Sometimes referred to as DDU’s, Digital Display Units provide the user with a visual commentary of the lift position and current direction of travel (i.e. towards you or away from you). They can be installed on the landings (outside of the lift) and / or on the Car Operating Panel. DDU’s are considered a useful tool for deaf people or those who are hard of hearing. In some instances, e.g. when the lift has panoramic doors, DDU’s on the landings might not be required as it is possible to see where the lift platform is, through the door glass. However, when Fire Doors are fitted, DDU’s are the only way of visually determining where the lift is and whether or not it is in motion.