The Internet phone has 5.8 GHz digital spread spectrum technology. It is expandable up to 4 handsets using one connection. Built-in WAN and LAN ports FirewallIntegrated broadband telephone adapter included. One-touch access to Vonage voicemail service. Security protectionVPN pass-through. Web-based browser. The features include 50 name and number phonebook directory, backlit display, caller id/call waiting, conference an outside call between handsets and handset speakerphone. There is an Intercom between handsets. It transfer calls between handsets.