This circuit compensates for the brightness of an LED as a function of temperature. We found it in an Electronic Design from the 80s. The components admit equivalents.
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...