two units. Both units have DB-25 D-type connectors. Does anyone have a wiring diagram of this cable. Hi I think I have it someplace. There are about 3 or 4 lines that need to be twisted pairs with a ground lead. The original used a bundle of twisted pairs that had black leads for the one twisted lead. I many cases, the black leads carried data signals and not ground. The cable manufacture only checked that the cable had continuity and not that the right pairs were twisted. When I worked at Intel, I made a checker that would display the number of incorrect twisted pairs by doing a transformer coupling of the wires. It may take me a while to look for the programmer cable drawings. Hopefully, Joe or Dave can find one quicker. Dwight