With this circuit from the September 1989 issue of Radio Electronics magazine, it is possible to receive VLF band signals on a common radio, just like the signals emitted by the previous receiver.
This old slide projector control circuit was found in an 80s Hands On. The circuit uses modern...
In the figure we have a circuit that uses unusual components, being indicated for low frequency...
The sensor of this circuit found in Popular Electronics can be formed by a piece of fabric between two...