NAME
Warning Signal — Reference
Description
A warning signal is a transient cue that alerts the user about
a minor, nonfatal error or problem with interaction. A warning signal
may be an audible signal (such as a beep) or a visible signal (such
as a flashing screen) or both. A warning signal may also be other
transient, sensory signals that the operating environment supports.
The warning signal should use as many modes as needed to supplement
other on-screen cues. For example, if the user is in a low-light
environment, an audible signal can be a useful supplement to other
visible on-screen messages and graphical cues.
When to Use
- Required
Provide a warning signal when the user types a character
that is not supported as input for a text-entry field that has focus.
For example, if a text-entry field supports only numeric characters,
provide a warning signal when the user types a letter.
- Required
Provide a warning signal when the user types a character
that cannot be used as a mnemonic at the active cursor position
or the control on which the cursor is positioned does not accept
text input. For example, if mnemonics are supported but no choice
has L assigned as the mnemonic, provide a warning signal when the
user presses the L key.
- Required
Use a warning signal to supplement a message. Note
that in degraded environments, a message may occur in sensory modalities
other than the standard visual on-screen mode. See Chapter
12 for more information.
- Recommended
Provide a warning signal when a user attempts to
activate a choice or interact with a control that is displayed with
unavailable emphasis.
- Recommended
Provide a warning signal to supplement a persistent
cue that might otherwise be ignored by the user, or if the cue is
intended to alert the user, or if the situation is urgent.
Guidelines
- Required
If the user has turned off a warning signal option
for the operating environment and a situation arises in which the
system would normally generate that warning signal, do not generate
a warning signal. For example, if the user has turned off audible
signals for the operating environment, do not generate an audible
signal when an action message is displayed.
- Recommended
Allow the user to take advantage of various capabilities
of hardware and software. For example, if the operating environment
supports the generation of a variety of sounds, allow the user to
specify different sounds for a warning message, an action message,
and for an attempt to activate a choice currently displayed with
unavailable emphasis.
- Recommended
Even if the operating environment allows an unlimited
range of warning signals in any sensory modality, assign meaning
to only a limited number of signals. Generally, your application
should support no more than seven different audible signals and
about five different visible signals.
- Recommended
If a warning signal is the only indication of a
condition and the environment is degraded such that a warning signal
cannot be used effectively, use a warning message instead.
Essential Related Topics
For more information, see Chapter 4
and the Action Message,
Message, and Persistent Cue reference
pages.
Supplemental Related Topics
For more information, see the Information and Message Areas (Area)
and Mnemonic reference
pages.
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