Page 152 - Handbook of Electronic Assistive Technology

140 HANDBOOK OF ELECTRONIC ASSISTIVE TECHNOLOGY

FIGURE 5-26 Switch scanning� The orange (grey in print version) highlighter moves from item to item� When the
required item is highlighted, the user activates a switch to select it�

A range of switch interfaces that connect to USB ports are available. Some of these
emulate a USB keyboard or mouse (i.e., the switch generates a Space or Return keypress,
or mouse click) while others are supplied with software that can be programmed to gener-
ate keyboard, mouse or gamepad commands.
Electronic assistive technologies are typically designed to operate with different types
of switch interface, and may use different keys for their operation, and so it is essential to
configure the software and switch interface to be compatible.

Scanning Access
Scanning is a term used to describe a method of access where items in the selection set
are highlighted in turn (Colven and Judge, 2006). When the desired item is highlighted, the
user activates the switch to select it (Fig. 5-26).

Simple Scan
With a simple scan, each item in the selection set is highlighted sequentially. Simple scan
is most suitable for choosing from a small number of items in the selection set.

Group Scan
Simple scan is very slow when working with a large selection set, and group scanning offers
more efficient and quicker access. Row/column and column/row scanning are common
types of group scan (Fig. 5-27).