Xerox Document Centre 255 LP Reference Manual page 67

System Tools
Tray Priority Settings
The window in this input region will accept values from 1 (highest
priority) to 99 (lowest priority).
Auto Selection
This selection enables the Auto Tray Switching feature which makes
the tray and its pre-programmed contents available when a tray is
selected in the Print Driver.
Disabling this option makes a tray unavailable for Auto Tray
Switching.
Xerox Document Centre Reference Guide Page 6 - 15