Internal Program Version: iaxmodem  1.3.0

IAXmodem is a software modem written in C that uses an IAX channel
(commonly provided by an Asterisk PBX system) instead of a
traditional phone line and uses a DSP library instead of DSP hardware
chipsets.

To accomplish this, then, IAXmodem interfaces an IAX library known as
libiax2 with a DSP library known as spandsp, and then IAXmodem
interfaces the DSP library with a tty device node for interfacing
with modem applications.

http://sf.net/projects/iaxmodem