Ricoh C7528 Setup Manual page 77

Installing Options
G
Align the notch of the user account enhance unit, and then insert it into
the controller board, pressing it down until it clicks into place.
H
Make sure that the user account enhance unit is firmly connected to the
controller board.
I
Align the controller board with the top and bottom rails, and then push
it in using the part marked "PUSH" until it stops.
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