| 摘要 |
PURPOSE:To collectively detect irregular noise, by detecting abnormal signals having excessively wide or narrow amplitude widths which are outside of in amplitude range with a level detecting circuit and deciding the abnormal signals as noise when the count value of reference clocks counted during the detecting period exceeds a prescribed value. CONSTITUTION:A noise detecting circuit 11 detects abnormal signals having excessively wide or narrow amplitude widths which are outside of an amplitude range at a level detecting circuit 13 after clamping video signals whose white peaks and synchronizing leading ends are within the prescribed amplitude range to a fixed level at a clamping circuit 12. When the count value of reference clocks counted by a counting circuit 14 during the detecting period exceeds a previously set prescribed value (n), a deciding circuit 15 decides the abnormal signals as noise. Therefore, abnormal signals whose white peaks and synchronizing leading edges are irregularly outside of the amplitude range are detected without omission regardless of the deviated direction from the range and irregular noise can be detected collectively by referring to the scales of the amplitude and producing periods of the irregular noise.
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