Patent GB-284765-A (GB)
Title: Improvements relating to selectors in automatic telephone systems
IPC: H04Q3/00
Filed: 1926-11-03
Abstract: 284,765. Siemens Bros. & Co., Ltd., and Patterson, W. G. Nov. 3, 1926. Automatic and semi-automatic exchange systems.-In a rotary connector having two sets of wipers and associated banks, after the vertical magnet has operated, hunting takes place in succession over the two levels engaged by the wipers, the latter being returned to the rotary normal position after the first hunting movement, and the two sets being effective alternately. Two arrangements are described, one suitable for private branch exchange groups containing up to 20 lines, the other (Fig. 2) suitable for groups containing up to 200 lines. The latter arrangement differs only from the former in that means are provided for lifting the wipers to the next pair of levels after each pair has been searched over. A busy signal is sent back at the completion of the search if no idle line is found. The modifications shown in dotted lines relate to the invention of Specification 284,766. Circuit arrangements, Fig. 2. Upon relapse of change-over relay C at the end of the vertical movement, relay DR(1) energizes and connects up rotary magnet RM. Relay C(2) is operated at contact rm by the stroke of the magnet, and this relay serves as a stepping relay. If no idle line is found in the level engaged by the upper set of wipers, when the 11th terminals are reached, test relay H(1) energizes over test wiper C in series with relay DR(2), and locks over H(2). Relay RN(1) now energizes over wiper A and locks over RN(2), releasing test relay H (both windings). Rotary release magnet RZM operates and returns the wipers to the rotary normal position. The circuit of relay RN (2) is broken at contact nr1, but before it falls back, relay E energizes and locks, switching over the connections to the lower set of wipers, Magnet RZM is disconnected and hunting takes place over the level engaged by the lower set of wipers. If no idle line is found, test relay H energizes as before over the 11th terminals, but vertical stepping relay VS(1) now energizes over wiper A<1> and releases wiper relay E. Relay RN energizes over wiper A. releases test relay H, and completes a holding circuit for relay VS(2) in parallel with rotary release magnet RZM. The wipers are returned to the rotary normal position, and upon the relapse of relay RN. a circuit is closed for vertical magnet VM, which raises the wipers one step. Relay RN also opens the holding circuit of relay VS(2), which falls back and substitutes rotary magnet RM for vertical magnet VM. Hunting takes place over the pair of levels with which the wipers are now in engagement. When an idle line is found, test relav H(1) energizes and locks over H(2), releasing relay DR(1). which connects up ringing current over ring cut-off relay F(l). Upon reply of the called party, the latter energizes, locks over F(2), and connects up back-bridge relay D. If the search is completed without an idle line being found in the group. test relay H energizes over the 11th terminals of the last level engaged by the lower set of wipers. and busy relay BO energizes over grounded wiper B' and contact s1. Relay VS also operates. but wiper relay E is now held at contact bc1. Busy tone and flash battery are fed over wire BB to back-bridge relay D, which energizes intermittently and applies battery over line relay A (1) to both the incoming line wires. release relay B being held while relav A is de-energized. A congestion meter may be actuated in series with busy relay BC.