addition to the telephone insWment ^nd coin box having a chute, is a polarised relay. This resembles the polarised bell movement of a telephone instrument, < and acts as a 2-way electro-mechanical switch. When a caU i^ made» and the battery on the line reversed by^the lifting of the called receiver, the nlicrophone is , , short-circuited and the receiver is shunted by a 30-ohm coil. The caller cannot, therefore, communicate with the called • 4 , ^ hut the response of the called party can be heard. The receiver is rendered in- —Pay Stations, Exflanatoby Cibouxt o^CoiN Box (A. T. M? Co.). i efficient^ thaiy if cannbt be xAed as a trai^smitter. When a coin is inserted in the chute, or a coin inserted and a lever turned, the short-circuit and shunt are removed, so that conversation can take place. ^ The batlfery ^n^the line is not reversed when the c|ll is to an “ information ” operator, nr when handIngMn K tru^ call, or ^hp like, and no fee is payable. Indjcatps to the ojj^erator tnat the caU is from such a pay-stahion. — A buzzer in such cases The eifcuits ot the explanatofy diagsam aie as foUows * , a. When the rwfiver is lifted to caUf the magnet aE is efiergised and the armature is : WXf i 16 to the position shown in the*dia«i?Mii. Ji *****+ * attracted to the Ji is ^ 18, TT **‘® W P»rty answers the oi^ntin circuit ^E.* The eftension 14 on arm 13 arm 16 to the right. The moving spring iT-is pivoted, c^ses a set on^l^^ tto am ,16 of contacts. » i* JHS A. SJiprtTGirctut abbut ftie microphone. c. atet about tfce’reoeiver^ The callinft8ttb8crib& «an hear, «ut ^®*‘*^* **‘® cannot speak. 23 falls, and, as the spring 30 has been, ««nrj^ to the riht by the ihsulqMd oam^ pencil 36, tl^ insulated parts37 falls behind spring^ft Md locks It in tfiw operatedjjosition untU the receiver is replaced. This lever is not dioyn hi “ provided,*in this case, to meet trouble that sometimes hap^,,d^ to the receiver being replaced wh§n the party first answering arother party to th6 telephone, and the like, when the has to bring current in the line fa restored to S nom^ condition. A s^ond reversal then takes place, and as the switch has meantime done ^ back to nomal and again energised, a second coin has to be inserted. When the ca^ed party fa heard on the line, a coin is immediately inserted in the chute 21 when the end of the 16, shownprojecting into the chute, fa am depressed against the action 14 Js free to pass over the lug 16. The 16 then ^ totfreleftby the tension of sprmg 18, when the circuits 6 and care opened. * »aL Short-circuit about coil aE. Should the called receiver ^e wrongfully replaced and again removed, the battery reversals will not affect * thfe calling apparatus • e. High resistance winding cE energises ftnd returns amature 12 to nn»win.i xhe extension 14 lifts the lever 23 and circuits e and d arelipened. When the calling receiver fa replaced, the apparatus is restored to'normal,’ and the exchange apparatus released. am p^s u pT otmm cmct!Wfe Section 5 POST OFFIGB CIRCUITS FbR COIN-BOX UlfES * 0 • Thej^e differ somewhat from the theoretical circuit before ^des^rihed. The Idver ^3 is not used and the polarised relay has its two coils connected in seri^,;the resistance of each c ‘ • • • • , Contacts ia2 are normally inakmg. When com is insjorteoranol handle turned 1S2 break ana Z&3 make ^Floating sprfng on Relay k depressed andpleased firom the aqfnature arm; this rgmt^ea ^ shunt and short ccg> from receiver and transmitter Wall Telephone a CL * White *2mf. iBrownl Cord Flex I 2 Cords Flex Pm/^ Lliht c «iJL Green eOA pL CL grange •4^ \ «?+ . ‘K -r CL ' I riT^ i f CL C6rdFlex\ fo^extrarec^ Exch,Une ifrequired* -8 .a Modification for Partly Line workin^i ^oP'"X Party* Fft an additional terminal. (4\aa shown In the explanatory sketch on Fig, 20 In doited lines, and connect to earth, Tranefbr, the wire from the back contact Sr the switch arm to terminal/ 4^ For Fit additional earth terminal (4) as above, Dlscoiyiect at teienlRal 3 the wire from thk wiae4rom the bell coll and connect It to Terminal and strap the switch arm to bad ** * Party, « 4 ' contact* o Note,’‘For Table Set see F!^, 20* »Fig. 19tf— Pay Station. WiflLL Instrument Circuit (A. T. M. Co.). Post Officb. As used by British bemg 5*ohmS. * In acfdition Co a coin beii^ inserted in the chute, a han^lle or lever is turned so that the weight of the coin does not control the movement. When connection is made to an information operator, a trunk record operator, and the like, su^ services requiring buzzer is included, so that these may no fee to be* pai^, ^he line battery is not reversed. A be used on mafluaf sys^|ns when ^l^e operator will hear the buzz on the line and be able * to ch^k the number of coins inserted, in % known manned. Fig. 19 shows the combinatkm Of a wall instrument witlf suc^ a coin box, and Fig« « table telephone. fThe explanatory diaigr^m B applies to bo%])i wiijngidiagrams. are numoerea anadue as tauows 0 'When tiie j^epriver is lift^to* make a call, a tiz^nit is oc^plefee^ through th^ polarised relay Sfitoh (whicl^ shunted by a ooxuftnser). • The reky isset in the position shotm in th^diag^m, dis desorilM for Fig. 18. , ' a\ The short-circuit about the buzzer. The caller dials the number waijlbed. The coin should be in the entrance pf the chute, * BO that immediately a response^is heard it is released and the lev^dtumed. When the called party 1^ {he receiver to aJhswer the call, the line battery is reversed. The polarised relay is energised in the revers€f direction, aifd two contacts closed. ^ b. The short-ci]%;ui1^ abooft the microphone. c. speak. The oatter oa^n, therefore, hear, but oao^d ifhe d(kofam shimt about the reoeirer. • . - V. « When the leveais turned, cireuit a' is optMued^and the buzzer tone is^ven to an 9t>erator, if,the call is on a manual system. /. • ^ The floating arm 10 is depressecl so that the extension 14 of armJS passes o^rer the catch \o return the relay to normaf. The talkfbg circuit is«dow complete with ihe receiver and microphone miseries, through circuit a and a\ ^Tliip receiyed currents^re through the Condenser which shunts fbe polarised relay. 6uch a device is very suitable for paijby-line working. For a direct line the ball and conde&ser are connected between the under contact of the switchhook and the B line. For party-line working the X subscriber’s bell and condenser is tapped, ofl the B* wire and connected to earth. The Y subscriber’s beU is tapped off the A ‘wire. * lj» ’ * * . IShe receiver is now totally shoyt-circuited, so that the caller ^oes not hear ^;he Ipuzz. Section 6 A. ff. M. CO.’S w ^ COIN-BOX CIRCUIT WITH TONE SiGNAL t v.* ^ ^ the circuits pretlowiy describid, the coin has to be dropped into the chute l^hen tb parties voice i^eard on the line. If tl^erj is any dglay due t» the caUet not realuiiii that the c^ed jiarty has answefed, the latter may fancy it a wrong call and replace tli altemative*circuib (Kg. 21) a spMial tone signal u given to the caller whei j the caLed rectavbr is lifted to rep^. set of r^afs is associated with a trunk line to whi8l a plurality of subscribers’ lih^ has access. Th» circuits are numbered * as follows A : 1. A cmling liile,«by a line sydtcb, extends a trunk line to a connector, in known manner * - one winding qf R' being in circuit. 2. The other winding of R' is in the third oonductor circuit in which cmrent is in the * opposite direction, so that R' does not energise. 3. When the called party answers, the current in theToop is reversed as elsewhere Sgscribed, and, the currents in the two windings now assisting each other, R' Wr^isetf and jpens the B wire towards the connector, and connects t^ie e xiling ^de through ilbl*yB»]S8 md R3' (which energise) to coU C3, and to battef^. 4. A tone signal is induced in circuit 3, which when heard in the receiver is a lio insert a coin. the coin falls through the ohtfte, contact la is opened, and resisfuSce « me circuit. R3 de-enogises, bUt.not R3'. 8. 6. R6 energises. R6 loc^ ci^ouif. pletes the talking cirouit. a, Winding 2 of R' is 8h«^-cirouited, R' detenendses and com- « Section 7 / SUB-STATION GALL METER Instead of the coin-box devtoe previously desorib^, it is sdmethneB preferred to use a meter to register the ntfmber of oaUb. The ^incipal feat^ of sudh^ instaUation is the Modification necessan^ for Party Line Working. For Fit an additional larmlnal (4) as shown In the explanatorv aheteh In dhtted lines and connejst to earth. Transfer the mre fhom the back contact of the switch arm to o terminal 4* '*Pmrty* • t « ‘ t For ' Fh an a&tltlona^ terminal (4) as aboye. Transfer wire to the bef! cot! from terminal 3 to terminal 4, and strap the smich arm to bank contact, Note.- For wiring of Table Set see F/Jj# 23. • * Eio. ^2. —Sub-station Call Mbtbb (A. T. M. ^ Go.). Waix Instruvnnt. e polarised relay^ of the ^$fpe used in^Elg. ^8, which functidhs in a manner similar to that in the coip box. The relay is set wbei^the rgceiver is lifted to make a call, is energised in the opposite direction when the line batte^ is reversed, and te res&re^ to nomal when the meter operates to re^ster a oaU.^ The mfter Is nerm^y shSrt-o&cuited and is energised Wlieii a key is pleased to open the s^ort-oirouit, when ounent over the exoluiiige line oansM it to VQMrd. These may be fitted on diitet lines,'oi*on eaolk of twotstations on\k S-party * oiioiiit.* a Abte,- 7ekph>ne connecting Strip Terminals marked ® Modifications for Part^ Line Working. For Vr Part^» Connect terminal 3 on Bell Set to earth, Instead of to terminal 6 oh Strip * Flex Cord connection^ • • ^ For'' y*Party Fit ^n additional terminal (S) on Bell Set anjf connect to earth. Transfer rfire from bell coH from terminal 4 to terminal fs). Strap terminals 1 and 3 on Bell Set Hote,-* For mm'ng of Wall Set see Fl^,ZZ, • t . Pig. 23. —Sub-station Mbteb (A.TT. M. Co.). T^lb Instbumbnt. The oirouit, when used with a wall instrument, is shown in Fig. 22, and with a table set in Fig. 23. An explanatory diagranf is shown at B in each case. The circuits are numbered^milarly in each jase SuSi are as fcWbws a. When the receiver is4ifted to call, ciprent^s through the receiver