Patent GB-235771-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/62
Filed: 1924-11-05
Abstract: 235,771. Coventry Automatic Telephones, Ltd., and Wilman, C. W. Nov. 5, 1924. Automatic exchange systems.-A single motion connector operated by more than one digit is moved in steps of equal length and has no blank positions. A fourth wiper 25, Fig. 1, co-operates with a row of terminals, three of which are connected to a relay 7, the remainder being connected together and to the stepping magnet 29. The numbering of the corresponding lines is shown below the terminals. The wipers make effective connection with the line on which they come to rest only if, in response to the preceding digit, the fourth wiper paused on one of the terminals connected to relav 7. In a modification, Fig. 2, two associated independently driven switches A, B are provided. Both are operated by the first two digits, after which the extra wiper of one of them is on one of the special terminals and is then restored to normal. The other switch makes connection to the line in response to the third digit. The switches described are of the 25-point back-stroke operated type and in the normal position the wipers rest on a subscriber's line. 25-line connector, Fig. 1. Line relay 1 and release relay 2 pull up and the first digit is repeated to stepping magnet 29 and relay 3 in parallel. If the line is a two-digit line the relapse of relay 3 at the end of the digit energizes relay 7 over terminal 907 or 19 and wiper 25, otherwise relay 7 is not energized until after the second digit, wiper 25 then being on terminal 09. Relay 7 at first attracts only its armature 31 to prepare for its full energization when relay 3 pulls up at the beginning of the final digit, whereupon it starts the busy and ringing machines over wire 56 and connects up the test wiper. Busy test and signal. If the line is busy, relay 4 pulls up over the grounded test terminal, and locks when relay 3 falls back, busy tone being sent from 53. Relay 4 is made sluggish by a short-circuited lower winding. Ringing current and signal. If the line is idle, relay 6 pulls up over its lower winding and the cut-off relay, when relay 3 falls back, grounds the test wiper and locks up by removing a shortcircuit from its upper winding which makes it slow to energize as described in Specification 221,333. Ringing current is sent from 52 over ring-tripping relay 5 and ringing signal leaks back over condenser 28. The energization of relay 5 completes the connection, and busy relay 4 which feeds the called party with talking current pulls up without effect. Release. The release of relay 2 by relay 1 at any stage completes a restoring circuit over 25, 51 (if necessary), 30, 48, 29 and unlocks all operated relays. 50-line connector, Fig. 2. Relays 201 - - 206 operate in the same way as relays 1 - - 6. Release relav 202 on pulling up energizes relays 258, 259 over the fourth wipers 225, 269. The first two digits operate both driving magnets 229, 271. After the wipers leave normal, relay 258 is locked up over wiper 269 and the multipled terminals and relay 259 over wiper 225. At the end of the second digit one of the fourth wipers is resting on one of the special terminals and relay 258 or 259 is therefore released. Assuming relay 258 to fall back, a restoring circuit is made over 269, 263, 270, 257 for the magnet 271 of the switch B. A similar circuit is made for switch A when relay 259 falls back when the connector is released. The energization of relay 203 at the beginning of the third digit energizes relay 279 over the back contacts 264 or 265 of one or other of relays 257, 258 to start the busy and ringing machines and connect up the test wiper of the operative switch in the same way as relay 7, Fig. 1. The remaining operations are the same as in the 25-line connector.