Cassidy James 
Ever wonder how radio buttons—you know, the IRL thing that gave the form buttons their name—work? I had never really thought about it, but I loved discovering it with this video.
Elias Mårtenson@cassidy That explains why some devices used to be able to hold more than one button down if you pressed them at the same time. This is what is being described here.
I'm still curious how the more fancy devices worked that prevented more than one button being pressed at the same time. I suspect that was a separate mechanism (I can envision a few different ways of achieving this)