Inland AV: Glossary

All industries have their specific terms and definitions. We have reproduced the InfoComm International® glossary to help our clients understand AV terminology.

A I  B I  C I  D I  E I  F I  G I  H I  I I  J I  K I  L I  M
N I  O I  P I  Q I  R I  S I  T I  U I  V I  W I  X I  Y I  Z

A

acceptable viewing area - A viewing range for a screen suggested as a 45-degree line extending outward from the left edge and right edge of a displayed image.

acoustics - the science of sound wave behavior in air.

Adapters - Adapters are used as interfaces in audiovisual technology to change from type of connector, signal format or power source to another.

AES - Audio Engineering Society.

alternating current (AC) - an electric current that reverses its direction periodically.

ambient light - all light in a viewing room produced by sources other than the display.

ambient noise - sound that is extraneous to the intended , desired, intentional, audio; background noise.

amplifier - an electronic device for increasing the strength of electrical signals.

amplitude - the strength of an electronic signal as measured by the height of its waveform.

analog - a method of transmitting information by a continuous but varying signal.

angularly reflective screen - a screen that reflects light back to the viewer at a complementary angle.

annotation - Annotation allows a presenter to mark up a displayed image as a means of highlighting specific information. Annotation technologies include interactive pens & displays, whiteboards, handheld tablet devices, touch-sensitive screens and more.

ANSI - American National Standards Institute.

aperture - an opening in a lens regulating the amount of light passing through the lens to the imager. 

appliances - Digital signage appliances are processing devices that support networks or help manage distribution or playback of digital signage across multiple screens or devices.

archival systems - Archival systems are equipment-based systems designed to ingest, organize & access multi-format rich-media content.

artifacts - small disturbances that affect the quality of a signal.

aspect ratio - the ratio of image width to image height.

assistive listening devices - Assistive listening devices provide enhancement of sound for people who are hard of hearing. The Americans with Disabilities Act mandates the use of assistive listening devices in certain environments.

attenuate - to reduce the amplitude (strength) of a signal or current.

audience response systems - Audience responses systems are devices that tabulate results when presenters ask questions & audience members to respond or vote by pushing buttons.

audio processor - an electronic device used to manipulate audio signals in some manner.

audio signal - an electrical representation of sound.

audio transduction - converting acoustical energy into electrical energy, or electrical energy back into acoustical energy.

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B

balanced circuit - a circuit in which two branches are electrically alike and symmetrical with respect to a common reference point, usually ground; preferred to an unbalanced circuit due to its ability to reject noise.

bands - a grouping or range of frequencies.

bandwidth - 1. A range of frequencies. 2. In terms of a circuit or equipment, the range of frequencies that the circuit or equipment can reliably pass. 3. In terms of a spectrum, defines the range of frequencies used or allowed.

bandwidth limiting - the result of encoding a higher quality signal into a lower quality form, such as RGB converted into S-Video.

baseband - video signal that has not been modulated.

bend radius - maximum amount a conductor can be bent before excessive attenuation is encountered, signal integrity is compromised, or the conductor breaks.

bi-directional polar pattern - the shape of the region where some microphones will be most sensitive to sound from the front and rear, while rejecting sound from the top, bottom and sides.

bit - shortened form of binary digit, symbolized by 1s and 0s.  The smallest unit of digital information.

bit depth - the number of bits used to describe data.

blocking - pieces of wood that have been inserted between structural building elements to provide a secure mounting point for finish materials or products.

block diagram - an illustration of the signal path through a given system.

BNC - a professional type of video connector featuring a two-pin lock.

boundary microphone - a microphone that  relies on reflected sound from a surrounding surface.

broadband - Broadband describes the usage of a wider band of electromagnetic frequencies or channels than standard bandwidth. Broadband applies to signaling in telecommunications, computer networks, video & Internet access.

buffer amplifier - an electronic device that provides some isolation between other components.

bus – (or buss); a wiring system that delivers power and data to various devices.

busbar - An electrically conductive block or bar of metal, typically copper or aluminum, that serves as a common connection for two or more circuits.

byte - an 8-bit word is called a byte.  The acronym for byte is the upper-case B

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C

cable - an assembly of more than one conductor (wire).

capacitance - the ability of a non-conductive material to develop an electrical charge which can distort an electrical signal.

capacitive reactance - the opposition a capacitor offers to alternating current flow. Capacitive reactance decreases with increasing frequency or, for a given frequency; the capacitive reactance decreases with increasing capacitance. The symbol for capacitive reactance is XC.

captive screw connector - sometimes called a Phoenix® connector, it is a molded plastic connector whose termination requires that you strip and slide a wire directly into a slot on the connector.  A set screw then pushes a gate down to hold the wire in place.

card readers - Card readers are learning aids that allow users to swipe magnetic vocabulary cards in a reader which translates the data into spoken audio.

cardioid - heart-shaped region where some microphones will be most sensitive to sound predominately from the front of the microphone diaphragm and reject sound coming from the sides and rear.

carrier - modulated frequency that carries video or audio signal.

category 5 (Cat 5) - the designation for 100-ohm unshielded twisted-pair cables and associated connecting hardware whose characteristics are specified for data transmission up to 100 Mb/s. (Part of the EIA/TIA 568A standard.)

category 5e (Cat 5e) - enhanced version of the Cat-5 cable standard that adds specifications for far end crosstalk. (Part of the EIA/TIA 568A standard.)

category 6 (Cat 6) - cable standard for Gigabit Ethernet and other interconnect that is backward compatible with Category 5 cable, Cat-5e and Cat-3. Cat-6 features more stringent specifications for crosstalk and system noise. (Part of the EIA/TIA 568A standard.)

CATV - Community Antenna Television system. Broadcast signals are received by a centrally located antenna and distributed by cable through a region.

CCTV - (See closed circuit television).

center tap - A connection point located halfway along the winding of a transformer or inductor.

charged-coupled device (CCD) - a semiconductor image-sensing device, commonly used in video and digital cameras, that converts optical images into electronic signals.

chassis - Also called a cabinet or frame, an enclosure that houses electronic equipment and is frequently electrically conductive (metal). The metal enclosure acts as a shield and is connected to the equipment grounding conductor of the AC power cable, if so equipped, in order to provide protection against electric shock.

chassis ground - A 0V (zero volt) connection point of any electrically conductive chassis or enclosure surrounding an electronic device. This connection point may or may not be extended to the earth ground.

chrominance - the color portion of a composite or S-Video signal.

clipping - The deformation of an audio signal when a device's peak amplitude level is exceeded.

clock adjustment - also called timing signals, used to fine tune the computer image. This function adjusts the clock frequencies that eliminate the vertical banding (lines) in the image.

closed circuit television (CCTV) - a system of transmitting video signals from the point of origin to single or multiple points equipped to receive signals.

coaxial cable - a cable consisting of a center conductor surrounded by insulating material, concentric outer conductor and optional protective covering, all of circular cross-section. Abbreviated coax.

CODEC - an acronym for coder/decoder. An electronic device that converts analog signals, such as video and audio signals, into digital form and compresses them to conserve bandwidth on a transmission path.

color burst - that part of an NTSC video signal that carries the color information. It is a signal consisting of several (8 to 10 in NTSC) cycles of unmodulated color subcarriers, superimposed at a specified location within the composite signal.

color difference signals - signals which convey color information such as hue and saturation in a composite format. Two such signals are needed. These color difference signals are R-Y and B-Y, sometimes referred to as Pr and Pb or Cr and Cb.

comb filter - transversal filter that combs out a specific set of frequencies. Comb filters are very effective in separating the chrominance and luminance sidebands in an NTSC video signal.
combiner - in a process called multiplexing, the combiner puts signals together onto one cable constituting a broadband signal.

common-mode - refers to either noise or surge voltage disturbances occurring between the power neutral (white wire) and the grounding conductor (green wire). Unwanted common mode disturbances exist as a result of noise injection into the neutral or grounding wires, wiring faults, or overloaded power circuits.

common-mode rejection ratio (CMRR) - The ratio of the common-mode interference voltage at the input of a circuit, to the corresponding interference voltage at the output.

compander - A device that combines compression and expansion.

component video - color video in which the brightness (luminance) and color hue and saturation (chrominance) are handled independently. The red, green and blue or, more commonly, the Y, R-Y, B-Y signals are encoded onto three wires. Because these signals are independent, processing such as chroma keying is facilitated.

composite video signal - the electrical signal that represents complete color picture information and all synchronization signals, including blanking and the deflection synchronization signals to which the color synchronization signal is added in the appropriate time relationship.

compression - the action of the air molecules moving closer together permitting audible sound.

compressor - a compressor controls the overall amplitude of a signal by reducing that part of the signal which exceeds an adjustable level (threshold) set by the user.  When the signal exceeds the threshold level, the overall amplitude is reduced by a ratio, also usually adjustable by the user.

condenser microphones - also called a capacitor microphone, it transduces sound into electricity using electrostatic principles.

conductor - in electronics, a material that easily conducts an electric current because some electrons in the material are free to move.

cone - most commonly used component in a loudspeaker system and found in all ranges of drivers.

conferencing systems - the technology by which people separated by distance come together to share information.  Conferencing systems may include projection, monitor displays, computers, satellite connections video and audio playback devices, and much more.

continuity - the quality of being continuous (as in a continuous electrical circuit).

control track - the portion along a length of a recorded tape on which sync control information is placed; used to control the recording and playback of the signal.

CPU - (central processing unit); the portion of a computer system that reads and executes commands.

crosstalk - any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel.

CRT - Cathode Ray Tube; the video display tube used in monitors and receivers, radar displays and video computer displays. The CRT is a high-vacuum tube containing an electron gun to produce the images seen on the face of the tube.

cue systems - Cue systems help the speaker communicate with the projectionist and vice versa during a presentation, but with today's presentation systems, the presenter can often control the projector & slides remotely.

current - the amount of electrical energy that is flowing in a circuit.

curvature of field - a blurry appearance around the edge of an otherwise in-focus object (or the reverse) when the velocity of light going through the lens is different at the edges than at the center of the surface, due to the lens design

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D

D-sub connector - a generic name for D-shaped serial connectors used in data communications.

DA - (see distribution amplifier)

dB SPL -  a measure of sound pressure level measured in dynes per centimeter squared. Its reference, 0 dBSPL equals 0.0002 dynes/cm2. dBSPL is used as a measure of acoustical sound pressure levels, and is a 20log function.

decibel - a comparison of two measurements or values.  Abbreviated dB, it is one-tenth of a Bel (a unit of measurement named for Alexander Graham Bell).

deflection coil - a uniform winding of wire used to electromagnetically direct an electron beam to draw an image on a cathode ray tube (CRT).

delay - an audio signal processing device or circuit used to retard the speed of transmission on one or more audio signals or frequencies.

demodulator - electronic device that removes information from a modulated signal.

depth-of-field - the area in front of a camera lens that is in focus from the closest item to the camera to the furthest away.

differential-mode - refers to either noise or surge voltage disturbances occurring between the power hot and the neutral conductor. Most differential mode disturbances result from load switching within a building, with motor type loads being the biggest contributor.

diffusion - the scattering or random redistribution of a sound wave from a surface. It occurs when surfaces are at least as long as the sound wavelengths, but not more than four times as long.

digital - a method of transmitting information by discrete, non-continuous impulses.

digital asset management systems - Digital asset management systems are comprised of hardware systems & software that support capture, storage, retrieval & distribution of media assets. Digital assets include everything from digital text & images to audio, video & animations.

digital-to-analog converter - an electronic device that converts digital signals into analog form.

digital media players - Digital media players are devices that allow users to playback or stream audio & video content from digital media servers, the Internet or computer hard drives.

D-ILA - Digital Direct Drive Image Light Amplification projectors.

DIN connector - Deutsche Industrie-Norm (DIN) - a connector that follows the German standard for electronic connections.

direct current (DC) - electricity that maintains a steady flow and does not reverse direction, unlike alternating current (AC). Usually provided by batteries, AC to DC transformers, and power supplies.

direct sound - also known as near-field, it is sound that is not colored by room reflections.

dirty ground - an ambiguous term that refers to a ground with electromagnetic interference present.

dispersion - can be seen when a white light beam passes through a triangular prism.  The different wavelengths of light refract at different angles, dispersing the light into its individual components.

distributed sound - a sound system in multiple loudspeakers separated by distance and typically operates in a lower sound pressure level than a high pressure system.  The loudspeakers are most often suspended over the heads of the listeners.

distribution amplifier - an active device used to split one input into multiple outputs, while keeping each output isolated, and the signal level constant.

DLP - Digital Light Processing™ by Texas Instruments. A projection system that has technology based on the Digital Micromirror Device (DMD). It uses thousands of microscopic mirrors on a chip focused through an optical system to display images on screen.

document camera - an imaging device used to create a video image of printed documents or three-dimensional objects.

dome - used in all ranges of loudspeaker drivers.

driver - in audio, an individual loudspeaker unit.

D-subconnector - A generic name for a D-shaped serial connector used in data communications.

DTV - Digital Television; a signal transmitted digitally.

DVD - Digital Video Disc or Digital Versatile Disk; an optical storage medium for data or video.

DVI - Digital Visual Interface; a connection method from a source (typically a computer) and a display device that can allow for direct digital transfer of data.  The digital signal is limited to 5 meters.

DVI-D - one of two common multi-pin connectors available for DVI signals.  The DVI-D carries no analog video information, only digital.  The digital signal is limited to 5 meters.

DVI-I - one of two common multi-pin connectors available for DVI signals.  The DVI-I adds analog video to the connection, permitting greater distances than the digital limit of 5 meters.

dynamic microphone - a pressure-sensitive microphone of moving coil design that transduces sound into electricity using electromagnetic principles.

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E

early reflected sound - created by sound waves which are reflected (bounced) off surfaces between the source and the listener.  The sound waves arrive at the listener's ear closely on the heels of the direct sound wave.

Earsets - Earsets allows the user to listen to an audio signal in a single ear as opposed to both ears in a headset.

echo cancellation - a means of eliminating echo from an audio path.

EIA - Electronics Industries Alliance. The association which determines recommended audio and video standards in the United States.

electromagnetic interference (EMI) - an electrical disturbance caused by an electromagnetic field, either low frequency or radio frequency (RF).

EMI - (See electromagnetic interference.)

emissive technology - any display device that emits light to create an image.

encoded - a signal that has been compressed into another form to reduce size or complexity, as in a composite video signal.

equalizer - electronic equipment that adjusts or corrects the frequency characteristics of a signal.

equipment grounding - The connection to ground (earth), or to a conductive body that extends that ground connection, of all normally noncurrent-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment. The purpose is to limit any voltage potential between the equipment and earth.

equipment grounding conductor (ECG) - The conductive path installed to connect normally noncurrent-carrying metal parts of equipment together and to the system's grounded conductor, to the grounding electrode conductor, or to both.

equipment rack - a centralized housing unit that protects and organizes electronic equipment.

Ethernet - a set of network cabling and network access protocol standards for bus topology computer networks invented by Xerox but now controlled by the 802.3 subcommittee of the IEEE.

expander - an audio processor that comes in two types – a downward expander and a part of a compander.

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F

F connector - a threaded connector that is used in transmission applications such as cable television.  The cable's center conductor also serves as the connector's center pin.

feedback  - 1. unwanted noise caused by the loop of an audio system’s output back to its input.  2. in a control system, data supplied to give an indication of status, i.e., on or off.

fiber optic - a technology that uses glass or plastic threads or wires to transmit information.

field - one half of a video frame containing every other line of information. Each standard video frame contains two interlaced fields.

filter - filters remove or pass certain frequencies from a signal.

fixed matrix - a type of display that has a fixed grid on which it recreates an image.

flex life - the number of times a cable can be bent before it breaks. A wire with more strands, or more twists per inch, will have a greater flex life than one with a lower number of strands, or one with less twists per inch.

focal length - abbreviated as FL, it is the distance, in millimeters, between the center of a lens and the point where the image comes into focus. The value given to a lens, stated in inches or millimeters. The shorter the focal length, the wider the angle of the image.

focus - the act of adjusting a lens to make the image appear clear, sharp, and well-defined.

footcandle - abbreviated as Ftc, it is an English unit of measure expressing the intensity of light illuminating an object. The illumination from one candle falling on a surface of 1 square foot at a distance of 1 foot.

footprint - 1. indicates where possible mounting points are to join two pieces together, the total contact area, and how they may or may not fit together. 2. space required to house an equipment rack or device. 3. coverage area of a communications satellite.

frame – 1. an individual segment of film  
2. a complete video picture or image of odd and even fields; two fields equal one frame.

frequency - cycles per second, expressed in Hertz (Hz) or the number of cycles in a given time period. 

frequency response - the range of frequencies within which a microphone is sensitive.

fresnel lens - a flat glass or acrylic lens in which the curvature of a normal lens surface has been collapsed in such a way that concentric circles are impressed on the lens surface; often used for the condenser lens in overhead projectors, in rear projection screens, and in studio spot lights.

front screen projection - a system that employs a light reflecting screen for use when the image will be projected from a source in front of the screen.

f-stop - the ratio of focal length to the effective diameter of a lens; also called f-number, it represents how much light is able to pass through the lens.

fundamental frequency - the lowest frequency in a harmonic series; known as “pure tone”.

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G

gain - 1. electronic signal amplification.
2. the ability of a projection screen to concentrate light.

gate - an audio processor that allows signals to pass only above a certain setting or threshold.

gauge - a thickness or diameter of a wire.

genlock - to lock the synchronization signals of multiple devices to a single source; the condition which exists when the sync generators of multiple devices are locked to a single source.

glass bead screen - screen covered with tiny glass beads, each of which provides a spherically reflective surface.

good viewing area - The good area from which to view a screen. Typically defined as any point within 45 degrees to the left or right from on-axis. The total good viewing area is 90 degrees.

graphics adaptors - commonly referred to as a "video card", which outputs computer signals.

ground lift - 1. Interruption of a cable shield connection by means of a switch or by simple omission in an attempt to solve a hum or buzz problem from current flowing on a cable shield due to a pin 1 problem, detrimental ground loop, and so on. 2. Interruption of the connection between the chassis ground and signal ground, usually by means of a switch. 3. Incorrect term used for a 3-pin-to-2-pin AC adapter.

ground loop - An electrically conductive loop that has two or more ground reference connections. The loop can be detrimental when the reference connections are at different potentials, which causes current flow within the loop (IEEE).

ground plane - A continuous conductive area. The fundamental property of a ground plane is that every point on its surface is at the same potential (low impedance) at all frequencies of concern.

ground potential - A point of no potential in a circuit.

ground reference - The 0V (zero volt) reference point for a circuit.

grounded conductor - A system or circuit conductor that is intentionally grounded.

ground-fault circuit interrupter (GFCI) - A safety device that deenergizes a circuit (or a portion of that circuit) within an established period of time when a current to ground exceeds the values established for a Class A device. Class A GFCIs trip when the current to ground is 6 mA or higher; they do not trip when the current to ground is less than 4 mA.

ground-fault current path - An electrically conductive path from the point of a ground fault on a wiring system through normally noncurrent-carrying conductors, equipment, or earth to the electrical supply source.

grounding - the techniques and hardware that connect electronic equipment and wiring to a reference point.

grounding adapter - A 3-pin-to-2-pin electrical adapter, the design of which is defined by National Electrical Code 406.9. The rigid tab or lug is to be used for equipment grounding and not left "floating."

grounding electrode conductor - The conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system.

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H

harmonics - higher frequency sound waves that blend with the fundamental frequency.

HDMI - HDMI is a digital connection which enables uncompressed high-definition audio and video to be sent over one cable. Digital AV sources (such as BluRay players) use HDMI cables to transmit signals to HDTVs, HD projectors, monitors, Tablet PCs & digital audio devices.

HDTV - High Definition Television.

headend – the equipment located at the start of a cable distribution system where the signals are processed and combined prior to distribution.

headroom - The difference in dB SPL between peak and average level performance of an audio system. For a speech-only system, this value is 10 dB.

heat sink - a device that absorbs and dissipates heat produced by an electrical component.

hemispheric polar pattern - the dome shape of the region that some microphones will be most sensitive to sound. Used for boundary microphones.

hertz (Hz) - cycles per second of an electrical signal.

hiss - Broadband higher-frequency noise typically associated with poor audio system gain structure.

horizontal blanking - the H sync pulse that tells the retrace electron beam to turn off at the end of each line.

horizontal blanking interval - the time during which the electron beam is turned off so that it can move into position to begin the next scan line; usually a very brief period, lasting between 5 -15 microseconds.

horns - loudspeakers that reproduce mid to high frequencies.

hot spot - the part of a displayed image which is unevenly illuminated, usually a bright area in the center.

hum - Undesirable 60 Hz noise emanating from a sound system or evidenced by a rolling hum bar on a display.

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I

IEEE - The Institute of Electrical and Electronics Engineers.

impedance - opposition to alternating current measured in ohms; it may vary with frequency of the applied current; also referred to in microphone technology as Hi Z and Lo Z.

inductance - the ability of a magnetic field to transfer electrical current on a conductor.

inductive reactance - the opposition to the flow of alternating current by the inductance of a circuit, measured in ohms.

infrared (IR) - a frequency range of light used to send information.  Remote controls and other wireless devices use IR.

insulation - material applied to a conductor that is used to isolate the flow of electric current between conductors and to provide protection to the conductor; also known as the dielectric.

interactive whiteboard - Interactive Whiteboards are an essential tool in business and classroom communications. They are used to display text, data and graphics from a computer or projector onto a large surface or display. Presenters and users can then interact with the image using a pen, stylus, finger or other device.

interlaced scanning - the scanning process that combines odd and even fields of video to produce a full frame of video signal.

Inverse Square Law - law of physics stating that some physical quantity or strength is inversely proportional to the square of the distance from the source of that physical quantity.  Applied to light and sound in AV.

IP - Internet protocol (IP); standard networking protocol, or method, which enables data to be sent from one computer or device to another over the Internet. 

ISDN - Integrated Services Digital Network (ISDN) is a communications standard for transmitting voice, video and data over digital phone lines or the traditional telephone network. Common applications of ISDN include telecommuting, Internet access, video conferencing & data networking.

isolated ground - A commonly misused term to describe a requirement for a dedicated equipment ground that terminates only at the main panelboard at the service entrance. An equipment grounding method permitted by the National Electrical Code (NEC) for the reduction of electrical noise (electromagnetic interference) on the grounding circuit. Equipment grounding for isolated receptacles and circuits is accomplished via insulated equipment grounding conductors and run with the circuit conductors.

isolated grounding circuit - A circuit that allows an equipment enclosure to be isolated from the raceway containing circuits, supplying only that equipment by one or more listed nonmetallic raceway fittings. The equipment is grounded via an insulated grounding conductor. (See National Electric Code 250.96 (B) for additional information.)

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J

jacket - outside covering used to protect wires in a cable and their shielding.

junction box - 1. A portable set terminal for power cables. 2. Generally, metal or plastic boxes where wire and/or cable terminates, combines, or splits; used to protect the conductors.

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K

keystone error - the trapezoidal distortion of a square-cornered image due to the optical effect of the projection device not being located in its proper position in respect to the screen.

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L

LAN - Local Area Network; a computer network limited to the immediate area, usually the same building or floor of a building.

lavalier - a small microphone designed to be worn either around the neck or clipped to apparel.

LCD - Liquid Crystal Display. 

LCoS - Liquid Crystal on Silicon

least favored viewer (LFV) - The farthest usable seat from the image. The LFV depends on the viewing angle toward the screen, image size, and content being displayed.

LED - Light Emitting Diode.

lenticular - a screen surface characterized by silvered or aluminized embossing, designed to reflect maximum light over wide horizontal and narrow vertical angles. Must be held very flat to avoid hot spots.

lifts - Lifts are designed to raise or lower equipment for easy access and storage as needed.

limiter - audio signal processor that  functions like a compressor except that signals exceeding the threshold level are reduced at ratios of 10:1 or greater.

load center - An electrical industry term used to identify a lighting and appliance panelboard designed for use in residential and light-commercial applications.

local monitor - a device used to monitor the output of a signal from a system or other device in a local vicinity.

logarithm - A logarithm is the exponent of base 10 that equals the value of a number.

loudspeaker - a transducer that converts electrical energy into acoustical energy.
Loudspeaker components are primarily a driver within an enclosure.

low voltage - An ambiguous term. It may mean less than 70V AC to an AV contractor, while an electrician may use the same term to describe circuits less than 600V AC. The term may also be determined by the authority having jurisdiction (AHJ).

lumen - a measure of the light quantity emitted from a constant light source across one square meter.

luminance - also called luma and abbreviated Y, it is part of a bandwidth limited video signal combining sync information and brightness information.

lux - a contraction of the words luminance and flux; metric version of footcandle.

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M

matrix decoder - produces red, green, and blue from Y, R-Y, and B-Y.

matrix switcher - an electronic device with multiple inputs and outputs, the matrix allows any input to be connected to any one, several, or all of the outputs.

matte white screen - evenly disperses light 180 degrees uniformly, both horizontally and vertically, creating a wide viewing cone and wide viewing angle.

MATV - Master Antenna Television system; a television system where broadcast programs are received via a master antenna array and then distributed to users over coaxial cable or fiber optic cable.

media players - Media players are used in digital signage to play and/or schedule content such as media files across a network of displays.

media retrieval system - a system in a facility that allows for remote requests of content to be delivered from a headend location.

microphone sensitivity - a specification that tells how much electrical energy is derived from a specified sound level input.

midrange - loudspeakers that reproduce midrange frequencies, typically 300 Hz - 8,000 Hz.

mixer - device for blending multiple audio sources.
 
modulator - converts composite or S-Video signals, along with corresponding audio signals, into modulated signals on a carrier channel.

modular connector - connector used with 4, 6, or 8 pins.  Common modular connectors are RJ-11 and RJ-45.

monophonic - uses input from all microphones and relays them from the electronic control system to the loudspeakers using a single path or channel.

MPEG-2 - Moving Pictures Expert Group; refers to a compression scheme that reduces the number of bits needed to code the video image.

multimeter - a multipurpose test instrument with a number of different ranges for measuring current, voltage, and resistance.

multiplexing - the process used by the combiner to put together a number of modulated signals.

multipoint - videoconferencing that links many sites to a common gateway service allowing all sites to see, hear, and interact at the same time; requires a bridge or bridging service.  Also called continuous presence.

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N

native resolution - the number rows of horizontal and vertical pixels that create the picture. The native resolution describes the actual resolution of the imaging device and not the resolution of the delivery signal.

near-field - sound that has not been colored by room reflections.  This is also known as direct sound.

nit - the metric unit for screen, or surface brightness.

noise - Any electrical signal present in a circuit other than the desired signal.

notch filter - "notches out”, or eliminates, a specific band of frequencies.

NTSC - National Television System Committee; the standard for analog video transmission in North America.

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O

octave - a band, or group of frequencies.  The relationship of the frequencies is such that the lowest frequency is half the highest: 200 Hz – 400 Hz is an octave, 4,000 Hz – 8,000 Hz is an octave.

Ohm’s Law - defines the relationship between current, voltage, and resistance in an electrical circuit as proportional to applied voltage and inversely proportional to resistance. The formula is I=V/R. I-current (in amps), V= voltage (in volts), R = Resistance (in Ohms).

omni-directional - describes the shape of the area for microphones that have equal sensitivity to sound from nearly all directions.

on-axis - The center point of a screen, perpendicular to the viewing area for a displayed image. This is considered to be the best location for viewing.

operating system (OS) - platform; enables software applications to communicate with the CPU.

oscilloscope - a test device that allows measurement of electronic signals by displaying the waveform on a CRT.

overhead projector - a device which produces an image on a screen by transmitting light through transparent acetate placed on the stage of the projector.

overcurrent - Any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, a short circuit, or a ground fault.

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P

PAL - Phase Alternate Line; the video standard for much of Europe and Australia.

panelboard - A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices. A panelboard may be equipped with switches for the control of light, heat, or power circuits. It is designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support, and accessible only from the front.

PDP - (See Plasma Display Panel).

peak - the highest level of signal strength, determined by the height of the signal's waveform.

peaking - an adjustment method that allows compensation for high frequency loss in cables.

phantom power - a direct current (DC) power source available in various voltages. 

phase - the relative timing of one signal to another.

Phoenix® - a molded, plastic, captive screw connector whose termination requires that you strip and slide a wire directly into a hole on the connector (compression termination).

phone connector - an audio connector used as a loudspeaker connector. Common types are 1/4 inch and 1/8 inch.

phono - the European name for an RCA connector.

phosphor - the substance which glows when struck by an electron beam, providing the image in a CRT. The higher the quality of the phosphor, the brighter and more vivid the image.

pink noise - a sound that has equal energy (constant power) in each 1/3-octave band.

pixel - acronym for picture element. The small element used to build a digital image.

Plasma display panel (PDP) - A direct view display made up of an array of cells, known as pixels, which are composed of three subpixels, corresponding to the colors red, green, and blue. Gas in the plasma state is used to react with phosphors in each subpixel to produce colored light (red, green, or blue) from a phosphor in each subpixel.

plenum boxes - Plenum boxes are designed to house equipment that requires air flow or ventilation to keep cool. Plenum boxes are typically used with ceiling-mounted projectors, so that cabling & equipment are not run through a plenum (air-flow space) to avoid fire hazards.

point-to-point - conferencing where two sites are directly linked.

point-source - a sound system that has a central location for the loudspeaker(s), mounted high above, intended to cover a large area; typical of a performance venue or a large house of worship.

polar pattern - (or pickup pattern); the shape of the area that a microphone will be most sensitive to sound.

power distribution unit - A rack-mountable or portable electrical enclosure that is connected by a cord or cable to a branch circuit for distribution of power to multiple electronic devices. A PDU may contain switches, overcurrent protection, control connections, and receptacles.

power conditioners - Power conditioners enhance the quality of power going to equipment by regulating voltage, eliminating noise or correcting other issues.

preamplifiers - A preamplifier or preamp is an electronic device that boosts a signal and sends it to a main amplifier for further processing.

primary optic - the lens that focuses the image onto the screen.

prism - a prism beam splitter filters the light into its red, green, and blue components.

progressive scanning - traces the image's scan lines sequentially, such as an analog computer monitor.

pulling tension - maximum amount of tension that can be applied to a cable or conductor before it is damaged.

pure tone - (See fundamental frequency.)

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R

raceway - An enclosed channel of metal or nonmetallic materials designed for holding wires, cables, or busbars, with additional functions. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquid-tight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways, and busways.

rack unit (RU) - unit of measure of the vertical space in a rack. One RU equals 1.75 inches (44.5 mm).

radio frequency (RF) - generally refers to signals such as radio and TV broadcast signals, or radio frequency control signals; the range of frequencies used for electrical transmission.

radio frequency interference(RFI) - tendency of a radio transmission to interfere with other electronic signals. Radio frequency energy is radiated by all electrical equipment - when it is a strong enough signal it becomes interference in audio systems.

RAM - Random Access Memory; the most common computer memory used by programs to perform necessary tasks while the computer is on; an integrated circuit memory chip allows information to be stored or accessed in any order and all storage locations are equally accessible.

rarefaction - the action of the molecules moving apart.

raster - the scanned or illuminated area of a CRT.

ratio - the comparison of two quantities.

RCA - a connector most often used with line level audio signals; also known as a phono connector.

rear screen projection - a presentation system in which the image is projected through a translucent screen toward the audience; projecting an image through a translucent screen material for viewing from the opposite side, as opposed to front projection.

receivers (audio) - A receiver is an audio-video device that amplifies sound, routes video signals, often includes an AM-FM tuner and serves as a selector for different types of equipment.

reflection - light or sound energy that has been redirected by a surface.

reflective technology - any display device that reflects light to create an image.

refraction - the bending or changing of the direction of a light ray when passing through a material, such as water or glass.  How much light refracts, meaning how great the angle of refraction, is called the refractive index.

resistance - the property of a material to impede the flow of electrical current, expressed in ohms.

resolution - 1. the amount of detail in an image.  2. the number of picture elements (pixels) in a display.

retrace time - the time it takes for the electron beam to turn off, travel to its next starting point, then turn back on to begin scanning again.

retro unit - self-contained rear projection system.

reverberant sound - sound waves that bounce off of multiple surfaces before reaching the listener, but arrive at the listener's ears quite a bit later than early reflected sound. 

RF system - a closed circuit system becomes an RF system when the composite video and audio signals are modulated at a certain frequency, called a channel.  RF systems require a display device (e.g. TV) with a tuner set to a selected channel to display the information modulated onto that frequency.

RGBHV - refers to a high bandwidth video signal with separate conductors for the red signal, green signal, blue signal, horizontal sync and vertical sync.

RGBS - refers to a four component signal comprised of a red signal, green signal, blue signal, and a composite sync signal.

RGSB - refers to a three component signal comprised of a red signal, green signal with composite sync added to the green channel and a blue signal.  Often called “sync on green.”

ring - a network topology that connects terminals, computers or nodes in a continuous loop.

ROM - Read Only Memory; memory whose contents can be accessed and read but cannot be changed. Permanent memory that can only be entered once, normally by a manufacturer; may not be altered or removed.

RsGsBs - red, green, and blue signals with composite sync added to each color channel; referred to as "RGB sync on all three”.  It requires three cables to carry the entire signal.

RU - (See Rack Units).

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S

sampling rate - how many samples of the analog signal are taken in a given time interval in creating the digital signal.

satellite television - entertainment or business video and audio transmitted via a satellite.

scaler - feature in a display device that changes the size of an image without changing its shape. Scaling may be required when the image size does not fit the display device.

scan conversion - the process of changing the horizontal scan rate of one device to that of another. Usually used to describe changing the scan rate of a computer to match the television (NTSC/PAL/SECAM) video format for the purpose of recording or viewing on television video equipment.

scan rate - the frequency of occurrence of a display drawing one line of information.

scattering - when light hits a textured surface, the incoming light waves get reflected in multiple angles because the surface is uneven.

screen gain - Describes the distribution of light reflected off a projection screen. The amount of gain is compared to a matte-white screen, which reradiates light and distributes it with perfect uniformity.

SDTV - Standard Definition Television.

SECAM - Séquentiel Couleur Avec Mémoire (Sequential Color with Memory); the video standard in France.

shield - 1. a physical layer in some cables used to protect signals and sometimes used as a return path for current. Three basic types of cable shielding: foil, braid and combination.

short circuit - The electrical connection between any two conductors of the electrical system from line-to-line or from line-to-neutral (Basic Electrical Theory, by Mike Holt). (A short circuit is not the same as a ground fault.)

shotgun microphone - a long, cylindrical, highly sensitive, unidirectional microphone used to pick up sound from a great distance.

signal generator - test equipment instrument that produces calibrated electronic signals intended for the testing or alignment of electronic circuits or systems.

signal to noise ratio - (S/N ratio); the ratio, measured in decibels, between the audio or video signal, and the noise accompanying the signal. The higher the S/N ratio, the better the quality of the sound or picture.

single-phase power - Alternating current electrical power supplied by two current carrying conductors. This type of power is used for residential and some light-commercial applications.

SMATV - Satellite and Master Antenna Television system; a television system where satellite and broadcast programs are received via a master antenna array and distributed to users over coaxial cable or fiber optic cable. 

sound masking systems - Sound masking systems add artificial or natural sound to an environment such as an office to mask unwanted sound & foster speech privacy among coworkers in a workspace.

SMPTE - Society of Motion Picture and Television Engineers.

Speakon™ - specialized connector used to hook up loudspeakers without causing a short circuit; allows connection of loudspeaker while working, or hot.

spherical aberration - light passing through the edges of the lenses can also have focal lengths different from those passing through the center is called spherical aberration.

splitter - an electronic device that divides a signal into different pieces to route to different devices.

star - a network topology where all network devices are connected to a central network device that is usually a hub or a switch.

stereophonic - commonly shortened to "stereo", input from all microphones is split into at least two channels before driving the signal through the loudspeakers.

streaming video and audio - sequence of "moving images" or "sounds" sent in a continuous, compressed stream over the Internet and displayed by the viewer as they arrive. With streaming video or audio, a web user does not have to wait to download a large file before seeing the video or hearing the sound.

subwoofers - loudspeakers that reproduce lower frequencies, typically 20 Hz - 200 Hz.

super cardioid polar pattern - the exaggerated heart-shape of the area that a highly directional microphone is most sensitive to sound.

surface mount microphone - also called a boundary microphone, placed on a table to pick up sound. Used in boardrooms and other environments where a number of talkers must be "picked up" and where the microphone needs to remain unobtrusive.

surround sound - more complex stereo playback systems that use from two to five channels for realistic sound production. The popular term used to describe an experience where the sound 'surrounds' you. This is best achieved using surround-encoded material, a receiver, and surround loudspeakers.

S-Video - a video signal, also known as Y/C. Y is the luminance and C is the chrominance. Y and C are transmitted on separate conductors.

switcher - a peripheral or sometimes integrated device used to select one of a group of signals.

sync - shortened form of synchronization; the timing information that keeps images displaying properly.

system - a compilation of multiple individual AV components and sub-systems interconnected to achieve a communication goal.

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T

taps - connections to the transformer windings allowing you to select different power levels from the transformer.

tensile strength - the maximum force that a material can withstand before deforming or stretching.

three-phase power - Alternating current electrical power supplied by three current carrying conductors, each offset by 120 degrees from one another. A fourth conductor, a neutral, is used as the return conductor. This type of power is used for commercial and industrial applications.

throw distance - the length of the projection beam necessary for a particular projector to produce an image of a specified size.

time base corrector (TBC) - the circuitry, or a stand alone component, used to stabilize the horizontal lines of an analog video image (typically originating from tape).

time code - a method of numbering video frames according to SMPTE standards; the 8-digit address representing hour, minute, second, and frame, recorded on the videotape's control track.

transmissive technology - any display device that creates images by allowing or preventing light to pass.

transient disturbance - a momentary variation in power such as a surge, spike, sag, blackout, noise, or other type of transient.

TRS - Tip, Ring, Sleeve - a three-conductor design of a phone connector that can be terminated as balanced or unbalanced.

TS - Tip, Sleeve - a two-conductor design of a phone connector used for an unbalanced circuit.

tweeters - loudspeakers that have high frequencies, typically 2,000 Hz - 20,000 Hz.

twisted pair - any number of wires that are paired together and twisted around each other; can be shielded or unshielded.

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U

unbalanced circuit - transmits the audio signal on a single conductor that is referenced to ground.

unity gain - derived from the number 1, unity gain refers to no change in gain.

UTP - unshielded twisted pair cable typically used for data transfer, contains multiple 2-conductor pairs twisted at regular intervals, employing no external shielding.

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V

vectorscope - a specialized oscilloscope used in video systems to measure chrominance accuracy and levels.

vertical blanking - the action of turning off the trace on an analog CRT during vertical retrace.

video wall - A video wall features several monitors, video screens, display cubes, video projectors or TV sets that are set up on top of each other or side by side to form a single, large contiguous display.

viewing angle - the viewing angle determines how far off the axis (screen centerline) a viewer can still sit and still see a quality image. This is no greater than 45 degrees off the projection axis.

viewing cone - the best viewing area for the audience.  The term cone is used because there is width, height, and depth to the best viewing area, and this area emanates from the center of the screen.

VOIP Systems - VOIP Systems or Voice over Internet Protocol are protocols & technology that allow the digital transmission of phone calls & multimedia over the Internet & other networks. VOIP is relayed over smartphones and other internet devices & requires equipment such as VOIP routers, phone adapters, telephone sets & more.

volt - the basic international unit of potential difference or electromotive force;  symbolized by an upper case V.

voltage - the electrical potential to create current flow in a circuit.

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W

WAN - Wide Area Network; a data communications system that uses telecommunications circuits to link local area networks (LANs) that are distributed over large geographic distances.

waveform monitor - a specialized oscilloscope used to display and analyze the video signals sync, luminance and chroma levels.

wavelength - the distance between two corresponding points of two consecutive cycles measured in meters.

webcasting - Webcasting allows the broadcast of digital media such as audio or video over the Internet which audience members can stream live or access on demand. Essential equipment for webcasting includes computers, streaming servers, production software, recording gear, appliances & more.

wire - a single conductive element intended to carry a voltage or electronic signal.

white noise - a sound that has the same energy level at all frequencies.

WLAN - Wireless Local Area Network; a network that shares information by radio frequency (RF).

woofers - loudspeakers that have low frequencies, typically 20 Hz - 200 Hz.

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X

XLR connector - a popular type of audio connector featuring three leads: two for the signal and one for overall system grounding. A secure connector often found on high quality audio and video equipment; sometimes called a Canon connector.

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Y

Y/C - a video signal, also known as S-Video. Y is the luminance and C is the chrominance. Y and C are transmitted on separate synchronized conductors.

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Z

zero reference - InfoComm experts consider that this term ambiguous. See reference point.

zoom lens - lenses that allow the operator to adjust focal length for sizing or distance.

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