Modern technology and microelectronics in particular have made a considerable impact on the rehabilitation of severely disabled children and adults. These people cannot normally use a computer keyboard directly and alternative input devices have to be used. Keyboard emulators allow the computer to be used to its fullest extent and work through a variety of switches. One type of emulator is an illuminated alphanumeric display. The characters on the display are scanned sequentially and the disabled operator selects the required character by closing a suitable switch.