According to the Center for Universal Design, headquartered in North Carolina State University, UD has seven basic principles.
Simple and Intuitive Use
The design and devise is user friendly. It is easy to understand, uses a standard way of presentation, and does not require a special skills, level of education , language and experience. In the picture, the fire alarm uses a push button that is standard and color red. Even a child can understand that it is a panic button.