CAT 5e-Enhanced Category 5—Cat 5e (Cat 5 enhanced) is currently the most commonly used in new installations. It’s designed to greatly reduce crosstalk. Cat 5e is better at keeping signals on different circuits or channels from interfering with each other. A step above Cat 5, it can handle 1000 Mbps speeds (gigabit Ethernet) at 100 MHz.
CAD-Computer Aided Design—The use of the computer system for designing, such as in architectural and engineering applications.
Calibration—The act of fine-tuning an audio or video component for correct performance. In an audio system, calibration includes setting the individual channel levels. In video, calibration means setting a video display device to display the correct color, brightness, tint, contrast, and other parameters.
Camcorder—The combination of a camera and a video recorder in one device. It permits easy and rapid simultaneous photography and recording. It is available in most video formats, VHS, VHS-C*, Beta*, 8-mm video*, Hi-8*, Super-VHS*, DV*, etc.
Camera Breakout—A single camera cable handling the following signals: video, audio, DC power supply, remote control line, tally* control and others. A camera breakout setup allows various signals, which are transmitted on the main camera cable, to be separated and made available externally. On many better video processing devices there are breakout systems. A connector outlet is provided, to which the multi-pin camera plug is attached.
Camera Supply—A single camera cable handling the following signals: video, audio, DC power supply, remote control line, tally* control and others. A camera breakout setup allows various signals, which are transmitted on the main camera cable, to be separated and made available externally. On many better video processing devices there are breakout systems. A connector outlet is provided, to which the multi-pin camera plug is attached.
Candela—Derived from the word “candle” and denoted by the symbol “cd”, the candela is the standard unit of light intensity. One candela is roughly equal to the amount of light, in any direction, from the flame of a candle. The luminance of a light source is often expressed in candelas per square meter (cd/m2).
Capacitance—The ability to store an electrical charge.
Capacitive Reactance—The opposition a capacitor offers to alternating current flow. Capacitive reactance decreases with increasing frequency or, for a given frequency; the capacitive reactance decreases with increasing capacitance. The symbol for capacitive reactance is XC.
Capacitor—A device made up of one or more pairs of conductors, separated by insulators and capable of storing an electrical charge. When there is a difference of potential between the conductors, and because current cannot flow through the insulator, an electrical charge is stored.
CAPEX—Capital Expenditure. Expenditures creating future benefits. Incurred when a business spends money either to buy fixed assets or to add to the value of an existing fixed asset with a useful life that extends beyond the taxable year.
Captive Screw Connector—A connector that uses a screw to hold a stripped wire end.
Card Readers—Card readers are learning aids that allow users to swipe magnetic vocabulary cards in a reader which translates the data into spoken audio.
Cardioid—Heart-shaped region where some microphones will be most sensitive to sound predominately from the front of the microphone diaphragm and reject sound coming from the sides and rear.
Carrier—Modulated frequency that carries video or audio signal.
CAT 5-Category 5—Describes the network cabling standard that consists of four unshielded twisted pairs of copper wire terminated by RJ-45 connectors. CAT 5 cabling supports data rates up to 100 Mbps. CAT 5 is based on the EIA/TIA 568 Commercial Building Telecommunications Wiring Standard. New installations rarely to never use it.
CAT 6-Category 6—The standard for the next higher grade of unshielded twisted pair (UTP) cabling beyond CAT 5e. The standard defines components (cable and connecting hardware) and cabling (basic link and channel) for Category 6 channels, as well as Level III field tester requirements.
CAT 7-Category—Cable standard for 10 Gigabit Ethernet using shielded twisted pair – STP) cable. Cat 7 features strict guidelines for crosstalk and system noise, requiring shielding for each pair of wires and the cable as a whole.
Cathode Ray Tube—A vacuum tube that produces light when energized by the electron beam generated inside the tube. A CRT has a heated cathode and grids in the neck of the tube, making up the "gun". Electrons are accelerated from the gun toward the front surface of the tube (screen), producing a beam. The surface on the back of the screen is coated with phosphors that light up when struck by the electron beam. The CRT in a TV is known as the picture tube, some of which have three guns - for red, green and blue colors.
CATV-Community Antenna Television System—Broadcast signals are received by a centrally located antenna and distributed by cable through a region.
CCD-Charge Coupled Devices—A light-detecting circuit array used in video cameras, scanners, and digital still cameras.
CCIR-Comite Consultatif International des Radio—Communications, the International Radio Consultative Committee. The CCIR has been superseded by the International Telecommunications Union, or ITU. Also see "ITU."
CCITT—French term for Consultative Comité of International Telephone and Telegraph, the international group that sets standards for telephony and digital communications (e.g., H.320 — the audio and video codecs and protocol for ISDN).
CCTV-Closed Circuit Television—A distribution system that limits reception of an image to those receivers that are directly connected to the origination point by coaxial cable or microwave link.
CDI-Compact Disk Interactive—A machine designed for consumer use, like audio CDs*, with special dedicated compression hardware. It allows storing and replaying a much larger quantity of data, and supports JPEG* and MPEG* standards.
CDTM/CDMT-Compressed Time Division Multiplex—A color component time compression system used byBetacam VTRs. The two-chrominance signals (R-Y and B-Y) are compressed, multiplexed and recorded at the same time as the Luminance signal.
CE-Conformité Européenne—A label or mark on a product signifying ESD, EMI, and safety compliance with all European Union (EU) directives applicable to that product. Some interpret it to mean European Community or Compliance for Europe.
CEC-Consumer Electronics Control—A bidirectional serial control bus defined in the HDMI 1.0 specification and subsequent updates. CEC is used to provide control for multiple products, connected via HDMI cables, from a single remote control. Alternately, one device, for example a Blu-ray Disc player, can turn on another device, such as a display, when put into Play mode. CEC command sets are proprietary to each manufacturer; Sony CEC commands cannot control devices from Panasonic or Sharp, and vice versa.
CEDIA-Custom Electronic Design and Installation Association—CEDIA is an international trade association of companies specializing in planning and installing electronic systems for the home. This association offers an annual expo. www.cedia.org.
CENELEC—European Committee for Electro-technical Standardization.
Center-Channel Mode—A setting on A/V receivers and A/V controllers that configures the receiver or controller for the type of center-channel speaker in the system.
Center-Channel Speaker—The speaker in a home-theater system located on top of, beneath, or behind the visual image; reproduces centerchannel information such as dialog and other sounds associated with onscreen action.
Center Tap—A connection point located halfway along the winding of a transformer or inductor.
CET-Carrier Ethernet Transport—Wide-area Ethernet services used for high-speed connectivity within a metropolitan, nationwide, or even internationally.
CGA-Color Graphics Adapter—Introduced in 1983, it was IBM’s first product to display both color and graphics. CGA has a horizontal scan frequency of 15.75 kHz and a vertical frequency of 60 Hz.
Channel Balance—The relative levels or volumes of the different channels in a home-theater system.
Channel Separation—A measure of how well sounds in one channel are isolated from other channels. Low channel separation results in sounds from one channel “leaking” into other channels, a phenomenon called “crosstalk.” A classic example is frontchannel sounds in Dolby Surround leaking into the surround channels. High channel separation results in more precise placement of sounds.
Character Generator—A machine used in video production to produce captions or titles. The character generator is similar to a PC word processor, allowing the user to change fonts, character attributes, font colors, background colors and so on.
Chassis—Also called a cabinet or frame, an enclosure that houses electronic equipment and is frequently electrically conductive (metal). The metal enclosure acts as a shield and is connected to the equipment grounding conductor of the AC power cable, if so equipped, in order to provide protection against electric shock.
Chassis Ground—A 0V (zero volt) connection point of any electrically conductive chassis or enclosure surrounding an electronic device. This connection point may or may not be extended to the earth ground.
Chip Set—Several electronic chips designed to perform a specific task together are called one chip-set. Manufacturers of VGA* cards, computer main boards, multimedia hardware and other video hardware use chip-sets to perform specific tasks which are integrated into the work of the entire board.
Chroma-(Chroma Signal)—(1) Hue and saturation are qualities of chroma. Chroma does not include black, gray, or white. The purity or intensity of color, sometimes called “hue.” Color information, independent of luma intensity or brightness. Without the chroma signal, the video picture would be black and white. (2) The NTSC or PAL video signal contains two parts that make up what you see on the screen: the black and white (luma) part, and the color (chroma) part.
Chroma Burst—See "Color burst."
Chroma Corrector—A device used to correct problems related to the chroma subsection of the video signal, including chroma saturation, hue*, color balance and color noise*.
Chroma Crawl—An artifact of encoded video also known as dot crawl or cross-luma. It occurs in the video picture around the edges of highly saturated colors as a continuous series of crawling dots (“dancing ants”) and is a result of color information being confused with luma information by the decoder circuits.
Chroma Delay—A video problem in which the color of an object or area is shifted slightly to the right of the luma (intensity).
Chroma Gain (chroma, color, saturation)—In video, the gain of an amplifier as it pertains to the intensity of colors in the active picture.
Chroma Key (Color Key)—A film and video process in which the subject is filmed in front of a blue or green background (the key color). For example, a weather reporter stands in front of a blue wall with a camera focused on him or her. The camera’s video signal feeds into a chroma keyer, which detects the blue background and replaces it with a video signal from another source, such as video of a weather map. Thus, the reporter appears to be standing in front of the weather map.
Chroma Noise—Noise which manifests itself in a video picture as colored snow*. It may be the product of one or more of the following factors: 4. Low quality videotapes. 5. Poor color decoding. Good color processors* reduce or eliminate chroma noise.
Chromatic Dispersion-CD—In fiber optics, a factor that reduces fiber bandwidth as a result of the separation of the incoming light into components of various wavelengths, which travel at different speeds along the fiber. This effect is associated with singlemode fiber at very long distances.
Chromaticity—Is an objective specification of the quality of a color regardless of its luminance, that is, as determined by its hue and colorfulness (or saturation, chroma, intensity, or excitation purity).
Chrominance—The measurement of the color value or color difference value in a pixel.
CIE-Commission Internationale de l’Eclairage (the International Commission on Illumination)—CCIR is the organization responsible for the chroma diagram of 1939, a three dimensional diagram that defines light and color. Other systems have been developed by CIE more recently.
Cladding—In fiber optics, the outer layer surrounding the core of a fiber that serves as an optical barrier as well as protection for the core. The index of refraction for the cladding is always lower than that for the core in order to maintain total internal reflection and thus ensure that the light always travels within the core.
Clamping—An electronic process, which corrects, line-by-line, the video blanking level or sync tips by clamping it to a predefined DC level. The process reduces the DC level changes when switching between different sources, eliminates picture jumps on the screen and the accumulation of low frequency noise and instability. Clamping also increases the dynamic range of video amplifiers by limiting the average picture changes, which stress the video amplifiers.
Class A—The output transistor(s) always have current flowing through them. This method of operation is pure, but inefficient. Class A amplifiers rarely exceed 20% efficiency in terms of power consumed (converted to heat) versus power delivered to the load.
Class A/B—A combination of Class A and Class B amplifier designs that corrects the inefficiency of Class A amplifier designs and allows a small amount of current to continually flow through the output transistors at all times. This alleviates most of the cross-over distortion at the expense of efficiency. An A/B amplifier is still more efficient (60 to 65%) than a Class A amplifier.
Class B—Somewhat more efficient than Class A. Class B amplifiers utilizing two drive elements operating in a push-pull configuration. On the positive excursion of the signal, the upper element supplies power to the load while the lower is turned off. During negative going signal excursions, the opposite operation occurs. This increases operating efficiency, but the exchange from ON to OFF causes a switching error condition commonly called cross-over distortion.
Class D—Also known as a switching amplifier, Class D amplifiers utilize output transistors which are either completely turned on or completely turned off (they’re operating in switch mode). Class D amplifiers operate either in the fully ON-region or fully OFF-region. Class D amplifiers reach efficiencies as high as 90%. This is of great importance to portable applications relying on battery power and for the lowest production of heat.
Cleave and Crimp—In fiber optics, the utilization of pre-polished connectors to significantly reduce termination time by eliminating the most time consuming step – polishing the connectors, so that the process requires just cleaving the fiber, insertion into the connector, and crimping.
Cleave Tool—Also known as a scribe tool, this specialized tool is used to break off a portion of an optical fiber by scoring, or scribing the fiber so that it can be cut using a cleaver to ensure a clean, precise, cut with the endface flat and at a 90-degree angle to the fiber axis.
Cleaving—The process of cutting the end of an optical fiber after it has been scored, or scribed using a cleave or scribe tool. The cut is made at a precise 90 degree angle to the fiber axis.
Client—A computer or network device that uses information supplied by a server.
Cliff Effect—The sudden or discrete loss of signal at a digital receiver due to the degradation of a transmitted signal that has been terminated due to an error rate being exceeded and the received signal being rejected.
Clipping—Cutting off the peaks (or excursions) of a signal. A form of distortion that occurs when the signal excursions exceed the limits of the circuit.
Clipping Level—An electronic limit to avoid overdriving an audio or video signal.
Clock Adjustment—Also called timing signals, used to fine tune the computer image. This function adjusts the clock frequencies that eliminate the vertical banding (lines) in the image.
Clock Rate—The rate at which analog audio is sampled and converted to a digital signal. Clock rate is important in digital audio recording and processing systems. When samples are not output at the correct time relative to other samples, a condition called “clock jitter” occurs. Clock jitter can also arise when digital audio is run through several audio products. When each product runs on its own clock, compensating for small differences between the clocks can cause output errors. For instance, even if both clocks are at exactly the same frequency, they will almost certainly not be in phase. If the clock rate of the input digital stream and the playback unit differ (44.1 KHz and 48 KHz, for instance), the playback unit has no choice but to perform a sample rate conversion. If they are the same, the playback unit may use sample rate conversion to oversample the input (for example, 88.2 or 96 kHz), then pick the samples that “line up” with its own clock.
Closed Captioning—An operation for decoding text information transmitted alongside video and audio information. The decoded text is displayed at the bottom of the screen.
CMR-Common Mode Rejection—A measure of how well a differential amplifier rejects a signal that appears simultaneously and in phase at both input terminals. As a specification, CMR is expressed as a dB ratio at a given frequency.
CMRR-Common Mode Rejection Ratio—(1) For a differential amplifier, the ratio of the differential gain to the common mode gain. (2) Expressed in dB, it is the ratio of common mode input voltage to output voltage. (3) For an operational amplifier, the ratio of the change in input offset voltage to the change in common mode voltage.
CMYK—Cyan, Magenta, Yellow, and Black. Also see "Subtractive color process."
Coarse Wavelength Division Multiplexing-CWDM—The multiplexing, or combining of several wavelengths into a single optical signal. CWDM is distinguished from Dense Wavelength Division Multiplexing – DWDM in that the separation between wavelengths – 20 nm – is much greater.
Coating—A layer of plastic covering over the fiber to provide protection from moisture as well as damage in manufacturing fiber optic cables. Also known as a buffer coating.
Coaxial Cable—A two-conductor wire in which one conductor completely wraps the other, with the two separated by insulation. Constant impedance transmission cable. Example: 75 ohm, type RG-59 cable used for video signals. Abbreviated as coax.
Coaxial Digital Output—A jack found on most DVD players that provides a digital audio signal on an RCA jack for connection to another component through a coaxial digital interconnect (which is different from the coaxial cable that carries TV signals).
Coaxial Speaker—A type of speaker design in which a high frequency driver (typically a tweeter) is placed inside a low or mid frequency driver.
CobraNet—A trademark of Peak Audio, CobraNet is network technology for the transmission of digital audio, video, and control signals over 100Mbps Ethernet networks.
Codec—(1) Coder/decoder. A device that converts analog video and audio signals into a digital format for transmission over telecommunications facilities and also converts received digital signals back into analog format. It may also dial up the connection, like a modem for teleconferencing. (2) Compressor/decompressor. Codecs can be implemented in software, hardware, or a combination of both. Some popular codecs for computer video include MPEG, QuickTime, and Video for Windows.
Collision—Two devices on a network attempt to use the physical media at the same time. The data from the two devices collides.
Color Adjustment—A video adjustment that is used to control color or chroma intensity.
Coloration—A change in sound introduced by a component in an audio system. A loudspeaker that is “colored” doesn’t accurately reproduce the signal fed to it. For example, a speaker with coloration may have too much bass and not enough treble.
Color Bars—A standard test pattern of several basic colors (white, yellow, cyan, green, magenta, red, blue, and black) as a reference for system alignment and testing. In NTSC video, the most commonly used color bars are the SMPTE standard color bars. In PAL video, the most commonly used color bars are eight full field bars. In the computer, the most commonly used color bars are two rows of reversed color bars.
Color Black—The NTSC standard for black, which is 8% gray. Computer black, the absence of all of the color primaries, is referred to as superblack and is used for matting or keying in video effects. Superblack does not render well to video. Instead of appearing black, it has a light gray appearance. Color black will appear blacker on video than superblack.
Color Burst—In color TV systems, a burst of sub-carrier frequency located on the back porch of the composite video signal. This serves as a color synchronizing signal to establish a frequency and phase reference for the chroma signal. Color burst is 3.58 MHz for NTSC and 4.43 MHz for PAL.
Color Depth—Describes the number of bits used to represent the color of a single pixel in a bitmapped image or video frame buffer. A common bit depth applied to computer graphic signals is 8-bits each for Red, Green and Blue. An 8 bit depth will produce 256 levels and 256 raised to the 3rd power, results in a resolution of over 16 million colors.
Color Difference Signals—Signals which convey color information such as hue and saturation in a composite format. Two such signals are needed. These color difference signals are R-Y and B-Y, sometimes referred to as Pr and Pb or Cr and Cb.
Color Encoder—A device that combines the separate red, green, and blue signals into one composite video signal.
Color Field—The number of a specific field in a color frame* sequence (1 to 8 in PAL, 1 to 4 in NTSC.)
Color Frame—A set of video frames which is different in each broadcast standard (PAL, NTSC, SECAM) and which is made of a certain number of sequential frames with different SCH phases until the first frame SCH or color difference signal repeats. In PAL the sequence consists of 4 frames or 8 fields, in NTSC and SECAM it is 2 frames or 4 fields. In SECAM the structure is different from PAL or NTSC.
Colorization—A process which allows painting a black/white or even a color video image with artificial colors.
Killer Color—Circuitry, which disables the color decoding* process in TV sets when a black and white transmission is received. The color killer circuitry looks for a color burst signal, and when it detects that the color burst is absent (as in black and white transmissions) color decoding circuitry is disabled. The circuitry was added to TV sets in order to improve the quality of black and white images, because the attempts of the TV to detect color information in a B&W signal result in artificial, disturbing color fringes and noise.
Color Phase—The timing relationship of the color video signal. The correct color phase will produce the correct color hues.
Color Processing—A way to alter the colors of a video signal. At the first stage, the video signal is separated into its black/white and color constituents. Further separation usually strips down the color information to its basic components, red, green and blue. After color correction, the signals are recombined into a normal video signal by the processor with improved or changed colors.
Color Quantization—Color quantization defines the resolution, or number of colors used in a system. This is this is important for displaying images that support a limited number of colors and for efficiently compressing certain kinds of images. For example, reducing the number of colors required to represent a digital image makes it possible to reduce its file size or streaming bit rate.
Color Resolution—The number of colors available at one time in an image, measured in terms of bits per pixel.
Color Space—A system for describing color numerically. There are several color space definitions, each used to support the specific identity of colors within a structured identification system. In AV presentation, there are two primary video color space definitions: RGB, which describes the three color primaries, Red, Green, and Blue; and Component or YUV, which describes the luminance channel (Y) and two chrominance channels, U (Blue minus Y) and V (Red minus Y), with the remainder representing Green. RGB is most commonly used with high-resolution computer video signals, while YUV is the primary color space for motion video and television transmission. While the earlier DVI standard supports only RGB, the newer HDMI, and DisplayPort standards support both RGB and YUV color space, and color space conversion is common in sources such as Blu-ray Disc players and both flat panel and projection display devices.
Color space and color space conversion pose a unique challenge when switching between signals with different color spaces, for example, switching a source in YUV color space to a display device set up to receive signals in RGB color space. Many digital displays will automatically detect the change in color space, but may require several seconds or more to lock to the new signal and display it properly. Some displays, on the other hand, require manual intervention to select the new color space through an on-screen display menu.
Color Subcarrier—The carrier signal or frequency on which the color signals are modulated. The most commonly used color subcarrier frequency is 3.58 MHz for NTSC, and 4.43 MHz for PAL.
Color Temperature—The color quality, expressed in degrees Kelvin (K), of a light source. The higher the color temperature, the bluer the light. The lower the temperature, the redder the light. Benchmark color temperatures for the A/V industry include 5000° K (a comparatively “warm” or reddish color temperature, favored for pleasing video reproduction); 6500° K (D65, the reference color for accurate color reproduction); and 9000° K (a comparatively “cold” or bluish color temperature, favored for graphics and other high-contrast image reproduction).
Color Uniformity—The ability of a projection screen to reflect all colors equally at every point on the screen. A screen with poor color uniformity may impart a blue tint to the image on one side of the screen, and a red tint on the other side.
Color Wheel—In DLP-based video displays, a device that sequentially passes red, green, and blue light to the DMD chip by means of a spinning wheel with red, green, and blue filter wedges.
Comb Filter—A filter circuit that passes a series of frequencies and rejects the frequencies in between, producing a frequency response that resembles the teeth of a comb. This is an improvement over the notch filter. Its precise separation of the chroma and luma reduces both cross chroma and cross luma artifacts (chroma crawl or zipper artifacts). It preserves more detail in black and white, resulting in a better quality picture. Although comb filters are successful in reducing artifacts, they may also cause a certain amount of loss of resolution in the picture.
Combing—An undesirable blurring of an image that contains motion. This effect occurs when a single frame of video combines two fields of video derived from different frames of film.
Communication Bandwidths—Below are listed commonly available bandwidths for network switching equipment and connections made available for public and private networks.
All communication bandwidths presented below are listed in Megabits/s (Mb/s). 1,000 Mb/s equals 1 Gigabit/s (Gb/s).
Half-Duplex LAN Switched Fabric (See Note)
Cisco Catalyst 3750
Raptor Networks RAST
Cisco Catalyst 6509
LAN Local Connections
Ethernet (10 BaseT)
Fast Ethernet (100 BaseT)
Gigabit Ethernet (1000BaseT)
10 Gigabit Ethernet
WAN and MAN
Broadband Satellite internet
Microwave 4 DS1
Please Note: Full-duplex switched fabric capacity is typically specified by manufacturers. Half-duplex capacity is typically more relevant to multicast video applications as it identifies the one-way sustained throughput directionally. Switched network architecture and intelligent switching features, including hardware or software routing, multicast routing protocol support, latency and other factors can be far more critical to consider than switched fabric capacity when designing switched networks.
Communication Protocol—Software based protocol or language, linking several devices to enable them to communicate one with one another. Communication protocols are used between computers DVRs and VCRs or editing controllers allowing bi-directional conversation between the units. The linked units use specific hardware connections in addition to the software and protocol. See also RS-232/RS-422*.
Common-Mode—Refers to either noise or surge voltage disturbances occurring between the power neutral (white wire) and the grounding conductor (green wire). Unwanted common mode disturbances exist as a result of noise injection into the neutral or grounding wires, wiring faults, or overloaded power circuits.
Common-Mode Rejection Ratio (CMRR)—The ratio of the common-mode interference voltage at the input of a circuit, to the corresponding interference voltage at the output.
Compander—A device that combines compression and expansion.
Component Digital—Digital video using separate color components, such as Y, Cb, Cr. Digital recording formats such as D1 (Sony, BTS/Philips) and D5 (Panasonic) utilize component digital recording technology. Component digital is the digital representation of the component analog signal set, Y, B-Y, R-Y; it is often represented as 4:2:2. The encoding parameters are specified by ITU-R BT.601-2 (formerly known as CCIR 601).
Component Video—Color television systems start with three channels of information: red, green, and blue (RGB). In the process of translating these channels to a single composite video signal, they are often first converted to Y, R-Y, and B-Y. Both three-channel systems, RGB and Y, R-Y, B-Y, are component video signals. They are the components that eventually make up the composite video signal. Higher quality program production is possible if the elements are assembled in the component domain.
Component-Video Switching—A feature on A/V controllers and receivers that allows you to connect several component-video sources to the controller or receiver, with the controller or receiver sending the selected signal to the video display.
Composite Digital—Digital video that is essentially the digitized waveform of NTSC or PAL video signals, with specific digital values assigned to the sync, blank, and white levels. Commonly described as “4fsc”, a sampling rate locked to four times the frequency of color subcarrier. Early digital tape formats, such as D2 (Sony) and D3 (Panasonic), used a composite digital recording scheme. Also refers to digitally encoded video signal, such as NTSC or PAL video, that includes horizontal and vertical synchronizing information.
Composite Sync—A signal combining horizontal and vertical sync pulses and equalizing pulses with no picture information and no signal reference level. Composite sync is sometimes referred to as “C”, “S” (as in RGBS), or “HV” (as on some connector panels).
Composite Video—An all-in-one video signal comprised of the luma (black and white), chroma (color), blanking pulses, sync pulses, and color burst.
Compression—The art and science of reducing the amount of data required to represent a picture or a stream of pictures and sound before sending or storing it. Compression systems are designed to eliminate redundant or repeated information to the desired data level while allowing the original information to be reproduced to the desired quality.
Compression (Audio)—Compression is commonly used to keep mic levels within an acceptable range for maximum intelligibility. Though a compressor effectively makes louder portions of a signal softer, it is used to make softer sounds louder. This is achieved by reducing the dynamic range, then raising the output level of the compressor (referred to as "make-up gain"), or by increasing the input signal, then preventing clipping by reducing the louder portions of the signal. Compression is also used to protect a system or a signal chain from overload.
Compression Artifacts—Compacting of a digital signal, particularly when a high compression ratio is used, may result in small errors when the signal is decompressed. These errors are known as artifacts, or unwanted defects. The artifacts may resemble noise (or edge busyness) or may cause parts of the picture, particularly fast moving portions, to be displayed as distorted or incomplete.
Compression Connector—A special connector, such as a BNC, RCA, or F-Connector, that is quickly and securely attached to a cable by using a compression tool. The connector is compressed onto the cable. Also see "Compression tool."
Compression Tool—A special cable tool that is used to quickly and securely attach a connector, such as a BNC, RCA, or F-Connector, by compressing the connector to the cable. Also see "Compression connector."
Compressor—A compressor regulates the level of an input signal by reducing or compressing its dynamic range above a user-defined threshold. Also see "Compression (Audio)."
Computer-Video Interface—A device that converts the nonstandard video output of computer systems to a standard RGB analog signal, which can then be connected to a compatible data monitor and projector.
Condenser Microphones—Also called a capacitor microphone, it transduces sound into electricity using electrostatic principles.
Conductor—In electronics, a material that easily conducts an electric current because some electrons in the material are free to move.
Cone—Most commonly used component in a loudspeaker system and found in all ranges of drivers.
Cone Diaphragm—The conically shaped paper, plastic, or metal diaphragm of a loudspeaker that moves back and forth to create sound. Contrast with “dome diaphragm.”
Conferencing Systems—The technology by which people separated by distance come together to share information. Conferencing systems may include projection, monitor displays, computers, satellite connections video and audio playback devices, and much more.
Congestion—Occurs when a link or node is carrying so much data that its quality of service deteriorates. Typical effects include queueing delay, packet loss or the blocking of new connections. A consequence of this is that increases in offered load lead to only small increases in network throughput, or to an actual reduction in network throughput.
Constant Bit Rate (CBR)—Constant bit rate encoding means that the rate at which a codec’s output data should be consumed is constant. CBR is useful for streaming multimedia content on data communication channels which operate more efficiently or require the bit rate to remain within a tight tolerance. Typically the constant bit rate is created by stuffing bits into a variable bitrate signal which has a defined peak or maximum limit.
Constant Quality—The quality output from a process, such as video encoding remains constant, while the output, such as a bit rate may vary. Constant quality encoding will result in a variable bit rate if the nature of the video material changes.
Constant Voltage System—The common name given to the interface between amplifiers and speakers in a distributed audio system. Several voltages are used, but the most common are 70.7 V (commonly shortened to 70 V) in the US, and 100 V in Europe. “Constant voltage” refers to the characteristic that whether the total output of the amplifier is 5 watts or 50 watts or 500 watts, the maximum output voltage is always a constant of 70.7 V. The voltage stays the same regardless of the load, so the output current varies but not the voltage.
Contact Closure—The momentary connection of two conductors to complete an electrical circuit. Often used to switch inputs on switchers.
Contention—The media that network devices use to deliver data is overused and “contention” for the media is experienced.
Continuity—In digital picture manipulators, the characteristic of location/positioning that determines if the motion path continues smoothly.
Continuous Power—The continuous power specification can be used to describe the output of an amplifier and is typically stated at “x watts (rms) into y ohms from 20 Hz to 20K Hz at z% THD (total harmonic distortion)”. For example, the Extron MPA 122 amplifier is specified as 11 watts (rms) per channel into 4 ohms at 1% THD.
Continuous Presence—A feature in some videoconferencing equipment that allows the participants to view multiple sites on the same video screen. This is a function of the codec used and not of the video switching system.
Contouring—Digital video picture defect caused by quantizing at too coarse a level.
Contrast—The range of light and dark values in a picture, or the ratio between the maximum and the minimum brightness values. Low contrast is shown mainly as shades of gray, while high contrast is shown as blacks and whites with very little gray. It is also the name of a TV monitor adjustment, which increases or decreases the level of contrast of a displayed picture. Also called “white level.”
Contrast Range—The range of grays in a video image.
Contrast Ratio—The ratio of the high light output level divided by the low light output level. In theory, the contrast ratio of the television system should be at least 100:1, if not 300:1. In reality, there are several limitations. In the CRT, light from adjacent elements contaminates the area of each element. Room ambient light will contaminate the light emitted from the CRT. Well-controlled viewing conditions should yield a practical contrast ratio of 30:1 to 50:1.
Contrast Mixing—A way of mixing two video images using a special effects generator* or video mixer. While maintaining a fully contrasted image, this process does not allow the mixed image to exceed the maximum permitted amplitude (which would cause degradation in picture quality). Using a quality video mixer, contrast is consistently maintained without the introduction of distortion.
Control Track—The portion along a length of a recorded tape on which sync control information is placed; used to control the recording and playback of the signal.
Controller—Another term for an A/V preamplifier.
Convergence—The alignment of the red, green, and blue video projected onto a screen when the lines produced by the three color sources appear to form one clearly focused white line. The point at which the light from each of the three lenses aligns so the perceived single image is clearly focused. Lack of convergence is a video problem when the displayed image appears to be outlined by red, green, or blue because of misaligned colors.
COP-3—A Code of Practices established by the MPEG Forum for the transmission of MPEG-2 transport streams which applies a technique known as Forward Error Correction to protect the enclosed data.
COP-4—A Code of Practices for the transmission of uncompressed standard video at up to 270 Mbps and High Definition video at up to 1.485 Gbps which applies a technique known as Forward Error Correction to protect the enclosed data.
Core—The central core of an optical fiber in which the light travels. The core’s index of refraction is always greater than that of the cladding which surrounds it, to maintain total internal reflection and therefore keep the light within the core.
CoS-Class of Service—Method of classifying traffic on a packet-by-packet basis using information in the type-of-service (ToS) byte to provide different service levels to different traffic. See also QoS.
Coupling Loss—The loss of optical power as light passes through a junction, expressed as the ratio of the optical power measured at the junction, such as a coupler, to the total optical power entering the system.
CP3—A Crestron, compact, rack-mountable 3-Series® control processor with immense power and numerous integrated control ports.
CPU-Central Processing Unit—The portion of a computer system that reads and executes commands.
CRC-Cyclic Redundancy Check—CRC or polynomial code checksum is a method used to detect changes or errors in raw data, and is commonly used in digital networks, data communications and storage devices.
Crest Factor—The ratio of peak value of a signal divided by the rms value of the signal. The crest factor of the audio program determines the required headroom needed in the audio system.
Crestron—Crestron is a global technology company headquartered in Rockleigh, New Jersey, that manufactures control and automation systems. Crestron solutions integrate unified communications, AV presentation, lighting, environmental and HVAC systems. Crestron provides technology services for corporate conference rooms, hotels, classrooms, auditoriums, and homes.
Critical Angle—An important angle of incidence for light as it meets a boundary between two refractive materials. Below this angle, total internal reflection occurs. In an optical fiber, light always strikes off the boundary between the core and cladding below the critical angle so that it is internally reflected within the core as it travels along the fiber.
Cross Color—Moiré or rainbow artifacts in an encoded video picture caused when the video encoder or decoder misinterprets luma detail as color information, resulting in color being displayed where it shouldn’t be. It is especially noticeable when the subject wears pinstriped clothing.
Cross Fading—A term used in video and audio editing* to describe a procedure whereby one signal is gradually faded out while a second signal is faded in until it fully replaces the first signal.
Cross Luma—Dot crawl, chroma crawl. A video artifact that occurs when a composite video decoder incorrectly interprets chroma information (color) to be high-frequency luma information (brightness). This may appear as tiny, colored dots that creep along the edges of objects.
Cross Planes—A digital video effect showing several images that appear to be riding on different planes. The planes may be parallel to each other, intersecting, perpendicular or in any other geometric form and relationship.
Crosshatch—A test pattern consisting of vertical and horizontal lines used for converging a color display device.
Crossover—A circuit that splits up the frequency spectrum into two or more parts. Crossovers are found in virtually all loudspeakers, and in some A/V receivers and controllers.
Crossover Distortion—A type of distortion that occurs in push-pull class AB or class B amplifiers. It happens during the time that one side of the output stage shuts off, and the other turns on.
Crossover Frequency—The frequency at which the audio spectrum is split. A subwoofer with a crossover frequency of 80Hz filters all information above 80Hz from the signal driving the subwoofer, and all information below 80Hz from the signal driving the main speakers. Also called “cutoff frequency.”
Crossover Network—An electrical circuit that combines high pass, low pass, and bandpass filters to divide the audio frequency spectrum, 20 to 20,000 Hz, into ranges suitable for low frequencies (woofer), mid-range, and high frequencies (tweeters).
Crossover Slope—Describes the steepness of a crossover filter. Expressed as “dB/octave.” For example, a subwoofer with a crossover frequency of 80Hz and a slope of 6dB/octave would allow audio frequencies at 160Hz (an octave above 80Hz) into the subwoofer, but signals at 160Hz would be reduced in amplitude by 6dB. A slope of 12dB/octave would also allow 160Hz into the subwoofer, but the amplitude would be reduced by 12dB. The most common crossover slopes are 12dB/octave, 18dB/octave, and 24dB/octave. Crossover slopes are also referred to as “first-order” (6dB/octave), “second-order” (12dB/octave), “thirdorder” (18dB/octave), and “fourthorder” (24dB/octave). The “steeper” slopes (such as 24dB/octave) split the frequency spectrum more sharply and produce less overlap between the two frequency bands, but they also cause phase anomalies.
Crosspoint—An electronic switch, usually part of an array of switches that allows video or audio to pass when the switch is closed.
Crosstalk—Caused by interference between two signals, usually from an adjacent channel, which adds an undesired signal to the desired signal. Crosstalk is caused by magnetic induction or capacitive coupling, and can occur when there is a grounding problem or improper cable shielding. Video symptoms include noise and ghosting, while audio symptoms include signal leakage.
CRT-Cathode Ray Tube—A vacuum tube that produces light when energized by the electron beam generated inside the tube. A CRT has a heated cathode and grids in the neck of the tube, making up the gun. Electrons are accelerated from the gun toward the front surface of the tube (screen), producing a beam. The surface on the back of the screen is coated with phosphors that light up when struck by the electron beam. The CRT in a TV is known as the picture tube. Some CRTs have three guns—for red, green, and blue colors.
CSMA/CD-Carrier Sense Multiple Access/Collision Detection—The Media Access Control method applied in Ethernet networks. When a device wants to gain access to the network, it checks to see if the network is quiet (senses the carrier). If it is not, it waits a random amount of time before retrying. If the network is quiet and two devices access the line at exactly the same time, their signals collide. When the collision is detected, they both back off and each waits a random amount of time before retrying.
CSP—Crestron Services Provider. Independent programmers who are certified by Crestron through intensive training and real-world experience.
CTS-Certified Technology Specialist—An A/V and video professional who, through practical experience and extensive industry training programs offered by ICIA, has developed a high level of expertise.
Cubby—A cubby is slang for a table mounted unit that transmits AV signals to presentation systems, and often supplies power, usb and ethernet connectivity for devices.
Cue Systems—Cue systems help the speaker communicate with the projectionist and vice versa during a presentation, but with today's presentation systems, the presenter can often control the projector & slides remotely.
Curing Oven—A specialized oven used to thermally cure epoxy for adhering a fiber optic connector ferrule onto the optical fiber.
Current—The flow of electricity, and the rate at which it flows. Also see "Amp."
Curvature of Field—A blurry appearance around the edge of an otherwise in-focus object (or the reverse) when the velocity of light going through the lens is different at the edges than at the center of the surface, due to the lens design
Cut—An instantaneous transition between two sources. An instantaneous scene change.