Importance

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Abstract

A method and apparatus is provided by the invention whereby a base station communicates with and determines the position of multiple remote devices on a two-dimensional surface. In one embodiment the base station employs a single channel radio transmitter, an infrared detector, and an infrared projecting apparatus. The radio transmitter sends a continuous stream of addressed and time-multiplexed commands to the multiple remote devices. The multiple remote devices receive commands and time synchronization from the radio signal. The projecting apparatus is located above the two-dimensional surface and projects an alternating pair of orthogonal, sweeping, infrared, line-shaped, illumination areas upon it with deterministic timing. Each remote device detects the passage of the sweeping infrared line-shaped illumination areas over it. The measured timing is used to derive the two dimensional position aboard the remote device which is then communicated back to the base station by an infrared data link.

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First Claim