V

Vacuum Evaporation (computer/microelectronics)
Creation of thin films by vaporizing the film substance and allowing its deposition onto a substrate through mask openings.

Vacuum Tube (A/V, communications)
Electron tube evacuated to such a degree that its electrical characteristics are essentially unaffected by any residual gas or vapor. According to function, vacuum tubes are classified as: receiving tubes, transmitting tubes, phototubes, cathode-ray tubes, microwave tubes, storage tubes. Structurally, they are classified according to their number of electrodes as: diodes, triodes, tetrodes, pentodes, etc.

Valence Band (microelectronics)
Highest electronic energy band in a semiconductor or insulator which can be filled with electrons. The electrons in the valence band correspond to the valence electrons of the constituent atoms. In a semiconductor or insulator, at sufficiently low temperatures, the valence band is completely filled and the conduction band is empty of electrons.

Value-Added Network (communications)
Communications network that provides services beyond normal transmission, such as automatic error detection and correction, protocol conversion and message storing and forwarding. Telenet and Tymnet are examples of value-added networks.

VAR (communications, computer)
Value Added Reseller - an organization that adds value to a system and resells it. For example, a VAR could purchase a computer and peripherals from different vendors and a graphics software package from another vendor and package it as a specialized system.

Varactor (microelectronics)
Semiconductor diode designed to maximize the variation of its capacitance with applied reverse bias voltage. Such diodes are also often called variable capacitance diodes. Today, they are almost exclusively junction diodes. Since varactor diodes are primarily used in parametric amplifiers and subharmonic generators, it has become customary to rate varactors by a so-called cutoff frequency. This is defined as the frequency at which the Q of the diode, under the condition of zero dc bias, drops to unity.

Variable (computer)
Name representing or substituting for a number (numeric variable), letter, or combination of letters (string variable).

Variable Area Track (A/V)
In audio/visual production, an optical sound track on film. It modulates the light of the exciter lamp through various shapes of translucent areas so that, when received by the photoelectric cell, the light variations produce identical variations in electrical current.

Varistor (computer/microelectronics)
Two-electrode semiconductor device with a voltage-dependent nonlinear resistance which falls significantly as the voltage is increased. Any variable resistor whose resistance depends upon voltage, current, or polarity.

VCR (A/V – Video Cassette Recorder)
Videotape recording and playback machine that comes in several formats. Although VCRs are analog recording machines, they are used to back up computer files and can store digital data with a special adapter.

VDI (computer)
Virtual Device Interface - an ANSI standard format for creating device drivers. For example, if a vendor sells a screen display and adapter board with a proprietary resolution, and also includes a driver written in the VDI format, software packages that support VDI will be able to use the new monitor. The VDI standard has been included into the CGI (Computer Graphics Interface) standard. When CGI is officially endorsed by ANSI, it may supersede VDI.

Vector (computer)
In computer graphics, a line designated by its end points (x-y or x-y-z coordinates). When a circle is drawn, it is made up of many small vectors. Windows meta files (WMF), Micrographx Designer/ Draw files (DRW), and CorelDRAW! files (CDR) contain vector based image data.

Vectored Interrupt (computer)
Interrupt system in which each interrupt can be immediately serviced without having to determine which has occurred by polling.

Vector Font (computer)
Series of dots connected by lines that can be scaled to different sizes. Plotters, typically, use vector fonts (also known as stroke font).

Vector Graphics (computer)
In computer graphics, a technique for representing a picture as points, lines, and other geometric entities (contrast with Raster Graphics).

Vector Key Light Position (A/V)
In audio/visual production, the relative distance of the key light from the studio floor, specifically with respect to whether it is above or below the eye level of the performer: not to be confused with high and low key lighting which refers to the brightness and contrast for the overall scene.

Vector Line (A/V)
In audio/visual production the dominant direction that is established by two people facing each other or through a prominent movement in a specific direction.

Vectorscope (A/V)
In audio/visual terms, a specialized oscilloscope used to monitor hue and color saturation in television signals (output of cameras, output of camera control units, etc.).

Vendor Independence (communications, computer)
Term used to describe one of the four fundamental principals of the Universal Communications System; that of vendor independence for the client, the end-user of the system. Basically, vendor independence means that the client or the end user is not controlled, confined, or restricted to any one vendor's methodology, or technique, or architecture, or implementation; that the system will support or enhance any vendor's equipment, or service, or support;; with the client always having the option of changing a vendor at any time without penalty or risk of communications failure.

Velocity (A/V, music, M/M)
Portion of a MIDI Note On message indicating the rate at which the key of the keyboard was depressed. The volume of the resulting sound is controlled by the velocity data.

Vertical Blanking Interval (A/V)
In audio/visual terms, the blanking portion of the beginning of each video field of information; it contains the equalizing pulses, the vertical sync pulses.

Vertical Refresh (A/V, computer)
Number of times an entire display screen is refreshed in one second. The typical frequency for a computer screen is around 70Hz (70 times per second). A TV is refreshed 60 half-frames per second (interlaced) resulting in 30 full frames per second.

Vertical Sync (A/V)
In audio/visual, the synchronizing pulses that control the vertical scanning of the video signal and that are used to define the end of on field of video information and the start of the next. In the NTSC system, vertical sync has a frequency of 59.94 Hz.

VESA (A/V, computer)
Video Electronic Standards Association - a group of manufacturers and software developers who create standards for graphic and video display adapter cards.

VHF (communications)
Very High Frequency - a range of electromagnetic frequencies from 30 MHz to 300 MHz.

VHS (A/V)
Predominate recording format for videocassette recorders. VHS was developed by Japan Victor Company (JVC) and introduced to the U.S. market in 1975. A version of VHS, called VHS-Compact or VHS-C, is used in some camcorders.

VHS-C (A/V)
Type of VHS format using 1/2 inch video tape in a mini-cassette; for use mostly in VHS-C camcorders. A full size VHS adapter must be used to playback on VHS VCRs.

Via (computer/microelectronics)
In microelectronic fabrication, a vertical conductor or conductive path formatting the interconnection between multi-layer hybrid circuit layers.

Vibrato (A/V, music, M/M)
Musical term indicating rapid, small changes in the pitch of a played note.

Video (A/V, computer)
Audio/visual playback and recording technology used in the TV industry. It also refers to computer screens and terminals. There is only one TV/video standard in the U.S., however, there are dozens of computer/video display standards. It also known as the picture portion of a telecast. It can also mean the non-broadcast production activities and use of inexpensive equipment for a variety of purposes. Usually the equipment includes a portable camera, a microphone, a videotape recorder (videocassette), and a monitor.

Video Amplifier (A/V, communications)
Low-pass amplifier having a bandwidth in the range from 2 MHz to 100 MHz. Typical applications are in television receivers, cathode-ray-tube video terminals, and pulse amplifiers. The function of a video amplifier is to amplify a signal containing high-frequency components without introducing distortion. Modern video amplifiers use specially designed integrated circuits. The use of integrated video amplifiers minimizes cost and space. With one chip and an external resistor to control the voltage gain, it is possible to make a video amplifier with a bandwidth between 50 and 100 MHz, having voltage gains ranging from 20 to 500 volts.

Video Camera (A/V)
Camera that takes continuous pictures and generates a signal for display or recording. It captures images by breaking down the image into a series of lines. Each line is scanned one at a time, and the continuously varying intensities of red, green, and blue light across the line are filtered out and converted into a variable signal. The standard signal of 525 scan lines used in the U.S. and Canada is governed by the NTSC.

Video Cassette (A/V)
Plastic container in which a videotape moves from supply to takeup reel, recording and playing back videotaped programming through a video cassette recorder: similar in construction and function to an audio cassette recorder.

Video Codec (A/V, computer)
Circuit that converts NTSC video into digital code and vice versa. It incorporates a compression technique to reduce the data and may or may not provide full-motion video. For full motion, real-time, full screen quality color the codec output is approximately 45 megabits/second. Some of the Codec vendors include: AT&T, CLI, PictureTel, V-tel.

Video Conferencing (communications)
Communications system used for the simultaneous exchange of real-time, full motion, color video and associated audio. A complete video conferencing communication system involves three basic elements: (1) terminal equipment (cameras, displays, microphones, speakerphones) that transform both the audio and visual inputs into electrical signals, and vice-versa; (2) transmission facilities to carry the electrical signals over large distances; (3) switching systems to allow a choice of devices, or terminals, to be connected. The limiting factor for wide-scale video conferencing is expense relating to the wide bandwidth required to transmit a high quality video signal, especially at will (at any time that the users wish to engage in video conferencing). There are only two ways to reduce the transmission facility costs: (1) reduce the bandwidth required to handle high-quality video signals by sacrificing resolution, screen size, and motion rendition; (2) reduce the bandwidth required by taking advantage of the redundancy present in video frames per second by introducing very high ratio, video compression techniques. In terms of the physical transmission/reception medium, fiber optic cabling provides the only realistic point-to-point medium that can handle the speeds and capacities required. For satellite communications linkage, their is a major investment required at both ends of the conference link, that will handle both send and receive capabilities of real-time, full-motion, full-color, full-screen, high quality communications. For satellite linkages that require more than a single up-and-down link, their are numerous problems encountered with signal delay simply due to the limitations of transmission speeds over distance. Each satellite up-link is about 22,000 miles each way, times however many links there are, including any repeater requirements (again, bandwidth requirements are significant.)

Video Disc Recording (A/V, computer)
Disk system used to reproduce television pictures and sound. The reproduction system consists of three parts: disk, disk player, and television receiver. The disk player rotates the disk (whole information density is several hundred times that of conventional audio/visual long playing device), at high speed and reads the recorded signal by a sensor. The signal can be seen on the picture tube or heard from the loudspeaker of the television receiver. On example of video disk technology, VHD (video high density) includes a recording system that employs a smooth, flat glass disk coated with photosensitive material. Minute laser beams irradiate the disk while it rotates at a speed of 900 revolutions per minute. The source of beams is moved radially at a constant speed. A laser beam is first split in two, one half for modulation of video and audio signals, the other for modulation of tracking signals. Fine pits are recorded spirally on the glass disk. A metallic master disk is produced from the original glass disk. Master disks, which have indented pits, are made from the metallic master. Then stamper disks are produced from each Master. Each stamper, with its extended pits, produces approximately the same number of final disks as the typical audio stamper. The VLP (video long play system) is essentially an optical system using lasers for recording/reproduction. This system is grooveless, has no stylus, has special features such as still, slow, quick motion, random access, and has two audio channels.

Video Display Board (A/V, computer)
Printed circuit board that plugs into a personal computer and generates text and graphics on a monitor's display screen. Also called a display adapter or graphics adapter, it is responsible for resolution quality and the number of colors that can appear on screen. It converts characters or graphic patterns (bit map) within a reserved segment of computer memory into signals that are used to refresh the display screen. In digital display systems, the video display board generates digital signals for the monitor. The monitor then does the conversion from digital to analog. In analog systems, the video display board does the digital to analog conversion and sends analog signals to the monitor. The monitor must be capable of handling the frequency range of the display board (number of lines per second). Multisync monitors can accept a range of frequencies and work with more than one type of display standard.

Videodisc (A/V, computer)
Older style read-only optical disc that holds up to 2 hours of video data. Like a phonograph record and CD player, most videodisc players provided direct access to any location on disc. Video discs have not done well and are now out of production. Videodiscs were analog like Video Tape.

Video Dubbing (A/V)
In audio/visual production, features on some videocassette recorders that were added after the advent of the advanced rotary flying erase head technology that allows a user to, very cleanly, replace a segment of video tape with a new segment, without any lines of color bar distortion moving down the picture (moiré line). This feature along with the audio dubbing capability are important features for people to look for when buying a camcorder.

Videographer (A/V)
Popularized new term for a person who uses mostly portable video equipment, such as a camcorder, to take shots of objects, or events, especially as an occupation.

Videography (A/V)
Popularized new term for the art or process of producing stories or images of objects using portable video equipment such as a camcorder.

Video In A Window (A/V, computer, M/M)
Type of full motion video adapter card accepting video signals and displaying the resulting image in a sizable window on a display under DOS or Windows. These cards are often identified by the first initials of each word: "VIW".

Video Leader (A/V)
In audio/visual production, visual and aural material that precedes any color videotape recording (also called academy leader). The SMPTE (Society of Motion Pictures and Television Engineers) prescribes for the standard video portion blank tape for threading: 10 seconds of color bars; 15 seconds of slate information; 8 seconds of numbers or black; 2 seconds of black ahead of the program information.

Video RAM (computer)
Specially designed memory that is used to hold and transfer an image onto the video screen. The video RAM contains a certain amount of processing logic that converts the pixel data onto the screen in the required format.

Videotape (A/V)
Acetate (plastic) iron-oxide coated (dull side) tape of various width for recording of video and audio signals, as well as additional technical code information.

Videotape Recorder (A/V)
Also called a VTR, the electronic recording device that records and stores on videotape, the video and audio signals for later playback or postproduction editing.

Videotext (A/V, communications, computer)
Computer communications services that have not yet gained widespread appeal that take advantage of standard television receivers and use them as display terminals to retrieve information from data bases. A "black box" (usually rented) is placed between the television set and the signal carrier. The signal carrier may be a telephone network, a data communications network, a television cable, or a broadcast signal. The black box (essentially a high-speed computer with storage) receives data from the signal carrier; it stores the downloaded information; it formats that data into a signal suitable for display on the television set. The user then interacts with the black box (and the stored program that is now within its memory) to determine what information is actually displayed on the screen of the television set (usually a time delay before the stored program is erased).

Video Track (A/V)
In audio/visual terms, the area of the videotape used for recording information.

Viewfinder (A/V)
Generally, the electronic viewfinder (in contrast to the optical viewfinder in a film or still camera): it is actually a small television set that displays the picture as generated by the camera, and it may be a black & white, or a color version.

VIRS (A/V)
In audio/visual terms, the Vertical Interval Reference Signal: a signal that may be included during the vertical blanking interval to allow TV receivers to obtain a color and luminance reference from the transmitting station (European specifications).

Virus (computer & communications)
Program that is used to infect a computer. After the virus code is written, it is buried within an existing program. Once that program is executed, the virus code is also activated and it attaches copies of itself to other programs in the system.

Virtual Memory (computer/Windows)
Most large programs are too long to fit into the space in main memory that can be allocated to them at run time. In a single user system this will be true when the amount of space required by the program is greater than the total memory available. In a multi- programming system it may be true because the amount of space that is needed is more than the operating system is willing to allocate to that particular program. In either case it becomes necessary to break the program up into sections, segments, or overlays so that the entire program need not be in main memory at the same time. The term virtual memory (also virtual storage) denotes the memory of a virtual (i.e. simulated) computer. In Windows Networking, space on a hard disk is used as if it were physical memory. Windows Networking does this through the use of swap files. The benefit of using virtual memory is that you can run more applications at one time than the system's physical memory would otherwise allow. The drawbacks are the disk space required for the virtual-memory swap file, and the decreased execution speed when swapping is required.

Virtual Printer Memory (computer/Windows)
In a PostScript printer, a part of memory that stores font information. The memory in Postscript printers is divided into banded memory and virtual memory. The banded memory contains graphics and page-layout information needed to print documents. The virtual memory contains any font information that is sent to the printer, either when printing a document, or when downloading printer fonts.

Virtual Reality (A/V, computer, M/M)
Computer interface that places the user in an artificial world. Virtual reality programs detect the user's actions and instantly change the user's perceptions as a result. The input and output devices involved, provide enough sensory feedback to the user to allow participation to be experienced as if the artificial were real.

Virtual Circuit (communications)
Packet-switching service in which a connection (virtual circuit) is established between two stations at the start of transmission. All packets follow the same route, need not carry a complete header address, and all packets arrive in exact sequence, during the session.

VISCA (A/V, computer, M/M)
Video System Control Architecture - a control protocol developed by Sony Corporation for its V-series, computer-controllable video products (i.e. Vbox or Vdeck). The VISCA protocol shares a common heritage with MIDI short SysEx (system exclusive) messages.

Visualization (A/V)
In audio/visual production, mentally converting a scene into a number of key television images: at this time the images do not need to be sequenced in any production order.

Visualization Technology (A/V, computer, M/M)
Term that is used to describe the recent development in computer engineering that uses shape, location in space, brightness, color, and motion to create and manipulate sophisticated graphics representing complex mathematic formulation.

VITS (A/V)
In audio/visual, the Vertical Interval Reference Signal: a signal that may be included during the vertical blanking interval to allow TV receivers to obtain a color and luminance reference from the transmitting station (European specification).

VLSI (communications, computer)
Very Large Scale Integration - refers to the very large number of electronic transistors and other components that are built onto a single chip. VLSI is in the range of approximately 100,000 to 1,000,000 components per chip (next higher density is ELSI).

VMP (computer)
File extension for 16-bit graphic images created or reproduced by many of the video cards that use the Chips & Technologies chipsets.

Voice Coil (communications, computer)
Type of motor that is used to move the access arm of a disk drive in very small increments. Like the voice coil of a speaker, the amount of current determines the amount of movement. Contrast with stepper motor, which works in fixed increments.

Voice Grade (communications)
Refers to bandwidth required to transmit human voice which is usually about 4,000 Hz.

Voice Mail (communications)
Computerized voice store and forward system (like a telephone answering system) that digitizes incoming voice messages and stores them on disk. Voice mail usually provides auto attendant capability, which uses prerecorded messages to route the caller to the appropriate person, department, or mail box.

Voice Messaging (communications)
Use of voice mail as an alternative to electronic mail, in which voice messages are intentionally recorded, not because the recipient was not available.

Voice-Over (A/V)
In audio/visual production, the narration delivered in conjunction with visuals, in which the person delivering the narration is not seen in the story, or picture.

Voice Processing (communications, computer)
Computerized handling of voice, which includes voice store and forward, voice response, voice recognition, and text to speech technologies.

Voice Recognition (communications, computer)
Conversion of spoken words into computer text. Speech is first digitized and then matched against a dictionary of coded waveforms. The matches are converted into text as if the words were typed on the keyboard. Speaker-dependent systems must be trained before using, by taking samples of actual words from the person who will use it. Speaker-independent systems can recognize limited vocabularies such as numeric digits and a handful of words. In the telephone companies, these systems are beginning to replace the human operator for services, such as collect and credit card calls, for example. In the future, voice recognition systems will be able to understand large vocabularies.

Voice Response (communications, computer)
Generation of voice output by the computer. At the present time widespread use of this technology provides pre-recorded information either with or without selection by the caller. Interactive voice response allows interactive manipulation of a database.

Voice Store and Forward (communications, computer)
Technology behind voice mail and messaging systems. Human voice is digitized, stored in the computer, possibly forwarded to another mail box, and retrieved.

Volatile Memory (computer)
Memory that does not hold its contents without power. A computer's main memory, made up of dynamic RAM or static RAM chips, loses its content upon loss of power.

Volt-ohm-milliammeter (A/V, communications)
Self-contained test instrument for measuring a wide range of voltages (both ac and dc), resistances, and current (usually dc only), for radio, TV, and electronic servicing. All readings are obtained on a single multiscale indicating instrument. The selection of the correct ranges and function is accomplished either by means of one or two rotary switches, by multiple pin jacks, or by a combination of both. Instrument sensitivity for dc-voltage measurements is usually from 100 to 100,000: for ac-voltage measurement for sensitivity ranges from 1,000 to 20,000 ohms per volt. Accuracy is usually about 3% for dc and 5% for ac measurements. The terms multimeter and analyzer (or circuit analyzer) are quite commonly used as synonyms for volt-ohm-milliammeter.

Voltage Amplifier (A/V, communications)
Electronic amplifier that produces, with minimum distortion, an output voltage greater in magnitude than the input voltage. They are built to amplify signals with frequency components in the range from zero hertz to thousands of megahertz. To cover this frequency range, several different types of amplifiers are required. An amplifier which cannot amplify voltage signals with zero frequency components (dc) is called RC-coupled. If zero frequency components (dc) are amplified, the amplifier is known as dc or direct-coupled. In the range from a few hertz to 30 kHz, amplifiers are classified as audio. In the frequency range up to 10 MHz for use in television, pulse circuits, and electronic instruments, amplifiers are know as video. For the radio-frequency range from a few hundred kilohertz to hundreds of megahertz, tuned amplifiers are normally used. At ultrahigh frequencies, amplifiers designed around special circuits are employed.

Voltage Measurement (A/V, communications)
Determination of the difference in electrostatic potential between two points: it is accomplished by observing reproducible effects caused by the voltage. Many different effects have been utilized in the construction of voltmeters, depending upon whether the voltage produces a direct-current (dc) or an alternating-current (ac) flow, and upon the power available to operate the voltmeter.

Voltage-Multiplier Circuit (A/V, communications)
Rectifier circuit capable of supplying a dc output voltage that is two or more times the peak value of the ac input voltage. Such circuits are especially useful for high-voltage, low-current supplies. These supplies are usually lighter in weight, smaller in size, and less expensive that the more usual half-wave and full-wave rectifier supplies.

Voltage Regulator (A/V, communications, computer)
Device or circuit that maintains a load voltage nearly constant over a range of variations of input voltage and load current. Voltage regulators are used wherever the unregulated voltage would vary more than can be tolerated by the electrical equipment using the voltage. Alternating-current (ac) distribution feeders use voltage regulators to keep the voltage supplied to the user within a prescribed rage. Electronic equipment has voltage regulators in direct-current (dc) power supplies.

Voltage Regulator Tube (A/V, communications)
Gaseous glow-discharge tube operating in the normal-glow region and therefore possessing an almost constant anode-to-cathode voltage drop. The purpose of these tubes is to provide a substantially constant dc voltage from a fluctuating dc source.

Voltmeter (A/V, communications)
Instrument for the measurement in volts of potential difference between two points. Derivatives of the voltmeter are the microvoltmeter, millivoltmeter, and kilovoltmeter. Voltmeters are connected between points of a circuit, between which the potential difference is to be measured.

Volume (computer)
In computer terminology, a physical storage unit; or logical, within several disk drives.

Volume Control Systems (A/V, communications)
Electronic systems that regulate the signal amplification or limit the output of circuits. Examples are volume compressors, limiters, and expanders. Compressors are used to reduce the volume range in sound motion picture, and phonograph recording; sound broadcasting, public address, and sound reinforcing systems.

Volume Label (computer/Windows)
Name that identifies a disk. It appears in the tile bar, or the Directory Tree window.

VSAT (communications)
Very Small Aperture satellite Terminal - small earth stations for satellite transmission that can handle from 1 to 30 Mbps - they are usually 1.5 meters diameter and smaller.

V-Series (communications)
CCITT standards for communications (V.21 for asynch 300 bps - to V.120 for DTE's).

VTR (A/V)
Video Tape Recorder - refers to a reel-to-reel device rather than a videocassette recorder.

VU Meter (A/V)
Volume-Unit meter: measures volume units, the relative loudness of amplified sound.