I absolutely adore this series of videos! Analog/mechanical computing is a fascinating field that is often ignored.
Also the pedagogical style of these videos is fantastic, simple, to the point, with no unnecessary distractions. It's hard to find this level of quality in the current 'click and subscribe' universe!
Another archaic technology is magnetic amplifiers. These were more used in Germany (in the Kriegsmarine and also in the V-2), but got some more play in the US immediately after the war, before being largely supplanted by transistors.
The idea here was to use magnetic saturation to modulate the behavior of a transformer, allowing a small control current to modulate larger AC currents.
Also the pedagogical style of these videos is fantastic, simple, to the point, with no unnecessary distractions. It's hard to find this level of quality in the current 'click and subscribe' universe!
Happy to see this pop on HN :)