VoxStack series VoIP gateways are the innovative products from OpenVox. They are the industry FIRST Hot-Swap Asterisk-Based VoIP Gateways. VoxStack comes with OpenVox creative modular design that provides up to 5 plug-in VoIP gateway modules which could support combination of different telephony interfaces including GSM, FXO/FXS, BRI, E1/T1 (Note: the current version supports GSM/FXS interfaces, other interfaces will be added soon). The VoxStack series gateways are industry FIRST Asterisk-based gateways that support GSM/FXS interfaces. It provides full flexibility and maximizes the asterisk functions on the VoIP gateways. The VoxStack VoIP gateways support up to 20GSM channels or 40 FXS ports or any combination of five GSM/FXS gateway modules at maximum.