Brightness. The black and white portion of the TV signal. Other names for this signal are luminance, luma or Y.
Burst signals determine picture hue. For a short time between video lines, the normal color signals don't transmit. In their place on the color subcarrier is the color sync signal. Engineers call this invisible signal the "color burst" signal. The burst assures a reasonable match between your TV set's colors and the station colors.
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Chroma. Another name for the part of the color signal that defines color saturation. Engineers define this signal with various symbols. In the original NTSC system, chroma consists of I (in-phase) and Q (quadrature) signals. The studio superimposes these signals. Signals I and Q transmit simultaneously.
Color Difference Signals. The three color difference signals are R-Y, G-Y and B-Y. These three signals contain color information, but not brightness information. The luminance or Y signal contains the brightness information.
CRT. Cathode-ray tube or picture tube. Vacuum tube display that reproduces pictures by exciting a luminescent screen with an electron beam.
EIA. Electronic Industries Alliance, formerly Electronic Industries Association, Radio Manufacturers Association, and other names.
Field. A TV field is a complete picture from top to bottom. Your TV set draws pictures from horizontal lines. As they scan across the set, the lines vary in gray content. Each field contains only every other picture line. The TV set builds up a detailed picture from two fields. The second field fills in the gaps of the first one.
Field-sequential color TV. In field-sequential color TV, each field indicates saturation values for one of three primary colors. In sequence, the TV receiver reproduces the field for one color at at time: Typically, R (red) — B (blue) — G (green), in that order. (Peter Goldmark set up this preferred order during his audience research for CBS.) Each field also conveys gray tones or Y data.
Frame. When the tv system combines two fields, the resulting detailed picture is what we call a frame.
Horizontal Sync. Between video lines, the station transmits horizontal sync pulses. The horizontal sync signal is a train of short pulses. These pulses recur about every 63 microseconds.
Hue is the tint or color of an object. For example, the hue of a leaf is green. NTSC TV color space has three components: Hue, saturation and brightness. Each one of these components associates with its own signal. Hue actually refers to the position of a vector on a polar coordinate system. The polar system looks like a clock or compass face. This clock face is in fact a virtual color wheel. A hue vector points to a single hue on this color wheel.
I and Q. The signal names I and Q refer to axes on a polar coordinate system. (For example, a vectorscope.) The I axis defines colors between orange and roughly cyan, two complementary hues. The chosen orange is close to a flesh tone color (for all races). The Q axis defines colors between green and magenta. These are also complementary colors. Because the eye is particularly sensitive to flesh tone reproduction, the I axis offers three times the definition (bandwidth) of the Q axis. Yet most TV receivers reproduce only a third of the I signal, making it equal to the bandwidth of the Q signal. European TV uses red (R-Y or V) and blue (B-Y or U) for the two color primaries. The European primary bandwidths are equal in size.
Luminance. In the background of a color picture, the regular black and white picture keeps on transmitting. Technicians call the black and white part the "luminance" signal. Really, luminance is a $64,000 term for brightness. Luminance is a broadband signal. It transmits at higher detail than do the colored picture components.
Matrix. In a TV receiver, a resistor matrix mixes the color difference signals with the luminance signal. Sometimes the matrix is the CRT itself. The result is TV pictures in natural colors. Another matrix at the TV station converts color difference signals to the I and Q signals that transmit.
NTSC. The standards body that established the engineering design for color TV in the US. The first NTSC color standard came out in 1953. An earlier NTSC also set standards for monochrome TV in 1941. Over the next half-century, NTSC standards underwent several revisions. The NTSC began as a part of the EIA, an industry trade group.
Pixel, or pixture element. (Also pel.) The smallest visible part of a picture. In color TV, the pixel actually has three components, the R, G and B subpixels. None of these subpixels is available as a “smaller pixel.”
QAM. The transmission mode for television color information. Chroma is an AM signal with two components, I and Q. The I and Q signals are 90 degrees out of phase with each other. That is, these two signal phases are orthagonal, or in quadrature.
Synchronous Demodulator. To demodulate the QAM signal, the receiver must have two synchronous demodulators. Each demodulator is an AM detector that is only active during one phase. The burst signal provides a phase reference (Phase Zero) that locks the receiver to the station. Then the receiver shifts the burst to produce proper phase references for the two demodulators. For example, one phase reference enables the blue or B-Y detector. Another phase reference, 90 degrees away, enables the red or R-Y detector.
Vertical Sync. Between video fields, the station transmits vertical sync pulses. The vertical sync signal is a train of short pulses. These pulses recur about every 16 milliseconds.
Y. Engineering shorthand for the luminance signal. Luminance is the same as brightness. It is the black-and-white part of the color signal.
Yoke. Yoke coils scan the electron beam across your picture tube. The TV set has two vertical and two horizontal coils. The coils are actually large electromagnets. An invisible part of the TV signal feeds the yoke coils, causing an increasing and decreasing electromagnetic field. The yoke uses this field to deflect the electon beam in the CRT. Deflection causes the electron beam to spread out from one dot to cover the entire screen.