This book is about teletext: a “broadcast service using several otherwise unused scanning lines (vertical blanking intervals) between frames of TV pictures to transmit information from a central data base to receiving television sets”. To the contributors to this book and possibly to many readers, this technical definition will feel out of place as it obscures the rich history of a formidable if forgotten medium. Nevertheless, it is the basic technology of teletext that sets it apart from other media and that, in part, has been the basis for much of what did and did not happen to teletext in terms of policy, institutional setting, content, users and scholarly interest. Many contributions in this book will provide similar definitions, but mostly as a stepping-stone to explore all that has so far been left unsaid by this technical description. It is this gap in our knowledge of teletext in Europe that this book aims to fill.