Thanks, Partial.
Another snippet of knowledge.
If that is the fault, I suspect that it would affect all incoming calls on that land line, eg from mobiles as well as, say, international etc.
Are there any known problems with making out-going calls on land-lines with such a fault, which would help in possibly confirming it?
Is it a fault that is associated with the described circumstances, of apparently being related to the outside line at the pole?
If most calls to and from this house are on mobiles only, both ways, the fault could be "undetected" etc for a long time from when it arose, unless it also impinged greatly on broadband usage.
--------------------
Just found amongst many-
https://en.wikipedia.org/wiki/Ringtone
Background
"
In POTS switching systems, ringing is said to be "tripped" when the impedance of the line reduces to about 600 ohms when the telephone handset is lifted off the switch-hook. This signals that the telephone call has been answered, and the telephone exchange immediately removes the ringing signal from the line and connects the call. This is the source of the name of the problem called "ring-trip" or "pre-trip", which occurs when the ringing signal on the line encounters excessively low resistance between the conductors, which trips the ring before the subscriber's actual telephone has a chance to ring (for more than a very short time); this is common with wet connections and improperly installed lines.
"
Edited by deleted (Wed 31-Dec-14 07:15:36)