| abstract |
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 respective transmitters and receivers for communication via ultrasound as well as audible sound, a plurality of stationary detectors which are interconnected in a network and arranged for both-way communication with the chips, and a central control unit in communication with the chips via the detectors. Each chip is continuously active in operation and is arranged to transmit its ID code at predetermined time intervals. At least one of the detectors or the control unit are being arranged to trigger an alarm unit if an incorrect code is received or an approved code is not received continuously at predetermined time intervals. |