Bret, A really simple DAC can be made with a just a bunch of resistors, of two values (look up "R-2R" DAC). Crude, but simple :-) Neil -- Neil Johnson :: Computer Laboratory :: University of Cambridge :: http://www.njohnson.co.uk http://www.cl.cam.ac.uk/~nej22 ---- IEE Cambridge Branch: http://www.iee-cambridge.org.uk ----