A taser is a non-lethal weapon used by many police forces around the world. Much like a stun gun (to which the name taser is sometimes erroneously applied) a taser incapacitates its victims by appliction of an electrical current, however it supercedes this ancestor by its ability to affect a target at range. Perhaps the best demonstration of a Taser is in the early Jackass episode in which Johnny Knoxville has various self defense weapons tested out on him.
Structure and function
A taser is typically the size of a handgun, although not all tasers are in this shape. The batteries are typically stored in the handle, or rear of the taser. These are used to charge capacitors, which allow an electric shock in the region of 50000V to be administered, but at only a 2-3 mA current. These are connected not only to a set of prongs, as in a normal stun gun, but to two probes, which are attached to insulated wires of up to 20 foot length. Civilian tasers are typically limited to a 15 foot range.
The first time the trigger is pulled, a compressed gas (usually CO2) cannister is broken, and the pressure generated fires the probes out of the front of the weapon. Since the probes are barbed they will stick to clothing or skin. While the trigger is held down the capacitors are charged and discharged in a rapid cycle, shocking the victim, even through fairly thick clothing.
Even if the probes miss, the taser can still be used as a normal stun gun simply by pulling the trigger and pressing the prongs against the target.
I suggest you check out http://electronics.howstuffworks.com/stun-gun3.htm for a rather good diagram to supplement my textual description.
The powerful electric shocks administered by the taser override the body's usual neurochemical nerve impulses, causing uncontrolable muscle spasm, which cause intense pain, and drop the target very quickly.
Recovery time is dependent on the duration of shock administered. Brief shocks may allow near instantaneous recovery, but those of an extended duration will cause systemwide shock, and neutralize the target for several minutes.
Advantages and disadvantages of the Taser
There are many factors that make tasers useful for both law enforcement and self defense use. The most important of these is the non-lethal nature of the weapon, which enables it to be employed in a much wider range of situations than a gun. Tasers are also heart pacemaker safe.
Other non-lethal weapons share this characteristic, but tasers are more effective. Not only can a target be struck at range, minimising danger to the user, but almost any point of the body is a suitable target, unlike pepper sprays which must be targeted at the face.
In America, tasers are not classified as firearms, and may therefore be carried and bought without a licence, but several States have stricter rulings. In most other countries, such as the UK ownership is restricted to the police.
Unfortunately the taser is not a perfect weapon. The first drawback is that range is limited by the length of the wires that are required to carry the electrical current. The range should however be more than sufficient to deal with agressors armed only with melee weapons.
The other major issue is the one shot nature of the taser. While a taser can be reloaded by repacking the wires and probes, and replacing the gas cannister this is not a quick operation, and cannot really be done in the field. The backup stun gun feature on most tasers is provided to somewhat compensate for this problem. To ensure a hit many tasers are equipped with laser sights, which indicate the point of impact on the target.
To be updated soon, once I'm no longer on a web proxy that bans anything remotely related to weaponry.