GB246544A - Improvements in two-way transmission systems with repeaters, particularly for telephone lines - Google Patents

Abstract

246,544. Western Electric Co., Ltd., [Western Electric Co., Inc.]. Oct. 21, 1924. Two-way repeating systems. -A repeat,er unit interposed in a two-wire line includes echo-suppressing circuits by which the return path is opened or short-circuited, so arranged that the echo-suppressor controlling the path in use cannot be operated by leakage of current through the hybrid transformer. Fig. 1 shows an arrangement with amplifiers 7, 8 and a single relay 13 adpted to short-circuit either path through a transformer, the windings being connected as shown through rectifiers 21 - - 24. For transmission East, for example, rectifiers 21, 24 receive current, and the corresponding windings of relay 13 move its armature against contact 26 to short-circuit the westward path. Either pair of rectifiers 21, 23 or 22, 24 may be omitted. In a modified arrangement, the single relay 13 is replaced by a pair of relays, one associated with each path. The windings connected to rectifiers 21, 24 then serve to hold the relay against possible operation by currents through the other windings. A delay circuit is inserted in each path. Fig. 2 shows an arrangement employing two controlling relays 33, 34 connected to rectifiers 32, 35. For transmission east, relay 33 operates to hold the eastward path closed, while relay 34 operates to open the westward path. A further relay 45 energizes and removes a shunt from the path in use. Delay circuits 30, 31, and, if desired, one-way valves 40, 41 are inserted in the two paths. Relays 36, 38 controlled by the relays 33, 34 serve to delay the removal of the short-circuit across the return path. In certain cases, the rectifiers and controlling relays may be replaced by A.C. relays. Modifications of this arrangement are described.