This simple circuit makes use of neon lamps to indicate the voltage of a power grid. The lamps are common neon and the circuit indicates whether the voltage is 110 V or 220 V.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...