Oki Microline 3390 User Manual page 154

Chapter 10: IBM - Standard Functions
10-34
The following commands are suppressed when this command is
used for scaling fonts:
ESC W: double width printing
ESC [ @: character size/line spacing
SI: condensed printing
SO, DC4: double width printing for one line
If a fixed pitch or proportional spacing is selected with this command,
the PROP lamp lights in the CHARACTER PITCH indicator panel
on the control panel.
This command is deleted by selecting a pitch with the commands
DC2, ESC :, ESC g, ESC SI, ESC P Pn and ESC I Pn.
If the printer is reset, this command is similarly deleted and the step
widths for the basic settings apply again.