Glowing mercury thyratrons: inside a 1940s Teletype switching power supply | Hacker News

Nice. Thyatrons were about the only component available for high-power control in the tube era. Today we have MOSFETs which approach ideal power switches, but it took a long time to get there.
As someone pointed out, that’s a switching voltage regulator, not a switching power supply. The transformers there are all upstream of the switching.