Two queue on the same printer

[Scagnetto Arjuna]

Hardware and queue config:

Xerox 860 dx (ppd tk860dx1).

We configured two queue one for normal paper printing (queue name xc) and one for slide printing (queue name slide).

The problem:

using lpr -Pslide filename.*

if * = text or pdf then everything works.
if * = ps then the output is on paper instead of slide.

Thanks for answering
Arjuna Scagnetto