| 摘要 |
The video signals transmitted from cameras of CCTV system are changed by digital signal of a microcomputer without fluctuation of screen of CCTV, generated when screen is changed. The circuit includes autoselection and manual selection switches (PB1-PB5) for selecting cameras, analog switches (G1-G4) for selecting video signals transmitted from a selected camera, a synchronous signal divider (1) for extracting horizontal and vertical synchronous signal from a selected video signal, a microcomputer (6) for generating character signal and blanking signal, and a switch (SW1) controlled by the blanking signal for displaying video signal and character. One video input signal is changed by another video input signal at the rising edge of vertical synchronous signal.
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