CITIZEN CBM-710 - Manual (Page 15)

CBM-710/720 Service Manual
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6. Paper End Sensor Circuit
Fig. 6-1 shows the paper end sensor circuit. The reflection type photo-interrupter is used as a sensor. When some
paper is still left, the light reflected by paper strikes upon the photo-transistor; thus, the collector of the photo-
transistor is L. When paper becomes short, no light is reflected, causing the collector to go H. As a result, the CPU
input port P40 becomes H, going into the paper end state.
Control Circuit
Vcc
Paper End Sensor
PHI 1
R12
R13
C11
R14
R15
Tr3
P40
CPU
Fig. 6-1 Paper End Sensor Circuit