The SIP phone a kind of voice communication terminal which is based on wide band and independent of PC (personal computer). Voice Features:Support IAX2 and SIP RFC3261 synchronouslyCodec: G.711A/u, G.7231 high/low, G.729Echo cancellation: Support G.168, and Hands-free can support 96msSupport Voice Gain Setting, Jitter Buffer, VAD, CNG, dual GK, call forward, and Peer to PeerNAT transverse: ...