The GXW4004 FXS Series is an ideal solution for businesses looking to connect one or more lines of a traditional PBX to a VOIP phone system or provider. The GXW4004 features 4-port FXS interfaces for analog telephones, dual 10M/100M network ports with integrated router, PSTN life line in case of power failure, and an RS232 serial port for administration. » Support for 2 SIP account profiles, caller ID for various countries/regions » Support for T.38 fax, flexible dialing plans, security protection (SIPS/TLS), and comprehensive voice codecs