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Chapter 7 Telecommunications, the Internet, and Wireless Technology 311

FIGURE 7.15 HOW RFID WORKS

RFID uses low-powered radio transmitters to read data stored in a tag at distances ranging from 1 inch to 100 feet.
The reader captures the data from the tag and sends them over a network to a host computer for processing.

processing. Unlike bar codes, RFID tags do not need line-of-sight contact to be
read.
The RFID tag is electronically programmed with information that can
uniquely identify an item plus other information about the item, such as
its location, where and when it was made, or its status during production.
Embedded in the tag is a microchip for storing the data. The rest of the tag is an
antenna that transmits data to the reader.
The reader unit consists of an antenna and radio transmitter with a decoding
capability attached to a stationary or handheld device. The reader emits radio
waves in ranges anywhere from 1 inch to 100 feet, depending on its power
output, the radio frequency employed, and surrounding environmental
conditions. When an RFID tag comes within the range of the reader, the tag
is activated and starts sending data. The reader captures these data, decodes
them, and sends them back over a wired or wireless network to a host computer
for further processing (see Figure 7.15). Both RFID tags and antennas come in
a variety of shapes and sizes.
Active RFID tags are powered by an internal battery and typically enable
data to be rewritten and modified. Active tags can transmit for hundreds of feet
but may cost several dollars per tag. Automated toll-collection systems such as
New York’s E-ZPass use active RFID tags.
Passive RFID tags do not have their own power source and obtain their
operating power from the radio frequency energy transmitted by the RFID
reader. They are smaller, lighter, and less expensive than active tags, but only
have a range of several feet.
In inventory control and supply chain management, RFID systems capture
and manage more detailed information about items in warehouses or in
production than bar coding systems. If a large number of items are shipped
together, RFID systems track each pallet, lot, or even unit item in the shipment.
This technology may help companies such as Walmart improve receiving and
storage operations by improving their ability to “see” exactly what stock is
stored in warehouses or on retail store shelves. Continental Tires, described

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