The Yeastar IP PBX S50 is designed for up to 50 users and 25 concurrent calls,supports 4 onboard module slots

Yeastar O2 Module with 2 FXO ports allows you to connect analog PSTN lines to your Yeastar S-Series IP PBX, expanding call capacity easily and efficiently.

Yeastar SO Module provides 1 FXO and 1 FXS port, to connect both a traditional phone line and an analog extension to IP PBX system easily.