| 摘要 |
PURPOSE:To prevent damage of a magnetic tape by measuring continuously intervals of the output of a capstan tachometer to detect involution of the magnetic tape between a capstan and a cover. CONSTITUTION:The output light of an LED11 passes a slit 12 for capstan tachometer rotated by a motor 14 and is received by a phototransistor 13 and is outputted as a capstan tachometer output 15. Intervals T1-Tn of this capstan tachometer output 15 are measured with reference clocks 27 by a counter 20. If intervals of the capstan tachometer output 15 are abnormally longer when an abnormality detection period signal 23 is turned on, a control processor circuit 21 transmits an abnormality detection signal 24 on a basis of the output of the counter 20.
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