Chapter 10. Configuring a System for Accessibility
- a speech synthesizer, which provides a speech output
- a braille display, which provides a tactile output
- configure the
brlttyservice, as described in Section 10.1, “Configuring the
- switch on the Always Show Universal Access Menu, as described in Section 10.2, “Switch On Always Show Universal Access Menu”
- enable the Festival speech synthesizer, as described in Section 10.3, “Enabling the Festival Speech Synthesis System”
10.1. Configuring the
brlttyservice to provide tactile output for visually impaired users.
brlttyis running. By default,
brlttyis disabled. Enable
brlttyto be started on boot:
~]# systemctl enable brltty.service
Authorize Users to Use the Braille Display
/etc/brltty.conffile is suitable even for the file systems where users or groups cannot be assigned to a file. The procedure using the
/etc/brlapi.keyfile is suitable only for the file systems where users or groups can be assigned to a file.
Procedure 10.1. Setting Access to Braille Display by Using
- Open the
/etc/brltty.conffile, and find the section called Application Programming Interface Parameters.
- Specify the users.
- To specify one or more individual users, list the users on the following line:
user_1, user_2, ...# Allow some local user
- To specify a user group, enter its name on the following line:
group# Allow some local group
Procedure 10.2. Setting Access to Braille Display by Using
- Create the
~]# mcookie > /etc/brlapi.key
- Change ownership of the
/etc/brlapi.keyto particular user or group.
- To specify an individual user:
- To specify a group:
- Adjust the content of
/etc/brltty.confto include this:
Set the Braille Driver
/etc/brltty.confspecifies a two-letter driver identification code of the driver for the braille display.
Procedure 10.3. Setting the Braille Driver
- Decide whether you want to use the autodetection for finding the appropriate braille driver.
- If you want to use autodetection, leave
braille driverspecified to
auto, which is the default option.
WarningAutodetection tries all drivers. Therefore, it might take a long time or even fail. For this reason, setting up a particular braille driver is recommended.
- If you do not want to use the autodetection, specify the identification code of the required braille driver in the
braille-driverdirective.Choose the identification code of required braille driver from the list provided in
/etc/brltty.conf, for example:
xw# XWindowYou can also set multiple drivers, separated by commas, and autodetection is then performed among them.
Set the Braille Device
/etc/brltty.confspecifies the device to which the braille display is connected. The following device types are supported (see Table 10.1, “Braille Device Types and the Corresponding Syntax”):
Table 10.1. Braille Device Types and the Corresponding Syntax
serial:ttyS0# First serial device braille-device
usb:# First USB device matching braille driver braille-device
usb:nnnnn# Specific USB device by serial number braille-device
bluetooth:xx:xx:xx:xx:xx:xx# Specific Bluetooth device by address
usb:does not work. In this case, identify the virtual serial device that the kernel has created for the adapter. The virtual serial device can look like this:
serial:ttyUSB0You can find the actual device name in the kernel messages on the device plug with the following command:
~]# dmesg | fgrep ttyUSB0
Set Specific Parameters for Particular Braille Displays
braille-parametersdirective passes non-generic parameters through to the braille driver. Choose the required parameters from the list in
Set the Text Table
/etc/brltty.confspecifies which text table is used to encode the symbols. Relative paths to text tables are in the
Procedure 10.4. Setting the Text Table
- Decide whether you want to use the autoselection for finding the appropriate text table.
- If you want to use the autoselection, leave
auto, which is the default option.
auto# locale-based autoselectionThis ensures that local-based autoselection with fallback to
- If you do not want to use the autoselection, choose the required
text-tablefrom the list in
/etc/brltty.conf.For example, to use the text table for American English:
en_US# English (United States)
Set the Contraction Table
/etc/brltty.confspecifies which table is used to encode the abbreviations. Relative paths to particular contraction tables are in the
contraction-tablefrom the list in
en-us-g2# English (US, grade 2)