disabled in both places during the winter than during the summer. Thus, the natural environment, including topography and climate, affect whether or to what degree a functional limitation will be disabling.
The physical environment is a complex interaction of built-in objects (Corcoran and Gitlin, 1997). Built objects are created and constructed by humans and vary widely in terms of their complexity, size, and purpose. Built objects are created for utilitarian reasons and also for an outlet for creativity. For instance, built objects such as dishwashers and computers have the potential to enhance human performance or to create barriers.
Another aspect of the built environment is assistive technology. The Technology-Related Assistance for Individuals with Disabilities Act of 1988 (Public Law 100-407), also known as the Tech Act, defines assistive technology devices as "any item, piece of equipment, or product system, whether acquired commercially off-the-shelf, modified, or customized, that is used to increase, maintain, or improve the functional capabilities of an individual with a disability." Thus, assistive technology affects the level to which a functional limitation is disabling. As an illustration, a person whose visual impairment can be corrected by corrective lenses does not technically have a disability. There are numerous other examples of how the environment affects the amount of disability associated with any functional limitation through the use of assistive technology. A person with a hearing impairment who has a TDD can make phone calls to other people who also possess such devices. If there is a relay service, in which an operator translates from TDD to voice telephone, the person who owns a TDD can call anyone. In these situations the impairment does not cause a disability. This example, however, illustrates the fact that it is the intersection of technology and social factors that can be more enabling than just the technology itself. Other examples are that a person who has a speech impairment can "speak" using a computer voice synthesizer or that people with low vision or blindness can read office memoranda or correspondence if he or she has the right computer software. These technologies do not always need to be complex: a person who uses a wheelchair and who works in an office could work effectively if the simple technology of an adjustable desk allowed the desk to be raised to allow the wheelchair to fit under the desk.
Through the passage of Public Law 100-407, the federal government affirmed the importance and benefits of assistive technology for the mil-