Back to GLOSSARY
AC line frequency - The frequency of the alternating current power line measured in Hertz (Hz), usually 50 or 60Hz.
Alternating Current - Electrical current that reverses its direction of flow at regular intervals.
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.
Analog signal - Any variable signal continuous in both time and amplitude rather than of a pulsed or discrete nature
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.
Armored Cable - Cable that is protected with metal sheathing or rods below or between the cables jacketing to protect from damage due to adverse outdoor factors such as rodent attack.
A/D
Analog to Digital (converter). A device that converts an analog signal to a digital value.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 line frequency - The frequency of the alternating current power line measured in Hertz (Hz), usually 50 or 60Hz.
AC coupled
- A circuit design that does not pass the DC component of a signal, therefore it ignores DC offsets.Acceptance Angle
- In fiber optics, this is the critical angle, 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.Accuracy
- Closeness between the value indicated by a measuring instrument and the corresponding true value. Sensor accuracy is based on US NIST (NBS) standards.Accuracy - Calibration Accuracy
- Closeness between the value indicated by a measuring instrument and a physical constant or known standard.Accuracy - Control Accuracy
- The ability to maintain a process at the desired setting. This is a function of the entire system, including sensors, controllers, heaters, loads, and inefficiencies.Accuracy - Indication Accuracy
- Closeness between the displayed value and a measured value. Usually expressed as a + or -, a percent of span or number of digits.Accuracy - Setting Accuracy
- Closeness between the value established by an input device, such as a dial, and the desired value. Usually expressed as a percent of span or number of digits.Action
- The response of an output when the process variable is changed. See also direct action, reverse action.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.Actual
- The present value of the controlled variable.Actuator
- A controlled hardware device used to implement change in a processAdapter
- A device used to make electrical or mechanical connections between items not originally intended for use togetherADC
- 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.Address
- A numerical identifier for a controller when used in computer communications.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 AutomaticVolume 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.Alarm - Deviation Alarm
- Warns that a process has exceeded or fallen below a certain range around the set point. Alarms can be referenced at a fixed number of degrees, plus or minus, from a set point.Alarm - Process Alarm
- Warns that process values exceed the process alarm setting. A fixed value independent of set point.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.Alternating Current - Electrical current that reverses its direction of flow at regular intervals.
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.Ambient Sound List
- 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.Ambient Temperature
- The temperature of the encompassing atmosphere, including the environment and air surrounding the equipment in use.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
- a device that enables an input signal to control power from a source independent of the signal and thus be capable of delivering an output that bears some relationship to, and is generally greater than, the input signalAmplifier 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 control
- A method using continuously varying voltage levels to provide control of equipmentAnalog signal - Any variable signal continuous in both time and amplitude rather than of a pulsed or discrete nature
Analog transmission
- The transmission of data as a continuous signal, as opposed to an on/off digital signal.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 Display Port 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 normalAngled Physical Contact
– APC - A specific technique for single mode fiber applications where the end face 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."Anti-reset windup
- This feature of the PID controller prevents the integral (reset) circuit from operating when the temperature is outside the proportional band, thus stabilizing the system.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 cables jacketing to protect from damage due to adverse outdoor factors such as rodent attack.
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