This circuit, which appears in other versions on this website, was obtained in old documentation. The load of each PUT depends on its characteristics. The circuit is low frequency.
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...