| 摘要 |
PURPOSE:To display the amount of a tape to be used in detail without any control signal on a tape by counting the number of revolutions of a rotary head and using a pulse signal to correct the counted value. CONSTITUTION:One pulse signal is obtained from a level comparator 6 when an output signal level of an envelope detection circuit goes to a prescribed level or over. A RF switching signal from an input terminal 11 is supplied to an edge detection circuit, and an edge detection circuit 12 detects the leading edge of the RF switching signal. A rotary pulse signal at each revolution of a drum fitted with rotary heads 1, 2 is obtained from the edge detection circuit 12 and supplied 1 to a microcomputer 10. Further, a mode signal such as reproduction mode or fast rapid traverse mode is supplied to the microcomputer 10 from a mode signal input terminal 13. Thus, the tape speed at reproduction is judged by the microcomputer 10 based on the tape speed at normal reproduction, the amount of a tape to be run is calculated and the display of a display device 14 such as hour/minute/second is changed.
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