Patent GB-232726-A (GB)
Abstract: 232,726. Western Electric Co., Ltd., (Deakin, G.). Feb. 12, 1924. Semi-automatic exchange systems.-A call to a distant automatic exchange is extended by a manual exchange operator by plugging into an idle jack J corresponding to the exchange, whereupon a link circuit connects itself by means of switches JF, SF to the jack J and to an idle register-controller which is set to the wanted number by the operator's keyset OKS by means of code impulses. An idle trunk to the automatic exchange is then selected by a switch TF and the switches thereat are controlled by means of revertive impulses by the register-controller. Connection of keyset, Fig. 2, to register-controller, Fig. 4. Upon plugging into an idle jack J, test terminal 204 of the switch JF is grounded and a common start relay 208 energizes and connects up through relay 239, the magnets 210 of all the switches JF having access to the jacks J corresponding to the desired exchange. The test relay 211 of the first switch to find the jack J energizes over test terminal 204 and closes a shunt circuit for itself in series with relay 216. the resistance of which is now enough to mark the jack J busy, and high enough to release relay 208 in parallel therewith to bring the remaining switches to rest. Relay 206 connects up the magnet 217 of the switch SF and test relay 218 energizes when an idle register-controller is found over test wiper 222, relay 402 and contact 401 of the sequence switch 400, and closes a shunt circuit for itself in series with switching relay 223. Relay 402 energizes and advances the sequence switch to the 3rd position and relay 405 energizes in series with relay 224 over wiper 221, and locks relay 402. Relay 228 energizes over wire 226 and wipers 202, 220 and lights lamp 229 to indicate that the keyset is ready for operation. Registration of wanted number. Relays 406, 407, 408 connected over wipers 201, 219 to wire 225, and relays 410, 411 connected over wipers 202, 220 to wire 226 are selectively operated by strong or weak positive or negative battery connected to those wires by the keys 1 - - 10. Relay 227 energizes upon depression of any key and lights lamp 235. Assuming key 2 to be operated, strong negative battery on wire 226 energizes both relays 410, 411, and weak negative battery on wire 225 energizes relay 407 only, relay 406 requiring greater current, and relay 408 being polarized requiring positive current. Relay 413 energizes in the 3rd position of the sequence switch and relays 410, 411, 407 connect up marking relays 416, 417, 433. The contacts of the upper set of marking relays are connected as indicated to the terminals of the registers 1DS, 3DS, the relays being operated in groups to remove ground from particular terminals. The lower set of marking relays are similarly associated with the registers 2DS, 4DS. Magnet 426 energizes over contact 455 and advances the register 1DS to the 2nd terminal which corresponds to marking relays 416 417, 433. Meanwhile, slow release relay 413 falls back and the sequence switch moves into the 4th position, in which the lower set of marking relays are. connected up. The registers 2DS, 3DS, 4DS are accordingly set in the 4th, 5th and 6th sequence switch positions. Selection of idle trunk, Fig. 3, and control of switches. In the 7th position of the sequence switch 400, the high-resistance winding of relay 405 is short circuited, so that relay 224 in series therewith energizes, connecting up the magnet 240 of the switch TF, and causing lamp 229 to flash by connecting interrupter 454 to wire 226. Test relay 241 energizes when an idle trunk is found, and grounds test wiper 245 over itself and relay 246, which energizes and locks in series with relays 206, 300 over wipers 214, 244. Relay 206 releases relays 211, 216 and relay 300 releases test relay 241 and energizes relay 301. The fundamental circuit is now completed over stepping relay 304, wire 307, wipers 243, 220, stepping relay 437, wipers 219. 242 and wire 306, and is controlled by interrupter 305, so that relay 437 is intermittently short-circuited, and controls a counting chain of the usual type in which two relays correspond to each impulse, the relays being connected to the right-hand banks of the registers. The last relay 444 connects up relay 438 to open the fundamental circuit and advance the sequence switch to the next position to transmit the next digit. When the last digit has been sent, the sequence switch advances to normal, and relays 405, 402 fall back and the registers are restored to normal. Relays 218, 223, 224 relapse, and the last completes the talking circuit, relay 246 being the only relay in the link circuit energized during conversation. When the operator removes her plug, relays 206, 246, 300 fall back, but the trunk tests busy until the group selector at the distant exchange returns to normal and grounds wire 306, whereupon relay 302 energizes and unlocks relay 301.