the A/B is a pass through, so you can test its electrical connectivity. The effect on the speed is caused by having all that extra wire hanging off the end which appears to be creating an imbalance or picking up interference.

It is common to get a low speed at the faceplate if an A/B extension is connected as you're not at the end of the line, but in your case you get the same at the end of the extension wire.

The solution is of course to put the router at the master socket and use ethernet / homeplugs / wireless to bridge the gap.

In reply to a post by hittyh:

ive seen on other forums people having luck with the pressac plate from Clarity. Anyone here had any joy with them?

I use the Pressac filtered faceplates. They appear perform more than adequately to SIN 346 as specified by BT.

In reply to a post by hittyh:

I remember my alarm has a tel wire too. Ill need to check the main box for the alarm to see if its connected to white or black.

The alarm is the equivalent of a Sky box modem, a telephone or any other telephone voice equipment - it kills the ADSL signal. It needs to be filtered: i.e. not connected directly to the A & B terminals.

Yes. Use this this