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Linux Accessibility HOWTOMichael De La RueSharon Sniderv3.1, June 21, 2002
1. IntroductionThe purpose of this HOWTO is to introduce the tools, applications, and configuration utilities that are available to Linux users who are disabled. The information provided targets groups of individuals with the following disabilities: Please send any comments, or contributions via e-mail to Sharon Snider. This document will be updated regularly with new contributions and suggestions. 1.1. Distribution PolicyThe Access-HOWTO may be distributed, at your choice, under either the terms of the GNU Public License version 2 or later or the standard Linux Documentation Project (LDP) terms. These licenses should be available from the LDP Web site: http://www.linuxdoc.org/docs.html. Please note that since the LDP terms do not allow modification (other than translation), modified versions can be assumed to be distributed under the GPL. ViaVoiceŽ is a registered trademark of International Business Machines Corporation. 2. The Linux Operating SystemThe Linux operating system has many software applications and utilities that run in the non-graphical environment. The graphical user interface (GUI), which is often referred to as X Windows, is clearly separate from the underlying non-graphical, text-only environment. One major reason that a visually impaired individual can use Linux is that network connectivity is built in to the operating system and provides full access to the Internet from the non-graphical interface. All visible text on the screen can be translated using a screen reader and speech synthesizer. Over the past few years many improvements have been made to the GUI, and many of the desktops now provide features and enhancements designed for accessibility. In the following sections you will find information on the tools, utilities, and applications that are available to assist users in configuring their desktop environment. 2.1. Assistive Technologies Available for LinuxAssistive technologies are computer hardware devices and software applications that provide individuals with impairments access to the information and applications on a computer. Although there are not many commercial applications available specifically for Linux accessibility, there are free software applications that can make the computer more accessible. Detailed information on assistive technologies that are available has been listed in this document based on the type of disability. 2.2. UsabilityLinux has the advantage over Windows that a large majority of Linux software has been developed for the console. Although many programs are now being developed for the GUI, programs continue to be written for the non-graphical, text-based environment. Linux originated as a programmer's operating system and, for the physically disabled, this means that it is easy to build and customize programs to suit an individual's needs. The windowing system used by Linux (X11) includes many programming tools that enable further modification and customization of the GUI. KDE and GNOME have included many accessibility and usability features in their latest releases and are continuing to test, upgrade, and enhance the graphical environment. The following are links to KDE and GNOME's accessibility and usability projects:
3. Visual ImpairmentsThere 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 ImpairedThe following is a list of assistive technologies for visually impaired users: 3.1.1. Screen ReadersScreen 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 SynthesizersSpeech 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 SynthesizersA 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 SynthesizersA 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 MagnifiersScreen 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 ResolutionThe 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:
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 DevicesBraille 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 DevicesThe 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 SoftwareThe following Braille translation applications are available for download:
3.1.6. Cursors for X WindowsChanging 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. AudioAudio 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
4. Hearing ImpairedFor users who have hearing impairments the audio output must be conveyed visually on the screen. Most desktops provide visual audio alerts and warnings. In console mode the system can also be configured to provide visual bells. There is a "Visual Bells mini-HOWTO" written by Alessandro Rubini that provides the configuration details available at: http://www.ibiblio.org/pub/Linux/docs/HOWTO/mini/. 4.1. Assistive Technologies for the Hearing ImpairedThe following is a list of assistive technologies for the hearing impaired: 4.1.1. Telecommunications Devices for the Deaf (TDD)TDD allows for the user you to communicate over the telephone using the computer as a text terminal.
4.1.2. Closed CaptioningClosed captioning provides text translation of spoken words to video display. Closed captioning can be used for distance learning, video-teleconferencing, audio from a CD-ROM, and other types of interactive technology.
5. Physically DisabledThere are a wide range of physical disabilities that can impair a user's mobility, and many of these impairments need to be addressed on an individual basis. This section addresses impairments that apply to users who have difficulty using a mouse, pointing device, or keyboard. 5.1. Keyboard NavigationThere are features that are built into the Linux operating system that allow for additional keyboard configuration. In some of the X Windows desktops these settings can be changed from the control center. An application has also been developed for X Windows called AccessX and it provides a graphical user interface for configuring all the AccessX keyboard settings. These settings are:
5.2. Assistive Technologies for the Physically DisabledThe following is a list of assistive technologies for the physically disabled: 5.2.1. On-Screen KeyboardOn-screen keyboards enable a user to select keys using a pointing device, such as a mouse, trackball, or touch pad. This application can be used in place of a standard keyboard.
5.2.2. Speech RecognitionSpeech recognition utilities are used by people with mobility impairments, so they can operate the computer using voice control.
5.3. Additional ResourcesThe following is a list of additional Web sites that may be of interest to users with mobility impairments:
6. Cognitive, Language, and Other ImpairmentsCognitive and language impairments include dyslexia and problems with; memory, comprehension, problem solving, and written language. For many individuals with cognitive and language disabilities, complex graphical displays and inconsistent use of words can make using the computer more difficult. A user with epilepsy can have a seizure from an application with blinking lights and animation. Most desktops now allow users to disable animation. Web browsers such as Mozilla and Netscape allow users to disable graphics. It is important to check the documentation for preferences that are available in the desktop environment you are using, as well as any applications that are used. This section discusses the tools that are available to aid users with these impairments: 6.1. Assistive Technologies for Cognitive, Language and Other ImpairmentsThe following is a list of assistive technologies that can be helpful to users with cognitive, language, and other impairments: 6.1.1. Screen Readers and Speech SynthesisScreen readers with speech synthesis enable the system to read on-screen information and text out loud to the user. This type of assistive technology can be particularly helpful to individuals who have dyslexia and other learning disabilities. Although there are no screen readers available for the GNOME desktop, screen reader applications are available for Linux in console mode that provide this functionality.
6.1.2. Keyboard filters and Word ProcessingKeyboard filters and word processing applications that have word prediction and spell checking utilities can be an excellent aid for users with learning and language impairments. 6.1.3. Speech RecognitionSpeech recognition applications enables you to control the computer with your voice rather than having to type or write out the information.
7. Developing Accessible ApplicationsIt is important to consider accessibility when developing new applications for the Linux operating system. The American Foundation for the Blind, the GNOME Accessibility Project, IBM, Sun, and W3C have written guidelines that are excellent road maps for developing and testing new Linux software. The following Web sites provide the tools, checklists and testing information to help developers write accessible programs for impaired users.
8. Other Helpful InformationThe following is a list of additional information that may be helpful, but is not necessarily targeting a specific disability:
9. AcknowledgmentsThese are the orignal acknowledgments documented by Michael De La Rue. They have been included in their entirety to ensure that each persons efforts to make Linux more accessibile are acknowledged. Much of this document was created from various information sources on the Internet, many found from Yahoo and DEC's Alta Vista Search engine. Included in this was the documentation of most of the software packages mentioned in the text. Some information was also gleaned from the Royal National Institute for the Blind's help sheets. T.V. Raman, the author of Emacspeak has reliably contributed comments, information and text as well as putting me in touch with other people who he knew on the Internet. Kenneth Albanowski kjahds@kjahds.com provided the patch needed for the Brailloterm and information about it. Roland Dyroff of S.u.S.E. GmbH (Linux distributors and makers of S.u.S.E. Linux (English/German)) looked up KTS Stolper GmbH at my request and got some hardware details and information on the Brailloterm. The most major and careful checks over of this document were done by James Bowden, jrbowden@bcs.org and Nikhil Nair nn201@cus.cam.ac.uk, the BRLTTY authors who suggested a large number of corrections as well as extra information for some topics. The contributors to the blinux and linux-access mailing lists have contributed to this document by providng information for me to read. Mark E. Novak of the Trace R and D centre http://trace.wisc.edu/ pointed me in the direction of several packages of software and information which I had not seen before. He also made some comments on the structure of the document which I have partially taken into account and should probably do more about. Other contributors include Nicolas Pitrie and Stephane Doyon. A number of other people have contributed comments and information. Specific contributions are acknowledged within the document. This version was specifically produced for RedHat's Dr. Linux book. This is because they provided warning of it's impending release to myself and other LDP authors. Their doing this is strongly appreciated since wrong or old information sits around much longer in a book than on the Internet. No doubt you made a contribution and I haven't mentioned it. Don't worry, it was an accident. I'm sorry. Just tell me and I will add you to the next version. | ||||||||||||||||||||||