Yeastar S300 IP PBX delivers enterprise-class IP telephony services with a base configuration that supports 300 users and can be expandable to 500 users. Yeastar  S300 grows with you business and supports up to 24 analog ports, up to 24 BRI ports, up to 3 E1/T1/PRI ports, and up to 6 GSM channels. S300 Supports D30 Module of increasing the Capacity and EX30 PRI Module.