An acoustic echo canceler and a side-tone echo canceler provided in a hands-free telephone suppress an acoustic echo and a side-tone echo respectively with few error by providing automatic gain controllers and/or limiters in the hands-free telephone so that the acoustic echo canceler and the side-tone...http://www.google.com/patents/US5384843?utm_source=gb-gplus-sharePatent US5384843 - Hands-free telephone set
