... least cost calls 120 IP users Billing, MOH, IVR, Recording All-in-One SIP IP PABX for SOHO useressupport ... 4 to 96 analog ports (extensions and pstn trunks)up to 120 IP ... 8,16,24 FXS local extensions; and 60 IP users in local or remote, support SIP and DDNS, ... its flash memory capacity, RT20 also supports built-in IVR, calls records, and downloads for color ring ...