Patent GB-640032-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/60
Filed: 1947-08-07
Abstract: 640,032. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Aug. 7, 1947, No. 21770. Convention date, Dec. 1, 1938. [Class 40 (iv)] In a system in which calls incoming over a junction may be established over automatic switches, pad switching is controlled according to the state of balance of the speech conductors. Thus the speech conductors of a local line are unbalanced and connection thereto switches pads into the junction. The speech conductors of a normal junction are however balanced so that connection thereto effects the cutting out of the pads of the incoming junction. The system is described with reference to two main exchanges in which pad switching in the case of manually established calls is controlled in the first exchange by marginal sleeve relays in the cord circuit and in the second exchange according to the presence of battery or earth on the simplexes of the two circuits connected over the cord. In the second exchange access may be had over the incoming selectors to ring down junctions in which case ringing current is automatically sent for a brief period at the end of which a supervisory signal is given to the operator at the first exchange. Access may also be had to PABX's incorporating line finders in which case a " stop dialling " signal is reverted to the calling operator until the PABX finder has operated. Call from first exchange to second exchange. When the operator at the first exchange, Figs. 1 . . . 6, inserts the answering plug RP into an incoming jack sleeve relay 15 operates followed by 16 and 7 to disconnect the supervisory lamp RL. When the operator inserts plug FP into the outgoing jack J1 of the junction T1, and throws dial key DK to its forward position, 32 operates whereupon 29 and 94 energize over the ring conductor, and 93 and impulse repeating relay 70 follow. Relay 89 operates 86 to put guarding earth on conductors 123, 133 and bring up 129 in the both way junction circuit TWT1, and relay 58 over the sleeve circuit. Relays 64, 75, 81, 65 also operate. In the dial circuit the upper winding of 42 is energized in the sleeve circuit to bring up 43 ... 47, 45 releasing 32 to light the " proceed to dial " lamp DP. When the dial goes off normal 48 releases lowering the resistance of the dialling circuit to bring up 91 and 90 to bring impulse repeating relay 70 under sole control of the dial contacts. Relay 70 then repeats the dialled impulses over the upper leg of junction T1. When the dial key is restored and the last impulse transmitted 48 re-operates and shunts down 94 which is followed by release of 93, 89, 90 and 86. Switching relay 50 operates during the slow release of 89 and'polarized relay 41 then operates over the ring conductor. Relays 29, 91 and 42 . . . 47 then release the first bringing up sleeve relay 25. The cord switching relay 26 and supervising relay 28 then operate to light the supervisory lamp FL. In the second exchange 210 operates to battery over the upper leg of junction T1 bringing up 228, which puts guarding earth on 233 and 256, which puts busy battery on the sleeve of J5 and operates 259 to light busy lamps BL5. Relay 225 operates in series with line relay 301 of the incoming selector TS2 over the simplex. Relay 226 puts holding earth on conductor 243. Selectors TS2 and AS2 are set in the usual way by successive trains of impulses. If the call is routed to an operator's jack via the incoming trunk circuit IT2 relay 371 operates on seizure to light the calling lamp AL7. When the operator inserts the answering plug RP into J7, 394 operates over the sleeve and is followed by 395, 396 which extinguishes AL7 and operates 240 to send battery over the upper wire of junction T1. Relay 110 thereupon operates to bring up trunk supervisory relay 80 in the outgoing junction circuit OT1, to release the cord supervisory relay 28 and extinguish the lamp FL. If the dial key DK is still operated when 80 operates resistance 87 is inserted into the sleeve circuit to reduce the current in the upper winding of 42 which then releases by differential action and relays 43, 46, 44 follow. Relays 42, 44 re-operate but not 46 due to the high sleeve resistance and dial lamp DP originally extinguished by 4 4 remains so. Supervisory and re-ring signals. If AS2 or TS2 encounter all-trunks-busy conditions, an interruptor is connected over 11th-step springs to conductor 244 to pulse relay 240 and relays 110, 80 and 28 repeat the signal to flash the dial lamp DP. If the operator at the first exchange wishes to recall the second exchange operator a single operation of the key RF suffices. Relays 56 and 83 operate and on restoration of the key the circuit for 70 is opened temporarily during the slow release of 83, this signal being repeated in the second exchange by 210 and 371 in the incoming junction circuit IT2. Relay 374 operates momentarily to bring up 382 and connect the interrupter 384 to relay 383 which intermittently disconnects the low resistance relay 382 from the sleeve conductor to flash lamp RL in the cord circuit. When the talk key TK is thrown the increase in the sleeve resistance releases the marginal relay 382 to disconnect 383 from the interrupter. To flash the originating operator the called operator must repeatedly operate her key RK the signal being repeated by the marginal relay 387 and 240 over the junction to relays 110, 80, 28 and lamp FL. When the originating operator disconnects, release of 70 releases 210, 371 and 374, 382 operate, relay 382 being connected to the sleeve to bring up the supervisory lamp RL. Relay 210 releases 225 which releases selectors AS2, TS2 and 396 in the junction circuit IT2 the last putting busy ground on conductor 363 until disconnection of the operator's cord C2 releases 395. If the answering operator disconnects first 394, 395 release 240 and 80 in the originating exchange to bring up the supervisory lamp FL therein. Call from operator of second exchange to operator of first exchange. When the operator plugs FP into J5 and operates the talk key TK relays 410 and 420 operate whereupon 421 and 422 and 254 operate in the sleeve circuit, 422 lighting the lamp FL and bringing up 423. Operation of the dial key DK brings up 424 ... 428 the last de-energizing the slow releasing relay 426. In the trunk circuit relay 267 brings up 257 which lights the busy lamp BL5. Guarding earth on conductors 223, 233 is supplied by relays 257 and 264. Relays 269, 276, 270 are then energized, the last connecting battery over the trunk as a seizing signal to the distant exchange. Relay 229 operates to ground on 223. When slow to operate relay 269 pulls up 278 and 429 operate in series over the tip of the jack. In the dial circuit 431 closes a circuit for 432 over the dial contacts D2 and the ring conductor, and 427, 429 release. In the trunk circuit 278 operates 279 and releases 276, thereby putting relay 270 (upper winding) under control of the dial, whose impulses are thus repeated to line. At the called exchange 110 operates to incoming battery over the junction T1, and 128 puts guarding earth on conductors 123, 133. Relay 125 operates over the simplex circuit in series with the line relay of the incoming selector TS1 and 126 follows to apply holding ground to conductor 143. Received impulses then set selectors TS1, AS1 in turn and when the call is answered by an operator, or, after further trains of impulses, by an automatic subscriber, ground on 144 operates 140 which sends battery over the junction as an answering signal thereby operating 210. Relay 255 follows opening the circuit through the low resistance winding of 254, the consequent increase in sleeve resistance extinguishing the cord supervisory lamp FL. On release of the dial and talking circuits by restoration of keys DK, TK, relay 278 releases to operate switching relay 266. If the operator re-operates her dial key after 266 is operated relays 410, 420 ... 428 operate as before and 429 operates in series (over the tip conductor) with 203 and 263 which latter. is marginal and does not operate. Relays 431, 432 operate and 427 releases. Relay 277 operates over the ring conductor and releases 266 whereupon 278 operates to put 270 under control of the dial contacts. Release on withdrawal of FP is initiated by 254, 270 extending earth over the junction T1 which releases 110, 125, 126 and 128 to release selectors TS1, AS1. The calling operator may re-ring the called operator by a single operation of RK to bring up marginal relay 263 over the tip conductor and 258 follows. On restoration of RK, 270 is momentarily released to send a recall signal. Re-ring in the reverse direction is effected by release of 140 in the called exchange to cause release of 210 and 255 and lighting of the lamp FL in the calling exchange. Ring down junctions. If the selector AS2 is set to a level giving access to ring down junctions the left hand contacts of normal post springs 358 are operated (the left and right hand springs are operated independently at different levels) to operate relay 336 of the interswitch circuit IST2, whereupon 325 operates over the simplex circuit followed by 326 which operates 327 of a common timing circuit. When ground from interrupter A operates 329 ringing tone from source 331 is transmitted to the calling operator until, two seconds later, 328 is operated by interrupter B and releases 329 to cut-off the ringing tone and to ground conductor 324 thereby operating 240 to send out battery over the trunk to extinguish the calling operator's supervisory lamp. In the ring- down junction circuit RD1, 508 operates a seizure, connecting battery to the sleeves of jacks J9,. 10 to mark them busy. Relay 529, 523 follow and operate busy indicator BS10. While 329 and 336 of IST2 are operated, 592 connects ringing current to the junction RDL. Ringing recall signals arriving over RDL operate 590, to release the normally operated relay 591, thereby bringing up 327