A set-top box (STB) or set-top unit (STU) is an information appliance device that generally contains a tuner and connects to a television set and an external source of signal, turning the signal into content which is then displayed on the television screen or other display device. Set-top boxes are used in cable television and satellite television systems, to transform the signal from the cable or satellite to a form that can be used by the television set or other receiver.
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Before the mid-1950s, all British television sets tuned only VHF Band I channels. Since all 5 Band I channels were occupied by BBC transmissions, ITV would have to use Band III. This meant all the TV sets in the country would require Band III converters which converted the Band III signal to a Band I signal. By 1955, when the first ITV stations started transmitting, virtually all new British Televisions had 13-channel tuners, quickly making Band III converters obsolete.
Before the All-Channel Receiver Act of 1962 required US television receivers to be able to tune the entire VHF and UHF range (which in North America was NTSC-M channels 2 through 83 on 54 to 890 MHz), a set-top box known as a UHF converter would be installed at the receiver to shift a portion of the UHF-TV spectrum onto low-VHF channels for viewing. As some 1960s-era twelve-channel TV sets remained in use for many years, and Canada and Mexico were slower than the US to require UHF tuners to be factory-installed in new TV's, a market for these converters continued to exist for much of the 1970s.
Cable television represented a possible alternative to deployment of UHF converters as broadcasts could be frequency-shifted to VHF channels at the cable head-end instead of the final viewing location. Unfortunately, cable brought a new problem; most cable systems could not accommodate the full 54-890 MHz VHF/UHF frequency range and the twelve channels of VHF space were quickly exhausted on most systems. Adding any additional channels therefore needed to be done by inserting the extra signals into cable systems on non-standard frequencies, typically either below VHF channel 7 (midband) or directly above VHF channel 13 (superband).
These frequencies corresponded to non-television services (such as two-way radio) over-the-air and were therefore not on standard TV receivers. Before cable-ready TV sets became common in the late 1980s, a set-top box known as a cable converter box was needed to receive the additional analog cable TV channels and convert them to analog video frequencies that could be seen on a regular TV set. These boxes often provided a wired or wireless remote control which could be used to shift one selected channel to a low-VHF frequency (most often channels 3 or 4) for viewing. Block conversion of the entire affected frequency band onto UHF, while less common, was used by some models to provide full VCR compatibility and the ability to drive multiple TV sets, albeit with a somewhat non-standard channel numbering scheme.
Newer television receivers greatly reduced the need for external set-top boxes, although cable converter boxes continue to be used to descramble premium cable channels and to receive digital cable channels, along with using interactive services like video on demand, pay per view, and home shopping through television. Satellite and microwave-based services also require specific external receiver hardware, so the use of set-top boxes of various formats never completely disappeared.
A cable converter box or television converter box is type of set-top box that is an electronic tuning device that transposes/converts any of the available channels from a cable television service to an analog RF signal on a single channel, usually VHF channel 3 or 4. The device allows a television set that is not “cable ready” to receive cable channels. While later televisions were "cable ready" with a standard converter built-in, the existence of premium television (aka pay per view) and the advent of digital cable have continued the need for various forms of these devices for cable television reception. While not an explicit part of signal conversion, many cable converter boxes include forms of descrambling to manage carrier-controlled access restriction to various channels.
Professional set-top boxes are referred to as IRDs or integrated receiver/decoders in the professional broadcast audio/video industry. They are designed for more robust field handling and rack mounting environments, and are also technically superior, IRDs have the distinct feature of outputting uncompressed SDI signals, unlike consumer STBs which don’t mostly because of copyright reasons.
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 video games, or other possibilities.
In the late 2000s, there has been a significant growth in the adoption of Hybrid IPTV Set-Top Boxes in both the pay-TV and free-to-air set-top box markets. A hybrid set-top allows traditional TV broadcast (from terrestrial, satellite, or cable providers) to be brought together with video delivered over the Internet, and with personal multimedia content. This enables television viewers to access a greater variety of content on their TV sets, without needing a separate box for each service.
Hybrid IPTV Set-Top Boxes also enable consumers to access a range of advanced interactive services, such as VOD and time-shifting TV, as well as internet applications, including video telephony, surveillance, gaming, shopping, e-government accessed via a television set.
For a pay-TV operator’s perspective, a Hybrid IPTV Set-Top Box gives them greater long term flexibility by enabling them to deploy a wide variety new services and applications as and when consumers require, most often without the need to upgrade equipment or for an engineer to visit and reconfigure or swap out the device. This minimises the cost of launching new services, increases speed to market and limits disruption for consumers.[1]
One of the leaders in the Hybrid IPTV Set-Top Box market is Advanced Digital Broadcast (ADB) – having launched its first hybrid digital terrestrial (DTT) /IPTV set-top box in 2005[2] that provided Telefónica with the digital TV platform for its Imagenio service at the end of that year.[3] In 2009, the company also provided Europe’s first three-way hybrid digital TV platform to Polish digital satellite operator n that enables its subscribers to view content delivered via satellite, digital terrestrial, and IP networks.[4]
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. IP set-top boxes have a built in home network interface which can be Ethernet or one of the existing wire home networking technologies such as HomePNA or the ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 Gigabit/s) Local area network using existing home wiring (power lines, phone lines, and coaxial cables).[5]
In the US and Europe, telephone companies use IPTV (often on ADSL or optical fiber networks) as a means to compete with traditional local cable television monopolies.
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. This is to differentiate between devices with IP or RF inputs.
In Europe, 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.
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, thanks 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.
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 discs, network or USB interfaces built-in.
Devices with computer terminal-like capabilities, such as the WebTV thin client, also fall into the grey area that could be catered for by the term NTB.
Set-top boxes were also made to enable closed captioning on older sets in North America, before this became a mandated inclusion in new TV sets. Some have also been produced to mute the audio (or replace it with noise) when profanity is detected in the captioning, where the offensive word is also blocked. Some also include a V-chip that allows only programmes of some television content ratings. A function that limits children's time watching TV or playing video games may also be built in, though some of these work on the mains electricity rather than the video signal.
As complexity of the set-top box increases, the software quality practices of the industry become obvious and many systems have bugs.[6] However, users of software-based solutions such as Windows Vista's Media Center, MythTV and Select-TV have a very flexible list of possible features ranging from basic Digital video recorder (DVR)-like functionality to features such as DVD copying, home automation, and house-wide music/video file playing.
In 2011, set-top boxes received attention for their energy consumption. The average set-top box configuration (one HD-DVR and one HD cable box) uses 446 kWh per year—more than a new 21 cubic foot Energy Star refrigerator, which uses 415 kWh a year.[7] Currently, there are no federal appliance standards in place to regulate the energy efficiency of set-top boxes, though in June 2011 the U.S. Department of Energy announced plans to include them in future regulations.[8]
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