Ricoh FT6645 Manual page 115

PAPER FEED 23 April 1993
6.15.3 Paper Size Detection
[C]
[A]
[B]
The paper width detection is necessary to decide the lens horizontal position
because the standard position of the optics (rear left corner) and the paper
(center) is different.
The by-pass paper size sensor [A] (variable resistor) monitors the paper
width. When the paper side fences [B] and [C] are positioned according to the
paper width, the rear side fence is connected to the lever of the by-pass
paper size sensor. The electrical resistance of the sensor changes in
accordance with the side fence position, This informs the CPU of the paper
width.
At the first copy from the by-pass feed table, the scanner makes a full
distance scan. The registration sensor monitors the length of this paper
(between the ON timing by the leading edge and the OFF timing by the
trailing edge). From the following copies, the copier is controlled according to
this paper length data.
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