Saturday, May 5, 2012

Switch Use

What is a switch?

Switches are used with all forms of assistive technology.  The easiest way to think about a switch is a device that can start or stop a device.  The most common type of switch is activate with some kind of touch, creating the contact of two surfaces or switches to work with an assistive technology device.

What kind of switches are there?

There are literally hundreds (if not thousands) of switches available for assistive technology access.  Switches are meant to be accessed by the available body part or motion that is strongest for the user.  This area of access needs to be consistent and not create fatigue with extended use.  The area of access can also vary dependent on the position of the individual.  For example, a person might use their finger for switch access when in their wheelchair and a sip and puff switch for when they are in their bed.

When evaluating what is the best switch site, it is recommended to evaluate distal to proximal.  This means, start with the hands or fingers.  If this is not an appropriate site, what can be done as we move up?  Are gross movements easier than fine movements?  If the individual cannot use their arms, what other areas are appropriate?  

Addition considerations for switch use is the amount of force required to press the switch (if it is a tactile switch).  When looking at the "specs" of the switch, you can find the amount of force in ounces or pounds for access.  This is very important for an individual with limited movement or a harder switch user that needs a more durable switch.

How can a switch be mounted for access?

There are many ways that a switch can be mounted.  Switches can be mounted to a wheelchair, tabletop, or any other surface for best access.  If appropriate, Velcro can be instrumental in attaching a switch for access.  

If additional mounting options are required, a simple tabletop mount might be appropriate.

Removable mounts can be used that would attach the switch to a wheelchair, tabletop, or any other surface.  These mounts can be purchased with varying arm lengths and plate sizes.

More permanent mounting can be done in wheelchair components such as in the headrest.  Conductive fabric and clothing can be used to create novel switches, making it a part of clothing.

What if the user cannot "hit" a switch?

There are switch options for an individual with limited or lack of movement that would be required in order to touch a switch.

Sip and puff:  A sip and puff switch is a great option for users with limited movement or issues with significant fatigue when attempting to touch a switch. Through the actions of sipping and puffing, the user can control their assistive 
technology device.

Proximity:  A proximity switch is activated when the user gets closer to the switch.  Dependent on the switch chosen, the range of how close the individual the user has to get to the switch to activate it can vary.  This switch can be mounted pointing at any area for the user.

EMG switch:  An EMG switch is also known as a muscle twitch switch.  A muscle twitch sensor is placed on a muscle that can be used consistently without pain or fatigue.  When the user contracts the muscle, it activates the assistive technology service. 

Sound switch:  This is a switch option that has been around for sometime.  The Clapper is an example of a sound switch.  When the individual makes a sound, it activates the device such as a communication device.  There are very sensitive sounds switches available allowing for changes in the sensitivity, how loud or soft the sounds needs for access.  

To conclude, the importance of switches and their positioning is very important. If the individual is not setup with the best switch for the strongest access site the user will not be efficient or conserve their energy.  Through a full evaluation, an appropriate recommendation can be made not only for the device but for the appropriate access method. 

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