I have personally not used Asterisk. But according to the Asterisk Web site, you will need an additional program. See below.
Loadable Module APIs:
Four Application Program Interfaces (API) are defined for loadable modules, facilitating hardware and protocol abstraction. Using this loadable module system, the Asterisk core does not have to worry about details of how a caller is connecting, what codecs are in use, etc.
- Channel API - the channel API handles the type of connection a caller is arriving on, be it a VoIP connection, Integrated Services Digital Network (ISDN), Primary Rate Interface (PRI), Robbed bit signaling, or some other technology. Dynamic modules are loaded to handle the lower layer details of these connections.
- Application API - the application API allows for various task modules to be run to perform various functions. Conferencing, Paging, Directory Listing. Voicemail, In-line data transmission, and any other task which a Private Branch Exchange (PBX) system might perform now or in the future are handled by these separate modules.
- Codec Translator API - loads codec modules to support various audio encoding and decoding formats such as Global System for Mobile communication (GSM), Mu-Law, A-law, and even MP3 (MPEG-1 Audio Layer-3).
- File Format API - handles the reading and writing of various file formats for the storage of data in the filesystem.
Using these APIs Asterisk achieves a complete abstraction between its core functions as a PBX server system and the varied technologies existing (or in development) in the telephony arena. The modular form is what allows Asterisk to seamlessly integrate both currently implemented telephony switching hardware and the growing Packet Voice technologies emerging today. The ability to load codec modules allows Asterisk to support both the extremely compact codecs necessary for Packet Voice over slow connections such as a telephone modem while still providing high audio quality over less constricted connections.
This was first published in March 2006