This protective circuit for power lines was found in a Radio Electronics from November 1957. The transistor used can be any general-purpose transistor such as the CK722.
The circuit shown is suggested by Texas Instruments and uses the TL489 as a base, thus providing 5 levels...
This source was found in old documentation, based on a regulating integrated circuit popular at...
This circuit was found in a 1980s American documentation. The circuit is based on integrated CMOS 4001...