[geeks] debugging house phones

[Porkchop]

It really sounds like there is an electrical fault somewhere on the 
line. I'm as much an ee as I am a trapeze artist, but my advice 
(since you haven't fixed this since you posted tuesday) is:

Option 1: Get the insurance plan... most telephone companies have the 
option of you paying an extra (extremely reasonable fee) to support 
your house wiring. Then you can call them and they'll deal with it no 
matter what.

Option 2: Keep trying it yourself.

I'd hook up all three phones directly to the mod jack in the NID. If 
it dosnt work there, call the phone co and lie to the automated 
computer. Explain it to the linemen when he comes out.

You say that each jack in the house has a dedicated pair going to the 
basement... is it a clean junction box? Are any of the runs excessive?

You say the modem on B hangs up when A gets a ring. If I remember my 
telco tech well enough, a ring is generated by a voltage spike... 
90VAC at 20hz or something like (voice is tiny voltage compared). If 
there is any sort of galvanic connection across the pairs, it may 
cause your hangup... and bring the voltage available to the ringers 
on those three phones down. You may be able to test this by 
disconnecting both lines at the NID, then testing for 
continuanty/resistance in the basement (or perhaps at the NID if you 
have customer-side contacts you can touch).

If you notice a difference on wet verses dry days (or think you do), 
there can easily be a problem on the telco side.

Hope this helps. Best of luck,
-porkchop