| 摘要 |
An information system for communicating information from each of a plurality of separate locations to each of a plurality of mobile objects includes a beacon at each location and a beacon triggering and detecting apparatus mounted on each object. Each beacon triggering and detecting apparatus is assigned a predetermined and unique time window within a common system cycle. During the initial portion of its window, the beacon triggering and detecting apparatus transmits a trigger signal at a frequency f1, with the trigger signal as transmitted having a substantially constant amplitude and with frequency f1 being chosen so that the intensity of the trigger signal decays as the cube of radial distance from the object. If the object is within a predetermined beacon trigger range of a location, the beacon at that location detects the trigger signal and transmits a beacon signal at a frequency f2 (substantially greater than frequency f1) during the terminal portion of the window which is detected by the beacon triggering and detecting apparatus. The beacon signal contains any information that is desired to be communicated from the location to the objects, such as the identity or location of the beacon. Provision is made for synchronizing the various beacon triggering and detecting apparatus by signals at a frequency f3 (that is distinct from frequencies f1 and f2) from a base station, for disabling operation of a given beacon triggering and detecting apparatus upon the failure of that apparatus to be synchronized by the base station for a predetermined period of time, and for transferring the information that has been communicated from each location to each object to the base station for further processing and centralized information display.
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