... at the same time 2.Provide two backup SIP servers IP Phone system: CPH-665 Features:Support three SIP servers running at ... and routing modeDTMF Sip Info, DTMF Relay, RFC2833Support PPPoE, (used for ADSL, cable modem connecting) VLAN(802.1P 802.1Q)Support ... , FTP, TFTP software upgrade or configure.Hotline,Alarm clockSpeed dial Phone book(140 records)Call Forward, Call Transfer, 3-way conference ...