1. In a speech recognition system, a subsystem for spotting pre-specified words, comprising: a sub-word model analyzer using context independent phoneme models and having an input connected to a source of continuous speech; a full-word model analyzer using triphone based models which may coincide with the context independent phoneme models, the full-word model analyzer [and]having an input connected to said source of continuous speech; said sub-word model analyzer having a first threshold output signal indicative of the presence of one or more said phoneme models; said full-word model analyzer having a second threshold indicative of the probability of the presence of a pre-specified word, represented by a triphone based model; and a pre-specified word detecting means having an input coupled to said sub-word model analyzer, for receiving said first threshold output, and coupled to said full-word model analyzer, for receiving said second threshold, and in response thereto, identifying a pre-specified word to be spotted, provided the probability of the presence of the pre-specified word, represented as a triphone model is greater than the probability of the presence of the phoneme model.