The Yeastar S20 is a hybrid PBX phone system designed for up to 20 users and up to 10 simultaneous calls, specifically tailored to the needs of small offices and businesses. As an all-IP system, the Yeastar S20 can be used with VoIP connections and IP phones. There are no additional costs for licenses, update, or maintenance contracts. Optionally, it can be expanded with modules to include analog extensions as well as analog, ISDN, GSM, or UMTS trunk lines.