This text provides an essential parallel treatment of continuous time and discrete time methods in signals and signal processing modelling and simulation, digital signal processing, filter theory and digital filters. Every topic is illustrated by applications and examples from both the students' background in electrical circuits, and from practical unrelated fields, such as: economics, physics, biomedical engineering, chemistry and heat transfer. The authors take into consideration the fact that students' previous mathematical studies may be too limited for many of the topics considered and, therefore, all essential mathematical details are included. Where a given development might involve extensive mathematical demands, this is indicated by use of a symbol at the section title. An appendix on matrix theory is included as support material to state equation development. This book should be of interest to degree and diploma students on courses in signals and systems; a knowledge of circuit theory and mathematics through differential equations is a prerequisite.