| 摘要 |
PURPOSE:To transmit simultaneously a switch signal and a photodetecting signal from a light pen by one coaxial cable by reproducing a switch signal by starting a retrigger monostable multivibrator by an AND output of a horizontal synchronizing signal and an input signal, and reproducing the photodetecting signal from AND of this switch signal and the input signal. CONSTITUTION:A photodetecting signal obtained by a photodetector 10 in a light pen 1 is supplied to an invertor 20 in an output buffer 2 through an amplifier 11 and a comparator 12, and also a switch signal of a switch part 7 is supplied to an invertor 19 through a comparator 9. An exclusive OR circuit 2 synthesizes signals of the invertors 19, 20 and supplies them as a signal E to a level converter 22. The composite signal converted to a prescribed level by this level converter 22 is attenuated suitably by an attenuator 23, and thereafter, transmitted to an input buffer 4 through a transmission line 5. The input buffer 4 separates the photodetecting signal and the switch signal by using a retrigger monostable multivibrator 28, etc., and the photodetecting signal L and the switch signal M are obtained from terminals 31 and 32, respectively.
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