Xerox PHASER 5400 User Manual page 64

At the printer:
If your printer driver doesn't include duplex mode, you can select it on
the printer's control panel. However, all jobs sent to the printer are
then double-sided unless they are sent using a printer driver that
specifically says to print the job single-sided. (The driver setting
always overrides the control panel setting.)
8. On the Xerox Phaser 5400 control panel, select duplex printing:
a. Press the Menu keys (labeled 1 or 5) to scroll to the
System
b. Press the Item keys (labeled 2 or 6) to scroll to Duplex.
c. Press the Value keys (labeled 3 or 7) to scroll to either
Long Edge or Short Edge. Refer to the figures on page 49 to
determine this value.
d. Press the Enter key (labeled 4).
e. Press the On Line key (labeled 0) to exit the menus.
48
Menu.
Xerox Phaser 5400 Laser Printer