Auditable security for cargo containers and other repositories

[0048] A preferred embodiment of the present invention provides a system that comprises a small low cost radio frequency (RF) tag as shown in FIGS. 1-5, that contains its own memory, a light sensor (e.g. a photodetector), an optional display and optional light emitting diodes.

[0049] As shown in FIG. 4, these tags may be placed directly on the side of the box of shipped items (e.g. autoparts) or pallet and will continuously record data including the time and light levels within a cargo container or other repository, and write this log to the internal memory of the tag. In addition, the tags may be interrogated by a radiofrequency transmitter contained in the warehouse of FIG. 6 or the truck of FIG. 7.

[0050] This radiofrequency system may be based on low-frequency (e.g. 300 khz) induction and may require large (e.g. 5′ to 50′ radius) loop field antennas placed in the ceiling or the floor of the truck. These loop antennas may also be used to segregate different regions of the truck or o