I've got a decade or so designing telco interfaces and modems, if that helps.

It sounds though, like a winmodem (gag-choke) might be best for this app.
Mostly because of the need to handle audio in.

Other than that, Dialogic makes cards that would do this, perhaps they 
might donate old obsolete versions?

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist