[TrackerFF]

Back when I studied EE, one of our class projects (industrial automation) involved working with companies out in the industry. We found a local heating companies that provided district heating, and they had this ancient PLC running some pretty central parts of the operation. By ancient, I mean early 70s or so. But the thing had just been running for forever, doing its thing.

No documentation, of course, so a metric ton of black-box testing to find out what did what.

In the end we managed to design a pretty nice interface/HMI, and a API so that it could be monitored online.