Variations of more than 6dB usually indicate a split pair

What's a split pair?

When one wire from the orange pair is used, and one from the blue pair.

Rather than the two wires from the same twisted pair. Probably a very common issue particularly on new builds.

Thanks Andrew. I assume that error, if it exists, could occur anywhere between the exchange and my master socket?

It could but would be a mistake in the wiring by BT (note the external BT side wiring usually has different colour cores to it, than the internal stuff).

Well, most of my line is underground but the last 400 yards is overhead and I know for a fact that there are 5 junction boxes in that stretch due to numerous breaks over the years! Could be in one of those

If this split pair exists, would it affect the downstream attenuation? I am straight line 2.3km from exchange with 40dB attenuation.

Nope

Roger!!

I knew it couldn't last

Mon 07 Dec 2009 16:59:09, Noise Margin= 4.5, Sync Speed= 6368, 2 days, 8:35:17

Mon 07 Dec 2009 16:59:24, Noise Margin= -8.0, Sync Speed= 6368, 2 days, 8:35:32

Mon 07 Dec 2009 16:59:54, Noise Margin= 12.5, Sync Speed= 4672, 0 days, 0:00:13

In reply to a post by Andrew_W:

Well, most of my line is underground but the last 400 yards is overhead and I know for a fact that there are 5 junction boxes in that stretch due to numerous breaks over the years! Could be in one of those

If this split pair exists, would it affect the downstream attenuation? I am straight line 2.3km from exchange with 40dB attenuation.

Is the last 400 yards in the street, or is it over your property ?

I inderstand that BT will re-lay the cable for free, if you dig and supply the duct.

In reply to a post by zebedeee:

Is the last 400 yards in the street, or is it over your property ?

I inderstand that BT will re-lay the cable for free, if you dig and supply the duct.

It's over my property. I dug a trench 200 yards long some years ago to carry a water pipe and can still feel the pain Think I would rather put up with the n/m variations!! Nice thought though