I've had the above fault (line loses dial tone but BB still works) on a few of the lines I'm responsible fo. I am reporting them to BT and getting them fixed, but I am purplexed as to how a line can work at all if there's a break?
These faults were deffo line pair faults (crackles before dial tone lost).
I can't understand how BB will run on one half of a pair though? I would have thought that the electrical circuit would be incomplete.