Avi sez, "The Digi-Comp 1 toy kit was a cool hands-on way to learn the basics of computing. The Digi-Comp 1 emulator is an interim substitute for those who can't get their hands on one."
In essence the Digi-Comp I contains three mechanical flip-flops and provides an ability to connect them together in a programmable way using thin vertical wires that are either pushed, or blocked from moving, by a number of cylindrical pegs. The whole arrangement is 'clocked' by moving a lever back and forth. Different configurations of these cylinders cause the Digi-Comp to compute different boolean logic operations. With a three binary digit (3-bit) readout of the state of the flip-flops, it can be programmed to demonstrate binary logic, to perform various operations such as addition and subtraction and to play some simple logic games such as Nim.
See also the magnificent CARDIAC, the cardboard teaching computer produced by Bell Labs.
D I G I - C O M P 1 (Thanks, Avi!)