3.1.1 Assistive technologies for physical disabilities and motor impairments
Mouse Alternatives and Replacements
Trackballs, joysticks and various forms of tablets are frequently easier to control than a mouse. The mouse pointer may also be controlled using head movements, which are tracked using infrared or ultrasound technology. Buttons on many alternative pointing devices can be programmed to perform a double click or to lock down the mouse button for a drag. Mouse buttons can be replaced with switches (e.g., puff-sip switches, foot pedal switches, etc.) or with software that performs the mouse click, double click, and drag by dwelling on a target for a predetermined time and then moving the mouse cursor in one of four directions.
The mouse pointer can be controlled using keys on the numeric keypad, or keys on an on-screen keyboard. Mouse emulators exist for single-switch users and users of voice recognition systems. These emulators employ a variety of strategies to quickly zero-in on the target.
Figure 3.1 An arthritic hand trying to use a standard mouse
Keyboard Modifications and Alternatives
Free software or operating-system modifications allow changes to be made to keyboard responses by slowing response time, eliminating or slowing key repeat rates and holding keys used in multiple key depressions when selected sequentially. Standard keyboards are also available with on-board memory for text or command macros. Mainstream alternatives include keyboards that are smaller, more ergonomically shaped, provide more efficient keyboard layouts (e.g., DVORAK or QWERTY) and have built-in trackballs or other mouse alternatives.
Specialized keyboards have been developed to accommodate a variety of individual needs. Miniaturized keyboards accommodate those with limited range of movement or strength. These may have mouse emulation as a built-in feature. Enlarged keyboards are more suited to person with poor motor control but adequate range of movement. Programmable keyboards allow for customization of the keyboard layout (key content, key size), with individualized overlays depicting the key contents for the user. Keys may also be programmed with mouse emulation functions.
Numerous on-screen keyboard software programs allow the user to select keystrokes (e.g., letters, words, commands, phrases) using a mouse or mouse emulation.
Switch input devices can be used by persons who are unable to use a keyboard or mouse but who have good control of some other muscle groups. Switches can be used to emulate keyboard and mouse functions. Single, dual or three-switch input of Morse code, for example, can be translated by a hardware and/or software interface into keyboard and mouse inputs to the computer.
Figure 3.2 A single switch mounted on a wheelchair 67
Voice recognition of commands or text input is available with some operating systems. Continuous speech voice recognition software that provides text input, mouse control and software application control, including optional levels of vocabulary and macros for various professions or specialty groups, is also available. Although voice models in the system allow the recognition of words without explicit training, each user has their own voice model file, which should be adjusted to allow optimal recognition. Proper maintenance of the voice model requires vigilance to errors made by the user and the system and proper correction of the errors. Most voice dictation systems have very large dictionaries, but the user must add proper names and specialized vocabulary. Several dictation systems rely on mouse controls to navigate the desktop and dictation functions.
Augmentative and Alternative Communication
Many people with a severe physical disability may also have speech impairments. Augmentative and alternative communication (AAC) is a way of communicating, not only for those with speech impairment but also for those with difficulty in comprehending spoken or written language.68 AAC strategies vary from the use of symbols or gestures to the use of AAC devices such as (a) text-to-speech generating (Fig 3.3) devices and (b) speech generating (Fig 3.4) devices. While AAC strategies and devices are not an integral part of enabling computer access, they are essential in enabling two-way communication in an inclusive education, job-skill training or work environment with teachers, trainers, fellow students and work colleagues.
Fig 3.3 Keyboard text-to-speech generating device69
Fig 3.4 Speech generating device
The following video shows how Ellen, an AT user, uses switches and an AAC device to communicate, access a computer and control her surroundings at home and at college.
67Source: http://en.wikipedia.org/wiki/File:Access_device.JPG Debbie L OU
International Society for Augmentative and Alternative Communications (ISAAC) http://www.isaac-online.org/en/publications/index.html