Modern personal computers often use operating systems which employ graphical user interfaces. Computer systems offer many possibilities of adapting the user interface with the resident features of the operating system, or by using additional hardware or software (further information at www.tiresias.org). This booklet concentrates on systems where there is less opportunity for the user to modify the user interface, so is much more reliant on the system designer having considered their needs.
Sophisticated user interfaces often appear to have been designed by people who think that all the potential users are like themselves. With greater penetration of systems, such as interactive television and car navigation systems, the users are frequently people who are not experts in the technology - their relevant experience may not be more than using a cash dispenser or a car radio.
Ideally the user should be able to configure the user interface to suit their individual requirements. With systems which will be solely used by one person, this could be done by the initial setup of the hardware or software. It is slightly more difficult when the system is to be used by a number of people. One solution for card-operated terminals is for the card to store the user's preferred interface; there is a European standard (EN 1332-4) for how to code this information.
Learning to use a sophisticated system can be difficult for people who have impaired vision or who are elderly. Instruction books in appropriate media (e.g. large print, audio tape) will help, but often that is insufficient. If an experienced human instructor is not available, then the system should incorporate a learning mode or have a separate teaching pack.
The following pages outline the main features of indirect controls. These are grouped into:
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Keys Numeric keys can cause particular problems for blind people since
there are two common layouts; the addition of a raised dot on the
number 5 button does not help in identifying which layout is being
used. Touchscreens Touchscreens can be difficult to use by a blind person. However it is possible to design the system so that there is spoken output when the finger is over an item on the screen, but activation is only when the finger is withdrawn over an active area. With this arrangement there should be only a small number of well spaced active areas. Buttons Buttons at the side of the screen can be difficult to align with
the text on the display if the user is not looking perpendicular
to the screen. Keypads When space for the control panel is very limited, such as on wearable
systems, it may be necessary to provide a socket by which the device
can be connected to an alternative keypad. Another option would
be an infra-red or radio link such as Bluetooth. Understanding the meaning of icons Icons used on buttons and controls must be easy to understand.
Currently the 'enter' button on most keypads uses a 'return' arrow
which is a left-over from the old style typewriters where this icon
indicated a 'carriage return'. The meaning is not obvious unless
you are old enough to remember moving carriage typewriters. Relative or absolute controls Controls which change the relative, rather than absolute, values often cause problems for people with low vision. |
There are now many control interfaces that require the user to follow a sequence of operations in order to make something work. This often involves the use of remote control devices and the need to look at both the control device and some form of display. Some devices have buttons that have more than one function, some involve time delays or the need to be able to hear an audible response. If no consideration is given to the needs of people with disabilities then even a simple operation sequence can be unworkable and leave people excluded. In the ideal world, systems will automatically learn from the way the user controls a system, and modify the user interface to optimally meet their needs.
Consistent user interface
For the visually impaired user it is essential that they understand the operation of the user interface since they are likely to have less feedback from visual displays than a fully sighted person. An important aspect is the need for a consistent user interface.
It is helpful if the user can pre-set sequences or settings they commonly use, and that these can be selected by a single key press or from a favourites list. On a washing machine, most of the time users will only want three or four settings, but machines seem to be sold on the basis of the maximum number of options available on the front panel.
Menus
The trend is towards selecting items from a menu shown on a visual display. These can be arranged so that each push of a button steps down one item; if speech output is provided, blind people can operate this type of system.
Another arrangement is to use 'soft' keys where the function currently controlled by a key is indicated on a screen. It is more likely for a blind user to get confused with this type of system.
Sub-menus can create further problems since an inexperienced user can often get lost. Scrolling menus are particularly difficult to use by people with low vision.
Major problems occur for many visually impaired persons when they are required to operate a pointer to select or drag items on a screen.
Complexity
If a large number of functions need to be selected, there can be:
(a) a large number of buttons
(b) fewer buttons but each button handling more than one function
(c) selection from menus
A large number of buttons are not inherently difficult to use if they are laid out clearly and grouped logically. However there is not always sufficient space, so multi-function keys are often used. With multi-function keys it is essential that the user can easily reset to the default setting (e.g. by a quick double press of a key).
As people get older, handling more than one task at a time becomes more difficult. For younger people displaying redundant information in more than one modality (e.g. both visually and aurally) is often beneficial, but this is not true for many older people.
Time delays
Controls whose function changes with time pose problems for many visually impaired and older persons. Ideally the user should be able to re-configure the user interface so that the controls operate in a different manner or the time between changes can be extended.
If there is a time delay between operating a control and obtaining feedback that the command has been accepted, users can become confused.
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Remote operation
In the case of television, the screen is typically positioned at 8H whereas optimum viewing is at about 3H (where H is the vertical dimension of the screen). Display clarity This has implications for how much information can be displayed on the screen and still be legible for an older person. For interactive television, users can have problems if the screen appears cluttered. Finding a pointer on a screen can sometimes be difficult for people with low vision; a system to highlight the pointer or caret can be helpful. Contrast and clarity Low contrast and small displays, such as on mobile phones, cause particular problems; synthetic speech may be the only viable solution for visually impaired users. However synthetic speech output has limitations if the information is displayed graphically. Screens and glare If it is not possible to provide a high contrast display and/or speech output, an interface for an external display is highly desirable. This could take the form of a socket or it could be handled by an infra-red or radio link. Sound output Typefaces & legibility
With an identity number as shown on this ticket it can be difficult to distinguish an I from a numeral 1. Integrated design
Smart cards can also help set up special requirements and integrate different controls.
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