I was in my mid 20's when I was sent by my company to give a short training course to a civilian group that worked for the US Army Signal Corps at Fort Gordon.

I was in my mid 20's when I was sent by my company to give a short training course to a civilian group that worked for the US Army Signal Corps at Fort Gordon. These guys built simulators of the big field radios that the signalmen carried around and everything was done with relay logic. This was the mid 90's and it blew my mind: I'd heard of relay logic in some EE course or the other, but I'd never actually seen it in operation. It's one thing to understand what's theoretically possible; quite another to actually see combinatorial and timing logic executed by loudly clacking relays. But it worked! They used relay logic because it's what they knew: some of them had backgrounds in industrial control. The small company I worked for sold single board computers and the group leader knew that there had to be a better, more modern method of building their simulators, so they asked to have someone sent down to educate them. That someone was me. I probably did a piss-poor job of it (no experience or aptitude for training at the time) but I hope it at least set them on the right path.