O-TEL-an experimental reverse directory telephone service with barge-in capability

Issues of practical implementation of a telephone dialog system are discussed with the reference to the experimental O-TEL system (a telephone reverse directory service) developed at the University of Maribor. The system offers a user to call the system, utters the telephone number in order to receive information on the subscriber (name and address). Critical implementation issues are: allowing a full-duplex telephone interaction (user barge-in); design of a dialog flowchart that enables fluent and fast dialog; robust feature extraction with channel compensation; assuring a high recognition accuracy; and synchronizing the system prompt signal with the feature extraction part of a recognizer for the purposes of introducing echo cancellation as a part of feature extraction. Field trials have shown especially high rate of dialog completion and a good error recovery scheme. The capability of barge-in reduced the dialog completion time for up to 56% (especially in error recovering phase).