Patent GB-481791-A (GB)
Title: Improvements in or relating to electron discharge devices
IPC: H01J31/14
Filed: 1936-06-16
Abstract: 481,791. Discharge apparatus ; wireless receiving circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. June 16, 1936, No. 16781. Convention date, June 27, 1935. [Classes 39 (i) and 40 (v)] An electron discharge. device suitable for use as a tuning or like voltage indicator comprises a cathode having two electron emitting sections, an anode and a control grid surrounding the first section, a second anode coated with fluorescent material and arranged to be visible through the envelope and to receive the electron stream from the second cathode section, and a control electrode electrically connected to the first anode and serving to control, in dependence on the potential of the first anode, the angular divergence the stream of electrons incident on the fluorescent anode. In one form, the tubular mesh fluorescent anode 20, Fig. 1, surrounds one portion 16 of the cathode, the other portion of which is surrounded by anode 15 and control grid 14. The control rod 17 is connected to the anode 15. When used as a tuning indicator, the negative rectified carrier voltage is applied to the grid 14. A resistance is connected between the anode 15 and the supply ; as the grid 14 becomes negative the anode 15 and hence the rod 17 approaches the potential of the anode 20 which is directly connected to the supply. As the rod 17 becomes more positive its shadow on the anode 20 becomes smaller and the edges thereof may be made to coincide or oven to overlap, giving a sensitive indication of the voltage on the grid 14. Two diametrically opposite control rods may be used. In another form, the fluorescent anode is a flat plate 27, Fig. 6, on which is thrown an oblique electron beam of width varying with the potential of a slotted control cylinder 25. That portion only of the cathode 16 which is opposite the slot 26 is coated with emissive material. Other forms are described in which flat or V-shaped fluorescent anodes and control members are disposed on opposite sides of the cathode. Specification 443,602 is referred to. The Specification as open to inspection under Sect. 91 comprises also the connection of the control electrode to the control grid of the associated valve. In the form shown in Fig. 8 (Cancelled), one section 51 of the cathode is surrounded by a pentode assembly, the supporting rods 57 of the control grid being extended upwards so as to form a control electrode between the other cathodic section 56 and the mesh fluorescent anode 59. Oval wire rings 58 secured to rods 57 concentrate the beam from cathode 56 axially. The anode 59 is split to reduce high-frequency heating during exhaustion. The device is used in the circuit shown in Fig. 11 (Cancelled) which includes a muting arrangement. The negative rectified carrier voltage from diode 60 is applied through a resistance capacity filter 65, 67 to the control grid 52. The minimum fluorescent area on the anode 59 indicates correct tuning. The coupled circuits 77, 79 connected respectively to the suppressor grid 54 and anode 55 are normally oscillating. The rectification of this oscillation produces a bias in resistance 80 which is applied to the grid of the amplifying valve 68 to produce cut-off. Application of the negative control voltage to grid 52 stops the oscillation and the amplifier is released. This subject-matter does not appear in the Specification as accepted.