Patent GB-193307-A (GB)
Abstract: 193,307. Coventry Automatic Telephones, Ltd., (Arter, R. C.). March 28, 1922. Automatic exchange systems.-A calling line is connected to an idle line of a desired numerical group by two groups of switching relays, one group of relays comprising as many relays as there are numerical groups, and the other group comprising as many relays as there are lines in a numerical group. A selector trunk A is connected to an idle connector trunk in the desired group by energizing one of the relays 190, 190<a> according to the hundreds digit of the wanted line; which relay 190, say, connects the test wires of all the trunks in that group to the second group of relays 180, 180<a>, 180<b>, &c., the relay 180, say, corresponding to the first idle trunk being energized to connect the trunk A to the set of contacts of relay 190 connected to the idle trunk. Relay sets based on the tens and units principle act to connect a calling line to an idle selector trunk, and to make connection with a called line, the tens and units relays in the latter case being selected by a temporarily used relav selector. Connection of calling line to idle selector trunk. When a subscriber removes his receiver, his line relay 101 energizes a relay 115 of the first idle selector trunk A. The relay 115 connects the tens and units relays such as 110 120 of this trunk to the contacts of the line relays so that one of the relays 110 and one of the relays 120 is energized to connect the calling line to the trunk A. The cut-off relay 102 then energizes in series with a relay 104, which completes holding-circuits for relays 110, 120, disconnects relay 115, and extends the starting circuit to the relay 115<b> of the next selector trunk. Relays 106, 107 energize over the calling line and complete circuits for relays 105, 151, 152, 162. Relay 108 of the impulse-responder R energizes over the contacts of relays 107, 162, 104. Connection to idle trunk in desired group. Under control of relay 107, the impulse-responder R operates in known manner to prepare a circuit for one of the switching-relays 190, 190<a>, &c. At the first impulse, relay 106 opens the circuit of relay 151, thus energizing the self-locking relay 154. At the end of the impulses relay 151, which is mechanically made slow to energize, energizes relay 153 which closes a circuit over the contact of the responder relay 132<1>, say, for the switching-relay 190, which locks up dependent on relay 104. The relay 190 connects all the relays 180, 180<a>, 180<b> over the contacts of relay 162 to the test wires 172, 175, &c. of the trunks in the selected group. If the first trunk is idle, the relay 180 energizes over test wire 172 and relay 201 which does not energize. Relay 180 locks up over a relay 161, which causes 'the de-energization of relays 106, 107, 162, 152, 153, 154, 132, 132<1>, and connects battery direct to the test wire 172 to energize relay 201, which locks up over its high-resistance winding so as to mark the trunk busy and grounds the relay 201<a> of the next trunk so as to make this available for the next call. If the first trunk had been busy and the second free, the relay 180<a> would have energized over test wire 175, relay 201<a>, and a contact of relay 201 of the first trunk. Relay 106 again energizes over the calling line and relay 202, which connects earth over the contacts of relays 201, 204, 209, 202, 203 to relays 320, 330, Fig. 3, of the impulse responder. Relay 321 is energized by relay 320 and locks up. Relays 321, 322, 323 control tens selection, relays 324, 325 control units selection and relays 326, 327 control selection on a party line. Tens selection. Under control of relay 202 and the tens impulses, the relay chain S prepares a circuit for a tens switching relay, such as 290. At the first impulse relay 320 energizes relay 322. and when the impulses cease relay 320 energizes relay 323 which causes a relay 295, Fig. 2, to connect up all the tens relays to the marking wires so that the desired tens relay 290 is energized over the contacts of the selected relay 303'. The relay 290 locks up dependent on relay 201, and energizes a relay 340 to restore the relay chain. Units selection. The relay chain is again operated by the units impulses to prepare a circuit for a units relay, such as 280. At the first impulse relay 324 energizes, and when the impulses cease relav 320 energizes relay 325 which causes a relay 285 to connect all the units relays to the marking wires so that the desired units relay 280 is energized over the contact of the selected relay 301'. Relay 280 locks up dependent on relay 201 and energizes relay 340 to restore the relay chain. Busy test and signal. If the wanted line is busy, the test relay 215 and relay 208 do not energize, and when the relay 209 is subsequently energized by one of the party-line ringing relays 211 - - 214, the busy interrupter 210 is connected to the calling trunk. The caller may hold the connection until the wanted line becomes free or may restore the apparatus by replacing his receiver. Party-line ringing current. If the wanted line is free, relays 215, 208 energize, and the ringing relay 206 is intermittently energized to connect one of the ringing-generators 16, 30, 50, 66 to the a- or b-lead according to the number of the wanted station on the line. The relav chain S is again operated by the final set of impulses to prepare a circuit for one of the relays 211 - - 214. At the first impulse, relay 320 energizes relay 326, and when the impulses cease relay 320 energizes relay 326, which causes a relay 275 to connect the marking wires to the four relays 211 - - 214 and also to connect a reversing relay 207 to the contact of a relay 350, which is energized only if the digit dialled is 6, 7, 8, 9, or 0. Thus, according to the final digit, one of the relays 211 - - 214, or one of these relays and the relay 207, is energized to connect one of the generators 16, 30, 50, 66 to the a- or blead of the wanted line. When the subscriber replies, a relay 204 opens the holding-circuit of the relay 211 - - 214, thereby de-energizing relays 209, 206 to complete the speaking circuit. Release. When the calling subscriber replaces his receiver, relays 202, 106, 105, 104, 102 deenergize, relay 104 opening the holding-circuits of the switching-relays 110, 120, 180, 190. To prevent the seizure of the connector trunk until the associated apparatus is restored, and the called subscriber has replaced his receiver, relay 201 is made dependent upon relay 203 which is controlled by the relay.204. The connector circuits are not restored until both subscribers have replaced their receivers. Specification 27139/08 is referred to.