Im not sure what a split line is either.
Just did a google and came up with this page
http://www.serviceview.bt.com/List/current/docs/Exch_Lines.boo/14061.htmA PSTN Split Line is a standard analogue line provided, primarily for voice services, on a metallic pair on which the high bandwidth has been rented by BT to another licensed operator (OLO) for the provision of services to the end-user.But a bit further down it states
The following services will not be provided over PSTN split lines
- BT ADSL However something else came up too
http://forum.digitalspy.co.uk/board/showthread.php?t=459007Where it would indeed seem to indicate that BT are using that term to describe "LLU LINE SHARE PSTN"....
or more specifically what we know as SMPF (Line Sharing Metallic Path Facility) LLU.
So yep TT if they are using LLU at that particular exchange.
---
The symptoms you describe would seem to indicate poor filtering.
>> Could the fax machine be incompatible with a BB line?
Shouldnt make any difference, if the line was filtered correctly, since fax uses the same lower frequencies as voice.
>> Would the service suffer due to being on a split line?
In theory again, shouldnt make any difference, since it would only be the higher frequencies at the exchange that go onto the LLU DSLAM. The 2 frequencies are kept separate (at the exchange).
Is it a long line that could be suffering from low SNR problems anyway. Therefore by plugging the modem straight in to the master socket its going to receive the best signal. The line could be so marginal that just one thing "tips the balance".
In which case yes the NTE5 adsl filtered faceplates could very well help.
I believe if you are on a long length line then normally BT will fit these for free as part of their commitment to bringing adsl to everyone. However if they still do it for free when its SMPF is another matter and I couldnt say :/