Computer Access Using Switches Sarah Crosbie, MS.Ed, OTR/L

Switch Access: Individuals with severe motor disabilities cannot who cannot operate any type of adapted keyboard or mouse must rely on switch access. Not to be confused with a flatbed scanner for input!!

This is a slow, but functional alternative for individuals with significant physical limitations. The individual only needs to have consistent control of one or more anatomical sites for accessing a single switch, or multiple switches.

Setting up a switch access system A switch cannot be plugged directly into a computer. Instead a Switch Interface is required to bridge the gap between the switch and the computer's USB, serial, or PS/2 port.USBserial PS/2 The computer (1) is connected to the computer-switch interface (2) which is then connected to the the switch (3). The interface jack that is used determines what the computer receives when the switch is pressed.

Types of computer-switch interfaces

Scanning Software A scan is comprised of equivalent key and mouse choices that appear on the screen when a software program is running. The student goes through (scans) the various commands and then activates a switch to make a choice. To use a scanning system, a student must be able to: * Make a choice from a field of options * Watch/listen and wait until the choice is highlighted by the scanning box * Activate a switch to select their choice. There is a range of 'cause and effect' switch programs that introduce the basic concepts of switching

Teaching switch skills: Cause&Effect h.uk/resources/restop.htmhttp:// h.uk/resources/restop.htm ROG_NUM=553http:// ROG_NUM=553

There are several "direct scan" methods available for accessing the computer. *Automatic scanning: continuous movement of indicator. The highlight pauses at each group/item for a pre-set time * Step scanning: indicator moves one item at a time each time the switch is activated * Inverse scanning: advance the highlight by holding a “move” switch down. While the switch is held down, the highlight pauses at each item for a pre- set time After selecting a method to scan-- a decision as what "selection set" format is best: Sequential *Rotary Row-column Group c_scanning_patterns.htmhttp://faculty.washington.edu/dowden/tcollab_aac_files/aac_module_scanning/aa c_scanning_patterns.htm

Switch Types and Positioning When considering which switch to use it is essential that the user is positioned properly in order to exert maximum control over the switch The switch used should capitalise on their most reliable and consistent movement (ex: head, chin, knee, foot) Switches also come in a variety of formats; single, dual and multiple switches. They can be activated in a variety of ways, for example; pressure switch, movement switch (blinking of the eye), vibration switch, sound switch and a sip and puff switch (by sucking and blowing).