Plug it in to the line directly in the phonebox. What it does it it comes in from the street then foes into a grey "Telephone Company" box. Take a phone out there and plug it in to see if that is dead. If so, then it is your tele-company. If not, then it is internal.

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-Justin

91 560 SEC AMG - other dogs dd
01 Honda S2000 - dogs dd
07 MB ML320 CDI - dd
16 Lexus IS250 - wifes dd

it's automatic.