sg-910 is a kind of voice communication terminal which is based on wide band and independent of pc (personal computer). voice features:  support sip rfc3261 rfc3262 rfc3265  support iax2  codec: g.711a/u, g.729,g.729a/b  echo cancellationz:support g.168  support voice gain setting, jitter buffer, vad, cng,  nat transverse: support stun client, vpn  sip support sip domain, sip authentication (none, basic, md5), dns name of server, peer to peer  sip support pubic/private server. can connect to public server 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/waiting  call control features:  flexible dial map  support hotline....