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!