The sensor used in this circuit is uncommon today, however equivalent types can be tried. The comparator also supports modern equivalents. The circuit is from 80's documentation.
In the figure we show our first circuit that consists of a simple touch switch capable of driving a...
This circuit was found in an 80's Electronic Engineering. The power supply must be symmetrical. The...
This metal detector was found in a French magazine Radio Plans from 1977. The phone can be a...