This sonic relay or vox was found in a Popular Electronics from the 90's. The power MOSFET can be of any type determining the controlled load.
This circuit with integrated TTL 7400 has a good teaching purpose, drawing one of two LEDs. The...
Found in American documentation from the 70s, this circuit uses components of the time, uncommon...
This circuit makes use of a diac to stop the activation of a sensitive reed relay 1 mA. The trip...