Xerox 4635 Operator's Manual page 314

BAR CODE OPERATING PROCEDURES
14-6
Note: If the center of a landscape bar code falls beyond 13
inches at the top of a document, set the read head to 13 inches
on the scale. If the center of a landscape bar code is less than 1
inch at the bottom of a document, set the read head to 1 inch
on the scale. The beam length is more than sufficient to read to
the edge of the document. Attempts to move the read head
beyond 13 inches or less than 1 inch in landscape mode will lead
to damage of the positioning mechanism.
XEROX 4635 LASER PRINTING SYSTEM OPERATOR GUIDE