cross-posted from: https://wolfballs.com/post/8432
In essence, the Digi-Comp I contained three mechanical flip-flops, providing 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 was 'clocked' by moving a lever back and forth. Different configurations of these cylinders caused 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 could 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.[1]
https://infogalactic.com/info/Digi-Comp_I
https://www.instructables.com/Digi-Comp-I-Redux/
Original Manual [PDF]: https://content.instructables.com/ORIG/F0M/LE8X/K1UYXD8T/F0MLE8XK1UYXD8T.pdf
3D printable version, another example: https://www.thingiverse.com/thing:1477209