GB172593A - Improvements in and relating to electron discharge devices - Google Patents

Abstract

172,593. British Thomson - Houston Co., Ltd., (General Electric Co.). Aug. 24, 1920. Vacuum tubes.-A thermionic valve or other discharge tube for use in wireless transmitting systems has means for setting up a magnetic field of a magnitude near that at which the field produces a decrease in the current passing through the valve, and a control grid for varying the electrostatic fields between the electrodes. In one arrangement, Fig. 2, a winding 19 around the tube produces a magnetic field parallel with an incandescent filament 8 and an anode 17, the current being controlled by a helical grid 12. The anode is connected through one winding of an aerial transformer 23, and a battery 25 with the cathode, and is coupled with the grid through a variable condenser 29. The grid-cathode circuit includes an inductance 28. The capacity and inductance are turned so as to cause the valve to oscillate. The winding 19 is in series with a battery 38 and inductances 39, 40, the strength of the magnetic field being such that a small increase causes a large decrease in the amplitude of the oscillations. A telephone transmitting circuit, comprising a microphone 42, a battery 43, an inductance 44, and condensers 45, 46 of large capacity, is connected with the winding 19 so as to modulate the oscillations produced by the valve. In a modification for use as a wireless telegraph transmitter, the winding 19 is connected in series with a battery and a signalling key, the production of oscillations being stopped when the circuit through the winding is closed by the key. In another arrangement, Fig. 3, oscillations are produced by the action of the magnetic field of the winding 19 on the current in the valve, and the oscillations are modulated by varying the potential of the grid 12. The winding 19 is in series with one winding of an aerial transformer 53, a variable condenser 57, and one winding of a transformer 54, the other winding of which is shunted by a variable condenser 58, and is connected with the anode 17, and through a battery 59 with the cathode 8. By tuning the anode-cathode circuit and the circuit of the winding 19, the valve may be made to produce oscillations, which may be modulated by a microphone 60 varying the potential of the grid through a transformer 62. Specifications 130,400 and 167,561 are referred to.