| 摘要 |
A tracking device obtains container position information, which is communicated wirelessly to a remote site. It is determined if the container is in proximity to an aircraft by detection of electromagnetic fields, and if so, the communication is disabled. Re-enabling of the communication is allowed if simultaneously no electromagnetic fields are detected and the tracking device is able to determine a container position. Re-enabling is also allowed if the lack of characteristic electromagnetic fields has lasted for a time period exceeding a predetermined value. This predetermined value is preferably larger than a maximum flight time from a globally most remote flight position. Alternatively, the predetermined value is larger than a maximum flight time on battery backup. The positioning information is preferably performed using GPS positioning. The detection comprises detection of electromagnetic field frequencies in the range of 400 Hz.
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