GB356111A - Improvements in thermionic valve circuits - Google Patents

Abstract

356,111. Transmission systems. STANDARD TELEPHONES & CABLES, Ltd., Columbia House, Aldwych, London.- (Reeves, A. H. ; 46, Avenue de Breteuil, Paris.) May 23, 1930, No. 15895. [Class 40 (iv).] A valve interposed between two sections of an electric transmission path is arranged to open and close the path by the action of a controlling impulse on a pair of reciprocally - coupled triode valves, in conjunction with one or more diode valves. As shown in Fig. 1, the device is arranged to control the operative condition of a repeater valve K interposed between an input line AB and an output line CD, and operates by affecting the bias of the valve grid. The device comprises a pair of reciprocally-coupled valves 1, 2 each having a battery E1, E2 and a resistance 13. 14 in its plate circuit, the junction of the battery and resistance for one valve being connected to the grid of the other valve. The control circuit FH is coupled by a transformer S to the grid circuit of the valve 1. In one position of equilibrium, the grids of the valves 2, K are sufficiently negative to block the transmission path AB, CD. In this position valve 1 is conducting, and valve 2 is blocked. When an impulse is applied in the control circuit FH, the condition of the valves is reversed, and grid 8 loses its negative bias owing to its connection to the plate circuit of the blocked valve 1. Consequently the main transmission path AB, CD is opened. A quick opening and slow blocking of the repeater K is provided for by the use of a condenser M across grid and filament of the valve 2, and a high resistance R shunted by a diode valve G is interposed in the lead from the plate circuit of valve 1 to the grid of valve 2. The effect of this is that a negative charge on the grid and on the condenser M can leak away quickly through the diode G, but a negative charge can only accumulate on the grid slowly as it has to traverse the resistance R. A diode E shunted by a resistance P is interposed between the transformer S and the grid of the valve 1, to ensure that only those impulses which render the grid negative are passed to the grid. The arrangement shown in Fig. 2 employs a pushpull repeater in the transmission path AB, CD. The operating voltages are applied to the grids and plates of the valves 1, 2 in the manner described in Specification 344,936, [Group XL]. Control impulses are applied through a transformer L connected between the plate circuit resistances of the valves. The transformer is shunted by a diode valve Q arranged to give quick opening and slow blocking of the repeater.