This circuit is based on a regulator component that consists of a transistor and zener in the same package. The circuit can be designed with the equivalent discrete configuration. The current is 200mA.
The critical components of this 1978 circuit are transformers, which, hopefully, can be obtained from...
Found in a manual of integrated circuits from the 90s, this circuit makes use of that time...
This tuning-free circuit was found in an old operating amplifier manual. The setting can serve as...