Abstract: With closed loop control, the hue for a color television receiver is automatically set by means of a received VIR signal. Viewer preference of the hue setting is realized by gated addition of the viewer preference offset voltage into the VIR control loop. The viewer preference signal is added into the control loop on all lines other than the VIR line 19. During line 19 the hue control loop is left undisturbed for the establishment of the reference hue setting.

Abstract: A line selector circuit for a television receiver identifies a predetermined horizontal line. The line to be identified desirably occurs during the vertical blanking interval subsequent to the vertical sync interval contained therein. A line of particular current interest is line 19 which contains reference information which can be used for automatic control of the receiver. The predetermined line is identified through the generation of a timing period which is initiated by a sync pulse synthesized by the summation of horizontal and vertical rate information. The timing period is terminated by horizontal sync information at the beginning of the predetermined line. The timing period is generated by a one-shot multivibrator having a first threshold circuit responsive to the synthesized sync pulse designed to initiate the timing period during the same line in the vertical sync interval of either field.

Abstract: A reference signal contained in the vertical blanking interval of the transmitted television signal is used in the color television receiver for automatic hue and saturation control. This vertical interval reference (VIR) signal includes a chrominance reference portion and a black level reference portion. The chrominance reference portion contains hue indicative information in that one of the color difference signals is zero and saturation indicative information in that one of the color signals is zero. The receiver is responsive to the VIR signal once during the black level reference portion to establish a zero reference for the hue control circuit and for the saturation control circuit. The receiver is responsive to the VIR signal a second time during the chrominance reference portion to set proper hue and saturation by automatically reducing to zero any differences between the indication of hue and saturation obtained from the VIR chrominance reference portion and the established zero references.

Abstract: A picture level control for a color television receiver which simultaneously varies luminance and chrominance signal levels and additionally provides a compensating voltage to prevent automatic color controls from counteracting the intended chrominance variation. The compensating voltage may be used either to control the feedback amplifier in the color burst automatic gain control (AGC) circuit or used to achieve the same result by controlling the gain of the subcarrier oscillator generator when such oscillator is of the type to form part of the burst AGC circuit. In addition, the compensating voltage is applied to the chroma averaging AGC circuit when such is included in the receiver to prevent the chroma averaging circuit from counteracting intended picture level variation.