Patent GB-252088-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-02-27
Abstract: 252,088. Western Etectric Co., Ltd., (Western Electric Co., Inc.). Feb. 27, 1925. Semi-automatic exchange systems.-A toll operator's position is provided with master dialling, ringing, splitting and transfer keys which become associated with the cord circuit in use through the listening key, which also controls supervisory lamps. The toll operator sets up a connection to the calling line by means of alternating current impulses, which are repeated to automatic switches bv an A.C. relav associated with the line seized by the operator. Connection is made with the wanted line by the distant toll operator at the appropriate exchange. Outgoing toll call. On receiving a record of the calling subscriber's number and the number required, the toll operator inserts plug 200 of a cord circuit in jack 101 which gives access to a train of automatic distributive selectors by which the calling line may be reached. Lamp 201 lights over the sleeve circuit in series with relay 102. The operator throws listening key 202 to the right, so that relay 207 energizes, while relay 102 remains held over relays 209, 210, and lamp 201 is extinguished. On moving dialling key 211 to the left, relay 106 energizes over the upper line wire and completes a bridge circuit for A.C. relay 108 which includes the dial 228. Relay 108 through relay 111 bridges polarized relay 112 across the outgoing trunk, and dialling by the operator causes impulses to be repeated thereover to make connection with the calling line. If this line is found to be idle, the current is reversed back to energize relay 112 which connects up relay 105 to substitute relay 114 for relay 106. which opens the circuit of A.C. relay 108. Relay 114 does not operate, however on account of series resistance 216. Bridge relav 116 now energizes over the outgoing trunk and reduces the resistance of the sleeve circuit to energize marginal relay 210, which connects up lamp 201 to indicate that the calling line is connected up. To establish connection with the wanted line, the operator restores dialling key 211 and inserts plug 233 at the other end of the cord circuit in jack 300 of an outgoing toll trunk in the required direction. Relay 302 energizes over the sleeve circuit in series with relays 235, 236 and connects up relay 303 which controls busy signals 304, 305, 306. Relay 235 energizes and connects up relay 240. The operator throws ringing key 229 to the right, whereby marginal relay 307 is energized over the upper line wire and connects ringing current to the toll trunk to summon the distant toll operator, who completes the connection and rings the wanted subscriber. The originating operator then throws ringing key 229 to the left, reducing the resistance of the circuit of marginal relay 114, which energizes and connects ringing current to the calling line. When the calling subscriber replies, relay 116 is deprived of current and releases, causing marginal relay 210 to fall back and extinguish lamp 201. The operator restores key 202. Supervisory arrangements. The calling subscriber may signal the toll operator by means of lamp 201 which is controlled by relay 116. No corresponding supervision over the toll trunk is provided. The. operator may monitor when the connection is established by moving listening key 202 to the left, energizing relay 264 and connecting up her set over coil 276. The distant toll operator may call the originating toll operator by sending ringing current over the toll trunk to operate relay 310, which releases relay 312 and so energizes relay 301. The resistance of the sleeve circuit is lowered and lamp 234 lights, while relay 334 locks relay 301. Relay 330 is now connected in series with interrupter 331 and controls high and low resistance circuits for lamp 234 through resistance 333 and relay 334, so that the lamp is caused to flash. On moving listening key 202 to the right, disconnecting lamp 234 and substituting high resistance relays 235, 236. relays 334, 330 fall back and disconnect relay 301. The toll operator's set is normally connected through coils 259, 260 and keys 229, 211, 221 to both plugs 200, 233, but it may be connected to one plug only by moving splitting key 211 to the left or right. Incoming toll call The'distant toll operator sends ringing current over the toll trunk to operate relay 310 as above, but relay 312 now connects up relay 313 (relay 303 being de-energized). which locks under control of relay 303 and connects up busy signals 304, 305, 306 and lamp 316 associated with jack 317 before a toll operator dealing with incoming calls. The call is answered by inserting plug 233 in jack 317, and throwing listening key 202 to the right, whereupon the sleeve circuit is completed over relays 235, 236, 302. Relay 303 energizes and releases relay 313, extinguishing lamp 316. If the attention of a recording operator is necessary, transfer key 272 is moved to the right, and a circuit is closed over the lower line wire to energize relays 315, 314. Relay 315 releases relays 302. 303 and again connects up relay 313, which lights lamp 319 associated with jack 300. To transfer the call to a through operator, key 272 is moved to the left, and the lower line wire circuit includes a resistance 275 so that relay 314 which is marginal does not operate, and lamp 320 associated with jack 321 is lighted.