By Sarah Horton and David Sloan — Assistive technologies that support user accessibility needs relating to operating a user interface include both hardware and software solutions. Alternative input devices are hardware devices with supporting software that together perform a similar role to a standard mouse and keyboard but do not rely on fine manual dexterity for operation. Some alternative input devices work in combination with a dedicated on‑screen keyboard to support more efficient input. Some alternative input device options are built into standard operating system accessibility settings, making use of the device’s camera or microphone. External keyboards can be wirelessly connected to touchscreen devices such as smartphones, tablets, and kiosks, allowing keyboard operation instead of touch.
Switch Controls
A switch device is a general term for any device that has a limited set of states and can be operated in different ways. For example, sip‑and‑puff devices act as a switch controlled by the mouth. Other switch devices may be operated by a hand or foot or by moving the head. On screen, the switch device may allow a user to choose between moving focus from one control to another or activating the currently focused control. Alternatively, focus may move automatically in a logical, slow progression through the interface.
Gestures and Movements
Gesture recognition devices involve body‑worn sensors that allow specific movements to be interpreted as input actions. Gaze recognition uses a camera to detect gaze direction and manipulate the mouse pointer accordingly. A head wand is a hardware device attached to a headband, allowing someone to use the wand to press keys by moving their head.
Speech
Speech recognition allows a user to issue verbal commands to control the interface, allowing navigation, operation, and data input without needing to use a keyboard or mouse. In recent years, the quality of speech input software has significantly improved, including greater tolerance for speech of diverse accents and volumes. It’s important to distinguish between two distinct categories of speech input software, with the first one being more accurately described as an assistive technology supporting user operation of an interface:
- Dedicated speech input software intended to enable a user to operate a user interface by, for example, selecting a specific hyperlink and activating it. This software typically responds to a set of specific, terse commands.
- Voice assistance software, such as Apple’s Siri or Microsoft’s Cortana, whose primary purpose is to answer questions expressed in a more natural language by interrogating large repositories of data.
Input Modifications
Some user accessibility needs may be supported through hardware or software adaptations to standard input methods. These can help accommodate tremors and other conditions that affect fine motor control, as well as reduce the physical effort required to operate an input device. Hardware modifications focus on adjusting hardware design to reduce the physical strain of operation, for example, through ergonomic keyboards, trackballs, and joysticks.
Some software modifications focus on adapting the signals received from a hardware input device to make operation easier and reduce input errors, such as adjusting the click rate of a mouse button and touchscreen sensitivity to account for involuntary clicks and taps.
Other software modifications focus on adjusting the visual display of the pointer, keyboard focus, or cursor to help meet user accessibility needs relating to vision and motor control. For example, operating system and software features allow users to customize the size and appearance of the mouse pointer or cursor, including adding a trailing animation when the pointer is moved.
Most alternative input solutions operate as input devices in the same way as using the TAB and ENTER keys on a standard keyboard, where TAB supports linear progression through each user interface element in turn and ENTER activates the currently focused element. This means that designing a digital product that can be navigated and operated by a keyboard increases the chances that the product can also be operated using alternative input methods.
From Horton, S., & Sloan, D. (2024). What Every Engineer Should Know About Digital Accessibility. CRC Press, Boca Raton, Florida.
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