Yealink"s new 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 > Wideband codec: G.722 > Narrowband codec: G.711(A/μ), G.723.1, G.729AB, G.726, iLBC > 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 por