Patent GB-378428-A (GB)
Title: Improvements in or relating to automatic telephone installations
IPC: H04Q3/00
Filed: 1931-05-09
Abstract: 378,428. Automatic exchange systems. BARON, H., 231, Strand, London.- (Lorenz Akt.-Ges., C. ; 1, Lorenzweg, Tempelhof, Berlin.) May 9, 1931, No. 13796. [Class 40 (iv).] A two-way junction has means at each end for preventing seizure at either end until release at both ends is complete. In the system described, impulsing and all control signals over the junction are effected by alternating current. The Figure shows apparatus associated with each end of a two-way junction VL, outgoing calls being made over switches AS, GW, and incoming calls over a hunting switch VW and a final selector LW. Establishment of connection ; outgoing end. When the junction is seized, relay JH operating over wiper c2 sends a pulse of A.C. over the junction, and relays A, V, C, Z(i), J, energize the last-named terminating the pulse. Impulses received over the calling loop are repeated by relay J to relay JH which transmits corresponding A.C. impulses over the junction, relay U being energized throughout each digit to disconnect the calling side of the repeater œ. Incoming end. The calling A.C. pulse operates relay W which in turn energizes relays A, V, U, S(i). Interrupter Un is connected to magnet D of switch VW and when an idle final selector is found, relay P2 operates, and relay S(ii) holds in series with relay N. Incoming A.C. impulses are repeated by relay W to relay N at the final selector, relays A, U operating at each digit to short-circuit winding S(ii) to improve the impulsing circuit, relay S being held however over its winding (i). When the called subscriber replies relay M reverses the current through winding S(ii), causing this relay to release momentarily and energize relay Z(i). Release ; outgoing end. If the calling subscriber hangs up first, relay J releases energizing relay JH which connects A.C. over the junction. Relays A, U, are also energized completing a short-circuit for relay V which after an interval releases, disconnecting relays Z, C. When Z releases, JH falls back and terminates the clearing signal, and when C releases, S(i) operates to hold open the test circuit for a further interval. If now release at the incoming end is not complete, A.C. is being sent back and relays W, A, U operate, the latter holding relay S. When release at both ends is complete, relays U, S de-energize slowly in succession and complete the circuit of the test wire to relay JH. If the called subscriber hangs up first, the A.C. clearing signal sent back over the junction operates relays W, A, U to release relays V, C, Z, in similar manner, and if this release is not complete when the signal ceases, relay JH operates to send A.C. forward. Incoming end. If the calling subscriber hangs up first, the A.C. clearing signal sent forward over the junction operates relays W, A, U, releasing relays V, N. When P2 falls back it closes a restoring circuit for switch VW, relay Z remaining operated over winding (i) until V releases and subsequently over winding (ii) until VW reaches normal. If the clearing signal ceases before Z falls back, relay JH energizes to send a signal forward to hold the outgoing end busy. If the called subscriber hangs up first, the release of P2 energizes JH to send a clearing A.C. signal to the outgoing end and restores switch VW as before. If the release at the outgoing end is delayed, the A.C. signal sent forward operates relays W, A, U, as before, to hold relay S and maintain the incoming end busy.