[Dave Moll]

Not related to your problem, but if you are plugging into an extension socket it is worth checking that contact 3 on the socket into which the telephone is connected is wired back to contact 3 in the master socket, otherwise the telephone will not receive a ringing signal on incoming calls (which it is expecting on the blue wire of the line cord). The reason this may not be connected is that many modern telephones don't use it.