1.Support three SIP servers running at the same time
2.Provide two backup SIP servers

    IP Phone system: CPH-665 

    Features:

Support three SIP servers running at the same time        Provide two backup SIP serversVoice code: G.711A/u, G.723.1 high/low, G.729a/b, G.722, G.726G.168 compliant echo cancellation(64ms/96ms/128ms)VAD (voice active detect) CNG (comfort noise generation)       Support Voice Gain Setting       GSM, AMR, ILBC          Support bridge and routing modeDTMF Sip Info, DTMF Relay, RFC2833Support PPPoE, (used for ADSL, cable modem connecting)  VLAN(802.1P  802.1Q)Support DMZ, DNS Relay, SNTP Client, FirewallSupport network tools: ping, trace route, telnet clientWeb administration, telnet configuration and keypad operationSupport HTTP, FTP, TFTP software upgrade or configure.Hotline,Alarm clockSpeed dial Phone book(140 records)Call Forward, Call Transfer, 3-way conference callsCaller ID, Do not Disturb, BlacklistEight different ring tonePoE or FXO (optional)