First you are assuming electricity works like a wave
crashing on the beach. Does the transient enter on phone
line, destroy phone, then stop? Of course not. A transient
first flows equally through everything in a path from the
cloud to ground. Only when that current increases
sufficiently, does something in that path (ie. the phone)
fail.
Second, all appliances have internal protection. Protection
that can be overwhelmed if the destructive transient is not
earthed BEFORE it can enter the building.
To have a destructive transient, the transistorized
appliance must have two paths - an incoming and an outgoing
path. Portable phone base stations are particularly
vulnerable; two paths being AC electric and phone line. So
which line did the transient enter on? You have assumed it
was the telephone line. Why?
Furthermore, do you expect to stop what 3 kilometers of sky
could not? That is what ineffective plug-in protector
manufacturers hope you will assume. However in N America,
every incoming phone line already has a 'whole house'
protector installed free by the telco. Does it stop the
transient? Of course not. Effective protection does what Ben
Franklin demonstrated in 1752. He did not stop lightning. He
shunted (diverted) lightning to earth. You must do same.
A protector is not protection. An effective protector does
same thing as an earthing wire. An effective protector
connects the destructive transient to protection. The
protector is not protection. Earth ground is protection. The
protector is simply a connection from that utility wire to
protection. This is what plug-in protectors hope you never
learn.
You don't know if the transient entered on AC electric to
find earth ground via phone line; or visa versa. But we know
this. First, a plug-in protector hopes you will assume a
protector will stop what 3 kilometers of sky could not.
Forget the nonsense promoted by Belkin; who avoids all
discussion about earth ground. The concepts of RJ-11
protection were discussed extensively "RJ-11 line protection?"
on 30 Dec 2003 through 12 Jan 2004 in pdx.computing at:
http://tinyurl.com/2hl53
In the UK, providers of effective protectors for AC electric
are:
http://www.keison.co.uk/furse/furse06.htm
http://www.keison.co.uk/furse/pdf/ma...lies/m2_m4.pdf
For phone lines:
http://www.one.co.uk/catalogue/teleb...otect/22PX.HTM
http://www.keison.co.uk/furse/furse11.htm
http://www.keison.co.uk/furse/furse08.htm
Notice what every effective protector features: a dedicated
wire for a 'less than 3 meter' connection to single point
earth ground. An effective protector only connector the
transient to protection.
How might your phone have been damaged? This figure from
the National Institute of Standards and Technology
demonstrates how bad earthing caused fax machine damage:
http://www.epri-peac.com/tutorials/sol01tut.html
Again, the effective protector makes a 'less than 3 meter'
dedicated connection to earth ground. Same principle is why
BT, connected to overhead wires everywhere in town, need not
shutdown during any thunderstorm. You are strongly
encouraged to review that previous discussion entitled "RJ-11
line protection?". Earth ground (and not the protector) is
protection. No protector is going to stop, block, filter, or
absorb the transient that might damage that portable phone
base station. Therefore ineffective protectors avoid all
discussion about earthing - to make the sale.
The protector is only as effective as its earth ground.
Kris wrote:
> Close lightning destroyed the cordless phone at the weekend, now
> looking to get some phone line surge protection. The adsl router
> survived.
>
> One of the Belkin range seems ok for mains / BT telephone sockets
> but I can't find anything for the RJ 11 lead between the BT ADSL
> faceplate and the router.
>
> .. Or perhaps the ADSL part of the faceplate and / or the router
> have inbuilt protection and no need to worry ?
>
> Chris