An externally attached handset connected between an end terminal of a mobile communication system and a data communication end terminal which handset is connected via a speaker/microphone terminal on the end terminal of the mobile communication system. The handset comprises a speaker, a microphone, a...http://www.google.com/patents/US5452474?utm_source=gb-gplus-sharePatent US5452474 - Externally attached handset of an end terminal used for mobile communication systems
