 to help you learn, and it offers the Telecom Essentials Learning Center (www. telecomessentials.com/learningcenter) to help you keep learning. The Telecom Essentials Learning Center offers a number of helpful resources to reinforce your telecommunications knowledge: Online quizzes- The online quizzes allow you to test your knowledge after reading each chapter. The quizzes are designed to reinforce what you have learned and assess those areas where you might wish to review the chapter. Online telecommunications glossary-The telecommunications vocabu- lary seems to grow daily. You can use the online glossary to search thou- sands of terms to find definitions quickly. Links to thousands of related Web sites-Each chapter is supported with links to recommended books, recommended magazines, and a comprehen- sive list of key sites to visit. This portal includes thousands of links to important destinations in the world of telecom. The Telecom Essentials Learning Center will help you to keep learning long after you have mastered the essentials of telecommunications. As a LIDO student, you can also enjoy full access to Telecom WebCentral (www.telecomwebcentral.com). At Telecom WebCentral, you will have at your fin- gertips up-to-the-moment information on the latest applications and financial and legal news, as well as connections to telecom career groups and newsgroups. Whether in seminar, book, or e-learning format, LIDO explains telecommuni- cations technologies very clearly and in an entertaining and interesting fashion to a very diverse professional and academic audience. LIDO seminars are offered worldwide, and the perspectives you gain by reading this book, attending LIDO seminars, or participating in e-learning programs are not U.S.-centric. They pro- vide knowledge and understanding of telecommunications environments on a glo- bal basis. Acknowledgments There are many gratifying moments in the writing and publishing of a book, but one of my favorites is the opportunity to acknowledge the colleagues and friends who