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.
Found in the 1969 neon lamp documentation, using neon lamps this circuit provides 18 V regulated...
This circuit was found in a Popular Electronics from the 90s. The circuit uses a general purpose...
This circuit was found in an ancient American documentation. The transformer is the type used in...