Overview of Digital Accessibility Technologies

There are a great number of tools and devices out there designed to improve computer use for people with disabilities or even make computer use possible at all. We can consider them in two broad categories, input and output. Input methods send data provided by a user to a device, while output methods send information provided by a device to a user.

This is a non-exhaustive list of these technologies for reference. Though I have attempted to be relatively comprehensive in covering usage, accessibility often necessitates varied usage and unique assembly of technologies, such that this post does not and will not cover every case.

Screen Readers

A screen reader is an output method that audibly relays the content on a screen via non-visual methods. In addition to reading text and content that is directly upon a screen, a screen reader also often conveys semantic meaning. For example, though the word ‘navigation’ may not be displayed visually, if a section is designated as ‘navigation’, a screen reader might convey that. Screen readers are extremely configurable, like many other accessibility tools, and are commonly modified for specific user needs. Often, synthetic speech output from screen readers will be at such a pace that it cannot be comprehended by people unacquainted.

They are most commonly associated with people with visual disabilities, though are also used in many cases by people who are illiterate or have learning disabilities.

Screen Magnifiers

Screen magnifiers are an output technology which enlarge sections of a display for easier viewing. This can be achieved in technology with often toggleable enlargement of specific screen sections or with physical magnifying lenses.

Most commonly, screen magnifiers are used by people with visual impairments that are significant enough to impact computer use but which don’t necessitate a screen reader. Magnifiers are, however, also used by people who lack fine motor control and thus need enlarged inputs.

Braille Displays

Electronic braille displays, also known as refreshable braille displays or braille terminals, are dynamic braille output interfaces. Braille is a tactile writing system where characters are represented as embossed dots on a 3x2 grid known as a ‘braille cell’. Different characters have different dots within the cell embossed and in different arrangements, such that a person with a visual impairment can identify a character by feeling it with their finger.

Electronic braille displays take output from a computer and mechanically displace a surface into braille cells for the user to read. On most devices the braille is displayed in a single strip between 40 and 80 cells wide, though for mobile readers it can be narrower. Depending on the device, the current cursor location might be indicated by the dots vibrating or additional dots above or below the cell. These displays are often used for the same purpose as speech synthesisers, and sometimes both tools are used by the same individuals who switch between them depending on circumstance. Braille displays are especially valuable for people who are both deaf and blind.

Sip-and-Puff

Sip-and-puff (SNP) is an input method which sends signals based on air pressure. The user sips (inhales) or puffs (exhales) on a device with their mouth to regulate this air pressure. The device is commonly worn as a headset, but it can also be mounted directly to a surface such as a wheelchair or table. Different inputs are achieved via sips and puffs of different strengths, which are calibrated based on the individual user. These strengths are often referred to as ‘hard’ and ‘soft’.

Most users of sip-and-puff machines have severely reduced motor function.

Gyroscopic Head Mice

Often worn as an earpiece or glasses, a gyroscopic head mouse is an input device which uses head motion. Depending on the level of motor control one has, it can be used to directly control an on-screen pointer akin to a mouse, or it can be used for directional input. A tilting of the head right to indicate a right input, and so forth. It can also be used in a method more akin to a joystick, which is sometimes taken advantage of for gaming.

Mouth and Tongue Joysticks

Positioned close to the mouth, similar to a sip-and-puff, mouth and tongue joysticks are input devices which rely on oral control of a joystick. A sip-and-puff machine is often integrated into the joystick for further input controls.

In progressively-onset motor diseases, the mouth is often one of the last external body parts one retains control of. If the option for a joystick of this nature is available, people often find them especially desirable for motorised wheelchair movement.

Chording Keyboard

A chording keyboard is an input device which involves pressing down multiple keys simultaneously to create a ‘chord’. Different combinations of keys trigger different inputs based on a user’s pre-defined dictionary. If you’ve ever wondered how court room stenographers type so fast, it is because stenography is a chording input method.

Due to minimal reaching or stretching, and the reduced number of keys needed for a chording keyboard, it can be advantageous for someone with wrist or arm problems. The combinations also allow for configurations where only one hand is needed for input, which allows more effective input for people with only a single arm.

Switch Control Devices

Switch control devices are input devices which send single binary inputs. Commonly, they’re large buttons which are placed within the range of motion of someone with limited motor control, such that they can press them when needed. The exact placement depends on the individual case and what movement is possible. Sensitive microswitches can also be used and attached in specific locations such that they can pick up tiny movements like twitching a muscle or blinking. Typically, a device configured for someone using switch control devices will cycle through input options with the user activating the switch when it highlights their choice. The exact configuration depends on the number of inputs and the fidelity of movement the user is capable of.

Dwell Clicker

A dwell clicker is an input method where hovering in a single place for a chosen period executes an input. It is often used in tandem with other accessibility technologies, such as head-and-mouth sticks and eye trackers, but is also used by people who can operate more common pointer devices like mice but are unable to click.

Head/Mouth Stick

Head sticks and mouth sticks are input devices either attached to one’s head with a harness or held between one’s teeth, respectively. They can be used to interact with touchscreens like one would with a finger or to press physical keys. Trackballs are also often popular, as they can be nudged to move a cursor. Which of these methods is chosen depends on if the user can maintain a bite grip or suffers from jaw fatigue and what is most comfortable for them.

They’re mainly used by people with quadriplegia/tetraplegia.

Expanded Keyboards

Expanded keyboards are input devices which resemble standard keyboards. However, they are designed for easier input by people with reduced motor control. They are physically larger, with significant spaces between keys to give a larger margin of error, and have a physical keyguard. The keyguard sits above the keys, making them recessed, and gives users a place to rest their hand or arm without triggering inputs. It also gives users more control over which key they’re pressing, so one can more deliberately strike a single key through the hole in the keyguard with a finger or a pointer stick attached to one’s head or held in one’s mouth.

Expanded keyboards are used by people with many accessibility considerations. Conditions including cerebral palsy, Parkinson’s disease, multiple sclerosis, or essential tremors can cause unintended tremors and spasms, which the keyboard mitigates by preventing unintended strikes. Typing on a typical keyboard requires one’s hands to rest lightly above keys, so people with muscle weakness who would otherwise accidentally trigger the keys use expanded keyboards for their keyguard. Due to expanded keyboards commonly having large, clearly labelled keys, people with low vision and cognitive disabilities also benefit. As aforementioned, it can also help head-and-mouth stick users.

Eye Gaze

Eye gaze or eye tracking is an input method where a person uses their eyes to navigate a screen. Tracking either one or both eyes, the cursor follows wherever one looks. To make a selection, one must either use dwell control and hold their gaze, blink, or pair eye gaze with another input method, like a sip-and-puff.

Similar to gyroscopic head mice, input is sometimes alternatively done by gestures in a direction, such as looking right to navigate right. Tracking is usually achieved with a specialised infrared eye tracker and is paired with software for configuring and managing control.

Even in cases of total paralysis, control of eyes often remains, which makes eye gaze input one of the last input methods available in many cases.

Foot Pedals and Mice

Foot pedals and mice are input devices which one operates with their feet. A primary and secondary click can be controlled with one’s feet, as well as mouse pointer input, but keyboard input is often considered to require too much fine motor control. Foot control is often very capable, though is often not quite as precise as control with arms.

Immersive Readers

Immersive readers are an enhancing output method that blocks content on a page so that only what the user must see is exposed. For example, on a website, sidebars and navigation systems might be hidden, while only core article content is left undisturbed. Sometimes the user will also change the font in use, adjust the text size, and use a line reader to highlight their current point on the page or obscure everything else.

Immersive readers are commonly used by a wide variety of people but are of particular importance to people with cognitive fatigue, ADHD, autism, and dyslexia.

Speech Input

Speech input is an input method where a user speaks commands at a microphone, which are then processed by a computer and treated as controls. Speech input takes many forms and is very configurable. Depending on configuration, a user might make a hissing sound to scroll or read off text for a button to click it. Often, optical character recognition (OCR) and overlay¹ systems are used so that any item on screen can be referenced with speech. A user also can write text via dictation.

Speech input is commonly used by people with motor problems.

Footnotes

1. I’m not talking about horrid, generic so-called ‘accessibility overlays’ such as those that you see on websites. ↩