| 摘要 |
PURPOSE:To obtain the margin of a timing where inconvenience does not occur in a clock switching point with simple constitution by controlling a boundary between a period with phase modulation on the clock and that without phase modulation by means of a switching circuit in correspondence with a reference clock. CONSTITUTION:A clock phase modulation circuit 1 corrects minute fluctuation of the time base smaller than a clock cycle when a reproduced signal of a VTR is A/D converted. A maintenance circuit 31 always maintains the reference clock which is not clock phase-modulated. The reference clock which the circuit 31 maintains is given to a clock switching circuit 32 as a control input. With gating to the size of the clock phase, the circuit 32 controls the boundary between the period with the phase modulation and without it on the clock in the circuit 1. Sufficient margin for the timing at the time of switching is held and satisfactory clock-switching can always be executed irrespective of the size of phase modulation on the clock and without the occurrence of unnecessary edge.
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