In article , Mark S.
writes
I've got BT coming Monday to connect my phone line but it's dangling
on the wall due to the previous tennants/owners either smashing it or
stealing it.
The wiring looks to be some older type, black outer with three yellow
wires, green, orange and I think black maybe.

The BT wallah will almost certainly replace the old connection box with
a modern, master socket. If I recall correctly, the old sockets did not
contain a line termination capacitor -- that was carried in the
telephone "instrument" itself...

--
Paul