This stun gun is powered by a 9V battery. The transformer steps up the voltage to about 1800V (but with very low current). A 555 timer IC is used to generate a high-frequency output. A 1 MEG variable resistor can also be used at the output to drop the voltage, but this is optional. If you build this circuit, be careful, as it outputs a high voltage. Touching the output leads will induce a painful shock.