GB406672A - Improvements in or relating to electro-optical image producing systems, such as television systems - Google Patents

Abstract

406,672. Television. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Gray, F. ; 243, West 101st Street, New York, U.S.A.) Aug. 31, 1932, No. 24286. Convention date, Sept. 16, 1931. [Classes 40 (iii) and 40 (v).] The suppression of direct-current components in television signals before or during transmission is compensated by a supply of direct current controlled by fluctuations produced in the received signals. The current from the photo-electric cell 7, Fig. 1, fluctuates in a manner indicated by the curve c, Fig. 3, and by scanning a black strip beside the object 6, or by making the aperture 8, Fig. 1, smaller than the width between two apertures 3 in the scanning disc 2, a fluctuation of amplitude I, Fig. 3, is periodically produced which is proportional to the D.C. component. The received signals, Fig. 4, lack the D.C. component and are amplified by valves 13 and 14 and applied to the neon lamp 19. The valves 13, 14 are coupled by a compensating circuit comprising a rectifier 16, a condenser 17, and a high resistance 18. The fluctuation of amplitude a, Fig. 4, is rectified at 16 and the condenser 17 is charged to reduce the potential applied to the grid of the valve 14 whose plate circuit is supplied with a corresponding D.C. The resistance 18 allows the charge on condenser 17 to leak away so that the condenser is recharged by the next signal produced by scanning the black strip. The rectifier 16 may comprise a twoelectrode thermionic rectifier (Fig. 5, not shown). When transmitting on a carrier wave, the D.C. components are suppressed in amplification and are replaced by a compensating circuit identical with that of Fig. 1, before modulation (Fig. 6, not shown).