GB595937A - Cathode ray receiver - Google Patents

Abstract

595,937. Copying-telegraphy. FINCH, W. G. H. July 10, 1945, No. 17569. Convention date, March 25, 1944. [Class 40 (iii)] In a facsimile receiver signal-modulated light is obtained from an electron ray tube of the "tuning-eye" type. A mask 92 (Fig. 2) has a perforation 93 covering one half of the no-signal shadow area of an electron ray tube. Received picture signals are applied to the triode grid of the tube to cause the fluorescent area 16 to increase. Thus the edge 118 of the fluorescence moves into the area of the aperture 93, and the illuminated area visible varies in accordance with the received signal. The no-signal shadow area may be restricted by suitable biassing of the triode grid to the. size of the aperture 93 so that received signals cause both edges of the fluorescent area to enter the aperture. The aperture 93 is optically focussed on to a photographic recording sheet 45 and in order that the light spot on the film may not consist of a dark area together with one or two illuminated areas, the lens system 102 (Fig. 1) may be arranged slightly out of focus. The electronray tube is mounted in a box 51, having the optical system 96 screwed into a tapped hole 95 in its front plate, and this hole covered by the mask 92. The recording film 45 is mounted on a drum 31, rotated by motor 22 which also drives a worm shaft 41 to cause the scanning system 51 to traverse the drum longitudinally. At the end of its traverse, half-nut 53 pivots on a pin 52 and the scanning system may be returned manually or automatically to its start position ready to scan another line.