This manual, which is part of a series on agricultural and industrial machinery, deals with electrical systems. Special attention is paid to electricity as it is commonly used on mobile machines. The following topics are covered in the individual chapters: electricity and how it works (current, voltage, and resistance; types of circuits; conductors; semiconductors; magnetism; electromagnetism; electromagnetic induction; capacitors); test equipment and tools; storage batteries; charging circuits; starting circuits; ignition circuits; electronic ignition systems (principle of operation, self-integrated electronic ignition); lighting and accessory circuits (lighting circuits, wiring harnesses, electromagnetic clutches, gauges, meters, horns and buzzers, relays, solenoids, switches, electric motors, cigarette lighters, flame rods, transformers, glow plugs); connectors (current flow in connectors, common types of connectors, stripping and crimping, soldering and bolt cutting); monitors and controllers (agricultural and industrial applications, principles of operation, planters and seeders, round balers, forage harvesters, tractors, motor graders, scrapers); general maintenance (storage batteries, direct and alternating current charging circuits, and starting and ignition circuits), and diagnosis and testing of electrical systems (testing and troubleshooting). Emphasis is on the theory of operation, diagnosis, and repair. Concluding each chapter is a set of self-test questions. A list of definitions and answers to the questions are also provided. (MN)