Coherent provides font width tables for a 10 pt times roman
font in regular, bold and italic.  Presumably this font is
available at all laserjets.  The deskjet 500, however only
provides a 12 pt cg times font (very similar to times roman)
and some assorted fixed space fonts.

The solution to this problem is to use fwtable on downloadable
fonts for a laserjet to generate the appropriate font width
tables for use with a deskjet 500.  Clear as mud?

At the end of this message are uuencoded versions of two such
font width tables:
tr120rpn.usp -- 12 pt times roman (close enough to cg times)
lg120rpn.usp -- letter gothic 
Use uudecode to recreate these tables and copy the resulting
files to /usr/lib/roff/troff_pcl/fwt

Allan
