Patent GB-357186-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/28
Filed: 1930-06-18
Abstract: 357,186. Automatic exchange systems. AUTOMATIC TELEP H 0 N E MANUFACTURING CO., Ltd., Strowger Works, and C A S W E L L, A. E., Ingleside, Milton Road, Edge Lane, both in Liverpool. June 18, 1930, No. 18652. [Class 40 (iv).] In arrangements for the routine testing of apparatus associated with the incoming ends of a group of two-wire junctions, one junction of the group. used normally for conversation is employed during testing as a control junction and gives access to the outgoing ends of the other junctions in order that each may be marked busy during the test on the associated apparatus. Stepping switches at both ends associate the control junction and the routiner apparatus with each junction in turn. Tests are made over each junction conductor separately and alarms are given if a junction is faulty or the stepping switches get out of synchronism. Detailed operation. Figs. 1 and 2 show the outgoing and incoming ends, respectively, of an ordinary junction 10, 11 and the control junction 15, 16, the incoming ends being associable with the routiner over an access switch AS, Fig. 3. (The relay contacts shown in Fig. 3 enclosed within a small rectangle belong to routiner relays not shown.) When the routiner start-key is thrown relay SL operates and when the switch AS engages with its first contacts, connected to junction 15, 16, relay PE operates provided that the junction is free. Relay RT disconnects the junction 15, 16 from apparatus at its incoming end, connecting earth over conductor 15 to operate relay LA. Relay B also operates to mark the junction busy, and busy or NU tone is connected up in case the junction or apparatus associated therewith may be faulty and a subscriber connected thereto, or is seized by a subscriber simultaneously with its seizure by the routiner. When the desired tests have been performed on the apparatus associated with the control junction, switch AS advances a step and relay TF (not shown) de-energizes relay LA temporarily, causing switch SD also to take a step. The low-resistance earthed winding of relay H serves to mark the selected junction busy over wiper 3b. Unless the junction is already busy relay H operates completing a circuit over relay LB, conductor 16, and relay L. The latter operates and by short-circuiting its left-hand winding enables LB to operate. A circuit is now completed over junction conductor 11 for relays LC, TB and if the junction is in order relay LC operates and connects earth over the other junction conductor 10 to operate relay TA. Relay TA releases relay PF which by connecting earth to lead 24 permits the test on the apparatus associated with the incoming end of the junction 10, 11 to proceed. If either of the junction conductors is broken relay TA does not operate and an alarm is given. If the switches SD, AS are not in engagement with the same junction either TA, TB will both be inoperated, i.e. if AS is in engagement with an idle junction, or both will be operated, i.e. if the junction is busy and therefore looped. In either case an alarm is given. Lamps connected to bank 4b of switch SD indicates the junction under test.