| 摘要 |
<p>PURPOSE:To detect the end position of recording information accurately by counting a dropout detection signal by a counter circuit during fast reproduction and outputting a blank detection signal when a dropout of information extends for longer than a specific time. CONSTITUTION:A dropout detecting circuit 16 detects a state in which an FM signal level is lower than a threshold value and its detection signal is inputted as a count-up signal to the 1st counter 19 through an LPF17 and a waveform shaping circuit 18. A head switch pulse HSW is inputted to the reset terminal of the counter 19 through a frequency dividing circuit 21 and a pulse shaping circuit 22. This circuit 22 shapes the waveform of the input signal to vary the duty ratio to send an output equivalent to a dropout detection pulse to a pulse generating circuit 23 and a counter 24 as a reset pulse. Then the most- significant digit MSB outputs of the counters 19 and 24 are supplied to an exclusive OR circuit 26, whose output is sent to a CPU as a blank detection signal.</p> |
