Home Theater

10BaseT - Standard developed by Institute of Electrical Engineers ( IEEE ) refering to 24-AWG unshielded twisted pair wiring with a baseband medium of 10 Mbps, and defines various aspects of running Ethernet on this cabling.
10Base2 - IEEE standard for thin coax with maximum length of 656 ft, having a baseband medium of 10 Mbps
100BaseT - Standard developed by Institute of Electrical Engineers ( IEEE ) refering to 24-AWG unshielded twisted pair wiring with a baseband medium of 100 Mbps, and defines various aspects of running Ethernet on this cabling.
1000BaseT - Standard developed by Institute of Electrical Engineers ( IEEE ) refering to 24-AWG unshielded twisted pair wiring with a baseband medium of 1000 Mbps, and defines various aspects of running Ethernet on this cabling.
3-2 pulldown processing - Sophisticated video processing common to digital TVs and progressive-scan DVD players. It corrects for artifacts and distortion that occur when film-based material (at 24 frames per second) is converted to video (30 frames per second), then de-interlaced to create a progressive-scan signal.
5.1, 6.1, and 7.1-channel inputs - A receiver's 5.1-channel input features preamp-level jacks for 6 channels: left main, right main, center channel, left surround, right surround, and subwoofer (sometimes called "LFE" or "Low-Frequency Effects"). Because the LFE channel carries a limited range of very low frequencies, it's the ".1" in 5.1. A 5.1-channel input allows you to hook up a separate multichannel surround sound (DolbyÂ® Digital, DTSÂ®) decoder, such as those built into some DVD players. You can also use these inputs with up-and-coming multichannel music sources like DVD-Audio and SACD players. Some receivers feature a 6.1 or 7.1-channel input. These let you hook up any of the 5.1 sources described above, but also pave the way for future upgradability. One potential use for these inputs is hooking up decoders for surround formats that offer 6.1 channels, such as Dolbyâ„¢ Digital EX, DTS-ESâ„¢ and THX Surround EXâ„¢.
5.1-channel surround sound - A setup with six discrete digital audio channels: five full-bandwidth and one "low frequency" channel. The full-bandwidth channels account for the front left and right speakers, the center speaker, and the back left and right surrounds, while a subwoofer takes care of the low-frequency effects. This set-up is used in home living rooms, media rooms, game rooms and smaller sized dedicated home theaters.
6.1-channel surround sound - A setup with seven discrete digital audio channels: six full-bandwidth and one "low frequency" channel. The full-bandwidth channels account for the front left and right speakers, the center speaker, surround left and right speakers and the back center surround, while a subwoofer takes care of the low-frequency effects. This set-up is used in home living rooms, media rooms, game rooms and small to medium sized dedicated home theaters.
7.1-channel surround sound - A setup with eight discrete digital audio channels: seven full-bandwidth and one "low frequency" channel. The full-bandwidth channels account for the front left and right speakers, the center speaker, surround left and right speakers and the back left and right surrounds, while a subwoofer takes care of the low-frequency effects. This set-up is used in home living rooms, media rooms, game rooms and medium to large sized dedicated home theaters.
7.2-channel surround sound - A setup with nine discrete digital audio channels: seven full-bandwidth and two "low frequency" channel. The full-bandwidth channels account for the front left and right speakers, the center speaker, surround left and right speakers and the back left and right surrounds, while two subwoofers takes care of the low-frequency effects. This set-up is used in home living rooms, media rooms, game rooms and large sized dedicated home theaters.
9.1-channel surround sound - A setup with ten discrete digital audio channels: nine full-bandwidth and one "low frequency" channel. The full-bandwidth channels account for the front left and right speakers, the center speaker, surround left and right speakers, back surround left and right speakers and the back left and right presence speakers, while a subwoofer takes care of the low-frequency effects. This set-up is used in home media rooms, game rooms and large sized dedicated home theaters.
10.2-channel surround sound - A setup with twelve discrete digital audio channels: ten full-bandwidth and two "low frequency" channel. The full-bandwidth channels account for the front left and right speakers, the center speaker, left high and right high, left wide and right wide, surround left and right and surround back center, while two subwoofer left and right between wide channels and surrounds takes care of the low-frequency effects. This set-up could be used in large sized dedicated home theaters.
22.2-channel surround sound - A setup with twenty four discrete digital audio channels: twenty two full-bandwidth and two "low frequency" channel. Not enough information to complete.
A / D converter - Analog to digital converter - A device that converts an analog value to a digital value.
A / V - Industry term for audio/visual, or audio/video.
A / V inputs (TV) - Using a TV's direct A/V inputs to connect a DVD player, VCR, DVR, game console or other video component provides improved picture rather than routing through another component however many new surround sound processors using HDMI version 1.3 provide up conversion for connectivity of components of lower quality connections to be connected to your televisions A / V inputs using the single HDMI cable and allowing for sound to be played through the surround sound processor with the TV audio muted and keep the option of muting the surround sound processor to have the audio to the television play. Antiquated methods of connectivity had each component connected to the television and surround sound processor and often the quality of audio and video were compromised and older connections utilized RF connections where everything was -on-one-wire RF antenna-style input. (If your TV is old enough that it only has RF-type inputs, that's reason enough to consider replacing it - Many components don't normally have an RF output!) Rear A/V inputs are used for components you normally leave connected to your TV. Front A/V inputs allow you to quickly and easily connect/disconnect a camcorder or video game console.
A / V inputs / outputs (Receivers) - An A/V input consists of many older connectivity types of audio video jacks such as Composite, utilizing three RCA jacks - two for the stereo audio signal, and one for the video signal. Then there is the S-Video video composite video signal separated into the luma ("Y" is for luma, or black and white information; brightness) and the chroma ("C" is an abbreviation for chroma, or color information). Using a 4-pin connector, an S-video jack transmits the chrominance (color) and luminance (brightness) portions of a video signal separately, for improved color accuracy and reduced distortion. Receivers with S-video inputs and outputs offer convenient remote switching for your high-quality video sources. A type of video connection that carries the chrominance (color) and luminance (brightness) portions of the video signal in separate streams, for improved color accuracy and reduced distortion. S-video provides a sharper picture than composite video, but not as good as what is next on the list of connections available. Component Video which is a signal that has been split up into its component parts where the brightness (luminance) and color (chrominance) portions of the signal are processed separately.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 3-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.The three-jack component video connection splits the video signal into three parts (one brightness and two color signals) for a more accurate picture with less color bleeding. This type of connection is capable of carrying wider bandwidth video signals, like progressive scan and high-definition video.Component video signals provide greater color accuracy than S-video or composite signals.Nearly all new DVD players and many new TVs include 3-jack component video connections. Why is component video superior to S-video? Where S-video separates the luminance and chrominance portions of the signal, component video goes a step further and splits the chrominance portion into two components. The benefits - improved color accuracy and less color bleeding - are especially noticeable on larger-screen TVs. These types of connections are for older analog based signals. DVI and HDMI are some of the available digital signal passing connections and cabling available for integrating components to one another in your audio visual system. Receivers offer convenient remote switching for your A/V sources.
AAC (Advanced Audio Coding) - An up-and-coming compression format for digital audio. In terms of sound quality and data efficiency, AAC solidly beats the still-popular MP3 format - not surprising, since AAC is a newer, more advanced form of compression. According to some listening tests, AAC files encoded at lower bitrates (like 96 Kbps) sound as good or better than MP3s encoded at higher bitrates (like 128 Kbps) despite their notably smaller size. The current version of the AAC codec was developed as part of the MPEG4 standard. AAC is the audio file format used by Apple in their popular iTunes Music Store.
AC-3 - The first descriptor for what is now called Dolby Digital.
AC - Alternating current. Electron flow that changes direction alternately.
AC coupled - When a circuit does not pass DC component of signal, and it ignores DC offsets.
AC Line Conditioner or Protector - A device inserted between the wall outlet and your equipment to isolate it from voltage spikes and unwanted high frequency signals that may be picked up by the power lines. High quality audio equipment may already have some of this kind of isolation built in. See also: AC Voltage Stabilizer
AC Voltage Stabilizer - A device inserted between the wall outlet and your equipment to maintain a constant voltage level. Used in buildings and neighborhoods where line voltage fluctuates widely because of heavy variable loads.
Acoustics - The physical science dealing with how sound is produced, propagated, manipulated and perceived. See also: Room Acoustics
Acoustic suspension - A type of speaker enclosure that uses a sealed box to provide tight, accurate bass response. It gives up some efficiency to provide bass that is more accurate and controlled, so compared to a bass reflex design, it may require more amplifier power to play at the same volume level. See also bass reflex.
Acoustical Interference - When two or more sounds arriving from different directions combine at a point in space, e.g. at an ear or microphone, those components which are in step with each other (in phase) will add (constructive interference) and those that are out-of-phase will subtract, or cancel each other (destructive interference). See: In Phase, Out-of-Phase, Comb Filter.
Achromatic - Completely colorless white light.
Active Crossover - An analog or digital device performing high-pass, low-pass and bandpass functions ahead of power amplifiers driving the transducers in a loudspeaker.
Active Loudspeaker - A loudspeaker which has a built-in power amplifier for at least one driver, usually the woofer or subwoofer. It may also have amplifiers for mid and high frequency drivers. See: Powered Tower
Active Matrix Decoder - See: Matrix Encode/Decode
ADA - Analog Distribution Amplifier.A device that takes in one signal and distributes it to several outputs without "tying" those outputs together (buffered).
Adapter - Device enabling different types or sizes of plugs to mate.
ADC - Analog-to-digital converter.A device used to convert 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 (CMYK)
ADSPâ„¢ - Advanced Digital Sync Processingâ„¢. 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.
ADTV - Advanced Definition Television. An early version of high definition television (HDTV) devised in Japan. Now superseded by US HDTV standards.
AES/EBU - The two-channel digital audio communication process that was standardized by the Audio Engineering Society (AES) and the European Broadcasting Union (EBU).
AFLâ„¢ - Accu-RATE Frame Lockâ„¢. A 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.
AGC - Automatic Gain Control. In audio recording, a circuit used to automatically control the volume of the recorded signal without distortion due to overload. It is sometimes called Automatic Level Control (ALC), or Automatic Volume Control (AVC).
AIFF (Audio Interchange File Format) - An audio format for Macintosh operating systems commonly used for storing uncompressed, CD-quality sound (similar to WAV files for Windows-based PCs).
Aliasing - Aliasing occurs when smooth curves and lines become rough or jagged because of a lower resolution device, or by an event. 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 moirÃ© or herringbone pattern, straight lines that become wavy, or rainbow colors. (Also see cross color.) 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. See anti aliasing.
ALiS - ALiS (Alternate Lighting of Surfaces) is a relatively new type of high-definition plasma panel design. On a conventional plasma TV, all pixels are illuminated at all times. With an ALiS plasma panel, alternate rows of pixels are illuminated so that half the panel's pixels are illuminated at any moment (somewhat similar to interlaced-scanning on a CRT-type TV). ALiS panels offer bright, clear picture quality, reduced power consumption, and extended panel life.
AM (radio) Amplitude Modulation - A method of radio transmission, by which the information part of the signal causes the amplitude to vary without affecting the frequency.
Ambience - In audio this refers to the reflected and reverberant sound characteristics of an acoustic space. All rooms can be acoustically 'live' or 'dead'. Large rooms can be flattering to musical performances (concert hall) or hostile (gymnasium).
American Standard Code for Information Interchange - It is the standard code consisting of 7-bit coded characters (8 bits including parity check), utilized to exchange information between data processing systems, data communication systems, and associated equipment. The ASCII set contains control characters and graphic characters.
American National Standards Institute - ANSI - The American National Standards Institute is the organization that sets standards for US A/V equipment.
American Wire Gauge (AWG) - Standard gauge for measuring diameter of copper, aluminum and other conductors.
Ammeter - A device used to measure current flow in amperes.
Amorphous - 1-No definite form or shape; not crystallized.2-Early type of LCD panel technology before polysilicon.
Amp - Ampere - The international base unit of current that represents the rate flow of electric charges through a conductor. Symbolized by "A". One amp is equal to the steady current produced by 1 volt applied across a resistance of 1 ohm.
Amperage - The magnitude of an electrical current as expressed in amperes.
Ampere-hour - A measure of the quantity of electricity delivered by a battery determined by multiplying the integrated current in amperes by the duration of the current flow in hours.
Ampere-hour capacity - Rating for a battery describing current in amperes that can be drawn over a period of time in hours before the discharge limit is exceeded.
Amplification - An increase in signal level.
Amplifier - Device used to increase the strength of a signal. An electronic device that takes in an original signal, gives it more power and provides it as an output.
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 - A method of radio broadcasting in which the radio carrier frequency is amplitude modulated by the audio signal. Typically limited in bandwidth, and susceptible to interference and static. However, it propagates well over long distances and around hills and buildings. Abbreviated AM.
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. (Not like digital, where changes are by steps.)
Analog control - Method using continuously varying voltage levels to provide control of equipment.
Analog recording - Method of recording and encoding information by use of a continuously varying signal, rather than by discrete (digital) pulses.
Analog-to-digital converter - See A/D converter.
Anamorphic - A type of lens or adapter designed to produce a wide-screen image from a condensed image on the film. Trademarks are held by CinemaScope, Panavision and Vistavision.
Anamorphic DVD - A DVD that has a widescreen video image that has been horizontally squeezed. This allows a full widescreen image to be displayed on a 16x9 screen.
Anamorphic video - Video images that have been "squeezed" to fit a video frame when stored on DVD. These images must be expanded (un-squeezed) by the display device. An increasing number of TVs employ either a screen with 16:9 aspect ratio, or some type of "enhanced-for-widescreen" viewing mode, so that anamorphic and other widescreen material can be viewed in its proper proportions. When anamorphic video is displayed on a typical TV with 4:3 screen size, the images will appear unnaturally tall and narrow.
Anechoic - Without echoes, reflections or reverberation.
Anechoic Chamber - A room without echoes or reflections that is used for precise acoustical measurements, not contaminated by normal room acoustical factors, including noise. It is the ultimate 'dead' room. See Reverberation.
Anode - The electrically positive terminal of a battery, or the plate of a vacuum tube.
Anti aliasing - In computer graphics, anti aliasing is a technique for smoothing jagged edges by blending shades of color, or gray along the edges. Some video devices, such as character generators, have an anti aliasing feature to minimize aliasing through filtering and other techniques.
Aperture - The opening, usually an adjustable iris, which 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 screen-like feature of Sony Trinitron monitors and others licensed by Sony which controls the number of electrons hitting the phosphor coating on the screen.
Aperture Ratio - In digital display devices, this is a measure indicating the percentage of the available area that is used for active pixels. Some displays have obvious inactive 'frames' around individual pixels, leading to the description 'screen-door' effect when viewing such a display from insufficient distance.
Aquaplas - A water based compound high in particulates which is used to adjust the mass of, and to add damping to, a variety of loudspeaker diaphragm materials.
Articulation / Articulation Index - Having to do with the intelligibility of speech. This is measured using listeners who try to identify randomly presented 'nonsense' words and phrases. The Articulation Index is the percentage of correct identifications. Used mainly in large venues.
Artifacts - Artifacts are visible corruption of the image or undesirable elements or defects in a video picture created by disturbances in the video transmission or processing. These may occur naturally in the video process but must be eliminated to produce a high quality picture. The most common reasons for video artifacts are cross color and cross luma. Examples include "dot crawl" or "hanging dots" in analog pictures, or "pixelation" in digital pictures.
Artificial Reverberation - Synthesized reflected sounds intended to add to a recording the acoustical impression of being in a specific size and kind of room, such as a concert hall, stadium, club, etc. Inexpensive versions tend to be very artificial sounding. The best versions are hardly distinguishable from the real thing, and in fact are used in numerous concert performing spaces to improve on less-than-perfect natural acoustics. Also, the electronic reverberation added to close-miked recordings.
Aspect ratio - The ratio of width to height for an image or screen. The North American NTSC television standard uses the squarish 4:3 (1.33:1) ratio. More and more direct-view and projection TVs (especially digital TVs) use the wider 16:9 ratio (1.78:1) to better display widescreen material like anamorphic DVDs and HDTV broadcasts.
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. Also see LSTA.
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.
ATRAC - Developed by Sony engineers in the early 90's, ATRAC is an audio codec which offers near-CD sound quality. The MiniDisc format uses ATRAC to fit a whole CD's worth of music on a 2-1/2" disc. ATRAC3 is a newer version of this codec that squeezes music into even smaller files. It's used for MDLP recording with some MiniDisc recorders, for music storage in some portable memory players, and in other Internet music applications like Liquid Audio and RealAudio. A MiniDisc recorder with MDLP gives you a range of compression options (in order of increasing compression): * regular recording mode - standard ATRAC codec (292 Kbps encoding bitrate), * LP2 mode - ATRAC3 codec (132 Kbps encoding bitrate), * LP4 mode - ATRAC3 codec (66 Kbps encoding bitrate)
ATSC - Advanced Television Standards Committee. Formed to establish technical standards for the U.S. digital television system,including digital high definition television (HDTV).
Attack - In music, the onset of a sound or note.
Attenuate/Attenuation - Reduction in power or strength (amplitude) of a transmitted signal as the signal travels along the cable. Attenuation is caused by capacitance, inductance and resistice losses in the cable. Attenuation is a function of frequency. Genrally, the greater the frequency, the more attenuation. Attenuation is also a function of distance. The greater the distance, the more attenuation. Attenuation is expressed as decibels/unit length and expresses a power loss per distance traveled. Also, frequency must be stated otherwise the data is useless. For example, attenuation specs stated as 6.5 db/1000m@10MHz means that the signal has lost 6.5 decibels of power over the 1000 meters of cable it traveled at a frequency of 10MHz. Attenuation is always present on a cable, as i capacitance. To improve error rates and achieve the reliable data transmission, the communications cable should have the lowest practical combination of the two.
AU - An audio format commonly used for posting sound clips on the Internet. AU files can be played back on Windows, Macintosh, and other operating systems.
Audio inputs / outputs (Receivers) - See A / V inputs / outputs (Receivers)
Audio follow - Term used when audio is tied to other signals, such as video, and they are switched together. The opposite of breakaway.
Audio Frequency Range - The range of human hearing commonly accepted as 20 to 20,000 Hertz (cycles per second).
Audio Interconnect Cable - A shielded wire used to link the audio signal output of one device to the input of another audio device.
Audiometer - A device for testing various aspects of hearing performance, beginning with the hearing threshold, the smallest sound that one can hear at various standardized frequencies.
Audio Oscillator - A test instrument that produces single frequency tones for measuring the performance of audio devices.
Audio outputs (TV) - Stereo audio jacks that let you connect your TV to your stereo or home theater system. There are two types - fixed, and variable. If you connect a TV's fixed output to your A/V receiver, you'll be able to raise and lower the TV volume via the receiver's volume control. If you connect the TV's variable output to your receiver, you would control TV volume using the TV's remote. Some outputs are amplified that allow you to connect directly to your speakers. There are also other televisions that have varying connections for surround sound outputs.
Audiophile - Anyone interested in the highest quality reproduction of sound.
Audio Signal - An audio frequency signal in electronic form or after conversion to sound.
Auto-termination - In equipment that has loop-through, or "daisy-chain" connections, termination is done at the last device on the chain. Some such devices provide termination automatically by having no cable going out, thus indicating that this is the last device and termination is provided.
Automatic convergence - Automatic alignment of the red, green and blue color images on a screen.
Automatic sync stripping - 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 off of all three video channels (Red, Green, and Blue).
Auto sequencing - A switcher feature that causes the switcher to automatically select each one of its channels in succession, repeatedly sequencing through all channels.
Auto sizing - Automatic picture sizing adjustment to compensate for different display modes, then enabling the display system to center the picture and fill the screen.
Auto switching - Feature which enables a product to detect which input has an active sync signal and to switch to that input.
AVI (A / V Interleaved) - A file format for storing and playing back movie clips with sound on Windows-based PCs. An AVI file is organized into alternating ("interleaved") chunks of audio data and video data. AVI is a "container format," meaning that it specifies how the data will be organized, but it is not itself a form of audio or video compression. Digital video fans may be familiar with AVI as the type of file that's created when DV clips are imported from a digital camcorder to a PC. (These clips are often referred to as "DV-AVIs" because they contain full-quality DV content.)
Axial Modes - The acoustical resonances in rooms that occur between opposing parallel surfaces: walls, or floor and ceiling. See Room Resonances.
Azimuth - The angular distance (side to side) from true north, along the horizon, to the DBS satellite, measured in degrees. During installation of your DBS system, you (or the installer) can punch your zip code or latitude and longitude into the DBS receiver's setup screen and get precise azimuth and elevation angles for your location. You need this information to make sure that your dish is accurately aimed at the satellite.
B-ISDN - Broadband integrated services digital network. A special version of ISDN that uses fiber optics and can transfer at 1.5 megabits per second. Also see ISDN
Backbone - An aggregate data path used to transport signals throughout the building or campus network.
Background Noise - In listening, it is any sound (normally unwanted) that is not part of the sound track being auditioned. In measurement, it is extraneous sound that, if too loud, can cause errors in the measured data.
Back porch - The time in a composite video signal that is between the trailing edge of the sync pulse and the trailing edge of the blanking pulse (before the video information). Also see blanking.
Baffle - The board to which loudspeaker drivers are mounted in a loudspeaker enclosure.
Balanced audio - Method that uses three conductors for one audio signal. They are plus (+), minus (-) and ground. The ground conductor is strictly for shielding, and does not carry any signal. Also called "differential audio".
Balance Control - In stereo systems, a control to adjust relative sound levels in the left and right loudspeakers. In multi channel systems there is a front-back balance adjustment. In car audio, the front-back adjustment is called a 'fader'.
Balanced Connection - A method of interconnecting audio components using a three-wire cable in which there are two signal wires and one ground wire, all of which may be inside a cylindrical shield that is also grounded. The two signal conductors both have the identical impedances to the common ground terminal, hence the name Balanced. Because of this such interconnections are highly immune to ground-originated noises and hum. It is widely used in professional audio systems which routinely have very long cable runs and very complex interconnections of signal and power grounds. The XLR plug is commonly used. See: Unbalanced Connection.
Balun - Impedance matching device converting signals (electrical) from balanced (UTP) to unbalanced (coax).
Banana Plug and Jack - A largish, pin-type, connector commonly used to connect loudspeakers to power amplifiers.
Banding - A video problem when dark bars appear across the displayed image in areas where there is movement.
Bandpass - An adjective describing a system or device that operates only over a specified range of frequencies. In audio, there are bandpass filters, as in loudspeaker crossovers, and bandpass loudspeakers as in bandpass subwoofers. In all cases, frequencies outside of the pass-band range are severely attenuated.
Bandpass Enclosure - A form of low-frequency loudspeaker enclosure in which chambers, drivers, and internal and external ports are configured in an integrated acoustical design that behaves as an acoustical bandpass filter, exhibiting natural low-and high-pass limits to the acoustical output. See: Low-Pass Filter, High-Pass Filter.
Bandwidth - A frequency range, or "band" of frequencies between the limits defined by the "half power points", where the signal loss is -3dB. In audio and video, it is this band of frequencies that can pass through a device without significant loss or distortion. The wider the bandwidth, the better the quality that results, such as a sharper picture, better sound, etc. The higher the bandwidth number the better the performance. (300 MHz is better than 250 MHz.) When a signal passes through a path with more than one device (including cables) the limiting factor (bottleneck) in that path is the device with the narrowest bandwidth.
Barrel - Outward curved edges on a display image. Also see Pin cushion
Barrel connector - Adapter used to connect two coax-type connectors of the same gender.
Barrel Distortion - In video, a form of geometric distortion in which straight lines bulge or bow outward toward the edges of the screen, e.g. making a square look barrel shaped. See: Pincushion Distortion.
Baseband - A prime signal such as composite video, component video and audio having its own path and that is not modulated onto a carrier signal or combined with other signals on a path. An unmodulated signal or band of signal. The video signal seen on a waveform monitor is baseband video signal.
Basket - The outer frame of a loudspeaker driver that supports the magnet, the diaphragm and other moving parts.
Bass - Low-frequency audio signals. Frequencies below approximately 300Hz.
Bass Control - A tone control allowing the user to boost or cut the low frequency portion of the audio signal.
Bass Management - A function in a multichannel surround processor that combines the low bass frequencies from all of the channels (including the LFE channel) in a recording, and directs it to the appropriate loudspeakers. To do this, the customer must tell it the number, kind (small or large), and placement of loudspeakers, and whether there is a subwoofer in the system. See: LFE
Bass reflex - A type of speaker enclosure that includes a "tuned" port to increase and extend bass response (by releasing some of the energy created by the inward movement of the woofer cone). Bass reflex designs are more power-efficient than acoustic suspension designs - they'll play louder than an acoustic suspension speaker when driven with the same amplifier power. But they may sacrifice some bass accuracy in exchange for the added bass output.
Baud - Named for J. M. E. Baudot, the inventor of the Baudot telegraph code. The number of electrical oscillations per second, called "baud rate". Related to, but not the same as transfer rate in bits per second, (bps).
Beaming - See Directivity
Beats - The combination or difference tone heard when two closely spaced frequencies combine in the ear. It is an intermodulation effect, or distortion.
Bend radius - The radius of the arc formed by bending a cable. The most a cable can bend without damage or without adversely affecting its electrical characteristics. The general rule is that the bend radius must be no less than 10 times the outside diameter of the cable jacket. However, it also depends upon the materials that make up the cable.
Bending - A video problem when the top of the screen hooks or bends to the side. Also known as 'hooking."
Bi-amping - Instead of driving a speaker full-range with a single channel of amplification through a single set of speaker cables, you actually connect two sets of cables, with each set carrying the signal from a separate amplifier (or amp channel). This way, both low-frequency drivers (woofers) and high-frequency drivers (tweeters) receive dedicated amplification.
Bi-wiring - Involves connecting two sets of cables to your speakers, like bi-amping, but both sets of cables connect to the same set of output connectors on your receiver or amplifier. Bi-wiring doesn't deliver more wattage to your speakers, so it doesn't offer as dramatic a sonic improvement as bi-amping. Still, many audiophiles find that it offers subtle improvements in imaging and detail.
Bidirectional - When signals can pass in either direction through the same port or by the same path.
Binaural - Literally, two ears, or listening through two ears. Also used to describe recordings made with a dummy head microphone, with microphones at each ear location, intended for playback through headphones or two loudspeaker with acoustical crosstalk cancellation so that the sound of each loudspeaker is heard primarily by only one ear. See Monaural.
Binary - A numbering system using the base-2. Each digit is represented by a 1 or a 0 (on or off ).
Binary code - Coding system using the digits 0 and 1 to represent a letter, numeral or other character in a computer. For example: the character "A" in ASCII code becomes 0100 0001 in binary.
Bipole - A speaker design that generates equal amounts of sound both forward and backward, with the two sounds being "in phase." See also Dipole.
Bit - Shortened form of "binary digit" (0 or 1). A bit is the smallest unit of information in a computer.
Bit map - Method of graphic display using rows and columns of dots, or pixels. Each pixel location corresponds to a location in memory.
Bitrate - Measured as "bits per second," and used to express the rate at which data is transmitted or processed. The higher the bitrate, the more data that is processed and, typically, the higher the picture resolution. Digital video formats typically have bitrates measured in megabits-per-second (Mbps). (One megabit equals one million bits.) The maximum bitrate for DVD playback is 10 Mbps; for HDTV it's 19.4 Mbps.With audio compression, the average amount of data required to store one second of music (expressed in kilobits per second, or Kbps). Some codecs like MP3, WMA, and AAC allow files to be encoded at different bitrates. Generally, as bitrate decreases, so does the sound quality of the resulting file (and also the amount of memory required to store it).
Bit stream - A signal that contains digital data in its undecoded state. An example is the signal that's fed through a DVD player's digital output(s), which carries Dolby Digital, DTS, or PCM signals.
Black - Darkest visible surface; created by the absorption of all incident light and color. In video, the transmission of horizontal and vertical sync signals without picture information.
Black and White - Monochrome (one color) or luma information. In the color television system the black and white portion of the picture has to be one "color": gray, D6500, 6500 K as defined by x and y values in the 1939 CIE color coordinate system.
Black burst - Video waveform without video elements. Includes the vertical sync, horizontal sync and chroma burst information. Black burst is used to synchronize video equipment to align the video output. One signal is normally used to setup an entire video system, or facility. Sometimes it is called "house sync".
Black burst generator - Special device for calibrating video equipment by generating a composite video signal with a totally black picture. This black burst signal is used to synchronize video equipment to provide vertical interval switching. It also provides black level and chroma burst information for maintaining uniform video levels and color information.
Black level - More commonly referred to as "brightness", the black level is the level of light produced on a video screen. The level of a picture signal corresponding to the maximum limit of black peaks. The bottom portion of the video wave form, which contains the sync, blanking and control signals. The black level is set by the "brightness" control.
Blackout area - A pre-defined area of the country where particular programming (often sports or special events) will not be available, usually because of contractual agreements.
Blanking - The turning off of the electron beam that scans the image onto the screen. The interval when the beam completes a scan line and it must return (retrace) back to the left. During this time, the beam must be turned off (horizontal blanking). Similarly, when the last line has been scanned at the bottom of the screen, the beam must return to the upper left ( vertical blanking).
Blanking level - The level of a video signal that separates the picture information from the sync information. The level of the front and back porches is Zero IEEE units. To blank the video signal, the video level is brought down to the blanking level such that nothing is visibly displayed, while the electron beam returns (retraces) to the start of the next line.
Blind Testing - See Double-Blind Listening Test.
Blooming - Most noticeable at the edges of images on a CRT, "blooming" is when the light hitting the screen is too intense and overdrives the phosphors. The edges of an image seem to exceed its boundaries. Thin lines and sharp edges may look thick and fuzzy. This may be caused by the brightness being set too high, or by a high voltage problem.
Blue enhancement - Mixes the right amount of blue information with the green signal for displaying text in a more readable "aqua" color. This color mixing affects all blue colors on the display screen (used only for TTL signals).
BMP (Windows Bitmap Image) - A standard format used for storing color or black-and-white images on Windows-based PCs. BMP images can either be compressed or uncompressed. This type of file also sometimes appears with the .DIB extension.
BNC - Bayonet Neill-Concelman - Cable connector used extensively in television and named for its inventor. A cylindrical bayonet connector that operates with a twist-locking motion. To make the connection, align the two curved grooves in the collar of the male connector with the two projections on the outside of the female collar, push and twist. This allows the connector to lock into place without the need for tools.
Bookshelf Speaker - A small loudspeaker system, capable of fitting on a bookshelf or in a cavity in A/V furniture. However, from a sound quality perspective, shelves and cavitities are the worst possible locations for such loudspeakers. They sound best when mounted on stands away from walls and other objects.
Boomy - Bass reproduction in which certain notes are exaggerated or prolonged by one or more resonances. See Resonance
Boost control - Device that can compensate for losses of signal level or picture contrast that result from increase in cable resistance as cable length increases.
Boundary Effects - In acoustics, the interactions between loudspeakers and listeners, and the room walls, floor and ceiling. Often refers to the interactions with boundaries that are adjacent to the source or receiver.
Bow - Curving of scan lines in the center of the image.
Breakaway - Ability to separate audio and video signals for switching them independently. For example: the audio and video signals from one source may "break away" and be switched to two different destinations. This is the opposite of the term "audio follow".
Breakup - When a loudspeaker diaphragm fails to move in a pistonic fashion, and flexes, or breaks up, distorting the sound.
Breezeway - Early part of the back porch portion of the video signal. The area between the horizontal sync pulse and the color burst.
Bridge(multipointbridge) - Device which allows multiple systems to dial in and participate in a single videoconference.
Bridging Connection - Parallel connection that draws some of the signal energy from a circuit, often with inconsequential effect on the circuit's operation. Combining the outputs of two amplification channels to provide one more powerful channel. Note that bridging may raise the minimum load impedance that the amplifier can safely drive.
Brightness - Usually refers to the amount or intensity of video light produced on a screen without regard to color. Sometimes called "black level". In video displays, the Brightness control is used to set the black level, which determines how dark the black portions of a picture are. In describing sound quality, it refers to an excess of high frequency sound. It can be caused by electronics or loudspeakers with excess output at high frequencies, or by rooms that are too reflective, or live, at high frequencies.
Brightness ratio - Difference between the brightest (whitest) and darkest (blackest) areas in an image. The wider the brightness ratio, the wider the contrast ratio.
Brightness signal - Same as luma (Y) signal; signal carrying information of the light intensity at each point in the image.
Broadband - Communications channel that has greater bandwidth than a voice-grade line and is potentially capable of greater transmission rates.
Buffer - Generally referred to as a unity gain amplifier, a buffer is used to isolate the signal source from the load. A buffer can be used for digital or analog signals.
Burn-in - In video display, this is a term to describe what happens when an image has been displaying too long, resulting in a permanent image being "burned in" to the screen phosphor.
Bus - A path for transporting voltages, signals or ground between the different sections of an electronic device, such as a data bus between a CPU and memory, or a peripheral device. Its width is determined by the number of lines (conductors) that make up the bus, and its speed (data transfer rate) is determined by the circuits that drive the lines. A signal distribution system, normally employing wire, optical fiber, which enables many components to be operated from a single control unit without each being individually linked to it. Some bus systems have two-way communication.
Cable equalization - The method of altering the frequency response of a video amplifier to compensate for high frequency losses in cables that it feeds. Also see peaking.
Cache - A cache is a small, separate portion of memory that a computer (or a program) uses to store information it needs to access frequently. Computers have Level 1 and Level 2 caches. Level 1 cache is small and very fast. Level 2 cache is more commonly used, and is much larger. The more memory in a PC's Level 2 cache, the more operations it is capable of carrying out speedily.
CAD - Computer Aided Design - The use of the computer system for designing, such as in architectural and engineering applications.
Campus Cable - The communications cable that is part of the campus sub-system which connects a series of buildings. There are four methods of installing this cable: in conduit (undergound),direct burial (in trenches),aerial (on poles) and tunnels.
Capacitance - Refers to a materials ability to store a electrical charge and resist sudden changes in the magnitude, or voltage, of that charge. Capacitance in cable results from two conductors in close proximity separated by an insulator or air which forms the capacitor. Capacitance exists between two wires of a twisted pair (mutual capacitance) and between adjacent pairs within the same cable. In the case of shielded cable, it exists between the shield and a pair. The larger the capacitance, the higher the distortion of the signal and therefore, the higher the potential error rate. In general, shielded cable exhibits more capacitance than similarly constructed unshielded cable.
Capacitor - A device made 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".
Captive screw connector - A connector that uses screws that don't fall out when loosened to insert the wires. (Tighten the screws to secure the wires.)
Capture Ratio - A specification describing the ability of an FM radio tuner to lock on to one station when there is another on the same frequency that is only slightly less strong.
Category - A method established to simplify selecting telecommunications media based on application and performance criteria.
Cathode - The electrically negative terminal of a battery, or the electron source of a vacuum tube.
Cathode Ray Tube - See CRT.
CAT 3 - Category 3 - ANSI/EIA (American National Standards Institute/Electronic Industries Association) Standard 568 is one of several standards that specify "categories" (the singular is commonly referred to as "CAT") of twisted pair cabling systems (wires, junctions, and connectors) in terms of the data rates that they can sustain. CAT 3 cable has a maximum throughput of 16 Mbps and is usually utilized for 10BaseT networks.
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 frequencies up to 100 MHz and speeds up to 100 Mbps. CAT 5 is based on the EIA/TIA 568 Commercial Building Telecommunications Wiring Standard.
CAT 5e - Enhanced Category 5 - The standard for the next higher grade of unshielded twisted pair (UTP) beyond Category 5. The CAT 5e specification has been developed to provide more robust support for 1000Base-T. CAT 5e will specify tighter limits than CAT 5 for NEXT, ELFEXT, and return loss.
CAT 6 - Category 6 - 100 ohm Category 6 cabling. 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 6 supports frequencies up to 250 MHz and speeds up to 250 Mbps.
CAT 7 - Category 7 - Proposed and pending standard. Category 7 unshielded twisted pair cable is rated up to 600MHz.
CATV - An abbreviation for Community Antenna Television, another name for cable tv.
CAV - Component Analog Video - Component video signals in which an analog voltage or current (rather than a set of numbers) represents the value of the pixel, the same as "analog components". Encoded video signals that can provide greater color resolution than composite video. An NTSC encoder must be used to convert the signals for a standard NTSC receiver.
CAV - Constant Angular Velocity - Constant Angular Velocity (constant RPM or revolutions per minute). A laserdisk format. Constant Angular Velocity. A method of recording a disc (e.g. laserdisc) in which the rotational rate is kept constant from beginning to end. Each rotation can be contrived to hold the same amount of information, such as a single frame of a picture, making perfect 'pause' functions possible in an analog medium. It is wasteful of space, however, as the density of recorded data reduces with increasing distance from the center of the disc. See: CLV.
CCIR 601(ITU-R BT.601) - Now known as ITU-R BT.601, this is a recommendation developed by the International Radio Consultative Committee for the digitization of color video signals. ITU-R BT.601 deals with color space conversion from RGB to YCbCr, the digital filters used for limiting the bandwidth, the sample rate (defined as 13.5 MHz), and the horizontal resolution (720 active samples). CCIR 601 is a serial digital form of component video. It is roughly equivalent to Y, R-Y, B-Y, but it is digital instead of analog, and is transmitted on one coax cable, instead of three. It is also called 4:2:2, which refers to the number of samples taken from the video channels respectively, in order to digitize and encode it. They sample the Y at four times the speed of the video (which is roughly 6 MHz) and the R-Y and B-Y are sampled at 2 times the speed of the video. The sample values are encoded into 10 bit words, and then transmitted serially, over one line, hence serial digital.
CCTV - Closed Circuit Television - A distribution system which limits reception of an image to those receivers which are directly connected to the origination point by coaxial cable or microwave link.
CD - Compact Disc - An optical disc format for storing digital signals, developed jointly by Sony and Philips.
CD-DA - Compact Disc Digital Audio - the original PCM digital music storage format, defined by the Red Book standard.
CD-R - A disc in the CD format that can be recorded once. Defined by the Orange Book standard.
CD-ROM drive - CD-ROM drives are designed to read CD-ROMs, audio CDs, CD-Rs and CD-RWs. A CD-ROM is a pre-written CD containing data files. A CD-ROM drive differs from a CD-R/W drive in that it cannot write to - that is, store info on - blank discs.
CD-R/W drive - Unlike CD-ROM drives, which can only read discs, CD-R/W drives can read audio CDs, CD-ROMs, CD-Rs and CD-RWs and write to blank CD-Rs and CD-RWs. (CD-R discs can only be recorded upon once; CD-RWs can be re-recorded, usually between 30 and 50 times.) A CD-R/W drive provides an A/V-ready PC with great flexibility, permitting audio CDs to be played via the PC's sound system, and music, digital stills, and other data to be copied to blank CD-Rs or CD-RWs.
Center channel speaker - In a home theater system, this video-shielded speaker is placed above or below your television, and is dedicated to reproducing on-screen sound and dialogue.
CEDIA - Custom Electronic Design and Installation Association. CEDIA is an international trade association of companies specializing in the planning and installing electronic systems for the home. This association offers an annual expo. www.cedia.org
CGA - Color Graphics Adapter - Introduced in 1983, it was IBM's first product to display both color and graphics. An RCA jack above the 9-pin video output connector provides NTSC video. The signal type is TTL, non-interlaced, with pixel x line resolution of 640 x 200 and a color palette of 4/16. CGA has a horizontal scan frequency of 15.75 kHz and vertical frequency of 60 Hz.
Channel - A segment of bandwith used for one complete communications link. A signal path. Stereo consists of two channels, starting from the signal source, and ending at the loudspeakers. Multichannel audio can have 5, 6 or 7 channels, plus a so-called .1 channel for low bass sound effects.
Channel Separation - See: Separation.
Chroma - (chroma signal) - 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 in black and white. (2) The (M) NTSC or (B, D, G, H, I) 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 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) - Cameras, scanners, and digital still cameras. Advantages include good sensitivity in low light and absence of the burn-in and phosphor lag found in CRTs. 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. However, the reporter must take care not to wear colors that are similar to the background color or else the image will appear on the reporter.
Chrominance - The portion of the video signal that carries the color information.It's the color component of a video signal that includes information about hue (shade) and saturation (intensity).Commonly used term for chroma.
CIE - Commission Internationale de l'Eclairage ( The International Commission on Illumination) 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.
Circuit - 2-way communications path between electronic devices.
Circuit Breaker - A device designed to protect other electronic devices by opening the circuit when the system is drawing too much power. Since it uses relay contacts, it can be reset manually or automatically. See: Fuse.
Class A - An amplifier design in which both positive and negative polarities of an audio waveform pass through devices that are active (conducting current) at all times. All low-level analog amplifiers are of this type. Class A power amplifiers are relatively uncommon because they generate a lot of heat, even when no signal is being reproduced, thus requiring enormous heat sinks and many output devices if large amounts of power are needed. See: Class AB, Class B.
Class AB - Basically a Class B power amplifier in which the positive and negative output devices never completely shut off, leaving a residual Class A activity at low signal levels and to smooth the transition from one polarity to the other. Less efficient, and therefore hotter, than Class B, but much cooler running than Class A. The most common form of power amplification. See: Class A, Class B.
Class B - A power amplifier design in which positive and negative polarities of an audio waveform pass through separate output devices that conduct only when needed. It is difficult to eliminate all distortions created when the devices transition from one polarity to the other (crossover distortion), which has relegated this design to low quality audio and other applications of power amplification where efficiency and cost are of greatest importance.
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 which has been terminated due to an error rate being reached 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.
Closed Captions - Text captions that can be made visible on demand. Open captions are a permanent part of the video signal.
Closed loop - A continuous loop of film or tape for repetitive playing, often enclosed in a cartridge.
CLV - Constant Linear Velocity. A method of recording a disc (e.g. laserdisc) in which the rotational rate is varied from start to finish so as to maintain a constant velocity of the 'groove' being read by the playback laser. This results in a more uniform data density over the surface of the disc, from inside to outside, allowing for longer recordings. See: CAV.
CMYK - Cyan, Magenta, Yellow and Black. See Subtractive color.
Coaxial cable - A two-conductor wire in which one conductor completely wraps the other with the two separated by insulation. A coaxial cable has great capacity to carry vast quantity of information with low radiation leakage and in a controlled impedance environment. Constant impedance transmission cable. Example: 75 ohm, type RG-59u cable used for video signals. Abbreviated as "coax".
Coaxial digital - One popular way of moving digital audio from one component to another. Although the jacks and plugs are standard RCA type, special cables designed to handle digital's higher bandwidth are recommended.
Coaxial Loudspeakers - Loudspeakers in which the tweeter is located on the central axis of the woofer, and the two are combined in a single structural unit.
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, Indeo, Cinepak, QuickTime and Video for WindowsÂ® .
Coherence - In listening, it describes a kind of perceptual realism in sounds. In measurements, it is a measure of the correlation between the phases of two or more signals.
Coil - Turns of wire used to create inductance for use in an electrical circuit, or to create a magnetic flux when current is passed through it, or to respond to a changing magnetic field. An electrical impedance of a coil increases with frequency. See also Inductance, Inductor, Voice Coil.
Collision - When signals from two or more connected devices on a network attempting to transfer simultaneously crash into each other. Common on Ethernet systems.
Coloration - Any change in the character of a sound that reduces accuracy, such as an over-or under-emphasis of certain frequencies. In listening evaluations, a perceived characteristic of a sound that was not in the original recording. Coloration modifies the timbre of voices and musical instruments, and is therefore not a good thing.
Color bar - SMPTE standard test bars used to match playback with original recording levels as a reference for color intensity, brightness, contrast and balance. Generated electronically, often accompanied by a 1000 Hz audio tone. A test pattern containing six basic colors: yellow, cyan, green, magenta, red, and blue used to check the chroma functions of color TV systems.
Color burst - In color TV systems, a burst of subcarrier 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 for NTSC is 3.58 MHz and PAL is 4.43 MHz.
Color encoder (Colorplexer) - A device that combines the separate red, green and blue signals into one composite video signal.
Color phase - The timing relationship of the color video signal.Correct color phase will produce the correct color hues.
Color resolution - The number of colors available at one time in an image, measured in terms of bits per pixel.
Color space - A model of the color spectrum with the ordering of colors by three parameters: intensity, saturation, and hue, in a defined 3D space. There are several color spaces with each used to support the specific identity of colors within a structured identification system. In television and video, the CIE 1931 or 1976 color space is most often used.
Color sub carrier - The carrier frequency that contains the color signal information. A 3.58 MHz signal interwoven with a standard NTSC monochrome signal that contains color information.
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. A measure of the color of light. In video, the underlying basis for a picture. A low temperature would be associated with a reddish picture, while a high temperature would yield one more bluish. NTSC standards require 6500 degrees Kelvin.
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. A comb filter's task is to remove residual chrominance (color) information from the luminance (brightness) signal.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 the 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.Comb filtering enhances fine detail, cleans up image outlines, and eliminates most extraneous colors. Comb filters are not required and not used with S-video or component video connections since those connections carry the chrominance and luminance information separately. There are 4 types of comb filters found in today's TVs: Glass - may also be referred to as an "analog" comb filter. 2-Line Digital - compares consecutive scanning lines within one field of video and makes adjustments to reduce cross-color interference. 3-Line Digital - compares 3 scanning lines within a field of video. By comparing more picture information, a 3-line filter further reduces color bleeding and dot crawl. 3D Digital - not only analyzes consecutive scanning lines within a field, but also analyzes the preceding and following fields. Results in improved color purity and a more stable video image, and nearly eliminates dot crawl and color bleeding. Also called 3D Y/C.
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.
Combiner - An active or passive device that serves to combine several signals into one output while maintaining a high degree of isolation between each input.
Common mode rejection (CMR) - 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.
Common mode rejection ratio (CMRR) - (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.
Communications Server - A device (node) connected to a LAN which provides remote communications to and from the LAN.
Compliance - The force required to move an elastically suspended object a certain distance - e.g. the 'stiffness' of a spring. The diaphragm suspensions in loudspeakers have mechanical compliance. The air inside an enclosure has acoustical compliance.
Component video - A video signal that has been split up into its component parts where the brightness (luminance) and color (chrominance) portions of the signal are processed separately.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 3-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.The three-jack component video connection splits the video signal into three parts (one brightness and two color signals) for a more accurate picture with less color bleeding. This type of connection is capable of carrying wider bandwidth video signals, like progressive scan and high-definition video.Component video signals provide greater color accuracy than S-video or composite signals.Nearly all new DVD players and many new TVs include 3-jack component video connections. Why is component video superior to S-video? Where S-video separates the luminance and chrominance portions of the signal, component video goes a step further and splits the chrominance portion into two components. The benefits - improved color accuracy and less color bleeding - are especially noticeable on larger-screen TVs. See also composite video and S-video. Receivers with component video switching allow you to select between multiple component video sources. However, just because a receiver offers component video switching doesn't mean it can pass on all video signals flawlessly. Component video bandwidth is the key figure to look for here. You'll need bandwidth over 10 MHz to pass on progressive-scan video without noticeable softening of the picture. And for HDTV signals, you'll need bandwidth in the upper 20s or higher to avoid noticeable softening of the picture (with most TVs).
Composite Baseband Signal - The complete A / V signal without a carrier wave. Satellite signals have audio baseband information ranging in frequency from 0 to 3400 Hertz. NTSC video baseband is from 0 to 4.2 MHz, PAL video baseband ranges from 0 to 5.5 MHz.
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.A video signal in which the brightness and color portions of the signal are combined. It's a video connection that improves upon the performance of an RF input by splitting the signal into separate audio and video streams. While better than an RF connection, composite video is of lower quality than an S-video or component video connection. A video signal in which the chrominance and luminance signals are combined, along with synchronizing signals. These tend to use cables, looking like yellow audio cables, with RCA connectors. This is the most basic form of video found on virtually all TV's, VCR's, etc. See: Chrominance, Luminance, RCA, S-Video, Component Video.
Compression - AUDIO: A reduction in the dynamic range of a system. This can be done deliberately, as is common in radio broadcasts, or it can be the result of overdriving something, such as a loudspeaker where, above a certain level, the device does not respond proportionally to increases in signal level (see Power Compression). ACOUSTICS: A momentary increase in pressure as a sound wave passes. See: Rarefaction, Sound Wave. DIGITAL DATA: Reducing the amount of digital data required to store audio or video. Data compression can be lossless or lossy, depending on whether the reconstruction is exact or not. Perceptual coding is used in lossy systems. See: Perceptual Coding.
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 with the movement distorted or missing.
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 or projector.
Conductor - Any substance (such as aluminum, copper or gold), usually a wire or cable, that can carry an electrical current with small opposition.
Cone - A cone-shaped diaphragm of a loudspeaker that vibrates and radiates sound. Loosely used to describe all diaphragms, some of which have other profiles, such as domes.
Connectors (pins, plugs, etc.) - There are several different ways to connect the cables from your receiver or amplifier to your speakers. Bare wire connections are acceptable, especially with "spring clip" terminals. However, there are other connector types that provide more solid and secure connections, especially with binding post terminals. Spade connectors are compatible with most binding post terminals. A spade fits around the terminal's central threaded post, allowing you to then tighten the collar down on the spade for a snug, secure connection. But keep in mind, some electronics now have terminals that prohibit the use of spade connectors. Pin-type connectors will work with both spring clip and binding post terminals. This is probably the best type for connecting a thick, heavy-gauge wire to a small spring clip connector. On a 5-way binding post, this slender pin will also fit the hole that's back near the base of the central post. You can then tighten the collar down against it. Banana plugs will plug straight into the center of 5-way binding posts. They make a quick and convenient connection - nothing to loosen or tighten. Double-banana plugs are the same as banana plugs, except the positive and negative banana connectors are both fixed in a molded housing that spaces them 3/4" apart. (These are even quicker and easier to connect than regular, single banana plugs - as long as the terminals on your speakers and/or receiver are true 5-way binding posts with the proper spacing.)
Contact closure - The momentary connection of two conductors to complete an electrical circuit. Often used to switch inputs on switchers.
Continuity - In digital picture manipulators, the characteristic of location/positioning that determines whether the motion path continues smoothly, without interruption.
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 - This is 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. Measures the difference between the brightest whites and the darkest blacks a display can show. The higher the contrast ratio, the greater the ability of a display to show subtle color details and tolerate ambient room light. Contrast ratio is an important spec for front projectors, as well as flat-panel plasma, LCD and LED TVs.
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 align so that 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 misalignment of the colors.
Converter - A device for changing signals from one frequency to another frequency. A device used to transfer signals from a channel of one frequency to another.
Copy protection - A system for preventing the unauthorized reproduction of copyrighted media like movies or music. The DVD format includes both digital and analog forms of copy protection. You will probably not be able to copy DVDs with your VCR. (In fact, because the copy protection system is triggered by a circuit found in most VCRs, simply playing a DVD and running the signal through your VCR will often result in a distorted picture. You should bypass the VCR altogether and connect your DVD player directly to your TV.)
Critical Band - In hearing perception, it is a band, or range, of frequencies over which the ears tend to combine sounds for purposes of detection or loudness perception. It is not the frequency resolution of hearing, as it relates to the perception of timbre, which is much higher.
Critical Distance - The distance from a sound source in a room at which the direct sound and the reverberant sound are equal in level.
Cross color - 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 connect - Distribution system equipment used to terminate and administer communication circuits. In a wire crossconnect, jumper wires or patch cords are used to make circuit connections. In an optical crossconnect, fiber patch cords are used. The crossconnect is located in an equipment room, riser closet, satellite closet or campus IDF facility.
Crosshatch - A test pattern consisting of vertical and horizontal lines used for converging a color display device.
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.
Crossover - A circuit that divides the frequency spectrum into two or more parts. A crossover acts as a filter, allowing certain frequencies to pass through to the speaker while blocking others. It's the crossover's job to send only high frequencies to the tweeter and only low frequencies to the woofer. (And midrange frequencies to the midrange driver in a 3-way speaker.) A high-pass crossover allows only frequencies above the "crossover frequency" to pass through, while a low-pass crossover (common in powered subwoofers) allows only frequencies below the crossover frequency to pass through. A "bandpass" crossover combines a high-pass and a low-pass so that the driver (often a midrange unit) only sees a restricted band of middle frequencies.
Crossover Slope - The rate, expressed in dB per octave, at which audio signals are attenuated as frequencies move into the crossover range. A high attenuation rate, e.g. 24 dB/octave means that there is little interaction between adjacent loudspeaker drivers. Low attenuation rates, e.g. 6 dB/octave allow adjacent drivers to operate simultaneously over a wide frequency range. See: Crossover, Octave.
Crosstalk - This is caused by interference between two signals, usually from an adjacent channel, which adds an undesired signal to the desired signal. Crosstalk is caused by cross modulation, magnetic induction or capacitative coupling, and can occur when there are grounding problems or improper cable shielding allowing leakage between two wire or parallel cables.Crosstalk can also occur in PCB tracks. Video symptoms include noise and ghosting, while audio symptoms include signal leakage. See also Near-End Crosstalk.
CRT (Cathode-Ray Tube) - A CRT ("picture tube") is a specialized vacuum tube in which images are created when an electron beam scans back and forth across the back side of a phosphor-coated screen. 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. Each time the beam makes a pass across the screen, it lights up a horizontal line of phosphor dots on the inside of the glass tube. By rapidly drawing hundreds of these lines from the top to the bottom of the screen, images are created. The regular "direct-view" TVs that most people watch have a single large picture tube, while CRT-based rear-projection and front-projection TVs use three CRTs: one each for red, green, and blue.
Current - The flow of electricity, and the rate at which it flows. Also see Amp.