| 摘要 |
This invention concerns an indication circuit that indicates letters on the present screen. This invention specially concerns an indicating circuit that uses a video memory system to merge the letter data and the picture data and project the image on the displaying system. The objective of this system is to simply indicate the desired characters without damaging the clarity of the picture. This system is made of a micom (109), a door phone (30), a video camera (116), a pattern data read/write horizontal counter (122) and a vertical counter (126), an A/D converter (110), a D/A converter (113), a two-way buffer (115), a derivative circuit (120) and an analog switch (119). |
