Screen magnification results when special software enlarges a selected portion of the presentation to fill the entire screen. This software will enlarge text, graphics, and movies. Speech output combines a speech synthesizer and screen review software. This software reads text displayed on the computer screen and sends it to the synthesizer in an intelligent fashion. The students can hear individual characters, lines, words, sentences, or paragraphs, as well as punctuation.
Screen reading software also allows students to explore and navigate the text on screen.
Braille output combines screen review software with a dynamic braille display. That is, the software converts text on the screen into braille characters which are produced almost as quickly as the printed characters on the screen. Since only approximately ten percent of the people who are legally blind know and use braille, it cannot be used as the only way to make information accessible. Therefore, use of a dynamic braille display is an important and effective option. Although there are a number of assistive technologies available in each of the above categories, the effectiveness of these assistive technologies in providing access to an electronic textbook is dependent upon the design of the electronic textbook.