HOW DOES IT WORK?

 

The interrogator device sends out a signal looking for nearby tags. When a tag receives that signal, it transmits whatever information it has been programmed to transmit. Hand-held interrogators are used for things like inventory control—scanning items in and out of a warehouse, for instance. Stationary scanners exist for applications in which the tags themselves are highly mobile, like toll booths and passport control. Any interrogator can be used to track location—if you know where the interrogator is, you know where any tags it scans are.

There are three ways of powering the transmission sent by an RFID tag. Passive tags don’t carry their own batteries, making them small and inexpensive. They borrow the power to send their data payload from incoming signals—meaning that when an interrogator sends a signal to the tag, leftover energy from the incoming signal powers the transmission. Range is limited by the amount of power put into the tag, but it can be more than sixty feet. Because they’re cheap, passive tags are most common in consumer goods. They’re also the least secure. It takes energy to encrypt information—low power means weak or nonexistent encryption.

Active RFID tags include batteries. They’re bigger and more expensive than their passive cousins, capable of broadcasting farther, but also capable of stronger security. They actively try to get the attention of interrogators. When they find one, they can transmit more than 200 yards. If you’ve got one of these on you, that’s a circle a fifth of a mile across, in which anyone could be receiving information and getting a rough idea of where you are. With multiple interrogators or the GPS unit that some active tags carry, your exact location becomes public knowledge.

The third kind of RFID tag is a battery-assisted passive tag. These are comparable in size to active tags, but they’re less enthusiastic. They conserve their energy until they receive a query from an interrogator, then they broadcast their payload with a range similar to active tags.

By the time you read this, passive tags could be as cheap as one cent. Spending a single cent to include a tag on every product could translate to thousands or hundreds of thousands of dollars in assets and supply chain management savings for retailers and manufacturers. In the near future, everything you buy, from new cars to fun-size Kit Kats, will include an RFID tag.