GB388065A - Improvements in or relating to telephone repeaters or the like - Google Patents

Abstract

388,065. Two-way transmission. ASSOCIATED TELEPHONE & TELEGRAPH CO., 1033, West Van Buren Street, Chicago, U.S.A. Aug. 18, 1931, No. 23281. Convention date, Sept. 2, 1930. [Class 40 (iv).] The alternate connection of the two paths of a repeater to the associated line circuits in accordance with the direction of speech is effected by differential relays 1, 2, controlled by voicecurrent relays 4<1>, 4, operated through additional amplifiers by incoming speech currents. The valves of the speech and control amplifiers are of the indirectly-heated-cathode type and normally receive a small heating current from battery A over resistances R, R1. When the junction with which the repeater is associated is taken into use for a call, the closure of a contact K, by a manual key or by plugging-in in the case of a manual exchange or automatically upon seizure of the junction in the case of an automatic exchange, operates relay 3 which by short-circuiting resistance R1 increases the heating current to its full value. Relay 3 also connects up anode battery B and supplies ground G to all the points marked on the Figure by ground within a circle. Differential relays 1, 2, 5, 6, 5<1>, 6<1> are then energized over both windings and do not operate. When speech arrives over line W, relay 4 vibrates its contacts, unbalancing relay 2 which connects up transmitting branch 8, 9 and disconnects receiving branch 8<1>, 9<1>, relay 6 which locks relays 1, 5<1>, 6<1>, in the receiving path against control by relay 4<1>, and relay 5 which short-circuits a third winding to maintain the connections during short pauses between words. A high-pass filter C, I, associated with relay 4<1> prevents operation of this relay by telegraphic frequencies in systems in which the line E between repeater points is used for telegraphy. The grids of the valves are supplied with positive bias from a battery D.