Install the Yeastar YST-S2 module on compatible Yeastar MyPBX or S-Series modular phone systems. The module brings two FXS ports to the IP PBX. MyPBX is a line of modular phone systems that let you customize connectivity types. Combine several modules on one IP PBX, and truly interconnect your existing endpoints and services. This FXS module supports devices like analog phones and fax machines.