On Sun, 25 Aug 2013 11:02:45 +0100, polygonum
wrote:

It is a fair old drive to get there so the ideal would be something I
can explain to her. If it is simple enough she can do the test when the
line is bad and, hopefully, identify the issue. But if I need to go
over, so be it.

There are well known issues with some DECT phones and ADSL but these
usually show up as noise on the line. The phone system is simple and
fault finding is a matter of being very methodical.

The first test to try when the line appears faulty is simply to unplug
the ADSL filter, splitter and DECT phone and her existing phone and
plug only a known good simple and wired phone directly into the phone
socket on the master box. The simpler the phone the better (Charity
shops and the like are often a good source of appropriate phones).

If that solves the problem leave everything disconnected and replace
the test phone with her normal phone. See if the problem returns.

If it doesn't, plug everything else back in one at a time testing at
each stage.

Is there a Sky box in use?

You might find it useful to make up a simple test sheet for her with a
column for the action (such as unplug everything bar the test phone)
an a space to record the result.