| 摘要 |
<p>A picture level control for a color television receiver 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 can be used either to control the feedback amplifier in the color burst automatic gain control (AGC) circuit or 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 counter-acting intended picture level variation. The picture control can be positioned in the receiver to control the compositive video signal before the chrominance and luminance information are separated or after separation to control respectively the luminance and chrominance information.</p> |
