GB379673A - Improvements in or relating to two-way electrical signal transmission systems - Google Patents

Abstract

379,673. Valve amplifying circuits. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.- (Assignees of Norwine, A. C. ; 53, Tennyson Place, Passaic, New Jersey, U.S.A.) May 30, 1931, No. 15883. Convention date, June 7, 1930. [Classes 39 (i) and 40 (v).] A quick-acting echo-suppressing arrangement for a telephone repeater system utilizes a gasfilled three-electrode discharge device, the grid of which is normally maintained near the ionizing potential so that on the application of speech currents a sudden rush of current rising almost instantaneously to its maximum value occurs in the anode circuit. A high resistance in the anode circuit limits the discharge so that cessation of the speech currents stops the discharge. In the arrangement shown in Fig. 1, when speech arrives over the line LW, a sudden rush of current is produced in the anode circuit of the discharge device 14, passing mainly over a condenser 22 and operating a polarized relay 21 which by removing a short-circuit from the right-hand winding of a second polarized relay 25 causes a short-circuit to be placed across the line LE. Relay 21 also closes an energizing circuit for relay 25 in series with a third polarized relay 27 which disconnects condenser 22 so that the discharge now passes entirely over resistance 29, and closes a parallel circuit for relay 21 over resistance 33 in order to counteract the tendency of the device 14 to oscillate. When speech ceases, relays 25, 27 remain operated for a short interval after the release of relay 21 owing to the provision of condenser 35 and resistance 28. In a modification, Fig. 3, the anode circuit of the discharge device 14 includes a condenser 64 or 65 according to the position of a switch 66, the effect of either condenser being to maintain the operation of relay 60 for a short interval after the discharge ceases. The discharge device is filled with an inert gas, e.g. argon, mercury, neon, at say 0À1 mm. pressure, or a mixture of gases, e.g. argon and mercury. The grid must shield the whole cathode from the anode.