Thanks for that. This is actually a really big help. I had the pinout but needed the behaviour because the 0120 does something but I couldn't determine if it was the correct thing under certain conditions.
Do you have any information on the characteristics available? Even a truth table or something? I'm trying to fault find on a 5200CD with some weird issues stopping it from powering on and I've got no reference for a 0120 to work out if it's behaving normally. Depending on results, any idea when...
I don't know what to say. I have a lot of old equipment from before it was "retro". I keep it running, or get it working, or sometimes modify it because it's so easy now to add things that would have prohibitive.
So... yeah.