GB439225A - Improvements in or relating to electro-optical image transmission systems - Google Patents

Abstract

439,225. Television. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Gray, F.; 18, West 76th Street, New York, U.S.A.) May 17, 1935, No. 14470. Convention date, May 19, 1934. [Classes 40 (iii) and 40 (v)] A cathode ray beam scans a screen, the lines of successive scans being displaced by an electrical biassing arrangement. As applied to a receiver, line synchronizing signals control a valve 13 discharging the condenser 14 of a relaxation oscillator supplying the line deflecting voltage. The line synchronizing signals are also fed to a subharmonic producer 17 and the frame frequency is selected by a filter F and supplied to two valves 20, 21 in push-pull and alternately discharging the condenser 22 of the frame frequency relaxation oscillator. The valve 20 completely discharges the condenser 22, but the valve 21 only reduces the potential of the condenser 22 to that of the battery 25, so that alternate scans are displaced on the screen s and the lines of one scan. overlap those of the preceding scan. The line synchronizing signals are preferably modulated onto a sub-carrier wave which is then mixed with the picture signals and the combined signal modulated onto a transmission carrier wave, Fig. 2 (not shown). Where the combined pictures and modulated sub-carrier wave overlap the frequency range of the channel, the modulator acts as an amplifier for the signals and the lower side band is distorted. The upper side-band is then selected and modulated onto the transmitting carrier wave. Specification 295,930, [Class 40 (v)], is referred to.