GB156876A - Improvements relating to transmitting apparatus for use in wireless telegraphy and telephony - Google Patents

Abstract

156,876. Bolitho, J. B. Oct. 6, 1919. Thermionic modulating systems.-In order to modulate the oscillations produced by a threeelectrode valve with a retro-active coupling, a control circuit containing a three-electrode valve has an inductance therein coupled with an inductance in the generator circuit in such a way that the reaction between them opposes the retro-action in the generator circuit. The generating-valve has inductances 8, 10 in its plate and grid circuits respectively coupled retroactively. The control circuit contains a highvoltage supply 12, such as an alternator or a three-electrode valve, and an inductance 11 in the plate circuit 4, 6. The grids 5, 2 and filaments 6, 3 are connected and a condenser 13 enables the circuit to be tuned to the same frequency as the circuit 8, 9. The inductance 11 is coupled with the inductance 10 in the reverse direction to that of inductances 8, 10. A telephone circuit may be included in the plate circuit of the control valve instead of the voltage supply 12. When negative potential is impressed on the plate of the valve 4, 5, 6, it is inoperative and the valve 1, 2, 3 can oscillate, but when positive potential is on the plate of the valve 4, 5, 6, this valve will oscillate but the reaction of the inductance 11 on inductance 10 more or less neutralizes that of inductance 8, so that the energy produced by the valve 1, 2, 3 is correspondingly varied.