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Chapter 5 • Alternative Access Technologies 111

crucially, scanning can be achieved using fewer or less precise control movements than
direct selection. Switch scanning is used by people with restricted physical movements,
due to, for example, conditions such as spinal injury, motor neuron disease/amyotrophic
lateral sclerosis (ALS) or muscular dystrophy. For example, Professor Stephen Hawking
utilised a small movement of his cheek to control a single optical switch to access his com-
puter and communication system via scanning (Hawking, 2017). Switch scanning is also
utilised by users with impairment of fine motor control who have difficulty targeting or
operating a control interface accurately.
Coded Access
With coded access, the user generates a code to select the item. A stenotype keyboard and
Morse code are the most commonly recognised methods of coded access. Very few coded
assistive technology access systems are available commercially (TandemMaster, 2017;
WesTest Engineering, 2017) despite studies that suggest they can be faster than scanning
with switches (Nisbet, 1996; Anson et al., 2004; Koester and Arthanat, 2017). Anson et al. note
that coded access requires greater initial learning than direct access or scanning because
the user must memorise the code for each selection, but once mastered it relies on motor
learning and recall; the user does not need to attend to the scanning display or interface.
Seating and Positioning

Functional and comfortable seating and accessible positioning of technology is essential
for effective access (Radell, 1997; Cook and Polgar, 2012). There is little point in investigat-
ing complex and sophisticated adaptations unless the basic positioning of the user, the
control interface and the device are correct and the user is seated in a stable, comfortable
position. Good seating and positioning is a prerequisite for use of technology: refer to the
chapter on Seating and Positioning.

Keyboards

Until about 2005, mechanical keyboards and static displays were the dominant type of
interface found on assistive technologies. For example, the Pathfinder from Prentke
Romich Company (Fig. 5-4) was a state-of-the-art voice output communication aid
launched in 2000, with a membrane keyboard interface. Scanning and direct selection
with an optical pointer were provided via LEDs in each key. Over the last 20 years or so,
dynamic displays and touchscreen keyboards have become ubiquitous and now provide
the principal interface for most of today’s more complex voice output communication
aids, environmental control systems and other assistive technologies. It is notable that
touch or dynamic screen devices are barely mentioned in pioneering assistive technology
textbooks from the 1990s (Cook and Hussey, 1995; Nisbet and Poon, 1998).
The Accent 1400 (Fig. 5-5) is an example of a 2017 dynamic screen communication aid. It
is based on a Windows tablet computer running communication and computer access soft-
ware. It can be accessed using touch, mouse or pointing device, hardware keyboard, switches
or eye gaze. The vocabulary can be displayed using text or a variety of symbol-based systems.