Epson AcuLaser C4000 Reference Manual page 206

Form
Selects the number of lines for the selected paper size and
orientation. This also causes a line spacing (VMI) change, and the
new VMI value is stored in the printer. This means that later
changes in Page Size or Orientation settings cause changes in the
value, based on the stored VMI.
Source SymSet, Dest SymSet
Available only in certain locations where printers are sold with a
special ROM module installed to handle specific languages.
CR Function, LF Function
These functions are included for users of particular operating
systems, such as UNIX.
Tray Assign
Changes the assignment for the paper source select command.
When is selected, the commands are set as compatible with the
HP LaserJet 4. When
compatible with the HP LaserJet 4000, 5000, and 8000. When
selected, the commands are set as compatible with the HP LaserJet
5Si.
194 Functions of the Control Panel
is selected, the commands are set as
is