Patent ID: 7123159

Claim:
A position dependent information retrieval system comprising a plurality of transmitter units and at least one receiver unit, each of said plurality of transmitter units comprising; a light source; a driver for generating a drive signal for said light source such that said light source produces a light signal; and an encoder for modulating said drive signal with a predetermined signature such that said light source produces a modulated light signal, wherein said predetermined signature is unique for each of said plurality of transmitter units, and said at least one receiver unit comprising: a receiver including a photosensitive detector for detecting the modulated light signal, and a decoder for decoding the predetermined signature; a memory having stored therein a plurality of localized messages; a controller communicatively coupled to the receiver and the memory, said controller receiving the decoded predetermined signature from said receiver, and obtaining at least one of said stored localized messages in dependence on the decoded predetermined signature; and an output device coupled to the controller for outputting the obtained at least one localized message.