Patent GB-306922-A (GB)
Title: Improvements relating to automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1927-11-29
Abstract: 306,922. Siemens Bros. & Co., Ltd., Lambert, C., and Patterson, W. G. Nov. 29, 1927. Automatic exchange systems.-In final selectors having two sets of wipers, wiper selection is determined in accordance with the level over which the final selector has been seized by a relay included in one of the speaking wires accessible over one level. One of each pair of incoming speaking wires is thus individual to a particular level of the preceding selector whilst the remaining speaking wires and the test wires are commoned. The Figure shows a double-wiper final elector having P.B.X. lines connected to one of its banks only, wiper-selection being effected by a relay WS included in an incoming speaking wire bb. The preceding group selectors are of the double-wiper simultaneous-hunting type. Double-wiper testing and trunk-offering final selectors controlled by a distributor in the manner described in Specification 284,460 may be associated with the find-selector rack. Operation of final selector. If the switch is seized over leads aa, bb, cc, relay WS operates to connect up the second set of wipers A<2> - - C<2> locks to the test lead, disconnects itself from lead bb and connects the latter to lead b. The switch then operates in the same way as for a call over leads a, b, c. Relays A, B, C, operate as usual and the tens digit is repeated by relay A over contacts b5, hs5, e2 to the vertical magnet VM in series with winding 2 of relay C. At the end of the digit, relay C relapses and closes a circuit for relay E over rotary off-normal contacts nr1. The units impulses are thus directed to the rotary magnet RM, relay C operating again in series to maintain relay E operated. On the retapse of relay C, a circuit is completed over contacts h7, ws6, c4, winding 1 of relay HS and wiper X (assuming relay WS to be operated since all P.B.X. lines are connected to the bank of the wipers A<2> - - C<2>). If the line selector is the first of a group to a P.B.X., wiper X makes contacts with an earthed pin so that if this first line is busy relay HS operates and when relay E has relapsed a circuit is complete over contacts b4, el, hs4 and winding 2 of HS, for the rotary magnet RM and winding 2 of relay C. Relay C and rotary-magnet contacts zm, operate relay E which breaks the magnet circuit. Stepping thus takes place until an idle line is found when relay H operates and connects up ringing-current. Release. The connection between winding 1 of relay A and lead b includes a contact zm of the release magnet so that A is unable to operate for a further call until release is complete. Busy signal. If a called ordinary line or all the line of a F.B.X. group are busy, relay F operates over its winding 2 when relay E relapses and connects the busy lead over contacts f5, h6, nr2 to the a-wire. Busy tone and battery are alternately connected to the busy lead and during the battery period, relay D operates over its left-hand winding, completing at d3 a holding circuit for the release relays B, and connecting battery overwinding 1 of relay A to the speaking leads in parallel to send back a lamp-flash signal. During each tone period lamp CSH is lit. Selectors, mounting and arranging. Final selectors of the double-wiper type are mounted in shelves of 10 together with a test clerk's final selector and a trunk offering final selector upon one side of a rack, the other side carrying 198 line-switches arranged in panels of 33, three panels forming a hinged gate. Specifications 203,759 and 285,602 are referred to.