An ambiguous keyboard based on character graphical association for the severely physically handicapped

Ambiguous keyboards can be used instead of scan matrices in Scanning Systems in order to increase the text entry rate. We present a novel alternative to assigning letters to keys by taking into consideration the shapes of lowercase letters in order to create simple layouts, leading to families of keyboards with 2, 3 and 4 keys. We have chosen the best 3-key layout using a single switch scanning system and a word level disambiguation algorithm with a 10,911 word dictionary and we have tested it. We predict 16.6 wpm for an expert user with a 0.5 second scan period.