Video from the RICM page:
There’s a bit of a history here, and you can buy a modern remake too:
Minds-On Toys - Kits
No one today would claim so reverently, as ESR did in 1963, that Digi-Comp is the “mechanical equivalent of an electronic digital computer” (probably quite a stretch, even back then). And is it still true, or was it ever, that “everything you learn on Digi-Comp can be used on large electronic digital computers”?
Digi-Comp is an ingenious, transparent Logical Gizmo that can teach anyone about binary numbers and Boolean algebra, still fundamental concepts in digital circuitry.
Digi-Comp’s unique combination of mechanics and logic forges a unique kind of connection between hand and mind. Like many great educational toys, it challenges you to think. But like almost no other toy we know, it also literally puts you in touch with a way of thinking.
There’s an archive here of the posts, images, and files from the soon-to-be-killed-off Yahoo! Group:
And here’s an Instructable for building your own: