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GLOSSARY
Saturation
Attribute of visual sensation that permits a judgment to be made of the
proportion of pure chromatic color in the total sensation.
Service
illuminance
Mean illuminance during one maintenance cycle of an installation averaged
over the relevant area.
Specular
reflector
That part of a luminaire designed to reflect the luminous flux of the
lamps in required directions by means of specular reflection
Spotlight
A (small) projector giving concentrated light of usually not more than
20° divergence.
Spread
Quantity of a luminaire to indicate the extent to which the light is 'spread
out' across the road. Luminaires are classified as being of narrow, average
or broad spread.
Starter
Device for starting a discharge lamp (in particular a fluorescent lamp)
that provides for the necessary preheating of the electrodes and/or causes
a voltage surge in combination with the series ballast.
Starting
device
Electrical apparatus that provides the conditions required for starting
a discharge.
Switch-start
fluorescent lamp
Fluorescent lamp suitable for operation with a circuit requiring a starter
for the preheating of the electrodes, for example 'TL'D type.
Tubular
fluorescent lamp
Gas-filled lamp containing halogens or halogen compounds, the filament
being of tungsten.
Ultraviolet
radiation
Optical radiation for which the wavelengths are shorter than those for
visible radiation.
Upper
[lower] (luminous) flux
Of a source. The luminous flux emitted above [below] a horizontal plane
passing through the source.
Note
It is essential that the plane be specified in every case.
Upward
[downward] light output ratio (luminaire efficiency)
The ratio of the flux emitted above [below] a horizontal plane passing
through the luminaire to the total bare lamp flux.
Utilisation
factor
Ratio of the utilized flux to the luminous flux emitted by the lamps.
Vapor-tight
luminaire
Luminaire so constructed that a specified vapor or gas cannot enter its
enclosure.
Visual
comfort
The degree of visual satisfaction produced by the visual environment.
Visual
guidance
The totality of measures taken to give a road user an unambiguous and
immediately recognizable picture of the course of the road ahead.
Visual
performance
The quantitative assessment of the visual system in the performance of
a visual task.
Watertight
luminaire
Luminaire constructed to withstand the penetration of water when immersed
to a specified depth, but not intended for permanent use under water.
Note
The term 'submersible luminaire' applies to a luminaire constructed to
withstand indefinitely submersion in water to a specified depth.
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