Yeastar provides flexible telephony interfaces combination while allowing for future scalability with unique modular design. Besides the built-in rich SIP capabilities, S-Series lets you decide what types of extensions and physical trunks you need in your telephone system. When your business grows, adding more users and concurrent calls is also possible with S-Series.

With Yeastar S-Series, all the telephony interfaces are modular and customizable, whether it’s FXS, FXO, ISDN BRI, GSM/3G, or E1/T1/PRI. S20 has 2 onboard module slots, S50 and S412 supports 4. S100 and S300 require the combination of Expansion Board and Telephony Module to add telephony interfaces. S100 allows 2 Expansion Boards and S300 supports 3.