Canon 2/3 Hole Puncher Unit-A1 Service Manual page 31

4. In precision priority mode, the paper moves by a given amount from where the punch inlet sensor (PS301) detects the trailing
edge of the paper and switches back. The paper is fed to the position where it bumps against the paper stopper guide, and
the punch motor (M301) drives to punch the paper.
Punch Motor (M302)
Paper
25
Cam (Punch)
Paper Stopper Guide
Punch Inlet Sensor
(PS301)
Paper Stopper Guide
2. Technical Explanation