Completely revised and updated to reflect changes in the field, the new edition of this popular text presents a model of a disabled human operator using various assistive technologies. Also included: an overview and historical perspective of the field, special disabilities and the use of assistive technologies, how to derive and measure standards of performance, proper positioning when using assistive devices, and more. New to this edition: a comprehensive glossary, new appendices, including a list of resources and a list of product manufacturers, additional case studies, new illustrations and photographs, and more!