The MIT ATIS System: February 1992 Progress Report 
 
 This paper describes the status of the MIT ATIS system as of February 1992, focusing especially on the changes made to the SUMMIT recognizer . These include context-dependent phonetic modelling , the use of a bigram language model in conjunction with a probabilistic LR parser , and refinements made to the lexicon . Together with the use of a larger training set , these modifications combined to reduce the speech recognition word and sentence error rates by a factor of 2.5 and 1.6, respectively, on the October '91 test set . The weighted error for the entire spoken language system on the same test set is 49.3%. Similar results were also obtained on the February '92 benchmark evaluation . 