Canon FY8-13FW-000DADF-A1 Service Manual page 29

4. Detecting the Number of Originals
The number of originals is detected in
terms of "stack end detection," "last original
rear edge detection," and "original count
detection."
a. Detecting the End of a Stack
The machine picks up and delivers
originals on the same tray, requiring distinction
of originals that have been copied from
originals that have not been copied.
Before picking up originals, the re-
circulating lever is placed on top of the stack.
The lever will drop on the original tray when
all originals have been picked up, enabling the
re-circulation sensor (S14) to identify the last
original and to generate the last original
detection signal (RSS).
DADF controller PCB
Recirculating lever
DADF controller PCB
Re-circulating
lever
Figure 2-210
COPYRIGHT © 1998 CANON INC.
Re-circulation
sensor (S14)
Original
Re-circulation
sensor (S14)
CANON DADF-A1 REV.0 DEC. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 2 BASIC OPERATION
b. Detecting the Trailing Edge of the Last
Original
A copier with a long paper path (from the
cassette to the drum) is designed to pick up
copy paper early to speed up copying work. As
such, when the machine picks up the last
original and places it on the copyboard glass,
the next paper is likely to be kept in wait.
To accommodate this, the machine is
designed to pick up originals to suit the timing
at which its host copier picks up copy paper.
If the length of an original is 220 mm or
less, the machine sets the first original on the
copyboard glass, and moves the second
original beyond the registration roller.
Recirculating lever
2nd original
Figure 2-211
If the re-circulating lever is on the original
tray in this condition, the machine
communicates to the copier that the third and
subsequent originals are present, and the copier
picks up copy paper for the next copying run.
When the re-circulating lever has dropped
on the original tray, the machine communicates
to the copier that there is not third or
subsequent originals (RSS signal) so that the
copier will not pick up copy paper.
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