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 Italian magazine (1988), but can be mounted with ease even with the...
In the figure we have a simple shield of 1 transistor. The supply voltage depends on the relay. The...
The operational 714 (not the 741) is an old Raytheon type that is no longer common today. The...