• Audio-Visual

Accent Lighting

  • "Directional lighting to emphasize a particular object or draw attention to a display item." - GE Lighting Glossary
  • While it may contribute to, accent lighting is not intended to provide general service lighting.


  • A type of plastic used in a number of lighting applications but most commonly as lenses. It's level of transmission (how much light it allows to pass through it) is excellent and is excellent at directing light as needed as well.
  • Acrylic does not have good impact resistance and can be quite brittle but is generally weather and UV resistant. It is more expensive than polycarbonate. Acrylic is fairly easy to scratch and cannot handle extreme temperatures or prolonged high temperatures well. Sheets of various styles of "prismatic" acrylic lenses for use mainly in troffer style fixtures.


  • "The process by which the human eye adjusts to a change in light level." - GE Glossary


  • A generic term used to describe anything that goes from one thing to another. Adapters generally do adapt from one version of something to another version of the same thing but that isn't entirely a certainty.
  • The most common types of adapters encountered in the lighting industry are base adapters for use in lampholders and the most common of these are threaded adapters that convert the thread size of a lampholder into which it is screwed in order to accept a bulb with a different size thread.
  • Adapters are always stated as [base being adapted from (bottom of adapter)] to [base being adapted to (top of adapter)].

    Image: • 1 mogul (E39) to medium (E26) 00910A • 2 medium (E26) to mogul (E39) 03472A • 3 medium (E26) to 4 pin CFL (GX24q) 22699A *includes an integral ballast to operate the bulb* • 4 medium (E26) to medium (E26) extender 00886A • 5 medium (E26) to intermediate (E17) 02919A • 6 medium (E26) to euro bayonet (B22d) 32821A • 7 medium (E26) to GU24 twist lock 30942A • 8 candelabra (E12) to intermediate (E17) 25873A, • 9 European Candelabra (E14) to candelabra (E12) 06675A • 10intermediate (E17) to candelabra (E12) 03182B • 11 candelabra (E12) to medium (E26) 27922A • 12 GU24 twist lock to medium (E26).

Air Leak

  • A compromised spot on a bulb's envelope resulting in "air" entering the envelope. Common reasons for this include physical shock or rapid temperature change. Because many bulbs maintain a vacuum within their envelope even very small fractures can have quick effects. This term is really only used when referring to bulbs that will be harmed by the presence of air and, in most cases, oxygen specifically. In incandescent bulbs for example the presence of oxygen, even in small amounts, will result in severely shortened life due to oxidation of the tungsten filament (See animation below) while in high intensity discharge bulbs, having air inside the envelope can result in air (convectional) currents which can cause temperature differentials that can harm the arc tube and/or cause affect performance.

Alternating Current

  • Abbreviated as "AC". This describes an electrical system in which the polarity (i.e. positive + /negative - ) reverses itself at a particular frequency which is measured in hertz. In North America alternating current alternates at a rate of 60Hz whereas in the majority of the rest of the world it is 50Hz. See World Voltages for info for other countries. Image: a visual representation of alternating current. Click the image to open animation.

Aluminized Reflector

  • A parabolic surface that has been made a reflector by being coated with vaporized aluminum. Examples would be R shaped bulbs as well as parabolic aluminized reflectors (PAR).
  • In the manufacture of PAR bulbs, small tabs of aluminum are placed on a small plate and then the open glass surface is placed face down over the plate. Using a powerful electric charge the aluminum tab is vaporized and then electrostatically drawn to the reflector's surface where it bonds, thereby creating a reflective surface.
  • In R shaped bulbs and mirrored bulbs the entire inner surface is coated with reflective material and then is partially filled with acid that eats away a portion of the reflective material to create the clear portion. The acid is then neutralized, drained and then washed out.
  • Image: R20 clear (left), PAR38 (middle), G25 mirrored (right)


  • A metal that has a fair electrical and thermal conductivity often used as a lower cost alternative to copper or even brass. Because pure aluminum is highly reactive when exposed to air, aluminum alloys are used but even many aluminum alloys will corrode over time when exposed to air and water.
  • To keep costs down, the most common incandescent bulbs have traditionally used aluminum bases instead of brass. In spite of the very short lifetimes of these mainstream bulbs their bases still corroded often when used outdoors or when used almost anywhere in humid environments. Significant corrosion can cause a base to seize inside its lampholder so that when the bulb is twisted in an attempt to remove it its base will separate from its shell.
    Image: Aluminum base (left), corroded aluminum base (2nd from left), separated aluminum base seized in lampholder (3rd from left), brass base (right).
  • See Ballast > Wire for more information on aluminum wire.
  • Aluminum has an acceptable reflectivity and thus has been used for decades as a reflective material in light bulbs. See Aluminized Reflector

Ambient Lighting

"The general lighting present in an area--excluding task lighting and accent lighting but including general lighting and daylight streaming in." - GE Lighting Glossary

Ambient Noise (Sound)

"'Background noise' generated by ballasts and other equipment operating in a building. Low ambient sound levels are desirable for hospitals, libraries and similar applications where high noise levels are unacceptable." - Advance Ballast Glossary

Ambient Temperature

"The surrounding temperature within an environment." - GE Lighting Glossary

American National Standards Institute (ANSI)

  • Abbreviated as "ANSI". A standards organization that creates and maintains standards for a number of electrical systems including but not limited to lighting systems.
  • HID Codes
    • A common spoken use of "ANSI" in the lighting industry is in reference to the "ANSI code" of a HID bulb or ballast. For a detailed list of ANSI codes reference this document: ANSI Ballast Codes. Below is a quick list of basic designations.
      Technology Type
      ANSI Designation
      High Pressure Sodium
      400W = S51
      Low Pressure Sodium
      180W = L74
      Mercury Vapor
      175W = H39
      Metal Halide
      50W = M59
      Metal Halide bulbs have a further suffix attached of "/O" (Open Rated, Example: M59/O) or "/E" (Enclosed Rated, Example; M59/E).


  • The common shortened version of Ampere. Abbreviated as "A".
    The current flow through an electrical system with a power factor of 1.0 is calculated as: Amps = Watts over Volts


The current carrying capacity of a conductor such as wire.

See Ballast Wire.


The standard unit of measurement for electrical current.

See Amp.


"The "positive" terminal of a diode." - GE Lighting Glossary


  • The codes assigned to various photo/studio/projection bulbs to identify bulbs from different manufacturers as being interchangeable. Examples:
    BTR 1000 WATT 120V T-7
    EXR 300 WATT 82V MR13
    FFR 1000 WATT 120V PAR-64


An opening, usually in a recessed luminaire, through which light enters a space.


"Also called "lighting application," it refers to the particular use for a lamp (e.g., high-bay industrial application or retail lighting application.) The term can also refer in a general way to "application engineering" which deals with specific parameters and usage of light sources (e.g., how to do a lighting layout, where to place fixtures and so on)." - GE Lighting Glossary.


  • Bright visible effect caused by the passage of electricity across a gap between terminals. Often used to refer to the arc that is struck within a high intensity discharge bulb's arc tube.
  • The arc of electricity that occurs between the pin of a fluorescent bulb and the contact in a fluorescent socket. This can lead to bulb failure, ballast failure, socket failure and fire. When this occurs there is generally a 'sizzling' sound.

Arcing of Output Leads

"Generation of an electrical arc between the output leads of a ballast. May deactivate conventional electronic ballasts." - Advance Ballast Glossary


A member of the noble gas family of elements which includes helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and element 118 (temporarily named ununoctium [Uuo]). The members of the noble gas family are known for their reluctance to undergo chemical reaction and are thus excellent for use in applications where oxidation is a concern such as inside of a light source.

Average Life Hours

  • Also often referred to as "Average Rated Life". Neither "Average Life" nor "Average Life Hours" are commonly abbreviated in any form. The point at which 50% of a representative sampling of a particular product has ceased to operate. Most commonly the Average Life of a product is measured in hours.

    An overly simplified example: 100 pieces of a particular item are installed and begin operating. The item's Average Life is the amount of operational time that must pass before a total of 50 of the original 100 pieces cease to operate.
  • The federal government's accepted definition is: "(P) The terms 'life' and 'lifetime' mean length of operating time of a statistically large group of lamps between first use and failure of 50 percent of the group in accordance with test procedures described in the IES Lighting Handbook-Reference Volume." - PUBLIC LAW 102-486
  • Here are common ranges of Average Life Hours for various item classes:
    750 - 2,000
    2,000 - 4,000
    10,000 - 40,000
    7,500 - 36,000
    Compact Fluorescent

      10,000 - 20,000
      8,000 - 10,000
    25,000 - 50,000

Average Lumens

  • The average of the measured lumen output of a representative sampling of a particular light source.