Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!apple!agate!shelby!unix!hplabs!hpfcso!hpfcdc!rer
From: rer@hpfcdc.HP.COM (Rob Robason)
Newsgroups: comp.sys.hp
Subject: Re: HPGL on the HPLaserjetIII
Message-ID: <5570550@hpfcdc.HP.COM>
Date: 14 Dec 90 00:09:43 GMT
References: <15737.27637b0d@ccvax.ucd.ie>
Organization: HP Fort Collins, Co.
Lines: 2

You probably need to prepend some escape sequence to the data to get the
printer into plot mode.  That should be documented in the manual.