to large pallets or other containers via the con- venient hole in the center of the disk, and is reusable. The thin sheet tag (5) is affixed to a sticky backing and can be affixed to the inside of com- puters, library books, and other small items. 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 The cylindrical tag (6) is an interesting transponder tag. The one shown is designed for high heat and corrosive environments, often used, for example, in automobile painting lines that are subject to extremes of temperature and caustic substances. The tag can be attached to an auto- mobile body, for example, and as it passes through the line broadcasts the color that is to be applied and the chassis style so that the robotic painters apply the paint correctly. The cylinder style also comes in a ceramic form factor and is designed to be embedded in the stomach of cattle. The tag contains bloodline history, shipping information, and other data that is invaluable to veterinarians tracking disease. And because the device is ceramic, it is impervious to corrosive stomach acids. The disk (7) is similar to the larger disk described earlier; it can be attached to smaller packages and, like its larger cousin, is reusable. In fact, these devices often remain attached to their shipping containers. The key fobs shown in (8) and (9) are RFID tags designed to facilitate the purchase of fuel. The Speedpass (8) is commonly seen, and replaces the need for a credit card. The glass transponder (10) is intriguing. These devices are designed for subcutaneous use, often injected under the skin of livestock, fish, and other wildlife that veterinarians and wildlife biologists wish to track. Sturgeon are often tagged SO that aquatic biologists can track the move- ment and survival rate of the fish. Spectrum Considerations RFID systems are genera