This circuit can be built using a small audio transformer. It also has a capacitor that will continue oscillations after the button is released for at least half a second each time. The 1mF cap is on the low tension side of the transformer. It could be a 16 volt electrolytic.
Alternatively, if you have a iron core toroid available or one that comes from a dead computer power supply, you can wind the transformer yourself. The size or thickness of the wire windings is not important. Just the number of turns. The Internet is full of sites that explain how to wind toroidal transformers.
This circuit could be built into a plastic enclosure a little bigger than a PP3 9 volt battery. It will require a safety switch and two prongs capable of puncturing clothes. It won't kill anyone but it certainly is capable of being a deterrent to abusive or violent action.
Note: in no way do I advocate the use of this type of circuit. This circuit is provided for educational purposes only.
