GB334218A - Improvements in or relating to telephone systems - Google Patents

Abstract

334,218. Automatic Telephone Manufacturing Co., Ltd., Gillings, C., and Rice, T. G. May 29, 1929. Automatic exchange systems. -A finder switch, taken into use over a chain start lead, is provided with a plurality of sets of wipers, the'set to be used being determined before the switch starts hunting. Two groups of switches serve two groups of lines, one group over each wiper set, and a first group switch is called upon to serve the second group only if all the switches in that group are engaged. In the embodiment described a Strowger type switch with two sets of wipers serves two groups of lines. Hunting is controlled over one wiper set only, a relay connected up prior to the commencement of hunting determines which set of wipers is to be used. A line served over the upper wiper set is indicated in Fig. 1. When a call is originated LR operates, removing the earth from the contact of the calling line and energizing 1A. Relay 1A operates D (Fig. 1) to connect up the upper' wiper set and energizes relay A which in turn connects up relay B to connect holding earth to the test conductor. Relay 1A also places earth on the contact of the level calling in bank VA (Fig. 3). Relay G pulls up (via V and R) completing a circuit for the vertical magnet VM, and G and VM interact until the wiper VW reaches the marked bank (the first in the example given) when T operates and locks, connecting relay G to the rotary test wiper and changing over to the rotary magnet RM. Relay G remains operated in series with T until RM operates to step the wipers on to the first rotary contacts. Relay G and magnet RM then interact until the calling line is reached when G fails to pull up and H, being no longer shorted, operates and switches through the calling line. Relay CO pulls up, removing the battery connections from the calling line and releasing 1A. Relay HR pulls up and is held throughout the conversation. The relay HR connects the start and discriminating leads S and D, Fig. 3, on to the next finder in the group and when all the finders in the group are busy a chain circuit of leads S and D is completed and relay AB is operated. Should another call now be made in the A group, relay AW operating in series with one of the relays 1A - - 10A will energize AY connecting the start and discriminating leads to the B group switches and operating relay LH to common the vertical banks VA and VB. The call then proceeds as previously described. Relay AY breaks the circuits of relays 1B - - 10B to prevent a " B " group call from seizing a finder whilst the vertical banks are joined. Similarly the B group lines can use the A group switches but in this case, as relay D, Fig. 1, is not operated, relay BY connects up the start lead only. To provide a minimum of vertical hunting movement the multiple of the finder switches is " slipped." A switch hunting for predetermined potential is also described. Specification 333,928 is referred to in the Provisional Specification.