This circuit switches power loads with audio signals. The circuit is from a Popular Electronics from the 90s. The components can be changed depending on the signal used.
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...