Text Entry System Based on a Minimal Scan Matrix for Severely Physically Handicapped People

Improving augmentative communication systems is necessary for severely physically handicapped people because of the low rate of text entry that doesn't even permit them to communicate simultaneously with other people. This paper presents a reduced virtual keyboard based on scanning with only one switch. The scan matrix consists of only two cells, so ambiguity is present due to the assignment of 26 characters to both keys. In order to disambiguate, users enter each letter in two stages. An estimation of the text entry rate for an expert user is 10.1 words per minute using a scan rate of 0.5 seconds, although this value should be adapted for each individual, leading to different rates.