Redundancy - Augment Overloaded Sensory System

Designing displays for more than one sense modality is also preferred to compensate for overload of one or more senses. In these instances, the use of an alternate sense system may be necessary to attract attention, alert, or warn a user. The most frequent use of redundancy in displays is the use of auditory alarms to compensate for overload of the visual channel. Examples include Air Traffic Control displays and Aircraft Flight Deck Displays.

	Air Traffic Control Displays give visual indicators as well as different auditory tones to signal loss of separation between aircraft, aircraft altitude below safe minimum, emergency code received, and subsystem failures.
Modern commercial aircraft present complex arrays of visual displays and indicators. Auditory tones are used to alert the pilot and crew of critical events. (Boeing, 747 cockpit)