Page 143 - Handbook of Electronic Assistive Technology

Chapter 5 • Alternative Access Technologies 131

FIGURE 5-19 Quha Zono head-operated mouse� Courtesy of Quha.

Direct Mouse Control With Multiple Switches
If the user can control four or five switches or a switched joystick, they can be connected
via a USB Switch Interface to control up, down, left and right movements and the mouse
button.

Scanning Mouse Control With One or Two Switches
If a user cannot access multiple switches or a switched joystick to control the pointer
directly, there are technologies to give control over the mouse using one or two switches
using scanning.
The Track-IT! USB Switch Interface scans each mouse direction in turn. The user
20
clicks a switch when the desired direction is reached and the mouse moves in that direc-
tion until the switch is released. The mouse buttons can also be controlled.
21
Switch scanning control of the mouse pointer is built in as standard to MacOS and
provided in computer access software packages such as Grid3, ACAT and GrapeVine. 24
23
22
Single switch control of the pointer is particularly slow so it is important to make use of
keystroke equivalents, macros and scanning screen markers to increase speed of access.
The development of head-controlled mice and eye-gaze systems has reduced the popular-
ity of switch and scan control of the mouse pointer, but it can still be an important access
technique.

20 Track-IT! mouse control interface: https://www.pretorianuk.com/track-it.
21 Use switch control to interact with your Mac: https://support.apple.com/en-gb/HT202865.
22 Grid 3: https://thinksmartbox.com/product/grid-3/.
23 Assistive Context-Aware Toolkit: https://01.org/acat.
24 Grapevine Computer Access: http://www.grapevineat.ie/.