This new textbook, written in conjunction with C&G, has been designed to be a complete companion for learners taking this course, giving them all the information they need at this level in a step-by-step, easily accessible way. Covering all the core units, these resources are a comprehensive reference guide for all learners at this level. Unit 309 includes: Unit 309 – Level 3: Understanding the electrical principles associated with the design, building, installation and maintenance of electrical equipment and systems About the Author The IET has provided specialist writers for all areas in the specification – Howard Carey, Trevor Pickard, Paul Harris, Andrew Hay-Ellis and Paul Cook. All are very experienced lecturers, tutors and practitioners.