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A/D - Analog to Digital (converter). A device that converts an analog signal to a digital value.
A/V - Audio visual, or audio video.
AACS – Advanced Access Content System - A digital rights management standard utilized with Blu-ray Disc and other optical formats. AACS incorporates two parts: a set of embedded decryption keys within the source device, and a set of keys encoded in the content that describes each of the playback devices licensed to utilize the content. This approach allows copyright holders to revoke the keys of a particular source device, thus preventing it from playing back future content. AACS also provides for a managed copy system, that is, a mechanism by which one or several, but not an unlimited number of copies can be legally made as backups, for storage on a media server, or for use on a portable device. The ICT – Image Constraint Token is a provision within AACS that allows the content provider to limit analog output resolutions.
AAP - Architectural Adapter Plate. Mountable metal plates available in hundreds of models offering popular pass-through audio, video, phone, data, power, and control connectors. Active AAPs are also available for power, control, and long distance signal transmission. Along with mounting options for maximum flexibility in placing connectors and controls within reach, these interchangeable components fit together to create an attractive and completely customizable A/V connectivity solution.
Absorption - The attenuation of light as it passes through fiber, similar to the resistive loss of an electrical signal as it passes through cable. Absorption is caused by impurities and defects in the fiber.
AC - Alternating Current. Electron flow that changes direction alternately.
AC coupled - A circuit design that does not pass the DC component of a signal, therefore it ignores DC offsets.
AC-3 - See "Dolby® Digital."
Acceptance Angle - In fiber optics, this is the maximum allowable angle of incidence for light entering a fiber measured from the center axis of the fiber. Incoming light must be directed below this angle in order to enter the core of the fiber and propagate along its length through total internal reflection.
Active crossover - A circuit that separates the audio signal into the appropriate frequency bands for the woofer, midrange, and tweeter. An active crossover is placed in the signal path ahead of the amplifier, where a passive crossover is placed between the amplifier and the speaker.
ADC - Analog to Digital Converter. A device that converts analog signals to digital signals.
Additive color process - Also called “RGB.” A color generation process used in video that combines red, green, and blue to make all colors. All three colors (red, green, and blue) at 100% combine to make white on a video screen; the absence of all three colors (0%) makes black. Also see "Subtractive color process."
ADSL - Asymmetrical Digital Subscriber Line. One of a number of DSL technologies, and the most common one. ADSL is designed to deliver more bandwidth downstream (from the central office to the customer site) than upstream.
ADSP™ - Advanced Digital Sync Processing™. Using sync processing to allow centering control (H-shift or V-shift) can create problems with some display devices because of the sync delay. This means the digital projector user may have to choose between a stable sync and centering control. Extron's ADSP restores the original sync timing relationship for a stable sync signal while allowing centering control.
ADTV - Advanced Definition Television. An early HDTV system proposed by the Advanced Television Research Consortium in 1992. Now superseded by US HDTV standards.
Aerial Cables - Optical fiber cables designed for outdoor installations on aerial supporting structures such as poles. They are specifically designed to withstand adverse conditions such as wind and ice loading, pollution, UV radiation, thermal cycling, stress, and aging.
AES – Advanced Encryption Standard - A data encryption standard adopted by the US Government and approved by the National Security Agency for top secret information. DCP, LLP, the licensing agency for HDCP, has adopted AES 128 encryption for the new HDCP 2.0 standard.
AES/EBU - Audio Engineering Society/European Broadcasting Union. A digital audio transfer standard. The AES and EBU developed the specifications for the standard. The AES/EBU digital interface is usually implemented using 3-pin XLR connectors, the same type of connector used in a professional microphone. One cable carries both left- and right-channel audio data to the receiving device. Also see "AES3."
AES3 - A digital audio standard defined by the Audio Engineering Society. The standard specifies several basic physical interconnections between devices: - Balanced - 3-conductor, 110 ohm cabling with an XLR connector, typically referred to as “AES/EBU audio.” - Unbalanced - 2-conductor, 75 ohm coaxial cable with an RCA connector, typically used in consumer audio applications. In many consumer products such as DVD players and A/V receivers, this is often referred to as a “digital coaxial” connection type. - AES-3id - A professional version of the 2-conductor 75 ohm coaxial cable terminated with a BNC connector. AES3 unbalanced and AES-3id audio can be switched or routed using a video switcher with a minimum of 150 MHz (-3 dB, fully loaded) video bandwidth. - Optical – Plastic optical fiber using an F05 style connector, typically used in consumer audio applications. In many consumer products, this is often referred to as a “digital optical” connection type. TOSLINK is the most common implementation of this connection type.
AFL™ - Accu-RATE Frame Lock™. Extron's patented method of eliminating image tearing which is associated with scaling, especially when motion video is involved, and occurs when the input frame rate is slower or faster than the output frame rate and part of the old frame and part of the new frame are displayed at the same time during a refresh cycle. Extron Accu-RATE Frame Lock sets and locks the output frame rate to the input frame rate of a designated input and produces a tear-free output in a seamless switching system.
AGC - Automatic Gain Control. A circuit used to automatically control the level of the recorded or transmitted signal. It is sometimes called Automatic Level Control (ALC), or Automatic Volume Control (AVC).
Air Blown Fiber – ABF - Optical fiber installed through special tube cables by means of using pressurized air or nitrogen to "blow" bundles of fibers through individual tubes within the cable. Tube cables are usually preinstalled at the premises before installation of air blown fiber.
Air Polish - In fiber optics, this is the first step in polishing the connector using special fine grit film, after the fiber has been cleaved.
ALC - Automatic Level Control. In audio recording, a circuit used to control the volume or level of the recorded signal automatically without distortion due to overload. Sometimes called Automatic Gain Control (AGC), or Automatic Volume Control (AVC).
Aliasing - (1) Aliasing occurs when smooth curves and lines become rough or jagged because of a lower resolution device, or by an event. (2) In analog video, aliasing is typically caused by interference between the luma and chroma frequencies or between the chroma and field scanning frequencies. It appears as a moiré or herringbone pattern, straight lines that become wavy, or rainbow colors. Also see “Cross color.” (3) In digital video, insufficient sampling or poor filtering of the signal causes aliasing. Defects typically appear as jagged edges on diagonal lines and twinkling or brightening in picture detail.
All Dielectric - In fiber optics, this denotes the presence of only dielectric, or non-metal elements.
AM - Amplitude Modulation. A method of radio transmission, by which the information part of the signal causes the amplitude of a carrier frequency to vary without affecting the frequency.
Ambient Sound Level - Any environmental or background sound that exists before a new sound source is added. For example, in a school classroom, ambient sound may come from an adjacent hallway or playground, HVAC system, room lights, or another classroom. Ambient sound must be taken into consideration when designing a sound support system.
American National Standards Institute (ANSI) - ANSI is a private, non-profit organization that administers and coordinates the voluntary standardization and conformity assessment system in the US.
Amp - Ampere. The international base unit of electrical current that represents the rate flow of electric charges through a conductor. Symbolized by “A.” 1 amp is equal to the steady current produced by 1 volt applied across a resistance of 1 ohm.
Amplifier - An electronic device used to increase the voltage amplitude of a signal.
Amplifier classifications - Audio amplifiers are typically described by “class”. There are four primary classes used in A/V system designs: A, B, A/B, and D.
Amplitude - The level or strength of a signal as measured by the height of its waveform. Electronic waveforms can be displayed and measured on an oscilloscope.
Amplitude Modulation – AM - Amplitude modulation is also employed in fiber optics applications, in which light acts as a carrier signal with its amplitude varying in accordance to the signal being conveyed.
Anaerobic - For fiber optics, this describes a method of bonding between optical fibers via a non-heat, intrinsic chemical reaction within the adhesive material. By definition, an anaerobic adhesive does not require air to cure.
Analog - A continuously varying action or movement that takes time to change from one position to another. Standard audio and video signals are analog. An analog signal has an infinite number of levels between its highest and lowest value (unlike digital, in which changes are in steps).
Analog - A continuous range of values to represent information. An infinite resolution of values can be established in an analog system.
Analog control - A method using continuously varying voltage levels to provide control of equipment.
Analog Sunset - When used colloquially, may refer to the general trend of digital video technologies displacing analog, such as when US broadcast television switched to digital transmission, or the increasing use of DVI, HDMI, and DisplayPort video on PCs instead of RGB, etc. In a narrowly defined legal sense, the analog sunset refers to AACS licensing restrictions placed on Blu-ray Disc players where licensed players produced after 2010 must limit analog video output to standard definition, and licensed players produced after 2013 must not output any analog video, when playing protected content.
Anamorphic - A type of lens or adapter designed to produce a widescreen image from a condensed image on the film. Trademarked anamorphic systems include CinemaScope, VistaVision, and Panavision.
Anamorphic DVD - A DVD with a widescreen video image that has been horizontally squeezed to fit into a standard video frame, resulting in an image with higher resolution than letter boxing can produce. Anamorphic DVDs are designed for optimal display on 16:9 widescreen displays or video scalers with an anamorphic squeeze mode.
Anechoic chamber - An acoustic space without echo or reverberation. Often used for the acoustic testing of microphones and loudspeakers.
Angle of Incidence - The angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal.
Angled Physical Contact – APC - A specific technique for singlemode fiber applications where the endface of the fiber or ferrule is cut and polished at an 8 degree angle in order to increase contact surface area and help minimize return loss. APC connectors are typically green in color and are not used in multimode applications. They are also rarely used in digital applications. APC polished connectors are not compatible with UPC, SPC, or PC polished connectors. Intermixing APC polished connectors with UPC/SPC/PC polished connectors can damage the fiber optic cable or equipment.
Animations - Animations consist of motion image sequences produced synthetically on video processing or computing systems.
ANSI lumen - The common unit of measurement for the light output of a projector, as measured by ANSI, the American National Standards Institute. The higher the ANSI lumen rating, the brighter the projector. In general, there needs to be about a 30% differential in the ANSI lumen rating before the human eye can really notice an appreciable difference in brightness when two projectors are shown side by side. Determining the lumen output for a given application depends on five factors, (1) the level of ambient room light (2) the size of the audience, (3) the size of the projected image, (4) the quality of the projection screen, and (5) the amount of detail in the presentation material. Also see "Lumen."
Antialiasing - A technique in computer graphics for smoothing jagged edges by blending shades of color or gray along the edges. Some video devices, such as character generators, have an antialiasing feature to minimize aliasing through filtering and other techniques. Also see "Aliasing."
Aperture - The opening, usually an adjustable iris, that controls the amount of light passing through a lens. In motion picture cameras, the mask opening that defines the area of each frame exposed. In motion picture projectors, the mask opening that defines the area of each frame projected.
Aperture grill - A grill-like feature of Sony Trinitron CRT monitors and others licensed by Sony that controls the number of electrons hitting the phosphor coating on the screen.
Apple Cinema Display - One of the first very high resolution monitors on the market and one of the first to utilize a dual-link DVI connection. The 30" version provides a native resolution of 2560x1600 pixels.
Aramid Yarn - A woven strength member, with Kevlar® as a common brand, incorporated into fiber optic cable that provides tensile strength and protection.
Arc - In fiber optics, the discharge that may occur between the two electrodes of a fusion splicer.
Armored Cable - Cable that is protected with metal sheathing or rods below or between the cable jacketing to protect from damage due to adverse outdoor factors such as rodent attack.
ARP - Address Resolution Protocol. A protocol for assigning an IP address to a device based on the device’s MAC (Media Access Control), or physical machine address, that maintains a table showing the correlation between the two.
Artifacts - Visible corruption of the image or undesirable elements or defects in a video picture. These may occur naturally in the video process but must be eliminated to produce a high quality picture.
Artifacts - Any error in the perception or representation of any visual or aural information introduced by the involved equipment. Image artifacts appear as deviations from the original in the delivered image in video streaming systems.
ASCII - American Standard Code for Information Interchange. The standard code consisting of 7-bit coded characters (8 bits including parity check) used to exchange information between data processing systems, data communication systems, and associated equipment. The ASCII set contains control characters and graphic characters.
Aspect ratio - The relationship of the horizontal dimension to the vertical dimension of an image. In viewing screens, standard TV is 4:3, or 1.33:1; HDTV is 16:9, or 1.78:1. Sometimes the “:1” is implicit, making TV = 1.33 and HDTV = 1.78.
ASTA - Active Sync Termination Adapter. A VGA-style (15-pin HD connector) adapter that provides active circuits that shape up the horizontal and vertical sync signals. This adapter may be used to eliminate jitter and/or intermittent tearing in the displayed image. Most small digital projectors are designed to be near the video source and may not provide impedance matching.
Asynchronous - Intermittent, not synchronized or continuous. A conversational type of communication that allows the parties at each end to talk when they like instead of at a prescribed time. Used in videoconferencing.
ATM - Asynchronous Transfer Mode. In videoconferencing, a system for transmission and switching of digital signals through the telephone system. Also see "Asynchronous."
ATM - Asynchronous Transfer Mode. A standardized digital data transmission technology that is a cell-based switching technique which uses asynchronous time division multiplexing. This is the core protocol used over the SONET/SDH backbone of the ISDN (Integrated Services Digital Network).
ATSC - Advanced Television Systems Committee. The ATSC was formed to establish voluntary technical standards for advanced television systems, including digital high definition television (HDTV). The ATSC is supported by its members, who are subject to certain qualification requirements.
Attenuate/Attenuation - To reduce the amplitude (strength) or current of a signal.
Attenuation - In fiber optics, this is the loss of optical power as light passes through a fiber optic path. This loss can occur due to absorption, scattering, and excessive bending within the fiber, and can also be attributed to optical components such as connectors, splices, and splitters. Attenuation is usually expressed in dB/km.
Audio - Of or concerning the electronic transmission of sound, specifically the electrical currents representing a sound. (CF. Sound)
Audio follow - A term used when audio is tied to other signals, such as video, and they are switched together. The opposite of “breakaway.”
Audio frequency - Frequencies within the range of human hearing, about 20 Hz to 20 kHz.
Audio summing amplifier - A device that converts two-channel stereo audio signals into balanced/unbalanced one-channel mono audio signals.
Auto-focus - Automatic focus. A device in a projector or camera that uses light reflected from a surface to focus the image.
Auto-Image™ - An Extron technology for scan converters and signal processors that simplifies setup by executing image sizing, centering, and filtering adjustments with a single button push.
Auto-input switching - The feature that enables a product to detect which input has an active sync signal and switch to that input.
Automatic convergence - The automatic alignment of the red, green, and blue color images on a screen.
Automatic sync stripping - The automatic removal of sync signals from video channels. Typically, this is associated with removing the sync signal from the green channel, but it may apply to stripping the sync from all three video channels (Red, Green, and Blue).
Autosizing - Automatic picture sizing adjustment to compensate for different display modes, thus enabling the display system to center the picture and fill the screen.
Autoswitching - The feature that enables a product to detect which input has an active sync signal and switch to that input.
Avalanche Photodiode – APD - A type of photodiode, or optical signal transducer that converts light to an electrical signal, used in fiber optic receivers.
AWG - American Wire Gauge. A standard measurement for wire conductor diameter.
A/V - Audio visual, or audio video.
AACS – Advanced Access Content System - A digital rights management standard utilized with Blu-ray Disc and other optical formats. AACS incorporates two parts: a set of embedded decryption keys within the source device, and a set of keys encoded in the content that describes each of the playback devices licensed to utilize the content. This approach allows copyright holders to revoke the keys of a particular source device, thus preventing it from playing back future content. AACS also provides for a managed copy system, that is, a mechanism by which one or several, but not an unlimited number of copies can be legally made as backups, for storage on a media server, or for use on a portable device. The ICT – Image Constraint Token is a provision within AACS that allows the content provider to limit analog output resolutions.
AAP - Architectural Adapter Plate. Mountable metal plates available in hundreds of models offering popular pass-through audio, video, phone, data, power, and control connectors. Active AAPs are also available for power, control, and long distance signal transmission. Along with mounting options for maximum flexibility in placing connectors and controls within reach, these interchangeable components fit together to create an attractive and completely customizable A/V connectivity solution.
Absorption - The attenuation of light as it passes through fiber, similar to the resistive loss of an electrical signal as it passes through cable. Absorption is caused by impurities and defects in the fiber.
AC - Alternating Current. Electron flow that changes direction alternately.
AC coupled - A circuit design that does not pass the DC component of a signal, therefore it ignores DC offsets.
AC-3 - See "Dolby® Digital."
Acceptance Angle - In fiber optics, this is the maximum allowable angle of incidence for light entering a fiber measured from the center axis of the fiber. Incoming light must be directed below this angle in order to enter the core of the fiber and propagate along its length through total internal reflection.
Active crossover - A circuit that separates the audio signal into the appropriate frequency bands for the woofer, midrange, and tweeter. An active crossover is placed in the signal path ahead of the amplifier, where a passive crossover is placed between the amplifier and the speaker.
ADC - Analog to Digital Converter. A device that converts analog signals to digital signals.
Additive color process - Also called “RGB.” A color generation process used in video that combines red, green, and blue to make all colors. All three colors (red, green, and blue) at 100% combine to make white on a video screen; the absence of all three colors (0%) makes black. Also see "Subtractive color process."
ADSL - Asymmetrical Digital Subscriber Line. One of a number of DSL technologies, and the most common one. ADSL is designed to deliver more bandwidth downstream (from the central office to the customer site) than upstream.
ADSP™ - Advanced Digital Sync Processing™. Using sync processing to allow centering control (H-shift or V-shift) can create problems with some display devices because of the sync delay. This means the digital projector user may have to choose between a stable sync and centering control. Extron's ADSP restores the original sync timing relationship for a stable sync signal while allowing centering control.
ADTV - Advanced Definition Television. An early HDTV system proposed by the Advanced Television Research Consortium in 1992. Now superseded by US HDTV standards.
Aerial Cables - Optical fiber cables designed for outdoor installations on aerial supporting structures such as poles. They are specifically designed to withstand adverse conditions such as wind and ice loading, pollution, UV radiation, thermal cycling, stress, and aging.
AES – Advanced Encryption Standard - A data encryption standard adopted by the US Government and approved by the National Security Agency for top secret information. DCP, LLP, the licensing agency for HDCP, has adopted AES 128 encryption for the new HDCP 2.0 standard.
AES/EBU - Audio Engineering Society/European Broadcasting Union. A digital audio transfer standard. The AES and EBU developed the specifications for the standard. The AES/EBU digital interface is usually implemented using 3-pin XLR connectors, the same type of connector used in a professional microphone. One cable carries both left- and right-channel audio data to the receiving device. Also see "AES3."
AES3 - A digital audio standard defined by the Audio Engineering Society. The standard specifies several basic physical interconnections between devices: - Balanced - 3-conductor, 110 ohm cabling with an XLR connector, typically referred to as “AES/EBU audio.” - Unbalanced - 2-conductor, 75 ohm coaxial cable with an RCA connector, typically used in consumer audio applications. In many consumer products such as DVD players and A/V receivers, this is often referred to as a “digital coaxial” connection type. - AES-3id - A professional version of the 2-conductor 75 ohm coaxial cable terminated with a BNC connector. AES3 unbalanced and AES-3id audio can be switched or routed using a video switcher with a minimum of 150 MHz (-3 dB, fully loaded) video bandwidth. - Optical – Plastic optical fiber using an F05 style connector, typically used in consumer audio applications. In many consumer products, this is often referred to as a “digital optical” connection type. TOSLINK is the most common implementation of this connection type.
AFL™ - Accu-RATE Frame Lock™. Extron's patented method of eliminating image tearing which is associated with scaling, especially when motion video is involved, and occurs when the input frame rate is slower or faster than the output frame rate and part of the old frame and part of the new frame are displayed at the same time during a refresh cycle. Extron Accu-RATE Frame Lock sets and locks the output frame rate to the input frame rate of a designated input and produces a tear-free output in a seamless switching system.
AGC - Automatic Gain Control. A circuit used to automatically control the level of the recorded or transmitted signal. It is sometimes called Automatic Level Control (ALC), or Automatic Volume Control (AVC).
Air Blown Fiber – ABF - Optical fiber installed through special tube cables by means of using pressurized air or nitrogen to "blow" bundles of fibers through individual tubes within the cable. Tube cables are usually preinstalled at the premises before installation of air blown fiber.
Air Polish - In fiber optics, this is the first step in polishing the connector using special fine grit film, after the fiber has been cleaved.
ALC - Automatic Level Control. In audio recording, a circuit used to control the volume or level of the recorded signal automatically without distortion due to overload. Sometimes called Automatic Gain Control (AGC), or Automatic Volume Control (AVC).
Aliasing - (1) Aliasing occurs when smooth curves and lines become rough or jagged because of a lower resolution device, or by an event. (2) In analog video, aliasing is typically caused by interference between the luma and chroma frequencies or between the chroma and field scanning frequencies. It appears as a moiré or herringbone pattern, straight lines that become wavy, or rainbow colors. Also see “Cross color.” (3) In digital video, insufficient sampling or poor filtering of the signal causes aliasing. Defects typically appear as jagged edges on diagonal lines and twinkling or brightening in picture detail.
All Dielectric - In fiber optics, this denotes the presence of only dielectric, or non-metal elements.
AM - Amplitude Modulation. A method of radio transmission, by which the information part of the signal causes the amplitude of a carrier frequency to vary without affecting the frequency.
Ambient Sound Level - Any environmental or background sound that exists before a new sound source is added. For example, in a school classroom, ambient sound may come from an adjacent hallway or playground, HVAC system, room lights, or another classroom. Ambient sound must be taken into consideration when designing a sound support system.
American National Standards Institute (ANSI) - ANSI is a private, non-profit organization that administers and coordinates the voluntary standardization and conformity assessment system in the US.
Amp - Ampere. The international base unit of electrical current that represents the rate flow of electric charges through a conductor. Symbolized by “A.” 1 amp is equal to the steady current produced by 1 volt applied across a resistance of 1 ohm.
Amplifier - An electronic device used to increase the voltage amplitude of a signal.
Amplifier classifications - Audio amplifiers are typically described by “class”. There are four primary classes used in A/V system designs: A, B, A/B, and D.
Amplitude - The level or strength of a signal as measured by the height of its waveform. Electronic waveforms can be displayed and measured on an oscilloscope.
Amplitude Modulation – AM - Amplitude modulation is also employed in fiber optics applications, in which light acts as a carrier signal with its amplitude varying in accordance to the signal being conveyed.
Anaerobic - For fiber optics, this describes a method of bonding between optical fibers via a non-heat, intrinsic chemical reaction within the adhesive material. By definition, an anaerobic adhesive does not require air to cure.
Analog - A continuously varying action or movement that takes time to change from one position to another. Standard audio and video signals are analog. An analog signal has an infinite number of levels between its highest and lowest value (unlike digital, in which changes are in steps).
Analog - A continuous range of values to represent information. An infinite resolution of values can be established in an analog system.
Analog control - A method using continuously varying voltage levels to provide control of equipment.
Analog Sunset - When used colloquially, may refer to the general trend of digital video technologies displacing analog, such as when US broadcast television switched to digital transmission, or the increasing use of DVI, HDMI, and DisplayPort video on PCs instead of RGB, etc. In a narrowly defined legal sense, the analog sunset refers to AACS licensing restrictions placed on Blu-ray Disc players where licensed players produced after 2010 must limit analog video output to standard definition, and licensed players produced after 2013 must not output any analog video, when playing protected content.
Anamorphic - A type of lens or adapter designed to produce a widescreen image from a condensed image on the film. Trademarked anamorphic systems include CinemaScope, VistaVision, and Panavision.
Anamorphic DVD - A DVD with a widescreen video image that has been horizontally squeezed to fit into a standard video frame, resulting in an image with higher resolution than letter boxing can produce. Anamorphic DVDs are designed for optimal display on 16:9 widescreen displays or video scalers with an anamorphic squeeze mode.
Anechoic chamber - An acoustic space without echo or reverberation. Often used for the acoustic testing of microphones and loudspeakers.
Angle of Incidence - The angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal.
Angled Physical Contact – APC - A specific technique for singlemode fiber applications where the endface of the fiber or ferrule is cut and polished at an 8 degree angle in order to increase contact surface area and help minimize return loss. APC connectors are typically green in color and are not used in multimode applications. They are also rarely used in digital applications. APC polished connectors are not compatible with UPC, SPC, or PC polished connectors. Intermixing APC polished connectors with UPC/SPC/PC polished connectors can damage the fiber optic cable or equipment.
Animations - Animations consist of motion image sequences produced synthetically on video processing or computing systems.
ANSI lumen - The common unit of measurement for the light output of a projector, as measured by ANSI, the American National Standards Institute. The higher the ANSI lumen rating, the brighter the projector. In general, there needs to be about a 30% differential in the ANSI lumen rating before the human eye can really notice an appreciable difference in brightness when two projectors are shown side by side. Determining the lumen output for a given application depends on five factors, (1) the level of ambient room light (2) the size of the audience, (3) the size of the projected image, (4) the quality of the projection screen, and (5) the amount of detail in the presentation material. Also see "Lumen."
Antialiasing - A technique in computer graphics for smoothing jagged edges by blending shades of color or gray along the edges. Some video devices, such as character generators, have an antialiasing feature to minimize aliasing through filtering and other techniques. Also see "Aliasing."
Aperture - The opening, usually an adjustable iris, that controls the amount of light passing through a lens. In motion picture cameras, the mask opening that defines the area of each frame exposed. In motion picture projectors, the mask opening that defines the area of each frame projected.
Aperture grill - A grill-like feature of Sony Trinitron CRT monitors and others licensed by Sony that controls the number of electrons hitting the phosphor coating on the screen.
Apple Cinema Display - One of the first very high resolution monitors on the market and one of the first to utilize a dual-link DVI connection. The 30" version provides a native resolution of 2560x1600 pixels.
Aramid Yarn - A woven strength member, with Kevlar® as a common brand, incorporated into fiber optic cable that provides tensile strength and protection.
Arc - In fiber optics, the discharge that may occur between the two electrodes of a fusion splicer.
Armored Cable - Cable that is protected with metal sheathing or rods below or between the cable jacketing to protect from damage due to adverse outdoor factors such as rodent attack.
ARP - Address Resolution Protocol. A protocol for assigning an IP address to a device based on the device’s MAC (Media Access Control), or physical machine address, that maintains a table showing the correlation between the two.
Artifacts - Visible corruption of the image or undesirable elements or defects in a video picture. These may occur naturally in the video process but must be eliminated to produce a high quality picture.
Artifacts - Any error in the perception or representation of any visual or aural information introduced by the involved equipment. Image artifacts appear as deviations from the original in the delivered image in video streaming systems.
ASCII - American Standard Code for Information Interchange. The standard code consisting of 7-bit coded characters (8 bits including parity check) used to exchange information between data processing systems, data communication systems, and associated equipment. The ASCII set contains control characters and graphic characters.
Aspect ratio - The relationship of the horizontal dimension to the vertical dimension of an image. In viewing screens, standard TV is 4:3, or 1.33:1; HDTV is 16:9, or 1.78:1. Sometimes the “:1” is implicit, making TV = 1.33 and HDTV = 1.78.
ASTA - Active Sync Termination Adapter. A VGA-style (15-pin HD connector) adapter that provides active circuits that shape up the horizontal and vertical sync signals. This adapter may be used to eliminate jitter and/or intermittent tearing in the displayed image. Most small digital projectors are designed to be near the video source and may not provide impedance matching.
Asynchronous - Intermittent, not synchronized or continuous. A conversational type of communication that allows the parties at each end to talk when they like instead of at a prescribed time. Used in videoconferencing.
ATM - Asynchronous Transfer Mode. In videoconferencing, a system for transmission and switching of digital signals through the telephone system. Also see "Asynchronous."
ATM - Asynchronous Transfer Mode. A standardized digital data transmission technology that is a cell-based switching technique which uses asynchronous time division multiplexing. This is the core protocol used over the SONET/SDH backbone of the ISDN (Integrated Services Digital Network).
ATSC - Advanced Television Systems Committee. The ATSC was formed to establish voluntary technical standards for advanced television systems, including digital high definition television (HDTV). The ATSC is supported by its members, who are subject to certain qualification requirements.
Attenuate/Attenuation - To reduce the amplitude (strength) or current of a signal.
Attenuation - In fiber optics, this is the loss of optical power as light passes through a fiber optic path. This loss can occur due to absorption, scattering, and excessive bending within the fiber, and can also be attributed to optical components such as connectors, splices, and splitters. Attenuation is usually expressed in dB/km.
Audio - Of or concerning the electronic transmission of sound, specifically the electrical currents representing a sound. (CF. Sound)
Audio follow - A term used when audio is tied to other signals, such as video, and they are switched together. The opposite of “breakaway.”
Audio frequency - Frequencies within the range of human hearing, about 20 Hz to 20 kHz.
Audio summing amplifier - A device that converts two-channel stereo audio signals into balanced/unbalanced one-channel mono audio signals.
Auto-focus - Automatic focus. A device in a projector or camera that uses light reflected from a surface to focus the image.
Auto-Image™ - An Extron technology for scan converters and signal processors that simplifies setup by executing image sizing, centering, and filtering adjustments with a single button push.
Auto-input switching - The feature that enables a product to detect which input has an active sync signal and switch to that input.
Automatic convergence - The automatic alignment of the red, green, and blue color images on a screen.
Automatic sync stripping - The automatic removal of sync signals from video channels. Typically, this is associated with removing the sync signal from the green channel, but it may apply to stripping the sync from all three video channels (Red, Green, and Blue).
Autosizing - Automatic picture sizing adjustment to compensate for different display modes, thus enabling the display system to center the picture and fill the screen.
Autoswitching - The feature that enables a product to detect which input has an active sync signal and switch to that input.
Avalanche Photodiode – APD - A type of photodiode, or optical signal transducer that converts light to an electrical signal, used in fiber optic receivers.
AWG - American Wire Gauge. A standard measurement for wire conductor diameter.
Balanced input
An input circuit whose electrical midpoint is grounded.
Bandpass
A two-part filter that cuts both high and low frequencies to leave a band in the middle. A bandpass enclosure cuts high frequencies by acoustic cancellation and low frequencies by natural physical limitations on bass response.
Bandwidth
The range of frequencies covered by a driver or network.
Bass
Low frequencies; those below approximately 200 Hz.
Bi-wiring
Of or referring to a method of connecting the amplifier or receiver to the speaker in which separate wiring is run to the woofer and the tweeter, or in a three-way system, to the midrange driver.
Boost
To make louder (to increase the amplitude of); opposite of attenuation.
Bridging
Combining two channels of an amplifier to make one channel that’s more powerful.
An input circuit whose electrical midpoint is grounded.
Bandpass
A two-part filter that cuts both high and low frequencies to leave a band in the middle. A bandpass enclosure cuts high frequencies by acoustic cancellation and low frequencies by natural physical limitations on bass response.
Bandwidth
The range of frequencies covered by a driver or network.
Bass
Low frequencies; those below approximately 200 Hz.
Bi-wiring
Of or referring to a method of connecting the amplifier or receiver to the speaker in which separate wiring is run to the woofer and the tweeter, or in a three-way system, to the midrange driver.
Boost
To make louder (to increase the amplitude of); opposite of attenuation.
Bridging
Combining two channels of an amplifier to make one channel that’s more powerful.
Capacitor bank
Any network of capacitors connected in combination, yielding a desired characteristic.
Channel
In components and systems, a channel is a separate signal path. A four-channel amplifier has at least four separate inputs and four separate outputs.
Chrominance
The color portion of a video signal. The chrominance channel carries the color signal that is laid on top of the luminance information when creating a picture.
Coaxial
1. A speaker with one driver in front of (and on the same axis of) another driver. 2. An audio or video cable with a single center pin that acts as the lead and the outer shield that acts as a ground.
Coloration
Any change in the character of sound, such as the overemphasis on certain tones, that reduces naturalness.
Component Video
This signal is recorded or transmitted on three channels: one channel for luminance information, and two channels of color. Compared to S-Video signals, a component signal carries more color detail and eliminates rainbow patterns completely. DVD and DBS are component video sources.
Cone
A typical shape of a speaker driver.
Crossover
A component that divides an audio signal into two or more parts by frequency, sending, for example, low frequencies to one output and high frequencies to another. Crossovers are sometimes built into amplifiers or equalizers.
Crossover network
Following final amplification in a sound-reproduction system, an outboard circuit facilitates delivery of high- and low-frequency (AF) components to correct speakers. (Passes correct sounds to correct speakers.)
Crossover point
The frequency that appears in two adjacent outputs of a crossover (such as high and mid) at the same level. For example, if a two-way crossover is set for a crossover point of 100 Hz, a 100 Hz signal will be at the same level in both the high-pass output and the low-pass output.
Cut
To reduce, lower, attenuate, make less loud; opposite of boost.
Any network of capacitors connected in combination, yielding a desired characteristic.
Channel
In components and systems, a channel is a separate signal path. A four-channel amplifier has at least four separate inputs and four separate outputs.
Chrominance
The color portion of a video signal. The chrominance channel carries the color signal that is laid on top of the luminance information when creating a picture.
Coaxial
1. A speaker with one driver in front of (and on the same axis of) another driver. 2. An audio or video cable with a single center pin that acts as the lead and the outer shield that acts as a ground.
Coloration
Any change in the character of sound, such as the overemphasis on certain tones, that reduces naturalness.
Component Video
This signal is recorded or transmitted on three channels: one channel for luminance information, and two channels of color. Compared to S-Video signals, a component signal carries more color detail and eliminates rainbow patterns completely. DVD and DBS are component video sources.
Cone
A typical shape of a speaker driver.
Crossover
A component that divides an audio signal into two or more parts by frequency, sending, for example, low frequencies to one output and high frequencies to another. Crossovers are sometimes built into amplifiers or equalizers.
Crossover network
Following final amplification in a sound-reproduction system, an outboard circuit facilitates delivery of high- and low-frequency (AF) components to correct speakers. (Passes correct sounds to correct speakers.)
Crossover point
The frequency that appears in two adjacent outputs of a crossover (such as high and mid) at the same level. For example, if a two-way crossover is set for a crossover point of 100 Hz, a 100 Hz signal will be at the same level in both the high-pass output and the low-pass output.
Cut
To reduce, lower, attenuate, make less loud; opposite of boost.
Damping
Of or pertaining to the control of vibration by electrical or mechanical means.
Damping material
Any material added to the interior of a speaker enclosure to absorb unwanted sound and reduce the out-of-phase reflection to the driver
Decibel (dB)
Not a unit like inches, but a ratio-like percent, the Bel and the decibel define power differences. (One decibel is one tenth of a Bel.) One dB is a difference of 27%. A 3-dB difference is a difference of two times, or 100%; that’s why a 200-watt amplifier is only 3 dB more powerful than a 100-watt amp. A power difference of 1,000% is a 10-dB difference. A 60-dB difference is a difference of 1 million times, and so on. The decibel is used to compare power differences in voltage, current, watts, sound pressure, etc. One dB SPL is commonly accepted as the smallest difference that people can hear. The logarithmic nature of the decibel scale corresponds to the logarithmic nature of human hearing.
Delay
The time effect of distance (sound traveling through space is delayed according to the distance it travels). People perceive spaciousness by the delay between the arrival of direct sound and reflected sound (larger spaces cause longer delays).
Diaphragm
The part of a dynamic loudspeaker, attached to the voice coil, that produces sound. It usually has the shape of a cone or dome.
Dipole
Dipole speakers are a popular choice for surround speaker application and a THX requirement. Each speaker enclosure consists of two speaker arrays facing opposite each other and wire out of phase from one another to create a more ambient or nondirectional soundfield.
Dispersion
The degree of sound that is spread over the listening area.
Distortion
Nonlinear and unwanted changes in an audio signal, often not including the addition of noise, but including harmonic, intermodulation, transient intermodulation, phase, and frequency distortion.
DNR
Dynamic Noise Reduction; a signal-processing circuit that reduces the level of high frequencies. Unlike Dolby NR, DNR doesn’t require processing during recording; it works on any signal.
Dolby B
A noise-reduction system that increases the level of high frequencies during recording and decreases them during playback.
Dolby C
An improvement on Dolby B that provides about twice as much noise reduction.
Dome
A type of speaker-driver shape usually used for tweeters (convex, not concave).
Driver
A speaker without an enclosure; also used to refer to the part of the speaker that compresses and rarefies the air (the diaphragm).
DSP
Abbreviation of digital signal processing.
DVD
Abbreviation for Digital Video Disc.
Dynamic range
The difference between the smallest possible signal and the largest; expressed in decibels.
Of or pertaining to the control of vibration by electrical or mechanical means.
Damping material
Any material added to the interior of a speaker enclosure to absorb unwanted sound and reduce the out-of-phase reflection to the driver
Decibel (dB)
Not a unit like inches, but a ratio-like percent, the Bel and the decibel define power differences. (One decibel is one tenth of a Bel.) One dB is a difference of 27%. A 3-dB difference is a difference of two times, or 100%; that’s why a 200-watt amplifier is only 3 dB more powerful than a 100-watt amp. A power difference of 1,000% is a 10-dB difference. A 60-dB difference is a difference of 1 million times, and so on. The decibel is used to compare power differences in voltage, current, watts, sound pressure, etc. One dB SPL is commonly accepted as the smallest difference that people can hear. The logarithmic nature of the decibel scale corresponds to the logarithmic nature of human hearing.
Delay
The time effect of distance (sound traveling through space is delayed according to the distance it travels). People perceive spaciousness by the delay between the arrival of direct sound and reflected sound (larger spaces cause longer delays).
Diaphragm
The part of a dynamic loudspeaker, attached to the voice coil, that produces sound. It usually has the shape of a cone or dome.
Dipole
Dipole speakers are a popular choice for surround speaker application and a THX requirement. Each speaker enclosure consists of two speaker arrays facing opposite each other and wire out of phase from one another to create a more ambient or nondirectional soundfield.
Dispersion
The degree of sound that is spread over the listening area.
Distortion
Nonlinear and unwanted changes in an audio signal, often not including the addition of noise, but including harmonic, intermodulation, transient intermodulation, phase, and frequency distortion.
DNR
Dynamic Noise Reduction; a signal-processing circuit that reduces the level of high frequencies. Unlike Dolby NR, DNR doesn’t require processing during recording; it works on any signal.
Dolby B
A noise-reduction system that increases the level of high frequencies during recording and decreases them during playback.
Dolby C
An improvement on Dolby B that provides about twice as much noise reduction.
Dome
A type of speaker-driver shape usually used for tweeters (convex, not concave).
Driver
A speaker without an enclosure; also used to refer to the part of the speaker that compresses and rarefies the air (the diaphragm).
DSP
Abbreviation of digital signal processing.
DVD
Abbreviation for Digital Video Disc.
Dynamic range
The difference between the smallest possible signal and the largest; expressed in decibels.
Efficiency Rating
The loudspeaker parameter that shows the level of sound output when measured at a prescribed distance with a standard amount of energy fed into the speaker. Efficiency rating standard is 1 watt at 1 meter and is measured in decibels.
Enclosure
The container of air that is pressurized by the backward motion of a speaker driver.
EQ
Equalization or Equalizer.
Equalization
Loosely any type of relative frequency adjustment. Specifically, the process of changing the frequency balance of a signal so acoustical energy is proportional to the electrical input.
Equalizer
A component designed to alter the frequency balance of an audio signal. Equalizers may be standard, graphic, parametric, or a combination of these types.
The loudspeaker parameter that shows the level of sound output when measured at a prescribed distance with a standard amount of energy fed into the speaker. Efficiency rating standard is 1 watt at 1 meter and is measured in decibels.
Enclosure
The container of air that is pressurized by the backward motion of a speaker driver.
EQ
Equalization or Equalizer.
Equalization
Loosely any type of relative frequency adjustment. Specifically, the process of changing the frequency balance of a signal so acoustical energy is proportional to the electrical input.
Equalizer
A component designed to alter the frequency balance of an audio signal. Equalizers may be standard, graphic, parametric, or a combination of these types.
Feedback
The transmission of current or voltage from the output of a socket or device back to the input, where it interacts with the input signal to modify operation of the device. Feedback is positive when it’s in phase with the input, and negative when it’s out of phase.
Flat response
The reproduction of sound without altering the intensity of any part of the frequency range.
Frequency
How often something happens. Audio frequencies are commonly defined as ranging from 20 to 20,000 cycles per second (Hz), assuming that sound waves that change the air pressure 20 or 20,000 times each second can be heard.
Frequency response
A measure of what frequencies can be reproduced and how accurately they are reproduced. A measurement of 20 to 20,000 Hz ±3 dB means that frequencies between 20 Hz and 20,000 Hz can be reproduced no more than 3 dB too loud (twice as loud) or 3 dB too soft (half as loud).
Fs
The frequency resonance of a driver in free-air.
Full range
A speaker designed to reproduce the full range of audio frequencies. Most full-range speakers can’t reproduce very low or very high frequencies loud enough, but reproduce mostly midrange frequencies.
The transmission of current or voltage from the output of a socket or device back to the input, where it interacts with the input signal to modify operation of the device. Feedback is positive when it’s in phase with the input, and negative when it’s out of phase.
Flat response
The reproduction of sound without altering the intensity of any part of the frequency range.
Frequency
How often something happens. Audio frequencies are commonly defined as ranging from 20 to 20,000 cycles per second (Hz), assuming that sound waves that change the air pressure 20 or 20,000 times each second can be heard.
Frequency response
A measure of what frequencies can be reproduced and how accurately they are reproduced. A measurement of 20 to 20,000 Hz ±3 dB means that frequencies between 20 Hz and 20,000 Hz can be reproduced no more than 3 dB too loud (twice as loud) or 3 dB too soft (half as loud).
Fs
The frequency resonance of a driver in free-air.
Full range
A speaker designed to reproduce the full range of audio frequencies. Most full-range speakers can’t reproduce very low or very high frequencies loud enough, but reproduce mostly midrange frequencies.
Graphic
A type of equalizer with sliding controls that create a pattern representing a graph of the frequency-response changes. Raising sliders boosts the affected frequencies; lowering sliders cuts (attenuates) the affected frequencies.
Gray scale
A reference scale for use in black-and-white television and video-display images, consisting of several defined levels of brightness with natural color.
A type of equalizer with sliding controls that create a pattern representing a graph of the frequency-response changes. Raising sliders boosts the affected frequencies; lowering sliders cuts (attenuates) the affected frequencies.
Gray scale
A reference scale for use in black-and-white television and video-display images, consisting of several defined levels of brightness with natural color.
Harmonic distortion
The generation of harmonics by the circuit or device by which the signal is processed.
HDTV
Abbreviation of High Definition Television.
High (frequencies)
Treble frequencies; those over approximately 3,150 Hz.
High pass
A filter that lets high frequencies go through, and attenuates low frequencies. Same as low cut.
Horn
A type of speaker that often looks like a horn. These speakers have very small drivers and very large mouths; the horn shape serves to gradually match the high impedance of the driver to the low impedance of the air.
Hz
Short for hertz; cycles per second. Something that repeats a cycle once each second is moving at a rate of 1 Hz.
The generation of harmonics by the circuit or device by which the signal is processed.
HDTV
Abbreviation of High Definition Television.
High (frequencies)
Treble frequencies; those over approximately 3,150 Hz.
High pass
A filter that lets high frequencies go through, and attenuates low frequencies. Same as low cut.
Horn
A type of speaker that often looks like a horn. These speakers have very small drivers and very large mouths; the horn shape serves to gradually match the high impedance of the driver to the low impedance of the air.
Hz
Short for hertz; cycles per second. Something that repeats a cycle once each second is moving at a rate of 1 Hz.
Interconnects
Also called RCA plug and phono plug. A plug designed especially for the quick connection and disconnection of coaxial cables used with audio and other low frequency devices.
Interlace
In CRT displays, every second field/frame is scanned between the first field/frame. Usually, this process divides and presents each video frame as two fields, as if the field was raked by a comb. The first field presents the odd lines, the second field represents the even lines. The fields are aligned and timed so that, with a still image, the human eye blurs the two fields together and sees them as one. Interlace scanning allows only half the lines to be transmitted and presented at any given moment. A 1080i HDTV signal transmits and displays only 540 lines per 60th of a second. 480i NTSC transmits and displays only 240 lines per 60th of a second.
Also called RCA plug and phono plug. A plug designed especially for the quick connection and disconnection of coaxial cables used with audio and other low frequency devices.
Interlace
In CRT displays, every second field/frame is scanned between the first field/frame. Usually, this process divides and presents each video frame as two fields, as if the field was raked by a comb. The first field presents the odd lines, the second field represents the even lines. The fields are aligned and timed so that, with a still image, the human eye blurs the two fields together and sees them as one. Interlace scanning allows only half the lines to be transmitted and presented at any given moment. A 1080i HDTV signal transmits and displays only 540 lines per 60th of a second. 480i NTSC transmits and displays only 240 lines per 60th of a second.
Keystoning
A form of video image distortion in which the top of the picture is wider than the bottom, or vice versa. The image is shaped like a trapezoid, rather than a rectangle.
kHz
One thousand Hz; 1 kHz equals 1,000 Hz and 20 kHz is 20,000 Hz.
Kintoscope
A motion picture projector.
A form of video image distortion in which the top of the picture is wider than the bottom, or vice versa. The image is shaped like a trapezoid, rather than a rectangle.
kHz
One thousand Hz; 1 kHz equals 1,000 Hz and 20 kHz is 20,000 Hz.
Kintoscope
A motion picture projector.
L-pad
A variable-resistance control that puts one element of resistance in series with the load and another element in parallel. This permits the L-pad to vary the signal to a driver while maintaining constant impedance at its input.
LCD
Liquid Crystal Displays are a transmissive device. Light isn’t created by the liquid crystals, but transmitted through it. The display consists of two polarizing transparent panels and a liquid crystal surface sandwiched in between. Voltage is applied to certain areas, causing the crystal to turn dark. A light source behind the panel is transmitted through transparent crystals and is partially blocked by dark crystals. Because the light is only partially blocked in dark areas, LCDs aren’t able to create deep blacks; therefore, it can’t generally create a considerable contrast. Resolution is limited by the panel array. LCDs are capable of substantial light output.
Letterbox
Format used widely on, laserdisc and some DVDs to fit widescreen movies (1.85:1 and 2.35:1) on the average, 1.33:1 TV screen. The image is shrunk to fit the screen, leaving blank space on the top and bottom. This process sacrifices some vertical detail that must be used to record the black bars.
Line level (low level)
A level of electrical pressure too low to make speakers move sufficiently (from 25 millivolts up to about 4 or even 5 volts). Amplifiers receive line-level signals and amplify them to speaker level.
Loop
An electrical circuit consisting of elements connected in series.
Low (frequencies)
Bass frequencies; those below approximately 200 Hz.
Low pass
A filter that lets low frequencies go through, but doesn’t let high frequencies go through. Same as high cut.
Luminance
The black and white portion of a video signal. The luminance channel carries the detail. The color channel is laid on top of the luminance signal when creating a picture. Having a separate luminance channel ensures compatibility with black and white televisions.
A variable-resistance control that puts one element of resistance in series with the load and another element in parallel. This permits the L-pad to vary the signal to a driver while maintaining constant impedance at its input.
LCD
Liquid Crystal Displays are a transmissive device. Light isn’t created by the liquid crystals, but transmitted through it. The display consists of two polarizing transparent panels and a liquid crystal surface sandwiched in between. Voltage is applied to certain areas, causing the crystal to turn dark. A light source behind the panel is transmitted through transparent crystals and is partially blocked by dark crystals. Because the light is only partially blocked in dark areas, LCDs aren’t able to create deep blacks; therefore, it can’t generally create a considerable contrast. Resolution is limited by the panel array. LCDs are capable of substantial light output.
Letterbox
Format used widely on, laserdisc and some DVDs to fit widescreen movies (1.85:1 and 2.35:1) on the average, 1.33:1 TV screen. The image is shrunk to fit the screen, leaving blank space on the top and bottom. This process sacrifices some vertical detail that must be used to record the black bars.
Line level (low level)
A level of electrical pressure too low to make speakers move sufficiently (from 25 millivolts up to about 4 or even 5 volts). Amplifiers receive line-level signals and amplify them to speaker level.
Loop
An electrical circuit consisting of elements connected in series.
Low (frequencies)
Bass frequencies; those below approximately 200 Hz.
Low pass
A filter that lets low frequencies go through, but doesn’t let high frequencies go through. Same as high cut.
Luminance
The black and white portion of a video signal. The luminance channel carries the detail. The color channel is laid on top of the luminance signal when creating a picture. Having a separate luminance channel ensures compatibility with black and white televisions.
MHz
Short for megahertz, which is 1 million Hz.
Midbass
The middle of the bass part of the frequency range, from approximately 50 to 100 Hz (upper bass would be from 100 to 200 Hz). Also used for drivers designed to reproduce both bass and midrange frequencies.
Midrange
The middle of the audio frequency range, from approximately 200 to 3,150 Hz.
Mono
Monophonic sound. A method of recording or reproducing sound in which sound from all directions is blended into a single channel.
Short for megahertz, which is 1 million Hz.
Midbass
The middle of the bass part of the frequency range, from approximately 50 to 100 Hz (upper bass would be from 100 to 200 Hz). Also used for drivers designed to reproduce both bass and midrange frequencies.
Midrange
The middle of the audio frequency range, from approximately 200 to 3,150 Hz.
Mono
Monophonic sound. A method of recording or reproducing sound in which sound from all directions is blended into a single channel.
Noise
An unwanted signal such as hiss, hum, whine, static, buzzing, etc.
An unwanted signal such as hiss, hum, whine, static, buzzing, etc.
Octave
The difference between two frequencies where one is twice the other. For example, 200 Hz is an octave higher than 100 Hz.
Ohm
A measure of how much something resists (impedes) the flow of electricity. Larger numbers mean more resistance.
The difference between two frequencies where one is twice the other. For example, 200 Hz is an octave higher than 100 Hz.
Ohm
A measure of how much something resists (impedes) the flow of electricity. Larger numbers mean more resistance.
Parametric
A type of equalizer with adjustable parameters, such as center frequency and bandwidth (Q), as well as amplitude.
Passive radiator
An undriven loudspeaker cone that is mounted in a bass-reflex (sealed) enclosure with other speakers.
Phase
Time.
Piezo
A type of speaker driver that creates sound when a quartz crystal receives electrical energy.
Pixel
Contraction of a picture element. The smallest bit of data in a video image. The smaller the size of the pixels in an image, the greater the resolution.
Polarity
The 180-degree difference in the phase of audio signals that must be observed when wiring speakers.
Port
An aperture in a loudspeaker enclosure used to help tune output. A ported enclosure is also called vented or bass reflex.
Power output
A measure, usually in watts, of how much energy is produced by a component.
Preamplifier
A control and switching component that may include equalization functions. The preamp comes in the signal chain before the amplifiers.
Presets
Memory locations in a tuner where radio-station frequencies are stored.
Programming
The ability to play tracks in a specified order.
Progressive scan
Each frame of a video image is complete, from top to bottom, not interlaced. For example, 480p means that each image frame is made of 480 horizontal lines drawn vertically. Computer images are all progressively scanned. Requires more bandwidth (twice as much vertical information) and a faster horizontal scan frequency than interlace images.
A type of equalizer with adjustable parameters, such as center frequency and bandwidth (Q), as well as amplitude.
Passive radiator
An undriven loudspeaker cone that is mounted in a bass-reflex (sealed) enclosure with other speakers.
Phase
Time.
Piezo
A type of speaker driver that creates sound when a quartz crystal receives electrical energy.
Pixel
Contraction of a picture element. The smallest bit of data in a video image. The smaller the size of the pixels in an image, the greater the resolution.
Polarity
The 180-degree difference in the phase of audio signals that must be observed when wiring speakers.
Port
An aperture in a loudspeaker enclosure used to help tune output. A ported enclosure is also called vented or bass reflex.
Power output
A measure, usually in watts, of how much energy is produced by a component.
Preamplifier
A control and switching component that may include equalization functions. The preamp comes in the signal chain before the amplifiers.
Presets
Memory locations in a tuner where radio-station frequencies are stored.
Programming
The ability to play tracks in a specified order.
Progressive scan
Each frame of a video image is complete, from top to bottom, not interlaced. For example, 480p means that each image frame is made of 480 horizontal lines drawn vertically. Computer images are all progressively scanned. Requires more bandwidth (twice as much vertical information) and a faster horizontal scan frequency than interlace images.
Q
The magnification of resonance factor of any resonant device or circuit. A driver with a high Q is more resonant than a driver with a low Q.
Qes
The electrical Q of the driver.
Qms
The mechanical Q of the driver.
Qts
The total Q of the driver at fs.
Quasiparametric
A type of equalizer with adjustable center frequency or bandwidth as well as amplitude.
The magnification of resonance factor of any resonant device or circuit. A driver with a high Q is more resonant than a driver with a low Q.
Qes
The electrical Q of the driver.
Qms
The mechanical Q of the driver.
Qts
The total Q of the driver at fs.
Quasiparametric
A type of equalizer with adjustable center frequency or bandwidth as well as amplitude.
Raw speakers
Speakers that are separate, not part of a multidriver set, combined with other drivers (like coaxials), or mounted on a connecting surface (like plates).
RCA jacks
Receptacles for RCA cables carrying line-level audio signals.
Receiver
Any component that receives broadcast signals.
Resonance frequency
The frequency at which any system vibrates naturally when excited by a stimulus. A tuning fork, for example, resonates at a specific frequency when struck.
Reverberation
The stretching of time a sound is audible by reflections of the, sound within a closed space.
Ribbon speaker
A loudspeaker that consists of a thin, corrugated, metallic ribbon suspended in a magnetic field. The ribbon acts electrically like a low-impedance voice coil and mechanically as a diaphragm.
RMS
Abbreviation for ROOT MEAN SQUARE; the square root of the arithmetic mean (average) of the square’s set of values.
Speakers that are separate, not part of a multidriver set, combined with other drivers (like coaxials), or mounted on a connecting surface (like plates).
RCA jacks
Receptacles for RCA cables carrying line-level audio signals.
Receiver
Any component that receives broadcast signals.
Resonance frequency
The frequency at which any system vibrates naturally when excited by a stimulus. A tuning fork, for example, resonates at a specific frequency when struck.
Reverberation
The stretching of time a sound is audible by reflections of the, sound within a closed space.
Ribbon speaker
A loudspeaker that consists of a thin, corrugated, metallic ribbon suspended in a magnetic field. The ribbon acts electrically like a low-impedance voice coil and mechanically as a diaphragm.
RMS
Abbreviation for ROOT MEAN SQUARE; the square root of the arithmetic mean (average) of the square’s set of values.
Sealed
A type of speaker enclosure that doesn’t allow the pressure generated by the back of the diaphragm to leave the enclosure.
Sensitivity (with input of 1 watt at 1 meter)
A measure (in decibels of sound-pressure level) of how much sound comes out when 1 watt of power is put in. The measuring microphone is placed one meter away from the speaker.
Signal
A variation in an electrical current that represents pressure changes (sound). Most audio signals are alternating currents, reversing direction according to how often the signal crosses zero level.
Signal-to-noise ratio
A measure of how much louder the signal (such as music) is, in comparison to the noise (such as hiss). Larger numbers are better.
Skip
A CD feature that finds the start of a desired track.
Slope
The rate of boost or attenuation expressed in decibels per octave. Steeper slopes (larger numbers) are usually better.
Soft dome tweeter
A tweeter that uses a fabric dome as the radiating diaphragm.
Sound
Changing pressure. Pressure that changes too slowly to be heard is infrasonic; pressure that changes too quickly to be heard is ultrasonic.
Soundfield
The total acoustical characteristics of a space, such as ambiance; number, timing, and relative level of reflections; ratio of direct to reflected sound; RT-6 time; etc.
Soundstage
The area that seems to be occupied by sonic images. Like a real stage, a soundstage should have width, depth, and height.
Speaker
A component that turns electrical energy into acoustical energy.
Speaker level
Signal strength sufficient to drive speakers (greater than line level).
Spider
The part of the loudspeaker that holds the diaphragm in place, and allows it to move when activated. Also called suspension.
SPL
Sound-pressure level, measured in dB. More is louder. May be weighted or unweighted.
Standard equalizer
An equalizer that doesn’t have sliders, whose positions represent boost or cut and doesn’t have variable parameters (such as center frequency or bandwidth), but fixed center frequencies and fixed bandwidth; relative amplitude is usually controlled by knobs.
Subwoofer
A speaker driver designed to reproduce very low frequencies, usually those under about 100 Hz. Often larger than 6.5 inches in diameter. However, since this is a relative term, even a 15-inch driver in a two-way system is really a woofer, not a subwoofer.
A type of speaker enclosure that doesn’t allow the pressure generated by the back of the diaphragm to leave the enclosure.
Sensitivity (with input of 1 watt at 1 meter)
A measure (in decibels of sound-pressure level) of how much sound comes out when 1 watt of power is put in. The measuring microphone is placed one meter away from the speaker.
Signal
A variation in an electrical current that represents pressure changes (sound). Most audio signals are alternating currents, reversing direction according to how often the signal crosses zero level.
Signal-to-noise ratio
A measure of how much louder the signal (such as music) is, in comparison to the noise (such as hiss). Larger numbers are better.
Skip
A CD feature that finds the start of a desired track.
Slope
The rate of boost or attenuation expressed in decibels per octave. Steeper slopes (larger numbers) are usually better.
Soft dome tweeter
A tweeter that uses a fabric dome as the radiating diaphragm.
Sound
Changing pressure. Pressure that changes too slowly to be heard is infrasonic; pressure that changes too quickly to be heard is ultrasonic.
Soundfield
The total acoustical characteristics of a space, such as ambiance; number, timing, and relative level of reflections; ratio of direct to reflected sound; RT-6 time; etc.
Soundstage
The area that seems to be occupied by sonic images. Like a real stage, a soundstage should have width, depth, and height.
Speaker
A component that turns electrical energy into acoustical energy.
Speaker level
Signal strength sufficient to drive speakers (greater than line level).
Spider
The part of the loudspeaker that holds the diaphragm in place, and allows it to move when activated. Also called suspension.
SPL
Sound-pressure level, measured in dB. More is louder. May be weighted or unweighted.
Standard equalizer
An equalizer that doesn’t have sliders, whose positions represent boost or cut and doesn’t have variable parameters (such as center frequency or bandwidth), but fixed center frequencies and fixed bandwidth; relative amplitude is usually controlled by knobs.
Subwoofer
A speaker driver designed to reproduce very low frequencies, usually those under about 100 Hz. Often larger than 6.5 inches in diameter. However, since this is a relative term, even a 15-inch driver in a two-way system is really a woofer, not a subwoofer.
THD
Total harmonic distortion.
Toroidal coil
A coil wound in a form that is shaped like a donut. The form is made of powered iron or ferrite. Toroidal coils have certain advantages over solenoidal coils: greater inductance for given physical size, better isolation properties, and higher Q factor.
Transducer
Any device that converts one quantity into another quantity, specifically when one of the quantities is electrical. Thus, a loudspeaker converts electrical impulses into sound, a microphone converts sound into electrical impulses, a photocell converts light into electricity, etc.
Treble
The higher part of the audio signal range, approximately 3,150 Hz on up.
Tuner
A component (or section of one) that receives radio signals and tunes in one from many.
Tweaking
Of or referring to any refinement that an audio professional or enthusiast can make to improve the naturalness of sound reproduction from a system no matter how great the effort nor how small the improvement.
Tweeter
A speaker driver designed to reproduce very high frequencies, those over approximately 5,000 to 10,000 Hz.
Total harmonic distortion.
Toroidal coil
A coil wound in a form that is shaped like a donut. The form is made of powered iron or ferrite. Toroidal coils have certain advantages over solenoidal coils: greater inductance for given physical size, better isolation properties, and higher Q factor.
Transducer
Any device that converts one quantity into another quantity, specifically when one of the quantities is electrical. Thus, a loudspeaker converts electrical impulses into sound, a microphone converts sound into electrical impulses, a photocell converts light into electricity, etc.
Treble
The higher part of the audio signal range, approximately 3,150 Hz on up.
Tuner
A component (or section of one) that receives radio signals and tunes in one from many.
Tweaking
Of or referring to any refinement that an audio professional or enthusiast can make to improve the naturalness of sound reproduction from a system no matter how great the effort nor how small the improvement.
Tweeter
A speaker driver designed to reproduce very high frequencies, those over approximately 5,000 to 10,000 Hz.
Underlap
When the crossover point is more than 3 dB below the unattenuated level.
When the crossover point is more than 3 dB below the unattenuated level.
VAS
The volume of air that offers the same degree of restoring force on the cone as that of the cone’s suspension.
Volt
The unit of electrical potential, or difference in electrical pressure, expressing the difference between two electrical charges. Voltage is the force that makes electrons move from where they are overcrowded to where they are scarce. It isn’t a measure of how many electrons are moving. (that’s electrical current, which is measured in amperes.)
The volume of air that offers the same degree of restoring force on the cone as that of the cone’s suspension.
Volt
The unit of electrical potential, or difference in electrical pressure, expressing the difference between two electrical charges. Voltage is the force that makes electrons move from where they are overcrowded to where they are scarce. It isn’t a measure of how many electrons are moving. (that’s electrical current, which is measured in amperes.)
Watt
A unit of power or energy. One horsepower is equal to 745.7 watts.
Woofer
A speaker driver designed to reproduce low frequencies.
Wow-and-flutter
A measurement of speed instability usually applied to cassette transports. Wow is slow-speed variations, and flutter is fast-speed variations. Lower percentages are better.
A unit of power or energy. One horsepower is equal to 745.7 watts.
Woofer
A speaker driver designed to reproduce low frequencies.
Wow-and-flutter
A measurement of speed instability usually applied to cassette transports. Wow is slow-speed variations, and flutter is fast-speed variations. Lower percentages are better.
Xmax
Length of voice coil winding; thickness of top/bottom plate.
Length of voice coil winding; thickness of top/bottom plate.
Z meter
A device used for measuring impedances. Instruments of this kind take four principal forms:
1. a direct-reading meter resembling an ohmmeter;
2. an adjustable circuit manipulated somewhat like a bridge that compares an unknown impedance with a standard resistance;
3. an impedance bridge for evaluating reactive and resistive components of an unknown impedance;
4. a section of transmission line used with a signal source and voltmeter for measuring impedance in terms of a standard resistor and/or standing waves.
A device used for measuring impedances. Instruments of this kind take four principal forms:
1. a direct-reading meter resembling an ohmmeter;
2. an adjustable circuit manipulated somewhat like a bridge that compares an unknown impedance with a standard resistance;
3. an impedance bridge for evaluating reactive and resistive components of an unknown impedance;
4. a section of transmission line used with a signal source and voltmeter for measuring impedance in terms of a standard resistor and/or standing waves.