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Glossary of Terms
Amorphous A type of LCD using non-crystalline silicon.
Analog Signal A continuous signal that takes time to make a transition from one level to another.
Standard audio and video signals are analog. This signal has an infinite number of levels between its
highest and lowest value. (Not represented by bits, such as with digital.)
Aspect Ratio Horizontal dimension of a picture expressed relative to the vertical dimensions. The aspect
ratio of all broadcast composite video systems is 4 units wide by 3 units high.
Bandwidth A frequency range, or "band" of frequencies, within which a device operates.
Brightness Ratio The difference between the brightest and darkest object in a picture. Too much of a
difference can cause unacceptable contrast.
CGA (Color Graphics Adapter) In 1983 IBM introduced their first product to display both color and
graphics. Pixel x Line resolution of 640 x 200. The horizontal scan frequency of 15.75 kHz and vertical
frequency of 60 Hz. The output is a 9 pin "D" type connector.
Chrominance Signal The signal that represents color in a video picture. Chroma is the characteristics of
color information independent of luminance intensity. Hue and saturation are qualities of chroma.
Chrominance is abbreviated as "C".
Composite Video A mixed signal comprised of the luminance black and white, chrominance (color),
blanking pulses, sync pulses and color burst.
Contrast Degree of difference between the lightest and darkest parts of a picture. Low contrast is shown
mainly as shades of gray, while high contrast is shown as blacks and whites with very little gray.
Convergence The alignment of the Red, Green, and Blue video on a projected display.
DOT Clock (also Pixel Clock) The highest data rate that a graphics device can produce.
Frequency Range Refers to the low-to-high limits of a device, such as a computer, projector or monitor.
Also "bandwidth."
Hertz (Hz) A measure of frequency in cycles per second.
Horizontal Rate (Frequency) The number of complete horizontal lines, including trace and retrace,
scanned per second. Typically shown as a measure of kHz.
Hue (Tint Control) Red, yellow, blue, etc., are hues of color, or types of color. Hue is the parameter of
color that allows us to distinguish between colors. Interlaced The process of scanning whereby the
alternated lines of both scanned fields fall evenly between each other.
Keystone Effect A distorted picture where one edge is not the same dimension as the opposite edge.
Typically results when the image is projected at an angle. In stone buildings, the tapered stone at the top
of an arch was the "key" that prevented the arch from falling.
Kilohertz (kHz) Thousands of Hertz, or a frequency rate in units of thousands of cycles per second. For
example: CGA's horizontal scan rate is 15,750 hertz (Hz), or 15.75 kHz.
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