This circuit with 1% regulation aims at replacing mercury cells. We found it in a 1967 documentation. Transistors can be replaced with modern equivalents.
This circuit simulates an inductor. Or operational amplifier of old type, but a configuration is...
This circuit for the logic control of the 555 in a power supply was found in the October 1989...
This traditional configuration from a 1980 publication shows how a reed relay is used to control a 240...