| 摘要 |
PURPOSE:To prevent malfunction at reading, by displaying a frame so as to surround a character pattern only in a short time, in depressing a light pen on a screen. CONSTITUTION:An output signal from a CRT controller 2 is transmitted to a CRT display via a switch 5 at normal operation. In depressing the light pen 7 on a CRT display screen, a switch signal 14 is generated and the switch 5 changes over a signal given to the CRT display 6 to a pattern signal 15. The pattern signal 15 displays a frame on the CRT display screen. A timing signal is generated from the light pen 7 in receiving the light emission of this frame and the position is read. Even if the light pen 7 is depressed between characters, the position is detected accurately with the frame display. Since the frame emits light, the erroneous reading from adjacent light emission is prevented. |
