books.google.co.uk - Many books have been written about the many different manual and automatic systems used throughout the world. These works usually only describe the way a system works. In this publication, not only the differences in principles by which these systems function are distinguished, but also the background...http://books.google.co.uk/books/about/100_Years_of_Telephone_Switching.html?id=EaVSbjsaBfMC&utm_source=gb-gplus-share100 Years of Telephone Switching
