| 摘要 |
PURPOSE:To prevent an accident, such as the fall accident of a head, or the erasing accident of a bit of storage information on a disk due to the trouble of a parts by detecting that the discriminating phase margin of a gate signal which discriminates a reproduced data clock pulse train to a data pulse train and a clock pulse train is narrowed than a prescribed value. CONSTITUTION:When a head 6, a disk 3, or an other parts is started to operate abnormally, the phases of the data clock pulse trains (x) and (y) of the output (g) from a one-shot circuit 13 is varied as shown in dotted line. Therefore, the discriminating phase margin of a delay time (t) from the data clock pulse trains (x) and (y) to the complementary output (h) of a VFO circuit 14 is narrowed than the prescribed value of a phase margin detection circuit 18, and the output (m) of the phase margin detection circuit 18 is outputted. When the output (m) of the phase margin detection circuit 18 is sent to an electronic computer, the computer issues a command instantly, and reproduces a bit of information from the disk, and stores the bit of information at other storage device, before the head 6 falls on the disk, or the parts breaks down by another cause.
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