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 Most 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 ). Note that on most architectures the boot loader interprets your keyboard as a QWERTY keyboard. 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 &enterkey; 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. 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. Support for software speech synthesis can be activated by selecting it in the boot menu by typing s &enterkey;. The first question (language) is spoken in english, and the remainder of installation is spoken in the selected language (if available in espeak). Support for hardware speech synthesis devices is available only alongside support for graphical installer. 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. 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 &enterkey;. For users with low vision, the installer can use a high-contrast theme that makes it more readable. To enable it, append the theme=dark boot parameter. Alternatively, &debian; can be installed completely automatically by using preseeding. This is documented in .