Disrupting the System

The basic idea of a stun gun is to disrupt this communication
system. Stun guns generate a high-voltage, low-amperage
electrical charge. In simple terms, this means that the
charge has a lot of pressure behind it, but not that much
intensity. When you press the stun gun against an attacker
and hold the trigger, the charge passes into the attacker's
body. Since it has a fairly high voltage, the charge will
pass through heavy clothing and skin. But at around 3
milliamps, the charge is not intense enough to damage the
attacker's body unless it is applied for extended periods of
time.

It does dump a lot of confusing information into the
attacker's nervous system, however. This causes a couple of
things to happen:

* The charge combines with the electrical signals from
the attacker's brain. This is like running an outside current
into a phone line: The original signal is mixed in with
random noise, making it very difficult to decipher any
messages. When these lines of communication go down, the
attacker has a very hard time telling his muscles to move,
and he may become confused and unbalanced. He is partially
paralyzed, temporarily.

* The current may be generated with a pulse frequency
that mimics the body's own electrical signals. In this case,
the current will tell the attacker's muscles to do a great
deal of work in a short amount of time. But the signal
doesn't direct the work toward any particular movement. The
work doesn't do anything but deplete the attacker's energy
reserves, leaving him too weak to move (ideally).

At its most basic, this is all there is to incapacitating
a person with a stun gun -- you apply electricity to
a person's muscles and nerves. And since there are muscles
and nerves all over the body, it doesn't particularly matter
where you hit an attacker.

Standard Stun Gun
Conventional stun guns have a fairly simple design. They are
about the size of a flashlight, and they work on ordinary
9-volt batteries.

The batteries supply electricity to a circuit consisting of
various electrical components. The circuitry includes
multiple transformers, components that boost the voltage in
the circuit, typically to between 20,000 and 150,000 volts,
and reduce the amperage. It also includes a oscillator,
a component that fluctuates current to produce a specific
pulse pattern of electricity. This current charges
a capacitor. The capacitor builds up a charge, and releases
it to the electrodes, the "business end" of the circuit.

The electrodes are simply two plates of conducting metal
positioned in the circuit with a gap between them. Since the
electrodes are positioned along the circuit, they have a high
voltage difference between them. If you fill this gap with
a conductor (say, the attacker's body), the electrical pulses
will try to move from one electrode the other, dumping
electricity into the attacker's nervous system.

More Electrodes

These days, most stun-gun models have two pairs of electrodes:
an inner pair and an outer pair. The outer pair, the charge
electrodes, are spaced a good distance apart, so current will
only flow if you insert an outside conductor. If the current
can't flow across these electrodes, it flows to the inner
pair, the test electrodes. These electrodes are close enough
that the electric current can leap between them. The moving
current ionizes the air particles in the gap, producing
a visible spark and crackling noise. This display is mainly
intended as a deterrent: An attacker sees and hears the
electricity and knows you're armed. Some stun guns rely on
the element of surprise, rather than warning. These models
are disguised as umbrellas, flashlights or other everyday
objects so you can catch an attacker off guard.

These sorts of stun guns are popular with ordinary citizens
because they are small, easy-to-use, and legal in most areas.
Police and military forces, on the other hand, typically use
more complex stun-gun designs, with larger ranges.