... 8,12,16 FXS/FXO ports PCI/PCI-E card Asterisk, FreeSwitch, Elastix Detecttion of busy tone, DTMF, FSK Adjustable line gain PCI/PCI-E analog card ... for Freeswitch and Asterisksupport 4 to 16 FXS/FXO ports ... Call Centers7, Prepaid Calling Card System8, Callback Service9, ...