said by gcerullo :
Yes, there is a Corning POTS splitter. It was installed when the original Fibe 25/7 service was installed.
I'm curious though why the interruption to the service only happens during the distinctive ring of a long distance call and not with local calls. Also, why would it exhibit this behaviour only while the phone rings but not while on a call. This seems very strange to me and I suspect that the problem lies further back along the circuit and not with the lines in or around the house.
There is a small metal junction box of sorts on the lawn of the house across the road from me that is damaged and has been known to cause problems in the past, mainly static on the line, when it has been disturbed. I've called Bell numerous times about it but the most they have ever done was wrap it in plastic.
There is some voltage on the phone line everything it rings... so depending on the ring, it will cause this type of issue.
Your metal junction box most probably is the cause then.