Keyboard interface of a speech synthesiser for the physically handicapped

This paper presents an evaluation of different keyboard display coding schemes for the operation of a speech synthesizer by children with cerebral palsy. The synthesizer uses 128 function keys to access 393 words and 45 phonemes. Most keys activate four different words or phrases, requiring the user to search for the desired word and to select the correct positional level prior to pressing the key. This process was quite slow with the existing machine due to the design of the keyboard display. A study was conducted in which five cerebral palsied subjects operated the device using four additional keyboard overlays representing different combinations of colour coding and lettering case. The time was measured for subjects to key in 10-word sequences. It was determined that one overlay using a colour and position redundant coding scheme with upper-case lettering resulted in a saving of more than 20 s/word compared with the original display.