| 摘要 |
PURPOSE:To detect stably a drop-out without erroneous detection by selecting an RF signal subjected to the waveform processing in accordance with the detection of a low frequency information pulse signal overlapped with the RF signal and detecting the drop-out. CONSTITUTION:A low frequency component detection circuit to which a read-out RF signal through an RF amplifier 1 is supplied controls a changeover switch 14 of a waveform processing circuit 12, and the overlapping of a low frequency information pulse signal with the RF signal is not detected. At this time the output of the amplifier 1 is supplied to a drop-out detection circuit of a limiter amplifier, etc., as it is. When the circuit 13 detects the overlapped low frequency signal pulse from the RF signal, the RF signal where the low frequency component for passing through the waveform processing circuit 12 formed with a clip circuit 15, high frequency amplifier circuit 16 and HPF17 is removed is supplied to a limiter amplifier 4. A drop-out is stably detected without an erroneous detection in such a way that the envelope component of the RF signal becomes large and a pickup level will not comes more than and less than a center level. |
