GB403674A - Improvements in or relating to two-way telephone systems - Google Patents

Abstract

403,674. Two -- way transmission. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, and MATHIEU, G. A., 3, Mayfield Gardens, Shirehall Park, both in London. June 27, 1932, No. 12535/33. Divided on 392,210. [Class 40 (iv).] The radio-transmitter and the receiving path of a repeater for coupling a telephone line LS with ultra short wave radio apparatus are rendered operative in accordance with the direction of signals by a pair of triodes V14, V<1>14 each having its grid connected to the anode circuit of the other. Alternatively the low-frequency transmitting path may be controlled instead of the transmitter itself. Signal currents arriving from the line LS produce by the rectifying action of V<1>14 a voltage across condenser C2 which (a) paralyses V14, (b) starts the transmitter oscillator VT1, VT2 in the manner described in Specification 392,210, [Group XL], by removing the short-circuit normally provided across the resistance R by the valve KV, (c) paralyses the receiving amplifier G, (d) stops the current through a valve V15 to cause a differential relay C1 in its plate circuit to light the lamp L1. The characteristics of the amplifier G and the valve KV are so chosen that the receiving path is blocked before the transmitter oomes into operation. On the cessation of speech from LS, C2 discharges through a high resistance R2, but the current through V15 quickly rises sufficiently to operate C1 in the opposite direction. Condenser C11 is then charged through a further relay AL which short-circuits C2 to bring the circuit into a condition in which reception is possible. Signals from the radio receiver, provided V11 is not paralysed, are rectified by V14 and produce a voltage across condenser C3 which (a) paralyses V<1>14 and (b) stops current through V13 so as to raise the plate voltage of V12 (which is fed through a common resistance from the same source as V13 to its optimum value. In the absence of speech V12 is made inefficient by the reduction of plate voltage to limit the amount of noise passed to the hybrid coil. In a modification V<1>14 instead of controlling the transmitter controls apparatus in the transmitting path from C similar to that shown at J. The amplifiers at B and I through which the controlling portions of the signals pass may be tuned so as to be particularly responsive to syllabic energy.