This audio-driven relay was published in the July 1977 issue of Radio Electronics magazine. The circuit uses CMOS components, and the relay must be a sensitive type.
This circuit, which appears at other points on this site, can be designed with both 4011 and 4001...
We found this circuit in an American documentation from the 90s. The circuit applies to vehicles...
Found in Motorola documentation from 1967, this circuit shows how it is possible to obtain a...