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Set-top box
From Wikipedia, the free encyclopedia
A set-top box (STB) or set-top unit (STU) is a device that connects to a television and an external source of signal, turning the signal into content which is then displayed on the television screen.
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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. Nowadays, cable converter boxes are used to descramble premium cable channels and to receive digital cable channels.
The signal source might be an ethernet cable , 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.
With the advent of flat panel televisions set-top boxes are now deeper in profile than the tops of most modern TV sets. Because of this set-top boxes are often placed beneath televisions and the term set-top box has become something of a misnomer.
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 approach avoids the need for a second remote control.
Special digital set-top boxes are available for receiving digital television broadcasts on TV sets that 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 (or IRD).
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.
In Australia set-top boxes are the principal means of receiving digital terrestrial broadcasts as comparably few television sets have in-built digital tuners. The Foxtel set-top boxes (including the Foxtel iQ unit) are also used to receive subscription television from Foxtel.
Globally, some boxes also have a built-in digital video recorder (or DVR) which often utilises the electronic programme guide scheduling data and records content to an internal hard drive.
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 which eliminates the need for any coaxial cabling.
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