Importance

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Abstract

A system for determining the position of a labelled object within an environment containing a plurality of detectors sensitive to energy of a first type and located at known positions therearound, wherein the object has a transmitter for transmitting energy of the first type, and each object is labelled by means of a receiver forming part of a communication link with a remote controlling transmitter for triggering the object-mounted transmitter. The transit time between the transmitter and each detector is used to determine the straight line distances between the object and the receivers, to enable the position of the object relative to the receivers to be determined. The arrival and departure of an object into and from the environment is determined by a second communication link from a second transmitter on each object, to a remote receiver. The two communication links may be combined in a bi-directional radio communication system. Computing means is provided to associate the time information with the receivers from which the times have been obtained to generate a transit time to each receiver, and the high speed energy transmissions may be encoded so that a plurality of different transmitters, all located in the same specified environment, can be triggered in turn. Typically the slow speed signals are acoustic or ultrasonic signals and the high speed signals are electric currents, voltages, electromagnetic radiation such as IR, UV or radio signals.

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First Claim