47. A speech recognition circuit according to claim 46 , wherein each lexical memory stores lexical data as at least one lexical tree data structure, each lexical tree data structure comprises a model of words having common prefix components, and an initial component of each lexical tree data structure is unique.
57. A speech recognition circuit according to claim 47 , wherein said control processor passes a lexical tree identifier to a said processor, said processor reads lexical data for the identified lexical tree from a corresponding said lexical memory and processes said speech parameters using said read lexical data.