HOW ARE THEY USED?

A taser delivers up to 50,000 volts. This does really sound like a lot of electricity, but it's a misleading way of expressing the power a Taser uses.

The electrical weapon, according to TASER International, overrides the brain’s control of the body by speaking the same ‘language’ as nerves. 

Tasers are designed to weaken a person through up to five centimetres of clothing. Taser International says the electrical pulse is delivered at a high voltage because the electric current has to pass through clothing and air — neither of which is a good conductor of electricity — to make a complete circuit with the target

Taser International also says that while its device can deliver up to 50,000 volts in an open air arc only, it does not deliver that much voltage to a person's body. The company says its Taser X26 delivers an average of 1,200 volts.

Source: 

http://scienceline.org/2007/08/ask-sergo-tasers/