Patent GB-311666-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/42
Filed: 1928-01-11
Abstract: 311,666. Siemens Bros. & Co., Ltd., Peters, C. L., and Christian, D. A. Jan. 11, 1928. Automatic exchange party line and metering systems. - In a two-digit system using finderconnector links controlled by a register-controller, the latter, which comprises means for testing and ringing the wanted line, for selecting a particular ringing code for party line and for metering calls, selects an idle link by means of a hunting switch which operates subsequently as a sequence switch, each link being represented by 3 adjacent terminals in its banks. The connectors, which also operate to select idle junctions to a main office, are single motion step-by-step switches and are controlled by a two motion register which after being set moves automatically to a limiting position determined by the number of subscribers on the office, the rotary magnet of the register and the magnet of the connector mutually controlling one another so that the latter takes a corresponding number of steps. In the case of main office calls, this mutual control begins after the register has received a single digit and stops when an idle junction is found, the same test relay being used as for calls to subscribers. The connecting circuit is released when either party clears, the other party being unable to make a further call before clearing. Permanent calls for example due to faults or to reverting party line calls which do not use the register controller result in the forcible freeing of the line from the register controller and link, the line being busied until the loop is broken. Selecting register controller. Assuming the allotting relays A - - C are in the position shown, the register controller on OSW1 having been used last, line relay L energizes A which locks and energizes C which removes a short circuit to allow B to pull up in series with A and disconnect C (1). If the register controller on OSW is available, C remains held over C (2) and the starting relay ST, Fig. 3. Otherwise, C falls and energizes reverse winding 2 of A which re-energizes C and releases B. B cuts off C (1) but C remains held over C (2) and the starting relay in the other register controller if it is available. When the calling line is found, the relapse of L releases C, but if the register controller on OSW is being used, A and B remain locked up and the initiation of a new call de-energizes them to cause the register controller on OSW1 to be tested first. Selecting link and operating call finder. ' S'T starts the interrupter and ringing motors and connects an interrupter to DFM which drives DF until wiper 1 finds battery, whereupon T connects an interrupter over wiper 5 to magnet DSM of the finder DS in the selected link. TC pulls up over the calling cut-off relay CO, locks up in series with T and connects B in parallel with itself. The calling loop is thus extended over 3<1>, 4<1> and b<2>, b3 to impulse relay A which energizes release relay V which holds B to za2. B also energizes DFM, the circuit being broken shortly afterwards to allow the wipers to move by the relapse of T which follows that of ST when the line relay is cut off. V also energizes dialling relay D which connects up dialling tone and opens the starting circuit to prevent interference by other calls. Registering number. 'The digits are repeated by A to the magnets VM, RM of the register RS. At the end of the first digit D energizes G to switch in RM and then pulls up again to hold G until the end of the digit. Selecting line. At the end of the 2nd digit, D energizes E which energizes RM over e2, 7<2>, dcm. RM on pulling up energizes the driving magnet DCM of the connector over 6<2>, e<1>, rm. DCM releases RM which releases DCM and then pulls up again re-energizing it and so on. When the register reaches the end of the level, wiper X energizes PS which disconnects RM, locks itself in series with PT and energizes the rotary release magnet RZM. On the restoration of springs w2, PS falls but PT holds. Before the relapse of PS, D pulls up over w1 to send an impulse to VM. On the relapse of PS, D falls; re-energizes RM and energizes G which releases PT. At the first step G falls again. When the register reaches a limiting position determined bv, the number of individual lines in the connector bank, RM holds momentarily over Q (1), X, and Q inserts its winding (2) to release RM and connects QA to DCM. On the relapse of RM DCM falls to advance the connector to the wanted line and QA pulls up. Busy test and signal; control of ringing current. QA completes the test circuit C<2>, P, qa1, c4. If the line is busy, the relapse of E, which is cut off by Q connects up busy tone BSW. If it is idle, P pulls up in series with the wanted cut-off relay, busies the line and energizes DFM, this circuit being broken shortly afterwards by the relapse of E to cause DF to move to the ringing position. Ringing current goes out over 7<3> and returns over 6<3> and ring trip relay TR (1). Completing connection and releasing register controller. When the subscriber replies, TR locks up and energizes the switch through relay LV in the link to complete the connection, release TC and busy both lines independently of the register controller. In the register controller, A, V, B, TR,SA fall back, release magnet ZM is operated and finally Q falls back. Release by either party. The relapse of either of the supervisory relays LA, LY releases LV which releases' the other and sends the connector home. Both cut-off relays fall back and if the other party fails to clear, his line relay prevents the relapse of PG and energizes PL so that a new cal is not started and an alarm is given. Inter-office calls. In response to a single digit denoting a main office call, shaft springs kk on the register energize JT which locks up, energizes E to start interaction between the magnets RM, DCM, and completes the test circuit C<2>, P, jt3, e4. When an idle line is found, P inserts Q (2) in the circuit of RM to stop the switches and P sends out ringing current as to a subscriber's line. If all junctions are busy, X in the limiting position energizes Q and P being unoperated, the subscriber gets the busy signal. TR as before energizes LV to cause the link circuit to switch through when the operator replies. The junctions may be two-way junctions, the incoming ends having line equipment like that of subscribers' lines. Party line working. Party lines are provided with a repeater, Fig. 4, before the individual relays shown in Fig. 1, When a party line subscriber makes a call, he grounds the end point of his bell, energizing AA, AV. AA loops the wires a b to initiate the seizure of a register controller, and subsequently repeats impulses dialled to it over both lines in parallel, as loop impulses. Reverting calls are set up by code ringing with a substation magneto. Such calls appear as permanent calls to the register controller which after an interval forcibly frees itself from the line and marks it busy as described below. Party lines are marked in a second bank on the register by a connection to a relay R which, on the relapse of D, replaces the usual ringing circuit by one over wiper dp1 of a code selecting switch DP, and energizes RD over dp2 in its normal position. The subscriber then dials an additional digit which operates DP over a3, rd2, r4, DPM. When DP moves off normal, E pulls up and RD is held over a back contact of A and so falls at the end of the digit. A constantly running cam CCC momentarily connects its three springs together to energize CC and then for half a revolution holds its inner springs together to keep it locked. CC on pulling up connects battery to the a-wire to energize S, Fig. 4, and cut out the repeater, and connects the selected code to the b-wire. At the end of the code, CC connects TR (1) to the a-wire (releasing S) and battery to the b-wire. The first relapse of S after the called party replies, energizes AA, which loops the wires ab to energize TR which causes the link to switch through. Restoration of the register releases R which makes a homing circuit for DP. Permanent calls. When the register controller is taken into use, V connects SA to one side of the interrupter SZ. SA on operation locks up and connects ZA to the other side of the interrupter. If the register controller is still in use when this contact closes, ZA locks up, releases B and consequently A, V, &c. in the register controller, TC in the link and CO in the individual circuit. L re-operates and holds PG which energizes an alarm relay PL. Metering. Ring trip relay TR completes a meter circuit tr2, jt2, 5<3> which is broken shortly afterwards when P is short-circuited. Metering does' not take place in the case of main office calls because JT is operated.