This article is about the "DIGI-COMP I" device ... a mechanical calculating toy from 1963.
DIGI-COMP was designed for manual operation. For better visibility, an Arduino-based motor mechanism is added here.
On first look DIGI-COMP appears to be quite outdated and limited, even for retro-enthusiasts.
But all these levers, sliders and rods implement a finite-state-machine with flip-flops and a combinatorical AND/OR logic matrix, so it is quite timeless and is a great model to teach logic design.
In this article series you find videos showing DIGI-COMPs operation, the manuals, links to other pages, operation details, theory of logic functions in normal form, similarity to modern FPGAs and a discussion about Turing completeness.