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 small blocking oscillator for approximately 1000 Hz was found in an American documentation from the...
An audio signal is applied to the input of this circuit. Depending on the position of the selector...
Using only one LM107 operational amplifier, National Semiconductor suggests the circuit in the...