I was a big fan of multi-image (multi-projector slide shows). The technology to create and display these shows has become obsolete. I'm working to preserve old multi-image shows by writing software to convert them to modern media. I've started by (mostly) reverse-engineering the Mate-trac control signal.
I've purchased an old 286 PC with an AVL Genesis card. AVL—Audio-Visual Laboratories—was another major producer of slide show controllers. Using this old PC, I plan to reverse-engineer AVL's Procall protocol as I've done for Mate-trac.