Hello, I have never set up a phone system before and am need of help on setting one up. The system has 3 lines and 5 extensions, although the 5th is connected directly to the partner system. I tried to initialize the system, but when i try to dial intercom 777 i get a busy signal... also is there a way to tell if we have a partner control unit, primary carrier or expansion carrier? thanks, i know this is a lot but i have no clue what im doing...