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Ampere (amp): The base unit of electrical current that is equal to a constant current.

Average Rated Life: An average rating, in hours, indicating when 50% of a group of lamps have failed when operated at nominal lamp voltage and current. Manufacturers use 3 hours per start for fluorescent lamps and 10 hours per start for HID (High Intensity Discharge) lamps when performing lamp life testing procedures. Every lamp type has a unique mortality curve that depicts its average rated life.

Baffles (Fixture): A mechanism that regulates the flow of light in a fixture.

Base: Metal contact on the lamp that connects to a socket or power source.

Ballast: A device used with an electric-discharge lamp to obtain the necessary circuit conditions (voltage, current, and waveform) for starting and operating; all fluorescent and HID light sources require a ballast for proper operation.

Ballast Hum: A sound generated by the vibration of laminations in the electromagnetic field that transforms the current for discharge lamp use.

Brightness: The attribute of light-source colors by which emitted lights ordered continuously from light to dark in correlation with intensity.

Burning Position: The position in which a lamp is designed to operate for maximum performance & safety.

  • BD - Base Down (bulb is vertically positioned with the metal base at the bottom, glass up)
  • BU - Base Up (bulb is vertically positioned with the metal base at the top, glass hanging down)
  • HBU - Base Up +/- 90° (bulb can be operated in a base up or horizontal position)
  • HOR - Horizontal Burn (bulb is positioned with the metal base parallel to the ground)
  • U - Universal Burn (bulb can be operated in any position)

Candlepower: Luminous intensity expressed in candelas.

Color Rendering Index (CRI): Color rendering is the ability of a light source to produce color in objects. The CRI is expressed on a scale of 0-100, where 100 is the best in producing vibrant color.

Color Temperature: Originally, a term used to describe the "whiteness" of incandescent lamp light. Color temperature is directly related to the physical temperature of the filament in incandescent lamps, so the Kelvin (K) (absolute) temperature scale is used to describe it. Although it may not seem sensible, a higher color temperature (K) describes a visually cooler, bluer light source. More recently, the term "chromaticity" has been used in place of color temperature.

Cool White: Reference to the color tone or appearance of light produced by a lamp for a specific color temperature. Cool White is the least expensive and most widely used fluorescent lamp color in lighting today. Its name comes from the cool, airy atmosphere it creates wherever it is used. Modern, efficient and business-like, it is popular in stores, classrooms, offices, corridors and factories.

Correlated Color Temperature (CCT): A term used for discharge lamps, where no hot filament is involved, to indicate that the light appears "as if" the discharge lamp is operating at a given color temperature. CCT generally measures the "warmth" or "coolness" of light source appearance using Kelvin(K) temperature scale.

Compact Fluorescent Lamp (CFL): A fluorescent type bulb that has the ability to be utilized in an incandescent fixture, and still maintain the efficiency and qualities of a standard fluorescent bulb. These bulbs generally offer 75% savings in electricity while maintaining comparable light levels.

CRI: Color rendering index.

Daylight: Reference to the color tone or appearance of light produced by a lamp for a specific color temperature. The bluish white appearance of this lamp is similar to natural daylight. 5000-6500K*.

Dimmable: A lamp that maintains reliability when varying its lumens.

Economic Life: The number of hours a group of lamps will burn before it is economically and aesthetically advisable to group relamp (typically 60% to 75% of rated life).

Efficacy: Efficiency of a light source expressed in lumens per watt (LPW or lm/W).

Enclosed Fixtures: Fixtures which have a lens that protects the bulb from the elements.

Energy: A measure of work done by an electrical system over a given period of time, often expressed in kilowatt-hours (kWh).

Filament: Tungsten wire positioned inside a bulb which generates light when heated.

Fluorescent Lamp: A high efficiency lamp utilizing an electric discharge through low pressure mercury vapor to produce ultra-violet (UV) energy. The UV excites phosphor materials applied as a thin layer on the inside of a glass tube which makes up the structure of the lamp. The phosphors transform the UV to visible light.

Foot-candle (): A unit of illuminance or light falling onto a surface. One foot-candle is equal to 1 lumen per square foot.

Frost: The glass of the lamp has a slightly opaque white appearance.

Four-Pin Compact Fluorescent Lamps: Type of lamps that do not have any starter built inot the base of the lamp. Therefore, the ballast has the starting circuit. Traditionally, 4-pin lamps are designed to work with electronic ballasts.

Full Spectrum: A bulb that reproduces the full color spectrum of natural outdoor light.

Glare: Excessive brightness that may be caused by either direct of indirect viewing of a light source.

Halogen Lamp: A short name for a tungsten-halogen lamp. Halogen lamps are high pressure incandescent lamps containing halogen gases such as iodine or bromine which allow the filaments to be operated at higher temperatures and higher efficacies. A high-temperature chemical reaction, involving tungsten and the halogen gas, recycles evaporated particles of tungsten back onto the filament surface.

Harmonic: An integral multiple of the fundamental frequency (60HZ) that becomes a component of the current.

High Intensity Discharge (HID): This is the general term for a mercury vapor, metal halide, or high-pressure sodium lamp. They differ from incandescent lamps in that there is no filament, but contain gas which when exposed to an electric charge, produces light. HID lamps require a ballast, which controls the electrical current that flows into the lamp.

High Pressure Sodium: These HID bulbs contain a sodium gas and produce a yellow/orange light.

Incandescent: Incandescent light bulbs are perhaps the most commonly found bulb in your home. The incandescent bulb contains a filament, which glows to an incandescent level when electricity flows into the bulb.

Infrared Radiation: Electromagnetic energy radiated in the wavelength range of about 770 to 1106 nanometers. Energy in this range cannot be seen by the human eye, but can be sensed as heat by the skin.

Instant Start: A lamp starting method in which lamps are started by high voltage input with no preheating of lamp filaments. Some rapid start lamps are designed so that they may be instant started.

Instant Start Lamp: A fluorescent lamp with a single pin at each end. The lamp is ignited by a high voltage without any filament heating.

Kelvin Temperature: See Color Temperature Chart – 2000K to 7000K (range for most lighting is 2700K to 5000K, warm white to daylight).

Lamp: The term used to refer to the complete light source package including the inner parts as well as the outer bulb or tube. "Lamp", of course, is also commonly used to refer to a type of small fixture such as a table lamp.

Lamp Watts: Input power used to operate lamps.

LED: Light Emitting Diode.

Low Pressure Sodium: These are also HID bulbs with a sodium gas, and produce a yellowish light.

Lumens Per Watt: A measurement of white light produced by each output watt.

Luminaire: A complete lighting unit consisting of a lamp (or lamps), together with the parts designed to distribute the light, position and protect lamps and connect them to the power supply.

Lumen Maintenance: The lumen output provided by a lamp at a given point or percentage of its life.

Lumen Efficacy: The light output of a source divided by the total power input to that source. It is expressed in lumens per watt.

Maximum Overall Length (M.O.L.): The end-to-end measurement of a lamp expressed in inches or millimeters.

Mean Lumens: The average light output of a lamp over its rated life. For fluorescent and metal halide lamps, mean lumen ratings are measured at 40% of rated lamp life. For mercury, high pressure sodium, and incandescent lamps, mean lumen ratings are measured at 50% of rated lamp life.

Mercury Vapor Lamp: A high-intensity discharge light source operating at a relatively high pressure (about 1 atmosphere) and temperature in which most of the light is produced by radiation from excited mercury vapor. Phosphor coatings on some lamp types add additional light and improve color rendering.

Metal Halide Lamp: These HID bulbs produce a blue-white type light, these bulbs are very efficient, and long lasting.

Neodymium: A rare earth element used in glass that filters out the excessive yellow spectrum to which our eyes are most sensitive.

Parabolic Aluminized Reflector (PAR) Lamp: A type of incandescent lamp made of a heavy glass that controls its light beam using a reflector and lens.

Photocontrol (Photocell): A device used to detect light levels, which controls the electrical operation of a light fixture when changes occur.

Preheat Lamp: A fluorescent lamp in which the filament must be heated by use of a starter before the arc is created. These lamps are typically operated with electromagnetic ballasts.

Programmed Rapid Start: A lamp starting method which preheats the lamp filaments, while not allowing the lamp to ignite, and then applies the open circuit voltage (OCV) to start the lamp. The user may experience a half to one second delay after turning on the lamps while the preheating takes place. This type of starting circuit keeps lamp end blackening to a minimum and improves lamp life performance, especially in applications where the lamps are frequently switched on and off.

Pulse Start Lamp: A specially designed metal halide lamp that uses a ballast with ignitor for starting.

Rapid Start: A lamp starting method in which lamp filaments are heated while open circuit voltage (OCV) is applied to facilitate lamp ignition.

Rapid Start Lamp: A fluorescent lamp with two pins at each end connected to the filament. The filaments are heated by the ballast to aid in starting. Some rapid start lamps may be instant started without filament heat.

Rated Life: See Average Rated Life.

Reflector Lamp: An incandescent, compact fluorescent or HID lamp with a built-in reflecting surface. Incandescent and HID versions are made from a single piece of blow-molded soft or hard glass. CFL versions may be one piece or may be designed so that the inner lamp can be replaced.

Restart or Restrike Time: The amount of time from return of power after an interruption to the point of lamp ignition.

Restrike: To re-ignite the arc of a HID lamp.

Retrofit: A self-ballasted replacement lamp that converts a light source to either change its characteristics or reduce energy consumption.

Shroud: A glass cylinder that surrounds the arc tube in open fixture rated metal halide lamps. The shroud is designed to contain hot arc tube particles and glass bulb breakage, should a rupture occur. This protection reduces the risk of using metal halide lamps in open fixtures.

Starting Temperature: Refers to the lowest outside temperature a fluorescent tube will operate at. This temperature may be determined by the ballast or specific qualities of the lamp in question.

Troffer: An inverted, usually metal, trough suspended from a ceiling as a fixture for fluorescent lighting tubes.

Two-Pin Compact Fluorescent Lamps: Type of lamps that have the glow bottle starter built into the base of the lamp. Traditionally, 2-pin lamps are designed to work with electromagnetic ballasts.

Track Lighting: Generic term used to reference either fixtures attached to a linear track system or a or the linear track itself.

Transformer: A device employing the principle of mutual induction to convert variations of current in a primary circuit into variations of voltage and current in a secondary unit.

Triple-Tube lamp: A triple twin-tube CFL lamp.

UL (Underwriters' Laboratories, Inc.): Laboratory that sets safety standards for building materials, electrical appliances, and other products.

VHO: Very High output. A lamp that operates at 1500MA.

Voltage: Measurement for the electromotive force, or the pressure of electricity.

Warm White: Reference to the color tone or appearance of light produced by a lamp for a specific color temperature. The color of the light from this lamp makes a factory, office or store seem warmer and friendlier. Together with the "white" lamp, this is the most efficient of all fluorescent colors. It is a good choice to blend with incandescent bulbs.

Warm-Up Time: The amount of time from ignition of the lamp to 90% light output.

Watt: A unit of electrical power. Lamps are rated in watts to indicate their power consumption. Power consumed over timer equals the electrical energy used/