... Speaker Phone Support Voice Gain Setting, VAD, CNG DTMF:Support SIP info, DTMF Relay, RFC2833 Full duplex hands-free speakerphone Support ... connect to SIP1 and SIP2 server at the same time SIP application: support Call forward/ transfer/ holding/ waiting / 3 way ... intercom/pickup/join call/click to dial/call park SIP support SIP domain, SIP authentication (none, basic, MD5), Peer to Peer/ IP call ...