A special telephone instrument has a cordless hand-piece and one or more base-stations. Each base-station is hard-wire-connected with the ordinary telephone utility system and may include a built-in cellular transceiver. The hand-piece, which is powered by a built-in rechargeable battery, is--within...http://www.google.co.uk/patents/US6167278?utm_source=gb-gplus-sharePatent US6167278 - Combination cordless-cellular telephone system
