FYI
NEC engineering will help you get the IP phone working straight into the IP card. They will recommend what equipment to use between the IP phone and the phone system after that they are done.It is up to the end user IT dept to make things work from there.(There are so many variables for fire walls and other security measures out there it would be impossible for NEC to know them all).
Tip and Ring is right you have to use VPN.

I wish I could be more help
Dan S


We get old too soon, smart too late