John, The Logi-Tran 4 was the follow on to the Logi-Tran 2. I used both to teach EE370 in 1979 or 1980. As you've no doubt learned by now, it's basically a "50 in 1"-ish logic trainer with spring connectors, switches (inputs), lights (outputs), and of course, the logic ckts themselves. It was a great trainer for our digital lab (I was the TA). I remember making a 4 bit calculator with one of my more talented students by hooking up a Logi-Tran 2 and a Logi-Tran 4 (we used lots of gates) side by side. If you've let it sit because of the lack of a manual, just start setting up the ckt emulation of a logical statement (I seem to remember that the Logi-Tran used NORs and NANDs). There was some limit on the output drive of each gate, but my memory doesn't have all the details. Hope you have had fun. Let me know if you get bored with it and want to get rid of it. Later... Kevin Dowd