Contents Introduction Starving for standards Secrets and trials Chipping the chains RFID a real asset Future potential Executive summary

There are two basic types of tag. Active tags require a power source (usually a battery) and are therefore relatively bulky and expensive. The eTag used on tollways is a well-known example. The main benefit is that they have a greater range.

Passive tags do not require a battery. Just as old-fashioned crystal radios worked from the energy of the broadcast signal, the tag is powered by the energy radiated by a reader. The "microchip" used to identify pets is a passive RFID tag.

For commercial or industrial uses, the tags are often mounted on a label, and the chip can be programmed with a unique identity number at the same time as the label is printed. For backwards compatibility, the label can also carry a barcode as well as human-readable information.

Reading a tag is not foolproof. "There are a lot of physical constraints you have to consider," says Trevor Barrows, solutions director at SSA Global Pacific, including the presence of water or metal which reduces range, and the possibility that two tags may be in contact (although Sydney-based Magellan Technology has developed "stack tags" that can still be read even when many tags are in very close proximity).