AND to add to it all ! I am not an ex-BT man (but as Alan NYK will attest have worked within the system) It is not unknown for strange effects to be manifest at points where the copper network changes into other manifestations including different metallic elements as conductors and/or transformations to or from optical fibre etc.etc.

 

Try checking around street cabinets and large "manhole" covers emblazoned with the logos of telecoms and utility companies (don't just look at Bravo-Tango).

 

As the old maps used to say "there be dragons" !

 

Pat g4gvw