REX500 IP-PBX provides versatile solutions containing voice/video call, voice message broadcast, Fax, call recording, mobile extensions to fulfil an enterprise with 500 employees. The REX500 can connect IMS of operator, and provide multiple models with different combinations of FXO and FXS ports. The high availability featuring primary-standby, dual-redundant Gigabit-Ethernet port and dual AC/DC power supplies allows the REX500 to be applied in many scenarios which are highly sensitive to reliability.