Grandstream UCM6301 Unified Communications IP PBX (Up to 500 Users, 75 Concurrent Calls, 75-Participant Audio Conference, 1080p Video Conferencing, 1×FXS, 1×FXO, 3×Gigabit RJ45 Ports with PoE+, USB 3.0, SD Card Slot, Asterisk 16-Based, GDMS Cloud Management) Up to 75 concurrent calls audio conferencing** conference rooms** with Full HD conferencing support (RJ11) Gigabit Ethernet ports** with PoE+ support 3.0** port and SD card slot G.722, G.729, T.38 Fax** codecs ** video codecs 1