OpenVox A400P01 4 Port Analog PCI Base Card with 1 FXO Modular Design: Up to 4 FXS, FXO or mixed FXS/FXO ports per card Support Industry Standard: PCI 2.2 with both 3.3 V and 5 V PCI slot can be used for A400P. Support GPL Software driver used with zaptel Scalable: Just add additional cards to extend system Easy to use: Full software and hardware compatible with Asterisk Drivers World Wide Usable: Configurable line interface to meet global telephone line interface requirements