GB708088A - Color-television signal-translating system - Google Patents

Abstract

708,088. Colour television. HAZELTINE CORPORATION. Dec. 18, 1951 [Jan. 10, 1951], No. 29630/51. Drawings to Specification. Class 40 (3) In a colour television system wherein there are generated a "monochrome" signal primarily representative of the brightness of the transmitted image and a " colour " signal primarily representative of the colour components of the image, the gain in the colour-signal channel is varied inversely with the amplitude of the " monochrome " signal, so that the colour components are accentuated when the reproduced image is of low intensity. The invention is described as applied to a " dot-sequential " type of system wherein the colour signal is transmitted as the modulation of a sub-carrier lying within the frequency band occupied by the " monochrome " signal, and may be effected either at the transmitter or receiver. At, for example, the receiver, the channel carrying the monochrome signal includes a detector which derives a gain-control signal which is applied to the " colour-signal " channel to control the amplitude of the modulated sub-carrier which is subsequently detected to derive the colour-component signals. In a modification the monochrome signal is passed through two parallel channels, translating respectively the lower-frequency and higher-frequency portions of the signal. The lower-frequency channel is used alone to derive the gain-control signal since this channel does not pass the modulated colour sub-carrier and the control exercised is consequently independent of the colour signals.