This circuit was found in a 1974 publication. It consists of a voltmeter for high voltages, up to more than 100 V, using a neon lamp.
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...