rj168-300 is 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 synchronously  codec: g.711a/u, g.7231 high/low, g.729  echo cancellation: support g.168, and hands-free can support 96ms  support voice gain setting, jitter buffer, vad, cng, dual gk, call forward, and peer to peer  nat transverse: support stun client, citron, avs  sip support sip domain, sip authentication (none, basic, md5), dns name of server, peer to peer  sip support pubic & private server. can connect to isp and private sip server at the same time  sip support dual public server  dtmf: support sip info, dtmf relay, rfc2833  sip application: support call forward/transfer/holding/wait