Recognizing touch tones

[Bob Bell]

    Someone has approached me about writing some software that would
basically provide a phone menu.  It would recognize touch tones (phone
button presses), gather information, provide voice prompts, and take
action based upon the information entered.  Any idea what it would take
to accomplish this?  I'm pretty sure I could record WAVs/MP3s/etc for
the voice prompts and such, but the biggest question for me is around
the use of the phone.  Specifically:
    1) How do I respond to incoming calls?
    2) How do I get an audio file to play into the telephone?
    3) How do I recognize touch tones as input?

    Obviously, I'm asking because I would expect to use Linux as the OS
on which I develop a solution.  Does anyone know how to accomplish these
things?  Perhaps there's an Open Source package that has a number of
these features?

-- 
Bob Bell <bobbell at zk3.dec.com>
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