Grandstream Audio Series UCM6300A IP PBX supports250 users and includes a built-in instant messaging. NO VIDEO CONFERENCINGOn Premise IP PBX (Audio Only) with No FXO ports, No FXS ports and supporting up to 250 users UCM6300A The UCM6300 Audio series enables enterprises to create strong and scalable unified communication and collaboration solutions. This IP PBX Audio series provides a platform that integrates basic business communications needs such as voice, instant messaging (IM), voice meetings, audio web meetings, data, analytics, mobility, facility access, intercoms,