Yeastar S2 module is a module with 2 FXS ports to terminate two analog telephone or fax machines. It is compatible with Yeastar S-Series VoIP PBX and P-Series PBX System.
Yeastar SO module is a module with one FXO port and one FXS port to offer a unique PSTN failover function, enabling you to make/receive calls even when system powers down.
