mahmood,

TELCO isn't making things up they tested the line from the "test trap" where the line is "looped back" prior to distribution to your specific trunk.

You might ask to what line specification it was characterized (in the US "C1" conditioning is typical for voice grade lines).

This level of testing indicates the problem exists form the point of distribution to your connection point. This (as you suspect) doesn't just mean the premise wiring but could also entail trouble between your premise and the distribution point.

Now your solution is a model of why telephone line interfaces are built as robustly as they are. I was always told the you could expect anything from a subscriber and recall thinking "ya right" when i was told that it was not unlikely that a subscriber would plug the line to mains power. So thanks, you validated some very grumpy old men (god bless 'em).

I suspect your line clears up because you cause a trunk alarm and you are moved to a different switch group. If this is true it would indicate that your service quality suspicions are right on.

I don't know your location but if your "link" has any residual analog components (i.e. analog FDM MUX) if was very common to limit channel deviation to allow the largest possible switch groups to propagate.

I don't know if there is much analog still out there but if so it would be on possible explaination. Your line "peterbation" might cause your line to be moved to a digital mux switch group where line groups are TDM and fixed.

who knows, but a great post!

regards,
p