Hi,
Whilst moving a BT master socket I checked the incoming voltage.
The B connection reads -50v,
and the A connection reads +4.2v
with nothing else connected.Is this OK?

I assume you know you are not really supposed to touch the BT line or the master socket?

Anyway there is about 50V DC between the A and B legs of the pair. You might not get exactly that voltage measuring between either leg and earth however. Just don't have your fingers across the wires when the phone rings though. That will give you a nasty tingle!

Thanks for your concern Chris.
A-50 B+4.2 does not appear to be a "balanced" line to my way of thinking.
I don't wish to fork out a handfull of twenties to BT only to be told its fine. So I'd be grateful if anyone could tell me what Line B should read in relation to A.... A being apparently correct @-50v,

If you measure each line with respect to earth then you will get odd voltage readings as the phone line is not balanced about earth, it is "floating". You will never see an Openreach engineer measure from either leg to earth unless he suspects a fault where one leg or the other has become short circuited to earth. So you always measure the voltage between A and B only and that should be about 50V give or take a bit depending on the line quality.

Whether that counts as being balanced or not is another matter . I usually think of balanced when dealing with AC signals such as the voice signal. That is balanced in that identical signals should be on both A and B legs but out of phase (ie A voltage positive when B negative and vice versa).

That title had me confused.

I thought Andy Gray wanted a few pointers!

Cheers Chris. Thats put my mind at rest.
.
Heinz. LOL. Woman gets mans job and 2 blokes get sacked.
It'll all end in tears!

As I said originally. be careful poking about with the phone wires. The 50V DC might not even tingle but believe me you WILL feel the ringing voltage - I know from practical experience
.

Is this some reference to that strange sport they play on a field with round balls that they kick about with their feet? Never understood the appeal myself.

Now oval balls that you pick up and run with is a different matter

Dim and very distant past for me but I couldn't agree more.