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 antenna for the frequencies 146 or 440 MHz was found in a magazine 73 for Amateur Radio of...
This circuit produces 1 kHz square signals using the CMOS IC 4070. The frequency is given by the...
Found in a 90s PE Hobbyst Handbook, this circuit mimics the sound of a space gun. The components...