SIP IP PABX Phone system with 4 to 96 FXS/FXO ports SIP trunks ... , Auto-Attendant, 3-way-conference; Embedded SoHo IP PBX phone system with 4,8 or 16 FXO analog ports, and 8 ... ; The RT20 is an All-in-One converged communication system for small and mid-size offices, home offices and ... VPN, it allow extensions to be boundled with cell phone, and it also directly integrates with VoIP service provider ...