OpenVox A400P is designed to be fully compatible with the TDM400P Asterisk Analog Telephony card.
The A400P supports up to a total of 4 FXO-100 and/or FXS-100 modules.
The FXO-100 (red) module allows the A400P card to terminate analog telephone lines (POTS). The FXS-100 (green) module allows the A400P card to terminate analog telephones.