Switches

Technology which can help people with disabilities use the web

How switches are used as an assistive technology for web users.

Many intellectually disabled (ID) web users with more severe or profound disability are likely to access computers via switches, even in the absence of significant physical impairments.

The majority of switch users without ID use switches via assistive software to provide sophisticated means of keyboard or mouse emulation. For these users, predictive text and dynamic scanning grids allow an efficient means of entering text or controlling applications using standard keyboard controls and shortcuts.

From the developer's perspective, such switch users can be effectively included online, providing attention is given to WCAG 2.0 guidelines, particularly in respect of keyboard operability.

Ball switch

Single switch

Using switches

Switch users with ID are less likely to be using accessibility middleware. Custom controls accepting keypresses directly will often be required if users with severe and profound disabilities are to be supported by an application.

Most switches used by this group are connected to the computer via a simple interface which allows the keypresses sent by switches to be selected, but a good default choices would be '1' and '2'.

Sometimes users may map two switches to 'tab' and 'enter' as a means of navigating web pages generically.

Single switch users rely on the application they are using, or accessibility middleware, to move focus automatically. In a web page context this would be like pressing the 'tab' key automatically after a set delay, leaving the user to press 'enter' when the desired item has focus.

A more able user may be able to undertake more complex and efficient operations via single switch, for instance narrowing a number of group selections to a single item, rather than stepping through a large number of items individually.

Even if switch users are not targeted or provided with custom controls, consideration should be given with respect to difficulties certain common practices present to switch users.

A single switch user accessing a page with a two second scan delay for instance could take one minute to arrive at the 30th link on a page. Use of prominent in page navigation therefore can be an essential aid to switch users, rather than simply a usability convenience.

The increasing trend to employ off page positioning for in-page navigation, without focused items to view, effectively prevents their use by many users. Likewise using text links without graphical annotation for in page navigation is likely to exclude many ID users accessing a page via switches.

Resources

  • SAW5 was a free Windows application from which simple and complex switch scanning grids could be created. Sample grids for common browsers were included.

  • HotSpots 2.0 provided a free and simple means of retrofitting switch accessibility to web applications without the need for custom controls to be scripted. This application was used to define a sequence of absolute (screen) positions for progression by switch. Ensuring a fixed screen resolution is defined and the requesting browsers are run full screen, allows a measure of consistency to be assumed between different users.