... SIP users, SIP trunks Billing, Recording, Voice mail Tie trunks for multiple IPPBXs Embedded IP PBX with 4,8 or 16 ... ; The RT20 is an All-in-One converged communication system for small and mid-size offices, home offices and branch offices. It ... , RT20 also supports built-in IVR, calls records, and downloads for color ring back tones.Model NameAnalog ExtensionsAnalog TrunksSIP usersSIP TrunksRT20 ...