Is it possible to program a telephony application with Java Sound?
It is possible. We cannot provide all concepts of digital audio in this FAQ. There are many good books on this subject. I recommend “the computer music tutorial” from Curtis Roads, from MIT press. For simple examples how to do streaming audio with Java Sound, see the Java Sound Resources: Examples. For streaming audio (and possibly video), have a look at Java Media Framework (JMF). It provides a high-level API with streaming protocols and codecs. See also next question.