OpenVox G400P1 4 Port GSM PCI card with 1 GSM Module Expandable to 4 Channels Fully Support Industry Standard: PCI 2.2 1 SIM card per GSM channel (SIM card not included) Works with 3.3v or 5.0v 32 bit PCI Slots It is used to build a PBX system based on Asterisk Open Source platform