OKIDATA ML320 Turbo Service Manual page 42

(5) Pull tractor mechanism (option) (See Figure 2-12.)
Bottom feed of continuous sheets is possible only when the optional pull tractor unit is installed.
The rotation of the platen is transmitted to the idle gear of the pull tractor unit through the platen gear at
the left end of the platen. The rotation of the idle gear is transmitted to the drive gear, and paper is fed
when the sheet feeder shaft turns the pull tractor.
(6) Bottom push feed operation (Option) (See Figure 2-13.)
The bottom push feed of continuous sheet requires the bottom tractor feed unit.
When the platen turns, its rotational force is transmitted through the tractor idle gear and the tractor
change gear to the tractor drive gear of the bottom push tractor, and paper is fed to the print start position.