| 摘要 |
PURPOSE:To detect stably the position of a display character, by providing specific brightness adjusting circuit, flip-flop, and AND gate to display characters on a cathode-ray tube with a constant brightness when a light pen is used. CONSTITUTION:Brightness adjusting circuits 12 and 13 which are interlocked with a variable resistor 7 for contrast adjustment of display characters to display characters with an approximately constant brightness when a light pen 9 is used, and FF15 where the switch signal of the light pen 9 is stored, and an AND gate 16 to which the output of the FF15 is inputted to control the detection signal output of the light pen 9 are provided. When the light pen 9 is not used and after a character position is detected by the light pen 9, brightness adjusting circuits 12 and 13 are switched to a normal display brightness adjusting circuit 11. For example, this switching is performed by a switching circuit 14 using a relay or an analog switch. |
