Checklist for User Interfaces and Interface Transmission Technologies to Assistive Devices

No significant benefits Minor benefits Major benefits
No significant benefits Minor benefits Major benefits

Displays
Text size should be configurable
Text colour and background colour ahould be configurable
Provision should be made to permit a Braille display or screen reader to be fitted
Publicly accessible equipment should offer alternative display modalities
The text and background colour combination should have high contrast
A clear open typeface, should be used for text
Text should not be placed over a background image or over a patterned background
White or yellow type on black or a dark colour is more legible, provided that the typeface (font), weight and size are suitable. Small type and very bold type tend to blur for some people, reducing legibility
Avoid shades of blue, green and violet for conveying information
Speech output of instructions, as an addition to (and not a replacement for), on-screen instructions, is recommended
There should be no noticeable flicker on the screen
Products should be designed to avoid causing the screen to flicker with a frequency greater than 2 Hz and lower than 55 Hz
Use no more than five colours when coding information
Adhere to existing colour conventions e.g. red for stop
Structure the visual display layout so that the user can predict where to find required information and how to use it

Touchscreens
The text and background colour combination is of high contrast
Use of blue, green and violet is kept to a minimum
There is no noticeable flicker on the screen
The structure of the visual display allows the user to predict where to find information and how to use it
Touch sensitive areas or keys are between 20 - 22mm across*
For mobile devices with touchscreens targets are 9.2 - 9.6mm across**
There is a high contrast between touch areas, text and background colour
Text or controls are not placed over a background image or a patterned background
White or yellow type on a black or dark colour background is used
Controls are labelled in a large high contrast font

Audio Output
Inductive coupling facilities should be made available in public terminals and on fixed telephones
Provision should be made to permit a device, such as a flashing light ringer, to be connected
Standard 3.5mm connectors should be used
The user must be able to increase the volume of the audio signal (preferably to at least 90 dB SPL)
Provide text versions of audio prompts that are synchronised with the audio so that the timing is the same
Signals from the basic system, such as alarms, warnings, status lamps and error messages are available in alternative forms
The volume can be reset to a default level
Warnings and similar alert messages must remain stable for a sufficiently long time to be discovered by the user

Icons / Graphics
Symbols should create the illusion of manipulatable objects, e.g., it should be clear that they can be selected, how to select them and be obvious when they are selected
Graphical symbols should be constructed with not more than 2 or 3 components
Symbols should always be presented upright
The symbol stands out from the background
Ensure that each icon is distinct from, and clearly visible within, a surrounding group of symbols
Try to make each symbol as distinct from the others as possible
Symbols should be designed according to a grid, or a basic pattern
Angles smaller than 30° as well as filled areas are avoided

Keyboards / Keypads
All commands and options can be accessed by using the keyboard
The keyboard should be detachable and have a sufficiently long cable, so it can be placed according to user's needs
The keyboard is of low-profile type, i.e. the height of the key-row beginning A-S should not be greater than 30mm
There is good friction between the keyboard and the desktop
The key tops are matt
The surface of the keytops is concave
The user receives tactile and audible feedback when pressing a key
Groups of keys are separated by distinct spaces
Groups of keys are distinguished by different colours
The F, J and 5 keys are marked with a tactile identification
Frequently used keys, such as Enter, Shift, Escape, Ctrl, Backspace etc. have a shape that differs from other keys
There is high contrast between the colour of the character and the background of the keytop
The height of the characters is not less than 4mm
The text on the keys should be printed in sans-serif font
Text is not printed in red or green
The user can customise the keyboard with respect to features such as repeat rate, key activation delay, delay between acceptance of two consecutive key presses, minimum time for pressing a key before the key repeat begins, and serial instead of multiple simultaneous keystrokes etc.
If key repeat is supported, the delay before repeat should be adjustable to at least 2 seconds per character
If sufficient space is available, shift keys (upper and lower case, ctrl, alt etc.) should be duplicated, one on each side of the keyboard, and be placed symmetrically
The system allows the connection of two keyboards, which could be used simultaneously
The power to press a key should be between 0.3 and 0.6 Newton***

Pointing devices
The user can execute pointing functions from the keyboard
The user can modify cursor speed, distance and double-click interval
Operation of a pointing device does not require two simultaneous hand movements
The power needed to operate a pointing device should be between 0.3 and 0.6 Newton***

*According to Namahn (2000), touch sensitive areas or keys, for users with no impairments, should be of a "minimal size: 22mm across". However, Colle & Hiszem (2004) recommend that a "key size no smaller than 20mm...should be used if sufficient space is available". See Touchscreens guideline for references.

**According to Parhi, Karlson and Bederson (2006), for one-handed thumb use of mobile handheld devices equipped with a touch-sensitive screen "target size of 9.2mm for discrete tasks and targets of 9.6mm for serial tasks should be sufficiently large...without degrading performance and preference". See Touchscreens guideline for references.

***According to the Nordic Cooperation on Disability (1998) the power to press a key should be "between 0.3 and 0.6 Newton". See Computer Hardware guideline for references.

Checklist for Displays
Checklist for Keys
Checklist for Pictograms, Icons and Symbols
Checklist for Pointing Devices
Checklist for Touchscreens

Back to User Interfaces and Interface Transmission Technologies to Assistive Devices