This is an amazing unit, kind of like a hand held TENS. Electricity is jumped between the two metal prongs (the unit is not a stun gun, there is no spark or crackle when activated). The prongs are pressed against someone and the sensation is felt. It operates in two modes, either pulse or continuous. For the price we cannot recommend the cobra stinger enough. Powered by two AA batteries (not included), this is a self contained unit. It does not accept cables or allow for use of attachments, such as our Huse Estim insertable electrodes. However it is a whole lot of fun in a small easy to use and inexpensive device.