| 摘要 |
PURPOSE:To accurately display the remaining time of a magnetic tape by displaying and converting the remaining time of a magnetic tape corresponding to one rotation time of a reel of the magnetic tape or the rotational frequency of the reel in a determined time. CONSTITUTION:The time necessary for one rotation of a take-up reel 2 is detected by means of a light-emitting diode or a magnet system. And, the remaining time of the magnetic tape 3 is preliminarily set in a storage circuit 9 corresponding to the time necessary for the one rotation counted by a rotational time detecting circuit 8 and to the take-up time of the tape 8 that is taken-up. Thus the rotational speed of the reel 2 is detected, and simultaneously, the remaining time corresponding to the results of the above-mentioned actions is calculated by a storage circuit 9. The resulted remaining time is converted to a digital value and displayed. Then the remaining time is displayed on a remaining time display circuit 10. Thus, the device is constituted of the circuits 8, 9 and 10. Since the speed of the tape when passing a magnetic head is constant, the one rotation time of the take-up reel 2 or its rotational frequency in the determined time is detected, and the remaining time corresponding to the result of this detection is calculated by the storage circuit. In such a way, the remaining time can be counted accurately.
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