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THEORY OF OPERATION
3-3. Detectors
(1) Paper-Out Detector
The paper-out detector is located at the paper entry slit. The detector consists of a reflective photosensor. The
photosensor’s phototransistor remains ON while paper is present. It goes OFF when paper runs out, generating
output of a paper-out signal.
(2) Black-Mark Detector
This detector senses black marks indicating print start positions. The detector is useful only with specially marked
paper. Like the paper-out detector, the black-mark detector consists of a reflective photosensor. The photosensor’s
phototransistor goes OFF when a black mark appears.
Fig. 2-15 Paper-Out Detector Fig. 2-16 Black-Mark Detector
(3) Label Detector
The transmissive detector is used to detect print-start positions for labels. It operates by detecting the difference
in light transmission between backing-only and backing-plus-label portions of the paper.
Fig. 2-17
Fig. 2-18 Label Detector
GND
+5V
R
R
GND
+5V
R
R
Paper
(Reflective photosensor)
Detection signal Detection signal
Paper
Black mark
(Reflective photosensor)
Light
Light
Backing paper
Quantity of
transmitted light
Quantity of
transmitted light
5V
Paper
Label paper
Detection signal
GND