Patent GB-264593-A (GB)
Title: Improvements in telephone systems
IPC: H04M3/40
Filed: 1925-10-21
Abstract: 264,593. Western Electric Co., Ltd., (Bell Telephone Laboratories, Inc.). Oct. 21, 1925. Manual exchange systems; two-way repeating systems.-In a system in which an operator sets up connections over a cord circuit, if both the incoming and outgoing lines are toll lines, a twoway telephonic repeater is automatically selected and associated with the lines. This is initiated by relays 223, 225 in the cord circuit which are controlled by marginal relays 222, 217 in the sleeve circuits. In the case of ordinary lines, the sleeve circuit is of low resistance, and the corresponding marginal relay prevents the energization of the relay 223 or 225. During conversation, the talking circuit is dissociated from the cord circuit, but bridge relays 432, 433 in the repeater control a supervisory lamp 208, and the operator is able to transfer back the lines to the cord circuit for supervision. The arrangement may be modified to connect up a repeater if either line is a toll line. and the alternative sleeve circuit connections of the lines may be under the control of the operator. The repeater (Fig. 4) is of the type described in Specification 215,323. Seizure of an idle repeater. When the operator plugs into the jack 100 of an incoming toll line 101, 102, relays 221, 114 energize in the sleeve circuit, marginal relay 222 being inoperative. Relay 114 causes relays 115, 116, 112 to energize in turn, and the last relay extinguishes the calling lamp 113. The sleeve circuit is transferred to the low-resistance right windings of relays 114, 115, marking the calling line busy, and allowing marginal relay 222 to operate, but without effect at this stage. In the cord circuit, relay 223 energizes and locks. Assuming the desired line 301, 302 is a toll line, when the operator plugs into the jack 300, relays 315, 218, 239 energize in the sleeve circuit, marginal relay 217 being inoperative. Relays 316, 317, 311 energize and the sleeve cricuit is transferred to the low-resistance left windings of relays 315, 316, marking the line busy and allowing marginal relay 217 to operate without effect. Relay 225 energizes and locks, and relay 212 energizes and bridges relay 211 across the line through key 204 to give supervision. A starting circuit is closed over front contacts of relays 223, 225 for magnet 250 of the lock-out switch 249, which is advanced until the cord circuit in use is reached, battery being supplied over wiper 251 from front contacts of relays like 234 in the case of cord circuits which are already associated with repeaters, and from back contacts of relays like 223, 225 in the case of other cord circuits. Relay 230 energizes, being no longer short-circuited, locks, connects up relays 229, 228, and shunts magnet 250 to prevent operation by other cord circuits until a repeater has been selected. The switch 249 serves a group of cord circuits and serves to isolate the repeater selecting apparatus. Relay 228 connects ground over wiper 252 to energize relay 231, which connects up magnet 240 and series relay 232 of the switch 259 which is individual to the cord circuit to hunt for an idle repeater. Sluggish relay 233 then energizes, locks and marks the repeater busy by grounding wiper 241. Relay 127 also energizes, disconnects relay 231 and connects up relay 410 which controls the filament current of the valves 401,451. The circuit of relay 231 is grounded at back contacts of all the relays like 127, so that, if all the repeaters are in use, this relay cannot energize. Connection of repeater to incoming and outgoing lines. Relays 224, 219 energize in parallel with the locking circuit of relay 233, and the latter adds resistance 256 to the sleeve circuit to release relay 315, whereby relay 323 energizes and connects up magnet 340 and series relay 324 of the switch 349, which is individual to the line and hunts for an idle outlet to a switch, 359, the terminals of which lead alternately to the two ends of the repeaters. Since plug 200 is always used for the incoming line and plug 201 for the outgoing line, the lines are always connected to the proper ends of the repeaters. Sluggish relay 825 energizes when series relay 324 finally falls back and grounds wiper 341. Relay 327 energizes and connects A.C. source 371 to wipers 343 - 346. Relay 320 energizes and connects up magnet 350 and series relay 321 to advance the switch 359 into engagement with the selected repeater, which is marked by absence of ground over wiper 350 due to energization of relay 127. Sluggish relay 322 pulls up and connects ground to wiper 351 to energize relays 130, 220 (over wiper 246), 329. A.C. is now connected over the wipers of the switches 349, 359 to the repeater for the purpose of reducing resistance at the switch terminals due to film, oxidation or dirt, and is subsequently disconnected by relay 326. Relay 130 removes ground from a terminal of the switch 159 to mark the selected repeater. Relay 220 adds resistance 225 to the sleeve circuit to release relay 114, which connects up relay 122, and the switches 149, 159, which are similar to the switches 349, 359, are operated to make connection to the selected repeater, and relay 133 energizes to connect up A.C. from source 135 to reduce resistance at the switch terminals. Relay 234 energizes over wiper 151, 244 in parallel with relay 216, locks and connects battery over wiper 251 to release relay 230 by short-circuiting, thereby disconnecting relays 228, 229 and rendering the lock-out apparatus again available. Relay 128 also operates and energizes relay 129 through the medium of sluggish relays 131, 132. Relay 129 locks and extends ground from wiper 245 to energize relays 119 (over wipers 152, 142), 126 and 326 (over wipers 352, 342). Relay 326 locks, disconnects relay 327 to cut off A.C. and establishes a balancing bridge across the outgoing line. Relay 327 upon release connects up relay 328 which transfers the outgoing line 301, 302 from the jack 300 to the repeater and connects in the usual balancing network 370. Relay 119 acts in a similar manner to disconnect A.C. and control relay 117 to connect the incoming line 101, 102 to the repeater. Relay 126 removes short circuits from the input transformers of the repeater. Supervision. Relays 432, 433, which are responsive to ringing current, are bridged across the incoming and outgoing lines and supply energizing ground over wiper 244 to relay 213, which controls a supervisory lamp 208 through relay 214. If this lamp becomes lighted, the operator may, by depressing a key, energize relay 328, which disconnects ground from wiper 245, so that relays 117, 328 fall back and associate the lines with the cord cricuit for supervision. By means of key 205, the operator may connect in her set 207 over wipers 242, 243 for monitoring purposes. Connections not requiring repeaters. An ordinary short line has its sleeve circuit leading direct to relay 112 over wire 109, relays 114, 115, 116 being omitted. On plugging into the jack 100 of such a line, marginal relay 222 energizes at once and opens the energizing circuit of relay 223. Since the seizure of a repeater depends on the energization of both relays 223, 225, a repeater is only connected up if both the lines are toll lines.