GB324642A - Improvements in or relating to telephone systems - Google Patents

Abstract

324,642. Automatic Telephone Manufacturing Co., Ltd., Gillings, C., and Rice, T. G. Oct. 29, 1928. Automatic exchange systems. - A hunting switch is provided with two test wipers, hunting being controlled over one of the wipers whilst switching and holding is controlled over the other, holding being effected by a different potential to that controlling switching. The whole switch train is held from the first selector which is provided with two test conductors, one arranged to be extended to hold preceding and succeeding switches whilst the other controls the hunting motion of preceding switches. A full connection through group selectors, selectors with double contact banks and final selectors is described in the Specification. Line switch, Fig. 1. The relay L pulls up over the subscriber's loop and DM operates from 14 (H, HM) stepping the switch off normal, subsequent move ment originating from earth received by HM from engaged selectors. When a free line is reached no earth is encountered by HM but battery over S operates K which locks at 20 to 14 until earth is returned over S. First selector, Fig. 2. Wire HM<1> is normally disconnected and S<1> is connected to battery through magnet R. When K (Fig. 1) switches through A operates, allowing AB and then B to pull up. Relay B connects earth to both S' and HM<1>, the former to hold relay K and the latter to mark the switch busy to hunting line switches. When the switching relay H operates S' is extended to P. Second selector, Fig. 3. Relay A operates over the extended loop and B operates locking to earth received from the first selector over the test conductor 18. As B is not dependent on A, a slow release slug is not required. When the call is passed forward H locks itself up to the earth on 18, which it extends forward to hold subsequent switches. Metering. When the called subscriber replies, D (Fig. 2) operates opening the circuit of slow relay MD (which operated on the first rotary step of the switch).When the connection is released AB releases opening the circuit of B and during the slow period of B battery from 41 is connected to HM<1> to operate the subscriber's meter.