| 摘要 |
A dual-standard display system with a common light pen has a raster-scan display TD and a cursive display CD, each with its own display drive circuit RD and LD respectively. A single light pen LP is connected to a switch control SC responsive to the repetition rate of light pen output signals. The switch control operates a switch SM to connect the pen output signals to the appropriate one of the two display drive circuits. The switch control SC may include a "window generator" comprising a counter, a decoder and a line-frequency clock generator. A gate responsive to the output of the window generator and to the output of the pen causes a monostable to assume its unstable state and to operate switch SM thus connecting the output of the pen to a raster-interrupt circuit RI whenever the pen is applied to a raster-scanned image. Otherwise the output is connected to the cursive-interrupt circuit CI. <IMAGE> |
