Surges, spikes, zaps, grounding and your electronics

	Theoretically, the power coming into your house is a perfect AC
	sine wave.  It is usually quite close.  But occasionally, it
	won't be.  Lightning strikes and other events will affect the
	power.  These usually fall into two general categories: very
	high voltage spikes (often into 1000s of volts, but usually
	only a few microseconds in length) or surges (longer duration,
	but usually much lower voltage).

	Most of your electrical equipment, motors, transformer-operated
	electronics, lights, etc., won't even notice these one-shot
	events.  However, certain types of solid-state electronics,
	particularly computers with switching power supplies and MOS
	semiconductors, can be damaged by these occurances.  For
	example, a spike can "punch a hole" through an insulating layer
	in a MOS device (such as that several hundred dollar 386 CPU),
	thereby destroying it.

	The traditional approach to protecting your electronics is to
	use "surge suppressors" or "line filters".  These are usually
	devices that you plug in between the outlet and your
	electronics.

	Roughly speaking, surge suppressors work by detecting
	overvoltages, and shorting them out.  Think of them as voltage
	limiters.  Line filters usually use frequency-dependent
	circuits (inductors, capacitors etc.) to "tune out" undesirable
	spikes - preventing them from reaching your electronics.

	So, you should consider using suppressors or filters on your
	sensitive equipment.

	These devices come in a very wide price range.  From a couple
	of dollars to several hundred.  We believe that you can protect
	your equipment from the vast majority of power problems by
	selecting devices in the $20-50 range.

	A word about grounding: most suppressors and EFI filters
	require real grounds.  Any that don't are next to useless.

	For example, most surge suppressors use MOVs (metal oxide
	varistors) to "clamp" overvoltages.  Yes, you can have a
	suppressor that only has a MOV between neutral and hot to
	combat differential-mode voltage excursions, but that isn't
	enough.  You need common-mode protection too.  Good suppressors
	should have 3 MOVs, one between each pair of wires.  Which
	means you should have a good solid ground.  Eg: a solidly
	connected 14ga wire back to the panel.  Not rusty BX armour or
	galvanized pipe with condensation turning the copper connection
	green.

	Without a ground, a surge or spike is free to "lift" your
	entire electronics system well away from ground.  Which is
	ideal for blowing out interface electronics for printer ports
	etc.

	Secondly, static electricity is one of the major enemies of
	electronics.  Having good frame grounds is one way of
	protecting against static zaps.

	If you're in the situation of wanting to install computer
	equipment on two wire groundless circuits take note:

	Adding a GFCI outlet to the circuit makes the circuit safe for
	you.  But it doesn't make it safe for your equipment - you need
	a ground to make surge suppressors or line filters effective.