In this article, we describe an automatic system for train timetable information over the
telephone that provides accurate connections between 1200 German cities. The caller can
talk to it in unrestricted, natural, and fluent speech, very much like he or she would
communicate with a human operator, and is not given any instructions in advance. The
system's four main components, speech recognition, speech understanding, dialogue
control, and speech output, are separated into independent modules that are executed …