Minolta Di 620 Manual page 107

<Paper Separating Mechanism>
The paper separating mechanism employs a torque limiter to ensure that only the
top sheet of paper is fed in by separating the second sheet of paper from the top
one.
This is accomplished by the difference in friction coefficient between the Feed and
Separator Rolls.
<Normal Feeding>
Feed Roll
Paper
Separator Roll
<Double Feeding>
Feed Roll
1st sheet of Paper
2nd sheet of Paper
Separator Roll
Stationary
Driven
4425M012AA
4425M013AA
M-88
When only one sheet of paper is taken up,
the friction coefficient on the top side of the
paper is equal to that on the underside.
Driven by the Feed Roll, the paper drives
the Separator Roll, allowing the paper to be
fed into the Vertical Transport Section.
Since the friction coefficient between the
second sheet of paper and the Separator
Roll is greater than that between the first
and second sheets of paper, the Separator
Roll is not driven and holds the second
sheet of paper. The Feed Roll thus feeds the
first sheet of paper into the Vertical Trans-
port Section.