Patent GB-401433-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/42
Filed: 1932-07-13
Abstract: 401,433. Automatic exchange systems. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and HAMILTON, R. M., c/o General Electric Co., Stoke, Coventry. July 13, 1932, No. 19796. [Class 40 (iv).] The switches serving a group of subscribers' lines comprise (1) a group of normally used finders directly connected to group selectors, (2) a group of normally used connectors, and (3) a group of dual function switches taken into use when all the normal finders or connectors are busy and which, when acting as finders, have access over hunting switches to group selectors fewer in number than the normally used group selectors. Common control circuits are used and, as described, the control circuits of the normal finders and connectors are used also for the dual function switches. The homing circuits of the numerical selectors involve the common control circuits so that a numerical selector must await an idle condition in its control circuit before homing, the control circuit being busied during the homing. A dual function switch may be taken as a finder before it has homed. The line circuits comprise a single slow-operating relay which makes a circuit for a quickly operating common start relay over make-before-break contacts, the operation of the start relay being assisted by discharge of a condenser charged over the start circuit. The finders and connectors have two sets of wipers while the group selectors have three, and are controlled by markers. The connectors are marker-controlled for the tens digit and directly impulsed by the units digit. Penultimate selector feed is used, the bridge being connected up when the wanted line has been found. Switches acting as finders have their test banks connected one step ahead of the speech banks, and the dual function switches are arranged normally to act as connectors, their function being changed by a relay operated when the switches are seized for use as finders. The sheets of drawings should be arranged as in Fig. 12A for normal connections, and Figs. 12B and 12C respectively for connections using a dual function switch as a finder and connector. Normal connection, Line finder and allotter, Figs. 9 and 4. The slow-operating combined line and cut-off relay CO, Fig. 1, in pulling up first closes momentarily all contacts of the make-before-break springs CO1 to energize CS, Fig. 4, this operation being assisted by the discharge of condenser 14 when the back contacts of CO1 are opened. CS locks itself, holds CO and operates W, whereupon P pulls up and KJ, AJ in the 1st group selector, Fig. 6, and its control circuit, Fig. 7, respectively operate followed by BJ, which holds KJ. Magnet ZJ of the finder steps in a self-interrupting circuit over ZC2 until the finder reaches contacts immediately preceding those of the calling line which is marked one step ahead in ZJ8 to operate NA (over a rectifier) which disconnects the hunting circuit of ZJ and holds it over ZC3. Relay P holds until the interrupter springs open when its relapse releases the magnet to step the finder on to the calling line. Relay U pulls up to ground returned by the group selector over the hold wire 35, releases NA, W, and operates the appropriate switching relay say X, during the release period of W, X remaining held over 35. Relay Q in the allotter is operated by the holding ground and NA re-operates followed by the allotter magnet ZC which interacts with NA to step the allotter until an idle finder, selector and common control circuit (battery on bbj2, Fig. 7, ZE7 normal, 35) operates U which releases Q, NA and falls back. The ground connected to U is direct over the commoning of the first part of ZC5 which corresponds to the regular finders, but is connected up over the contacts of regular switching relays in series over the second part of the bank which corresponds to the combined overflow switches so that one of these is not allotted for use unless all the regular finders are busy. First group selector, Figs. 6 and 7. Relay KJ has operated to connect the selector to its control circuit in which AJ, BJ, BBJ are operated, The selector has three wiper sets and a control wiper ZE10, each group being distributed over the three sets of banks. The magnet ZE is connected via kj8 and banks ZG3 to ZG6 to all contacts of ZE10 other than the group on which ZG is resting at any particular instant. Digit 1 is not used. The impulses are repeated to magnet ZG of the control switch and CJC in parallel, and on the relapse of CJC if the digit is 2 or at the end of the third impulse if the digit exceeds 2, the wiper of ZE10 is connected via springs ze, kj1, wiper ZG1, to ground over BBJ, the circuit including contacts of test relays EA-EC which relays correspond to the three switching relays of the group selector. Selector ZE, therefore, chases the control switch, and on the relapse of CJC at the end of the train, DJ is connected to wiper ZG2 standing on a contact connected to the group in ZE10 which is unmarked by ZG3 .. ZG6. When the grounded wiper ZE10 reaches this group, DJ pulls up followed by CS, which grounds the test relays EA-EC, and operates SJ which energizes magnet ZE. The magnet interacts with DJ until one of the test wipers ZE7-ZE9 finds battery over an idle second group selector and control circuit whereupon a switching relay and test relay, say HAJ and EA, pull up in series. Relay EA stops the hunting, releases DJ and disconnects the other relays EB, EC to prevent double switching. HAJ switches through, releases AJ, BJ, BBJ and KJ falls back to disconnect the control circuit. All outlets busy. DJ falls back when the last contact is reached, CS releases, but SJ remains held since neither EA, EB, EC is operated, and busy tone from 37 is connected over AJ. Second group selector, Fig. 8. When this selector is seized, KK connects up a common control circuit similar to Fig. 7 and operates AK. The selector is set in exactly the same manner as the first group selector except that digit 1 is permissible. One of the switching relays BK-EK pulls up and when KK releases, JK (left) is connected to the outgoing third wire, which, however, is grounded at the final selector control circuit at this time so that JK remains inert. Final selector, Fig. 10, and common control circuit, Fig. 5. On seizure A, Fig. 5, and KQ, Fig. 10, pull up over the calling loop and KQ connects up the common circuit. As the final selector has two sets of wipers, pairs of connected contacts in the marking bank ZD5 are connected to groups of 10 in the control bank ZK9 of the final selector. Relays B, BC, BB in the control circuit pull up, BB eonnecting ground to the third wire of all finals over individual contacts bb3. The tens digit is repeated by A to C and magnet ZD in series, and at the end of the third impulse (the final selector does move for digits 1 and 2), magnet ZK of the final selector is stepped over ZD4 until D pulls up over ZD5, ZK9, locks up, and operates E since C has relapsed. Relay E opens the self-stepping circuit of ZK and transfers the impulsing circuit to ZK which receives the units digit. Relay C operating during the train energizes G which is followed by L, and on the relapse of C, M pulls up in series with one or other of the wiper switching relays AQ, BQ and the cut-off relay of the wanted line. This circuit includes a rectifier RE, Fig. 5, and the switching relay depends on whether the tens digit is odd or even. Completion of connection. AQ or BQ shortcircuits M, locks up to the third wire, removes ground therefrom at the final selector, and releases A, B, BC, BB, L, D in the control circuit which the associating relay KQ also restores and the marker goes home. The removal of ground on the third wire at the final selector removes the short circuit on JK, Fig. 8, which connects up ringing over FK and ringing tone over 37, and temporarily opens the third wire in the second group selector. On reply of the wanted party, FK connects in circuit a transmissing bridge comprising relays AK, DK and the usual condensers. JK falls back and during its release period booster metering battery is connected up over 38. Wanted line busy. Relay M does not operate and on the relapse of G when C falls back, L remains held and busy tone from 25 passes back over relay A. Release. When the calling party hangs up, AK, Fig. 8, falls back and releases the operated switching relay (BK, CK or EK) so that groung is removed from the third wire which is continuous throughout the switches. The other switching relays and the cut-off relays fall back and DK relapses if the called party has not hung up. The first selector homes over connections between ZE10 and the banks ZG3- ZG6 of the control switch, Fig. 7, if or when idle, the homing circuit including BBJ which busies the control circuit. The penultimate selector homes in a similar manner. The final selector homes over ZK9 over a circuit including BC, Fig. 5, in the control circuit, BB being operated by BC to busy the control circuit. All finders busy ; overflow switches, Fig. 2. If all regular finders are busy, ground over contacts of the switching relays in series is connected to the second half of the commoning of ZC5, Fig. 4, to provide a ground for U so that the allotter stops on an idle dual function switch, Fig. 2, when U operates in series with K. Relay Q releases and W pulls up as previously described so that S, Fig. 2, operates, opens the test circuit from the 2nd group selectors to the dual functon switch, marks it in banks ZB4 of secondary line finders ZB, Fig. 3, and connects ground to relays V to start up the idle ones which have battery on the third wire from an idle 1st group selector control circuit. Relay S also opens the test circuit over ZA7 normal, and disconnects the associating relay K to prevent the switch being seized as a final selector. It should also be noted that the test circuit of the switch as a finder does not pass over a normal bank contact since it is imm