Visually impaired persons may use braille terminals in order to understand what text is being displayed on a computer monitor. Braille terminals are machines that convert the text on a screen to braille. The braille displayed on the terminal is refreshable for repeated use.
Braille terminals are generally expensive machines but alternative aids are available. Speaking software, or speech synthesizers, can be employed to read the text aloud to the visually impaired user. Touch monitors are also available to assist the user in typing. In fact, some systems combine the functions of a braille terminal and a regular keyboard.
Braille terminals are generally very basic looking machines that display anywhere from 20 to 80 cells which can be refreshed by being pushed up or down. Typically, a cell, which conveys one character, is represented by six raised dots or bumps — two across by three down. Braille terminals, however, employ eight dot cells — two across by four down. The extra two dots are typically used to display the cursor's position, but in some European countries they are used as part of the alternative eight dot braille system. A braille display also has buttons that can be used to move the computer's mouse cursor or that can be set to perform user-specified functions.
In addition, some braille terminals are designed to display alerts when a radio emergency signal is transmitted or when a telephone call is made to the user's telephone. These signals are detected by an FM transceiver, which transmits the information to a vibration motor. The vibrator then makes the braille terminal vibrate in one of two patterns so that the user will know whether an emergency broadcast or telephone call is being made. If it is an emergency broadcast, the braille terminal can also turn on the connected computer and display the appropriate emergency information, which is then converted into braille and displayed on the braille terminal.
Braille terminals can be used with a variety of operating systems, including Windows, Macintosh, and Linux. These operating systems include a piece of software called a screen reader which pulls text content from the current screen display and converts it into braille. The braille characters are then transmitted to the braille terminal. The software might also describe graphic content and send the descriptions to the braille terminal as braille characters.