Technology can be confusing, which is why no audio visual resource would be complete without a comprehensive glossary of terms. AV-iQ has created a list of AV terms and their definitions to better help you navigate through the world of audio visual technology.
3.5 mm mini
A connector that is similar in appearance to a 1/4-inch phone connector, but much smaller. It measures 3.5 mm in diameter.
See alternating current.
acceptable viewing area
A viewing range for a screen suggested as a 45-degree line extending outward from the left edge and right edge of a displayed image.
The science of sound wave behavior in air.
Adapters are used as interfaces in audiovisual technology to change from type of connector, signal format or power source to another.
Audio Engineering Society.
See authority having jurisdiction.
alternating current (AC)
An electric current that reverses its direction periodically.
All light in a viewing room produced by sources other than the display.
Sound that is extraneous to the intended, desired, and intentional audio; background noise.
An electronic device for increasing the strength of electrical signals.
The strength of an electronic signal as measured by the height of its waveform.
A method of transmitting information by a continuous but varying signal.
angularly reflective screen
A screen that reflects light back to the viewer at a complementary angle.
Annotation allows a presenter to mark up a displayed image as a means of highlighting specific information. Annotation technologies include interactive pens & displays, whiteboards, handheld tablet devices, touch-sensitive screens and more.
American National Standards Institute.
An opening in a lens regulating the amount of light passing through the lens to the imager.
Digital signage appliances are processing devices that support networks or help manage distribution or playback of digital signage across multiple screens or devices.
Archival systems are equipment-based systems designed to ingest, organize & access multi-format rich-media content.
A small disturbance that affects the quality of a signal.
The ratio of image width to image height.
Assistive listening devices provide enhancement of sound for people who are hard of hearing. The Americans with Disabilities Act mandates the use of assistive listening devices in certain environments.
ATA shipping cases are road cases which follow Air Transport Association specifications certified for airline shipping.
To reduce the amplitude (strength) of a signal or current.
Audience responses systems are devices that tabulate results when presenters ask questions & audience members to respond or vote by pushing buttons.
An electronic device used to manipulate audio signals in some manner.
An electrical representation of sound.
Converting acoustical energy into electrical energy or electrical energy back into acoustical energy.
authority having jurisdiction (AHJ)
1. An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure. 2. The entity responsible for interpretation and enforcement of local building and electrical codes (BICSI Information Transport Systems Dictionary).
A two-conductor circuit in which both conductors and all circuits connected to them have the same impedance with respect to ground and all other conductors.
1. Short for balanced to unbalanced.
2. A transformer used to connect a balanced circuit to an unbalanced circuit. For example, a transformer used to connect a 300-ohm antenna cable (balanced) to a 75-ohm antenna cable (unbalanced).
A grouping or range of frequencies.
1. A range of frequencies. 2. In terms of a circuit or equipment, the range of frequencies that the circuit or equipment can reliably pass. 3. In terms of a spectrum, defines the range of frequencies used or allowed.
The result of encoding a higher-quality signal into a lower-quality form, such as RGB converted into S-Video.
A video signal that has not been modulated.
The maximum amount a conductor can be bent before excessive attenuation is encountered, signal integrity is compromised, or the conductor breaks.
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.
Shortened form of binary digit, symbolized by ones and zeros. A bit is the smallest unit of digital information.
The number of bits used to describe data.
An illustration of the signal path through a given system.
Pieces of wood that have been inserted between structural building elements to provide a secure mounting point for finish materials or products.
A professional type of video connector featuring a two-pin lock.
A microphone that relies on reflected sound from a surrounding surface.
The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s)
Broadband describes the usage of a wider band of electromagnetic frequencies or channels than standard bandwidth. Broadband applies to signaling in telecommunications, computer networks, video & Internet access.
An electronic device that provides some isolation between other components.
Also buss, a wiring system that delivers power and data to various devices.
An electrically conductive block or bar of metal, typically copper or aluminum, that serves as a common connection for two or more circuits.
A mixture of higher-order harmonics of the 60 Hz noise (hum) originating from the AC power system and audible in the sound system.
An 8-bit word. The abbreviation for byte is B.
An assembly of more than one conductor (wire).
The ability of a nonconductive material to develop an electrical charge that can distort an electrical signal.
capacitive reactance (XC)
Opposition a capacitor offers to alternating current flow. Capacitive reactance decreases with increasing frequency or, for a given frequency, the capacitive reactance decreases with increasing capacitance. The symbol for capacitive reactance is XC.
captive screw connector
Sometimes called a Phoenix connector, a molded plastic connector. Termination requires a wire to be stripped and slid directly into a slot on the connector. A set screw then pushes a gate down to hold the wire in place.
Card readers are learning aids that allow users to swipe magnetic vocabulary cards in a reader which translates the data into spoken audio.
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.
Modulated frequency that carries video or audio signal.
Category 5 (Cat 5)
The designation for 100-ohm unshielded twisted-pair (UTP) cables and associated connecting hardware whose characteristics are specified for data transmission up to 100 Mb/s (part of the EIA/TIA 568A standard).
Category 5e (Cat 5e)
An enhanced version of the Cat 5 cable standard that adds specifications for far-end crosstalk (part of the EIA/TIA 568A standard).
Category 6 (Cat 6)
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.
Community antenna television system or cable television. Broadcast signals are received by a centrally located antenna and distributed by cable.
See charged-coupled device.
See closed circuit television.
A connection point located halfway along the winding of a transformer or inductor.
charged-coupled device (CCD)
A semiconductor light-sensitive device, commonly used in video and digital cameras, that converts optical images into electronic signals.
Also called a cabinet or frame, an enclosure that houses electronic equipment and is frequently electrically conductive (metal). The metal enclosure acts as a shield and is connected to the equipment grounding conductor of the AC power cable, if so equipped, in order to provide protection against electric shock.
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.
The color portion of a composite or S-Video signal.
an ambiguous term that refers to an electrical ground with insignificant electromagnetic interference (EMI) present.
The deformation of an audio signal when a device's peak amplitude level is exceeded.
Also called timing signals, used to fine-tune the computer image. This function adjusts the clock frequencies that eliminate the vertical banding (lines) in the image.
closed circuit television (CCTV)
A system of transmitting video signals from the point of origin to single or multiple points equipped to receive signals.
See common-mode rejection ratio.
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.
An acronym for coder/decoder. An electronic device that converts analog signals, such as video and audio signals, into digital form and compresses them to conserve bandwidth on a transmission path.
That part of an NTSC video signal that carries the color information. It is a signal consisting of several (eight to ten in NTSC) cycles of unmodulated color subcarriers, superimposed at a specified location within the composite signal.
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.
A transversal filter that combs out a specific set of frequencies. Comb filters are very effective in separating the chrominance and luminance sidebands in an NTSC video signal.
In a process called multiplexing, puts signals together onto one cable, constituting a broadband signal.
Refers to either noise or surge voltage disturbances occurring between the power neutral (white wire) and the grounding conductor (green wire). Unwanted common-mode disturbances exist as a result of noise injection into the neutral or grounding wires, wiring faults, or overloaded power circuits.
common-mode rejection ratio (CMRR)
The ratio of the common-mode interference voltage at the input of a circuit to the corresponding interference voltage at the output.
A device that combines compression and expansion.
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.
The action of the air molecules moving closer together, permitting audible sound.
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.
Also called a capacitor microphone, a microphone that transduces sound into electricity using electrostatic principles.
In electronics, a material that easily conducts an electric current because some electrons in the material are free to move.
The most commonly used component in a loudspeaker system and found in all ranges of drivers.
The technology by which people separated by distance come together to share information. Conferencing systems may include projection systems, monitor displays, computers, satellite connections, video, audio playback devices, and many more items.
Consoles or workstations are used to organize & optimize audiovisual equipment in a central location for a specific purpose such as audio or video editing or production.
The quality of being continuous (as in a continuous electrical circuit).
The portion along a length of a recorded tape on which synchronization control information is placed. A control track is used to control the recording and playback of the signal.
Converters are used to convert signals from one format to another such as from analog to digital or from low resolution to high resolution or vice versa. 3D converters convert images or video from two dimensional to three dimensional viewing.
Central processing unit. The portion of a computer system that reads and executes commands.
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.
Cathode ray tube. The video display tube used in monitors and receivers, radar displays, and video computer displays. The CRT is a high-vacuum tube containing an electron gun to produce the images seen on the face of the tube.
Cue systems help the speaker communicate with the projectionist and vice versa during a presentation, but with today's presentation systems, the presenter can often control the projector & slides remotely.
The amount of electrical energy that is flowing in a circuit.
curvature of field
A blurry appearance around the edge of an otherwise in-focus object (or the reverse) when the velocity of light going through the lens is different at the edges than at the center of the surface. Curvature of field is due to the lens design.
See distribution amplifier.
A measure of sound pressure level represented in dynes per centimeter squared. Its reference, 0 dB SPL equals 0.0002 dynes/cm2. dB SPL is used as a measure of acoustical sound pressure levels, and is a 20log function.
A comparison of two measurements or values. It is one-tenth of a Bel (a unit of measurement named for Alexander Graham Bell).
an ambiguous term that refers to an insulated equipment grounding conductor.
an ambiguous term that refers to one of more individual branch circuits with a supplemental grounding conductor.
A uniform winding of wire used to electromagnetically direct an electron beam to draw an image on a CRT.
An audio signal-processing device or circuit used to retard the speed of transmission on one or more audio signals or frequencies.
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.
Refers to either noise or surgÃŸe voltage disturbances occurring between the power hot and the neutral conductor. Most differential-mode disturbances result from load switching within a building, with motor type loads being the biggest contributor.
The scattering or random redistribution of a sound wave from a surface. Diffusion occurs when surfaces are at least as long as the sound wavelengths, but not more than four times as long.
A method of transmitting information by discrete, noncontinuous impulses.
Digital asset management systems are comprised of hardware systems & software that support capture, storage, retrieval & distribution of media assets. Digital assets include everything from digital text & images to audio, video & animations.
An electronic device that converts digital signals into analog form.
Digital media players are devices that allow users to playback or stream audio & video content from digital media servers, the Internet or computer hard drives.
JVC's Digital-direct Drive Image Light Amplifier projection system.
For Deutsche Industrie-Norm, a connector that follows the German standard for electronic connections.
direct current (DC)
Electricity that maintains a steady flow and does not reverse direction, unlike alternating current (AC). Usually provided by batteries, AC-to-DC transformers, and power supplies.
Also known as near-field, sound that is not colored by room reflections.
an ambiguous term that refers to a ground with electromagnetic interference present.
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.
A sound system using multiple loudspeakers separated by distance. It typically operates in a lower sound pressure level than a high-pressure system. The loudspeakers are most often suspended over the heads of the listeners.
An active device used to split one input into multiple outputs, while keeping each output isolated and the signal level constant.
Digital Light Processing by Texas Instruments. A projection system that has technology based on the digital micromirror device (DMD). It uses thousands of microscopic mirrors on a chip focused through an optical system to display images on the screen.
An imaging device used to create a video image of printed documents or three-dimensional objects.
A type of loudspeaker driver construction. Fabric or woven materials are used to create a dome-shaped diaphragm, and the coil is attached to the edge of the diaphragm.
In audio, an individual loudspeaker unit.
A generic name for a D-shaped serial connector used in data communications.
Digital Television. A signal transmitted digitally.
Digital video disc or digital versatile disc. An optical storage medium for data or video.
Digital Visual Interface. A connection method from a source (typically a computer) and a display device that can allow for direct digital transfer of data. The digital signal is limited to 5 meters.
One of two common multipin connectors available for DVI signals. The DVI-D carries only digital information; no analog video information is sent. The digital signal is limited to 5 meters.
One of two common multipin connectors available for DVI signals. The DVI-I adds analog video to the connection, permitting greater distances than the digital limit of 5 meters.
A pressure-sensitive microphone of moving-coil design that transduces sound into electricity using electromagnetic principles.
early reflected sound
Sound created by 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.
Earsets allows the user to listen to an audio signal in a single ear as opposed to both ears in a headset.
See equipment grounding conductor.
A means of eliminating echo from an audio path.
Electronics Industries Alliance. The association that determines recommended audio and video standards in the United States.
electromagnetic interference (EMI)
Improper operation of a circuit (noise) due to the effects of interference from electric and/or magnetic fields.
See electromagnetic interference.
Any display device that emits light to create an image.
A signal that has been compressed into another form to reduce size or complexity, as in a composite video signal.
ENG is an acronym for Electronic News Gathering typically for broadcasting. ENG cameras are used for shoots with lone reporters in the field, TV crews, production trucks and remote newscasts.
Electronic equipment that adjusts or corrects the frequency characteristics of a signal.
The connection to ground (earth), or to a conductive body that extends that ground connection, of all normally noncurrent-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment. The purpose is to limit any voltage potential between the equipment and earth.
equipment grounding conductor (ECG)
The conductive path installed to connect normally noncurrent-carrying metal parts of equipment together and to the system's grounded conductor, to the grounding electrode conductor, or to both..
A centralized housing unit that protects and organizes electronic equipment.
A set of network cabling and network access protocol standards for bus topology computer networks invented by Xerox but now controlled by the 802.3 subcommittee of the Institute of Electrical and Electronics Engineers (IEEE).
An audio processor that comes in two types: a downward expander and as a part of a compander.
A threaded connector that is used in transmission applications such as cable television. The cable's center conductor also serves as the connector's center pin.
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.
A technology that uses glass or plastic threads or wires to transmit information.
In video, one half of a video frame containing every other line of information. Each standard video frame contains two interlaced fields.
Remove or pass certain frequencies from a signal.
A type of display that has a fixed grid on which it re-creates an image.
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 (FL)
The distance, in millimeters, between the center of a lens and the point where the image comes into focus. The value given to a lens, stated in inches or millimeters. The shorter the focal length, the wider the angle of the image.
The act of adjusting a lens to make the image appear clear, sharp, and well-defined.
An English unit of measure expressing the intensity of light illuminating an object. A footcandle equals the illumination from one candle falling on a surface of 1 square foot at a distance of 1 foot.
1. Indicates where possible mounting points are to join two pieces together, the total contact area, and how they may fit together. 2. Space required to house an equipment rack or device. 3. Coverage area of a communications satellite.
1. An individual segment of film. 2. A complete video picture or image of odd and even fields. Two fields equal one frame.
The number of complete cycles in a specified period of time. Formerly expressed as cycles per second (cps), now specified as hertz (Hz).
The range of frequencies within which a microphone is sensitive.
A flat glass or acrylic lens in which the curvature of a normal lens surface has been collapsed in such a way that concentric circles are impressed on the lens surface. A Fresnel lens is often used for the condenser lens in overhead projectors, in rear-screen projection systems, and in studio spotlights.
A system that employs a light-reflecting screen for use when the image will be projected from a source in front of the screen.
Also called f-number, the ratio of focal length to the effective diameter of a lens. It represents how much light is able to pass through the lens.
Known as pure tone, the lowest frequency in a harmonic series.
1. Electronic signal amplification. 2. The ability of a projection screen to concentrate light.
An audio processor that allows signals to pass only above a certain setting or threshold.
A thickness or diameter of a wire.
To lock the synchronization signals of multiple devices to a single source.
See ground-fault circuit interrupter.
A screen covered with tiny glass beads, each of which provides a spherically reflective surface.
good viewing area
The good area from which to view a screen. Typically defined as any point within 45 degrees to the left or right from on-axis. The total good viewing area is 90 degrees.
Commonly referred to as a video card, outputs computer signals.
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.
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.
1. Interruption of a cable shield connection by means of a switch or by simple omission in an attempt to solve a hum or buzz problem from current flowing on a cable shield due to a pin 1 problem, detrimental ground loop, and so on. 2. Interruption of the connection between the chassis ground and signal ground, usually by means of a switch. 3. Incorrect term used for a 3-pin-to-2-pin AC adapter. (See also grounding adapter.)
An electrically conductive loop that has two or more ground reference connections. The loop can be detrimental when the reference connections are at different potentials, which causes current flow within the loop (IEEE).
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.
A point of no potential in a circuit.
The 0V (zero volt) reference point for a circuit.
A system or circuit conductor that is intentionally grounded.
ground-fault circuit interrupter (GFCI)
A safety device that deenergizes a circuit (or a portion of that circuit) within an established period of time when a current to ground exceeds the values established for a Class A device. Class A GFCIs trip when the current to ground is 6 mA or higher; they do not trip when the current to ground is less than 4 mA.
ground-fault current path
An electrically conductive path from the point of a ground fault on a wiring system through normally noncurrent-carrying conductors, equipment, or earth to the electrical supply source.
Connecting to ground or to a conductive body that extends the ground connection. The connected connection is referred to as grounded. (See also equipment grounding and system grounding.)
A 3-pin-to-2-pin electrical adapter, the design of which is defined by National Electrical Code 406.9. The rigid tab or lug is to be used for equipment grounding and not left "floating."
A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes. (See also equipment grounding conductor.)
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.
Higher-frequency sound waves that blend with the fundamental frequency.
HD refers to "high definition" which describes the increased quality of video or audio available in specific technologies & formats compared to traditional "standard definition."
HDMI is a digital connection which enables uncompressed high-definition audio and video to be sent over one cable. Digital AV sources (such as BluRay players) use HDMI cables to transmit signals to HDTVs, HD projectors, monitors, Tablet PCs & digital audio devices.
The equipment located at the start of a cable distribution system where the signals are processed and combined prior to distribution.
The difference in dB SPL between peak and average level performance of an audio system. For a speech-only system, this value is 10 dB.
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.
Cycles per second of an electrical signal.
Broadband higher-frequency noise typically associated with poor audio system gain structure.
The action of turning off the trace on an analog CRT during horizontal retrace
A loudspeaker that reproduces mid to high frequencies.
The part of a displayed image that is unevenly illuminated, usually a bright area in the center.
Undesirable 60 Hz noise emanating from a sound system or evidenced by a rolling hum bar on a display.
The Institute of Electrical and Electronics Engineers.
The total opposition to current flow in an AC circuit. Like a DC circuit, it contains resistance, but it also includes forces that oppose changes in the current (inductive reactance) and voltage (capacitive reactance). Impedance takes into account all three of these factors. It is measured in ohms, and its symbol is Z.
Opposition to the starting, stopping, or changing of current flow in a coil of wire. An inductor's ability to resist the changes in current is represented by the symbol L, but it is measured in henries (H).
The influence exerted on a conductor by a the movement of a magnetic field. An example of this is a magnet moving through a coil of wire.
inductive reactance (XL)
Opposition to the current flow offered by the inductance of a circuit. It is dependent on frequency and inductance. Its symbol is XL.
A frequency range of light used to send information. Remote controls and other wireless devices use IR.
Also known as the dielectric, material applied to a conductor that is used to isolate the flow of electric current between conductors and to provide protection to the conductor.
Interactive Whiteboards are an essential tool in business and classroom communications. They are used to display text, data and graphics from a computer or projector onto a large surface or display. Presenters and users can then interact with the image using a pen, stylus, finger or other device.
The scanning process that combines odd and even fields of video to produce a full frame of video signal.
Internet Protocol (IP)
A standard networking protocol, or method, that enables data to be sent from one computer or device to another over the Internet.
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. For AV systems, this law is applied to light and sound.
See Internet Protocol.
An Institute of Radio Engineers (IRE) unit used as a reference to measure video signal levels.
Integrated Services Digital Network (ISDN) is a communications standard for transmitting voice, video and data over digital phone lines or the traditional telephone network. Common applications of ISDN include telecommuting, Internet access, video conferencing & data networking.
isolated ground (IG)
A commonly misused term to describe a requirement for a dedicated equipment ground that terminates only at the main panelboard at the service entrance. An equipment grounding method permitted by the National Electrical Code (NEC) for the reduction of electrical noise (electromagnetic interference) on the grounding circuit. Equipment grounding for isolated receptacles and circuits is accomplished via insulated equipment grounding conductors and run with the circuit conductors.
isolated grounding circuit
A circuit that allows an equipment enclosure to be isolated from the raceway containing circuits, supplying only that equipment by one or more listed nonmetallic raceway fittings. The equipment is grounded via an insulated grounding conductor. (See National Electric Code 250.96 (B) for additional information.)
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. (See NEC 2008 250.146 (D) for additional information.)
isolated star ground
InfoComm experts consider this term ambiguous. See isolated ground.
Outside covering used to protect cable wires and their shielding.
1. A portable set terminal for power cables. 2. Generally, metal or plastic boxes where wire and/or cable terminates, combines, or splits. It is used to protect the conductors.
The trapezoidal distortion of a square-cornered image due to the optical effect of the projection device being located in an improper position with respect to the screen.
Local area network. A computer network limited to the immediate area, usually the same building or floor of a building.
A small microphone designed to be worn either around the neck or clipped to apparel.
Liquid crystal display.
Liquid crystal on silicon.
Learning labs are typically classroom environments where students can receive specialized instruction or skills training. These labs rely on pro-AV equipment such as portable presentation systems, audio & video players, whiteboards, computer workstations, jackboxes, headphones and more.
least favored viewer (LFV)
The farthest usable seat from the image. The LFV depends on the viewing angle toward the screen, image size, and content being displayed.
A screen surface characterized by silvered or aluminized embossing, designed to reflect maximum light over wide horizontal and narrow vertical angles. The device must be held very flat to avoid hot spots.
Lifts are designed to raise or lower equipment for easy access and storage as needed.
Lift Mounts are mounted to a wall, the ceiling or a cabinet. They are commonly used with large flat-panel displays & projectors where aesthetics, utility and room space are a concern.
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.
Equipment, materials, or services included in a list published by a Nationally Recognized Testing Laboratory (NRTL), such as Underwriters Laboratories (UL), that is acceptable to the authority having jurisdiction (AHJ). The NRTL list is concerned with the evaluation of products and services. The NRTL maintains periodic inspections of the production of the listed equipment or materials and periodic evaluations of the listed services. The listing states that the equipment, material, or services meets appropriate designated standards or has been tested and found suitable for a specified purpose.
An electrical industry term used to identify a lighting and appliance panelboard designed for use in residential and light-commercial applications.
A device used to monitor the output of a signal from a system or other device in the local vicinity.
The exponent of base 10 that equals the value of a number.
A transducer that converts electrical energy into acoustical energy. A loudspeaker is basically a driver within an enclosure.
An ambiguous term. It may mean less than 70V AC to an AV contractor, while an electrician may use the same term to describe circuits less than 600V AC. The term may also be determined by the authority having jurisdiction (AHJ).
A measure of the light quantity emitted from a constant light source across 1 square meter.
Also called luma, part of a bandwidth-limited video signal combining synchronization information and brightness information. Its symbol is Y.
A contraction of the words luminance and flux. 10.7 lux is equal to 1 footcandle.
A decoder that produces red, green, and blue from Y, R-Y, and B-Y.
An electronic device with multiple inputs and outputs. The matrix allows any input to be connected to any one, several, or all of the outputs..
A screen that evenly disperses light 180 degrees uniformly, both horizontally and vertically, creating a wide viewing cone and wide viewing angle.
Master antenna television system. A television system where broadcast programs are received via a master antenna array and then distributed to users over coaxial or fiber-optic cable.
Media players are used in digital signage to play and/or schedule content such as media files across a network of displays.
media retrieval system
A system that allows for remote requests of content to be delivered from a headend location in a facility.
MIDI controllers allow users to control electronic devices that send and transmit data using MIDI protocol. Controllers such as keyboards, samplers or synthesizers can then work in synchronization with other MIDI-compatible devices such as musical instruments, VCRs, multi-track recorders, computers, light show controllers and more.
A loudspeaker that reproduces midrange frequencies, typically 300 Hz to 8,000 Hz.
A device for blending multiple audio sources.
A connector used with four, six, or eight pins. Common modular connectors are RJ-11 and RJ-45 (8P8C).
A device that converts composite or S-Video signals, along with corresponding audio signals, into modulated signals on a carrier channel.
Uses input from all microphones and relays them from the electronic control system to the loudspeakers using a single path or channel.
A Moving Pictures Expert Group (MPEG) compression scheme that reduces the number of bits needed to code the video image.
A multipurpose test instrument with a number of different ranges for measuring current, voltage, and resistance.
The process used by the combiner to put together a number of modulated signals.
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.
The number rows of horizontal and vertical pixels that create the picture. The native resolution describes the actual resolution of the imaging device and not the resolution of the delivery signal.
Sound that has not been colored by room reflections. This is also known as direct sound.
See grounded conductor.
The metric unit for screen or surface brightness.
Any electrical signal present in a circuit other than the desired signal.
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).
A filter that notches out, or eliminates, a specific band of frequencies.
National Television System Committee standard for analog video transmission in North America.
A band, or group, of frequencies. The relationship of the frequencies is such that the lowest frequency is half the highest. 200 Hz to 400 Hz is an octave, 4,000 Hz to 8,000 Hz is an octave, and so on.
OEM is an acronym for "Original Equipment Manufacturers." OEM manufacturers sell equipment to other manufacturers for the purpose of integrating components and rebranding products for their market.
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).
Describes the shape of the area for microphones that have equal sensitivity to sound from nearly all directions.
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.
Opaque projectors are projectors that project images from opaque materials onto a screen.
operating system (OS)
Computer platform that enables software applications to communicate with the CPU.
A test device that allows measurement of electronic signals by displaying the waveform on a CRT.
Any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, a short circuit, or a ground fault.
overcurrent protection device
A safety device designed to open a circuit if the current reaches a value that causes excessive or dangerous temperatures in conductors or conductor insulation. Examples are circuit breakers and fuses.
A device that produces an image on a screen by transmitting light through transparent acetate placed on the stage of the projector.
The Phase Alternate Line (PAL) video standard, followed by much of Europe and Australia.
A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices. A panelboard may be equipped with switches for the control of light, heat, or power circuits. It is designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support, and accessible only from the front.
See plasma display panel.
See power distribution unit.
The highest level of signal strength, determined by the height of the signal's waveform.
An adjustment method that allows compensation for high-frequency loss in cables.
A DC power source available in various voltages.
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.
A molded, plastic, captive screw connector. Termination requires a wire to be stripped and slid directly into a hole on the connector (compression termination).
An audio connector used as a loudspeaker connector. Common types are 1/4 inch and 1/8 inch.
The European name for an RCA connector.
The substance that glows when struck by an electron beam, providing the image in a CRT. The higher the quality of the phosphor, the brighter and more vivid the image.
A sound that has equal energy (constant power) in each 1/3-octave band.
A combination of two words, "picture" and "element".. The smallest element used to build a digital image.
plasma display panel (PDP)
A direct-view display made up of an array of cells, known as pixels, which are composed of three subpixels, corresponding to the colors red, green, and blue. Gas in the plasma state is used to react with phosphors in each subpixel to produce colored light (red, green, or blue) from a phosphor in each subpixel.
Plenum boxes are designed to house equipment that requires air flow or ventilation to keep cool. Plenum boxes are typically used with ceiling-mounted projectors, so that cabling & equipment are not run through a plenum (air-flow space) to avoid fire hazards.
A sound system that has a central location for the loudspeaker(s), 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.
Conferencing where two sites are directly linked.
Also known as pickup pattern, the shape of the area that a microphone will be most sensitive to sound.
A rack-mountable or portable electrical enclosure that is connected by a cord or cable to a branch circuit for distribution of power to multiple electronic devices. A PDU may contain switches, overcurrent protection, control connections, and receptacles.
Power conditioners enhance the quality of power going to equipment by regulating voltage, eliminating noise or correcting other issues.
Power sequencing is the act of powering on & 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.
A preamplifier or preamp is an electronic device that boosts a signal and sends it to a main amplifier for further processing.
The lens that focuses the image onto the screen.
A beam splitter that filters the light into its red, green, and blue components.
Scanning that traces the image's scan lines sequentially, such as with an analog computer monitor.
The maximum amount of tension that can be applied to a cable or conductor before it is damaged.
See fundamental frequency.
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 (IEEE Std. 142-1991).
An enclosed channel of metal or nonmetallic materials designed for holding wires, cables, or busbars, with additional functions. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquid-tight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways, and busways.
rack unit (RU)
A unit of measure of the vertical space in a rack. One RU equals 1.75 inches (44.5 mm).
radio frequency (RF)
The portion of the electromagnetic spectrum that is suitable for radio communications. Generally, this is considered to be from 10 kHz up to 300 MHz. This range extends to 300 GHz if the microwave portion of the spectrum is included.
radio frequency interference (RFI)
Radiated electromagnetic energy that interferes with or disturbs an electrical circuit.
Random access memory. The most common type of computer memory used by programs to perform tasks while the computer is on. An integrated circuit memory chip allows information to be stored or accessed in any order, and all storage locations are equally accessible.
The action of molecules moving apart.
The scanned or illuminated area of a CRT.
The comparison of two quantities.
Also known as a phono connector, a connector most often used with line-level audio signals.
Opposition to alternating current resulting from capacitance and inductance in the circuit.
A system in which the image is projected toward the audience through a translucent screen material, for viewing from the opposite side. This is opposed to front-screen projection.
A receiver is an audio-video device that amplifies sound, routes video signals, often includes an AM-FM tuner and serves as a selector for different types of equipment.
The point of no potential used as the 0V (zero volt) reference for a circuit.
Light or sound energy that has been redirected by a surface.
Any display device that reflects light to create an image.
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.
relocatable power tap
A cord-connected product rated 250V AC or less and 20 A or less with multiple receptables. 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.
The property of a material to impede the flow of electrical current, expressed in ohms.
1. The amount of detail in an image. 2. The number of picture elements (pixels) in a display.
The time it takes for the electron beam to turn off, travel to its next starting point, and then turn back on to begin scanning again.
A self-contained rear-projection system.
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.
See radio frequency interference.
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.
A high-bandwidth video signal with separate conductors for the red signal, green signal, blue signal, horizontal sync, and vertical sync.
A four-component signal composed of a red signal, a green signal, a blue signal, and a composite sync 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."
A network topology that connects terminals, computers, or nodes in a continuous loop.
Read-only memory. Memory whose contents can be accessed and read but cannot be changed. ROM is permanent memory that can be entered only once, normally by a manufacturer. ROM may not be altered or removed.
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."
See equipment grounding conductor.
How many samples of the analog signal are taken in a given time interval when creating the digital signal.
Entertainment or business video and audio transmitted via a satellite.
A feature in a display device that changes the size of an image without changing its shape. Scaling may be required when the image size does not fit the display device.
The process of changing the horizontal scan rate of one device to that of another. Usually used to describe changing the scan rate of a computer to match the television video format (NTSC, PAL, or SECAM) for the purpose of recording or viewing on television video equipment.
The frequency of occurrence of a display drawing one line of information.
When light hits a textured surface, the incoming light waves get reflected in multiple angles because the surface is uneven.
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.
The Séquentiel Couleur Avec Mémoire (Sequential Color with Memory) video standard in France.
separately derived system
A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems do not have any direct electrical connections, such as a solidly connected grounded circuit conductor, to supply conductors originating in another system. Examples of separately derived systems are generators, batteries, converter windings, transformers, and solar photovoltaic systems .
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 contain 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.
The electrical connection between any two conductors of the electrical system from line-to-line or from line-to-neutral (Basic Electrical Theory, by Mike Holt). (A short circuit is not the same as a ground fault.)
A long, cylindrical, highly sensitive, unidirectional microphone used to pick up sound from a great distance.
A test equipment instrument that produces calibrated electronic signals intended for the testing or alignment of electronic circuits or systems.
1. 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.
signal-to-noise (S/N) ratio
The ratio, measured in decibels, between the audio or video signal, and the noise accompanying the signal. The higher this ratio, the better the quality of the sound or picture.
Alternating current electrical power supplied by two current carrying conductors. This type of power is used for residential and some 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.
Satellite and master antenna television system. A television system where satellite and broadcast programs are received via a master antenna array and distributed to users over coaxial or fiber-optic cable.
Sound masking systems add artificial or natural sound to an environment such as an office to mask unwanted sound & foster speech privacy among coworkers in a workspace.
Soundfield systems are sound amplification systems typically used in classrooms to improve the sound distribution or "field of sound" of a teacher's voice.
Society of Motion Picture and Television Engineers.
A specialized connector used to hook up loudspeakers without causing a short circuit. It allows connection of a loudspeaker while it's working, or "hot."
speech privacy systems
Speech privacy system is a sound system that adds background noise to an environment to cover up human speech & prevent privacy issues.
See single-point ground.
Light passing through the edges of the lenses that have focal lengths different from those passing through the center.
An electronic device that divides a signal into different pieces to route to different devices.
A network topology where all network devices are connected to a central network device, usually a hub or a switch.
1. A conductor connection by which separate electrical circuits or equipment are connected to earth at one point (IEEE Std. 1100-2005). 2. A grounding configuration where grounds from different circuits are insulated from one another and referenced (connected) to a single point.
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 media is the traditionally the transfer of audio & video files which are played at the same time they are temporarily downloaded to a user's computer.
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.
A loudspeaker that reproduces lower frequencies, typically 20 Hz to 200 Hz.
supercardioid polar pattern
The exaggerated heart shape of the area that a highly directional microphone is most sensitive to sound.
Also called a boundary microphone, a microphone placed on a table to pick up sound. This type of microphone is often used in boardrooms and other environments where a number of talkers must be picked up and the microphone needs to remain unobtrusive.
A stereo playback system that uses from two to five channels for realistic sound production, producing an experience where the sound appears to surround listeners. This is best achieved using surround-encoded material, a receiver, and surround loudspeakers.
A video signal, also known as Y/C. Y is the luminance, and C is the chrominance. Y and C are transmitted on separate conductors.
A peripheral or sometimes integrated device used to select one of a group of signals.
Synchronization. The timing information that keeps images displaying properly.
Synchronizers provide sophisticated timing control of workstations for audio-video production & post-production facilities & recording studios. Controllers & synchronizers automate the start, stop & cueing of video tape recorders, hard disk recorders, consoles, editing systems, mixers & other devices.
Synthesizers or synths are electronic instruments that mix & modify frequencies or waveforms to create a wide variety of sounds.
In the AV industry, a compilation of multiple individual AV components and subsystems interconnected to achieve a communication goal.
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.
A connection to a transformer winding that allows you to select a different power level from the transformer.
See time-base corrector.
an ambiguous term that refers to a branch circuit with an isolated equipment ground that serves an AV system exclusively..
InfoComm experts consider this term ambiguous. It is used to refer to a separately derived power system that is 120 volts line to line and 60 volts to ground. In the AV industry, technical power refers to power that serves an AV system exclusively.
The maximum force that a material can withstand before deforming or stretching.
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.
The length of the projection beam necessary for a particular projector to produce an image of a specified size.
time-base corrector (TBC)
The circuitry, or a stand-alone component, used to stabilize the horizontal lines of an analog video image (typically originating from tape).
A method of numbering video frames according to Society of Motion Picture and Television Engineers (SMPTE) standards. The code is the eight-digit address representing the hour, minute, second, and frame recorded on the videotape's control track.
A passive electromagnetic device commonly consisting of at least two coils of wire (inductors) with no physical connection between them. Most often, these coils share an iron-based alloy core. This common core aids in concentrating the magnetic lines of force created by the current flow in one coil (primary), thereby inducing a voltage into the other coil (secondary).
A momentary variation in power, such as a surge, spike, sag, blackout, or noise.
Any display device that creates images by allowing or preventing light to pass.
Tip, ring, sleeve. A three-conductor design of a phone connector that can be terminated as balanced or unbalanced.
Tip, sleeve. A two-conductor design of a phone connector used for an unbalanced circuit.
a loudspeaker that is designed to reproduce frequencies above 3000 Hz.
Any number of wires that are paired together and twisted around each other. The wires can be shielded or unshielded.
A two-conductor circuit in which one conductor carries the signal and the other conductor carries the return. The return conductor is usually the cable shield and is a low-impedance connection, as it is connected to the signal ground and possibly also to the earth ground. The impedance of the signal circuitry is quite different from the return circuitry, hence the impedance of the two conductors are quite different - the impedances are unbalanced with respect to one another.
Derived from the number 1, refers to no change in gain.
Unshielded twisted-pair cable, typically used for data transfer. UTP cable contains multiple two-conductor pairs twisted at regular intervals, employing no external shielding.
A specialized oscilloscope used in video systems to measure chrominance accuracy and levels.
The action of turning off the trace on an analog CRT during vertical retrace.
A video wall features several monitors, video screens, display cubes, video projectors or TV sets that are set up on top of each other or side by side to form a single, large contiguous display.
Determines how far off-axis (screen centerline) a viewer can sit and still see a good-quality image. This is no greater than 45 degrees off the projection axis.
The best viewing area for the audience. The term cone is used because there is width, height, and depth to the best viewing area, and this area emanates from the center of the screen.
VOIP Systems or Voice over Internet Protocol are protocols & technology that allow the digital transmission of phone calls & multimedia over the Internet & other networks. VOIP is relayed over smartphones and other internet devices & requires equipment such as VOIP routers, phone adapters, telephone sets & more.
The basic international unit of potential difference or electromotive force.
The electrical potential to create current flow in a circuit.
Wide area network. A data communications system that uses telecommunication circuits to link local area networks (LANs) that are distributed over large geographic distances.
A specialized oscilloscope used to display and analyze the video signals synchronization, luminance, and chroma levels.
The distance between two corresponding points of two consecutive cycles measured in meters.
Webcasting allows the broadcast of digital media such as audio or video over the Internet which audience members can stream live or access on demand. Essential equipment for webcasting includes computers, streaming servers, production software, recording gear, appliances & more.
A sound that has the same energy level at all frequencies.
A single conductive element intended to carry a voltage or electronic signals.
Wireless local area network. A network that shares information by radio frequency (RF).
A loudspeaker that has low frequencies, typically 20 Hz to 200 Hz.
A popular type of audio connector featuring three leads: two for the signal and one for overall system grounding. This is a secure connector often found on high-quality audio and video equipment. It is sometimes called a cannon connector.
A video signal, also known as S-Video. Y is the luminance, and C is the chrominance. Y and C are transmitted on separate synchronized conductors.
InfoComm experts consider that this term ambiguous. See reference point.
A lens that allows the operator to adjust the focal length for sizing or distance.