In the figure we have the configuration of a voltage regulator with 3 transistors. The components depend on the desired voltage and current as well as on the characteristics of the transistors.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
This power source with silicon diodes at a time when valves were still used was found in Radio...