I
n one of the true ironies of the computing world, a PC’s biggest enemy is the very
thing it must have to operate: the electricity it gets from the public power system. The
public power system is an imperfect river of electricity that has periods of high, low,
and no voltage. The high voltages, referred to as over-voltage or spikes and surges, can
fry the PC’s power supply and eventually the motherboard and all attached to it. Low
voltage periods, also called under-voltage and brownouts, can also inflict damage on the
powersupplyandtheothercomponentsofthePC.Asuddenlossofpower,a.k.a.ablack-
out, loses data and valuable processing time. In addition, a spike in the voltage typically
follows a blackout that can fry the fragile components inside the PC.
The two types of damage that can be done to a PC by its electrical supply and electro-
static discharge (ESD) are catastrophic and degradation. Catastrophic damage is when a
component or device is destroyed all at once in a single event, such as a direct lightning
strike on a building burning out all of the electrical devices plugged into its AC mains.
Degradation is when a device is damaged over a period of time, a little at a time, and
eventually, usually much later, begins to fail or have intermittent problems. While a cata-
strophic failure is very serious, most damage to a PC and its components and peripherals
is degradation, the result of hundreds and thousands of small electrical events that have
slowly degraded the ability of a device to perform. People tend to focus on the cata-
strophic events, but you should protect your system against degradation.Power Line Problems
A PC’s power supply is quite a heroic device when you consider all that it must contend
with day in and day out. One thing that can be said for the public electrical supply sys-
tem is that it is not consistent. Not all of the inconsistency is the electrical company’s
fault. Many different situations, many beyond the electric company’s control, can cause
the electricity received at your home or office to fluctuate u por down. The fluctuations
ontheelectricalsupplylinearewhatcausethePC(anditspowersupply)themosttrouble.
Six general types of electrical events occur on an electrical power line and reach
your PC: line noise, power surges, power spikes, power sags, brownouts, and black-
outs. Each of these has its own varying level of impact on the PC power supply, but the
PC can be protected from each successfully. It’s mostly a matter of how much you want
to spend to protect your system.Line Noise
Every electrical circuit has a certain amount of electrical line noise, which is electromag-
netic interference (EMI) caused by many sources, both from nature and electrical equip-
ment. Most EMI comes from electrical equipment, such as a motor, welder, fluorescent
lighting, and radio transmitters. An electrical supply line that is shared with noisy electri-
cal equipment very often carries the electrical noise of the equipment over the circuit to
other devices connected to the circuit. An example is what happens to your AM radio or(^600) PC Hardware: A Beginner’s Guide