Patent GB-226467-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04M7/06
Filed: 1923-09-18
Abstract: 226.467. Automatic Telephone Manufacturing Co., Ltd., Mercer, R., and Tench, F. Sept. 18, 1923. Automatic exchange systems comprising offices of 1000 - - 5000 lines or networks of fewer than five offices are provided with selectors which are not operated effiectively by the first digit, which however is first stored on a group of relays to effect wiper selection in the selector or in a subsequent selector or in both. In the 4000-line office shown in Fig. 1 the selector F and connector H5 are double-wiper Strowger switches. The first digit causes the operation of either, neither, or both of two relays, one of which controls wiper selection in the selector F while the other controls the momentary connection of a discriminating potential to a speaking lead to effect wiper selection in the connector. In a 400-line office, Fig. 2, a quadruple-wiper connector is used. 2000-line offices have either the selectors or connectors of standard type. Two forms of switch are described. In one, the selector is released after and in the other is not operated by the first digit. Selector, Fig. 5, in which the wipers return to normal after the first digit. Line relay 204 and release relay 206 pull up and the first digit is repeated to the vertical magnet 211. According to its value (which will be 1, 2, 3 or 4) either, neither, or both of the post springs 215, 218 operate their relays 214, 219 when the series relay 209 falls back. Relay 209 also energizes the release magnet 213 and relay 224 which disconnects the relays 214, 219 and the release magnet and connects up the stepping relay 231. Relays 214, 219 if operated remain locked up, the latter switching over to the alternative wiper set. The selector responds to the next digit to find an idle line in the wanted group in the ordinary way. If the relay 214 is operated, however, the operation of switching relay 235 grounds the lower talking wire. The relapse of release relay 206 shortly afterwards unlocks relay 214 so that the ground connection is only momentary. Selector, Fig. 6, in which the wipers are not moved by the first digit. During the first digit, the series relay 309 is associated with three twostep relays 319, 326, 333, the two former of which correspond to the relays 219, 214, Fig. 5, while the latter has functions analogous to those of relay 224. At the first impulse relay 319 attracts a light armature 320 to connect up its second winding, which, however, is short-circuited until the end of the impulse, whereupon the relay energizes fully, and transfers the impulse circuit to relay 326. A second impulse thus energizes relay 326 which releases relay 319. A third re-energizes relay 319 and a fourth energizes relay 333, which locks up and releases both the others. If the series relay 309 falls back after fewer than four impulses relay 333 energizes fully at once, but relays 319, 326 if operated are held at the back contact 311 and afterwards over contact 335. Owing to the operation of relay 333, the second digit controls the vertical magnet 338 and the change-over of springs 318 arranges for rotary hunting under control of stepping relay 314. Connector. The momentary ground on the talking wire serves to short-circuit a wiper-changing relay 118 in the connector, Fig. 7. which otherwise energizes in series with the line relay and locks up. Specification 227,888 is referred to.