A security system for use in secure areas, buildings, hotels, automobiles and so forth. Each lock mechanism is controlled by a decoding circuit having a changeable binary memory. A basic key has two decodable information fields: a key field and an authorization field. When a key field is sensed by the...http://www.google.com/patents/USRE29259?utm_source=gb-gplus-sharePatent USRE29259 - Self re-keying security device
