Patent GB-167561-A (GB)
Title: Improvements in and relating to electric discharge devices
IPC: H01J21/18
Filed: 1920-05-07
Abstract: 167,561. British Thomson - Houston Co., Ltd., (General Electric Co.). May 7, 1920. Vacuum tubes. - In a thermionic or like valve operating with a substantially pure electron discharge, the discharge is controlled by a magnetic field of a magnitude near the critical value at which a small increase in the field produces a substantial reduction in the current passing through the valve. The cathode is preferably a heated filament, which may be straight or V-shaped, or in the form of a single or double helix, the anode being preferably in the form of a cylinder or circular loop, and arranged symmetrically with respect to the filament. The magnetic field extends parallel with the cathode. Two windings may be used, one for producing the polarizing field, and the other the controlling field, or a single winding may be used for producing both fields. A cylindrical anode may be slotted to prevent screening of the magnetic field and may be made of thick copper, or of molybdenum or nickel. A metallic deposit on the wall of the valve may be used as an anode. In the amplifier for wireless receiving systems shown in Fig. 1, a straight filament 2, surrounded by a cylindrical anode 3, is heated by current from a battery 6. A winding 16, producing the polarizing field, surrounds the tube, and is energized by a battery 19 in series with a variable resistance 20 and a choke coil 21. A winding 10, producing the controlling field, is energized by the incoming oscillations from an aerial' 14. A crystal detector 24, a telephone receiver 25, and a battery 23 are connected between the anode and the filament. In the telephonic amplifier shown in Fig. 5, the control winding 10 is .connected in series with the secondary of a transformer 27, the primary of which is in series with a telephone transmitter 28 and battery 29, and the polarizing winding 16 is energized by a battery 19. The anode 3 is connected with the cathode 2 through a battery 23, a variable resistance 31, and the primary of a transformer 30, the secondary of which is in series with a telephone receiver 33. The battery 23 and resistance 31 are shunted by a condenser 32. In the telephonic amplifier shown in Fig. 6, two valves A, B are used, each of which has a single winding, each producing polarizing and controlling fields. The winding 36 of the valve A is energized by a battery 37 in series with a variable resitance 39 and a choke coil 38, and is connected with a telephone transmitter 28, a battery 42, and an inductance 44 through a condenser 43. The filaments of both valves are heated by alternating current supplied through transformers 34, 35. The winding 36 of the valve B is energized by a battery 47 in series with a variable resistance 49 and a choke coil 48, and is connected with the middle point of the secondary of the transformer 34, and through a battery with the anode of the valve A. The anode of the valve B is connected through a telephone receiver 53 and a battery 52 with the middle point of the transformer secondary 35. In the wireless receiving system shown in Fig. 8, one valve C acts as an amplifier and another valve D as a detector. A winding 70 producing the controlling field is connected in a closed oscillating-circuit coupled with the aerial 68. The filament 2 of the valve C is heated by alternating current from the secondary 86 of a transformer. A winding 71, producing the polarizing field, is supplied with rectified current from a secondary winding 72 through a rectifier 75. Resistances 76, 77, a ballast resistance 78, and condensers 79 are used as a filter to smooth. out the rectified impulses. The output circuit of the valve C is connected with a variable condenser 93, and a winding 91 on the, valve D. An indicator, such as a telephone receiver 98, is connected between the anode and the .filament of the valve D through a battery (not shown). In the wireless telephone system shown in Fig. 7, a winding 55, producing a polarizing and a controlling field, is energized by a battery 36 and is connected with a telephone transmitter 28 in a manner similar to that shown in Fig. 6. A second winding 56 is connected in the anode-cathode circuit 3, 2 and in series with a battery (not shown), a choke coil 59, and the primary of a transformer 60 the secondary of which is in the circuit of the aerial 63. A 'variable condenser 61 shunts the winding 56 and the transformer primary. The action of the coil 56 on the current through the valve produces highfrequency oscillations which are modulated by the current in the winding 55.