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 General Electric circuit was published in 1970. The LED is infrared and the voltage according...
This circuit was found in the October 1989 issue of Radio Electronics magazine. It drives an...
The transistor can be a modern equivalent and the transformer is the type of output found on an...