1/3 octave equalizer   A graphic equalizer that provides 30 or 31 slider adjustments corresponding to specific fixed frequencies with fixed bandwidths, with the frequencies centered at every one-third of an octave. The adjustment points shape the overall frequency response of the system.

4K   An ultra-high-resolution video format with a resolution approximately four times that of full HD (1920×1080 pixels). 4K formats include 3840×2160 pixels (UHDTV) and 4096×2160 pixels (digital cinema, DCI).

8K   An ultra-high-resolution video format with a resolution of 7680×4320 pixels, which is 16 times the resolution of full HD (1920×1080 pixels).

9-pin connector   The DB 9 is the most common type of connector used in RS-232 control systems.

acceptable viewing area   The viewing range for a screen; suggested as a 60-degree arc of the far vertical edge of the screen being viewed.

access point   A network device that allows other devices to connect to a network.

acoustic echo canceller   Used in conferencing systems. The echo canceller attempts to remove environmental echoes that are created at the far site from sound reflected off hard surfaces and returned to conferencing microphones.

acoustics   The properties or qualities of a room or building that determine how sound is transmitted and reflected it. The study of the properties of sound.

AES   Audio Engineering Society.

allied trade   A business that collaborates with AV professionals to complete a project.

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

ambient light   The sum of all lighting in an area.

ambient noise   The sum of all sounds in an area.

amperage   The amount of electric current flowing in a circuit. Current is measured in amperes (amps), abbreviated as A.

amplifier   A device for increasing the strength of signals.

amplitude   The height of the waveform of a signal.

analog (analogue)   A continuously variable signal.

analog-to-digital/digital-to-analog (AD/DA) converters   Devices that convert signals from analog to digital or from digital to analog.

angularly reflective screen   A screen that reflects light at the same angle at which it arrived.

ANSI   American National Standards Institute.

aperture   The opening in an optical train that controls the amount of light passing through.

arrayed loudspeaker system   A loudspeaker arrangement that delivers sound from a single point in space.

artifact   An element introduced into a signal during processing. Not always a good thing.

aspect ratio   The ratio of image width to image height.

attack time   A setting within a digital signal processor that determines how rapidly the signal level will be reduced once the volume exceeds the threshold. If the attack time is too slow, then the sound will become distorted as the system adjusts.

attenuate   To reduce the amplitude of a signal or current.

Audio Coverage Uniformity measurement locations (ACUML)   The test points within a venue that have been determined to carry out the measurements for the Audio Coverage Uniformity test.

Audio Coverage Uniformity Plan (ACUP)   A stand-alone document that identifies the Audio Coverage Uniformity measurement locations for a particular venue, using the AVIXA indication symbol.

audio processor   A device used to manipulate audio signals.

Audio Return Channel (ARC)   Introduced to the HDMI standard with version 1.4. ARC allows a display to send audio data upstream to a receiver or surround-sound controller, eliminating the need for a separate audio connection.

audio signal   An electrical representation of sound.

audio transduction   The process of converting acoustical energy into electrical energy or electrical energy back into acoustical energy.

Audio Video Bridging (AVB)   A standards-based audiovisual Data Link layer protocol defined under IEEE 802.1-AVB. It uses standard Ethernet cabling but requires AVB-enabled switches and network components. AVB does not require separate network infrastructure or dedicated bandwidth; AVB components automatically prioritize data. AVB was recently renamed Time-Sensitive Networking to reflect the standard’s applicability to communication among different types of devices, such as network sensors. See Time-Sensitive Networking (TSN).

audiovisual infrastructure   The physical building components that make up the pathways, supports, and architectural elements required for audiovisual technical equipment installations.

audiovisual rack   A housing unit for electronic equipment. The inside of a typical AV industry rack is 19 inches (482.6mm) wide. Many of the technical specifications for a rack, including size and equipment height, are determined by standards that have been established by numerous standard-setting organizations. The outside width of the rack varies from approximately 530mm to 630mm (21in to 25in).

authority having jurisdiction (AHJ)   An organization, office, or individual responsible for enforcing the requirements of a code or standard or for approving equipment, materials, installation, or procedures. In some places the authority having jurisdiction may be known as the regional regulatory authority.

automatic gain control (AGC)   A circuit that maintains a constant output gain in response to input variables such as signal strength or ambient noise level.

Automatic Private IP Addressing (APIPA)   A Windows function that assigns locally routable addresses from the reserved network 169.254.0.0/16 to devices that do not have or cannot obtain an IP address. This allows devices to communicate with other devices on the same LAN. APIPA operates at the Network layer of the OSI model and the Internet layer of the TCP/IP protocol stack.

balanced circuit   A two-conductor circuit in which both conductors and all circuits connected to them have the same impedance with respect to ground.

balun   Short for BALanced-to-UNbalanced, a device used to connect a balanced circuit to an unbalanced circuit. For example, a transformer used to connect a 300Ω television antenna cable (balanced) to a 75Ω antenna cable (unbalanced).

band   A grouping or range of frequencies.

bandwidth   1. A range of frequencies. 2. A measure of the amount of data or signal that can pass through a system during a given time interval.

bandwidth (networking)   The available or consumed data communication resources of a communication path, measured in bits per second (bps). It is also called data throughput or bit rate.

bandwidth limiting   The process of limiting the bandwidth of a signal, usually to allow the signal to be transmitted over a lower bandwidth path.

baseband   A signal that has not been modulated onto a higher frequency carrier.

benchmarking   The process of examining methods, techniques, and principles to establish a standard to which comparisons can be made.

bend radius   The radial measure of a curve in a cable, conductor, waveguide, or interconnect that defines the physical limit beyond which further bending has a measurable effect on the signal being transported.

bidirectional 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.

bill of materials (BOM)   A complete equipment list of components that must be procured in order to build the system as specified. The BOM also lists the costs associated with each aspect of designing and implementing the system.

bit   A contraction of the words binary digit. This is the smallest unit of digital information and may have the value 1 or 0.

bit depth   The number of bits used to specify a parameter.

bit error rate (BER)   The number of error bits present in a signal stream per unit of time.

bit rate   The measurement of the quantity of data transmitted over a digital signal stream, per unit of time. It’s measured in bits per second (bps).

block diagram   A diagram of a system or device in which the principal parts are represented by suitably annotated geometrical figures to show both the functions of the parts and their functional relationships.

Bluetooth   A wireless technology for low-cost, short-range radio links between devices. It operates in the 2.4GHz industrial, scientific and medical (ISM) frequency band.

BNC connector   A type of connector featuring a two-pin bayonet-type lock. The most common professional coaxial cable connector because of its reliability and ruggedness. It is used to transport signals such as, SDI, RF, video, and time code.

bonding   Joining conductive material by a low impedance connection, thus ensuring that they are at the same electrical potential.

boundary microphone   A microphone design where the diaphragm is placed close to a sonic “boundary” such as a wall, ceiling, or other flat surface. This arrangement prevents the acoustic reflections from the surface from mixing with the direct waveform and causing phase distortions. It is used in conference and telepresence systems.

branch circuit   The circuit conductors between the final overcurrent device protecting the circuit and the load connection.

breaker box   See panelboard.

broadcast domain   A set of devices that can send Data Link layer frames to each other directly, without passing through a Network layer device. Broadcast traffic sent by one device in the broadcast domain is received by all devices in the domain.

building information modeling (BIM)   A data repository for building design, construction, and maintenance data, shared by multiple disciplines on a single project.

bus   A wiring system that links multiple 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   A data word containing 8 bits, also known as an octet. The symbol for byte is B.

cable   An assembly of more than one conductor (wire).

cable tray   A structure to provide rigid continuous support for cables.

campus area network (CAN)   A type of network linking multiple LANs in a limited geographical area such as a university campus or a cluster of buildings.

candela   The unit of luminous intensity. A candela is the luminous intensity emitted by a reference point light source in a given direction. The symbol for candela is cd. The luminous intensity of a common wax candle is approximately 1 candela.

capacitance   The ability of a nonconductive material to store an electrical charge. Capacitance measured in farads (F). The symbol for capacitance is C.

capacitive reactance   The opposition a capacitive device offers to alternating current flow. It is measured in ohms (Ω). The symbol for capacitive reactance is X_C. Capacitive reactance is inversely proportional to the frequency of the current in a circuit.

capacitor   A passive electrical component in which plates of conductive material are separated by a dielectric. For a given capacitance value, expressed in farads, a capacitor will have a greater opposition to AC current flow at lower frequencies than at higher frequencies.

cardioid polar pattern   A 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 100Ω unshielded twisted-pair (UTP) cables and associated connecting hardware whose characteristics are specified for data transmission up to 100Mbps (part of the EIA/TIA 568A standard).

Category 5e (Cat 5e)   An enhanced version of the Cat 5 cable standard that adds specifications to reduce far-end crosstalk for data transmission up to 1Gbps (part of the EIA/TIA 568A standard).

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

Category 6A (Cat 6A)   A cable standard for 10 Gigabit Ethernet and other interconnections that is backward-compatible with Category 5, Cat 5e, and Cat 6 cable. Constructed using a mechanism to physically separate the twisted pairs, Cat 6A features more stringent specifications for alien and near-end crosstalk.

Category 7 (Cat 7)   A cable specification for 10 Gigabit Ethernet and other interconnections that is backward-compatible with Cat 5e and Cat 6A cable. To further reduce cross-talk, in Cat 7 cables each twisted-pair is shielded and the entire cable is shielded.

Category 8 (Cat 8)   A cable standard for 40 Gigabit Ethernet and other interconnections that is backward-compatible with Category 5e, Cat 6, and Cat 6A cable (part of the EIA/TIA 568A standard). Cat 8 features a shield around each twisted pair and a further shield enclosing all twisted pairs. It is only specified at 40Gbps for runs up to 30m (100ft).

cathode ray tube (CRT)   A high-vacuum glass tube containing an electron gun to produce the images seen on the phosphor-coated face of the tube. This video display technology was used in early-generation video monitors, television receivers, radar displays and oscilloscopes.

center tap   A connection point located halfway along the track or winding of an electronic device such as an inductor or resistor.

central cluster   A single source configuration of loudspeakers. In a central cluster, the sound is coming from one point in the room. The central cluster is normally located directly above (on the proscenium), and slightly in front of, the primary microphone location.

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

charged-coupled device (CCD)   A semiconductor light-sensitive 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, 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.

chroma   The saturation, or intensity, of a specific color. It is one of the three attributes that define a color; the other two are hue and value or luminance.

cliff effect   The sudden loss of digital signal reception. When a digital signal is carried too far on a cable, the eye pattern will collapse, and the signal will become unreadable.

clipping   The deformation of a 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.

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

CobraNet   CobraNet is a proprietary digital audio Data Link layer protocol designed by Cirrus Logic. It uses standard Fast Ethernet cabling, switches, and other components. CobraNet signals are non-routable.

codec   A contraction of the term coder/decoder. An electronic device or software process that encodes or decodes a data stream for transmission and reception over a communications medium.

collision domain   A set of devices on a local area network (LAN) whose packets may collide with one another if they transmit data at the same time.

color difference signal   A signal that conveys 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.

color rendering index (CRI)   The effect a light source has on the perceived color of objects, indexed against an incandescent source (CRI 100) of the same correlated color temperature.

color temperature   The quantification of the color of “white” light in reference to the light emitted by a standardized object at a specified temperature on the Kelvin scale. Measured in kelvins (K). Low color temperature light (~2000K) has a warm (reddish) look, while light with a high color temperature (>4000K) has a colder (bluish) appearance.

combiner   In a process called multiplexing, puts signals together onto one cable, constituting a broadband signal.

common mode   1. Voltage fed in phase to both inputs of a differential amplifier. 2. The signal voltage that appears equally and, in phase, from each current carrying conductor to ground.

common-mode rejection ratio (CMRR)   The ratio of the differential voltage gain to the common-mode voltage gain; expressed in decibels.

compander   An audio processing 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 signals—or more commonly, the Y, R-Y, and 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   1. An increase in density and pressure in air molecules. 2. A process that reduces data size.

compression ratio   Determines how much the volume on an audio compressor reduces depending on how far above the threshold the signal is.

compressor   A device that controls the overall amplitude of a signal by reducing the part of the signal that 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.

compressor threshold   Sets the point at which the automatic volume reduction kicks in. When the input goes above the threshold, an audio compressor automatically reduces the volume to keep the signal from getting too loud.

condenser microphone   Also called a capacitor microphone, a microphone that transduces sound into electricity using capacitive principles.

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

conduit   A circular tube that houses cable.

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

constant voltage   25V, 70V, 100V; a method of distributing signals to loudspeakers over a large area with less loss than a typical connection would provide. This can also be called a high impedance system.

Consumer Electronic Control (CEC)   A single-wire, bidirectional serial bus that uses AV link protocols to perform remote-control functions. It is an optional feature of the HDMI specification that allows for system-level automation when all devices in an AV system support it.

contact closure   A contact closure is the simplest form of remote-control communication. It is a switch. This type of control point operates a device by opening or closing an electrical current or voltage loop. It has the most basic protocol language: “on” (closed circuit) or “off” (open circuit).

content delivery network (CDN)   A distributed network of caching servers that can provide hosted unicast distribution of media for an organization. They are most often utilized by organizations whose content is in high demand.

contrast   Absolute difference in luminance between the peak white and black levels, where white and black luminance is displayed simultaneously.

contrast ratio   Describes the dynamic video range of a display device as a numeric relationship between the brightest color (typically white) and the darkest color (typically black) that the system is capable of producing. Two methods are used to specify contrast ratio; the full on/full off method describes the dynamic contrast ratio, and the ANSI measures the static contrast ratio.

control system   A system that controls subsystems such as audio, video, winches, drapes, lighting and atmospheric effects.

correlated color temperature (CCT)   The color appearance of a light source as compared with a standardized object heated to a temperature measured on the Kelvin scale. CCT is measured kelvins (K).

coverage pattern   The predictable pattern of sound energy that every loudspeaker emits. The coverage pattern is based on the frequency of the sounds and the physical size of the loudspeaker.

critical distance (Dc)   The point where sound pressure level of the direct reverberant sound field are equal.

critical path schedule   Reveals the interdependence of activities and assesses resource and time requirements and trade-offs. It also determines the project’s completion date and provides the capability to evaluate activity performance.

crossover   An electronic device that separates the frequency bands of an audio signal so that each driver in a multidriver loudspeaker system is sent only those frequencies that it will transduce accurately.

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.

current   The quantity of electrical charge flowing in a circuit, measured in amperes (A). The symbol for current is I.

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. Curvature of field is due to the lens design.

Dante   A proprietary digital audio Network layer protocol designed by Audinate. Dante sends audio information as Internet Protocol (IP) packets. It is fully routable over IP networks using standard Ethernet switches, routers, and other components. Dante controller software manages data prioritization and audio routes.

dB SPL   A measure of sound pressure level with reference to 0dB SPL, a sound pressure of 20 microPascal (µPA).

decibel (dB)   A base-10 logarithmic relationship of the ratio between two numbers. This is used for quantifying differences in voltage, distance, and sound pressure as they relate to power.

delay   A signal-processing device or circuit used to delay the speed of transmission of a signal.

demodulator   An 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 item farthest away.

detail drawing   A detail drawing enlarges small items to show how they must be installed. They depict items too small to see at the project’s typical drawing scale.

dielectric constant   Describes the ability of a material between two conductors to store an electrical charge. Dielectric strength is determined by the material’s type and thickness and is the amount of voltage that insulation can stand before it breaks down.

differential mode   1. Voltage fed out of phase to both inputs of a differential amplifier. 2. Signals measurable between or among active circuit conductors feeding the load but not between the equipment grounding conductor or associated signal reference structure and the active circuit conductors.

differentiated service (DiffServ)   A network quality-of-service strategy wherein data from specific applications or protocols are assigned a class of service. Flows assigned a high priority are given preferential treatment at the router, but delivery is not guaranteed.

diffusion   The scattering or random reflection of a wave from a surface.

digital media player   Devices that allow the playback of recorded or streamed audio and video content from media servers, the Internet, or local storage.

digital-only token (DOT)   A digital flag that is embedded onto digital sources, such as Blu-ray discs. Its purpose is to limit the availability or quality of HD content on the component output of a media player.

digital signage   Customized content shown on strategically located displays intended to attract specific types of viewers. It is sometimes referred to as dynamic signage to differentiate it from large-format static signs. Digital signage is displayed on LCD and LED panels, kiosks, and projection screens. These displays are placed in public spaces, museums, stadiums, corporate and educational buildings, retail stores, hotels, restaurants, and other locations.

digital signage media player   A hardware device or computer server used to store and forward or play back digital signage content on display screens. Some commercial digital signage displays have integrated media players on a chip. Digital signage players are often located in close proximity to the display screen but may also be located remotely. Network-ready media players enable the control and management of content remotely.

digital signage template   Customizable layouts used for standardizing content across all displays on the network. They enable multiple messages or content from multiple sources to be displayed on a screen by presenting the information in zones.

digital signal processor (DSP)   Combines processor functions such as mixers, limiters, and equalizers, typically into a single device.

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

direct couple   A loudspeaker system in which the amplifier is connected directly to the voice coil wires of the loudspeaker.

direct current (DC)   Electricity that maintains does not reverse direction, unlike alternating current (AC).

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

direct view display   Houses the light-producing elements and screen in one piece of equipment.

directivity   The specific coverage pattern that designers must consider when determining the placement of loudspeakers required to provide full coverage for all the listeners within a space.

dispersion   An effect that 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.

Display Data Channel (DDC)   The data channel used between video sources and video displays to carry information about display capabilities and video formats. The channel used for exchanging EDID and HDCP data.

DisplayID   A standard developed by VESA outlining how video display data is structured to describe its performance and capabilities when communicating with other devices. By structuring data in a flexible, modular way, DisplayID enables devices to identify new display resolutions, refresh rates, audio standards, and other formats as they become available. For example, the standard can support a single image segmented across tiled displays using multiple video processors.

DisplayPort   A digital display interface used to connect a video source to a display device. It can also carry audio, USB, and other data. It is backward compatible with HDMI and DVI signals.

distributed sound system   A sound system using multiple distributed loudspeakers to provide sound coverage across an area at a constant sound pressure level.

distribution amplifier (DA)   An active device used to split one input signal into multiple isolated output signals at a constant level.

diversity receiver   An RF receiver that uses multiple antennas to receive a single RF transmission. The receiver calculates phase differences between the received signals to dynamically shift between antennas to avoid multipath signal cancellation.

DLP   Digital Light Processing. A projection technology based on the MEMS digital micromirror device (DMD) chip family. It uses a matrix of thousands of movable microscopic mirrors on a chip to display images on a screen.

Domain Name System (DNS)   A hierarchical, distributed database that maps names to data such as IP addresses, name server addresses, and mail exchange addresses.

dome   A type of loudspeaker driver construction. Fabric or woven materials are used to create a dome-shaped diaphragm. The voice coil is attached to the edge of the diaphragm.

driver   In audio, an individual loudspeaker unit.

dual channel   In test equipment, refers to a test device with two independent input channels.

DVD   Digital Video Disc or Digital Versatile Disc. An optical storage medium for data or video.

DVI   Digital Visual Interface. A digital interface to connect an uncompressed video source to a display device. DVI has largely been replaced by HDMI, DisplayPort, and other formats.

Dynamic Host Configuration Protocol (DHCP)   A management process that automates the assignment of IP addresses and networking parameters to devices on an IP network.

dynamic microphone   A microphone with a diaphragm attached to a moveable coil of wire located in a magnetic field. Sound pressure waves cause the diaphragm to move the coil in the magnetic field, inducing a small electric current in the coil.

dynamic range   The difference between the loudest and quietest levels of a signal. Usually expressed in decibels (dB).

early reflected sound   Sound waves that 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.

earthing conductor   A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes.

echo   A reflected version of sound energy acoustically, or duplicated version of a signal electronically, that arrives to the listener with sufficient delay and separation from the original signal to allow the delayed signal to be perceived distinctly and later in time from the original signal.

echo cancellation   A means of eliminating echo from an audio path.

electret microphone   A type of condenser microphone using a prepolarized material, called an electret, which is applied to the microphone’s diaphragm or backplate.

electrical service   The conductors and equipment for delivering energy from the electricity supply system to the wiring system of the site served.

electromagnetic interference (EMI)   Improper operation of a circuit (noise) due to the effects of interference from electric and/or magnetic fields.

elevation drawing   A side view of an object or surface taken in the vertical plane, from outside the object or surface.

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.

energy management plan (EMP)   A document that details a systematic approach to implementing the most effective power consumption methods and procedures to achieve and maintain optimum energy usage.

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 (EGC)   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.

equivalent acoustic distance (EAD)   The farthest distance one can go from the source without the need for sound amplification or reinforcement to maintain good speech intelligibility. It is a design parameter dependent on the level of the presenter and the noise level in the room.

ergonomics   Also known as human factors or human factors engineering. This is the scientific study of the way people interact with a system. It focuses on effectiveness, efficiency, reducing errors, increasing productivity, improving safety, reducing fatigue and stress, increasing comfort, increasing user acceptance, increasing job satisfaction, and improving quality of life.

Ethernet   A set of network cabling, signaling, and network access protocol standards employing carrier-sense multiple access technology with collision detection (CSMA/CD).

EtherSound   A proprietary digital audio Data Link layer protocol designed by Digigram. It uses standard 100Mbps or 1Gbps Ethernet cabling, switches, and other components. It requires a separate network with dedicated bandwidth. EtherSound signals are nonroutable.

expander   An audio processor that comes in two types: a downward expander and as part of a compander.

extended display identification data (EDID)   A data structure within a sink that is used to describe the sink’s capabilities to a source. These capabilities include native resolution, color space information, and audio type (mono or stereo).

external configuration   Refers to the ability of one device to configure other devices and subsystems.

far field   The sound field distant enough from the sound source so the SPL decreases by 6dB for each doubling of the distance from the source.

farthest viewer   The viewer positioned at the farthest distance from the screen as defined by the viewing area.

feedback   1. In audio, 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, such as on or off.

feedback stability margin (FSM)   Extra margin, added into the needed acoustic gain formula, that represents extra gain that a sound system may need. It is the possibility of feedback due to the nonlinearity across the frequency band of a sound system.

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

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

filter   Blocks or passes certain frequencies from a signal.

firewall   Any technology, hardware, or software that protects a network by preventing intrusion by unauthorized users and/or regulating traffic permitted to enter or exit the network. A firewall controls what traffic may pass through a router connecting one network to another. Firewalls control access across any network boundaries, including between an enterprise network and the Internet or between local area networks (LANs) within an enterprise.

firmware   A type of software that has been permanently stored in a piece of hardware.

fixture   A luminaire that is mounted or fixed in place.

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

focal length   The distance, in millimeters, between the center of a lens and the point where the image comes into focus. The shorter the focal length, the wider the angle of the image will be.

foot-candle   The US customary unit of illuminance. The incident light measured when one lumen of light is spread over an area of one square foot. Its symbol is fc. 1 foot-candle = 10.76 lux.

footlambert (fl)   The footlambert (fl) is a U.S. customary unit of measurement for luminance. It is equal to 1/π candela per square foot.

frame rate   The number of frames sent from a display source per second.

frequency   The number of complete cycles in a specified period of time. It is measured in hertz (Hz). 1Hz = 1 cycle per second.

frequency domain   A signal viewed as amplitude versus frequency is in the frequency domain. This allows you to view the amount of energy present at different frequencies.

frequency response   The amplitude response versus frequency for a given device.

Fresnel lens   A flat 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. A Fresnel lens is often used for the condenser lens in overhead projectors, in rear-screen projection systems, and in Fresnel spotlights.

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.

full-duplex communication   A form of bidirectional data transmission in which messages may simultaneously travel in both directions.

full HD   A high-definition video mode with a resolution of 1920×1080 pixels.

fundamental frequency   Known as pure tone, the lowest frequency in a harmonic series.

gain   1. Electronic signal amplification. 2. The ability of a projection screen to concentrate light.

gain control   A gain control is an electronic adjustment through which the operator can increase or decrease the amplitude of a defined signal element.

gain-sharing automatic mixers   A gain-sharing automatic mixer is an audio mixer that automatically turns up microphone channels that are in use and turns down microphone channels that are not being used.

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

gated automatic mixer   An audio mixer that turns microphone channels either “on” or “off” automatically.

gateway   The highest router in the hierarchy of routers. It connects a local network to an outside network, and all traffic must travel through it. A gateway will pass traffic to the routers below, and the routers below look to the gateway to find names (DNS addresses) that are not found on the local network.

gauge   A thickness or diameter of a wire.

genlock   To lock the synchronization signals of multiple devices to a single source.

graphic equalizer   Equalizer with an interface that has a graph comparing amplitude on the vertical axis with frequency on the horizontal.

graphical user interface (GUI)   Often pronounced “gooey”; provides a visual representation of the system features and functions.

graphics adapter   Commonly referred to as a video card, outputs computer video signals.

graphics processing unit (GPU)   A specialized circuit designed for processing display functions. The processor is optimized to render and manipulate images in a video frame buffer.

grayscale   The brightness and darkness of a color. It is sometimes called value. It is one of the three attributes of color; the other two are hue and chroma.

grayscale test pattern   A pattern that displays a known range of values between black and white on the screen.

ground   1. The earth. 2. In the context of an electrical circuit, the earth or some conductive body that extends the ground (earth) connection. 3. In the context of electronics, the 0V (zero volt) circuit reference point. This electronic circuit reference point may or may not have a connection to earth.

ground fault   1. An unintentional, electrically conducting connection between an ungrounded conductor of an electrical circuit and a normally noncurrent-carrying conductor, metallic enclosure, metallic raceway, metallic equipment, or earth. 2. The electrical connection between any ungrounded conductor of the electrical system and any noncurrent-carrying metal object.

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.

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 de-energizes a circuit (or a portion of that circuit) within an established period of time when a current to ground exceeds a specified level. Similar in function to an earth leakage circuit breaker (ELCB), a residual current device (RCD), or a core balance relay (CBR).

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   Connecting to ground or to a conductive body that extends the ground connection. The connected connection is referred to as grounded.

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

grounding electrode   A conducting object through which a direct connection to earth is established.

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.

group management protocol (GMP)   Allows a host to inform its neighboring routers of its desire to start or stop receiving multicast transmissions. Without a GMP, multicast traffic is broadcast to every client device on the network segment, impeding other network traffic and overtaxing device CPUs.

group of pictures (GoP)   A set of successive frames that are required to display a complete series in a digital video signal. It includes the visible picture, timing/sync information, and compression frames.

half-duplex   A form of data transmission in which only one network node at a time sends data.

harmonic distortion   Signal distortion that arises when harmonics of an input signal are produced during processing and appear in the output together with the processed input signal.

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

HD-15 connector   HD-15 connector, sometimes called a VGA connector, is a video connector that is typically associated with the output of a computer graphics card. It has three rows of five pins, which carry analog red, green, blue, and sync signals along with display data channel information.

HDbaseT   A connectivity standard for the transmission of, high definition video, audio, DC power, Ethernet, and serial signaling including USB and other protocols, over standard twisted-pair cables such as Cat 5e and above.

HDCP key   A long number that a program uses to verify authenticity and encode/decode content. HDCP processes use multiple types of keys. These keys are strongly protected by Digital Content Protection, LLC.

HDCP receiver   A device that can receive and decode the HDCP signals. A television is an example of a receiver.

HDCP repeater   A device that can receive HDCP signals and transmit them to another device, such as a switcher or distribution amplifier.

HDCP sink   A device that receives and decodes the HDCP signals.

HDCP source   A device that sends HDCP-encoded signals and content.

HDCP transmitter   A device that can send HDCP-encoded signals and content. A Blu-ray Disc player is an example of an HDCP transmitter.

HDMI Ethernet Audio Control (HEAC)   In HDMI, the combining of HDMI Ethernet Channel (HEC) and Audio Return Channel (ARC) into one port or cable. See HDMI Ethernet Channel (HEC) and Audio Return Channel (ARC).

HDMI Ethernet Channel (HEC)   Consolidates video, audio, and data streams into a single HDMI cable. A dedicated data channel enables high-speed, bi-directional networking to support future IP solutions and allow multiple devices to share an Internet connection.

HDTV   High-definition television. Generally includes image definitions above 1280×720 pixels.

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.

heat load   Heat load is the heat that is generated and released by a piece of electronic equipment. It is measured in British thermal units.

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. This pattern is used for boundary microphones.

hertz (Hz)   The unit of frequency. 1Hz = 1 cycle per second.

High-Bandwidth Digital Content Protection (HDCP)   A form of encryption developed by Intel to control digital audio and video content as it travels across Digital Video Interface (DVI) or High Definition Multimedia Interface (HDMI) connections. It prevents transmission or interception of unencrypted HD content.

High Definition Multimedia Interface (HDMI)   A point-to-point connection between video devices for all-digital video and audio. HDMI signals include audio, control, and digital asset rights management information. It is fully compatible with DVI.

high dynamic range (HDR)   Digital images having a bit depth of at least 10 bits (1024 levels) per channel. Standard dynamic range images have a bit depth of 8 bits (256 levels) per channel.

high-pass filter   A circuit that allows signals above a specified frequency to pass unaltered while simultaneously attenuating frequencies below the specified limit.

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

horn   A loudspeaker that reproduces mid to high frequencies.

hot plug   A low-level signal sent by a source that indicates whether a sink or display is connected.

hue   The attribute of a color that represents a red, a purple, a green, and so on. It is one of the three attributes that define color; the other two are grayscale and chroma.

hum   Undesirable 50 to 60Hz noise emanating from a sound system or evidenced by a rolling hum bar on a display.

IEEE   The Institute of Electrical and Electronics Engineers.

illuminance   The amount of light falling on a surface, measured in lux (lx) or foot-candle (fc). 1 foot-candle = 10.76 lux.

image constraint token (ICT)   A digital flag signal incorporated into some high-definition digital video streams. If present, the video stream can be decoded at full-resolution only on HDCP-enabled devices.

image resolution   Image resolution is the total number of pixels in the image. It is normally expressed as the number horizontal pixels multiplied by the number of vertical pixels.

imager   A light-sensitive electronic device behind a camera’s lens, usually made up of thousands of sensors which convert the light input into an electrical output.

impedance   The total opposition to that a circuit presents to an alternating current. It includes resistance (R), inductive reactance (X_R) and capacitive reactance (X_C). Impedance is measured in ohms (Ω). Its symbol is Z.

impedance matching   Having an impedance value on an input that an output is expecting. It does not necessarily mean having comparable impedances on an input and an output.

impedance meter   Device used to measure the impedance of an electrical circuit.

inductance   The magnetic property of a circuit that opposes any change in current, represented by the symbol L and measured in henrys (H).

induction   The influence exerted on a conductor by a changing magnetic field.

inductive reactance (X_L)   Opposition to the current flow offered by the inductance of a circuit. Inductive reactance is measured in ohms (Ω). Its symbol is X_L. The inductive reactance in a circuit is directly proportional to the frequency of the current.

InfoFrames   Structured packets of data that carry information regarding aspects of audio and video transmission, as defined by the EIA/CEA-861B standard. Using this structure, a frame-by-frame summary is sent to the display, permitting selection of appropriate display modes automatically. InfoFrames typically include auxiliary video information, generic vendor-specific source product description, MPEG, and audio information.

infrared (IR)   The range of light frequencies below the red end of the visible spectrum. IR signal transmission requires an uninterrupted line-of-sight between transmitter and receiver.

input   A connection point that receives information from another piece of equipment.

I/O port   Input and/or output port. A connection port on a device for handling input and/or output signals, frequently in a digital format.

insulation   A material of high dielectric strength used to isolate the flow of electric current between conductors.

Integrated Services Digital Network (ISDN)   A communications standard for transmitting data over digital telephone lines.

intelligibility   A sound system’s ability to produce an accurate reproduction of sound, allowing listeners to identify words and sentence structure.

Internet Corporation for Assigned Names and Numbers (ICANN)   A nonprofit organization chartered to oversee several Internet-related tasks. ICANN manages Domain Name System (DNS) policy, including the top-level domain space for the Internet.

Internet Group Management Protocol (IGMP)   The IPv4 group management protocol. IGMPv1 allowed individual clients to subscribe to a multicast channel. IGMPv2 and IGMPv3 added the ability to unsubscribe from a multicast channel.

interlaced scanning   The scanning process that alternately displays the odd and even lines of a video frame to construct a full frame of video signal.

internal configuration   Refers to the setup and customization of management or control device.

Internet of Things (IoT)   Refers to scenarios where network connectivity and computing capability extends to objects, sensors and everyday items not normally considered computers, allowing these devices to generate, exchange and consume data.

Internet Protocol (IP)   A TCP/IP protocol defined in the IETF standard RFC 791. IP defines rules for addressing, packaging, fragmenting, and routing data sent across an IP network. IP falls under the Internet layer of the TCP/IP protocol stack and the Network layer of the OSI model.

Internet Protocol Television (IPTV)   A system that delivers television services over a packet-switched network such as a LAN or the Internet.

inverse square law   The 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.

IoT   See Internet of Things.

IP   See Internet Protocol (IP).

IR   See infrared (IR).

isolated ground (IG)   An equipment grounding method permitted by the NEC for reducing electrical noise (electromagnetic interference) on the grounding circuit. The isolation between IG receptacles and circuits and the normal equipment grounding is maintained up to the point of the service entrance (or a separately derived system) where the grounded (neutral) conductor, equipment grounding, and isolated equipment grounding conductor are bonded together and to earth ground.

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.

isolated receptacle   A receptacle in which the grounding terminal is purposely insulated from the receptacle mounting means. Isolated receptacles are identified by a triangle engraved on the face and are available in standard colors. The receptacle (and so the equipment plugged into the receptacle) is grounded via an insulated grounding conductor.

jacket   Outside covering used to protect cable wires and their shielding.

junction box   A metal or plastic enclosure for enclosing the junction of electrical wires and cables. A junction box can be used as a termination point with a custom connector plate or interface plate. A junction box can also be installed and used as a pull box for longer cable runs.

keystone error   The trapezoidal distortion of an image due to the projection device being at an angle to the plane of the screen.

lamp   The light source in a luminaire.

latency   Response time of a system. The delay between an input being received a system and the corresponding output being received. Measured in seconds (s).

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

Law of Conservation of Energy   States that energy cannot be created or destroyed. Energy can be transformed from one form to another and transferred from one body to another, but the total amount of energy remains constant.

lenticular screen   A screen surface characterized by silvered or aluminized embossing, designed to reflect maximum light over wide horizontal and narrow vertical angles.

lighting fixture   A lighting instrument or luminaire.

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

limiter ratio   Defines how much the limiter will compress signals that exceed its threshold. The limiter compresses only the portion of the signal that exceeds its threshold, after the signal has already passed through the compressor.

limiter threshold   Defines which portions of the signal the limiter will affect. All decibel levels below or equal to the threshold will pass through the limiter unchanged. All signals above the threshold will be compressed.

line driver   An amplifier used to compensate for signal attenuation created by cable resistance over longer cable runs.

line level   The specified strength of an audio signal used to transmit analog audio between the elements of an audio system. Generally this is considered to be approximately 1V at 1kHz into a 600Ω impedance.

liquid crystal display (LCD)   A video display that uses liquid crystals to produce an image. These devices do not emit light directly.

liquid crystal on silicon (LCoS)   A reflective, fixed-resolution LCD imaging technology. LCoS panels resemble LCD panels in size and function. A liquid crystal layer is applied inside an LCoS panel to a reflective complementary metal-oxide semiconductor (CMOS) mirror substrate. The LCoS chip has a fixed matrix of pixels, each backed by a mirrored surface.

listed   Equipment, materials, or services included in a list published by a nationally recognized testing laboratory, such as the US Underwriters Laboratories (UL), that is acceptable to the authority having jurisdiction (AHJ).

load center   An electrical industry term used to identify a lighting and appliance electrical distribution board in residential and light-commercial applications.

local area network (LAN)   A computer network connecting devices within a confined geographical area, such as a building or living complex.

local monitor   A local device used to monitor the output signal from a system.

logarithm   The exponent of 10 that equals the value of a number.

logic network diagram   A project management tool that aids in sequencing and ultimately scheduling a project’s activities and milestones. It represents a project’s critical path as well as the scope for the project.

lossless compression   A process that compresses data without losing any information.

lossy compression   A form of compression that produces an approximation of the original data by eliminating non-critical or redundant information.

loudspeaker   A transducer that converts electrical energy into acoustical energy.

loudspeaker circuit   A group of wired loudspeakers.

low-pass filter   A circuit that allows signals below a specified frequency to pass unaltered, while simultaneously attenuating frequencies above the one specified.

low voltage   An ambiguous term. It may mean less than 70V AC to an AV technician, 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   The unit of luminous flux. A measure of the total quantity of visible light emitted from light source per unit of time. Its symbol is lm.

luminaire   A complete lighting instrument. Comprised of light source, optical system, housing and mounting mechanism.

luminance (Y)   Also called luma, part of a bandwidth-limited video signal combining synchronization information and brightness information. Its symbol is Y.

lux   The international unit of illuminance. The incident light measured when one lumen of light is spread over an area of one square meter. Its symbol is lx. 10.76 lux = 1 foot-candle.

MAC address   The actual hardware address, or number, of an NIC device. Each device has a globally unique Media Access Control (MAC) address to identify its connection on the network.

mains buzz   A mixture of higher-order harmonics of the 50Hz or 60Hz noise (hum) originating from the AC mains power system and audible in a sound system.

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

matrix switcher   An electronic switching device with multiple inputs and outputs. The matrix allows any input to be connected to any one or more of the outputs.

matte-white screen   A screen that uniformly disperses light, both horizontally and vertically, creating a wide viewing cone and wide viewing angle.

maximum transmission unit (MTU)   The size in bytes of the largest frame that can pass over a Data Link layer connection. Any header information must be included within the MTU.

mechanical switcher   A switch that mechanically connects circuit elements. It functions like a wall switch, meaning there is a mechanical connection or disconnection.

MEMS   See microelectromechanical systems (MEMS).

MEMS microphone   A microphone built using MEMS technology. Generally MEMS implementations of either condenser or piezo-electric microphones.

mesh topology   A network where each node is connected via bridges, switches, or routers to at least one other node.

metropolitan area network (MAN)   A communications network that covers a single geographic area, such as a suburb or city.

mic level   The very low-level signal from a microphone. Typically only a few millivolts.

microphone sensitivity   A specification that indicates the electrical output of a microphone when it is subjected to a known sound pressure level. Usually measured in dBV/Pa.

microelectromechanical systems (MEMS)   Mechanical devices built directly onto silicon chips using the same fabrication processes as microprocessors and memory systems. Best known as the digital micromirror devices (DMD) used for light switching in DLP projectors.

middleware   Software that provides services to applications that aren’t available from the operating system. In a streaming system, for example, middleware may perform transcoding, compression, or remote access authentication.

midrange   A loudspeaker that reproduces midrange frequencies, typically 300Hz to 8kHz.

milestone   A significant or key event in the project, usually the completion of a major deliverable or the occurrence of an important event. It can often be associated with payment milestones, and client approvals.

millwork   Carpentry work produced in a mill. Usually refers to finished woodwork such as doors, molding, trim, flooring, and wall paneling.

mixer   A device for blending multiple signal sources.

mix-minus system   A type of speech reinforcement system that allows both meeting presenters and participants to be heard. Each loudspeaker is given a separate subsystem, which mixes the microphone signals, minus the closest microphone.

Mobile High-Definition Link (MHL)   A standard audio/video interface for connecting mobile electronics to high-definition televisions and audio receivers. The most recent version, superMHL, is capable of 36Gbps and HDR video up to 8K at 120fps.

modular connector   A connector used with four, six, or eight pins. Common modular connectors are RJ-11 and RJ-45 (8P8C).

modulator   A device that varies one or more properties of a carrier signal (frequency, amplitude, phase) with information from another signal.

Multicast Listener Discovery (MLD)   The IPv6 group management protocol. Multicast is natively supported by IPv6; any IPv6 router will support MLD. MLDv1 performs roughly the same functions as IGMPv2, and MLDv2 supports roughly the same functions as IGMPv3.

multicast streaming   A one-to-many transmission, meaning one server sends out a single stream that can then be accessed by multiple clients. Class D IP addresses are set aside for multicast transmissions.

multimeter   A test instrument with multiple ranges for measuring current, voltage, and resistance. Many instruments also include a simple continuity test capability.

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

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

Multi-Protocol Label Switching (MPLS)   A networking protocol that allows any combination of Data Link layer protocols to be transported over any type of Network layer. MPLS routes data by examining each packet’s MPLS label without examining packet contents. Implementing MPLS improves interoperability and routing speed.

native resolution   The number of 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   The sound field close to the sound source that has not been colored by room reflections. This is also known as direct sound.

needed acoustic gain (NAG)   The gain the sound system requires to achieve an equivalent acoustic level at the farthest listener equal to what the nearest listener would hear without sound reinforcement.

needs analysis   A needs analysis identifies the activities that the end users need to perform, then develops the functional descriptions of the systems that support those needs.

Network Address Translation (NAT)   Any method of altering IP address information in IP packet headers as the packet traverses a routing device. NAT is typically implemented as part of a firewall strategy. The most common form of NAT is Port Address Translation (PAT).

network bridge   Connects two different types of networks. It translates one network protocol to another protocol. An example of a bridge is a computer modem. A cable modem converts, or bridges, the Ethernet protocol to a cable TV protocol.

network interface card (NIC)   An interface that allows you to connect a device to a network. Many NICs are now integrated into the device’s main circuitry.

network segment   A network segment is any single section of a network that is physically separated from the rest of the network by a networking device such as a switch or router. A segment may contain one or more hosts.

network switch   Connects multiple devices so they can communicate with the other devices that are also connected to the switch. As each device is connected, the switch collects and stores the MAC address of the device that it communicates with. When one device wants to communicate with a second device, the switch looks up the destination device’s location in its memory and then sends the information to its destination.

network topology   The physical arrangement of the elements connected to a network.

neutral conductor   The conductor in an electrical supply system that is connected to the earth/ground for current return. This is not part of the protective earth/grounding system. Also see grounded conductor for US usage.

nit   The metric unit for screen or surface brightness.

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

noise criterion (NC) rating   Developed to establish satisfactory conditions for speech intelligibility and general living environments. Measurements are taken at eight center octave frequencies from 63Hz to 8kHz and plotted against a standardized curve.

noise-masking system   Introduces background noise to hinder communication and increase privacy. These are also sometimes called sound-masking or speech-privacy systems.

noisy ground   An electrical connection to a ground point that produces or injects spurious voltages into the computer system through the connection to ground (IEEE Std. 142-1991).

nominal impedance   The low point in the usable frequency area in a loudspeaker.

notch filter   A filter that notches out, or eliminates, a specific band of frequencies.

number of open microphones (NOM)   Takes into account the increased possibility of feedback by adding additional live microphones in a space. Each time the number of open microphones is doubled, you lose 3dB of gain before feedback.

Nyquist-Shannon Sampling Theorem   States that an analog signal can be reconstructed if it is encoded using a sampling rate that is greater than twice the highest frequency sampled. For example, since the range of human hearing extends to 20kHz, the sampling rate for digital audio should be greater than 40kHz.

octave   A band, or group, of frequencies. The relationship of the frequencies is such that the lowest frequency is half the highest. 200Hz to 400Hz is an octave, 4kHz to 8kHz is an octave, and so on.

Ohm’s law   A law that 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, where I is the current (in amps), V is the voltage (in volts), and R is the resistance (in ohms).

omnidirectional   Describes the pattern for devices have equal signal sensitivity 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.

organic light-emitting display (OLED)   Consists of layers of organic compounds that emit light when an electric current flows through it. There are separate organic layers for red, green, and blue.

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

OSI model   Open Systems Interconnection model. This is a reference model developed by ISO in 1984, as a conceptual framework of standards for communication in the network across different equipment and applications by different vendors. Network communication protocols fall into seven categories, or layers.

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

overcurrent protection device   A safety device designed to open a circuit if the current reaches a predetermined value. Examples are circuit breakers and fuses.

packet filtering   A technique that uses rules to determine whether a data packet will be allowed to pass through a firewall. Rules are configured by the network administrator and implemented based on the protocol header of each packet.

panelboard   The North American name for an electrical load distribution board.

parallel circuit   A circuit in which the voltage is the same across each load, but the current divides and takes all the available paths and returns to the source.

parametric equalizer   Allows discrete selection of a center frequency and adjustment of the width of the frequency range that will be affected. This can allow for precise manipulation with minimal impact of adjacent frequencies.

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.

peaking control   Electronic adjustments within a video component that can be used to compensate for system losses, particularly in cable capacitance.

permissible area   The maximum amount of space that cables should occupy inside the conduit.

personal area network (PAN)   A limited-range wireless network that serves a single person or small workgroup.

phantom power   A DC power supply delivered as an “invisible” overlay on the signal wires of a system. In audio phantom power systems, a voltage is overlaid on microphone signal lines to enable the remote powering of devices such as condenser microphones and active direct input boxes.

phase   A particular value of time for any periodic function. For a point on a sine wave, it is a measure of that point’s distance from the most recent positive-going zero crossing of the waveform. It is measured in degrees; 0 to 360 degrees is a complete cycle.

phono connector   The international name for the type of coaxial connector known as RCA in North America.

phosphor   A substance that produces light when stimulated by radiation. Phosphors are used to produce some colors of visible light in fluorescent lamps, LED sources, some laser light sources and in CRT and plasma displays.

pink noise   A signal with a broad spectrum of random frequencies that has equal energy in each octave band.

pink noise generator (PNG)   A device to generate pink noise. An audio PNG is commonly used in conjunction with an audio spectrum analyzer to evaluate and align a sound system in an environment.

pixel   A contraction of the words picture and element. The smallest element used to build a digital image.

plan view   A drawing of a space from the “top view,” taken directly from above. Examples include a floor plan and site plan.

plane of screen   Identification of image position on a plan or drawing relative to other plotted locations. It is a notional line, whether in plan view or elevation, that aligns with the front surface of the screen (that is, image position) used as a datum to define viewers’ relative positions.

plasma display panel (PDP)   A direct-view display technology consisting 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.

playback system   A system designed specifically to play back recorded material.

plenum space   The plenum space is also called environmental air space. It is an area connected to air ducts that forms part of the air distribution system.

point source   A sound system that has a central location for the loudspeakers, mounted high above, intended to cover a large area. This type of sound system is typically used in a performance venue or a large house of worship.

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

polar pattern   Also known as pickup pattern, the shape of the area that a microphone will be most sensitive to sound.

polar plot   A polar plot is a graphical representation of the relationship between a device’s directionality and its output.

port   1. In a TCP/IP network, a 16-bit number included in the TCP or UDP Transport layer header. The port number typically indicates the Application layer protocol that generated a data packet. A port may also be called by its associated service (e.g., port 80 may be called HTTP, or port 23 may be called telnet). 2. To move an application to a new platform.

Port Address Translation (PAT)   A method of Network Address Translation (NAT) whereby devices with private, unregistered IP addresses can access the Internet through a device with a registered IP address. Unregistered clients send datagrams to a NAT server with a globally routable address (typically a firewall). The NAT server forwards the data to its destination and relays responses to the original client.

post tension type construction   A type of structure that uses metal cables embedded within the concrete slab to support the structure. The cables act as a suspension support system that allows for wider spacing of columns within a building.

potential acoustic gain (PAG)   The potential gain that can be delivered by the sound system without ringing and before feedback occurs. It is based upon the number of open microphones and the distances between sources (like a presenter) and microphones, microphones and loudspeakers, and listeners and loudspeakers.

power   Energy expended in one form manifesting itself into another form: motion, heat, or light. This is power, or the rate at which work is done. Power is measured in watts (W). The symbol for power is P.

power amplifier   Boosts the audio signal enough to move the loudspeakers.

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

power distribution unit (PDU)   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 sequencing   The act of powering on and off equipment that often requires warm-up or cool-down time. Sequencing also helps prevent tripping circuit breakers by limiting the excessive surge of electricity when devices are first turned on.

preamplifier   An amplifier that boosts a low-level electronic signal before it is sent to other processing equipment.

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

program report   A document that describes the client’s specific needs, system purpose and functionality, and the designer’s best estimate of probable cost, in a nontechnical format for review and approval by the owner. This is also known as the AV narrative, or discovery phase report, return brief, or concept design report.

progressive scanning   Scanning that traces the image’s scan lines sequentially, such as with an analog computer monitor.

Protocol Independent Multicast (PIM)   Allows multicast routing over LANs, WANs, or even, theoretically, the open Internet. Rather than routing information on their own, PIM protocols use the routing information supplied by whatever routing protocol the network is already using; that’s why it’s protocol independent.

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

pure tone   See fundamental frequency.

Q factor   The quality factor of an audio filter is the ratio of the height of the center frequency of the filter compared with the bandwidth of the filter at the 3dB point.

quality of service (QoS)   Any method of managing data traffic to preserve system usefulness and provide the best possible user experience. Typically, QoS refers to some combination of bandwidth allocation and data prioritization.

quiet ground   A point on a ground system that does not inject spurious voltages into the computer system. There are no standards to measure how quiet a quiet ground is.

raceway   An enclosed channel of metal or nonmetallic materials designed for holding wires, cables, or busbars, with additional functions.

rack   See equipment rack.

rack elevation diagram   A rack elevation diagram is a pictorial representation of the front of a rack and the location of each piece of equipment within that rack, typically labeling the number of RUs used for each piece of gear.

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

radio frequency (RF)   The portion of the electromagnetic spectrum that is suitable for radio communications. Generally, this is considered to be from 10kHz up to 300MHz. This range extends to 300GHz if the microwave portion of the spectrum is included.

radio frequency interference (RFI)   Radiated electromagnetic energy that interferes with or disturbs an electrical circuit.

rarefaction   A decrease of density and pressure in air molecules.

ratio   A mathematical expression that represents the relationship between the quantities of numbers of the same kind. A ratio is typically written as X:Y or X/Y.

RCA connector   The North American name for the phono connector, a coaxial connector most often used with line-level audio signals and consumer composite video signals.

reactance   Opposition to alternating current resulting from capacitance and inductance in the circuit. Measured in ohms (Ω). The symbol for reactance is X.

rear-screen projection   A system in which the image is projected toward the audience through a translucent screen material, for viewing from the opposite side.

reference level   In the context of decibel measurements, the reference level is the established starting point represented by 0dB. The reference level varies according to linear unit and application.

reference point   The point of no potential used as the 0V (zero volt) reference for a circuit.

reflected ceiling plan   Used to illustrate elements in the ceiling with respect to the floor. It should be interpreted as though the floor is a mirrored surface, reflecting the features within the ceiling.

reflecting server   Takes in a unicast stream and broadcasts out a multicast stream. It is often used for live data streams.

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.

refresh rate   The number of times per second a display device will update the display of a received image.

release time   The release time of an audio compressor determines how quickly the volume increases when an audio signal returns below the threshold.

relocatable power tap   A North American cord-connected product rated 250V AC or less and 20A or less with multiple receptacles. This tap is intended only for indoor use and plugged directly into a branch circuit. It is not intended to be connected to another relocatable power tap.

reserve DHCP   A hybrid approach to IP addressing. Using reserve DHCP, a block of addresses is set aside for devices requiring a static IP address. The remaining IP addresses in the subnet pool are assigned dynamically using DHCP.

residual current device (RCD)   A safety device that de-energizes a circuit (or a portion of that circuit) within an established period of time when a current to ground exceeds a specified level. Similar in function to an earth leakage circuit breaker (ELCB), a ground-fault circuit interrupter (GFCI), or a core balance relay (CBR).

resistance   The property of a material to impede the flow of electrical current. Measured in ohms (Ω). The symbol for resistance is R.

resistor   A passive electrical device that produces opposition to current flow. Current passes through a resistor in direct proportion to voltage, independent of frequency. The relationship between voltage across, and current through, a resistor is defined in Ohm’s law.

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

reverberant sound   Sound waves that bounce off multiple surfaces before reaching the listener but arrive at the listeners’ ears quite a bit later than early reflected sound.

reverberation   Numerous, persistent reflections of sound energy.

RF   See radio frequency (RF).

RF control   RF control is generally employed as a user interface to the control system. Some manufacturers’ devices provide control links into their components using RF transmission, as this affords the ability to control devices when line of sight is not possible.

RF system   A closed-circuit system with the composite video and audio signals modulated at a certain frequency, called a channel. RF systems require a display device (such as a television) with a tuner set to a selected channel to display the information modulated onto that frequency.

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

RGBS signal   A four-component signal composed of a red signal, a green signal, a blue signal, and a composite sync signal.

RGsB signal   A three-component signal composed of a red signal, a green signal with composite sync added to the green channel, and a blue signal. It is often called sync on green.

rigid metal conduit   Rigid metal conduit, called rigid in North America, is the heaviest conduit and offers the best physical and EMI protection.

rigid nonmetallic tubing   Rigid nonmetallic tubing is very stiff with a thick wall but lightweight. It is similar to plumbing tubing. Because it is not flexible, it is available in preformed pieces at various angles.

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

room criteria (RC) rating   With measurements taken at eight center-octave frequencies from 31.5Hz to 8kHz, the average of the measurements taken from 500, 1kHz, and 2kHz. This includes additional steps to rate the background noise as (N) for neutral, (R) for rumbly, or (H) for hissy.

room mode   An acoustic phenomenon that occurs between the parallel surfaces of an enclosure where the dimension between those parallel surfaces equals one-half wavelength (and the harmonics thereof) of a frequency. The wave is thus reflected on itself out of polarity creating location-specific areas of maximum and minimum pressure.

router   A device that works on the OSI layer above the Network and Transport layers. A router knows the IP address of sent packets, and it can dispatch them to specific locations on the network.

RS-232   The interface between data terminal equipment and data circuit-terminating equipment employing serial binary data interchange. It supports a single-ended mode of operation with one driver and one receiver. At a cable length of 15m (50ft) RS-232 supports a data rate of up to 19.2kbps. At its maximum cable length of 900m (3000ft) it supports a data rate of 2.4kbps.

RS-422   Provides the electrical characteristics of balanced voltage digital interface circuits. It is a balanced signal with one driver and 10 receivers with multidrop capability. The maximum cable length for RS-422 is 1,220m (4,000ft) with a data rate of 10Mbps.

RS-485   Supports a differential mode of operation with 32 drivers and 32 receivers and multidrop capability. The maximum cable length for RS-485 is 1.2km (4,000ft) with a data rate of 10Mbps.

RsGsBs   Red, green, and blue signals with composite sync added to each color channel. This requires three cables to carry the entire signal. It is often referred to as RGB sync on all three.

RT₆₀   The time taken for the energy in an initially steady reverberant sound field to decay by 60dB after the source of the sound ceases.

RU   See rack unit (RU).

sampling rate   The number of samples taken per unit of time (typically seconds) when converting a continuous (analog) signal to a discrete signal (typically a digital signal).

scale   The representation of a number by another number differing by a fixed ratio.

scale drawing   A drawing that shows objects in accurate proportion, with all dimensions enlarged or reduced in a fixed ratio.

scaler   A processor that changes the resolution of an image without changing its shape. Scaling may be required when the image resolution does not match the resolution of the display device.

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

scattering   When a wave hits a textured surface, the incoming waves are reflected in multiple directions because the surface is uneven.

scene   A recallable preset of lighting levels for one or more zones.

scope statement   A written agreement between the client, the project sponsor, the key stakeholders, and the project team that defines the boundaries of the project.

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.

section drawing   A section drawing is a view of the interior of a building in the vertical plane. Section drawings show a bisected wall, which allows you to view what is behind it.

sensitivity specification   A way to determine a device’s ability to convert one form of energy into another form of energy. It is used to define the device’s efficiency in converting from one form to another.

serial digital interface (SDI)   A set of serial data standards to transport digital video data over the BNC-terminated 75Ω coaxial cable. Variants include HD-SDI for HD video, 6G-SDI (6Gbps) for 4kp30, 12G-SDI (12Gbps), for 4kp60 and 24G-SDI (24Gbps) for 8kp30 video. SDI can also be transported over optical fiber.

series circuit   When all the current supplied by the source will flow through the entire circuit. The electrons leaving the source of power go through each component of the circuit and return to the source. While all the current flows through all the circuit, the voltage is divided between the three resistors (loads) as well as the wire that connects them.

series/parallel loudspeaker circuit   When groups of loudspeakers called branches are wired together in series. Typically, loudspeakers in the same branch have the same impedance. Each branch is connected to the positive and negative lines of the amplifier in parallel.

server   A computer system that share resources and services with other connected devices.

service level agreement (SLA)   A document used to record an agreement between a service provider and a customer. It describes the services to be provided, documents service-level targets, and specifies the roles and responsibilities of the service provider(s) and the customer(s).

shear   The tendency of a mount to tear or cut off from the structure.

shield   A metallic partition placed between two regions of space. A shield is used to control the propagation of electric and magnetic fields from one of the regions to the other. It contains electric and magnetic fields at the source or to protect the receiver from electric and magnetic fields. A shield can be the chassis (metallic box) that houses an electronic device or the metallic enclosure (aluminum foil or copper braid) that surrounds a wire or cable.

shotgun microphone   A long, cylindrical, highly sensitive microphone with a very narrow pickup pattern.

sightline   The line of sight between a viewer and an object that needs to be seen.

signal flow   The traceable path of signals through a system.

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

signal ground   1. A 0V (zero volt) point of no potential that serves as the circuit reference. 2. A low-impedance path for the current to return to the source.

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

single-point ground (SPG)   In the context of IEEE Std. 1100, refers to implementation of an isolated equipment grounding configuration for the purposes of minimizing problems caused by circulating current in ground loops.

signal-to-noise (S/N) ratio   The ratio, measured in decibels, between an information signal and the accompanying non-information noise. The higher this ratio, the cleaner the signal.

Simple Network Management Protocol (SNMP)   A set of Internet Engineering Task Force (IETF) standards for network management.

socket   In a TCP/IP network, the combined port number, Transport Layer protocol identifier, and IP addresses of communicating end systems. A socket uniquely identifies a session of a given transport protocol.

sound pressure level (SPL)   In the context of Standard 1M, expressed in unweighted decibels.

sound reinforcement system   The combination of microphones, audio mixers, signal processors, power amplifiers, and loudspeakers that are used to electronically amplify and distribute sound.

source-specific multicast (SSM)   In streaming, allows clients to specify the sources from which they will accept content. This has the dual benefit of reducing demands on the network while also improving network security. Any device that has the host address can try to send traffic to the multicast group, but only content from the specified source will be forwarded to the group.

specification   A written, precise description of the design criteria for a piece of work. Specifications define the level of qualitative and/or quantitative parameters to be met and the criteria for their acceptance. All specifications must be formulated in terms that are specific, measurable, and verifiable and unambiguous.

specular reflection   A mirror-like reflection of energy, in which most of the energy is reflected in a single direction.

speech privacy system   A sound system that adds background noise to an environment to raise the hearing threshold to make it more difficult to hear low-level sounds such as traffic noise, machinery, and distant human speech. Used to assist with speech privacy in open environments.

speech-reinforcement system   An audio system that reinforces or amplifies a presenter’s voice.

splitter   An electronic device that splits a signal to route it to different devices.

spot photometer   A type of meter used to measure illuminance over a narrow angle.

standing wave   Occurs between parallel surfaces of an enclosure (could be a room, a loudspeaker cabinet, and so on) where the dimension between those parallel surfaces equals one-half wavelength (and the harmonics thereof). The wave is thus reflected on itself out of phase creating location-specific areas of maximum and minimum pressure.

star topology   A network topology where all network devices are connected to a central network device, usually a switch.

static IP address   A permanently assigned IP address.

stereophonic   Commonly shortened to stereo, describes when input from all microphones is split into at least two channels before driving the signal through the loudspeakers.

streaming video/streaming 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 need to wait to download a large file before seeing the video or hearing the sound.

subnet   A logical group of hosts within a local area network (LAN). A LAN may consist of a single subnet, or it may be divided into several subnets. Additional subnets may be created by modifying the subnet mask on the network devices and hosts.

subnet mask   A binary number whose bits correspond to IP addresses on a network. Bits equal to 1 in a subnet mask indicate that the corresponding bits in the IP address identify the network. Bits equal to 0 in a subnet mask indicate that the corresponding bits in the IP address identify the host. IP addresses with the same network identifier bits as identified by the subnet mask are on the same subnet.

subwoofer   A loudspeaker that reproduces lower frequencies, typically 20Hz to 200Hz.

supercardioid 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, a microphone designed to be mounted directly against a hard boundary or surface, such as a conference table, a stage floor, or a wall, to pick up sound.

surround-sound system   An audio system that uses multiple channels to produce an acoustic experience where the sound appears to surround listeners.

switcher   A device used to select one of several available signals.

sync   Synchronization. The timing information used to coordinate signals and events.

system   In the AV industry, a compilation of multiple individual AV components and subsystems interconnected to achieve a communication goal.

system black   The lowest level of luminance a system is capable of producing for its task operating conditions.

system grounding   The intentional grounding of one of the current-carrying conductors in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines, and that will stabilize that voltage to earth during normal operation.

tap   A connection to a transformer winding that allows you to select a different power level from the transformer.

task lighting   Lighting directed to a specific surface or area that provides illumination for visual tasks.

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.

threshold   The point at which a function or effect becomes active.

throw distance   The distance between a light source, such as a projector or luminaire, and a focusing surface, such as a stage or a screen.

Thunderbolt   Interface technology that transfers audio, video, power, and data over one cable in two directions. Thunderbolt versions 1 and 2 use the same connector as Mini DisplayPort (MDP), while Thunderbolt 3 uses USB Type-C.

time code   A sequence of numeric codes generated at fixed intervals to provide a time synchronization signal. The Society of Motion Picture and Television Engineers (SMPTE) time code used throughout the AV and production industries uses an eight-digit address scheme, representing the hour, minute, second, and frame number, for each frame of a video sequence. SMPTE time code is encoded in a wide variety formats, including being embedded in audio, video, and data streams.

time domain   A view of a signal as amplitude versus time. The display on a time-based oscilloscope shows the input signal in the time domain.

Time-Sensitive Networking (TSN)   The IEEE working group overseeing the Audio Video Bridging standard has been renamed Time-Sensitive Networking to reflect the standard’s applicability to communication among different types of devices, such as network sensors. See Audio Video Bridging (AVB).

transduction   The process by which one type of energy is changed into another.

transformer   A passive electrical device that electromagnetically transfers energy between two AC circuits. Commonly constructed of at least two electrically isolated induction coils sharing a common core.

transient disturbance   A momentary variation in a signal, such as a surge, spike, sag, dropout, or spurious noise.

transition-minimized differential signaling (TMDS)   A technology for transmitting high-speed serial data. The signaling method used in the HDMI and DVI interfaces.

transmission   The passage of a wave through a medium. Examples include the transmission of soundwaves through air, and the transmission of electromagnetic waves through space.

Transmission Control Protocol (TCP)   A connection-oriented, reliable Transport layer protocol. TCP transport uses two-way communication to provide guaranteed delivery of information to a remote host. It is connection-oriented, meaning it creates and verifies a connection with the remote host before sending it any data. It is reliable because it tracks each packet and ensures that it arrives intact. TCP is the most common transport protocol for sending data across the Internet.

transmission loss   The attenuation that occurs as a signal moves through a medium. Usually expressed in decibels.

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

tweeter   A loudspeaker that is designed to reproduce frequencies above 3kHz.

twisted-pair   A pair of wires that are twisted around each other to facilitate common mode noise rejection.

ultra high definition (UHD or ultra HD)   A term used to describe video formats with a minimum resolution of 3840×2160 pixels in a 16×9 or wider aspect ratio.

UHD ecosystem   The video cameras, recorders, servers, media players, displays, distribution, processing and networking technologies used for recording, editing, producing, delivering and displaying ultra-high-definition video.

unbalanced circuit   A circuit in which one conductor carries the signal and another conductor carries the return. The return conductor is often the cable shield or drain wire and is a low-impedance connection connected to the signal ground. As the impedances of the two conductors are quite different, they are unbalanced with respect to one another.

unicast streaming   A one-to-one connection between the streaming server sending out the AV data and client devices listening to the stream. Each client has a direct relationship with the server. The client sends a request to the server, and the server sends the client a stream in response. Since the server is sending out a separate stream for each client, each additional client takes up more bandwidth. Streaming media to three clients at 100Kbps actually uses 300Kbps of bandwidth. IP Unicast streams may use either UDP or TCP transport, although with TCP transport, there will always be some buffering.

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

Universal Serial Bus (USB)   A standard for connecting, communicating, and supplying power between electronic devices. Version 3.2 of USB is capable of communicating at 20Gbps, and can utilize a USB Type-C (USB-C) connector, which supports DisplayPort, HDMI, power, all USB generations, and VGA. USB 4 communicates at up to 40Gbps and includes handling the Thunderbolt protocol.

unshielded twisted-pair (UTP) cable   Typically used for data transfer, UTP cable contains multiple two-conductor pairs twisted at regular intervals, employing no external shielding.

vectorscope   A specialized oscilloscope-type display used in video systems to display and measure chrominance accuracy and levels. A vectorscope mode may be included in video waveform monitoring systems.

vertical scan rate   The number of complete fields a device draws in a second. This may also be called the frame rate, vertical sync rate, or refresh rate. The vertical scan rate is measured in hertz (Hz) or cycles per second.

video wall   A video display composed of a matrix of smaller video displays linked to display a contiguous image.

viewing angle   The angle at which a viewer is located in reference to the center axis of a display.

viewing area plan   A plan-view drawing of the viewing environment that identifies five viewing locations as defined in the requirements section of the ANSI/INFOCOMM 3M-2011 Standard, Projected Image System Contrast Ratio.

viewing cone   The volume of space containing the audience viewing a display. The term cone is used because there is width, height, and depth to the viewing space, which emanates from the center of the display.

virtual local area network (VLAN)   A type of network created when network devices on separate LAN segments are linked to form a logical group, thereby spanning the logical LANs to which they are connected. For instance, the LANs at each branch of a company could be combined into one company-wide VLAN.

virtual private network (VPN)   A virtual point-to-point private connection established across a public network via an encrypted tunneling protocol. VPNs are used for secure remote monitoring, troubleshooting, and control.

visual acuity   The eye’s ability to discern fine details. There are several different kinds of acuity, including resolution acuity, which is the ability to detect that there are two stimuli, rather than one, in a visual field, and recognition acuity, which is the ability to identify correctly a visual target, such as differentiating between a G and a C.

visual field   The volume of space that can be seen when a person’s head and eyes are absolutely still. It is specified as an angle, usually in degrees. The visual field of a single eye is termed monocular vision, and the combined visual field where the perceived image from both eyes overlap is called binocular vision.

Voice over Internet Protocol (VoIP)   A suite of technologies and protocols that allow the transmission of telephone calls and multimedia over internet protocol (IP) networks.

volt   The basic international unit of potential difference or electromotive force. It is represented by the symbol V.

voltage   The electrical potential difference across a circuit.

watt   The measurement of the amount of power consumed by a system. It is represented by the symbol W.

waveform monitor   An oscilloscope-type monitor used to monitor the waveforms of signals. A video waveform monitor is a specialized monitor used to display and analyze a video signal’s sync, luminance, and chroma levels. Some waveform monitors include a vectorscope mode.

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

wayfinding   The use of audiovisual guides or signage to assist with navigation to a destination.

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, and more.

white noise   A signal with a broad spectrum of random frequencies at the same energy level.

wide area network (WAN)   A data communications network that links local area networks (LANs) that are distributed over large geographic areas, such as cities, states, countries and regions.

wire   A single conductive element intended to carry a current.

wireless access point   A network device that allows other devices to access a wireless network.

wireless local area network (WLAN)   A network that shares information by radio frequency (RF) wireless transmission.

woofer   A loudspeaker that produces low frequencies, typically 20Hz to 200Hz.

work breakdown structure (WBS)   A deliverable-oriented grouping of project elements that will ultimately organize and define the total scope of the project. Each descending level represents an increasingly detailed definition of a project component.

XLR connector   A secure, low-voltage connector used in professional audiovisual systems. The 3-pin version is the standard audio signal cable for the production and AV industries. The 4-pin version is widely used for communication headsets and the 5-pin version is the standard connector for the DMX512 digital lighting protocol. Also known as a Cannon connector.

zone   A defined area within a system. In the context of lighting, a zone is a grouping of luminaires (lighting fixtures) that are focused on the same area. In the context of digital signage, a zone is an area where specific content may be placed. In the context of audio, a zone is an area where the same program is delivered.