G-Y Signal
Color mixture close to green with a bandwidth of 0 to 0.5 MHz. Usually formed by combining B-Y and R-Y video signals.
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Gain
1) A general term used to denote an increase in signal power or voltage produced by an amplifier in transmitting a signal from one point to another, or equivalently, the logarithmic ratio of the output to input signals. The amount of gain is usually expressed in decibels (dB) above a reference level. Opposite of attenuation. 2) The amplification of a signal, unit or system. Expressed in the unit of measurement appropriate to the signal or system, or in a mathematical formulation (Y x Z) for screens. 3) A projection screen has gain when in one way or another it can be measured as being brighter than the reference standard, an illuminated block of magnesium carbonate (MgCO3). See Screen Gain.
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Gain Bounce
A descriptive term for the display gain changes that may occur when the APL shifts dramatically between pictures. See Average Picture Level.
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Gamma
The light output of a CRT is not linear with respect to the voltage input. This non-linearity follows an exponential function called "gamma."
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Gamma Correction
Compensation in a video monitor for the nonlinear gamma characteristic of the camera or the picture-tube phosphors.
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Genlock
A method of synchronizing video equipment by using a common, external "genlock" signal. This locks the sync generators of multiple devices to a single source.
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Geometric Distortion
Deviations from geometric linearity. Flaws in a display device's ability to accurately reproduce lines, shapes, and sizes.
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Geometry
The symmetry and uniformity of a video image's display. With ideal geometry all the lines of a crosshatch test pattern are straight and produce squares of equal size.
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Ghost
A shadowy or weak image in the received picture, offset either to the right or to the left of the primary image. It is the result of transmission conditions where secondary signals are created and received earlier or later than the primary signal caused by a reflected signal. Ghosts can also be the result of burning an image on a screen or by a mirror.
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Ghosting
See Multipath Distortion.
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GHz
Gigahertz. One billion Hertz or cycles per second.
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GIGA
The prefix abbreviation for billions. (G) e.g. One G-byte = 1 billion bytes.
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Gigahertz
See GHz.
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Glitch
Picture distortion or technical malfunction.
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Good Picture
One that conforms to the NTSC idea of a good picture. A good picture is one that accurately reproduces the information contained in the incoming video signal.
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Grand Alliance
Consortium of U.S. broadcasters, manufacturers and engineers that have drawn up the standard for digital HDTV. See HDTV.
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Graphic Equalizers
Equalizers which provide a visible display of the frequency response curve by the relative position of controls on the unit.
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Graphics Grade Projector
A Graphics grade projector will usually handle everything in the Data grade category up to, and including, the 1125 or 1250 line proposals for HDTV, plus higher scan rates, such as those from Silicon Graphics work stations. There are exceptions. Some Graphics projectors will not display NTSC or PAL without first having those signals up-converted.
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Graphics Monitor
A monitor with horizontal scan capable of 15.75 -75 (80) kHz. Graphics monitors and projectors accept inputs from NTSC Video, CGA, and VGA, as well as, high resolution workstations.
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Gray Scale
1) A test pattern consisting of a row of different shades of gray, ranging from white to black. 2) A display device's ability to reproduce all the steps of a gray scale pattern (series of regularly spaced tones ranging from white to black), uniformly and with the correct color of white-6500°K.
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Grazing Effect
The way in which sound is absorbed by the audience; stepping or raking the seating reduces the absorption, and improves sight lines. Any implied relationship between people and ruminants is purely coincidental.
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Ground
A conducting path between an electrical circuit (or equipment) and the earth (or some conducting body serving in place of the earth).
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Ground Loop
A state where too many electrical grounds are connected at different points.
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Grounding
1) A signal path to earth where a physical connection with earth provides a potential attracting unwanted electrical transients. Generally created by 10-feet copper rods driven into the earth. The rods are then connected to the electrical service ground buss or a separate connection to equipment chassis. An electrical ground and an earth ground may or may not describe the same connection. If multiple paths are available to the "ground" (earth connection) a ground loop can occur. See Ground Loop. Metallic shielding of electrical signals is nonexistent without proper grounding. If there is one ubiquitous problem in audio, it is the inattention to proper grounding procedures. 2) The earth potential path becomes unstable with varying potentials between different pieces of equipment. As the potential varies new circuit path loops are created. This usually causes an audible frequency (60Hz in the United States; plus harmonics) hum from the electronics to the speakers. See GLI.
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