This circuit was found in the March 1995 issue of Electronics Now magazine. The circuit requires a symmetrical power supply, and the FET is a common general-purpose type.
Carbon microphones are no longer used in most projects. However, finding one in the scrap metal, it...
This circuit produces a strong tone of audio or ultrasound, depending on the values of components C1 and...
This alarm from an old 1978 publication uses PNP transistors and driver and output transformers that are...