Today he writes me with this update:
Thanks to a wonderful individual in Baltimore, Md., I have received a copy of the GP 2106 User's Manual which has appendices that have handshaking, emulation and other physical/supply information. Great! This gets me halfway to my restoration goal.
The Plotter manual comes in two parts, though: the User's Manual and the Command Set Reference Manual. If you can help me find the Command Set Reference Manual (GP 2106-UM-351, any condition), that would be excellent.Mr Anderson may be closer to a solution than he realizes, as I wrote back to him:
Many plotters used emulation, ie mimicked the command sets of established brands. Three most common in the 1980s were (in order of popularity):
1. Hewlett-Packard (HPGL)
3. Houston Instruments
Emulation was implemented in two ways:
1. Directly -- you hooked up the plotter to the computer, and then used an HPGL driver (still supported by AutoCAD in 2010).
2. Indirectly -- the plotter had its own command codes, but also supported HPGL. In this case, however, you would have to tell the plotter to switch to HPGL, either through a software or hardware switch.