A system for supervision and control of objects or persons within a limited area, such as a building, comprising a plurality of electronic identification chips for placing on respective objects/persons to be supervised/controlled, each chip having stored therein a special ID code and being provided with...http://www.google.com.hk/patents/US6433689?utm_source=gb-gplus-share專利 US6433689 - System for supervision and control of objects or persons
