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.
The relay of this circuit closes when the position set in P2 is reached by the sensor...
In this circuit the output voltage is given by xx. The L series circuits are for a maximum current of...
This circuit consists of an electrostatic sensor that can check if a cable is energized by simply...