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Understanding Assistive Technologies: What Are Sip-and-Puff Systems?

Apr 28, 2023

By understanding how assistive technologies (AT) work, we can gain new perspectives on web accessibility — and avoid some of the mistakes that create barriers for AT users.

Sip-and-puff (or SNP) devices use air pressure to trigger specific commands. They may be useful for people with physical disabilities, but they’re not the only interface available for these users; some people might prefer eye-tracking systems, joysticks, or touchscreens.

SNPs connect to a computer via a wired or wireless connection. The system’s mouthpiece can typically be attached to a headpiece or affixed to the user’s desk or wheelchair. By using their lips to “sip" or “puff" into the mouthpiece, the user activates electronic switches that send signals to the computer. SNP systems can also be used to control other devices such as wheelchairs.

Some SNP systems have multiple switches, while others consist of a single switch. Software interprets the commands, and programs like SwitchX® can be used to emulate a keyboard or mouse. 

The user can configure the software to handle complex interactions. For example, “puffing" air into the interface might scroll to the next focusable element of a webpage, while “sipping" air might activate a hyperlink. When typing, the software can generate a predictive list of words, which the user can scroll through to select the correct option. 

Related: Assistive Technology 101: What You Need to Know

Web Accessibility for Sip-and-Puff Systems

Like many types of AT, sip-and-puff systems are customizable, and many commands are specific to the user’s SNP software or computer operating system.

In other words, SNP systems don’t all work the same way — and two users may have very different configurations. To function predictably with all SNP systems, online content needs to follow certain rules. 

The Web Content Accessibility Guidelines (WCAG) are the international standard for digital accessibility. Content that meets all WCAG Level AA success criteria should work predictably with most types of AT, including sip-and-puff systems. 

Several WCAG success criteria may be especially important for SNP users:

WCAG 2.1 Success Criterion (SC) 2.1.1, “Keyboard.” 

This criterion requires that all functionality of the content is operable through a keyboard without requiring specific timing for individual keystrokes. 

Essentially, you shouldn’t build content that relies on a mouse. Some users may not be able to “point and click,” and if a website or mobile app doesn’t work with a keyboard, it probably won’t work with popular assistive technologies.

WCAG 2.1 SC 1.3.1, “Info and Relationships.”

This criterion requires that “information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text.”

In other words, software should be able to understand the semantic structure of the content. This enables AT users to customize their software to present information in a way that makes sense. 

“Info and Relationships" is also important for individuals who use screen readers, which convert text to audio or braille. Without semantic markup, content becomes much less navigable and perceivable for these people.

WCAG 2.1 SC 2.4.1, “Bypass Blocks.”

“Bypass Blocks" requires a mechanism — usually, a “Skip Navigation" link — for bypassing repetitive elements.

Many people who use AT may want to skip past repeated blocks of content. For example, if a user visits your blog, they may not want to scroll through every focusable item in your header menu before reading the content. 

Dozens of other WCAG criteria can impact people who use sip-and-puff systems. Developers, designers, and content creators can remove accessibility barriers by following WCAG Level AA — and wherever possible, it’s also a good idea to follow the strict Level AAA requirements. 

For more guidance, read: What's The Difference Between WCAG Level A, Level AA, and Level AAA?

Building Better Online Content for People with Disabilities

Following WCAG can improve experiences for every type of user — including those who do not use AT regularly. 

The business case for digital accessibility is extremely strong; if your business needs to improve its search engine optimization (SEO) or attract a wider variety of users, accessibility should be a core part of your strategy. 

With that said, it’s difficult to overstate the importance of WCAG for assistive tech users. If a website isn’t accessible with a keyboard alone — or if it requires users to have a certain type of sensory perception — the website is unusable for a large portion of your audience.

About 1 in 4 U.S. adults live with some form of disability. Every organization has a legal and ethical responsibility to accommodate those users. By following the principles of accessibility, you can provide an improved experience for every potential customer. 

To learn more, download our free eBook: Developing the Accessibility Mindset.

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