For 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/.
The following is a list of assistive technologies for the hearing impaired:
TDD allows for the user you to communicate over the telephone using the computer as a text terminal.