IBM 6400 Maintenance Information Manual page 36

Chapter 4
Line Matrix Printing
When the shuttle reaches the end of a sweep, it reverses direction, the paper
is advanced one dot row, and the hammers print the next row of dots as the
shuttle sweeps in the opposite direction. After a line of characters is printed,
hammer action stops and the paper advances to the first dot row of the next
print line. The number of dot rows allowed for line separation depends on the
vertical line spacing the user selects.
The dot matrix patterns of text characters vary according to the font the user
selects. For example, in the data processing (DP) font at a line spacing of six
lines per inch (lpi), a dot matrix contains 12 dot rows from the top of one
character line to the top of the next. (See Figure 8 and Figure 9.) At eight lpi
there are nine dot rows per character line, at nine lpi eight dot rows per
character line, and so on.
Each individual hammer spring forms more than one character as the shuttle
moves horizontally. This principle is illustrated in Figure 10.
One
Text
Line
36
Direction of Shuttle Movement
Dot
Row
Start
1
2
3
4
5
6
7
8
*
9
* *
10
Number of rows determined by line spacing
11
n
1
2
* This row is used only for lowercase descenders
** This row is used for underlining and lowercase descenders
Figure 9. Standard Character Formation
Paper
Feed
Direction