Patent GB-141674-A (GB)
Title: Improvements in or relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1920-02-17
Abstract: 141,674. Automatic Telephone Manufacturing Co., (Assignees of Jacobsen, E.). April 11, 1919, [Convention date]. Automatic exchange systems.-The line switch of each of a group of lines, all corresponding to the same number, is adapted to act as a finder switch to select the trunk over which a call is being made to that number. For this purpose, each line switch has a series of terminals leading to group-selectors or connectors over which outgoing calls are made in the usual way, and a second series of terminals connected respectively to the terminals of the several connectors serving that number. The group of lines is represented in each connector by a single set of terminals, and when the connector wipers engage this set, the line switch of the first idle line is set in motion to connect that line to the set of terminals to which the incoming call is extended by the connector wipers. The line switch is provided with two sets of testing-arrangements so that the two distinct operations of the switch are mutually independent. Operation of line switch C', Fig. 2, for outgoing calls from multiple-line subscriber B. The switch C' is controlled in this case by the test wiper 60, the terminals, engaged thereby, corresponding to the trunks from the connector bank terminals being permanently earthed. When the subscriber B removes his receiver, the line relay 85 closes a circuit for the stepping-magnet 354 through the switching-relay 27, which is shortcircuited over wiper 60 until an idle outgoing trunk is found. Connexion of ordinary subscriber A, Fig. 1, to idle line of subscriber B, Fig. 2. When the subscriber A removes his receiver, his line is extended in known manner by switch C to an idle collector H, the relays 9, 10 being energized. The first set of selecting-impulses is repeated through the series relay 12 to the vertical magnet 13; when these cease, the relay 12 prepares a circuit through relay 23 for the rotary magnet 22, which is operated by the next set of impulses and brings the wipers to the set of terminals of the multiple-line subscriber B. If all his lines are in use, the cut-off relays 27, 28, 29, Fig. 2, of these lines will all be energized, and a circuit completed over resistance 38, Fig. 2, contacts 37, 35, 33, wiper 31, for relay 41, which connects a busy generator to the calling line, the connexion being released when the subscriber replaces his receiver If, however, one of the lines, say that shown in Fig. 2, is free, the circuit of the rotary magnet 54 of its switch C' is completed over contact 53, wiper 31, and the upper winding of relay 41, which is not energized owing to the resistance of magnet 54. The switch C<1> rotates under control of wiper 61 until it finds the connector handling the incoming call, when a circuit is closed from battery over relay 64, Fig. 1, and wipers 49, 61, for relay 69, Fig. 2, which operates the switching-relay 27 to arrest the switch C<1>. The relays 64, Fig. 1, 27, Fig. 2, complete the connexion of the ringing-generator R, Fig. 1, to the called line the ring-cut-off relay 71 being energized, when the subscriber replies, to disconnect the ringing-current and extend the called line to the back-bridge relay 72.