CableCARD Credit-card-sized device that inserts into a CableCARD-compliant television and replaces a separate cable box.

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.

cathode ray tube See “CRT.”

center channel In a multichannel audio system, the audio channel that carries information that will be reproduced by a speaker placed in the center of the viewing room between the left and right speakers. The center channel carries nearly all a film’s dialog.

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 center-channel information such as dialog and other sounds associated with onscreen action.

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 front-channel sounds in Dolby Surround leaking into the surround channels. High channel separation results in more precise placement of sounds.

chrominance (chroma)The color-carrying portion of a video signal. The chroma signal carries color and hue, but little brightness information.

Class-A Mode of amplifier operation in which a transistor or tube amplifies the entire audio signal.

Class-AB Mode of amplifier operation that is similar to Class-B except that both tubes or transistors operate when the voltage is near 0V. Distortion is higher at low signal levels than Class-A, but efficiency is higher, though not as high as Class-B.

Class-B Mode of amplifier operation in which one tube or transistor amplifies the positive half of an audio signal, and a second tube or transistor amplifies the negative half.

Class-D Mode of amplifier operation in which the output transistors are switched fully on or fully off in pulses. The pulse duration determines the signal’s amplitude. Also called a “switching” or “digital amplifier.”

coaxial cable A cable in which an inner conductor is surrounded by a braided conductor that acts as a shield. Coaxial cable is used between a TV antenna and a VCR or TV, between a DBS dish and a DBS receiver, and sometimes between a VCR and a TV set. It is also used to deliver cable-TV signals into the home.

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).

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 temperature Measurement, in kelvins, of a video display’s reproduction of gray. Too low a color temperature and the color gray has a red cast. Too high a color temperature and the color gray has a blue cast. The ideal color temperature is represented as 6500K.

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 circuit that splits a composite video into separate color and brightness signals.

component video A video signal split into three parts: luminance and two color-difference signals (technically known as Y, B – Y, R – Y, or YPbPr). A superior method of connecting video compared to composite video.

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 video A video signal in which the luminance (brightness,or black-and-white) information and the chrominance (color) information are combined into a single signal. Composite video inputs and outputs appear on RCA jacks.

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.”

congested A thickening of the sound that makes instrumental images less separate and distinct.

contrast The range between white and black in an image.

controller Another term for an A/V preamplifier.

convergence The integration of various technologies, such as digital video, digital audio, computers, and the Internet.

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 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 “cut off frequency.”

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), “third-order” (18dB/octave), and “fourth-order” (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.

crosstalk See “channel separation.”

CRT (cathode ray tube) A vacuum tube in which electrons are fired at a screen coated with phosphors that give off light when struck to produce a visible pattern (a picture). Direct-view television sets use a large CRT. Some front-projectors use three small CRTs to project an image.

current The flow of electrons in a conductor. For example, a power amplifier “pushes” electrical current through speaker cables and the voicecoils in a loudspeaker to make them move back and forth.

cutoff frequency See “crossover frequency.”