5.2. 辅助功能

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 beeps when it is ready to receive keystrokes. It beeps once on BIOS systems, and beeps twice on UEFI systems. Some boot parameters can then be appended to enable accessibility features (see also 第 5.1.7 节 “引导界面”). Note that on most architectures the boot loader interprets your keyboard as a QWERTY keyboard.

5.2.1. Installer front-end

The Debian installer supports several front-ends for asking questions, with varying convenience for accessibility: notably, text uses plain text while newt uses text-based dialog boxes. The choice can be made at the boot prompt, see the documentation for DEBIAN_FRONTEND in 第 5.3.2 节 “Debian 安装程序的参数”.

5.2.2. USB 盲文点显器

系统应该可以自动检测到 USB 盲文点显器。然后自动选取安装程序的文本界面,该设备也会被自动安装到最终系统中。您只需要在引导菜单中按下 Enter 键。一旦 brltty 启动,您就可以通过菜单选择 braille table。在 brltty website 可以找到盲文点显器的键绑定文档。

5.2.3. 串口盲文点显器

Serial braille displays cannot safely be automatically detected (since that may damage some of them). You thus need to append the brltty=driver,port boot parameter to tell brltty which driver and port 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. A third parameter can be provided, to choose 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. A fourth parameter can be provided to pass parameters to the braille driver, such as protocol=foo which is needed for some rare models. Documentation on key bindings for braille devices is available on the brltty website.

5.2.4. 软件语音合成(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. To just accept the default answer for a question, simply press Enter at the prompt. To provide an empty answer for a question, type ! at the prompt. To get back to the previous question, type < at the prompt.

5.2.5. 硬件语音合成(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.

硬件语音合成设备无法自动识别。您需要添加 speakup.synth=driver 引导参数告诉 speakup 使用哪种驱动程序。driver 应替换为该设备的驱动程序代码(参阅 driver code list)。接着安装程序的文本界面自动被选中,对于语音合成设备的支持也会被自动安装到最终系统里面。

5.2.6. 板卡设备

一些辅助设备实际上是插入计算机里面的板卡,它们直接从显存里面读取字符。要让它们工作,需要使用引导参数 vga=normal fb=false 禁止使用 framebuffer。然而这会减少可用语言的数量。

假如希望使用字符界面的 bootloader,可以在添加引导参数前输入 h Enter

5.2.7. 高亮主题

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.

5.2.8. Zoom

For users with low vision, the graphical installer has a very basic zoom support: the Control++ and Control+- shortcuts increase and decrease the font size.

5.2.9. 预置

另外,Debian 可以使用预置进行完全自动安装。相关文档参见 附录 B, 使用预置自动进行安装

5.2.10. Accessibility of the installed system

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