This circuit is from American documentation from 1970. It can be designed with a BC558 and for the operational, we can use equivalents. The FET can be the BF245.
Found in a Popular Electronics from the 90s, this circuit checks the presence of voltage on a...
Found in Popular Electronics from the 90s, this signal tracer or tracer can be used with the inner...
The circuit shown in the figure is indicated for alternative sources of energy, such as those...