This is a book discussing the present state of the art of avionic systems in a manner intelligible to both the student and the technician. Avionics was a major factor in preserving the world from Nazi domination in the 1940s. It was only in 1935 that Dr Watson Watt's team carried out the famous experiment at the BBC's Daventry transmitter and received a signal reflected back from a Heyford bomber approaching Daventry. The 50 years since this event have seen scientists and engineers at research centres and manufacturer's works combine computer technology with developments in this field to produce systems of unbelievable capability and reliability.