Canon GP200 Service Manual page 81

2. Operation of Original Size Sensors
A reflecting type sensor is used under the
copyboard glass to detect the size of an original
placed on the copyboard glass.
When the copyboard cover is brought down to
about 30°, the photointerrupter (PS3) located at
the rear of the copier turns ON, i.e., the light-
blocking plate blocks PS3.
The output level of each sensor is read for 15
sec or until the Copy Start key is pressed after
PS3 has turned ON at intervals of 0.128 sec. The
presence of an original at the sensor position is
assumed if the output level remains unchanged
during the period, and the size of the original is
identified as shown in Tables 3-205 through -208.
This way of identifying the size enables identi-
fication of the size of black originals as well.
In the case of a/b described below, however,
the output level will remain unchanged.
In the case of c described below, on the other
hand, A3 will be selected with priority; if no cas-
sette contains A3 paper, the cassette selected
under standard mode will be selected.
Original
PS3:ON
Original
detection 1
COPYRIGHT © 1996 CANON INC.
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Copyboard
cover
30˚
Copyboard
glass
ON OFF
Original
detection 2
Figure 3-208
CANON GP215/200 REV.0 JULY 1996 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. OPERATIONS AND TIMING
a. A3 black original
b. Book original (The thickness of a book pre-
vents changes in the sensor level.)
c. The copyboard cover is not closed. (PS3 is
OFF.)
Reference:
In the case of a, b, or c, the size may be
detected wrongly.
ON
No
change
in the level
ON
Change
in the
level
3–27