What is Access Switches

Many individuals with speech and motor disorders face problems in expressing themselves in an easy and intelligible way. An array of Augmentative and Alternative Communication (AAC) devices and techniques is used to alleviate their problems. One of the commonly used computer based AAC systems is the scanning keyboards. A scanning keyboard refers to an on-screen keyboard operated with a scanning input method. There are many ways to place alpha-numeric characters on the keyboard interface. Therefore, it is necessary to compare alternative layouts to determine the best one in terms of user performance. Usually, layouts are compared by testing prototypes with physically disabled users. This approach is problematic since it is difficult to get physically disabled users or collect data from those users. An alternative approach is to use models to compute user performance, which can serve as the basis of layout comparison as well as automatic design space exploration. Several of these models and design space exploration algorithms are reported in the literature. A review of these works is presented in this chapter. The chapter is concluded with a discussion on the limitations of the existing works and the issues that can be taken up for further research.