CARDIAC: Bell Labs's old cardboard computer

Make Magazine's Arwen O'Reilly recently wrote asking if I could provide a brief reminisce about a kit that I'd especially loved as a kid. I wrote her this:

In between getting a Selectric in 1976 and a TTY in 1977, we had a brief period in my household where my dad was transitioning from being a programmer to going to teacher's college. He brought home a "cardboard computer" that you assembled by punching out parts, inserting tabs into slots. It assembled to something about three-card-thicknesses deep and about 10" by 6". It had little tokens that represented bits, and a table of operations. You could write a program to calculate, say, 2 + 2, then move the tokens around from one part of the computer to another, simulating the shunting of bits through logic-gates, until you got the total. I was completely enchanted with this thing -- I spent days and days making it add up very small numbers, fascinated by this look into the universe of a Von Neumann machine. Years later I saw Tron and was unimpressed -- sure they had speeder-bikes, but they weren't a patch on my cardboard tokens. I wish I could remember what that thing was called!

Based on my sketchy description, Arwen managed to turn up the long-lost cardboard computer: it was a Bell Labs CARDIAC: A Cardboard Illustrative Guide to Computers. There's a lot of CARDIAC fans out there, and there may even be a vendor still selling original, left-over CARDIACs!

CARDIAC Photos Link, Answers About CARDIAC

(Thanks, Arwen!)