Patent GB-228720-A (GB)
Title: Improvements relating to selectors for automatic telephone systems and the like
IPC: H01H67/16
Filed: 1924-02-29
Abstract: 228,720. Siemens Bros. & Co., Ltd., (Bernard, G. H. B.). Feb. 29, 1924. Automatic exchange systems; selectors.-The off-normal contacts of selectors are prevented from operating until the completion of the corresponding movement, by a sluggish magnet energized by the driving impulses. The invention is described in connection with a group selector and a connector. Construction of switches. As shown in Fig. 1, separate magnets K, W, are provided for the vertical and rotary springs 2, 3. Vertical movement releases the lever 4 and rotary movement the frame 11, in known manner, but they are prevented from moving to allow the springs to close by the magnets K, W. Once the springs have been operated, energization of these magnets is without effect. In the modification shown in Fig. 2, the magnets K. W, are replaced by a single magnet X with an armature shaped so as to engage both the lever 4 and frame 11. The notch 16 is provided to prevent accidental energization of magnet X after the operation of the rotary springs from having any effect. First selector, Fig. 3. Impulse relay A pulls up over the incoming c-wire, energizes release relay V and is then put under control of the calling loop and repeats the first digit to the vertical magnet VM over the sluggish magnet K which prevents the change-over of vertical springs k<1>, k<2> until the end of the digit. When these springs change over an interrupter circuit is made over the sluggish magnet W for the rotary magnet RM and the wipers advance until relay T pulls up over the test terminal of an idle line. The relapse of magnet W allows rotary springs w<1> to change over and disconnect winding 1 of relay T. Subsequent digits are repeated by relay A over the b-wire. In case a single magnet is used for controlling both sets of off-normal springs, it is arranged between contacts t<5> and k<2>. Connector, Fig. 4. When the connector is seized, relay A pulls up and an instant later, relay N. The tens digit is repeated by relay A to the vertical magnet VM and sluggish magnet K which delays the change-over of the vertical springs k<1> - - k<4> as in the group selector. The change-over of springs k<1> - - k<4> energizes a sluggish relay G and the final digit is repeated to the rotary magnet RM and sluggish magnet W after which the rotary springs w<1> - - w<4> change over, disconnect relay G and connect up the test relay T. A single magnet to replace magnets K, W, would be connected between contacts a<1> and k<2>. Busy test and signal. If the wanted line is busy its test terminal is dead or connected to battery over relay T in another connector, and relay T fails to energize. After an interval, relay G falls back, disconnects the test relay and energizes relay TR over its winding 2 to connect up busy tone from BS. Ringing current and signal. If the wanted line is idle, relay T pulls up over the cut-off relay, short-circuits its winding 1, and cuts off relay A. On the relapse of relay G, ringing relay S pulls up, and ringing current from RG is sent forward over winding 1 of the tripping relay TR, and ring- ing signal from RS is sent back. The energization of relay TR when the called party responds, short-circuits relay S to complete the connection. Release. When the calling party hangs up, relays A, V, I, in the group selector fall back, release magnet M operates, and the outgoing c-wire is disconnected to release relay N in the connector. Relay N releases relay T and energizes release magnet M.