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 tests quartz crystals of frequencies between 100 kHz and 10 MHz. The circuit is from...
We found this circuit at a January 1991 Modern Electronics. The magazine no longer exists, but the...
The ZN416E integrated circuit is uncommon today. It consists of a complete radio, like the one...