The S400M FXS module allows 800 Series or 2400 Series analog cards to terminate four (4) analog stations per module.
FXS is an interface that connects to a station, such as an analog telephone or the FXO interface of another PBX. It provides ringing voltage and battery to the FXO devices. 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.
Note: To use the S400M module, you must provide 12V DC power to the TDM800P card or TDM2400P card, either from the computer's power supply or from the Analog FXS Module Power Supply.