Page 138 - Handbook of Electronic Assistive Technology
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126 HANDBOOK OF ELECTRONIC ASSISTIVE TECHNOLOGY
FIGURE 5-14 Small Marble Mouse and larger SimplyWorks trackball with buttons for click and drag�
FIGURE 5-15 Microsoft Windows on-screen keyboard�
Trackballs designed for the assistive technology market may have features such as but-
ton guards to prevent accidental activations, separate buttons for functions such as drag
and double click and speed adjustment built into the device. They usually also have insert
nuts for fixing to trays and tables, and sockets so that switches can be plugged in to gener-
ate mouse button clicks.
Jennifer’s Case Study
Jennifer is 14 years old and as a result of Duchenne’s muscular dystrophy has limited range
of movement in her hands and experiences fatigue. She cannot reach across a physical
keyboard and is very successful with a standard Windows on-screen keyboard (Fig. 5-15),
which she accesses using a Marble Mouse placed on her lap. She rests her hand on the
trackball and she can move the ball with her finger tips. She uses the ‘Hover over keys’
(Dwell Select) facility to click, which is more efficient and requires less physical effort than
clicking the button on the trackball.
