| 摘要 |
PURPOSE:To attempt common use of capstan servo loop by selecting the frequency of capstan rotating signal in normal state in a specific value, and changing the ratio of frequency dividing to specific relation according to the frame frequency of video signal. CONSTITUTION:Capstan rotating signal frequency fb is selected to be fb=150M (M:a positive integer) under normal state, and the dividing ratio of frequency divider is chosen to be 1/5M when the frame frequency is 30 Hz, and 1/6M when it is 25 Hz. Therefore, a scale-of-32 counter 9 works as a scale-of-25 counter when switch 13 is closed at contact (a) side to divide the capstan rotating signal selected at 750 Hz under normal state into 30 Hz by 1/25 dividing, and works as a scale-of- 30 counter when the switch 13 is closed at contact (b) side to provide 1/30 frequency division to change to 25 Hz, thereby outputting each frequency to a phase comparator 8. Thus, when recording or reproducing video signals of either frame frequency, the same servo loop may be common used. |
