Joined: 28 June 2002
After a great deal of searching for information, I still can't find a simple answer to the question of whether, and how, one should surge protect a DSL line.
Given that ADSL modems/routers are quite expensive, replacing one or more due to a lightning strike etc seems like a way to spend a lot of money, and I can definitely recall times when I've had unprotected modems fail just after a major storm.
From my searching I've gleaned three pieces of information (some related to the UK):
1) BT fit a surge protector in the master socket, but it's entirely differential mode across the twisted pairs (lightning surges usually present themselves as common mode as I understand it).
2) DSL is a high frequency signal and so any protector must be of very low capacitance to avoid loss of what is already probably a poor signal in most areas that suffer from lightning issues.
3) Any surge protector worthy of the name needs a proper earth to dump the surge to ground.
Is this accurate? What are other people's experience and/or advice on the subject? Has anyone ever come across a decent DSL surge protector that doesn't degrade signal, and has a chance of protecting sensitive comms equipment?
I've struggled to find any at all that are designed to deal with a high frequency signal. Presumably they exist - what are BT and telcos using?
Thanks in advance for any advice.