I have an IP 403 system that primarily uses Digital Station phones. I need to set up a 4620sw IP phone for use on the system. The phone comes up and gets an IP address and I am able to program it with a name and extension. But, when I go off hook I immediatly get a message "Unobtainable". There is probably more programming that needs to be done, but I can't find any programming documentation for the phone. Thanks.