Credits to mmcgaha, who posted this in the thread about the school that can't turn off their lighting: <a href="https://news.ycombinator.com/item?id=34452424" rel="nofollow">https://news.ycombinator.com/item?id=34452424</a><p>I did some digging on how the Amiga <i>actually</i> controls the HVAC systems, because at first I assumed it was through GPIO, maybe the parallel port or a dedicated I/O expansion card. However, it seems like it's talking directly to an HVAC control box by made by Johnson Controls (<a href="https://en.wikipedia.org/wiki/Johnson_Controls" rel="nofollow">https://en.wikipedia.org/wiki/Johnson_Controls</a>) which communicates over radio and that seems to be the cause of the recurring radio interference always reported in articles about this school.<p>It seems like a pretty good separation of concerns. The Amiga could probably be trivially replaced by a more modern computer if someone actually wanted to. Same goes for the radio box, which is probably the even more pressing concern. At the cost of running data lines to the boiler rooms or even switching to a modern digital remote control system, you could keep most of the system as is without swapping out hardware extensively.