| 摘要 |
<p>A circuit for generating a composite keying signal includes a burst gate circuit, a clipping circuit, and a voltage divider, in a color television receiver also including means for deriving horizontal and vertical blanking signals and a horizontal sync pulse from a composite color television signal containing a color burst component. The burst gate circuit responds to the lagging edge of the horizontal sync pulse to develop a burst gate pulse encompassing the burst interval. The clipping circuit and the voltage divider serve to clip and translate both the horizontal and vertical blanking signals, which are then combined with the burst gate pulse to produce a composite keying signal. The composite keying signal comprises a first pulse component of desired magnitude as determined by the clipping and voltage divider circuits and occurring during the blanking intervals, and a second pulse component as provided from the burst gate circuit, superimposed on the first pulse and encompassing the burst interval.</p> |
