9. A system, comprising: a buffer to store samples representing an input audio signal, a speech feature extractor having an input for samples from the buffer, a speech vocabulary storing data representing a predetermined set of speech elements, and a controller comprising a decision circuit to generate a wake up signal in response to a match between speech features output by the extractor and the stored speech elements, wherein the controller is configured to output a wake up signal indicating the match and to output samples received subsequent to the samples stored in the buffer corresponding to the match.
21. The system of claim 9 , further comprising: a microphone to capture the input audio signal, a preamplifier coupled to the microphone, and an analog to digital converter coupled to the preamplifier having an output in communication with the buffer.