Assessing Student's Needs for Assistive Technology (ASNAT)

Chapter 2 – Computer Access
• Scanning-When an individual is not able to accurately use direct selection, scanning can be
considered as an input method. Scanning is less efficient and more time consuming than direct
selection. However, it is a viable means of computer input. The items that are scanned and available
for computer input are dependent on the software interface. Programs can offer a few choices for
targeted responses (e.g., First Words by Laureate Learning Systems, Inc.) or a full array of keyboard
options through an onscreen keyboard. Many software programs offer preprogrammed scanning
options. Items are scanned using a number of scanning modes which include:
• Automatic - scanning proceeds automatically, and the individual activates a switch to stop
scanning and make a selection
• Step - scanning does not proceed automatically; the individual must repeatedly activate a switch
to proceed to desired selection; to select an item the user must refrain from hitting the switch for
a period of time
• Inverse - scanning does not proceed automatically; individual maintains switch activation to
cause scanning to proceed - releasing switch makes selection
• Block - scanning selections are highlighted in groups (or blocks); the user first chooses a group,
then makes individual selection within the group; can be used with automatic, inverse, or step
methods
• Directed - scanning proceeds by use of two or multiple switches or the use of a joystick; the
individual chooses the direction of the scan
A variety of switches exist which can be used for scanning. Virtually any action that can be made
reliably and consistently can be utilized to activate a switch for scanning. The following are switch
categories (AbleNet, Inc., 1996):
• Pressure (e.g., Jelly Bean ® or plate switch): momentarily activated by applying light pressure or
touch to the switch using any body part
• Lever (also referred to as wobble or leaf): using any body part to move a lever from a vertical or
horizontal position to activate
• Muscle sensor (e.g., Twitch Switch): sensitive electronic switch activated by any muscle
movement
• Sound Sensitive (e.g., Voice Activated Switch): activated when a loud noise is made such as a
clap or vocalization
• Pneumatic (e.g., Sip and Puff Switch, Squeeze Switch): activated by compressed air
• Tilt (e.g., Tilt Switch): activated when the switch itself is rotated or tilted
• Pull (e.g., String Switch): activated by pulling a cord attached to the switch
• Photosensitive (e.g., Photocell Switch): activated when either light shines on or is prohibited
from a photo cell
Switches come in all shapes, sizes, and forms. Consider the following switch characteristics when
choosing a switch for an individual:
• Surface size: e.g. small, medium, large, circular, square, etc.
• Surface texture: e.g. option for mounting graphics or symbols on the switch
• Pressure: force required for activation
• Travel/excursion: distance switch must travel from resting position to activation
Assessing Students’ Needs for Assistive Technology (2004) 69