2002 Conference Proceedings

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Two Switch Step Scanning: Access for Children with Severe Physical and/or Multiple Challenges

Linda J. Burkhart
Special Educator, Technology Integration Specialist
6201 Candle Ct., Eldersburg, MD 21784


Many students with severe physical challenges have difficulty accessing communication devices and computer software. Their ability to even access a single switch can be problematic because of their physical challenges. Cause and effect software and one message voice-output devices are available for the very beginning user, but there is a huge leap from these to the more complex use of automatic scanning. This limits the student's access to software and communication devices that could offer more appropriate cognitive content.

Automatic scanning involves only a single switch; however, this method is dependent on the student being able to time a motor response with a predetermined auditory or visual scan. As the student anticipates the approaching item, excitement increases and their ability to control their motor responses decreases.

Two switch step scanning has been around for a long time, however, the technology for its effective use is not always available. For the purpose of this presentation, it will be defined as follows: One switch advances the scan to the next item. To advance to the next item, the switch must be released and activated again. Once the desired item is reached, a second switch is used to select it. Length of time on and off the switch does not effect correct responses and there is no timing involved. This should not be confused with inverse scanning or step scanning with a delay. Since no timing is involved, the task does not require the same intense amount of concentration. If the student becomes distracted or if a social opportunity arises in the middle of the scan, the child can stop, interact, and return to the scanning without having lost his or her place. This allows the child to be more actively involved in the process instead of passively waiting for the scan to reach a desired item. Even though access is slightly more difficult since the child needs two switches instead of one, two switches offer a simpler cognitive map.

This presentation will cover a variety of commercially available software, dynamic displays, and authoring programs that may be accessed by two switch step scanning. Experiences with specific students will illustrate strategies and setups for use with play, communication, emergent literacy, and curricular activities.

Starting off: Where to Begin

Begin with a single switch that is connected to a direct response of some type. Do not use a delay-timer until it is clear that the child understands the cause and effect of the switch. Model use in play situations with peers if possible.

Next, try using a single switch in multiple locations. Note: it is important not to frustrate the child by moving the switch, but with the child's consent, experiment with other locations.

Once the child is able to activate a switch in several locations, move on to two switches. Place one switch in the most preferred location and the other in the second most preferred, Strive to achieve a balance between leaving a switch in one place long enough for the child to accommodate to it, and experimenting with moving the switch to a place that might be easier for the child to access.

Preparation for Two Switch Step Scanning (if Needed)
Two Switch Direct Access - Two Functions

Prepare children if needed for two switch step scanning by using two switches for some direct access activities, If each switch has a different function, the child will have more reason for cognitive engagement. Natural feedback will provide the child with a reason to activate one switch or the other, according to the context or function within the activity. This will provide the child with practice in activating a desired switch for a purpose.

One switch - a battery-operated bubble blower, second switch on a single message device for "Uh oh! We need some more bubbles" when the blower runs out.

One switch for a battery-operated toy animal that kicks a ball to someone else and another switch connected to voice-output: "Throw it to me!"

One switch - battery-operated farm animal or vehicle that is lined up to run into a pile of blocks. The second switch with voice-output: "build up the blocks!" after knocking them down.

One switch with a spin art and the other with voice-output: "put on some more paint" or "I'll show you what color I want now."

One switch on a single switch program on the computer and the other on a voice-output message: "Hey look at this" or "Come see what I did."

One switch spinning a game spinner and the other one with voice-output with an appropriate social comment related to the game or "I'm going to get you!"

Two voice-output messages that have a logical sequence such as "blow up the balloon" and "let it go!"

One switch that controls an action on a computer and when that action finishes or reaches a logical point, that switch no longer works and the other switch controls the result or the next action.

NOTE: Automatic scanning should be considered for any child who does not have trouble activating a switch on cue. Two switch step scanning should be considered for children who have difficulty timing a switch activation

Two Switch Step Scanning

Intermediate step:

One switch moves something on the computer screen and the second switch activates something in relation to where the item has moved. This type of software is not common, but fills a gap for some children who have difficulty understanding step scanning. This is in contrast to typical two switch step scanning where the movement on the screen or display is simulated by a light or highlight showing one item after the next. Some children may have trouble seeing this as movement. Others will understand it right away.


There are an endless variety of activities that can be set up to give children experience with two switch step scanning using authoring programs. Once the child understands the process, then two switch scanning can provide an access strategy to many curricular applications. Music, animation, and logical or humorous sequences are often a good starting place. Emerging literacy for creating stories, playing with sounds and letters, or constructing a rhyme or sentence are also motivating for many children.

Errorless Learning and Practice for Two Switch Step Scanning:

This type of activity offers the child a variety of choices through two switch step scanning, but any response is accepted as the child plays or creates a story. For example, the child can choose the character and events of his or her story by selecting them as the story is created. The resulting story is unique to the child's choices, but there are no "incorrect" stories. Along the same line, the student can choose verses of a song to be sung in any order. Similarly the child can use a series of communication displays to direct the action of another person in a play activity script.

Activities for Increasing Accuracy and Cognitive Engagement:

* Insert some blanks in the array of choices:

* Add slightly negative or illogical items in the array of choices:

When the child selects one of these choices, the feedback shows that it is somehow not logical or not reinforcing. Hopefully the child will not select that item again, and pay more attention to selecting a fun or appropriate choice.

Activities to Reduce Time of Tasks and Provide Success (for children who understand the process of two switch step scanning)

Present a limited array at appropriate times

If the child is just spelling out a controlled set of words, it may be faster for the child to be presented with only the possible letters instead of the whole alphabet array.

If the child is creating sentences, selected words can be offered, instead of the child having to spell out each word.

zMake use of sentence starters, endings and phrases.

Use the feature of branching to present a limited number of choices at each logical step of a discussion, sequence of activity, composition or story.

Set up the array so that incorrect pictures or items disappear after one selection.

Utilize electronic "Word Walls" and "Word Banks" to provide access to frequently used words.

Consider using word prediction or picture/word prediction.

Consider using encoded alphabet displays for spelling.


Two switch step scanning is not for every child, but is simply an option that is frequently overlooked and needs to be considered. Because it eliminates the timing factor, it can make a big difference in accuracy and success for a child. With the use of two switch step scanning for refining switch use, some children can then move on to single switch automatic scanning which may be less fatiguing for them in the long run. Another progression might be to some type of two switch directed automatic scanning, such as one switch for up/down and one switch for left/right on an array or use of Morse Code.

All Rights Reserved: Linda J. Burkhart

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