| 摘要 |
PURPOSE:To display an alarm display on a CRT without effecting an object image corresponding to a video signal by superimposing an alarm display signal during the horizontal blanking period. CONSTITUTION:A video signal Sx inputted from a video signal input terminal 10 is amplifier by an amplifier 12, clamped by a clamp circuit 22, and the horizontal blanking period is subjected to blanking processing by a pedestal circuit 24 to set a black level. The video signal Sx subjected to black level setting is mixed with an alarm display signal S4 by a mixer 14. In this case, the display signal S4 is superimposed on the horizontal blanking period. The signal after mixing is given to the CRT 18 via an output circuit 16. The object image is displayed on the CRT 18 within the horizontal video scanning region and the alarm information is displayed in the horizontal blanking region.
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