Value-added reseller refers to distributors that also provide other services such as systems integration or network management.
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This is the living glossary of terms related to interactive television development. Most of these terms were graciously donated to OEDN by Vidiom Systems and Time Warner Cable. Browse the list below, search for specific terms, and provide comments to terms to clarify their meanings.
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See value-added reseller (VAR).
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Variable bit rate is a type of telecommunications service characterized by a service bit rate specified by statistically expressed parameters that allow the bit rate to vary within defined limits.
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See vertical blanking interval (VBI).
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See variable bit rate (VBR).
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See Virtual Channel Table (VCT).
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"Very high-speed digital subscriber line that uses existing the copper infrastructure of the telephone companies. VDSL offers video and data transmission rates up to 52 Mbps up to 2,700 feet. See also digital subscriber line (DSL)."
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"Velocity of propagation refers to the velocity of signal transmission. In free space, electromagnetic waves travel with the speed of light. In coaxial cables, this speed is reduced. The velocity of propagation is commonly expressed as percentage of the speed in free space."
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"The vertical blanking interval is the unused lines in each field of a television signal, seen as a thick band when the television picture rolls over. Some of these lines may be used for teletext and captioning, or may contain specialized data. See also teletext."
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Very High Frequency (VHF) refers to channels 2-13?54-88 MHz and 174-216 MHz.
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Very small aperture terminals are small earth stations with a satellite dish usually four to six feet in diameter used to receive high speed data transmissions. VSATs can also transmit slow-speed data. See also earth station.
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"A vestigial sideband transmission is a system of transmission that eliminates a large portion, but not all, of one sideband of an amplitude modulated signal. Vestigial sideband transmissions may be done with either analog or digital modulation. The vestigial sideband can be used to carry new information. For example, the broadcast industry uses vestigial sideband with eight discreet amplitude levels (8-VSB) for modulating standard- and high-definition digital television signals transmitted from a broadcast tower."
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See Very High Frequency (VHF).
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Video generally refers to the bandwidth and spectrum of the signal that results from television scanning and which is used to produce a picture.
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The video band refers to the frequency band used to transmit a composite video signal. See also composite video signal.
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A video tape recorder is a device that allows the recording and playback of magnetic tape sound and picture recordings.
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"Video transmission refers to the original video signal before it is modulated and converted to radio frequency and broadcast or cablecast. A home television set reconverts radio frequencies to a video signal. See also broadcast, cablecasting, and radio frequency (RF)."
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"Video-on-demand allows a subscriber to select movies he or she wishes to view from a large selection of titles and categories stored on a remote server at any time. This service may also provide VCR functionality?stop, pause, etc.?that allows the subscriber to control the play back of the server from the remote control."
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"Videotape is used to electronically record sight and sound for instant playback. Videotape comes in half-inch, three-quarters, one, and two-inch widths and can be erased and re-recorded."
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"Videotex is the generic term used to refer to a two-way interactive system for the delivery of computer-generated data into the home, usually using the television set as a display device. Some of the more often used specific terms are viewdata for telephone-based systems (narrowband interactive systems); wideband broadcast or cabletext for systems using a full video channel for information transmission; and wideband two-way teletext for systems which could be implemented over two-way cable television systems. In addition, hybrids and other transmission technologies, such as satellite, could be used for delivery of videotex services on a national scale."
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"A viewer is the person currently in control of the set-top box. This term may just refer to whoever is holding the remote, but has other implications when viewer profiles are used."
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"A viewer profile allows the viewing experience to be personalized for each viewer. Each viewer may have personal favorite channels and certain other settings. Some features, such as parental controls, may be extended to allow a personal viewing and purchasing PIN for each viewer."
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"Viewer session refers to all set-top box viewer activities between the start of a session and the end of a session. These events may be different, depending on whether individual viewer profiles are provided. "
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"Viewers per viewing household (VPVH) is a demographic percentage that indicates how many persons per 100 or per 1000 households are viewing. For example, a VPVH of 80 K2-11 means that for every 100 households viewing, there are an estimated 80 children ages 2 to 11."
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A V-chip is a microchip that permits parental control over rated television programs.
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A virtual channel is the communication channel that provides for the sequential unidirectional transport of ATM cells.
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"The Virtual Channel Table is broadcast by the head-end and read by the tuner manager during the boot process. The VCT is defined by the Advanced Television Systems Committee (ATSC). Basically, the VCT contains a transport stream identifier, the channel number, the short channel name, the carrier frequency, the program number, the access controlled flag, the location field for extended text messages, and the service type."
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Virtual circuit refers to a predefined path through a network that provides a connection-oriented session between two applications.
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"A virtual machine is an operating environment working with, yet independent of a host operating system. Used in such applications as a middleware component of a set-top box, virtual machines accommodate proprietary philosophies of associated software and service vendors. "
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"A virtual private network (VPN) is a portion of a public network that has been logically partitioned for private use. It is a type of technology designed to increase the security of information transferred over the Internet. VPN can work with either wired or wireless networks, as well as with dial-up connections over Plain Old Telephone Service (POTS). VPN creates a private encrypted tunnel from the end user?s computer, through the local wireless network, through the Internet, all the way to the corporate servers and database. "
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See video-on-demand (VOD).
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Voice-over-internet protocol (VoIP) services are a provision of voice telephony via the use of packet-switched networks running Internet Protocol (IP) networks rather than traditional circuit switching. VoIP can be less expensive than voice transmission using standard analog packets over Plain Old Telephone Service (POTS).
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Voice-Over-Net refers to various sets of technologies that are used to enable voice applications across the Internet.
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See voice-over-internet protocol (VoIP).
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See Voice-Over-Net (VON).
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See virtual private network (VPN).
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See viewers per viewing household (VPVH).
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See very small aperture terminal (VSAT).
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VSB-8 is vestigial sideband modulation with 8 discrete amplitude levels.
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See video tape recorder (VTR).
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