RFID for Freight Transportation Vulnerability, Security, and Productivity ...

From Electronic Cargo Seals: Context, Technologies, And Marketplace, Michael Wolfe, North River Consulting Group, writes ...

... "There are four clusters of electronic seals, representing four methods of communicating between the seal and its 'reader:' radio frequency identification (RFID), infrared, direct contact, and very long range cellular or satellite. All but the simplest solutions are capable of reporting sensor information and data that goes beyond seal status and ID.
RFID Seals RFID technologies are most common among electronic seals. Fundamentally, they marry RFID transponders or their components with manual seal components. There are two main types of RFID tags and seals, passive and active. Passive seals do not initiate transmissions--they respond when activated by the energy in the signal from a reader. Interrogated by a reader, a passive seal can identify itself by reporting its 'license plate' number, analogous to a standard bar code. The tag can also perform processes, such as testing the integrity of a seal. The beauty of a battery-free passive seal is that it can be a simple, inexpensive, and disposable device. Although not a formal term, it is useful to think of such devices as 'pure passive'--a term that describes what most practitioners have in mind when they discuss passive RFID electronic seals." ...