The aim of this revised and updated text is to provide a concise introduction to the theory of signal analysis and linear signal processing. To ensure that it is contemporary in flavour examples of cross-correlation by digital computer have been included. It is suitable for students of the second and final years of degree courses in electrical and electronic engineering and for other courses which deal with the analysis and processing of signals, records and data of all types. Students of electrical engineering will find the text relevant to courses on communications and linear systems as well as on signal theory. It will help them to fit much of their work on electric circuits and systems into a more general framework. Further problems have been provided at the end of four chapters and numerical answers to selected problems are given at the end of the book.