Found in a Popular Electronics from the 90s, this circuit can be used as an electrifier. T1 can be an old TV fly back transformer or an ignition coil.
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...