Telephony interface cards are PCI or PCI Express expansion cards that connect computers running Asterisk directly to legacy phone lines, phones and phone systems. The cards convert the legacy signaling and media into Asterisk's internal formats.
Telephony cards are the essential hardware components of telephone systems that integrate with computers (i.e. CTI). Telephony cards are installable circuit boards that usually fit into PCI slots in computers. They can perform all the main features of a telephone system. The card can be used for PBX orIVR systems, call recording, dial dictation, DTMF tone detection/generation, analog-VoIP conversion, etc.
Cards are made to support analog, digital or hybrid phone systems. Both FXS and FXO ports are available, depending on the model. Ports usually range from 2-32, though there are boards with a much higher number of ports.
Analog Interface Cards
Support for analog or "POTS" (Plain Old Telephone Service) lines. The analog cards are provided in four, eight, and twenty-four modular port varieties
Digital Interface Cards
Digium produces a complete line of digital interface cards for T1/E1 and ISDN connections. The digital cards are provided in one, two, four and eight port varieties
Hybrid analog and BRI cards are available to provide a mixed-mode operations from a single device. The hybrid cards are available to support up to 8 ISDN BRI ports.