APPENDIX I

GLOSSARY

AMPLIFIER \The device that provides amplification (the increase in current, voltage, or power of a signal) without appreciably altering the original signal.

ANNUNCIATOR \An electrical signaling device that displays a visual indication, usually a flashing light.

APPROACH LIGHTS\A configuration of ground lights located in the extension of a runway before the threshold to provide visual approach and landing guidance to pilots.

AUTOMATIC FIRE ALARM SYSTEM\ A system using fire detectors, such as heat, smoke, and flame detectors, to initiate alarms automatically.

BALLAST\A device used with an electricdischarge lamp to obtain the necessary circuit conditions (voltage, current, and waveform) for starting and operating.

BASE\The element in a transistor that controls the flow of current carriers.

CANDELA (FORMERLY CANDLE)\The unit of luminous intensity used to measure the intensity of light radiated from a light source. It is the average luminous intensity of the international candle. This intensity is usually expressed as CANDLEPOWER instead of as candles of luminous intensity.

CATHODE \The negative terminal of a forward-biased semiconductor diode, which is the source of the electrons.

CATHODE-RAY TUBE (CRT)\An electron tube which has an electron gun, a deflection system, and a screen. This tube is used to display visual electronic signals.

COEFFICIENT OF UTILIZATION\ Concerning the light from a luminaire, the ratio of lumens received on the work plane to the lumens emitted by the luminaire lamp.

COLLECTOR\The element in a transistor that collects the current carriers.

COMMON BASE\A transistor circuit in which the base electrode is the element common to both the input and the output circuits.

COMMON COLLECTOR\A circuit configuration in which the emitter is the element common to both the input and the output circuits.

DIELECTRIC\A nonconductor of electricity; an insulator or insulating material.

DIFFUSER\A device to redirect or scatter the light from a source.

DIODE\A two-element solid-state device made of either germanium or silicon. It is primarily used as a switching device.

DONOR\An impurity that can make a semiconductor material an N-type by donating extra "free" electrons to the conduction band.

DOPING\The process of adding impurities to semiconductor crystals to increase the number of free charges that can be moved by an external, applied voltage. Doping produces N-type or P-type materials.

DUSTPROOF LUMINAIRE\A luminaire so constructed or protected that dust will not interfere with its successful operation.

DUST-TIGHT LUMINAIRE\A luminaire so constructed that dust will not enter the enclosing case.

ELECTRIC-DISCHARGE LAMP\A lamp in which light is produced by the passage of an electric current through a vapor or a gas.

EMERGENCY LIGHT\Lighting designed to supply illumination essential to safety of life and property in the event of failure of the normal light.

EMITTER\The element in a transistor that emits current carriers (electrons or holes).

EXPLOSION-PROOF LUMINAIRE\A completely enclosed luminaire capable of withstanding an explosion within it and preventing the ignition of a gas or vapor surrounding the enclosure by sparks, flashes, or explosion. The external temperature at which it is operated must be such that a surrounding flammable atmosphere will not be ignited.

FIELD-EFFECT TRANSISTOR (FET)\A transistor consisting of a source, a gate, and a drain. Current flow is controlled by the transverse electric field under the gate.

FLOODLIGHT \A system designed for lighting a scene or an object to a luminance greater than that of its surroundings.

FLUORESCENT LAMP\A low-pressure mercury electric-discharge lamp in which a fluorescing coating on its inner surface transforms some of the ultraviolet energy generated by the discharge into light.

FLUORESCENT-MERCURY LAMP\An electric-discharge lamp having a high-pressure mercury arc in an arc tube and an outer envelope coated with a fluorescing substance that transforms some of the ultraviolet energy generated by the arc into light.

FOOTCANDLE \The illumination intensity or luminous density on a surface 1 foot distant and perpendicular to the rays emitted by a light source of 1 candlepower.

FORWARD BIAS\An external voltage that is applied to a PN-junction in the conducting direction so that the junction offers only minimum resistance to the flow of current. Conduction is by the majority current carriers (holes in P-type material; electrons in N-type material).

FULL-WAVE RECTIFIER\A circuit that uses both positive and negative alternations in an alternating current to produce direct current.

GENERAL-PURPOSE FLOODLIGHT\A weatherproof fixture so constructed that the housing forms the reflecting surface. The assembly is enclosed by a glass cover.

GIN POLE\An upright guy pole with hoisting tackle and a foot-mounted snatch block used for vertical lifts.

GLARE\Light from a source or a reflecting surface that interferes with proper vision or causes eye discomfort. The amount of glare depends on the brightness of the light source, the contrast between the source and the background, and the location of the light source in respect to the field of vision.

GROUND\A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth.

GROUNDING CONDUCTOR\A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode.

GROUNDING ELECTRODE\A conductor embedded in the earth for maintaining ground potential on conductors connected to it.