LP 1  (260-1150)                   Buffer              Faxback Doc. # 5653

The printer contains a line buffer which allows parallel data to be 
received at rates up to 75,000 characters per second.

Basically, all printer functions can be grouped into one of two categories:
(1) character printing, and (2) paper motion.

CHARACTER PRINTING

Line Printer characters are printed by selectively activating the seven 
print wires aligned  in a vertical column in the print head. As the print 
head moves across the paper, the appropriate print wires are momentarily 
activated driving them against the ribbon,  paper and platen to from the 
specified dot pattern.

The print commands to the seven print wires are developed by the read-only
memory (ROM). A variety of character sets are obtainable simply by changing
the ROM. Each character within a ROM is addressed by a 7-bit character code
and each column within a character is specified by timing signal internal 
to the printer.

The print head and ribbon cartridge are attached to the carriage assembly. 
By activating either of the two carriage solenoids, the carriage attaches 
to a continuously rotating band. Activating the forward carriage solenoid 
attaches the carriage to the upper half of the band and moves the print 
head in the forward (left and right) direction. Activating the reverse 
carriage solenoid, attaches the carriage to the lower half of the band 
and moves the head in the reverse direction.

PAPER MOTION

Paper can be moved manually by pushing in and rotating the platen knob, or
automatically by performing a line feed operation.

Power from the drive motor is applied via a line feed clutch to the platen
and forms handling mechanism (pinch roller or tractor) drive gears. Paper 
is advanced one line by momentarily activating the paper motion solenoid 
in the line feed clutch, allowing the drive gears to turn and advance the 
paper by one line.

SPECIAL FUNCTIONS

In addition to printable character codes, the printer also recognizes four
special control codes and the printer action performed upon receiving these
codes.

(dtc-08/04/93)