This book not only attempts to describe the aspects of telecommunications that are necessary for examinations but also to describe the effects of telecommunications in our society in the past and today. It is hoped that the relevance and importance of this subject to everyday life will be apparent. The book is written in such a way as to encourage a variety of approaches. Each chapter is similar in layout. There are a series of objectives on what may be learnt in the chapter. There follows four sections with questions at the end of them. At the end there is a summary followed by further questions including ones taken from examination papers. In many of the chapters there are investigations. These are designed to further the understanding of the topics, and to failiarize students with science apparatus and scientific investigation. Not every part of the syllabus is covered, but there is a list of reference books which, it is hoped, will help to fill the gaps.