We describe a new real-time isolated word recognizer with improved user interface. The recognizer is designed for an Extension Number Guidance System which looks up and announces an extension number by telephone dialogue with users. To deal with telephone quality speech input which include noise and distortion during transmission over the telephone network, we developed feature extraction and a word detection algorithm. These techniques use wide band-pass filter outputs which are generally

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... yed to decide whether speech is voiced or unvoiced. To achieve a friendly interface, the system can accept user input at any time by using an echo canceler and the new word detection algorithm. Finally, the recognizer is evaluated using a large telephone voice database consisting of more than 500 speakers.