On our Axxess system, you need to point them to the IPRC card. You will also need to program one of the lines on the IPRC card with the MAC address of the IP Phone. You either do that from the software database programming, or via the web config on the card itself depending on firmware version.

Other Inter-Tel systems may be different...I'm not a tech, just a sysadmin who inherited an Axxess system.