This circuit allows the activation of a remote telephone bell made with a common piezoelectric capsule. The circuit does not need power, as it is powered by the line call signal itself.
This circuit was originally intended for reading movie soundtracks. The circuit is from 1967 and...
This circuit was obtained in an old magazine from the 1970s. The circuit can still be assembled with...
This circuit recognizes a tone determined by the tuned input circuit (R3 / R4 / C2). The circuit...