This circuit indicates when the voltage of a 12 V battery is low. With changes, for example, the zener, the circuit can be used to monitor other voltages.
November 2016 - The On Semiconductor Reference Development Kit and WDK1.0GEVK Reference Kit can...
This circuit was obtained in a 90s documentation. However, it can be developed with modern...
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...