> I can't seem to find or remember the resistance to earth status of a live telephone circuit with its 0v and 50v A and B connectors.
SIN 349 says 100 kΩ
http://www.btplc.com/sinet/SINs/pdf/349v2p5.pdfPresumably in the case of ground potential rise, where you have a long line and the potential of the local earth at your house is different from that at the far end (i.e. at the PCP or at the exchange or whatever, don't know which is earthed), then you're going to heat up the conductors with current flowing trying to level the difference, aren't you? I'm not sure it's going to make much difference concerning lighting strikes, somehow I would think not. I wouldn't do it myself, but not because of lightning.
It's very interesting that you got an SNR improvement, makes sense. I should have said that if the far end isn't even earthed at all, then that's a different matter of course.
I have three ‘lines’, delivered as three pairs in two drop cables, and the one with the fastest downstream sync rate is the one that's alone in its drop cable. The difference is slight, but always consistently there.