This circuit for incandescent lamps was found in the January 1980 Radio Elecronics magazine. The sensitivity can be controlled by a potentiometer and the microphone used is of the dynamic type.
This circuit was found in a 1970s General Electric documentation. Transistors are uncommon today....
This circuit, from a component manual, also applies to other components in the same family. The...
The sensor of this circuit is a common transistor and the trigger point is set on the trimpot or...