RFID Wireless world - tags
RFID tagsLast updated: December 31, 2009.
How many times have you walked through a store's doors and—to your extreme embarrassment—set off the anti-theft alarm? It's surprisingly easy to do, even when you've paid for your item and had it "deactivated" at the checkout. Anti-shoplifting alarms use a technology called RFID (radio-frequency identification), but the same technology has many other uses too, from tracking pets to collecting fares from bus passengers. Let's take a closer look at this cunning new technology and find out how it works!
Photo: A typical RFID gate in a shop doorway. There's another one of these on the other side of the door. Sometimes these scanners are disguised so you can't see them, but more often they're designed to act as a very visible deterrent to shoplifters.
Radio or wireless is a way of transmitting energy through empty space—that is, instead of using a wire cable. The energy is carried by invisible waves of electricity and magnetism that vibrate through the air at the speed of light. The basic science and the practical technology of wireless communication was developed in the second half of the 19th century. During the early 20th century, "radio" came to mean audio programmes beamed through the air from giant transmitters to cumbersome electronic boxes sitting in people's homes. When inventors found a way of sending pictures, as well as audio, television was born. Today, all kinds of things work using the same wireless technology, from digital radio and television to cellphones (mobile phones), and wireless Internet.
Radio and television involve sending radio waves in one direction only: from the transmitter at the radio or TV station to the receiver (the radio or TV set) in your home. Wireless Internet and cellphones are more sophisticated because they involve two-way communication. Your cellphone, for example, contains both a radio receiver (to pick up an incoming signal from the person you're speaking to) and a radio transmitter (to send your voice back to the other person).Radar is another technology that uses radio waves. Planes and ships fitted with radar transmitters send out beams of radio waves and listen for echoes—reflected radio beams bouncing back off other planes and ships nearby. Anti-shoplifting devices are a little bit like radar: they beam radio waves out into a store in the hope of catching a stolen book or CD as it passes by. But how exactly do they work?