2FXO + 2FXS is mixed interface of foreign exchange office and foreign exchange station that connect to office and station. It includes 2 FXO ports and 2 FXS ports, and can be combined with BRI, PRI and GSM module. FXO interfaces are used to connect your PBX to the PSTN. One FXO channel is required for each line you receive from your telco. FXS interfaces are used on the inside of your PBX; they do not connect directly to the PSTN. One FXS channel is required for each telephone that you wish to connect to your Asterisk system. The Analog Station Interface (FXO) provides the following features:
The IPX-21SL module applies to PLANET's IPX-2100/IPX-2500, IPX-2200, and IPX-2100v2/IPX-2500v2 IP PBX System with 4 RJ11 ports for connection.