Yeastar S20 is a stand-alone telephone system offering an unrivalled range of features to small business with less than 20 users. It supports 10 concurrent calls and various combinations of telephony ports including FXS, PSTN, ISDN BRI, and GSM/3G. This guide describes how to install the S20 and how to log in the web GUI to configure the system. Once you complete the installation, refer to the Yeastar S-Series Administrator Guide for instructions on how to perform configurations on the system.