This circuit activates a horn from an audio signal. This can be used for remote control via audio signals. The circuit is from a Radio Electronics from October 1965.
This circuit was found in an American 1980s documentation. The integrated circuit used is uncommon...
We found this circuit in a Radio Electronics magazine from June 1992. The circuit has a power...
This simple audio and RF signal tracker was found in a Japanese publication in 1967. The...