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A SWITCH IN TIME

Jana Birch, M.A.
Computerade Products
2346 Wales Drive
Cardiff, California 92007
Voice/Fax: (619) 942-3343
Email: jbirch@cts.com

Web Posted on: November 22, 1997


A SWITCH IN TIME is a teaching guide for switch control and switch scanning skills. It is due to be published along with supporting software in late 1997. For further information, contact the author above.

The number of children and adults with disabilities who are destined to become single switch users is a relatively small portion of the population. Switch control is a very slow method of control, but for some it is the door to independence. The ability to interact with one's environment and to independently control something can make the difference between how that person views life and how others view that person.

There are other options to adaptive control besides single switch scanning. The ability to directly choose is usually faster than waiting for a signal to get to the choice you want. Direct selection is not the best option when the effort to move to that choice requires a lot of time, results in many accidental choices, or exhausts the user.

Scanning, on the other hand, requires a great deal of patience along with the ability to reliably control a single switch and to maintain attention on the desired choice until the signal arrives there. Someone with a high level of distractibility and a low level of patience would not be a good candidate for scanning.

It is always better however to do something rather than nothing. If you are still searching for the perfect method of control for someone, you may want to begin with some of the beginning levels of switch control, especially when working with children. Learning to control something independently makes a profound difference in a child's sense of self and developing interest in the environment around them. Learning to exercise choice in that control helps the child to develop even further.

What is scanning?

Direct selection means directly choosing what you want whether it be through touch, eye gaze, adapted mouse control on a computer or some other type of adaptation. Scanning involves a middle man, a signal, which must be watched or listened to. When the signal reaches the desired choice, that is when the selection must be made.

Scanning involves:

  • 1. the ability to reliably control a single switch within a defined time frame
  • 2. the ability to wait without activating that switch
  • 3. the ability to attend to a signal while waiting
  • 4. the ability to respond within a defined time frame when the signal reaches the desired choice
  • 5. the ability to recognize whether the desired choice was successfully made and
  • 6. the ability to stop responding and begin to wait and attend to the signal again.

Comparing different types of scanning

There are various forms of scanning to meet different needs.

Automatic scanning:
The most commonly used form of scanning is auto scanning. During an automatic scan the signal moves on its own according to the rate set. The objective is to watch the location desired and press a switch when the signal is at that location.
Step scanning:
During a step scan, the switch is used to move the signal. The user must press and release the switch repeatedly. When the desired location is reached, the user must stop and wait. After a delay determined by the rate setting, the choice where the signal is located is recognized. There is usually then an auditory signal indicating the user may begin using the switch to scan for another choice.
Inverse scanning:
The inverse scan is similar to a step scan, however does not require the release of the switch until the desired location is reached. The switch is simply held down and the signal moves according to the rate set. Selection is made upon release of the switch.
Manual scanning:
The manual scan is much like the step scan, however it requires two switches and eliminates the need for a rate setting. It is ideal for the user who has difficulty maintaining a consistent timed response, but it requires the ability to control two switches and coordinate and isolate the physical response for both. It is cognitively more demanding as well. You may encounter manual scanning in many electronics that have limited buttons such as programming your television or making choices on a game machine. Personally, I have found this the most frustrating and difficult method.
Continuous scanning:
Continuous scanning is a style of scanning that can be implemented with auto or inverse scanning. A continuous scan does not jump between choices, but moves instead along a continuous line or circle. It allows more options for selection, but also requires much finer control. A rotary (clock type) scanner is one example of a continuous scan. Scanning on a computer which is designed to simulate mouse control is usually based on a continuous scan. Cross Scanner (R. J. Cooper & Associates) is one example of a continuous scan.

Types of switch control

Switch control may be used in other ways besides scanning on a computer or communication device. The way in which these switches function may vary. If a variety of methods are being used with one individual it could be very confusing for them. Some persons may be able to understand the different ways in which switches function, but when learning switch control it is best to introduce only one type at a time.

Momentary:
A battery-operated toy that has been adapted for switch control is usually working in a momentary mode. The toy goes when the switch is activated and stops when the switch is released. The switch is held down to keep the toy going. This type of control is opposite from the skill that must be learned to operate an automatic scanning system.

Multiple switch control with an electric wheelchair usually functions in momentary mode as well. It could be very confusing to a beginner learning to scan if they are being taught to use a switch one way for electric wheelchair control and another way to operate their computer or communication device. An inverse scanning approach would be most similar to the momentary form of control, because the signal moves only when the switch is held on, but it may not be the best choice since a computer is much more sensitive to momentary releases of a switch than an electric wheelchair.

Timed:
Use of a switch control unit or timer (available from Ablenet) can be used to designate a time period for which the device will remain active after the switch has been activated and released. This is very useful for cause and effect training for a user who has difficulty holding a switch on for any length of time. It is recommended to use a timed method with cause and effect training for individuals who are likely to move on to learn auto scanning.

On/Off:
An on/off switch is often used with environmental control systems. A light switch is a good example. One touch turns the switch on. The switch must be touched again to turn it off. The on/off method may work well with a rotary scanner where a pointer moves around in a circle.

When is an individual ready to learn scanning?

The best key to readiness for scanning is observation of the ability to wait, then activate a switch-operated activity when given a designated cue.

Begin by introducing the user to cause and effect activities with a single switch. These can include operation of battery-adapted toys, use of appliances connected to a control unit such as the Powerlink from Ablenet, Inc., or responding to simple cause and effect software on a computer.

Observe whether the user is beginning to demonstrate a sense of timing. If the activity is on a timer, does the user stop hitting the switch while the activity is going, then return to the switch when the activity stops? Can the user respond to simple verbal instructions for when to start and stop? These skills can be practiced with activities or even with a simple signal buzzer.

When you begin to observe these skills, you can develop a game with a timer. See how long it takes the user to activate or release the switch. See how quickly the user can activate the switch five times in a row. Use these timing games to evaluate different types of switches, switch placement, or positioning.

Use your results from these timing games to choose a scanning time that will allow success 90% of the time. If the user can activate more quickly and consistently than release, begin with automatic scanning. If the user can release the switch more quickly and consistently, you may want to consider inverse scanning. If the user is able to press the switch repeatedly with ease and stop after a designated number of times, consider step scanning as an option. Step scanning may be preferred especially if the user attends better to the moving signal when it is under his or her control rather than moving at a set rate.

The software, CATCH THE COW, is designed for training switch scanning skills with individuals who have reached the level described above. The Macintosh version is due to be released in late 1997. The author can be contacted for further information.

A SWITCH IN TIME will provide a series of guide sheets and training activities that can assist teachers, therapists, or family members in teaching beginning switch control through advanced scanning skills. The author can be contacted for further information.


References

Ablenet, Inc., 1081 Tenth Ave., S.E., Minneapolis, MN 55414-1312, telephone: (800) 322-0956.

R. J. Cooper & Associates, 24843 Del Prado, #283, Dana Point, CA 92629, telephone: (800) RJCOOPE.