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This paper describes a novel light-sensor-based information transmission system for indoor positioning and navigation with particular benefits for mobile and wearable computers. It can seamlessly extend outdoor GPS tracking to the indoor environment. In a novel manner, fluorescent light is used as the medium to transmit information, which is encoded by using a pulse-frequency modulation technique. The user receives the encoded light information through a photoreceiver. The information is passed into the wearable or mobile computer after the data are decoded. This information allows positioning information to be given to indoor mobile and wearable computers. We design an economical transmitter circuit by adding a few components to a commercial electronic ballast circuit for fluorescent lamps with a price of less than 10 USD. The proposed system can be used in indoor guidance and navigation applications. Exemplary applications are included in the paper, with experimented results detailed.