IP phone Sip support 3 simultaneous SIP lines or 1 IAX2 line Support phonebook 500 records Superior quality and competitive IP PhoneSupport SIP 2.0 (RFC3261) and correlative RFCsSupport IAX2Supports 3 SIP lineFull duplex hands-free speakerphoneSIP support SIP domain, SIP authentication (none, basic, MD5), DNS name of server,Peer to Peer/ IP callDTMF:Support SIP info, DTMF Relay, RFC2833Advanced ...