This circuit is from a 1968s Motorola documentation. The load can range from 10 to 100ohm and the transistor supports a modern equivalent such as 2N2222 or BD135.
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...