A plug-in surge protector is on the order of tens of times
more money per protected appliance. Furthermore it does not
even claim to protect from the typically destructive
transient. Protectors do not stop, block, filter, or absorb
destructive transients. Ineffective protector manufacturers
get one to wish that is how they work. In reality, the
protector is not protection. Protector and protection are two
separate components of a surge protection system. Effective
systems must include the protection. And the connection to
protection is either a hardwire (less than 3 meters) or a
protector (also part of a less than 3 meter connection).

In short, the protection is called single point earth
ground. Destructive surges may enter the building seeking
earth ground. If not earthed (either by hardwire connection
or by surge protector), then the destructive surge may find a
path to earth ground via computer. One classic example is due
to a direct strike to lines highest on utility poles - AC
electric. Incoming on AC electric, through computer and its
modem, then outgoing to earth ground via phone line. Many
then *assume* the surge entered on phone line, damaged modem,
then stopped - a violation of even primary school science.

Effective protection means all incoming utilities are
earthed before entering the building. All must be earthed to
the same single point earth ground. That means even the CATV
wire drops down to earth ground, connects ground block 'less
than 3 meters' to that earth ground, and only then rises back
up to enter building. Again, no surge protector required
because earthing is accomplished by a direct and short
hardwire connection.

These concepts are explained further including some examples
of 'whole house' protectors for AC mains at:
"RJ-11 line protection?" on 30 Dec 2003 through 12 Jan 2004 in
pdx.computing at
http://tinyurl.com/2hl53 and
"strange problem after power surge/thunderstorm" in
comp.dcom.modems on 31 Mar 2003 at
http://tinyurl.com/2gumt .

Additional information on how surge protectors work, how
they are rated, installed, etc was posted in:
"Opinions on Surge Protectors?" on 7 Jul 2003 in the
newsgroup alt.certification.a-plus at
http://tinyurl.com/l3m9 and
"Power Surge" on 29 Sept 2003 in the newsgroup
alt.comp.hardware at
http://tinyurl.com/p1rk

One industry professional demonstrates how two structures
are protected. Notice every wire entering each structure
(building and tower) must first connect to single point
ground. Even the buried phone wire carries a potentially
destructive transient which is why even buried wires must
enter building at the service entrance with the 'less than 3
meter' connection to earth ground:

http://www.erico.com/public/library/...es/tncr002.pdf

How do we identify ineffective protectors? 1) No dedicated
connection to earth ground AND 2) manufacturer avoids all
discussion about earthing. A surge protector is only as
effective as its earth ground - the protection.

Those ineffective protector manufacturers fear you might
learn about the essential earth ground AND discover that
plug-in protectors cost tens of times more money per protected
appliance.

Pyriform wrote:
I have a surge protector which includes protection for the
phone line, so that's where the ADSL modem gets plugged.
Whether it would actually work or not is another matter of
course. My complacency lies in not bothering to research the
matter thoroughly, on the grounds that if I was buying snake
oil, it was at least *cheap* snake oil...

For the mains, online UPS is the proper solution, but I
can't say I'm unduly concerned about not having one. Power
provision in the UK is fairly reliable at the moment,
although political and business imperatives will probably
conspire to make it worse in the future.