CABLE EQUALIZATION
CABLE REFLECTIONS
CABLE TV (CATV)
CAMCORDER
CAMERA
CAMERA BREAKOUT
CAMERA SUPPLY
CANDELA
CARDIOID
CAT 5
CCD (Charge Coupled Device)
CCIR
CCIR 601
CCIR 656
CCTV (Closed Circuit TV)
CD
CDI
CGA (Color Graphics Adapter)
CHARACTER GENERATOR
CHIP-SET
CHROMA CORRECTOR
CHROMA KEY
CHROMA NOISE
CHROMINANCE LEVEL
CLAMPING
CLIFF EFFECT
CLIPPING
CLOSED CAPTIONING
COLOR BAR
COLOR BURST
COLOR DECODER
COLOR DIFFERENCE
COLOR FIELD
COLOR FRAME
COLOR IDENTIFICATION SIGNAL
COLOR KILLER
COLOR PHASE
COLOR PROCESSING
COLOR PROCESSOR
COLOR SPACE
COLOR SUBCARRIER
COLOR TEMPERATURE
COLORIZATION
COMB FILTER
COMMUNICATION PROTOCOL
COMPONENT DIGITAL
COMPONENT VIDEO
COMPOSITE VIDEO
CONTOUR
CONTRAST
CONTRAST MIXING
COUPLING
CPI/O
Cr, Cb
CROSS FADING
CROSS PLANES
CROSSTALK
CRT
CTDM
CABLE EQUALIZATION
An electronic process compensating for high frequency losses incurring in long cables due to various cable shortcomings. Equalization is usually performed by special controls or trimmers mounted on the amplifier or switcher which allow variable operation to equalize different cable lengths and qualities. Equalization is best done at the source amplifier, at the beginning of the long cable, to preserve optimal signal-to-noise ratio. Cable equalization (EQ) is also important for fast digital signals. For digital signals, cable EQ is done at the end of the cable. In this case the equalization is usually automatic and no trimming is required.
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CABLE REFLECTIONS
An interfering artifact that appears when a signal which is transmitted via a cable to an acceptor is unable to transfer its energy in full to the load, due to cable shortcomings or improper loading at the remote acceptor. Some of the energy is reflected back to the source (as if coming from a mirror) and is irregularly remixed with the transmitted signal. The result is “ghosting”, artifacts and signal noise.
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CABLE TV (CATV)
A TV system that uses cables rather than antennas for the transmission of TV programs and commercials. In many countries the cable TV network transmits side by side with the regular TV network (MATV). Many commercial stations use cable TV, because it is easier to control and the picture quality is superior to that received from an antenna. Hundreds of channels can be transmitted simultaneously with CATV, which is almost impossible with MATV.
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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.
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CAMERA
(рус. Камера)
See VIDEO CAMERA.
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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.
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CAMERA SUPPLY
A camera power supply. Some professional video cameras can use an external 12 VDC voltage supply which is derived either from a battery belt worn by the cameraman, from a battery within the video recorder itself, from the mains power supply (after down-conversion) or some other DC source. The required 12 VDC supply must be highly regulated. Many problems in camera recording such as black-outs, distorted images, faulty colors and other interference showing on the screen can be the result of a poor power supply.
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CANDELA
(рус. Кандела)
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CARDIOID
A type of microphone with a sound pick-up characteristic and which resembles a heart-shaped sphere. The cardioid microphone is used in applications where a specific pick-up characteristic is needed.
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CAT 5
Category 5, an unshielded cabling system consisting of 4 twisted pairs of wires used for communication and networking. At the end of the CAT 5 cable there is a RJ-45 connector. This was initially used in computer network environments in 10/100 Mbps systems. There are newer, higher bandwidth systems such as CAT 6 and others. The 4 twisted pair system can be used to transfer VGA, video, audio and other signals as well, using the appropriate transmitters and receivers.
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CCD (Charge Coupled Device)
(рус. ПЗС)
A microelectronics chip which stores minute electric charges on a matrix of micro-capacitors. These voltages are bucketed (in the sense of a bucket brigade) from one address to another according to an external-clocking signal. This permits storage of analog memory on the chip. CCD technology was once used in audio to store a signal, which could be retrieved later to create an echo effect via retrieval delay. CCDs are at the heart of video cameras and digital still cameras. Lenses cast a beam of light on the CCD, which acts as a sensor and temporarily stores the visual image. CCDs were used to store a video signal, which was later retrieved for time base correction. Digitally storing video information is performed using digital video tapes (mini DV for example) recordable DVDs, hard disks and large flash memory chips. There are also other types of semiconductor optical sensor devices such as CMOS sensors – which differ in their characteristics, light sensitivity and noise levels.
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CCIR
(рус. ПЗС)
Comite Consultatif International des Radiocommunications. A European committee which was situated in Paris and created and approved standards related to Audio and Video. The committee is no longer active and has been replaced by the International Telecommunication Union (ITU.)
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CCIR 601
(рус. ПЗС)
Specifications and parameters for application of Component Video signals (Y, Cr, Cb) in a 4:2:2 system, recommended by the CCIR, now known as ITU-R BT.601-2.
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CCIR 656
(рус. ПЗС)
The definitions of the parallel connector pinouts, multiplexing schemes, syncs, blanking periods, etc. for parallel and serial interfaces with CCIR 601, now known as ITU-R BT.656.
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CCTV (Closed Circuit TV)
A surveillance system - commonly used in security applications - where the video signals are not publicly distributed. Cameras are connected to television monitors in a limited area such as a bank, a museum, a store, or a parking lot. CCTV video is often of very low quality - usually black and white – and more sophisticated systems in sensitive installations may be connected to frame grabbers recording at very low frame-rates (typically, around one frame per second, or even slower).
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CD
Compact Disk. A digital, optical-based audio, video and computer data storage medium. Audio CDs have taken over from vinyl records in the consumer field, because CD audio quality is very high and unaffected by mechanical problems. In video, CD-ROM and erasable CDs are fast penetrating into Multimedia, video editing and video recording, as digital image quality is high, suffering no generation loss. The DVD will ultimately replace the CD. Video can be recorded on a CD in several formats- low quality VCD, VCR quality SVCD and mini-DVD. The latter can store around 15 minutes of DVD quality video on a standard 700 MB CD. In the computer field, the CD ROM (Read Only Memory) system (player and disk) is used to retrieve enormous amounts of data - text and graphics - up to several hundred megabytes from one disk. Re-writable CDs (CDRW) became very popular for data storage and retrieval but the recordable DVDs with their enormous 4.7 GB storage space (and double that capacity) at an affordable price are pushing CDs into historys dustbin.
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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.
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CGA (Color Graphics Adapter)
An obsolete color standard developed by IBM for personal computers which permits the display of only four colors out of a menu of a total of 16 colors at any given moment, and at a resolution of 320 x 200 lines (on a TTL digital monitor). With special electronic processing hardware, CGA output provided a video image, computer generated, that was used for special effects, animation, titling, etc.
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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.
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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.
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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.
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CHROMA KEY
A process available on better quality special-effects generators and mixers which allows superimposition or replacement of one video picture in a predetermined area of another one. The first picture is photographed with an object or person against a special, single-color background. The complete color content of this particular signal is removed and the second picture is inserted in that area where the background was (See Blue Key).
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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: 1. The chrominance in the video signal is weak. 2. There is excessive color information, which creates over-saturation. 3. A poorly manufactured video device. 4. Low quality videotapes. 5. Poor color decoding. Good color processors reduce or eliminate chroma noise.
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CHROMINANCE LEVEL
The level of color in a video picture as manifested by the strength and saturation of the tones. The higher the chrominance level the stronger the color (e.g., a strong signal produces red, and a weak signal, pink). A strong signal produces a high saturation level and a weak signal, a weak saturation level. Color saturation level can be changed using a color processor. Thus colors can be made stronger or paler. A quality color processor can also change the tint, - red can be changed to green and green to blue.
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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.
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CLIFF EFFECT
Analog signal quality gradually degrades with cable length. Digital signals behave differently. Up to a certain distance, depending on equipment and cables used, the signal is perfect. Extending the cable length by only a few meters beyond that distance may cause a total signal crash which is known as the Cliff Effect.
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CLIPPING
An electronic process for limiting the amplitude of video or audio signals. Sometimes, clipping is performed prior to Modulation and sometimes to limit signal level, so that it will not exceed a predetermined, allowed level. In video, the term SOFT clipping is used when the luminance signal is limited, and HARD clipping is used when both luminance and chrominance signals are limited. Clipping a signal can distort it, resulting in additional, unwanted harmonics.
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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.
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COLOR BAR
An artificial video signal, electronically generated by a signal generator. It produces color bars on the video screen which are used to establish a proper color reference before recording and playback and for adjustment purposes.
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COLOR BURST
A reference color subcarrier signal transmitted at the beginning of each scanning line (during the blanking period) of a composite video signal or the ''C'' component of a Y/C signal. It is used for color synchronization and to establish a reference for the color information following it. The color burst is an amplitude and phase reference for both color hue and color intensity. It is transmitted at the DC voltage level which is practically the black level of the signal. The luminance signal, which follows the color burst, should not fall below the color burst level. Black level clamping is usually performed in the color burst area.
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COLOR DECODER
A device which breaks down the video signal to its color components – Red, Green and Blue, or color difference components. A color decoder chip set is used in TV receivers, for example, and the recovered color signals are used to drive the CRT.
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COLOR DIFFERENCE
Component video uses Y (luminance) and two color difference signals: R-Y and B-Y representing - in a formula - the red and the blue contents of the signals. The color difference signals are derived from a calculated subtraction of the luminance part from each of the signals representing the red and blue parts of the video signal. YIQ and YUV are derived from similar formulas.
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COLOR FIELD
The number of a specific field in a color frame sequence (1 to 8 in PAL, 1 to 4 in NTSC.)
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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.
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COLOR IDENTIFICATION SIGNAL
See BOTTLES.
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COLOR KILLER
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.
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COLOR PHASE
The timing relationship in a color video signal which keeps the hue of a color signal correct, measured in degrees. Color information is encoded in the video signal as the difference in phase between the sine peaks of the chrominance signal and the color burst subcarrier signal. If the two signals overlap exactly, then the phase difference is designated as zero degrees. If the sine signals do not overlap, the color phase can vary from 0 to 360 degrees. Each shift in the color phase represents a specific tint on the screen. If two sine waves are shifted one from the other by 180 degrees, then the colors are totally inverted.
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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.
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COLOR PROCESSOR
See CHROMA Corrector.
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COLOR SPACE
A mathematical way to describe color information. In different color space schemes all the different formulas used describe essentially the same colors.
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COLOR SUBCARRIER
A standard monochrome video signal has additional modulation frequency bands (sidebands) added in order to convey color information. These are the color subcarrier components. Using the color burst as a reference, the ratio of the color subcarrier of the video signal to the burst indicates the intensity of the colors (in PAL and NTSC). Thus, when there are relatively limited color subcarrier components in the video signal, the colors are weak or pale. The system is, in fact, a little more complicated than this since in PAL and NTSC the color subcarrier contains red and blue information simultaneously which must be further processed to RGB by a color decoder in the monitor.The color subcarrier frequency in PAL is about 4.43 MHz and in NTSC it is about 3.58 MHz. Since it resides outside the highest luminance frequency, the relevant usable luminance frequency is limited to about 4 MHz in PAL and to about 3 MHz in NTSC (when using simple analog filters.) The luminance frequency response after separating chrominance from luminance may be much higher when using a digital Comb Filter.
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COLOR TEMPERATURE
Indicates the hue of the color. The term is derived fr om photography wh ere the spectrum of colors are based upon a comparison with the hues produced when a special metal body is heated from red through yellow to blue, which is the hottest. Color temperature measurements are expressed in degrees Kelvin.
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COLORIZATION
A process which allows painting a black/white or even a color video image with artificial colors.
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COMB FILTER
Circuitry designed for best separation of Y and C from a composite video signal. Standard circuitry uses analog bandpass and bandstop filters, which result in unclean separation of Luma from Chroma, possible phase shifts (hue changes), signal delays and a host of other undesirable effects. Comb filtering is a digital process, separating Y from C, based on “combing” out the chrominance signal from the luminance. It is called comb filtering because chroma resides in specific bands along the frequency axis which resemble a comb. The drawbacks of digital comb filtering are some undesirable effects due to digitization of the video signal, higher cost than analog filters and sometimes the need for time base correction prior to “combing” in order to obtain the best results.
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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 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.
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COMPONENT DIGITAL
A digital form of Component Analog signals usually related to CCIR 601 (ITU-R BT. 601-2.)
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COMPONENT VIDEO
A simple composite video signal comprises luminance information, color information (chrominance) and sync information in one transmission channel. When performing video image improvement operations and special effect generation on a composite video signal, a trade-off between color quality and picture resolution is unavoidable. To achieve maximum video quality, professional equipment therefore uses one of several component systems which split the signal into several channels: RGB splits the video signal into its red, green, blue, and sync components. The YUV system uses a different set of components: luminance + sync, and red/blue color difference. The Super-video (Y/C - Super-VHS and Hi-8) system, separates the luminance and chrominance components. Different types of equipment are required for each format and each component system has its own advantages and disadvantages. In a video studio, it is not uncommon to find a composite or Y/C video recorder, an RGB camera and a component YUV mixer. Special interface units are needed to bridge between the various formats of video.
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COMPOSITE VIDEO
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CONTOUR
(рус. Контур)
An accentuated edge defining a video or a computer generated image.
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CONTRAST
Contrast is a function of differences in intensity between the darkest and the brightest areas of a picture. When contrast is high the picture contains sharp blacks and whites. When low, the picture shows only variations in gray tones. Excessive contrast can result from improper illumination or photographing in harsh sunlight. In such a case, it can be corrected using a video processor. In the same fashion, a low contrast image, which is the result of insufficient illumination, can be enhanced. Very few video processors on the market today offer real contrast control.
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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.
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COUPLING
A way to interface between two machines or signals. In video and audio, coupling can be direct – called DC coupling, through capacitors – called AC coupling, using transformers – called inductive coupling, by opto devices - using optocouplers or using RF (radio frequency) transmitters and receivers. DC coupling preserves the original DC levels of the signals and insures maximum signal flatness. However, erroneous DC levels, if they exist, are transferred between the machines and may cause damage. AC coupling practically isolates the two machines or signals from their respective DC components, but has the problem of poor low frequency response and signal breathing effect. For example, video switchers and DAs may have AC or DC coupling either at the inputs, outputs or both. A smart system allows the user to decide which way the signals should be coupled to and from the DA or switcher. Transformer coupling is problematic in the video field, mainly because of bandwidth considerations, as the transformer should perform equally in all relevant frequencies, and magnetic core transformers hardly ever do so, especially when a true flat response is needed. Transformer coupling is used in the audio field mainly for maintaining proper balanced signals, for impedance matching and for ground isolation - as ground loops may be quite harmful in audio. It is used in video as well for similar reasons. Opto-coupling in video is mainly used to link devices in remote locations, by using fiber optics technology instead of coaxial connections, thus extending substantially the range of operation. RF connection is mainly used in radio, TV and cable transmissions, in microwave links - node to node for ENG and in satellite transmissions. RF modulators and demodulators are needed to maintain the link. RF offers the longest connection range of all systems, crossing continents, oceans and even outer space.
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CPI/O
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Cr, Cb
Digital red and blue color difference signals.
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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.
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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.
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CROSSTALK
The interference of one signal by an adjacent one caused by stray electromagnetic or electrostatic energy. For example audio crosstalk results from leakage, -between the left and the right channels or between different inputs. In video, crosstalk between input channels can be classified into two basic categories: luminance /sync crosstalk and color (chroma) crosstalk. When crosstalk in video is too high, images from one source appear as ghosts on the other. Low crosstalk is an essential feature for any audio and video device and is based on accurate design and proper signal handling. Crosstalk risk gets higher with higher signal frequencies.
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CRT
(рус. ЭЛТ)
Cathode Ray Tube. A vacuum tube which produces light when an electron beam hits its internal surface. A ''gun'' which creates electrons and a high voltage source that accelerates them generate the electron beam. The CRT is used as a picture displaying tube in video monitors, TV sets, computer monitors and others. It is assumed that the CRT will be replaced in the future by flat displays – such as LCD/TFT, Plasma or other modern types.
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CTDM
(рус. ЭЛТ)
Compressed Time Division Multiplex. A color component time compression system used by BETACAM VTRs. The two-chrominance signals (R-Y and B-Y) are compressed, multiplexed and recorded at the same time as the luminance signal.
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