| 摘要 |
PURPOSE:To remove misdetection by clipping an RF signal at the 1st prescribed level, controlling the ratio of the amplitude of the RF signal to the 1st prescribed level so as to be a prescribed value and extracting a high frequency component over prescribed frequency from the clipped RF signal. CONSTITUTION:If an RF signal (a) is defined as a signal obtained by superposing and recording audio and video signals and a PCM signal, the upper peak level may be reduced to a value less a center level Vo. When the RF signal (a) is supplied to a clip circuit after being fixed at its amplitude, a part exceeding a clip level Vc is clipped and the clipped signal (h) is supplied to a high frequency extracting circuit 12 to remove a low frequency component consisting of a PCM signal or the like and obtain a signal (i). When the signal (i) is supplied to a limiter amplifier 4, the generating period of respective pulses forming an output (c) of a multiplier 5 is made longer than a period corresponding to the frequency of a video FM signal component in a section T3 and a detecting signal (e) is generated. Consequently, misdetection due to superposed recording of a PCM signal is prevented and the drop-out can be stably detected. |
