GB318565A - Improvements in systems and apparatus for television - Google Patents

Abstract

318,565. Pollak, J. E., (Associated Telephone & Telegraph Co.). June 1, 1928. Vacuum tubes.-In television apparatus employing cathode rays for scanning in transmitting and receiving, the end of the cathode ray tube 4, Fig. 1, at the sending station is closed by a photoelectric plate 3, Fig. 3, made of insulating material and coated on both faces with a lightsensitive material 40, 41 such as selenium or potassium hydride. Embedded in the front and back faces are grids 38, 39 respectively, which form the terminals, and extending through the plate are insulated conductors 37. The resistance of the coating on the front or image side varies with the intensity and colour of the light, and the circuit from a battery 15 is completed across the inner face by the cathode ray rendering the coating 41, at any point being scanned, conductive between the ends of the conductors 37 and the grid 39. The grid elements may be spaced apart from the faces of the insulating body of the plate, the front grid 38 however being embedded in the coating 40. The plate 3 may be made by winding insulated wire on a flat coil form, coating the whole with synthetic resin, and cutting through transversely to the wire. Or a number of thin glass strips wound with wire may alternate with plain glass strips, the whole then fused and coated with lowmelting glass, and the exposed edges of the wire ground away. The current in the circuit 15, Fig. 1, is transformed and amplified, and may be transmitted by wire or radio. The end of the receiving cathode tube 22 is a fluorescent screen or photographic plate 23. To ensure synchronization, the two frequencies applied to the electrostatic deflecting plates 11, 12 and 28, 29 are supplied from the same generators 13, 14.