Set-top box
From Wikipedia, the free encyclopedia
The term set-top box (STB) describes a device that connects to a television and some external source of signal, and turns the signal into content then displayed on the screen.
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[edit] History
Before cable-ready TV sets, a set-top box known as a cable converter box was used to receive analog cable TV channels and convert them to video that could be seen on a regular TV (channel 3 or 4 in North America, or channel 36 or 37 in the United Kingdom). Nowadays, cable converter boxes are used to descramble premium cable channels and to receive digital cable channels.
[edit] Many TV signal sources
The signal source might be an ethernet cable (see triple play), a satellite dish, a coaxial cable (see cable television), a telephone line (including DSL connections), Broadband over Power Line, or even an ordinary VHF or UHF antenna. Content, in this context, could mean any or all of video, audio, Internet webpages, interactive games, or other possibilities.
[edit] Ambigutites in the definition
A set-top box does not necessarily contain a tuner of its own. A box connected to a television (or VCR) set's SCART connector is fed with the baseband television signal from the set's tuner, and can ask the television to display the returned processed signal instead.
- The SCART feature is used for decoding Pay TV in Europe, and in the past was used for decoding teletext, before decoders became built-in.
The outgoing signal can be of the same nature as the incoming signal, or RGB component video, or even an "insert" over the original signal, thanks to the "fast switching" feature of SCART. In case of Pay TV, this solution avoids the hassles associated with having a second remote control.
[edit] Digital television
In the United Kingdom, digital set-top boxes (often referred to as digiboxes, after Sky Digital's trademark for their unit) are usually for digital terrestrial television through services such as Freeview, a service operated by the Freeview Consortium, or through digital satellite with BSkyB and also with digital cable. They are used to access television as well as audio and interactive services through the "Red Button" promoted by broadcasters such as the BBC with BBCi or Sky with Sky Active.
Special digital set-top box are available for receiving digital TV broadcasts on TV sets do not have a built in digital tuner. In the case of direct broadcast satellite (mini-dish) systems such as SES Astra, Dish Network, or DirecTV, the set-top box is an integrated receiver/decoder (IRD).
In IPTV networks, the set-top box is a small computer providing two-way communications on an IP network, and decoding the video streaming media.
[edit] See also
Related Technolies
