A follow-up to my accident. I had a 6 year old Visual 1 version controller on a shelf in the warehouse. I didn't think it would work anymore, but I replaced it with that broken VIsual 3 version. The surprise was when everything went back to normal and all the lighting and other things controlled by the IHC were working in the house. A couple of minor changes still need to be made to work by programming the IHC. As long as I can just get the computers hooked up to it on the serial bus. As I recall, it used to be a pain to get it to play with a Windows machine.
I'll send that broken controller to be examined, if there's a component that could be replaced to fix it.
Because of this problem, I'm thinking of starting a project to replace the electrical controls in my house away from the IHC system. I have already briefly researched various options, and so far switching to Shelly components seems to be a cheap and quick solution. Is there anyone here on the forum who has swapped the central bus components for Shelly products? For the more expensive ones like KNX I don't want to go with what I learned from this IHC saga. My house also has a well working HomeAssistant installation, so connecting new components to it using e.g. Shelly is completely painless.