| 摘要 |
PURPOSE:To detect the remaining amount of a tape in any mode without reference of the rotation state of a reel by measuring rotational periods of a payoff and a take-up side reel. CONSTITUTION:Payoff and take-up side reel pulse detecting circuits 4 and 9 detect rotation pulses of frequencies corresponding to rotating speeds. Those pulses ar frequency-divided by frequency dividing circuits 5 and 10 and gate pulse generating circuits 6 and 11 generate gate pulses for setting time intervals. The rotation pulses detected by the detecting circuits 4 and 9, on the other hand, are converted by voltage converting circuits 17 and 18 into a voltage corresponding to the frequencies, so that a clock outputted by a voltage-controlled oscillator 21 varies in frequency with a superposition and its correction output. Even when the reels vary in rotating speed and then a pulse for gate opening and closing supplied to one input terminal of a counter varies in width, a time pulse supplied to the other input terminal also varies in frequency, so the remaining quantity of the tape is detected invariably when the reels rotate. |
