| 摘要 |
<p>In apparatus for reproducing a signal recorded on a magnetic tape or other record medium and which includes a signal band containing an information signal, such as the chrominance component of a color video signal, and a reference signal of a predetermined frequency occurring only during spaced intervals, such as, the burst signal; the mentioned band of the reproduced signal is applied to a variable gain amplifier for controlling the level of the chrominance component, a burst gate receives the level-controlled output of the amplifier and is gated during the intervals of the burst signal to provide an output during each such interval, a crystal filter tuned to the frequency of the burst signal receives the output of the burst gate so as to pass only the burst signal, and the gain of the variable g?in amplifier is controlled in accordance with the combined levels of the outputs of the burst gate and the crystal filter, respectively. In providing the gain control signal for the variable gain amplifier, the outputs of the burst gate and crystal filter may be both level detected and the resulting D.C. voltages then added to provide the gain control signal, or only one of such outputs may be level detected and added to the other output to provide an added signal which is the? level detected to provide the gain control signal. The combined ?evels of the outputs of the burst gate and the crystal filter are also preferably employed to control a color killer circu?t in the reproducing apparatus.</p> |
