Electrooptical apparatus

475,008. Copying-telegraphy. STANDARD TELEPHONES & CABLES, Ltd. Nov. 27, 1936, No. 32555. Convention date, Dec. 18, 1935. [Class 40 (iii)] A carrier modulated by image currents and accompanied by the image currents, and unaccompanied image currents are produced, and the two sets of currents are connected differentially. A light beam is modulated by the picture 1 and by a chopping-disc 9 and falls on a light-sensitive cell 12, and part of the light is deflected to a cell 13 by a semi-transparent mirror in front of the chopping - disc. The cells are . connected differentially to an amplifier 18, thus neutralizing unmodulated image currents. According to a modification, the cells are coupled respectively to co-planar grids in a four-electrode valve, Fig. 2 (not shown).