Ricoh D124 Detailed Descriptions Manual page 74

 The roll feed roller [1] feeds the paper over the feeler of the paper exit sensor [2]
and out of the roll feeder into the vertical feed path of the main machine.
 When the leading edge of the paper reaches the pre-registration sensor [3], the
vertical motor [on the left side of the machine] turns on and rotates the registration
roller [4] and exit roller [5].
 When the DRESS sensor [6]detects the leading edge of the paper, the vertical
motor stops.
D124 68 Detailed Descriptions