IBM 6400-I15 Maintenance Manual - Page 36

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. Direction of Shuttle Movement Dot Row Start 1 2 3 4 One Text 5 6 Line 7 8* 9* * 10 11 Number of rows determined by line spacing n 1 2 Paper Feed Direction * This row is used only for lowercase descenders ** This row is used for underlining and lowercase descenders Figure 9. Standard Character Formation 36 Principles of Operation