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A set-top box (STB) or set-top unit (STU) (one type also colloquially known as a cable box) is an information appliance device that generally contains a TV-tuner input and displays output to a television set and an external source of signal, turning the source signal into content in a form that can then be displayed on the television screen or other display device. They are used in cable television, satellite television, and over-the-air television systems, as well as other uses.
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Electronic program guide
Electronic program guides and interactive program guides provide users of television, radio, and other media applications with continuously updated menus displaying broadcast programming or scheduling information for current and upcoming programming. Some guides, such as ITV, also feature backward scrolling to promote their catch-up content.
Favorites
This feature allows the user to choose preferred channels, making them easier and quicker to access; this is handy with the wide range of digital channels on offer. The concept of favourite channels is superficially similar to that of the "bookmark" function offered in many Web browsers.
Timer
The timer allows the user to program and enable the box to switch between channels at certain times: this is handy to record from more than one channel while the user is out. The user still needs to program the VCR or DVD recorder.
Scart link recording
The user having selected the required TV programs on the electronic program guide at the appropriate time, the box sends a control signal via the Scart link telling a compatible VCR or DVR to start or stop recording. This means the user has only to program the set-top box and it will switch to the right channel at the right time and "wake up" the VCR or DVR to record, so there is no need for a timer.
Controls on the box
Some models have controls on the box, as well as on the remote control. This is useful should the user lose the remote or if the batteries age.
Remote controls that work with other TVs
Some remote controls can also control some basic functions of various brands of TVs. This allows the user to use just one remote to turn the TV on and off, adjust volume, or switch between digital and analog TV channels or between terrestrial and internet channels.
Parental locks
The parental lock or content filters allow users over 18 years old to block access to channels that are not appropriate for children, using a personal identification number. Some boxes simply block all channels, while others allow the user to restrict access to chosen channels not suitable for children below certain ages.
Software alternatives
As complexity and potential programming faults of the set-top box increase, software such as MythTV, Select-TV and Microsoft's Media Center have developed features comparable to those of set-top boxes, ranging from basic DVR-like functionality to DVD copying, home automation, and housewide music or video playback.
Firmware update features
Almost all modern set-top boxes feature automatic firmware update processes. The firmware update is typically provided by the service provider.
Ambiguities in the definition
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, possibly helping the adoption of the term digibox. Additionally, newer set-top boxes that sit at the edge of IP-based distribution networks are often called net-top boxes or NTBs, to differentiate between IP and RF inputs. The Roku LT is around the size of a pack of cards and delivers Smart TV to conventional sets.
The distinction between external tuner or demodulator boxes (traditionally considered to be "set-top boxes") and storage devices (such as VCR, DVD, or disc-based PVR units) is also blurred by the increasing deployment of satellite and cable tuner boxes with hard disk, network or USB interfaces built-in.
Devices with the capabilities of computer terminals, such as the WebTV thin client, also fall into the grey area that could invite the term "NTB".
Europe
In Europe, a set-top box does not necessarily contain a tuner of its own. A box connected to a television (or VCR) SCART connector is fed with the baseband television signal from the set's tuner, and can have the television display the returned processed signal instead.
This SCART feature had been used for connection to analogue decoding equipment by pay TV operators in Europe, and in the past was used for connection to teletext equipment before the decoders became built-in. The outgoing signal could be of the same nature as the incoming signal, or RGB component video, or even an "insert" over the original signal, due to the "fast switching" feature of SCART.
In case of analogue pay-TV, this approach avoided the need for a second remote control. The use of digital television signals in more modern pay-TV schemes requires that decoding take place before the digital-to-analogue conversion step, rendering the video outputs of an analogue SCART connector no longer suitable for interconnection to decryption hardware. Standards such as DVB's Common Interface and ATSC's CableCARD therefore use a PCMCIA-like card inserted as part of the digital signal path as their alternative to a tuner-equipped set-top box.
Energy use
In June 2011 a report from the American National Resources Defense Council brought attention to the energy efficiency of set-top boxes, and the US Department of Energy announced plans to consider the adoption of energy efficiency standards for set-top boxes. In November 2011, the National Cable & Telecommunications Association announced a new energy efficiency initiative that commits the largest American cable operators to the purchase of set-top boxes that meet Energy Star standards and the development of sleep modes that will use less energy when the set-top box is not being used to watch or record video.