minimodem - software audio Bell-type or RTTY FSK modem
Copyright (C) 2011-2012 Kamal Mostafa <kamal@whence.com>
Minimodem is a command-line program which generates (or decodes) audio
modem tones at any specified baud rate, emulating an old Bell-type or
radio-teletype FSK modem. The tones can be played to (or recorded from)
the system audio (PulseAudio or ALSA) or to an audio file.
Minimodem can be used to transfer data between nearby computers using an
audio cable (or just via sound waves), or between remote computers using
radio, telephone, or another audio communications medium.