This sonic key or vox was found in old English documentation. The operational admits equivalent as well as the transistors. The microphone is crystal.
In this circuit the LED lights up when the voltage drops below the value set in the trimpot. The...
This circuit was obtained from a Linear Technology manual from the 90's. The integrated circuits are...
Found in a 1995 documentation, this circuit is an alternative output to the previous circuits. The MOSFETs...