SIP IP PABX Phone system with 4 to 96 FXS/FXO ports SIP trunks ... on Hold,Ring group, Auto-Attendant, 3-way-conference; Embedded SoHo IP PBX phone system with 4,8 or 16 FXO analog ... or VPN, it allow extensions to be boundled with cell phone, and it also directly integrates with VoIP service provider networks ...