Genicom GEK 00031B manual Normal ? character is printed

HT	Horizontal Tab (09H): HT moves the active position to the next
	horizontal tab stop on the same line. If no tab stop exists to the right
	of the active horizontal and within the right margin, HT moves to the
	right margin and sets the Right Margin Flag.
	If no tabs are set and bar code is not active, HT moves the active
	horizontal position to the right margin.
LF	Line Feed (0AH): LF moves the active vertical position down one
	Vertical Advance Increment (VAI). If Line Feed/New Line Mode (LNM)
	is set, the active horizontal position moves to the Line Home Position.
	See the section on the Page Coordinate System later in this chapter.
SI	Shift In (0FH): SI, also named Locking Shift Zero (LS0), maps
	character set G0 as the GL character set.
SO	Shift Out (0EH): SO, also named Locking Shift One (LS1), maps
	character set G1 as the GL character set.
SUB	Substitute (1AH): This sequence aborts the sequence in progress.
	SUB in a control string generally aborts the string in progress. (Need
	a reference to a local equivalent of table 2-2 in the spec.)
	SUB in printable text causes the error character to be printed. The
	error character is taken from the GL font. The error character for most
	fonts is a distinctive reverse question mark. In some instances a
	normal ? character is printed.
VT	Vertical Tab (0BH): VT moves the active position to the next vertical
	tab stop on the current page. If no tab exists between the active
	position and the bottom margin, VT moves the active position to the
	bottom margin. Be aware that this command interacts with
	coordinate system bounds. If no vertical tabs have been set, then VT
	moves the active position to the bottom margin.

Chapter 8. PPL3 Plus Emulation 200 GEK-00029B