Continuing the discussion from Technician keeps computer made in 1959 still humming along:
Here’s the modern homebuilt Zusie machine (more in this playlist):
A modern build of a floating point square root calculator
This is a machine I built to calculate square roots. It uses only electromechanical relays like the early computers of the 1930s. There are 480 of them, each with a light that you can watch on the front panel. No micro controllers in sight!
See also Simon Winder’s site: