GB236915A - Improvements in or relating to electric discharge devices - Google Patents

Abstract

236,915. Westinghouse Lamp Co. (Assignees of Lederer, E. A.). July 9, 1924 [Convention date]. Copying telegraphs; thermionic relays. - A lighting tube suitable for use in the telegraphic reproduction of pictures with or without wires is provided with ionizing electrodes, one o which is of small area so as to restrict the ioniz ing current. and with means for producing a positive column glow discharge. The ionization may consist of a wire 3, Fig. 1, wound helically about a leading-in wire 6, and of a surrounding tube 4. These are situated within a constricted part of an inner tubular chamber 2, above the open end of which a cathode 5 is held by clips 13. A central hole in the disc-shaped electrode 5 allows light from the positive column to issue. The electrodes may be of aluminium, and may be coated with an alkali metal which is distilled from a side-tube 15<1> after sealing the container Suitable gaseous media are helium and neon preferably at a pressure below 12 mm. of mercury. Two of the leading-in wires 6, 7 are surrounded by separate tubuLar extensions 8 of the chamber 2, to prevent stray discharges. In another construction the ionizing electrodes consist of a plate and a flat spiral, and the cathode is a cylinder surrounding the chamber, which is constricted at its upper end. Variation of the luminous intensity may be produced by varying either the ionizing current or the main current. Thus, the cathode 5 may be connected to one of the ionizing-electrodes 3, 4 by a battery furnishing a steady current, while the ionizing-electrodes are connected through a microphone and a battery. In another arrangement, current flows from a positive main 23, Fig. 4, to one ionizing- electrode 4, through the tube to the main electrode 5, and thence to the anode 25 of a thermionic valve, the cathode of which, like the ionizing electrode 3 of the luminous tube, is connected to the negative main 23. The grid 27 of the valve is maintained at a lower potential than the anode 25 by a battery 26. between which and the anode a microphone 20 is connected. For controlling the luminous tube in accordance with current variations transmitted by wireless telegraphy, the circuits of the luminous tube and anode of the valve are as shown in Fig. 4, but the grid 28, Fig. 5, is connected so that the valve acts as a detector.