1 to 4 GSM channels card for asterisk,elastix IPPBX the card can be GSM + FXO + FXS mixed ports easy to install and use Feathers:* Support the access of wireless(GSM and CDMA), PSTN, Phone.* Supports GSM, CDMA two kinds of wireless communication standard.* Support GSM: 850M/900M/1800M/1900M, CDMA: 800M.* Support 4 channels, user can choose to insert wireless, FXO or FXS module in each channel.* ...