Glossary 113
XGA A type of video signal with a resolution of 1,024 (horizontal) ^ 768 (vertical) dots that is used by IBM PC/AT-compatible computers.
Aspect ratio The ratio between an image's length and its height. HDTV images have an aspect ratio of 16:9 and appear elongated. The aspect ratio for
standard images is 4:3.
Interlace A method of image scanning whereby the image data is divided into fine horizontal lines that are displayed in sequence starting from left
to right and then from top to bottom. The even-numbered lines and odd-numbered lines are displayed alternately.
Gateway address This is a server (router) for communicating across a network (subnet) divided according to subnet masksg.
Contrast The relative brightness of the light and dark areas of an image can be increased or decreased to make text and graphics stand out more
clearly, or to make them appear softer. Adjusting this particular property of an image is called "contrast adjustment".
Component Video A video signal which has the luminance component and color component separated to provide better image quality.
Refers to images that consist of three independent signals: Y (luminance signal), Pb and Pr (color difference signals).
Composite video Video signals that have the video brightness signals and color signals mixed together. The type of signals commonly used by household
video equipment (NTSC, PAL, and SECAM formats). The carrier signal Y (luminance signal) and chroma (color) signal that are
contained in the color bar are overlapped to form a single signal.
Subnet mask This is a numerical value that defines the number of bits used for the network address on a divided network (subnet) from the IP address.
Synchronization The signals output from computers have a specific frequency. If the projector frequency does not match this frequency, the resulting
images are not of a good quality. The process of matching the phases of these signals (the relative position of the crests and the troughs in
the signal) is called Synchronization. If the signals are not synchronized, flickering, blurriness, and horizontal interference occur.
Tracking The signals output from computers have a specific frequency. If the projector frequency does not match this frequency, the resulting
images are not of a good quality. The process of matching the frequency of these signals (the number of crests in the signal) is called
Tracking. If tracking is not carried out correctly, wide vertical stripes appear in the signal.
Dolby Digital A sound format developed by Dolby Laboratories. Normal stereo is a 2-channel format that uses two speakers. Dolby Digital is a 6-
channel (5.1-channel) system which adds to this a center speaker, two rear speakers, and a sub-woofer.
Progressive A method of image scanning whereby the image data from a single image is scanned sequentially from top to bottom to create a single
image.
Refresh rate The light-emitting element of a display maintains the same luminosity and color for an extremely short time. Because of this, the image
must be scanned many times per second to refresh the light-emitting element. The number of refresh operations per second is called the
Refresh rate and is expressed in hertz (Hz).