Is important information communicated through multiple senses?
The two-senses principle states that products should appeal to at least two of the three senses of sight, hearing and touch. This ensures that products are also accessible to people with a limitation of one sense.
It is especially important for warning or usage instructions and in public spaces.
Z. E.g. An acoustic signal is accompanied by light/vibration (e.g. cell phone).
Z. E. Buttons are marked with cuneiform and Braille in addition to text (Ex. Elevator buttons).
Z. E.g. Digital text is available as voice output (e.g. ticket vending machine).