On May 20, 3:17*am, "Dave Plowman (News)"
wrote:
Must be something wrong with my telephone - and every other one I've seen.
No local earth. Nor would you expect one with a balanced line.

First, you are in the UK where BT only installs earthing on their
end. In North America, every phone line is earthed at both ends.

BT's switching computer is challenged by maybe 100 surges during
every thunderstorm - and no damage. New master socket installations
do not have that earthing - that is even required by code in North
America.

Second, balanced line remains because - well read the previous post
with care. Every wire in every phone line cable gets earthed through
a protector - therefore remains a balance line. What does a protector
do? Performs like an open switch. Only connects a wire to earth when
a surge exists.

Surge protectors don't stop or block surges. See the examples at:
http://www.keison.co.uk/furse/furse19.htm
http://www.tripplite.com/products/pr...?productID=151
The effective protector makes that short (ie less than 3 meter)
connection to earth - that green wire. Each ethernet wire gets
connected to earth ground only during surges. Then that surge need
not find earth ground, destructively, via any switch or network card.
Then that surge will not overwhelm thousands of volts protection in
every ethernet interface.

Third, does BT shutdown service for five days while they replace
that £multi-million switching computer? Of course not. Hundreds of
surges during every thunderstorm and no switching computer must be
damaged. A protector is only as effective as its earth ground. Earth
ground provides ethernet protection.

Another industry professional demonstrates this solution in an
application note:
http://www.erico.com/public/library/...es/tncr002.pdf
Routine is to connect communication wires between buildings and have
no damage. Those who would deny this also claim surge damage is
acceptable. Nonsense.