Rabu, 22 Juni 2011

RFID Tags: Passive, Active And Hybrid

By Owen Jones


All RFID tags are used to store and ultimately send data. They can best be thought of as the replacement for the bar code. However, they have significant advantages over bar codes. For instance: RFID tags can hold much more data than bar codes; they can be scanned from further away and they can in point of fact send data, not only store data.

There are three varieties of RFID tags: passive, active and hybrid. Passive RFID tags are the least expensive, because they are less complex. They need to be induced to disclose their data by taking power from an RFID reader. When the reader's radio waves hit them, they reflect back their data. This is the kind of tag used in goods in a retail outlet or on crates in a warehouse.

On the other hand, active RFID tags have a battery, a transmitter and an aerial so that they are always transmitting. These units are clearly a lot more expensive and so are used only on more expensive items like a container, a battle tank, an aircraft, on criminals ankle bands or on an animal of an endangered species.

The hybrid RFID tag is capable of transmitting, but it needs to be told to transmit; it has to be switched on by a signal. This signal could be a satellite passing over head. These hybrid RFID tags are also costly, but the battery lasts longer because they are not 'always on'. These tags have the same applications as the active tags, but are appropriate for use where it is not vital to know where something is every minute of the day: for example cattle in a field or goats on a mountain.

Passive tags can be attached permanently by sewing them into hems or putting them under skin because they do not have their own electricity source and do not wear out. This is a cause of concern to some people who worry about an invasion of their privacy or the erosion of their human rights.

Active and hybrid tags are most frequently plainly visible so that the batteries can be changed as and when required. If this is going to be unlikely to take place, as in the case of wild animals, the tag can have a biodegradable clasp which will break sometime after the probable expiry of the battery.

Some uses for RFID tags are on season tickets so that the holder can pass through the style more quickly than a customer paying by cash. It has applications in security; most of the ID badges you see pinned to shirts have RFID built into them so that security guards do not have to stop and question everybody.

They can be put into wagons that repeatedly cross frontiers so that they do not have to stop for identification. They can be put on windscreens so that, as you pass through a motorway toll post, either your credit card is billed or the charge is added to your company's monthly statement.

Hospitals use them on patients so that they do not lose anyone or mis-identify them. RFID tags are useful in our daily lives but people are worried about criminals being able to read all this information too easily as well.




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