Patent GB-223030-A (GB)
Title: Improvements in or relating to automatic or semi automatic telephone systems
IPC: H04Q3/00
Filed: 1923-09-18
Abstract: 223,030. Automatic Telephone Manufacturing Co., Ltd., Mercer, R., and Tench, F. Sept. 18, 1923. Automatic exchange systems.-A code-translating register-controller of the kind described in Specification 194,580 is modified to translate the numerical part of the number when it routes a call to an office using Strowger switches with two sets of wipers. In the case of calls for a 10000- line office of this kind, first digits of 1 - - 5 are transmitted as dialled, but 6 is sent as one impulse, 7 as two, and so on. The first selectors therefore never move more than five steps but have two sets of wipers and hunt simultaneously through twenty trunks. Second selectors are standard but connectors are large capacity and before sending the tens digit, the register-controller, if the first digit was translated, sends a " switching current " to control the change-over from one to the other set of wipers. The switching current is sent by momentarily grounding the trunk. 4000-line offices have a single group selector stage, the selectors having two sets of wipers and giving access to different groups of largecapacity connectors over corresponding levels in their two banks. In this case the register-controller suppresses the thousands digit but according to its value sends a " switching current " before either, neither or both of the (untranslated) hundreds and tens digits. Normal operation. This proceeds exactly as in Specification 194,580. The switch F operating like a group selector selects an idle register controller, Figs. 2 - - 5, of the proper group in response to the first exchange digit and the other two digits lift and rotate the exchange register J. The numerical digits are stored on the digit registers M<1> - - M<4>. As soon as the exchange letters have been dialled the routing number or exchange code is transmitted followed by the un-translated numerical digits. Impulses are sent over the wires 100, 101 by relay 107 operating under control of the sending switch S, the sequence switch S' taking a step after each digit sent. In case there are only three digits in the exchange code the switch S' is driven through its fourth position. Transmission of numerical code,-first digit translated. In the case of certain exchanges, e.g. when the register J is rotated to the, fourth terminal in the level shown, relay 502, Fig. 4, energizes in the first position of switch S<1> over 306, 411, 404, 400, 219, locks up, connects wiper 306 to the proper bus-bar and changes the connections of the upper bank of the thousands register M<1> so that the 1st and 6th, 2nd and 7th, &c. terminals are connected together. The thousands digit transmitted therefore has always one of the values 1 - - 5, but if the register M<1> is set to a higher number than 5 a circuit is completed over its lower wiper to ground the trunk when the switch S<1> moves on after the transmission of the hundreds digit (404, 417, 509, 401, 206, 455, 123). This circuit is maintained by the off-normal relay 106 when relay 105 relapses shortly after the hundreds digit. Operation of repeater and of the distant exchange selectors. When the repeater R, Fig. 6, is seized, relays 600, 601 energize in series followed by release relay 604, and line relay 620 in selector E<2> energizes over shunt field relay 610, followed by relay 622. Relay 610 does not energize. Impulses from the register controller are repeated to vertical magnet 650, and shunt field relay 629 energizes over off normal contacts 627, 635, and interrupter contact of rotary magnet 633. The energization of the rotary magnet on the relapse of series relay 625 releases relay 629, which reenergizes only if both trunks are busy and causes another rotary step. As soon as an idle trunk is found one of the switching relays 636, 637 pulls up and extends the connection. The second selector is of ordinary type. The connector H is standard except for the provision of relay 662 for changing to the alternative wiper set. In the absence of a discriminating impulse, line relay 653 energizes in series with relay 662, which then locks up. If, however, after the hundreds digit, the register controller sends a discriminating impulse as described above, relay 601 in the repeater is short-circuited and connects ground over the lower talking wire to short-circuit relay 662. The energization of release relay 656 opens the circuit of relay 662 so that it cannot energize when, later, relay 601 re-energizes. The operation of back-bridge relay 671 energizes relay 610 at the repeater which reverses the current in the calling loop. Transmission of numerical code-1st digit suppressed. In the case of a 4000-line exchange such as that selected when the exchange register is stepped to the sixth terminals in the level shown, relay 500 energizes in the first position of the sequence switch S<1> over 306, 411, 400. Relay 500 connects wiper 306 to the proper bus bar, locks up and energizes relay 501. Relay 501 grounds wire 449 to cause the sequence switch S<1> to be driven through its fifth position so that no thousands digit is transmitter, and with relay 500 alters the connections of both banks of the thousands register. According to the setting of the thousands register, a discriminating impulse is sent out before either, neither, or both of the hundreds and tens digits. If it is set to 1 an impulse is sent before the hundreds digit over 404, 416, 508, 415, 244, 451, 503, 455, and before the tens digit over 404, 417, 510, 469, 206, 455. If to 2, the impulse is sent only before the hundreds digit, if 3 only before the tens, if 4 no impulse is sent. The group selectors at the exchange are provided with a relay, the function and control of which are the same as those of relay 662 in the connector H, Fig. 6. Special provisions. Connections with a complaint or information operator, or in response to a dialling of a non-existent number, are provided for as in Specification 194,580, and the arrangements for releasing the register controller if dialling is interrupted is the same also. The provision for releasing the register controller in case the exchange code has been sent before the dialling of the number is, however, omitted. This could be included but would then have to be disabled by the operation of relays 500 - - 502. Interexchange working. Large capacity switches can be used in selecting the exchange, e.g. by giving two exchanges the same exchange code and discriminating by means of an additional impulse. Grading. The system described for the 10,000- line exchange may be modified in the following manner. The thousands digit is transmitted without translation and the selector E<2> has only one wiper set. The first five terminals in any level of the selector E<2> lead to ordinary switches but the last five in level 1 are multipled to the last five in level 6 and so on and give access over a second selector to connectors of the kind shown in Fig. 6. The discriminating arrangements are the same as those described above and do no harm to the ordinary connectors. The same idea can be applied to a two-wiper group selector arranged for simultaneous hunting so as to give groups of trunks of any desired size.