where L(T) is the total luminance (image plus background) and
L(B) is the luminance of the background portion. Contrast ratio defined as
L(T) / L(B) and is one more than the contrast.
3.7 Design eye line. The design eye line is a segment
of the over the nose vision line connecting two points which represents the
predicted eye positions of the extremes of the aircrew population.
3.8 Design eye position. The design eye position is the
midpoint of the design eye line from which all crewstation dimensions are
related and referenced.
3.9 Display. A device which presents information to one
or more aircrew members via one or more of the senses.
3.9.1 Dedicated alert display. A display whose sole
purpose is to present alert signals.
3.9.2 Integrated display. A display which can operate
in several modes or functions, one of which is the presentation of alert
3.9.3 Transilluminated display. A display in which
the light passes from behind the display surface through translucent
3.10 Flag. A visual mechanical or electromechanical
device used to show a change in the status of an indicator, instrument, or
its associated system.
3.11 Indicator. A display device, usually mechanical or
electromechanical, which indicates discrete conditions or status of a
3.12 Tactial signal. A signal which is felt rather than
seen or heard.
3.13 Visual signal. A signal which is seen rather than
heard or felt.
3.13.1 Advisory signal. A visual signal which
indicates a safe or normal configuration, condition of performance or
operation of essential equipment, or attracts attention and imparts
information for routine action purposes.
3.13.2 Annunciator assembly. A grouped assembly of
two or more warning, caution, or advisory legend signals arranged
categorically or functionally.
3.13.3 Caution signal. A visual signal which
indicates the existence of a condition requiring immediate attention but
not immediate action.
3.13.4 Legend signal. A visual signal containing
alphanumeric characters or symbols.
3.13.5 Master caution signal. A visual signal which
indicates that one or more caution signals have been energized.
3.13.6 Master warning signal. A visual signal which
indicates that one or more warning signals have been energized.
3.13.7 Nonlegend signal. A visual signal which has no
alphanumeric characters or signals arranged categorically or
3.13.8 Warning signal. A visual signal which
indicates the existence of a hazardous condition requiring immediate
action to prevent loss of life, equipment damage, or abortion of the