This circuit is intended for detecting 3 levels power grid voltage, and it can be adapted to operate with the most diverse voltages. The circuit uses neon indicator lamps.
This circuit was found in an old American publication. The integrated circuit used is no longer easy...
Using a transconductance operational amplifier, this circuit was found in July 1983 Radio...
This battery-powered emergency light circuit was published in an April 1962 Radio Electronics...