This relay triggered by voice or by another sound was found in an Elektor from the 90's. The circuit uses a 12 V sensitive relay and has no sensitivity control.
This circuit was found in an old Linear Technology documentation. The working principle can be...
Scratch is the scratching noise that occurs on old, scratched discs and the rumble is the...
This 6-transistor receiver was manufactured in Japan in the 60s. The circuit is superheterodyne and has a 6V...