| 摘要 |
PURPOSE:To reduce the circuit in scale of a drop-out detector by providing a track selection means which selects the output signals of plural tracks and comparing the selected track output signal with the reference voltage. CONSTITUTION:A track selection part 10 selects the output signal of an amplifier 3 or 4 by the track selection control signal supplied from a signal generating part 9. The selected output signal is supplied to a wave detection part 5A and converted into the DC voltage proportional to the signal amplitude. The new input signal is supplied every cycle T/2 to the part 5A from amplifiers 3 and 4 respectively. At the same time, the control signal needed for a switch part 5d to constitute a closed circuit is supplied to the part 5A from the part 9 every cycle T/2 synchronizing with the track selection control signal and just in a short time. The output voltage of the part 5A is compared with the reference voltage of a reference voltage generating part 7a through a comparison part 7A. Thus a drop-out state can be outputted to output terminals 11c and 11d of a signal distribution part 11. In such a way, the circuit scale of a drop-out detector is reduced. |
