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Figure 8-1 shows an enlarged schematic view of the front of
the printhead, showing the ends of the wires and their relation-
ship to the draft characters. As you can see, the capital letters
use the top eighteen wires of the printhead, and the descenders
(such as the lower case “p” shown) use the bottom eighteen
pins. As the printhead moves across the page (in either direction
- that’s what is meant by bi-directional printing) it prints one
column of dots at a time. Each time a dot is supposed to print an
electromagnet inside the printhead causes the appropriate wire
to strike the ribbon (making this printer an impact printer).
3
O0
O0
O0
O0
O0
O0
O0
O0
0
OO
OO
?igure 8-l. As the printhead moves across the page, each of the
wires prints one row of dots.
THE PRINT MATRIX
All of the standard characters that this printer prints are form-
ed from patterns of dots that are permanently stored in the
printer’s ROM (read-only memory). This includes all of the
standard ASCII characters, and special characters, the interna-
tional character sets, and the LQ characters.