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Switch access scanning
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<h2 id="scanning-patterns">Scanning patterns</h2> <p>A scanning pattern refers to the way items in the selection set are presented to the user. It allows for easier item selection as the scanning is systematic and predictable.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> Three primary scanning patterns exist: </p> <ul><li>In <i>circular scanning</i>, individual items are arranged in a circle (like the numbers on a clock face) and the scanning indicator moves in a circle to scan one item at a time. Although circular scanning is visually demanding, it is the simplest scanning pattern as it is cognitively easy to master.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a></li> <li>In <i>linear scanning</i>, items are usually arranged in a grid and the scanning indicator moves through each item in each row systematically.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> Although linear scanning is cognitively more demanding than circular scanning, it is relatively straightforward and easy to learn.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> However, it may be inefficient if there are many items in the set (e.g., in a grid consisting of 8 items per row, if the desired item were the 7th item in the 4th row, the scanning indicator would have to scan through 30 undesired items first before reaching the desired item.</li> <li>In <i>group-item scanning</i>, items are grouped (e.g., by row, column, or other meaningful categories) and the scanning indicator will first scan by groups. Once the scanner selects the group his desired item belongs to, the scanning indicator will scan each item in the selected group. Among the variations of group-item scanning, the most common is <i>row-column scanning</i> where the items are grouped in rows.<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a><a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a></li></ul> <h2 id="scanning-control-techniques">Scanning control techniques</h2> <p>Scanning control and item selection occurs through switch activation in three general ways: </p> <ul><li>In <i>directed (or inverse) scanning</i>, the indicator will only scan in the preset pattern when the user holds down a switch. Selections are made when the switch is released.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a></li> <li>In <i>automatic (regular or interrupted) scanning</i>, the indicator scans in the preset pattern on its own and item selection occurs when the scanner hits a switch.<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a></li> <li>In <i>step scanning</i>, the user controls each movement (or step) of the scanning indicator through its preset pattern by hitting a switch. To select an item, the AAC user hits a second switch once the indicator reaches his desired item. Because of the constant switch activation, this method might be too fatiguing for the certain scanners, including those with <a href="/facts/Amyotrophic_lateral_sclerosis/9fIXnNL4">Amyotrophic lateral sclerosis</a>, but is easier cognitively.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></li></ul> <h2 id="notes">Notes</h2> <ul><li>Beukelman, D. & Mirenda, P. (2005 Augmentative and Alternative Communication: Supporting Children and Adults with Complex Communication Needs (3rd edition) Baltimore: Brookes.</li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://www.toby-churchill.com/en/products/scanning-lightwriters">[1]</a> A Demonstration of scanning</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Beukelman & Mirenda, 2005, p. 92 <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Vinson, Betsy Partin (2001). Essentials for speech-language pathologists. Cengage Learning. pp. 150–51. ISBN 978-0-7693-0071-9. <a href="978-0-7693-0071-9" target="_blank">978-0-7693-0071-9</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Beukelman & Mirenda, 2005, p. 97 <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>American Speech-Language-Hearing Association. (2004) Roles and Responsibilities of Speech-Language Pathologists With Respect to Augmentative and Alternative Communication: Technical Report <a href="http://www.asha.org/policy" target="_blank">http://www.asha.org/policy</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Hedman, Glenn (1990). Rehabilitation Technology. Routledge. pp. 100–01. ISBN 978-1-56024-033-4. <a href="978-1-56024-033-4" target="_blank">978-1-56024-033-4</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Beukelman & Mirenda, 2005, p. 97-101 <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Beukelman & Mirenda, 2005, p. 97 <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Radomski, Mary Vining & Trombly Latham, Catherine A. (2007). Occupational therapy for physical dysfunction. Lippincott Williams & Wilkins. pp. 524–25. ISBN 978-0-7817-6312-7. <a href="978-0-7817-6312-7" target="_blank">978-0-7817-6312-7</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>American Speech-Language-Hearing Association. (2004) Roles and Responsibilities of Speech-Language Pathologists With Respect to Augmentative and Alternative Communication: Technical Report <a href="http://www.asha.org/policy" target="_blank">http://www.asha.org/policy</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Hedman, Glenn (1990). Rehabilitation Technology. Routledge. pp. 100–01. ISBN 978-1-56024-033-4. <a href="978-1-56024-033-4" target="_blank">978-1-56024-033-4</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>American Speech-Language-Hearing Association. (2004) Roles and Responsibilities of Speech-Language Pathologists With Respect to Augmentative and Alternative Communication: Technical Report <a href="http://www.asha.org/policy" target="_blank">http://www.asha.org/policy</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Beukelman & Mirenda, 2005, p. 97 <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Vinson, Betsy Partin (2001). Essentials for speech-language pathologists. Cengage Learning. pp. 150–51. ISBN 978-0-7693-0071-9. <a href="978-0-7693-0071-9" target="_blank">978-0-7693-0071-9</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Beukelman & Mirenda, 2005, p. 97 <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Vinson, Betsy Partin (2001). Essentials for speech-language pathologists. Cengage Learning. pp. 150–51. ISBN 978-0-7693-0071-9. <a href="978-0-7693-0071-9" target="_blank">978-0-7693-0071-9</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Beukelman & Mirenda, 2005, p. 98 <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Vinson, Betsy Partin (2001). Essentials for speech-language pathologists. Cengage Learning. pp. 150–51. ISBN 978-0-7693-0071-9. <a href="978-0-7693-0071-9" target="_blank">978-0-7693-0071-9</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Beukelman & Mirenda, 2005, p. 98 <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Vinson, Betsy Partin (2001). Essentials for speech-language pathologists. Cengage Learning. pp. 150–51. ISBN 978-0-7693-0071-9. <a href="978-0-7693-0071-9" target="_blank">978-0-7693-0071-9</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Beukelman & Mirenda, 2005, p. 100 <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Hedman, Glenn (1990). Rehabilitation Technology. Routledge. pp. 100–01. ISBN 978-1-56024-033-4. <a href="978-1-56024-033-4" target="_blank">978-1-56024-033-4</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Radomski, Mary Vining & Trombly Latham, Catherine A. (2007). Occupational therapy for physical dysfunction. Lippincott Williams & Wilkins. pp. 524–25. ISBN 978-0-7817-6312-7. <a href="978-0-7817-6312-7" target="_blank">978-0-7817-6312-7</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Hedman, Glenn (1990). Rehabilitation Technology. Routledge. pp. 100–01. ISBN 978-1-56024-033-4. <a href="978-1-56024-033-4" target="_blank">978-1-56024-033-4</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Radomski, Mary Vining & Trombly Latham, Catherine A. (2007). Occupational therapy for physical dysfunction. Lippincott Williams & Wilkins. pp. 524–25. ISBN 978-0-7817-6312-7. <a href="978-0-7817-6312-7" target="_blank">978-0-7817-6312-7</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Beukelman & Mirenda, 2005, p. 101 <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> </ol>