GSM-IP-PBX ( GSM VOIP Switch ) The TDM800/400 is a PCI 2.2 & PCI Express 1.0 compliant card that supports FXS and FXO station interfaces for connecting analog telephones and analog POTS lines through a PC, It supports a combination of FXS +FXO for a total of 8 lines. Using Asterisk PBX software and standard PC hardware a user can create a SOHO telephony environment which includes all the sophisticated features of a high end PBX / Voicemail platform.