Experimental television transmitter
14 January 1937
Describes a film scanner designed for easy operation and maintenance, and for variable definition. The film moves vertically at constant speed, and is scanned by the horizontally-moving spot in a simple kathode-ray tube. To increase the screen life, the spot scans a surface of adjustable height. After-glow is reduced to about 1 musec. Since its wave-length is 6000 A, whereas the first glow is at 5400 Aring, its effect can be reduced by using a selective photo-cell. This unfortunately involves a poorer sensitivity (10 muA/lumen). The phot-cell coupling to the amplifier, and the noise problem, are briefly analysed.