4,8,12,16 FXS/FXO ports PCI 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 ... Services6, Call Centers7, Prepaid Calling Card System8, Callback Service9, Traditional Calls/VoIP Calls Conference Hardware and software requirements: 1, Interface: PCI 2 ...