D is an extension of the common barcode and, while the two share some application overlap, RFID is much more than a barcode. RFID Functionality A typical RFID system is a remarkably simple collection of technology components. It comprises a collection of transponder tags, which form the heart of the system; a reader, which energizes the tags, collects information from them, and delivers the information to backroom Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Chapter 6 Figure 6-12 transponder analysis applications; and the application set that analyzes the data pro- vided by the transponder tags to the reader. This application set is criti- cally important, because RFID systems, by their very design, generate enormous amounts of data that must be analyzed and acted upon if the system is to have value. Each transponder, an example of which is shown in Figure 6-12, has a unique "serial number" (a card ID, or CID) that identifies the tag and therefore whatever it is attached to-a pallet of products, an identifica- tion card, or a beef cow in a herd. When the tag is within the operational range of a reader, the reader's magnetic field energizes the tag, causing it to go through a series of functions that culminate in the transmission of whatever piece of data is stored in the tag's memory. This information is programmable and might contain detailed product information, prod- uct perishability data, routing information, a sheep's bloodline, and so on. For the most part, the tags are passive, meaning that they have no bat- tery but are, in fact, powered inductively by the RF signal emitted by the reader. These tags necessarily have a relatively short read range-as much as a foot, no more-but active tags, which do have internal power, can broadcast up to 20 feet under the right conditions. Passive tags are often used in applic