Glossary

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DTMF(also: Dual-Tone Multi-Frequency, Touch-Tone)

DTMF (Dual-Tone Multi-Frequency) is the signaling system used when pressing keys on a telephone keypad, where each key press generates a unique combination of two audio frequencies. In accessibility contexts, DTMF input serves as an alternative interaction method for voice-based…

Dead Time(also: Wait Time, Idle Time)

In scanning-based assistive technology interfaces, the period during which a user must passively wait before they can make their next input action. In row-column scanning, dead time occurs while waiting for the desired row or column to be highlighted. Longer dead times reduce…

Debounce(also: Debounce Filter, Key Debounce, Bounce Key Filter)

A keyboard accessibility feature that filters out unintended extra keypresses caused by tremor or imprecise motor control. When enabled, the system ignores rapid successive activations of the same key within a specified time window, treating them as a single press. Debounce is…

Deformable Input(also: Flexible Input Surface)

An input method that uses physically flexible or pressure-sensitive surfaces that can be bent, squeezed, twisted, or otherwise deformed to generate control signals. Deformable input devices can provide accessible interaction for users with motor impairments, as they may require…

Digital Crown(also: Watch Crown, Rotary Input)

A physical rotary input control on the Apple Watch and some other smartwatches that can be turned to scroll, navigate, or adjust values. The digital crown provides tactile, proportional input that does not require looking at a screen, making it valuable for accessibility…

Direction-Based Navigation(also: Directional Navigation, Direction-Based Cursor Control)

A cursor control method where users issue directional commands such as "move left," "move up," or "move down" to reposition the cursor on screen. In speech-based implementations, these commands move the cursor continuously or in fixed increments. Direction-based navigation is…

Disambiguation(also: Target Disambiguation, Touch Disambiguation)

In accessible interface design, disambiguation is the process of resolving ambiguity when a user's input could correspond to more than one interactive target. This commonly occurs on touchscreens where small, densely packed elements make precise selection difficult, particularly…

Drag and Drop(also: DnD)

An interaction pattern in which users select an on-screen object by pressing and holding, then move it to a new location before releasing. Drag and drop is widely used in visual programming environments, file management, and content editing. It presents significant accessibility…

Dwell Activation(also: Dwell Click, Dwell Selection)

An input method where an action is triggered by maintaining focus on a target for a specified period of time (the dwell time). Commonly used with eye tracking and head tracking systems, dwell activation allows users to select items without needing to physically click. While…

Dwell Control(also: Dwell Click, Dwell Selection, Dwell-Time Activation)

An input method in which a user activates a target — such as a button, link, or key — by holding a pointer or gaze over it for a specified period of time rather than clicking or tapping. Dwell control is essential for users who interact via head tracking, eye tracking, or other…

Dwell Selection(also: Dwell Click, Dwell Time Selection, Hover Click)

An interaction technique where a user activates or selects an on-screen element by keeping a cursor, gaze point, or pointer within the target area for a specified duration (the dwell time), rather than clicking or tapping. Dwell selection is essential for people with motor…

Dwell Time(also: Gaze Dwell, Fixation Duration)

The length of time a user must maintain their gaze on a target element to trigger a selection in eye gaze technology systems. Dwell time is a critical parameter in gaze-based interfaces: too short and users make unintended selections (the "Midas touch" problem), too long and…

Dynamic Keyboard(also: Adaptive Keyboard, Self-Adjusting Keyboard)

An assistive technology concept in which a keyboard automatically adjusts its input parameters — such as key repeat rate, debounce time, and acceptance delay — based on the user's typing patterns and abilities. Dynamic keyboards were developed to reduce common typing errors…

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