RFID Freight Transportation Security ...

FHWA Freight Management and Operations - Technology to Enhance Freight Transportation Security and Productivity - A-2. Event-Driven Tools

... "Electronic seals tend to combine physical seals and RFID components. Most of the electronics include passive or active RFID technologies. Passive seals are short range, low cost, and disposable. They have no inherent electric power, such as a battery. The RFID reader or interrogator provides energy when it illuminates or scans the seal. The passive seal uses the absorbed energy to reflect its information back to the reader. The lack of on-board power limits the functionality. For example, since passive seals cannot provide continuous power to measure the condition of the seal cable, they cannot detect and record tampering at the time of the event - they simply report whether they are intact or not when interrogated by a reader. Active seals are more sophisticated, have higher initial costs, and until prices drop significantly demand reuse. Active seals carry batteries and the power permits longer range and greater functionality. To extend the previous example, they can detect tampering when it occurs and add it to a time log of events. If equipped or interfaced with GPS, an active seal can also log the location. Further, some seals can provide live mayday tampering reports as the events happen, mostly within specially equipped terminals. " ...