William Donzelli wrote: A double-header hamfest weekend yielded a couple of vintage digital logic trainer items. The first is one of those little wood boxes DEC Logic labs, but who cares about that. The more interesting thing is a book for the CDC logic trainer. From the pictures and writeups in the manual, this box has no logic of its own, but is made to accept a small number (20) of logic cards from a 1604. It mentions that it can be lightly modified to take 3000 series cards as well. Can Billy or Chuck add any comments? I have never seen or even heard of this box before. -- Will --------------------------------- The logic trainer was developed by Control Data Institute. They also did a workbook with a series of simple experiments. It was a part of their program to take high school graduates to computer technicians in 12 months. Lots of government funding for the 12 month program, so the classes were usually full. I believe there a couple of list members who took that class. The 1604 and 3000 cards both use +/- 20 volts, though on different pins. 1604 has power on pins 13,14 15; 3000 has power on pins 6, 7 and 8. So the mod was moving power pins. The signal levels could be mixed without level converters, though you stressed the 3000 inputs doing it. I only know of piece of equipment that actually mixed the logic families on the same chassis: The Digigraphics system. The power wires are always solid red, blue with black for ground. I may still have some of the documentation for it, but very uncertain. It's been a few years. However, Al has posted some of the CDI training manuals used with it. One is at CDC/modules/60238500_3000pcbs_Dec68.pdf. Billy