Explaining applications for a wide range of technicians, this reference guide deals with an area of practice which many students and technicians find particularly challenging. Fully updated in line with IEE Wiring Regulations, it covers the intepretation of circuit diagrams, wiring systems, and the principles and practice of testing and fault diagnosis. Applications focused on include heating systems and intruder alarms. This third edition contains additional sections on shock risk, safe isolation, testing and electrical theory. It is aimed at installation and plumbing contractors, heating engineers, and anyone who needs to be able to trace faults in circuits, whether they be domestic, commercial or industrial systems.