| 摘要 |
PURPOSE:To facilitate a countermeasure to the case that the video signals only of synchronizing signals, video signals only of picture signals, and entire video signals are absent by detecting the presence or absence of the synchronizing signals, difference signal between the video signals and the synchronizing signals, or the alternating components of the video signals. CONSTITUTION:A synchronizing separator circuit 14 separates the synchronizing signals from the video signals, and outputs the synchronizing signals. A comparator circuit 24 searches the difference between the delayed video signals and pulse signals, the presence or absence of this difference signal is detected by a first detecting circuit 25, and the first detection signal is delayed by a first delay circuit 26, and outputted through an output circuit 27 from a first output terminal 21. Moreover, the first detection signal is applied through the first delay circuit 26 to a first display circuit 28, and the detected result is displayed. Next, the pulse signal is applied to a second detecting circuit 29, the presence or absence of the pulse signal is detected, and the second detection signal is transmitted by the second detecting circuit 29. Then, the video signals are detected based on the first and second detection signals. |
