| 摘要 |
A digital fine tuning system for a television receiver includes a counter arrangement for measuring the frequency of the IF picture carrier by counting cycles of the IF picture carrier during a measurement interval and comparing the count at the end of the measurement interval to a predetermined count related to the nominal frequency of the IF picture carrier. To prevent counting, and thereby frequency measurement errors, due to the overmodulation of the picture carrier during image intervals, the frequency measurement operation is enabled during a predetermined portion of the vertical retrace interval when the picture carrier is not overmodulated.
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