Centronics 101AL Technical Manual page 15

1.3.2 PAPER MOVEMENT
Paper can be moved manually by rotating the platen knob (shown in
Figure 1-5) or automatically by any of three paper movement commands: Tine
feed, vertical tab and form feed.
PAPER
ADVANCE
FORM FEED
(RELEASE)
CLUTCH
FORM FEED
HOLE
Figure 1-5. PAPER MOVEMENT
A small independent motor not shown in Figure 1-5, provides the power
necessary to move the sprocket-feed tracotrs which control paper movement.
To move the paper, the printer electronics activates a line feed solenoid
which activates a clutch that mechanically links the motor to the sprocket-feed
tractors.
To initiate a single line feed, the line feed solenoid is energized
for 15 milliseconds to initiate paper motion. Upon completion of the line feed
command, a 60 millisecond delayed line feed is generated. This allows the
clutch pawl and clutch mechanism to return home before another line feed is
allowed.
Vertical forms movement is accomplished hy applying a DC level to the
paper feed solenoid until a hole is detected in the Vertical Format Unit (VFU).
The tape consists of two tracks; one used for Top of Forms and the other for
Vertical Tab. The movement of the paper tape is caused by direct mechanical .
linkage to the gear train which drives the paper feed tractors.
When the printer runs out of paper, a sensing switch activates a
two-second audible tone in a speaker located at the rear. The printer also
Stops printing and lights the PAPER EMPTY light on the control panel.
1-5 Rev. C