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Digital television

Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high-definition television (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio (commonly 16:9) in contrast to the narrower format (4:3) of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in the same bandwidth as a single analog channel, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:
 * Digital Video Broadcasting (DVB) uses coded orthogonal frequency-division multiplexing (OFDM) modulation and supports hierarchical transmission. This standard has been adopted in Europe, Africa, Asia, and Australia, for a total of approximately 60 countries.
 * Advanced Television System Committee (ATSC) standard uses eight-level vestigial sideband (8VSB) for terrestrial broadcasting. This standard has been adopted by 9 countries: the United States, Canada, Mexico, South Korea, Bahamas, Jamaica, the Dominican Republic, Haiti and Suriname.
 * Integrated Services Digital Broadcasting (ISDB) is a system designed to provide good reception to fixed receivers and also portable or mobile receivers. It utilizes OFDM and two-dimensional interleaving. It supports hierarchical transmission of up to three layers and uses MPEG-2 video and Advanced Audio Coding. This standard has been adopted in Japan and the Philippines. ISDB-T International is an adaptation of this standard using H.264/MPEG-4 AVC, which has been adopted in most of South America as well as Botswana and Angola.
 * Digital Terrestrial Multimedia Broadcast (DTMB) adopts time-domain synchronous (TDS) OFDM technology with a pseudo-random signal frame to serve as the guard interval (GI) of the OFDM block and the training symbol. The DTMB standard has been adopted in China, including Hong Kong and Macau.
 * Digital Multimedia Broadcasting (DMB) is a digital radio transmission technology developed in South Korea  as part of the national information technology project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones, laptops and GPS navigation systems.

Background
Digital television's roots are tied to the availability of inexpensive, high performance computers. It was not until the 1990s that digital TV became a real possibility. Digital television was previously not practically feasible due to the impractically high bandwidth requirements of uncompressed video, requiring around 200Mbit/s for a standard-definition television (SDTV) signal, and over 1Gbit/s for high-definition television (HDTV).

Development
In the mid-1980s, Toshiba released a television set with digital capabilities, using integrated circuit chips such as a microprocessor to convert analog television broadcast signals to digital video signals, enabling features such as freezing pictures and showing two channels at once. In 1986, Sony and NEC Home Electronics announced their own similar TV sets with digital video capabilities. However, they still relied on analog TV broadcast signals, with true digital TV broadcasts not yet being available at the time.

A digital TV broadcast service was proposed in 1986 by Nippon Telegraph and Telephone (NTT) and the Ministry of Posts and Telecommunication (MPT) in Japan, where there were plans to develop an "Integrated Network System" service. However, it was not possible to practically implement such a digital TV service until the adoption of motion-compensated DCT video compression formats such as MPEG made it possible in the early 1990s.

In the mid-1980s, as Japanese consumer electronics firms forged ahead with the development of HDTV technology, and as the MUSE analog format was proposed by Japan's public broadcaster NHK as a worldwide standard. Japanese advancements were seen as pacesetters that threatened to eclipse US electronics companies. Until June 1990, the Japanese MUSE standard—based on an analog system—was the front-runner among the more than 23 different technical concepts under consideration.

Between 1988 and 1991, several European organizations were working on DCT-based digital video coding standards for both SDTV and HDTV. The EU 256 project by the CMTT and ETSI, along with research by Italian broadcaster RAI, developed a DCT video codec that broadcast SDTV at 34Mbit/s and near-studio-quality HDTV at about 70–140Mbit/s. RAI demonstrated this with a 1990 FIFA World Cup broadcast in March 1990. An American company, General Instrument, also demonstrated the feasibility of a digital television signal in 1990. This led to the FCC being persuaded to delay its decision on an advanced television (ATV) standard until a digitally based standard could be developed.

In March 1990, when it became clear that a digital standard was feasible, the FCC made a number of critical decisions. First, the Commission declared that the new TV standard must be more than an enhanced analog signal, but be able to provide a genuine HDTV signal with at least twice the resolution of existing television images. Then, to ensure that viewers who did not wish to buy a new digital television set could continue to receive conventional television broadcasts, it dictated that the new ATV standard must be capable of being simulcast on different channels. The new ATV standard also allowed the new DTV signal to be based on entirely new design principles. Although incompatible with the existing NTSC standard, the new DTV standard would be able to incorporate many improvements.

The final standard adopted by the FCC did not produce a universal standard for scanning formats, aspect ratios, or lines of resolution. This outcome resulted from a dispute between the consumer electronics industry (joined by some broadcasters) and the computer industry (joined by the film industry and some public interest groups) over which of the two scanning processes—interlaced or progressive—is superior. Interlaced scanning, which is used in televisions worldwide, scans even-numbered lines first, then odd-numbered ones. Progressive scanning, which is the format used in computers, scans lines in sequences, from top to bottom. The computer industry argued that progressive scanning is superior because it does not flicker in the manner of interlaced scanning. It also argued that progressive scanning enables easier connections with the Internet, and is more cheaply converted to interlaced formats than vice versa. The film industry also supported progressive scanning because it offers a more efficient means of converting filmed programming into digital formats. For their part, the consumer electronics industry and broadcasters argued that interlaced scanning was the only technology that could transmit the highest quality pictures then (and currently) feasible, i.e., 1,080 lines per picture and 1,920 pixels per line. Broadcasters also favored interlaced scanning because their vast archive of interlaced programming is not readily compatible with a progressive format.

Inaugural launches
DirecTV in the US launched the first commercial digital satellite platform in May 1994, using the Digital Satellite System (DSS) standard. Digital cable broadcasts were tested and launched in the US in 1996 by TCI and Time Warner. The first digital terrestrial platform was launched in November 1998 as ONdigital in the UK, using the DVB-T standard.

Formats and bandwidth
Digital television supports many different picture formats defined by the broadcast television systems which are a combination of size and aspect ratio (width to height ratio).

With digital terrestrial television (DTT) broadcasting, the range of formats can be broadly divided into two categories: high-definition television (HDTV) for the transmission of high-definition video and standard-definition television (SDTV). These terms by themselves are not very precise, and many subtle intermediate cases exist.

One of several different HDTV formats that can be transmitted over DTV is: pixels in progressive scan mode (abbreviated 720p) or  pixels in interlaced video mode (1080i). Each of these uses a 16:9 aspect ratio. HDTV cannot be transmitted over analog television channels because of channel capacity issues.

SDTV, by comparison, may use one of several different formats taking the form of various aspect ratios depending on the technology used in the country of broadcast. NTSC can deliver a resolution in 4:3 and  in 16:9, while PAL can give  in 4:3 and  in 16:9. However, broadcasters may choose to reduce these resolutions to reduce bit rate (e.g., many DVB-T channels in the UK use a horizontal resolution of 544 or 704 pixels per line).

Each commercial broadcasting terrestrial television DTV channel in North America is allocated enough bandwidth to broadcast up to 19 megabits per second. However, the broadcaster does not need to use this entire bandwidth for just one broadcast channel. Instead, the broadcast can use Program and System Information Protocol and subdivide across several video subchannels (a.k.a. feeds) of varying quality and compression rates, including non-video datacasting services.

A broadcaster may opt to use a standard-definition (SDTV) digital signal instead of an HDTV signal, because current convention allows the bandwidth of a DTV channel (or "multiplex") to be subdivided into multiple digital subchannels, (similar to what most FM radio stations offer with HD Radio), providing multiple feeds of entirely different television programming on the same channel. This ability to provide either a single HDTV feed or multiple lower-resolution feeds is often referred to as distributing one's bit budget or multicasting. This can sometimes be arranged automatically, using a statistical multiplexer. With some implementations, image resolution may be less directly limited by bandwidth; for example in DVB-T, broadcasters can choose from several different modulation schemes, giving them the option to reduce the transmission bit rate and make reception easier for more distant or mobile viewers.

Reception
There are several different ways to receive digital television. One of the oldest means of receiving DTV (and TV in general) is from terrestrial transmitters using an antenna (known as an aerial in some countries). This delivery method is known as digital terrestrial television (DTT). With DTT, viewers are limited to channels that have a terrestrial transmitter in range of their antenna.

Other delivery methods include digital cable and digital satellite. In some countries where transmissions of TV signals are normally achieved by microwaves, digital multichannel multipoint distribution service is used. Other standards, such as digital multimedia broadcasting (DMB) and digital video broadcasting - handheld (DVB-H), have been devised to allow handheld devices such as mobile phones to receive TV signals. Another way is Internet Protocol television (IPTV), which is the delivery of TV over a computer network. Finally, an alternative way is to receive digital TV signals via the open Internet (Internet television), whether from a central streaming service or a P2P (peer-to-peer) system.

Some signals are protected by encryption and backed up with the force of law under the WIPO Copyright Treaty and national legislation implementing it, such as the US Digital Millennium Copyright Act. Access to encrypted channels can be controlled by a removable card, for example via the Common Interface or CableCard.

Protection parameters
Digital television signals must not interfere with each other, and they must also coexist with analog television until it is phased out. The following table gives allowable signal-to-noise and signal-to-interference ratios for various interference scenarios. This table is a crucial regulatory tool for controlling the placement and power levels of stations. Digital TV is more tolerant of interference than analog TV.

Interaction
People can interact with a DTV system in various ways. One can, for example, browse the electronic program guide. Modern DTV systems sometimes use a return path providing feedback from the end user to the broadcaster. This is possible over cable TV or through an Internet connection but is not possible with a standard antenna alone.

Some of these systems support video on demand using a communication channel localized to a neighborhood rather than a city (terrestrial) or an even larger area (satellite).

1seg
1seg (1-segment) is a special form of ISDB. Each channel is further divided into 13 segments. Twelve are allocated for HDTV and the other for narrow-band receivers such as mobile televisions and cell phones.

Comparison to analog
DTV has several advantages over analog television, the most significant being that digital channels take up less bandwidth, and the bandwidth allocations are flexible depending on the level of compression and resolution of the transmitted image. This means that digital broadcasters can provide more digital channels in the same space, provide high-definition television service, or provide other non-television services such as multimedia or interactivity. DTV also permits special services such as multiplexing (more than one program on the same channel), electronic program guides and additional languages (spoken or subtitled). The sale of non-television services may provide an additional revenue source to broadcasters.

Digital and analog signals react to interference differently. For example, common problems with analog television include ghosting of images, noise from weak signals, and other problems that degrade the quality of the image and sound, although the program material may still be watchable. With digital television, because of the cliff effect, reception of the digital signal must be very nearly complete; otherwise, neither audio nor video will be usable.

Analog TV began with monophonic sound and later developed multichannel television sound with two independent audio signal channels. DTV allows up to 5 audio signal channels plus a subwoofer bass channel, producing broadcasts similar in quality to movie theaters and DVDs.

Digital TV signals require less transmission power than analog TV signals to be broadcast and received satisfactorily.

Compression artifacts, picture quality monitoring, and allocated bandwidth
DTV images have some picture defects that are not present on analog television or motion picture cinema, because of present-day limitations of bit rate and compression algorithms such as MPEG-2. This defect is sometimes referred to as mosquito noise.

Because of the way the human visual system works, defects in an image that are localized to particular features of the image or that come and go are more perceptible than defects that are uniform and constant. However, the DTV system is designed to take advantage of other limitations of the human visual system to help mask these flaws, e.g. by allowing more compression artifacts during fast motion where the eye cannot track and resolve them as easily and, conversely, minimizing artifacts in still backgrounds that, because time allows, may be closely examined in a scene.

Broadcast, cable, satellite, and Internet DTV operators control the picture quality of television signal encoders using sophisticated, neuroscience-based algorithms, such as the structural similarity index measure (SSIM) video quality measurement tool. Another tool called visual information fidelity (VIF), is used in the Netflix VMAF video quality monitoring system.

Quantising effects can create contours – rather than smooth gradations – on areas with small graduations in amplitude. Typically, a very flat scene, such as a cloudless sky, will exhibit visible steps across its expanse, often appearing as concentric circles or ellipses. This is known as color banding. Similar effects can be seen in very dark scenes, where true black backgrounds are overlaid by dark gray areas. These transitions may be smooth, or may show a scattering effect as the digital processing dithers and is unable to consistently allocate a value of either absolute black or the next step up the greyscale.

Effects of poor reception
Changes in signal reception from factors such as degrading antenna connections or changing weather conditions may gradually reduce the quality of analog TV. The nature of digital TV results in a perfectly decodable video initially, until the receiving equipment starts picking up interference that overpowers the desired signal or if the signal is too weak to decode. Some equipment will show a garbled picture with significant damage, while other devices may go directly from perfectly decodable video to no video at all or lock up. This phenomenon is known as the digital cliff effect.

Block errors may occur when transmission is done with compressed images. A block error in a single frame often results in black boxes in several subsequent frames, making viewing difficult.

For remote locations, distant channels that, as analog signals, were previously usable in a snowy and degraded state may, as digital signals, be perfectly decodable or may become completely unavailable. The use of higher frequencies add to these problems, especially in cases where a clear line-of-sight from the receiving antenna to the transmitter is not available, because usually higher frequency signals can't pass through obstacles as easily.

Effect on old analog technology
Television sets with only analog tuners cannot decode digital transmissions. When analog broadcasting over the air ceases, users of sets with analog-only tuners may use other sources of programming (e.g. cable, recorded media) or may purchase set-top converter boxes to tune in the digital signals. In the United States, a government-sponsored coupon was available to offset the cost of an external converter box.

The digital television transition began around the late 1990s and has been completed on a country-by-country basis in most parts of the world.

Disappearance of TV-audio receivers
Prior to the conversion to digital TV, analog television broadcast audio for TV channels on a separate FM carrier signal from the video signal. This FM audio signal could be heard using standard radios equipped with the appropriate tuning circuits.

However, after the digital television transition, no portable radio manufacturer has yet developed an alternative method for portable radios to play just the audio signal of digital TV channels; DTV radio is not the same thing.

Environmental issues
The adoption of a broadcast standard incompatible with existing analog receivers has created the problem of large numbers of analog receivers being discarded. One superintendent of public works was quoted in 2009 saying; "some of the studies I’ve read in the trade magazines say up to a quarter of American households could be throwing a TV out in the next two years following the regulation change". In Michigan in 2009, one recycler estimated that as many as one household in four would dispose of or recycle a TV set in the following year. The digital television transition, migration to high-definition television receivers and the replacement of CRTs with flat screens are all factors in the increasing number of discarded analog CRT-based television receivers. In 2009, an estimated 99 million analog TV receivers were sitting unused in homes in the US alone and, while some obsolete receivers are being retrofitted with converters, many more are simply dumped in landfills where they represent a source of toxic metals such as lead as well as lesser amounts of materials such as barium, cadmium and chromium.

title: Digital television


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Declaration of Arbroath

The Declaration of Arbroath (Declaratio Arbroathis; Declaration o Aiberbrothock; Tiomnadh Bhruis) is the name usually given to a letter, dated 6 April 1320 at Arbroath, written by Scottish barons and addressed to Pope John XXII. It constituted King Robert I's response to his excommunication for disobeying the pope's demand in 1317 for a truce in the First War of Scottish Independence. The letter asserted the antiquity of the independence of the Kingdom of Scotland, denouncing English attempts to subjugate it.

Generally believed to have been written in Arbroath Abbey by Bernard of Kilwinning (or of Linton), then Chancellor of Scotland and Abbot of Arbroath, and sealed by fifty-one magnates and nobles, the letter is the sole survivor of three created at the time. The others were a letter from the King of Scots, Robert I, and a letter from four Scottish bishops which all made similar points. The Declaration was intended to assert Scotland's status as an independent, sovereign state and defend Scotland's right to use military action when unjustly attacked.

Submitted in Latin, the Declaration was little known until the late 17th century, and is unmentioned by any of Scotland's major 16th-century historians. In the 1680s, the Latin text was printed for the first time and translated into English in the wake of the Glorious Revolution, after which time it was sometimes described as a declaration of independence.

Overview
The Declaration was part of a broader diplomatic campaign, which sought to assert Scotland's position as an independent kingdom, rather than its being a feudal land controlled by England's Norman kings, as well as to lift the excommunication of Robert the Bruce. The pope had recognised Edward I of England's claim to overlordship of Scotland in 1305 and Bruce was excommunicated by the Pope for murdering John Comyn before the altar at Greyfriars Church in Dumfries in 1306. This excommunication was lifted in 1308; subsequently the pope threatened Robert with excommunication again if Avignon's demands in 1317 for peace with England were ignored. Warfare continued, and in 1320 John XXII again excommunicated Robert I. In reply, the Declaration was composed and signed and, in response, the papacy rescinded King Robert Bruce's excommunication and thereafter addressed him using his royal title.

The wars of Scottish independence began as a result of the deaths of King Alexander III of Scotland in 1286 and his heir the "Maid of Norway" in 1290, which left the throne of Scotland vacant and the subsequent succession crisis of 1290–1296 ignited a struggle among the Competitors for the Crown of Scotland, chiefly between the House of Comyn, the House of Balliol, and the House of Bruce who all claimed the crown. After July 1296's deposition of King John Balliol by Edward of England and then February 1306's killing of John Comyn III, Robert Bruce's rivals to the throne of Scotland were gone, and Robert was crowned king at Scone that year. Edward I, the "Hammer of Scots", died in 1307; his son and successor Edward II did not renew his father's campaigns in Scotland. In 1309 a parliament held at St Andrews acknowledged Robert's right to rule, received emissaries from the Kingdom of France recognising the Bruce's title, and proclaimed the independence of the kingdom from England.

By 1314 only Edinburgh, Berwick-upon-Tweed, Roxburgh, and Stirling remained in English hands. In June 1314 the Battle of Bannockburn had secured Robert Bruce's position as King of Scots; Stirling, the Central Belt, and much of Lothian came under Robert's control while the defeated Edward II's power on escaping to England via Berwick weakened under the sway of his cousin Henry, Earl of Lancaster. King Robert was thus able to consolidate his power, and sent his brother Edward Bruce to claim the Kingdom of Ireland in 1315 with an army landed in Ulster the previous year with the help of Gaelic lords from the Isles. Edward Bruce died in 1318 without achieving success, but the Scots campaigns in Ireland and in northern England were intended to press for the recognition of Robert's crown by King Edward. At the same time, it undermined the House of Plantagenet's claims to overlordship of the British Isles and halted the Plantagenets' effort to absorb Scotland as had been done in Ireland and Wales. Thus were the Scots nobles confident in their letters to Pope John of the distinct and independent nature of Scotland's kingdom; the Declaration of Arbroath was one such. According to historian David Crouch, "The two nations were mutually hostile kingdoms and peoples, and the ancient idea of Britain as an informal empire of peoples under the English king's presidency was entirely dead."

The text describes the ancient history of Scotland, in particular the Scoti, the Gaelic forebears of the Scots who the Declaration claims have origins in Scythia Major prior to migrating via Spain to Great Britain "1,200 years from the Israelite people's crossing of the Red Sea". The Declaration describes how the Scots had "thrown out the Britons and completely destroyed the Picts", resisted the invasions of "the Norse, the Danes and the English", and "held itself ever since, free from all slavery". It then claims that in the Kingdom of Scotland, "one hundred and thirteen kings have reigned of their own Blood Royal, without interruption by foreigners". The text compares Robert Bruce with the Biblical warriors Judah Maccabee and Joshua.

The Declaration made a number of points: that Edward I of England had unjustly attacked Scotland and perpetrated atrocities; that Robert the Bruce had delivered the Scottish nation from this peril; and, most controversially, that the independence of Scotland was the prerogative of the Scottish people, rather than the King of Scots.

Debates
Some have interpreted this last point as an early expression of popular sovereignty – that government is contractual and that kings can be chosen by the community rather than by God alone. It has been considered to be the first statement of the contractual theory of monarchy underlying modern constitutionalism.

It has also been argued that the Declaration was not a statement of popular sovereignty (and that its signatories would have had no such concept) but a statement of royal propaganda supporting Bruce's faction. A justification had to be given for the rejection of King John Balliol in whose name William Wallace and Andrew de Moray had rebelled in 1297. The reason given in the Declaration is that Bruce was able to defend Scotland from English aggression whereas King John could not. "To this man, in as much as he saved our people, and for upholding our freedom, we are bound by right as much as by his merits, and choose to follow him in all that he does." Whatever the true motive, the idea of a contract between King and people was advanced to the Pope as a justification for Bruce's coronation whilst John de Balliol, who had abdicated the Scottish throne, still lived as a Papal prisoner.

There is also recent scholarship that suggests that the Declaration was substantially derived from the 1317 Irish Remonstrance, also sent in protest of English actions. There are substantial similarities in content between the 1317 Irish Remonstrance and the Declaration of Arbroath, produced three years later. It is also clear that the drafters of the Declaration of Arbroath would have access to the 1317 Irish Remonstrance, it having been circulated to Scotland in addition to the Pope. It has been suggested therefore that the 1317 Remonstrance was a "prototype" for the Declaration of Arbroath, suggesting Irish-Scottish cooperation in attempts to protest against English interference.

Text
For the full text in Latin and a translation in English, See Declaration of Arbroath on WikiSource.

Signatories
There are 39 names—eight earls and thirty-one barons—at the start of the document, all of whom may have had their seals appended, probably over the space of some time, possibly weeks, with nobles sending in their seals to be used. The folded foot of the document shows that at least eleven additional barons and freeholders (who were not noble) who were not listed on the head were associated with the letter. On the extant copy of the Declaration there are only 19 seals, and of those 19 people only 12 are named within the document. It is thought likely that at least 11 more seals than the original 39 might have been appended. The Declaration was then taken to the papal court at Avignon by Sir Adam Gordon, Sir Odard de Maubuisson, and Bishop Kininmund who was not yet a bishop and probably included for his scholarship.

The Pope heeded the arguments contained in the Declaration, influenced by the offer of support from the Scots for his long-desired crusade if they no longer had to fear English invasion. He exhorted Edward II in a letter to make peace with the Scots. However, it did not lead to his recognising Robert as King of Scots, and the following year was again persuaded by the English to take their side and issued six bulls to that effect.

Eight years later, on 1 March 1328, the new English king, Edward III, signed a peace treaty between Scotland and England, the Treaty of Edinburgh–Northampton. In this treaty, which was in effect until 1333, Edward renounced all English claims to Scotland. In October 1328, the interdict on Scotland, and the excommunication of its king, were removed by the Pope.

Manuscript
The original copy of the Declaration that was sent to Avignon is lost. The only existing manuscript copy of the Declaration survives among Scotland's state papers, measuring 540mm wide by 675mm long (including the seals), it is held by the National Archives of Scotland in Edinburgh, a part of the National Records of Scotland.

The most widely known English language translation was made by Sir James Fergusson, formerly Keeper of the Records of Scotland, from text that he reconstructed using this extant copy and early copies of the original draft.

G. W. S. Barrow has shown that one passage in particular, often quoted from the Fergusson translation, was carefully written using different parts of The Conspiracy of Catiline by the Roman author, Sallust (86–35 BC) as the direct source:

"... for, as long as but a hundred of us remain alive, never will we on any conditions be brought under English rule. It is in truth not for glory, nor riches, nor honours that we are fighting, but for freedom – for that alone, which no honest man gives up but with life itself."

List of signatories
Listed below are the signatories of the Declaration of Arbroath in 1320.

The letter itself is written in Latin. It uses the Latin versions of the signatories' titles, and in some cases, the spelling of names has changed over the years. This list generally uses the titles of the signatories' Wikipedia biographies.

 * Duncan, Earl of Fife (changed sides in 1332)
 * Thomas Randolph, Earl of Moray (nephew and supporter of King Robert although briefly fought for the English after being captured by them, Guardian of the Realm after Robert the Bruce's death)
 * Patrick Dunbar, Earl of March (or Earl of Dunbar) (changed sides several times)
 * Malise, Earl of Strathearn (King Robert loyalist)
 * Malcolm, Earl of Lennox (King Robert loyalist)
 * William, Earl of Ross (earlier betrayed King Robert's female relatives to the English)
 * Magnús Jónsson, Earl of Orkney
 * William de Moravia, Earl of Sutherland
 * Walter, High Steward of Scotland (King Robert loyalist)
 * William de Soules, Lord of Liddesdale and Butler of Scotland (later imprisoned for plotting against the King)
 * Sir James Douglas, Lord of Douglas (one of King Robert's leading loyalists)
 * Roger de Mowbray, Lord of Barnbougle and Dalmeny (later imprisoned for plotting against King Robert)
 * David, Lord of Brechin (later executed for plotting against King Robert)
 * David de Graham of Kincardine
 * Ingram de Umfraville (fought on the English side at Bannockburn but then changed sides to support King Robert)
 * John de Menteith, guardian of the earldom of Menteith (earlier betrayed William Wallace to the English)
 * Alexander Fraser of Touchfraser and Cowie
 * Gilbert de la Hay, Constable of Scotland (King Robert loyalist)
 * Robert Keith, Marischal of Scotland (King Robert loyalist)
 * Henry St Clair of Rosslyn
 * John de Graham, Lord of Dalkeith, Abercorn & Eskdale
 * David Lindsay of Crawford
 * William Oliphant, Lord of Aberdalgie and Dupplin (briefly fought for the English)
 * Patrick de Graham of Lovat
 * John de Fenton, Lord of Baikie and Beaufort
 * William de Abernethy of Saltoun
 * David Wemyss of Wemyss
 * William Mushet
 * Fergus of Ardrossan
 * Eustace Maxwell of Caerlaverock
 * William Ramsay
 * William de Monte Alto, Lord of Ferne
 * Alan Murray
 * Donald Campbell
 * John Cameron
 * Reginald le Chen, Lord of Inverugie and Duffus
 * Alexander Seton
 * Andrew de Leslie
 * Alexander Straiton

In addition, the names of the following do not appear in the document's text, but their names are written on seal tags and their seals are present:

 * Alexander de Lamberton (became a supporter of Edward Balliol after the Battle of Dupplin Moor, 1332)
 * Edward Keith (subsequently Marischal of Scotland; d. 1346)
 * Arthur Campbell (Bruce loyalist)
 * Thomas de Menzies (Bruce loyalist)
 * John de Inchmartin (became a supporter of Edward Balliol after the Battle of Dupplin Moor, 1332; d. after 1334)
 * John Duraunt
 * Thomas de Morham

Legacy
In 1998 former majority leader Trent Lott succeeded in instituting an annual "National Tartan Day" on 6 April by resolution of the United States Senate. US Senate Resolution 155 of 10 November 1997 states that "the Declaration of Arbroath, the Scottish Declaration of Independence, was signed on April 6, 1320 and the American Declaration of Independence was modeled [sic] on that inspirational document". However this claim is generally unsupported by historians.

In 2016 the Declaration of Arbroath was placed on the UK Memory of the World Register, part of UNESCO's Memory of the World Programme.

2020 was the 700th anniversary of the Declaration of Arbroath's composition; an Arbroath 2020 festival was arranged but postponed due to the COVID-19 pandemic. The National Museum of Scotland in Edinburgh planned to display the document to the public for the first time in fifteen years.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Declaration of Arbroath


text:
Digital data

Digital data, in information theory and information systems, is information represented as a string of discrete symbols, each of which can take on one of only a finite number of values from some alphabet, such as letters or digits. An example is a text document, which consists of a string of alphanumeric characters. The most common form of digital data in modern information systems is binary data, which is represented by a string of binary digits (bits) each of which can have one of two values, either 0 or 1.

Digital data can be contrasted with analog data, which is represented by a value from a continuous range of real numbers. Analog data is transmitted by an analog signal, which not only takes on continuous values but can vary continuously with time, a continuous real-valued function of time. An example is the air pressure variation in a sound wave.

The word digital comes from the same source as the words digit and digitus (the Latin word for finger), as fingers are often used for counting. Mathematician George Stibitz of Bell Telephone Laboratories used the word digital in reference to the fast electric pulses emitted by a device designed to aim and fire anti-aircraft guns in 1942. The term is most commonly used in computing and electronics, especially where real-world information is converted to binary numeric form as in digital audio and digital photography.

Symbol to digital conversion
Since symbols (for example, alphanumeric characters) are not continuous, representing symbols digitally is rather simpler than conversion of continuous or analog information to digital. Instead of sampling and quantization as in analog-to-digital conversion, such techniques as polling and encoding are used.

A symbol input device usually consists of a group of switches that are polled at regular intervals to see which switches are switched. Data will be lost if, within a single polling interval, two switches are pressed, or a switch is pressed, released, and pressed again. This polling can be done by a specialized processor in the device to prevent burdening the main CPU. When a new symbol has been entered, the device typically sends an interrupt, in a specialized format, so that the CPU can read it.

For devices with only a few switches (such as the buttons on a joystick), the status of each can be encoded as bits (usually 0 for released and 1 for pressed) in a single word. This is useful when combinations of key presses are meaningful, and is sometimes used for passing the status of modifier keys on a keyboard (such as shift and control). But it does not scale to support more keys than the number of bits in a single byte or word.

Devices with many switches (such as a computer keyboard) usually arrange these switches in a scan matrix, with the individual switches on the intersections of x and y lines. When a switch is pressed, it connects the corresponding x and y lines together. Polling (often called scanning in this case) is done by activating each x line in sequence and detecting which y lines then have a signal, thus which keys are pressed. When the keyboard processor detects that a key has changed state, it sends a signal to the CPU indicating the scan code of the key and its new state. The symbol is then encoded or converted into a number based on the status of modifier keys and the desired character encoding.

A custom encoding can be used for a specific application with no loss of data. However, using a standard encoding such as ASCII is problematic if a symbol such as 'ß' needs to be converted but is not in the standard.

It is estimated that in the year 1986, less than 1% of the world's technological capacity to store information was digital and in 2007 it was already 94%. The year 2002 is assumed to be the year when humankind was able to store more information in digital than in analog format (the "beginning of the digital age").

States
Digital data come in these three states: data at rest, data in transit, and data in use. The confidentiality, integrity, and availability have to be managed during the entire lifecycle from 'birth' to the destruction of the data.

Properties of digital information
All digital information possesses common properties that distinguish it from analog data with respect to communications:
 * Synchronization: Since digital information is conveyed by the sequence in which symbols are ordered, all digital schemes have some method for determining the beginning of a sequence. In written or spoken human languages, synchronization is typically provided by pauses (spaces), capitalization, and punctuation. Machine communications typically use special synchronization sequences.
 * Language: All digital communications require a formal language, which in this context consists of all the information that the sender and receiver of the digital communication must both possess, in advance, for the communication to be successful. Languages are generally arbitrary and specify the meaning to be assigned to particular symbol sequences, the allowed range of values, methods to be used for synchronization, etc.
 * Errors: Disturbances (noise) in analog communications invariably introduce some, generally small deviation or error between the intended and actual communication. Disturbances in digital communication only result in errors when the disturbance is so large as to result in a symbol being misinterpreted as another symbol or disturbing the sequence of symbols. It is generally possible to have near-error-free digital communication. Further, techniques such as check codes may be used to detect errors and correct them through redundancy or re-transmission. Errors in digital communications can take the form of substitution errors, in which a symbol is replaced by another symbol, or insertion/deletion errors, in which an extra incorrect symbol is inserted into or deleted from a digital message. Uncorrected errors in digital communications have an unpredictable and generally large impact on the information content of the communication.
 * Copying: Because of the inevitable presence of noise, making many successive copies of an analog communication is infeasible because each generation increases the noise. Because digital communications are generally error-free, copies of copies can be made indefinitely.
 * Granularity: The digital representation of a continuously variable analog value typically involves a selection of the number of symbols to be assigned to that value. The number of symbols determines the precision or resolution of the resulting datum. The difference between the actual analog value and the digital representation is known as quantization error. For example, if the actual temperature is 23.234456544453 degrees, but only two digits (23) are assigned to this parameter in a particular digital representation, the quantizing error is 0.234456544453. This property of digital communication is known as granularity.
 * Compressible: According to Miller, "Uncompressed digital data is very large, and in its raw form, it would actually produce a larger signal (therefore be more difficult to transfer) than analog data. However, digital data can be compressed. Compression reduces the amount of bandwidth space needed to send information. Data can be compressed, sent, and then decompressed at the site of consumption. This makes it possible to send much more information and results in, for example, digital television signals offering more room on the airwave spectrum for more television channels."

Historical digital systems
Even though digital signals are generally associated with the binary electronic digital systems used in modern electronics and computing, digital systems are actually ancient, and need not be binary or electronic.
 * DNA genetic code is a naturally occurring form of digital data storage.
 * Written text (due to the limited character set and the use of discrete symbols – the alphabet in most cases)
 * The abacus was created sometime between 1000 BC and 500 BC, it later became a form of calculation frequency. Nowadays it can be used as a very advanced, yet basic digital calculator that uses beads on rows to represent numbers. Beads only have meaning in discrete up and down states, not in analog in-between states.
 * A beacon is perhaps the simplest non-electronic digital signal, with just two states (on and off). In particular, smoke signals are one of the oldest examples of a digital signal, where an analog "carrier" (smoke) is modulated with a blanket to generate a digital signal (puffs) that conveys information.
 * Morse code uses six digital states—dot, dash, intra-character gap (between each dot or dash), short gap (between each letter), medium gap (between words), and long gap (between sentences)—to send messages via a variety of potential carriers such as electricity or light, for example using an electrical telegraph or a flashing light.
 * The Braille uses a six-bit code rendered as dot patterns.
 * Flag semaphore uses rods or flags held in particular positions to send messages to the receiver watching them some distance away.
 * International maritime signal flags have distinctive markings that represent letters of the alphabet to allow ships to send messages to each other.
 * More recently invented, a modem modulates an analog "carrier" signal (such as sound) to encode binary electrical digital information, as a series of binary digital sound pulses. A slightly earlier, surprisingly reliable version of the same concept was to bundle a sequence of audio digital "signal" and "no signal" information (i.e. "sound" and "silence") on magnetic cassette tape for use with early home computers.

title: Digital data


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Deduction

Deduction may refer to:

Philosophy

 * Deductive reasoning, the mental process of drawing inferences in which the truth of their premises ensures the truth of their conclusion
 * Natural deduction, a class of proof systems based on simple and self-evident rules of inference that aim to closely mirror how reasoning actually occurs

Taxation

 * Tax deduction, variable tax dollars subtracted from gross income
 * Itemized deduction, eligible expense that individual taxpayers in the United States can report on their Federal income tax returns
 * Standard deduction, dollar amount that non-itemizers may subtract from their income

Other uses

 * English modals of deduction, English modal verbs to state how sure somebody is about something.
 * Deduction (food stamps), used in the United States to calculate a household's monthly food stamp benefit goods

title: Deduction