Patent GB-343674-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04M3/22
Filed: 1930-01-03
Abstract: 343,674. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and CHRISTIAN, D. A., Morven, Charlton Road, Charlton, both in London. Jan. 3, 1930, No. 286. [Class 40 (iv).] A switch which is normally used to connect one circuit, for example, a common control circuit, to an idle one of a group of other circuits, for example finder-connector link circuits, is adapted to give access also to equipment for routine testing the first mentioned circuit. When the test-plug is inserted, the normal test-circuit of the switch is opened and a circuit is prepared for stopping the switch on terminals connected to the routine tester. The invention, as described, is applied to testing a control circuit, Figs. 2 and 2a, identical with that described in Specifications 343,611 and 343,978 and serving to control a bi-directional call-finder and connector link-circuit connected up over switches CCA, CCB. The features tested comprise (1) impulsing arrangements for setting the call-finder, (2) response to dialled impulses under conditions simulating normal, high resistance, and low insulation lines, (3) response to idle and busy conditions of wanted line, (4) ringing arrangements both for individual and party line connections, (5) metering and release of control circuit. The various tests are initiated by keys controlled by an operator, the results of the tests being indicated by lamps. Plugs IP and TP are inserted in jacks IJ, TJ respectively, key EK, Fig. 2, is thrown to busy the control circuit in the banks of the assigner (not shown), and momentary operation of SK, Fig. 3, causes OS and L to lock up, lamp LTL remaining inert. Start relays ST, STT and relay AT operate over TP, and ground over L is connected to terminals 9, 21 of LS4 to simulate a call in the ninth level of the call finders. The switch CCA is stepped as described in the prior Specifications but the normal circuits of test relay T are open at a1 so that the switch steps on to its first terminals, and CCB follows, to connect up the routine testing equipment shown in Fig. 3. Lamp OPL glows, and test relay TA of CCB operates GD (i) which starts the interrupter relays X-Z and prepares a circuit for GD (ii) over wiper A6 in series with lamp VIL, and for magnet LS. At each impulse over y3, lamp VIL flashes and magnet LS steps until contacts 9 or 21 are reached whereupon M operates over LS4, jack TJ and relay L, and transfers the impulses to wiper A7 to flash RIL. The flashing of VIL and RIL checks the sending of impulses for controlling the vertical and rotary movements of the call finder. Ground from gd4, over m1, LS4 short-circuits L, Fig. 3, and lamp LTL glows. Key CK in the tester is now thrown so that GD falls back and dial-transmitter DD is connected over A4, A5 to impulse relay A. Relay V pulls up and sequence switch SS steps to position 1 in which D pulls up and short-circuits OS, Fig. 3, which releases ST, STT, AT, connects up lamp RIL and extinguishes LTL. Relay T remains locked by V. On receipt of dialling tone, the testing operator transmits impulses to A and by throwing key LLK or LIK may increase the resistance of the circuit or simulate a line of low insulation by connecting up a shunt resistance. The first train, repeated over a1, SS1, flashes VIL, and SS, which stepped to position 2 at the first impulse, proceeds to position 3 at the end of the train. Lamp HDL lights up over B8, SS5. The second train is dialled, SS moves to position 4, HDL is extinguished and VIL flashes as before. The third train is dialled with SS in positions 5 and 6, VIL flashes again, and SS moves to position 7. Relay G, operated in position 6, energizes test-relay P which locks, lights MTL, and operates PA to complete the ringing circuit RG, B4, bell CSB, B3, TR. The operator, hearing tone as well as the bell, throws the ring- tripping key ANS, and ground connected by TR to B6 lights lamp ASL. If busy-key BK is thrown before the end of the third train, test-play P does not operate and the busy signal is heard. The switch-through key TMK is now thrown, MR operates to initiate metering and release of the control circuit, and when relays V and P release, OPL, MTL are extinguished. Relay MR connects battery to A2 to operate a meter TM in the tester. The tests are now repeated, but a party-line number and ringing-code digit are dialled. R operates in response to the third digit, disconnects the normal ringing circuit, starts the interrupter relays X-Z, and connects magnet RC of the code selecting switch to SS3 (positions 7 and 8) in which the code ringing digit is repeated over a2 to RC. In the meantime the test circuit has been completed and relays P, PA operated so that RD is driven continuously by impulses from relay Y, and relay RR is operated in accordance with the code selected to complete the ringing circuit. At the end of each code cycle, RT connects TR to the ringing circuit and the operator trips by throwing key BK as before. The operation of the switches RC, RD is thus tested.