The sip-t21 uses an extra-large 132 x 64-pixel graphical lcd showing a clear 5-line data display offering smoother user experience plus hd voice characteristics. This phone uses dual 10/100 mbps network ports that are ideal for extended network use with t21 supports two VoIP account, simple, flexible and secure installation options, plus support for ipv6, open vpn and a redundancy server. Specification > audio features > hd voice: Hd handset, hd speaker > dtmf: In-band, out-of-band(rfc 2833) and sip info > full-duplex hands-free speakerphone with aec > vad, cng, aec, plc, ajb, agc phone features > 2 VoIP accounts > call hold, mute, dnd > one-touch speed dial, hotline > call forward, call waiting, call transfer > group listening, sms, emergency call > redial, call return, auto answer > local 3-way conferencing > direct ip call without sip proxy > ring tone selection/import/delete > set date time manually or automatically > dial plan > xml browser, action url/uri > integrated screenshots > rtcp-xr interface > 2xrj45 10/100m Ethernet ports >power over Ethernet (ieee 802.3af), class 2 > 1xrj9 (4p4c) handset port > 1xrj9 (4p4c) headset port. Poe (powered over Ethernet), power supply not included.