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.
Found in Motorola documentation from the 90s, this circuit makes use of a triac from that time. The...
This transistorized signal injector was one of the first that we found using the well-known...
This 200-mW amplifier uses one of the first commercial power transistors. The circuit is from a...