The careful design of some products makes the products convenient and efficient, brings comfort to customers, and customers don't have to read complex instructions or ask for help from others. On the contrary, some products are designed without considering users' habits and needs, so people will encounter difficulties or confusion in the process of use. This kind of products are called Norman Products.
The shape and size of car radio buttons are the same as those of other equipment switches. It is difficult for users to distinguish which radio button is, according to the above definition, a Norman Product.