When i connect my modem wire to the phone socket, it causes a phones to ring. There are 3 connected to the same line, and if you remove the cable of the ringing one another one will ring. I had this problem before and it was solved by changing the cable, i have recently changed it and have had no problem, on the other pc or the laptop it is fine, on this machine with another cable it is also fine. Any ideas what it is?
There is a reversal somewhere. You will have to remove the front plate of each socket and check the colours of the wires on pins 2 and 3. Pin 2 is normally Blue with White rings, Pin 3 Orange with White rings.
The colour is not important, but all pin 2s should be connected together, same with pin 3s.
Agree that the 'phone sockets are probably not all wired the same. Check that each extension socket has same colour wire to connections 2 and 5 (the line,usually bluewhite/whiteblue) and 3 for the ringer(usually orange).Same goes for connections at the removable plate on your master socket. If still problems remove the plate off master socket then undo the exposed two screws and you will find two wires connected to screw-down terminals, this is the main line in and may be reversed, disconnect and swop polarity.