4,8,12,16 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 ... Applications: 1, PBX/IVR Services2, VoIP Services3, VoIP Gateways4, FAX Server, FAX On Demand5, Voice Mail Services6, Call Centers7, Prepaid Calling ...