Xerox PHASER 340 User Manual page 14

PostScript
Click the PostScript tab to see the following options:
The PostScript header contains important PostScript information
that must accompany each print job; it is not a banner page
printed with each job. If an option is not selected, an error
message is displayed on your computer screen and your job does
not print. Click one of the following in the PostScript header
field:
Select Download header with each print job. This option
downloads PostScript header information with each print job.
Click the Send Header Now button to save the PostScript header
information in the printer, then select the Assume header is
downloaded and retained option. This option makes print files a
little smaller and faster than the first option, but you need to click
the Send Header Now button every time the printer is turned off
or reset.