If you buy decent surge protectors and assure your grounding is good,
there is no reason to ever unplug anything.
I am in the lightning capital of the world and I have not lost
anything in 30 years.
I think it's still healthy to ask the question, of whether
certain types of surge protectors affect ADSL. That isn't answered
here, but at least someone asked the question.
https://community.bt.com/t5/ADSL-Co...rge-suppressor-affect-my-BB-speed/td-p/375299
The original phone network, only has to pass 4KHz, and so impairments
to the line are allowed to be different, than they would be if attempting
to pass a megahertz baseband signal (2.2MHz on ADSL2+).
In the pictures here:
http://www.kitz.co.uk/adsl/btsockets.htm
the BT main plate uses something I don't recognize.
http://www.kitz.co.uk/adsl/images/phone/components.png
Is that a gas tube ? It looks too thick for a MOV.
One difference between their phone system and ours,
is their ringer signal is carried on a third wire. Whereas
our ringer is HV AC carried on the line pair.
*******
If your modem is capable of reporting line statistics,
you can compare performance (noise margin) with and without the surge
protector in place, and see if it makes any difference.
I worked with an engineer, who was tasked with putting
surge suppression on an Ethernet interface (higher frequencies
than ADSL), and his comment at the time was that it
was pretty difficult to find a protection device that
didn't degrade return loss. He was experimenting with a
semiconductor device, which has two devices in series
inside, the first device with a very low junction capacitance,
the second device more robust. And the combination was
intended to keep capacitance down to the picofarad level.
But the device probably doesn't have all that high a surge
rating. I didn't look at all the details at the time,
but at least noted there was yet another flavor of
protection available.
*******
So I plugged return loss into the search engine, and found this
article.
http://www.epanorama.net/newepa/2012/07/30/adsl-overvoltages-and-protection/
And rather than worry about the details, all I can say is
you'd want to do a noise margin test with and without the
surge protector in place, to see if the surge protector
might be the wrong type.
Paul