Yeastar P570 PBX 300user 60channels, Basic features. Upgradeable. Yeastar P570 supports 2 expansion boards. You can install EX08 board or EX30 board according to your needs.Used to connect an E1/T1/J1 line. Up to 4 modules and 8 RJ11 ports are supported on the expansion board. The 8 RJ11 ports can be used to connect to different objects: FXS port (green light): For the connection of analog phones or fax machines. BRI port (orange light): For the connection of BRI lines. FXO port(red light): For the connection of PSTN lines or FXS ports of traditional PBX.