is to provide an overall view of telecommunications networks to newcomers to the telecommunications business. This kind of general knowledge is useful to the users of telecommunications services, the personnel of operators, and the employees of telecommunications system manufacturers. The professionals working with these complicated technologies very often have extensive knowledge of one very narrow section of telecommuni- cations, but are not familiar with the hundreds of terms and abbreviations that are used in other telecommunication areas by individuals with whom they need to interact. One purpose of this book is to provide content to some of the most common terms and abbreviations used in different areas of telecommunications. When I was working as a development department manager at Nokia, I noticed that relatively few books are available that provide a good intro- duction to data, fixed, and mobile networks. This kind of overview is valu- able for people entering a technology area in which all of these technologies are emerging. Most of the books on the market explain telecommunica- tions from only one point of view even though there is no longer any distinct separation of the networks that provide data, speech, and mobile services. Everyone working in the modern business environment, such as the development engineers, testing personnel, and sales managers, must have a common language if they are to work together efficiently, but not many books supply that common language because they do not provide an over- view of telecommunications as a whole. The material included in this book is used in the Telecommunica- tions Networks course for students of information technologies at the Espoo-Vantaa Institute of Technology in Finland. The goal of this course is to give students a basic understanding of the structure and operation of a global telecommunications network. This course provides an overview of telecommunications; the provision of a deeper understanding about each subject, such as the spectral analysis o