Patent US 5,239,586

A voice recognition system comprises a handset and a hands-free microphone for generating an input audio signal, a high-pass filter for eliminating low frequency components from the signal from the handset or hands-free microphone, a signal level controller for adjusting the level of the high-pass signal in response to the user of either the handset or hands-free microphone, a storer for storing the speech data and a controller for controlling the storer so that a user's utterance is stored or the user's utterance is recognized by comparing the utterance to speech data already stored. The handset hook switch provides an on-hook control signal to reduce amplifier gain during hands-free microphone operation.