GB279455A - Improvements in telephone and like repeater circuits - Google Patents

Abstract

279,455. Standard Telephones & Cables, Ltd., (Assignees of Bjornson, B. G.). Oct. 19, 1926, [Convention date]. Two-way repeating systems.-In systems in which a relay 5, 30 short circuits one or more of the transmission paths until speech currents come in, the relay is guarded from operation by the comparatively weak disturbances that cause line noise by causing the incoming currents to pass to it over parallel paths including rectifiers 6, 8 or 15, 14 with different saturation currents, the currents in the two paths acting on it differentially. In one arrangement, Fig. 1, the relay has differential windings in the plate circuits of the valves, the valve 8 having a preponderating effect when the line is 'silent. Line noises produce equal effects in both windings and the relay remains in the position shown except for a kick at the beginning of the disturbance due to the retarding effect of a filter 12 in the lower path. In the case of speech however, the relay changes over in response to the strong impulse in the upper path and is not restored when the impulse, weakened by the limiting effect of valve 8, arrives from the lower path. A hang-over relay 25 prevents the end of the syllables from being cut off. In a modification, Fig. 2, the rectifiers act in opposition on a third valve 21 with a simple relay in its plate circuit.