SIP IP PABX Phone system with 4 to 96 FXS/FXO ports SIP ... users, can be working under NAT for remote IP users by DDNSRecording, Voice mail,Music on Hold,Ring group, Auto- ... Attendant, 3-way-conference;Embedded SoHo IP PBX phone system with 4,8 or 16 FXO analog ports, and ... or VPN, it allow extensions to be boundled with cell phone, and it also directly integrates with VoIP service provider ...