... .0 (RFC3261) and correlative RFCs; 2)Can connect to SIP1 and SIP2 server at the same time; 3) ... Gain Setting, VAD, CNG·Full duplex hands-free speaker phone·NAT transverse:support STUN client·SIP support SIP domain, ... (none, basic, MD5), DNS name of server, Peer to Peer/ IP call·SIP support 2 SIP lines. Can connect ... to SIP1 and SIP2 server at the same time·DTMF ...