Patent GB-328611-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1929-01-31
Abstract: 328,611. Standard Telephones &. Cables, Ltd., Baker, J. H. E., and Haigh, L. B. Jan. 31, 1929. Automatic and semiautomatic exchange systems.-The line relav of a calling party operates and locks as a result of a momentary looping of the line so that, if the automatic equipment for extending the call is busy, the calling party replaces his receiver and awaits a ringing signal automatically connected to his line, when the equipment becomes free. The invention is described in connection with a small rural exchange in which the calling impulse from subscriber S, Fig. 1, completes a starting circuit extending from line circuit LC through common control equipment R to an idle local link circuit LLC whereupon finder FA is stepped on to the calling line which is then rung. The dialled impulses are repeated at R to a marking switch LS, and connector C of the link circuit hunts for the marked line. For outgoing calls to an operator or to another rural exchange, the equipment R takes into use a link circuit LLC and finder FA is set as before, but in response to particular first digits, seizes an idle junction circuit BJC associated with a two-way junction BJ, whereupon finder FB is stepped on to terminals corresponding to those of FA and the link circuit LLC is released. For incoming calls, the junction circuit is disconnected from the junction, a local link circuit is seized, and finder FA hunts for the calling junction, the marker LS being set by incoming impulses and the connection completed as for a. local call. The marker comprises a singlemotion switch moved one step per impulse for the first digit and two steps per impulse for the second digit, twenty subscribers being provided for. Local call. When a call is initiated, line relay 1 operates, locks to the b wire, connects the windings of 2 in parallel to the test terminal in FA, and grounds the start lead a which is extended over 9(7), Fig. 4, if the register is idle, and lead e to operate relay 6, Fig. 3, of the first idle link circuit. Relay 6 connects up the leads to the register, whereupon relay 9 pulls up, opens the operating circuit of 6 but holds this relay over 9(1), h. The magnet 7 of FA is operated over lead f and when the calling line is reached, test relay 11 (lower) operates over c in series with relay 2 which releases the line relay and locks over its high-resistance upper winding to busy the line. Relay 11 locks up, opens the driving circuit, and completes the ringing circuit from relay 13 and 11(1) over leads i, b. When the calling party responds, relay 13 pulls up and connects tone from DT over condenser C and battery over relay 12 to the b wire. Relay 12 operates over the calling loop to ground at 11 (1) and slow. to-release relay 21 pulls up. The local subscribers are numbered 20 - - 39. The dialled impulses are repeated by 12 to magnet 19 and relay 20 in parallel, relay 13 being released by 20. If the first digit is 2, the relapse of 20 at the end of the train energizes 16 over wiper D and, owing to commoning in the K bank, magnet 19 operates for the second digit during each relapse and operation of 12 so that switch LS takes two steps per impulse. Slow-to-operate relay 23 pulls up after 16 has locked up. If the first digit is 3, relay 16 remains unoperated but the switch takes two steps per impulse commencing at terminal 3. During the second train, relay 30 pulls up over 23(1), 20(1), 21(5), relay 23 being very slow to release so that it does not fall back when 20 is operated, but is locked over 30(1). In the interval between the release of 20 and 30 at the end of the train, the called line is tested over 20(3), 30(2), and relay 22 (upper) which, if the wanted line is idle, operates in series with the cut-off relay. After the relapse of 30, relay 23 holds over its original circuit. Relay 22 completes a circuit over lead m for magnet 8, Fig. 3, of the connector C the terminals in bank M of which are connected to those of bank M of LS. When the marked terminals are reached, relay 15, Fig. 4, energizes over the banks M, lead n to ground at 22(2), opens the driving circuit, and completes the ringing circuit from relay 13 and 9(2) over leads g,. l, ringing tone being sent back to the calling party over condenser C. When the called party replies, relay 13 transfers the ground from 9(2) to lead j to operate relay 4, Fig. 3, which completes the connections on both called and calling sides of the link circuit. The feed relays 3, 5 both complete holding circuits for relay 4 so as to give last party release, and relay 4 connects ground to the respective test wipers of C and FA to hold the cut-off relays 2, and transfers the start lead e over L to the next idle link circuit. Relay 6 falls back to disconnect the register, whereupon the operated relays therein fall back and a homing circuit for switch LS is completed. Call to operator over junction BJ. The register and link circuit are picked up as before, and FA finds the calling line, but in this case the first digit is 0 so that relay 17 pulls up over wiper D of LS and holds relay 6, Fig. 3, to ground at 9(2) instead of 9(1). The circuit of relay 26, Fig. 5, of the first idle junction circuit is now completed over lead u, and relay 10 in the register operates over q, 26(5). Relays 26, 17 complete a circuit for magnet 27 of the finder FB the banks of which are multipled to those of FA so that when FB reaches the calling line, ground from 17(1) over lead o is connected over wipers J of FB, FA and lead k to relay 15 which connects ground from 9 (2) over lead r to relay 28 of the junction circuit and releases relay 6 in the link circuit to disconnect the register therefrom. Relay 10 in the register holds over lead q but other operated relays therein fall back as before. Relay 28 connects feed relay 24 to the calling line, and relay 24 holds 28 and connects battery over 25 (lower) to the junction b wire to signal the operator. Relay 6 relapses and disconnects the register. When the operator plugs in, relay 25 energizes and connects up a further holding ground for relay 28 to give operator hold. Calls to other rural exchangee. A first digit other than 2, 3, 0 may be used to gain access to other small exchanges in a similar manner to that described in the preceding paragraphs, one or more relays functioning similarly to 17 being added to the register. Incoming calls. Battery over the junction a wire operates relay 25 (upper) which completes a circuit from 28(6) over leads t, e for relay 6 in a local link circuit. The finder FA searches for the calling junction, and when this is found relay 29, Fig. 5, operates in series with relay 11, Fig. 4. Relay 29 disconnects the junction circuit from the junction, and dialling tone is sent back over the junction, the remaining operations of setting the marking switch LS and of the connector C taking place as described for a local call. Busy and standstill signals and release; incorrect dialling. If the calling or called parties do not respond to the ringing signals, or if dialling is delayed, the register is held for an abnormal time and thermal device 18 operates relay 14. If a wrong first digit (1 or 4- - 9 as shown) is dialled, relay 14 energizes over wiper D and locks to 9(6). Relay 14 completes a driving circuit for magnet 8 of the connector C which is stepped on until wiper M reaches a contact connected to lead w, Fig. 4, when relay 15 operates over leads w, n, opens the drive, and connects ground from 9(2) over lead j to operate relay 4 which switches through as previously described. The connector C was stopped on line terminals connected to a tone signalling device, so that the calling party on hearing the tone replaces his receiver. Relay 4 releases the register as before.