Brother DCP6690CW Service Manual page 104

After the paper reaches the paper feed roller (rotating counterclockwise), the paper pull-in
rollers keep rotating clockwise. This assures paper buckling to separate the paper from the inner
chute, preventing paper from lifting from the platen. This concurrent drive continues until the
leading edge of the paper comes under the star wheels on the CR support chassis.
In duplex printing, the machine performs backward registration for the SB paper. After the SB
paper is fed to the platen by the concurrent drive of the paper pull-in rollers (clockwise) and the
paper feed roller (counterclockwise), the paper feed roller rotates clockwise to feed the paper
back until its leading edge becomes released from the paper feed roller. This is called
"backward registration." After that, the paper feed roller rotates counterclockwise to align the
leading edge of the paper.
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