... Phone system with 4 to 96 FXS/FXO ports SIP trunks for least cost calls 120 IP users ... working under NAT for remote IP users by DDNSRecording, Voice mail,Music on Hold,Ring group, Auto-Attendant, ... system with 4,8 or 16 FXO analog ports, and 8,16,24 FXS local extensions; and 60 IP ... 20 4 60 60 System Features Built-in SIP Server SIP Trunk Auto Attendants Distinctive Greetings Greeting Mode Scheduling ...