I have a 9 pin connection for my I/O port on the call accounting buffer box I need to connect to my BCM 400. How does the physical connection work? On my PBX I just plug my 25 pin modem cable in to my I/O port and the other end (9 pin) in to the buffer box, but I've never done this with a BCM before. Also, where is this turned on in the BCM?