This variable frequency circuit was found in a Popular Electronics from the 90s. The circuit outputs to a small speaker and can be powered by voltages as low as 3 V.
Found in old English documentation this circuit can be made with a BF245 or equivalent. Coils are...
This circuit is indicated for the generation of signals in the 40 meters range. The circuit was...
Carbon microphones are no longer used in most projects. However, finding one in the scrap metal, it...