Blind people and persons with low vision have difficulty in reading the labelling on keys. It is important that the layouts of keys be kept in a standard arrangement. It is also important to set out the keys in a way that makes it easy to distinguish between the main numerical keys and other function keys. Variation in the size, shape and position of function keys will help differentiation. Terminals which are incorporated in computers will usually have the calculator layout for the number keys.
Telephone features that make a difference .