Linux Accessibility HOWTO
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3. Visual Impairments

There are two categories of visual impairments. Individuals who are partially sighted (for example, blurred vision, near and far-sightedness, color blindness) and those who are totally blind. Assistive technologies are available for the Linux operating system for visually impaired users, and many of the software packages are free.

3.1. Technologies for the Visually Impaired

The following is a list of assistive technologies for visually impaired users:

3.1.1. Screen Readers

Screen readers are software applications that are installed on the computer to provide translation of the information on the computer screen to an audio output format. The translation is passed to the speech synthesizer and the words are spoken out loud. Currently, fully functional screen readers are only available for Linux in console mode. This section describes some of the most common screen readers.

3.1.2. Speech Synthesizers

Speech synthesizers can be a hardware device or a text to speech (TTS) software application that creates the sounds necessary to provide speech output. Hardware synthesizers are available for the Linux operating system; however, they can be very expensive and must be compatible with the screen reader application in order to function properly. The alternative is to download and install a software synthesizer such as IBM's ViaVoice or Festival and configure the application to a compatible screen reader, such as Emacspeak.

3.1.2.1. Hardware Speech Synthesizers

A hardware speech synthesizer is a device that is connected to the computer's serial or parallel port and translates the text to a spoken output. Normally there are Braille labels on all controls to indicate the off and on position, and volume control. Hardware synthesizers also have the ability to speak in different tones that can be setup to indicate various parts of a document or text. Some models will provide a connection for headphones. The following is a list of speech synthesizers that are supported on the Linux operating system and can be used with Emacspeak:

3.1.2.2. Software Speech Synthesizers

A software speech synthesizer is an application that translates the text on the screen to speech output and provides speech synthesis, so that the screen reader application can read information out loud to the user.

3.1.3. Screen Magnifiers

Screen magnifiers enable users that are partially sighted to view selected areas of the screen in a manner similar to using a magnifying glass.

3.1.4. Adjusting the Screen's Resolution

The X Windows server can be setup with different screen resolutions. The ability to adjust the screen's resolution allows a partially sighted user to magnify the screen with a single key sequence. The steps to set up your system are as follows:

  1. Changed directories, type cd /etc

  2. Using a text editor, open the XF86Config file

  3. Locate the line beginning with Modes and change it to 

    Modes "1280x1024" "1024x768" "800x600" "640x480" "320x240"
    Note: The settings may vary based your monitor's highest resolution mode.

  4. Save the file and exit.

To enlarge the text on the screen type Ctrl+Alt+keypad-plus and to make the text smaller type Ctrl+Alt+keypad-minus

3.1.5. Braille Devices

Braille terminals are normally used by individuals who are totally blind and may be hearing impaired as well. A Braille display uses a series of pins to form Braille symbols that are continuously updated as the users changes focus. A Braille embosser is a hardware device for printing a hard copy of a text document in Braille. Braille translation software is required to translate the on-screen text to a Braille format.

3.1.5.1. Braille Hardware Devices

The following Braille devices have been listed on the hardware compatibility list of one or more of the following Braille translation applications:

3.1.5.2. Braille Translation Software

The following Braille translation applications are available for download:

3.1.6. Cursors for X Windows

Changing the shape and size of the mouse cursor can help users who have a problem following or seeing the cursor. The X Big Cursor mini HOWTO explains how to configure enlarged mouse cursors with the X Windows system. This HOWTO is available at: http://www.icewalk.com/doclib/howtos/mini/X-Big-Cursor.html .

There are also a large select of cursors that can be downloaded at: http://themes.tucows.com/cursors.html .

3.1.7. Audio

Audio can be very useful to users who are visually impaired. In most X Windows desktop environments audio alerts and sound events can be setup within the desktop control center by enabling sound and verifying that the option to show sound is activated. You will need to check the desktop users manual for setup and configuration of sound events.

Locktones is an excellent application for providing toggle keys that sound an audio alert to warn the user that a keystroke has created a locking state such as Cap Locks, or Num Locks. The application can be downloaded at: http://leb.net/pub/blinux/ .

Linux can also be configured to beep at the login prompt so the user knows when to type in the password. A configuration utility can be downloaded and installed that can provide this function at: http://leb.net/pub/blinux/bootmeup/ .

3.1.8. Additional Resources
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