Please select a letter for terms starting with that letter:

- V -

VESA
Video Equipment Standards Association; a computer industry association which regulates video output standards for the SVGA graphics modes.

Ventilation
Airflow through a projector's internals for the purpose of cooling the lamp, or light source.

VGA
A video resolution equating to 640x480 pixels in size; acronym for Video Graphics Array.

V
(1) Vertical (as in RGBHV), or the vertical sync connector on a panel. This is used when the sync is separated into horizontal and vertical components. (2) In electrical specifications, "v" is the Acronym for "volts".

Validation
The process of measurement and evaluation to verify courseware requirements prior to replication and distribution.

Value Added Reseller
A party who purchases a product, adds something to it, such as hardware or software, and then sells it as a package.

Values
A numerical designation of lightness, with white having high and black low values. All colors have a value relative to black or white. See also "Gradation".

VAR
Acronym for Value Added Reseller.

Variable Level Control
This control is a variable voltage level control similar to a contrast control on a data monitor. The level control increases or decreases the levels of red, green and blue simultaneously, thus not affecting the adjusted gray-scale of the monitor or projector.

Varifocal
As in the lens type and what these lenses on OHPs does for projected images (usually severe barrelling).

VCR
Acronym for video cassette recorder. In Europe, however, VCR is a trademark for a particular _"video format developed by Philips of the Netherlands".

Vectorscope
A specialized oscilloscope used in video systems to measure chrominance.

Vertical Blanking
Retrace. The turning off of the scanning electron beam in a CRT during the time the beam must return from the bottom of the screen to the top. Vertical blanking occurs between writing each field of a picture. If vertical blanking does not occur, a diagonal "retrace" line will display from lower right to upper left of the screen. Also see "retrace".

Vertical Blanking Interval
The blanking time at the beginning of each field. It contains equalizing pulses and vertical sync pulses.

Vertical Interval
The synchronizing information which is presented between fields, and then signals the picture monitor to return to the top of the screen to start another vertical scan.

Vertical Resolution
Also known as vertical definition. The number of distinct horizontal lines, alternately black and white, that can be seen in a TV image. Vertical resolution is fixed by the number of horizontal lines used in scanning.

Vertical
Shift, or Vertical Centering Control - Adjusting the vertical centering control one way shifts the displayed image toward the bottom of the monitor or projector screen and the other way shifts the displayed image to the top of the monitor or projector screen.

Vertical Sync Pulse Width Switch
A switch on the RGB 108 Plus and RGB 202xi interfaces that widens the output of the vertical sync pulse width from 180 microseconds to 500 microseconds.

Very High Frequency
Television broadcast range between 30 and 300 MHz , on channels 2 through 13.

VESA
Acronym for Video Electronics Standards Association.

VGA
Acronym for Video Graphics Array.

VHF
Acronym for Very High Frequency.

VHS
Acronym for Video Home System.

Video
Refers generally to any method using video tape or television technology to produce an image. A process of recording and transmitting information that is primarily visual, by translating moving or still images into electrical signals. These signals, typically include audio signals, can be broadcast (live or prerecorded) using high-frequency carrier waves, or sent through cable on a closed circuit.

Video Amplifier
A low-pass amplifier with a bandwidth of 2 - 10 MHz, used to strengthen the video signal for TV transmission and reception.

Video cassette recorder
In Europe, however, VCR is a trademark for a particular _"video format developed by Philips of the Netherlands".

Video Card
A circuit board that is usually mounted inside the computer that generates signals necessary to drive, or control a specific type of monitor.

Video Connector
The connector on the video card or computer's graphics output that is connected to the video input on the local monitor.

Video Converter
See "scan converter".

VideoDisc
A read-only storage medium that uses a laser light beam to read information from the surface of a disc. The information in optical videodiscs is encoded in the form of microscopic pits pressed into the surface of the disc. The pits of small holes modulate the laser in a manner that can be decoded by the videodisc player. Information stored in these pits is read by the laser beam and transmitted to the decoder inside the videodisc player.

Video Distribution Amplifier
An amplifier for strengthening the video signal so that it can be supplied to a number of video monitors at the same time.

Video Electronics Standards Association
A nonprofit member organization dedicated to facilitating and promoting personal computer graphics through improved graphics standards for the benefit of the end-user.

Video Full-Motion
Video reproduction at 30 frames per second (fps) for NTSC signals or 25 fps for PAL signals. Also known as continuous-motion video. In the videoconferencing world, the term "full-motion video" is often used, and often misunderstood. Videoconferencing systems cannot provide 30 fps for all resolutions at all times nor is that rate always needed for a high-quality, satisfying video image. Picture quality must sometimes be sacrificed to achieve interactive visual communication across the telephone network economically. Videoconferencing vendors often use "full-motion video" to refer to any system that isn't still-frame. Most videoconferencing systems today run 10 to 15 frames per second at 112 Kbps.

Video Gain
The amplitude of a video signal.

Video Graphics Array
Introduced by IBM in 1987, VGA is an Analog signal with TTL level separate horizontal and vertical sync. The video outputs to a 15-pin, HD connector and has a horizontal scan frequency of 31.5 kHz and vertical frequency of 70 Hz (mode 1, 2) and 60 Hz (mode 3). The signal is non-interlaced in modes 1, 2, 3 and interlaced when using the 8514/A card (35.5 kHz, 86 Hz) in mode 4. It has a pixel by the line resolution of 640 x 480 with a color palette of 16/256,000.

Video Home System
The 1/2" videocassette format originated and developed by JVC and adopted by a number of different manufacturers. Not compatible with the Beta format, which is also 1/2", but differs electronically.

Video Loop Back
A feature in some switchers that allows a video signal to exit to another device, such as a decoder or scan-doubler. The output from that device is then used as another input to the switcher.

Video Projector
A device which projects a video image onto a presentation surface.

Video Quality
A representation of the quality of video from best to worst:

• RGBHV (BEST QUALITY)
• RGBS (HDTV)
• RGsB
• R-Y, B-Y, Y/YUV/Component Video (DTV - firewire)
• S-Video
• Composite Video
• Cable TV
• Hotel TV (WORST QUALITY)

Video Standards
See NTSC, PAL and SECAM.

VideoShift^™
A technique used to move a video image around on the screen to prevent "burn-in", or destruction of the phosphor. A typical example would be flight schedule monitors in airport terminals, where the same image stays on the screen for long periods of time.

Video Test Generator
An Extron device that generates video test patterns at scan rates that simulate most popular applications.

Viewing Angle
Screens do not reflect equally in all directions. Most light is reflected in a conical volume centered around the "line of best viewing" or along the "on axis". A viewer located along the surface of the cone sees only 50 percent of the maximum brightness. Curved screens usually have smaller viewing angles than flat screens. Also applied to the transmitted light coming from direct view screens in a similar way.

Virtual Memory
The process of increasing the apparent size of a computer's random-access memory (RAM) by using a section of the hard disk storage as an extension of RAM.

Virtual Disk
A disk that is simulated in memory and usable, but not physically present in the computer.

Virtual Memory
A technique that simulates more memory than physically exists in a computer system and allows the system to access this memory to run additional programs or to increase the speed of its operations.

Virtual Reality
A multimedia environment that simulates a multi-sensory 3-D experience based upon a user's actions in physical space.

VLB
Acronym for Video Loop Back.

Volt
The potential difference or electromotive force that will cause current of one ampere to flow through the resistance of one ohm. Symbolized by "v".

Voltage
The potential difference or electromotive force expressed in volts. See volt.

Voltage, Maximum Input
The maximum voltage that can be applied to an input channel without damaging the input circuitry.

Voltage, Minimum Input
Amplitude (voltage) measurement of the minimum amplitude. Typically the most negative peak voltage.

Volume Unit meter
For sound systems or recorders, a device to indicate the relative levels of the various sounds being recorded or played. Usually calibrated to show a maximum recording level to avoid tape saturation and distortion.

VS
Extron's product designation for VideoShift^™.

VTG
Acronym for Video Test Generator.

VU Meter
Acronym for Volume Unit meter.

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