5.2. Accessibility

Some users may need specific support because of e.g. some visual impairment. USB braille displays are detected automatically (not serial displays connected via a serial-to-USB converter), but most other accessibility features have to be enabled manually. On machines that support it, the boot menu emits a beep when it is ready to receive keystrokes. Some boot parameters can then be appended to enable accessibility features (see also Section 5.1.7, “The Boot Screen”). Note that on most architectures the boot loader interprets your keyboard as a QWERTY keyboard.

5.2.1. USB Braille Displays

USB braille displays should be automatically detected. A textual version of the installer will then be automatically selected, and support for the braille display will be automatically installed on the target system. You can thus just press Enter at the boot menu. Once brltty is started, you can choose a braille table by entering the preference menu. Documentation on key bindings for braille devices is available on the brltty website.

5.2.2. Serial Braille Displays

Serial braille displays cannot safely be automatically detected (since that may damage some of them). You thus need to append the brltty=driver,port,table boot parameter to tell brltty which driver it should use. driver should be replaced by the two-letter driver code for your terminal (see the BRLTTY manual). port should be replaced by the name of the serial port the display is connected to, ttyS0 is the default, ttyUSB0 can be typically used when using a serial-to-USB converter. table is the name of the braille table to be used (see the BRLTTY manual); the English table is the default. Note that the table can be changed later by entering the preference menu. Documentation on key bindings for braille devices is available on the brltty website.

5.2.3. Software Speech Synthesis

Support for software speech synthesis is available on all installer images which have the graphical installer, i.e. all netinst, CD and DVD images, and the netboot gtk variant. It can be activated by selecting it in the boot menu by typing s Enter. The textual version of the installer will then be automatically selected, and support for software speech synthesis will be automatically installed on the target system.

The first question (language) is spoken in english, and the remainder of installation is spoken in the selected language (if available in espeak).

The default speech rate is quite slow. To make it faster, press CapsLock+6. To make it slower, press CapsLock+5. The default volume should be medium. To make it louder, press CapsLock+2. To make it quieter, press CapsLock+1. To get more details on the browsing shortcuts, see the Speakup guide.

5.2.4. Hardware Speech Synthesis

Support for hardware speech synthesis devices is available on all installer images which have the graphical installer, i.e. all netinst, CD and DVD images, and the netboot gtk variant. You thus need to select a Graphical install entry in the boot menu.

Hardware speech synthesis devices cannot be automatically detected. You thus need to append the speakup.synth=driver boot parameter to tell speakup which driver it should use. driver should be replaced by the driver code for your device (see driver code list). The textual version of the installer will then be automatically selected, and support for the speech synthesis device will be automatically installed on the target system.

5.2.5. Board Devices

Some accessibility devices are actual boards that are plugged inside the machine and that read text directly from the video memory. To get them to work framebuffer support must be disabled by using the vga=normal fb=false boot parameter. This will however reduce the number of available languages.

If desired a textual version of the bootloader can be activated before adding the boot parameter by typing h Enter.

5.2.6. High-Contrast Theme

For users with low vision, the installer can use a high-contrast color theme that makes it more readable. To enable it, append the theme=dark boot parameter.

5.2.7. Preseeding

Alternatively, Debian can be installed completely automatically by using preseeding. This is documented in Appendix B, Automating the installation using preseeding.

5.2.8. Accessibility of the installed system

Documentation on accessibility of the installed system is available on the Debian Accessibility wiki page.