The purpose of this book lies outside the usual framework of studies devoted to technology in a given branch of industry. Its main objective is to show how, in only two decades, the highly specialized telephone switching industry was completely transformed and how it revolutionized its manufacturing processes and its products, a phenomenon largely unknown to the public. The change was so drastic that it has been compared to the metamorphosis of the insect which progresses from the caterpillar phase to that of the butterfly.The second aim of the book is to show how the change occurred within the context of the major electronic revolution of recent decades, following the inventions of the transistor and integrated circuits.