This circuit has a 100 dB dynamic We found it in a Popular Electronics from the 90s. Equivalent operational can be used.
We found this crystal AM radio using a germanium diode in a Japanese magazine in 1967. The circuit...
This circuit triggers a photographic flash when the microphone picks up a sound. The SCR can be...
This circuit decodes a 1800 Hz tone used in communications. The circuit is from an American...