... , 3-way-conference; Embedded SoHo IP PBX phone system with 4,8 or 16 FXO analog ports, and ... SIP and DDNS, Can be working under NAT; based on Linux OS, GUI for management; The RT20 is ... an All-in-One converged communication system for small and mid-size offices, home offices and ... analog trunks and analog extensions, and but VoIP based SIP trunks and remote extension as well. Using ...