
7 - 17 SCANNER
Supplementary comments
• Concerning the reflecting photointerruptor:
The reflecting photointerruptor consists of an infrared diode and a phototransistor. It detects
originals by use of pulse modulation.
The light emitting diode (LED) is driven by pulses with a period of 130 msec. If a signal which has
the same characteristics is received by the phototransistor, an original is determined to be present.
Pulse modulation is performed within the reflecting photointerruptor.
Original
Phototransistor
130µsec
LED
8µsec
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