Ulrich Karrenberg, the author of this book, studied telecommunications in Berlin from 1960. After completing his degree course he worked as an engineer for 7 years. After taking a degree course in physics and mathematics at Cologne University he started working as a teacher at the present-day Heinrich-Hertz-Berufskolleg (vocational college) in DA1/4sseldorf. For 12 years he was responsible for the full-time vocational training of students in the field of electrical engineering up to their university entry qualifications. Alongside his main position, he was a member of the curriculum board for