title: Republic of Crimea

text: United Nations monitors (that had been in Crimea from 2 April to 6 May 2014) said they were concerned about treatment of journalists, sexual, religious and ethnic minorities and AIDS patients. The monitors had found that journalists and activists who had opposed the 2014 Crimean referendum had been harassed and abducted. They also reported that Crimeans who had not applied for Russian citizenship faced harassment and intimidation. Russia said that it did not support the deployment of human rights monitors in Crimea. The (new) Crimean authorities vowed to investigate the reports of human rights violations.


title: Republic of Crimea

text: According to Human Rights Watch "Russia has violated multiple obligations it has as an occupying power under international humanitarian law – in particular in relation to the protection of civilians' rights."


title: Republic of Crimea

text: In its November 2014 report on Crimea, Human Rights Watch stated that "The de facto authorities in Crimea have limited free expression, restricted peaceful assembly, and intimidated and harassed those who have opposed Russia's actions in Crimea". According to the report, 15 persons went missing since March 2014; according to Ukrainian authorities 21 people disappeared. Head of the Republic Sergey Aksyonov pledged to find the missing persons as well as the culprits behind the kidnappings. Aksyonov regularly meets with a group of parents, whose children have gone missing, and human rights activists. These parents and human rights activists have complained that rotation of the team of investigators into these missing persons has harmed these investigations.


title: Republic of Crimea

text: The Mejlis of the Crimean Tatar People has come under the scrutiny of the Russian Federal Security Service, which reportedly took control of the building where the Mejlis meets and searched it on 16 September 2014. Crimean Tatar media said FSB officers also searched the office of the "Avdet" newspaper, which is based inside the Mejlis building. Several members of the Mejlis were also reportedly subjected to FSB searches at their homes. Several Crimean Tatar opposition figures were banned from entering Crimea for five years. Since Russia annexed Crimea several Crimean Tatars have disappeared or have been found dead after being reported missing. Crimean authorities state these deaths and disappearances are connected to "smoking an unspecified substance" and volunteers for the Syrian civil war; human rights activists claim the disappearances are part of a repression campaign against Crimean Tatars.


title: Republic of Crimea

text: In February 2016 human rights defender Emir-Usein Kuku from Crimea was arrested and accused of belonging to the Islamist organization Hizb ut-Tahrir although he denies any involvement in this organization. Amnesty International has called for his immediate liberation.


title: Republic of Crimea

text: In May 2018, Server Mustafayev, the founder and coordinator of the human rights movement Crimean Solidarity, was imprisoned by Russian authorities and charged with "membership of a terrorist organisation". Amnesty International and Front Line Defenders demand his immediate release.


title: Republic of Crimea

text: The status of the republic is disputed, as Russia and some other states recognised the annexation, whilst most other nations do not. Ukraine still considers both the Autonomous Republic and Sevastopol as subdivisions of Ukraine under Ukrainian territory and subject to Ukrainian law.


title: Republic of Crimea

text: The official line of the US, EU and Australia is that they don't grant visas to Crimeans with Russian passports. Nevertheless, Russian media claims Crimeans get visas for some EU countries.


title: Republic of Crimea

text: On 21 March 2014, Armenia recognised the Crimean referendum, which led to Ukraine recalling its ambassador to that country. The unrecognized Nagorno-Karabakh Republic also recognised the referendum earlier that week on 17 March. On 22 March 2014, President Hamid Karzai of Afghanistan told a U.S. delegation that he recognised and supported the Crimean referendum and "respects the free will of the people of Crimea and Sevastopol to decide their own future". On 23 March 2014, Belarus recognised Crimea as "de facto" part of Russia. On 27 March 2014, Nicaragua unconditionally recognised the incorporation of Crimea into Russia.


title: Republic of Crimea

text: On 27 March 2014, the UN General Assembly voted on a non-binding resolution claiming that the referendum was invalid and reaffirming Ukraine's territorial integrity, by a vote of 100 to 11, with 58 abstentions and 24 absent. Australia, Canada, Chile, France, Germany, Italy, Indonesia, Japan, Mexico, United Kingdom, United States and 89 other countries voted for; Armenia, Belarus, Bolivia, Cuba, North Korea, Nicaragua, Sudan, Syria, Venezuela and Zimbabwe, as well as Russia, voted against. Among the abstaining countries were China, India, Pakistan, South Africa and Brazil. Israel was among the countries listed as absent. Reuters reported unnamed UN diplomats saying the Russian delegation threatened with punitive action against certain Eastern European and Central Asian countries if they supported the resolution. Subsequent United Nations General Assembly resolutions also reaffirmed non-recognition of the annexation and condemned "the temporary occupation of part of the territory of Ukraine—the Autonomous Republic of Crimea and the city of Sevastopol".


title: Darkseid

text: Darkseid () is a supervillain appearing in American comic books published by DC Comics. The character was created by writer-artist Jack Kirby to serve as the primary antagonist of his "Fourth World" metaseries, and was first seen briefly in "Superman's Pal Jimmy Olsen" #134 in December 1970 before being officially introduced in the debut issue of "Forever People" in February 1971. Kirby modeled Darkseid's face on actor Jack Palance and based his personality on Adolf Hitler and Richard Nixon.


title: Darkseid

text: Formerly known as Uxas, Darkseid is a New God and the tyrannical Lord of Apokolips who is regarded as one of the most powerful beings in the DC Universe. His ultimate goal is to enslave the multiverse by eliminating all hope and free will in sentient beings. He is also the father of Kalibak, Orion and Grayven, and serves as one of Superman's greatest adversaries and the archenemy of the Justice League.


title: Darkseid

text: Darkseid has been adapted in various media incarnations, having made his live-action feature debut in the 2021 DC Extended Universe film "Zack Snyder's Justice League", portrayed by Ray Porter. Michael Ironside, Andre Braugher, Tony Todd, and others have provided the character's voice in media ranging from animation to video games.


title: Darkseid

text: Prince Uxas, the son of King Yuga Khan and Queen Heggra and the second in line to the throne of Apokolips, plotted to seize control over the planet from his older brother, Drax. When Drax attempted to claim the fabled Omega Force, Uxas murdered him and claimed its power for himself. His skin turned to stone, Uxas rechristened himself as Darkseid. At some point, he fell in love with an Apokoliptian scientist and sorceress named Suli, with whom he had a son, Kalibak. However, Heggra ordered Desaad to poison Suli out of the belief that she was corrupting her son.


title: Darkseid

text: Following Suli's death, Darkseid's heart grew even colder and his disdain for his mother intensified when she forced him to marry a woman named Tigra, with whom he had another son, Orion. Seeking vengeance against Heggra for killing the one he loved, Darkseid ordered Desaad to poison her so he could finally become the supreme monarch of Apokolips. Darkseid then tried to force Tigra to eliminate Orion, but the latter was ultimately traded with Highfather's son, Scott Free, as part of a peace treaty between the warring planets of Apokolips and New Genesis. This trade eventually became a setback for Darkseid, with Orion growing up to value and defend the ideals of New Genesis as a powerful champion in opposition to his father. The prophecy foretold that Darkseid would meet his final defeat at the hands of Orion in a cataclysmic battle in the fiery Armaghetto of Apokolips. Likewise, Darkseid and his training minion, Granny Goodness, were unable to break Scott Free's spirit after a long, torturous upbringing and Free ultimately managed to escape Apokolips, taking with him the mightiest of the Female Furies, Big Barda, as his wife. Free, now known as the superhero Mister Miracle, and Barda began living on Earth, and Darkseid used this "betrayal" as a pretext to declare the treaty with New Genesis abrogated so the planets could resume their conflict.


title: Darkseid

text: Seeing other deities as a threat, Darkseid invaded the island of Themyscira in order to discover the secret location of the Olympian deities, planning to overthrow the Olympians and steal their power. Refusing to aid Darkseid in his mad quest, the Amazons battled his Parademon troops, causing half of the Amazon population's death. Wonder Woman was able to gain her revenge against Darkseid for killing so many of her sisters by placing a portion of her own soul into Darkseid. This supposedly weakened the god's power as he lost a portion of his dark edge.


title: Darkseid

text: Darkseid's goal was to eliminate all free will from the universe and reshape it into his own image. To this end, he sought to unravel the mysterious Anti-Life Equation, which gives its user complete control over the thoughts and emotions of all living beings in the universe. Darkseid had tried on several other occasions to achieve dominance of the universe through other methods, most notably through his minion Glorious Godfrey, who could control people's minds with his voice. He had a special interest in Earth, as he believed humans possess collectively within their minds most, if not all, fragments of the Anti-Life Equation.


title: Darkseid

text: Darkseid intended to probe the minds of every human in order to piece together the Equation. This has caused him to clash with many superheroes of the DC Universe, most notably the Kryptonian Superman. Darkseid worked behind the scenes, using superpowered minions in his schemes to overthrow Earth, including working through Intergang, a crime syndicate which employs Apokoliptian technology and later morphed into a religious cult that worships Darkseid as the god of evil.


title: Darkseid

text: One thousand years in the future, Darkseid has been absent for centuries and is almost completely forgotten. He returns and comes into conflict with that era's champions, the Legion of Super-Heroes. After using both scientific and magical methods to enhance his power, Darkseid transposes the planets Apokolips and Daxam—which places Daxam under a yellow sun and gives each of its inhabitants Kryptonian-like superpowers equal to those of Superman. Placing the Daxamites under his mental thrall, he uses them in a massive attempt to conquer the known universe. However, he is eventually defeated by the Legion and many of its allies.


title: Darkseid

text: In Grant Morrison's 2005 "Mister Miracle" limited series, it was revealed that Darkseid had finally discovered the Anti-Life Equation, which he then used to destroy the Fourth World altogether. The New Gods fled to Earth, where they hid. Highfather and his followers were now a group of homeless people. Metron used a wheelchair, the Black Racer was an old white man in a wheelchair, DeSaad was an evil psychiatrist, Granny Goodness was a pimp (or "madam") for the Female Furies and Darkseid himself was now an evil gang leader who is referred to only as "Boss Dark Side". It is revealed that Darkseid actually gave the Sheeda North America in return for Aurakles, Earth's first superhero. This was, in turn, purely in order for Darkseid to get Shilo Norman, whom he considers the "Avatar of Freedom", in his clutches so that he could eventually destroy the New Gods.


title: Darkseid

text: As prophesied, Orion returns to Earth via boom tube for his final battle with Darkseid. During the massive fight, Orion ultimately kills him by ripping his heart out, which created a firepit of Apokolips from Darkseid's chest cavity (in reference to the prophecy of their final battle). As Darkseid dies, a battered, wounded Orion walks away from the battlefield having "won" the battle against his father once and for all. However, Darkseid's life essence endured even the death of his body and fell back in time, where he was reborn as "Boss Dark Side", aided by his resurrected minions and the supervillain Libra.


title: Darkseid

text: Once again bound to the form of a human, "Boss Dark Side" began to appear in a number of titles in the run up to "Final Crisis". In "The Flash" vol. 2 #240, he led an army of fanatics, their will broken by the "spoken form" of the Anti-Life Equation, to kidnap the Tornado Twins. In "Birds of Prey" #118, he runs his Dark Side Club where superhumans fight to the death, brainwashed by drugs produced by Bernadeth. In "Teen Titans" #59, it was revealed that he had employed the Terror Titans to capture the Teen Titans and use them in his club fights.


title: Darkseid

text: In "Final Crisis", Darkseid has begun to take over Earth and corrupt the Multiverse with the aid of his herald Libra, a reborn supervillain and antichrist-like figure who soon converts much of the Secret Society of Super Villains to his cause with the aid of the Crime Bible and the Holy Lance. Darkseid is also joined by the souls of his fellow evil New Gods, who, like Darkseid, now possess either modified human bodies or the bodies of other superpowered beings, such as Mary Marvel.


title: Darkseid

text: Darkseid also arranges for detective Dan Turpin to be lured into the Dark Side Club, where Turpin is turned into Darkseid's "final host", as his Boss Dark Side body has begun to mummify due to Darkseid's foul astral presence. With his legion of followers and allies aiding him as he undergoes his latest "rebirth", Darkseid successfully conquers the Earth with the unleashing of the Anti-Life Equation onto mankind. However, the rebirthing process is still far from complete as Dan Turpin's mind and soul, while corrupted by Darkseid's essence, still remains in firm control over his body. However, at the same moment Shilo Norman, the "Embodiment of Freedom" is shot by S.H.A.D.E. operatives, thus signalling the "Victory of Evil". Darkseid wins control over Turpin's body, now twisted in a close copy of his Apokoliptan former appearance, and wearing an updated version of his battle armor. Darkseid then gains the fullest of his power, his "fall" having the effect of compressing and crumpling spacetime around Earth.


title: Darkseid

text: After escaping from captivity, Batman shoots Darkseid with the same radion bullet that killed Orion, while Darkseid simultaneously hits Batman with the Omega Beam, sending back in time and then "infecting" Batman with Omega energy that will cause him to jump forward in time, with disastrous results when he reaches the present. Darkseid is mortally wounded, but not before his Omega Sanction teleports Batman into prehistoric times. Remains believed to be Batman's (later revealed to be the last of the many Batman clones that Darkseid created) are found by Superman, who confronts Darkseid. As Darkseid mocks his old enemy for failing to defend Earth, it emerges that in Darkseid's fall through the multiverse, he created a doomsday singularity that now threatens all of existence. When Superman attempts to physically assault him, Darkseid reveals that he now exists inside the bodies of all those who fell to the power of the Anti-Life Equation and that killing Darkseid will kill humanity. Darkseid then reloads the gun that was used to shoot him, to kill Orion by way of firing the bullet backwards in time (a move Superman deems to be suicide due to the paradoxical nature of his actions: the bullet used to kill Orion is ultimately fired at him by Batman and is now poisoning him to death).


title: Darkseid

text: Before Darkseid can use the Omega Effect to kill Superman, Barry Allen and Wally West lead the Black Racer to Darkseid and making contact with him frees Turpin from Darkseid's control. Wonder Woman (having been freed from possession by one of Darkseid's minions) then uses her lasso of truth to bind Darkseid's spirit form, effectively freeing humanity from the Anti-Life Equation and being controlled by Darkseid. In his final effort, Darkseid's disembodied essence appears and tries to seize the Miracle Machine Superman has created; however, Superman uses counter-vibrations to destroy him. Furthermore, the last piece of Darkseid's plan fails when Batman, thanks to the actions of the new Batman (Dick Grayson), Red Robin (Tim Drake), Robin (Damian Wayne), and the Justice League, is able to return safely to the present, consuming the Omega Energy in his body without damaging the time-stream further, thus becoming the second individual, along with Mister Miracle, to escape the Omega Sanction.


title: Darkseid

text: Doctor Impossible later manipulates the Crime Syndicate of America into helping him resurrect Darkseid via a machine that draws energy from the Multiverse itself. The resurrection backfires, and instead creates a new being known as the Omega Man.


title: Darkseid

text: In September 2011, The New 52 rebooted DC's continuity. In this new timeline, Darkseid's name is first invoked by a Parademon in "Justice League" #1. He is later mentioned again in "Justice League" #2, and in "Justice League" #3 Darkseid makes his first appearance in the series, seen in a vision by Victor Stone after he is injured by an exploding Mother Box. In the final pages of "Justice League" #4, Darkseid himself appears. In "Justice League" #5, the League confronts him but they are overpowered by him, when he severely hurts Superman with his Omega Beams and breaks Green Lantern's arm. Finally, in "Justice League" #6, Darkseid is driven out when Cyborg activates the invaders' Mother Boxes and Superman forces him through a boom tube. The incidents that occur in these issues make Darkseid the very first foe the newly formed League faces as a team. The issue also reveals DeSaad and Steppenwolf, referring to Darkseid's daughter and their ceaseless search for her across countless worlds. Darkseid's daughter escapes containment in "Justice League of America's Vibe" #7 after the dampeners on her cage are temporarily disabled.


title: Darkseid

text: In the New 52 continuity, there is only one set of New Gods across the 52 Multiverse. So as Darkseid invades Prime Earth in "Justice League", he sends his lieutenant Steppenwolf to do the same, with greater success, on Earth 2, resulting in the deaths of Batman, Superman, and Wonder Woman, and stranding Helena Wayne and Kara Zor-L on Prime Earth. Five years later, Darkseid once again invades Earth 2, which never fully recovered from his armies' earlier assault, and it is revealed that he and Highfather of New Genesis struck a deal allowing him the unchallenged right to invade Earth 2.


title: Darkseid

text: In "Darkseid" #1, his background story was revealed. Formerly a farmer named Uxas, he hated the deities of his world. So he traveled up to their mountain while they slept and tricked them all into fighting each other. As they were all weakened from the war, he killed them one by one with his scythe (similar to Kronos of Greek mythology) and stole their power, before destroying his world and creating Apokolips.


title: Darkseid

text: In "Justice League: The Darkseid War" (after the retirement of the "New 52" imprint), Darkseid comes into conflict with the Anti-Monitor. Darkseid's daughter Grail leads the Anti-Monitor, who is revealed to be a scientist named Mobius, to Darkseid for the former to kill the latter. Mobius believes that with the death of Darkseid, he will be free from being the Anti-Monitor. After an intense battle, the Anti-Monitor fuses the Black Racer with Flash and sends it after Darkseid. Using the fused Flash and his own powers, he kills Darkseid. With Darkseid dead, the universe is unbalanced as it has lost its God of Evil. Later, Lex Luthor would be merged with the Omega Sanction, becoming the new ruler of Apokolips.


title: Darkseid

text: After killing the Anti-Monitor using an Anti-Life Equation-powered Steve Trevor, Grail would later resurrect Darkseid through the newborn child of Superwoman. The child has the same powers as his father Mazahs, with the ability to steal the powers of others. Stealing the new "God" abilities of the Justice League, Grail fuses them with the child and brings Darkseid back to life. However, he is under her complete control. Grail later attempts to redeem herself by seemingly killing Darkseid with the Anti-Life Equation. However, it is later revealed that she reincarnated him back as a baby with the intention of teaching him differently.


title: Darkseid

text: Darkseid (as a baby) appears in "DC Universe: Rebirth" #1 where Grail tells him of Wonder Woman's long lost brother, Jason.


title: Darkseid

text: Baby Darkseid reappears in "Dark Nights: Metal" where it is shown that Batman stole him from Grail and intends to use the Omega Beams to send himself back in time. This never comes to fruition and Darkseid is either returned to or retrieved by Grail.


title: Darkseid

text: Sometime afterwards, Darkseid matured into a toddler, and using telepathy, demanded that he needed to feast on Old Gods to return to his former self. After killing A.R.G.U.S. agents that were hunting them down, Darkseid and Grail began hunting down and taking the life force of Zeus' demi-god children, killing several including Perseus and Hercules, and growing into the size of a child. After recruiting Jason and luring Wonder Woman to him, Darkseid ages once again into a young man. He fights Wonder Woman himself and as he starts to drain her life force, he is betrayed by Jason. When Zeus appears and transforms into his true form, Darkseid fights the Olympian God, destroying their surroundings in their brawl. When they take a Boom Tube to Manila, Philippines, Zeus grabs onto Darkseid and unleashes bolts of lightning on him. However, Darkseid reveals that he planned for this and that his true target was Zeus himself, and he begins to drain and kill him, restoring Darkseid back to his original self. When the rest of the Justice League arrive, Darkseid decides it is best not to fight them as he does not want to risk revealing his greater plans, and promptly leaves through a Boom Tube with Grail.


title: Darkseid

text: During the "Infinite Frontier" era as a result of the Multiverse being expanded into an Omniverse, Darkseid is trapped in Earth-Omega. He regained his original form by fusing with all his various selves across the multiverse which he declares are all lesser Darkseid. Without an alternate in any other universe he becomes Prime Darkseid. Darkseid's former henchmen eventually reunite with him on Earth-Omega and remain by his side as he gains a new follower named X-Tract (a version of Cameron Chase from the original Earth-Two).


title: Darkseid

text: As a New God, Darkseid is among the most powerful beings in the DC Universe, with immortality, immense strength, and many abilities.


title: Darkseid

text: His best-known and most-used ability is shooting Omega Beams from his eyes. Powered by a cosmic energy source called the "Omega Effect", the beams are an intense form of heated energy that can act as a concussive force, can disintegrate organisms or objects, can cause a target to have never existed, and can resurrect fallen beings killed by them. During the Final Crisis, Darkseid used his Omega Beams to grant power to Mary Marvel, and her powers afterwards were based on Anti-Life rather than magic. Darkseid has pinpoint control of this energy, and can direct the beams to travel in straight lines, curve around corners, and even pass through matter or other forms of energy. Some super-powered beings, such as Superman and Doomsday, can resist the Beams, although in the case of Superman, with a great deal of pain. Orion and Diana were able to deflect them, Firestorm once used his powers to redirect them, and, in a crossover story, Galactus was unaffected by them. Darkseid sometimes uses the beams to punish those who fail him but are too valuable to kill outright.


title: Darkseid

text: His Omega Sanction traps organisms in a series of alternate realities in which they die. Upon their death, they are resurrected in a new reality, in which they die in a worse and more painful manner than the previous.


title: Darkseid

text: Darkseid is depicted as immensely strong. He has effortlessly broken a Green Lantern Ring with his bare hands, easily overpowered two Kryptonians at once, and defeated the entire Justice League. He can move with great speed, once catching Superman off guard, and can react in nanoseconds. Even without his full power and strength, Darkseid has held his own against an Olympian God such as Zeus. He can increase his physical size, his true form as a New God being almost incomprehensibly massive.


title: Darkseid

text: In "The Great Darkness Saga", Darkseid displayed a range of deity-like powers, such as transposing the positions of two planets in different solar systems, taking mental control of the entire population of a planet, instantly absorbing all the information from another being's mind, pronouncing a curse, manifesting the worst fears of other beings as realities, and easily defeating incredibly powerful beings such as Mon-El, Mordru, and the Time Trapper. He has also displayed godly abilities by sensing the death of his son Orion and fluctuations of the energy of the "Godwave".


title: Darkseid

text: Darkseid is a highly skilled hand-to-hand combatant who has been trained in the art of war on Apokolips. Combining his superhuman powers with his combat skills makes him one of the strongest beings in the DC Universe. He is proficient in the use of various weapons, even though he rarely uses them due to other powers like the Omega Beams.


title: Darkseid

text: Despite Darkseid's extraordinary physical powers, he rarely engages himself personally in confrontations, as he prefers to use his superhuman intellect to manipulate or control others to his ends.


title: Darkseid

text: While Darkseid is a deity and immortal, having lived for several hundred thousand years, he is not invincible and has been killed on several occasions. Darkseid is able to drain the life force of other godly beings to rejuvenate himself or return to his full power. Demi-gods are capable of slowly rejuvenating Darkseid, but a god (such as Zeus) can return Darkseid back to his original form by draining the demi-gods.


title: Darkseid

text: Darkseid makes his first official appearance in Chapter 22 of the "" comic on Apokolips. He is seen overseeing the torture of an unseen figure as his son Kalibak approaches him. Kalibak informs his father of Superman's worldwide ceasefire on Earth. Darkseid muses if Superman has begun to soften before Kalibak asks to take a war party to personally investigate. When Kalibak sees just who it is Darkseid is torturing, the lord of Apokolips confirms the man's identity before saying, "He made a mistake." When Kalibak asks if he can be killed, Darkseid chides his son, "Of course not. Who would come for him?" He then allows Kalibak to go, bidding him to kill the Kryptonian and take the Earth. Darkseid grins to himself as he asks to be left alone with his prisoner: Black Racer, death himself, as Darkseid resumes his torture. In the Injustice Annual, Darkseid hires the bounty hunter Lobo to go to Earth and kill Superman in retaliation for the death of Kalibak at the Man of Steel's hands. However, Lobo returns some time later after a 'therapy' session with Harley Quinn, and brazenly challenges the Dread Lord to a battle. Later, under Darkseid's command, Ares manipulates the Justice League into battle with the Greek Gods. The attempt, while initially successful, is defused by Batman and Highfather's intervention. The Greek Gods depart with no further conflict and Superman brings Ares to Darkseid to torture in exchange for Darkseid, Ares and their underlings to "never step foot on Earth."


title: Darkseid

text: In a crossover comic "Injustice vs. Masters of the Universe" Darkseid and the forces of Apokolips invaded Earth and Eternia to take the Power of Grayskull for themselves and reach the Nexus of All Realities. There, with his Soul Siphon (a pseudo-Infinity Gauntlet) and the Anti-Life Equation, Darkseid planned to rewrite and enslave a new reality. It turned out that Skeletor was working with Darkseid all this time since he also wanted to enter Castle Grayskull. He secretly co-opted the power of Shazam to make his own power sword, and he did battle with Darkseid to control the Nexus. As Darkseid breaks into Castle Grayskull, and prepares to use the Anti-Life Equation, along with the Sorceress of Eternia's Orb of Power, to poison the multiverse, Skeletor betrays him and attacks. He's now powered up, a la Black Adam, because of the Rock of Eternity, and he wants all of that power for himself. However, Darkseid proves too mighty, and pummels the dark wizard, beating him into submission for his treachery. With the help of Supergirl and Batman and Superman, He-Man's crew and the League defeat Darkseid's forces and the residual legion Skeletor had there occupying the lands. That provides a window of opportunity for Superman to fly in and blindside the ruler of Apokolips. With the villain's focus is on Superman, He-Man ambushes the New God, and stabs him in the chest with his inactive Sword of Power, which penetrates Darkseid's armor. Instead of being a full-blown killing stroke on the physical plane, it actually strips Darkseid's essence from reality and turns him into knowledge, which the elders of Grayskull store within the castle. Superman looks on as Darkseid withers away into the abyss, becoming the very thing he sought. After Darkseid death Superman betrayed everyone and killed Skeletor to seize the ultimate power for himself and takes up the sword/orb, puts on Darkseid's Soul Syphon and prepares to step into the Nexus of All Realities. He-Man returned to face the Man of Steel, and with his Eldritch magic, he disintegrated the Kryptonian and helped save all realms. Eternia was at peace again with Sorceress and Zatanna working to ensure no future threats like Skeletor or Darkseid arose.


title: Darkseid

text: Darkseid was ranked as the sixth Greatest Comic Book Villain of All Time by IGN and the 23rd Greatest Villain of All Time by "Wizard" magazine.


title: Tower Bridge

text: Tower Bridge is a Grade I listed combined bascule and suspension bridge in London, built between 1886 and 1894, designed by Horace Jones and engineered by John Wolfe Barry with the help of Henry Marc Brunel. It crosses the River Thames close to the Tower of London and is one of five London bridges owned and maintained by the Bridge House Estates, a charitable trust founded in 1282. The bridge was constructed to give better access to the East End of London, which had expanded its commercial potential in the 19th century. The bridge was opened by Edward, Prince of Wales and Alexandra, Princess of Wales in 1894.


title: Tower Bridge

text: The bridge is in length and consists of two bridge towers connected at the upper level by two horizontal walkways, and a central pair of bascules that can open to allow shipping. Originally hydraulically powered, the operating mechanism was converted to an electro-hydraulic system in 1972. The bridge is part of the London Inner Ring Road and thus the boundary of the London congestion charge zone, and remains an important traffic route with 40,000 crossings every day. The bridge deck is freely accessible to both vehicles and pedestrians, whereas the bridge's twin towers, high-level walkways and Victorian engine rooms form part of the Tower Bridge Exhibition.


title: Tower Bridge

text: Tower Bridge has become a recognisable London landmark. It is sometimes confused with London Bridge, about upstream, which has led to a persistent urban legend about an American purchasing the wrong bridge.


title: Tower Bridge

text: In the late 19th century, commercial development in the East End of London increased, leading to demand for a new river crossing downstream of London Bridge. A traditional fixed bridge at street level could not be built because it would cut off access by sailing ships to the port facilities in the Pool of London between London Bridge and the Tower of London.


title: Tower Bridge

text: A "Special Bridge or Subway Committee" chaired by Sir Albert Joseph Altman was formed in 1877 to find a solution. More than fifty designs were submitted, including one from civil engineer Sir Joseph Bazalgette, which was rejected because of a lack of sufficient headroom. A design was not approved until 1884, when it was decided to build a bascule bridge. Sir John Wolfe Barry was appointed engineer and Sir Horace Jones the architect (who was also one of the judges). An Act of Parliament authorising construction was passed in 1885. It specified that the opening span would provide a clear width of and headroom of . The design had to be in a Gothic style. Construction was funded by the Bridge House Estates, a charity established in 1282 for maintenance of London Bridge that subsequently expanded to cover Tower Bridge, Blackfriars Bridge, Southwark Bridge and the Millennium Bridge.


title: Tower Bridge

text: Barry designed a bridge with two bridge towers built on piers. The central span was split into two equal bascules or leaves, which could be raised to allow river traffic to pass. The two side spans were suspension bridges, with rods anchored both at the abutments and through rods contained in the bridge's upper walkways.


title: Tower Bridge

text: Construction started in 1886, with the foundation stone laid by the Prince of Wales on 21 June, and took eight years. Major contractors included Sir John Jackson (foundations), Armstrong, Mitchell and Company (hydraulics), William Webster, and Sir William Arrol & Co. 432 people worked on the site; E W Crutwell was the resident engineer for the construction.


title: Tower Bridge

text: Two piers, containing over of concrete, were sunk into the riverbed to support the construction. More than of steel were used in the framework for the towers and walkways, which were then clad in Cornish granite and Portland stone to protect the underlying steelwork.


title: Tower Bridge

text: Jones died in 1887, and George D. Stevenson took over the project. Stevenson replaced Jones's original brick façade with the more ornate Victorian Gothic style, which made the bridge a distinctive landmark, and was intended to harmonise the bridge with the nearby Tower of London. The total cost of construction was £1,184,000 (equivalent to £ in ).


title: Tower Bridge

text: Tower Bridge was officially opened on 30 June 1894 by the Prince and Princess of Wales. The opening ceremony was attended by the Lord Chamberlain, the Lord Carrington and the Home Secretary, H. H. Asquith. An Act of Parliament stipulated that a tug boat should be on station to assist vessels in danger when crossing the bridge, a requirement that remained in place until the 1960s.


title: Tower Bridge

text: The bridge connected Iron Gate, on the north bank of the river, with Lane, on the south – now known as Tower Bridge Approach and Tower Bridge Road, respectively. Until the bridge was opened, the Tower Subway – to the west – was the shortest way to cross the river from Tower Hill to Tooley Street in Southwark. Opened in 1870, Tower Subway was among the world's earliest underground ("tube") railways, but it closed after just three months and was reopened as a tolled pedestrian foot tunnel. Once Tower Bridge was open, the majority of foot traffic transferred to using the bridge, as there was no toll to cross. Having lost most of its income, the tunnel was closed in 1898.


title: Tower Bridge

text: The high-level open-air walkways between the towers gained a reputation for prostitutes and pickpockets. Since they were only accessible by stairs, the walkways were seldom used by regular pedestrians and were closed in 1910. The walkway reopened in 1982 as part of the Tower Bridge Exhibition.


title: Tower Bridge

text: During the Second World War, Tower Bridge was seen as a major transport link to the Port of London, and consequently was a target for enemy action. In 1940, the high-level span took a direct hit, severing the hydraulic mechanism and taking the bridge out of action. In April 1941, a parachute mine exploded close to the bridge, causing serious damage to the bascule, towers and engine room. In 1942, a third engine was installed in case the existing ones were damaged by enemy action. It was a 150 hp horizontal cross-compound engine, built by Vickers Armstrong Ltd. at their Elswick works in Newcastle upon Tyne. It was fitted with a flywheel having a diameter and weighing 9 tons, and was governed to a speed of 30 rpm. The engine became redundant when the rest of the system was modernised in 1974, and was donated to the Forncett Industrial Steam Museum by the City of London Corporation.


title: Tower Bridge

text: The southern section of the bridge, in the London Borough of Southwark, was Grade I listed on 6 December 1949. The remainder of the bridge, in the London Borough of Tower Hamlets, was listed on 27 September 1973. In 1974, the original operating mechanism was largely replaced by a new electro-hydraulic drive system, designed by BHA Cromwell House, with the original final pinions driven by modern hydraulic motors.


title: Tower Bridge

text: In 1982, the Tower Bridge Exhibition opened, housed in the bridge's twin towers, the long-closed high-level walkways and the Victorian engine rooms. The latter still house the original steam engines and some of the original hydraulic machinery.


title: Tower Bridge

text: The bridge closed for a month in 2000 to repair the bascules and perform other maintenance. A computer system was installed to control the raising and lowering of the bascules remotely. However, the system proved unreliable, resulting in the bridge being stuck in the open or closed positions on several occasions during 2005 until its sensors were replaced.


title: Tower Bridge

text: In April 2008, authorities announced that the bridge would undergo a £4 million refurbishment that would take four years to complete. The work entailed stripping existing paint down to bare metal and repainting in blue and white. Before this, the bridge's colour scheme dated from 1977, when it was painted red, white and blue for Queen Elizabeth II's Silver Jubilee. Its colours were subsequently restored to blue and white. Each section was enshrouded in scaffolding and plastic sheeting to prevent the old paint falling into the Thames and causing pollution. Starting in mid-2008, contractors worked on a quarter of the bridge at a time to minimise disruption, but some road closures were inevitable. The completed work should stand for 25 years. The renovation of the walkway interior was completed in mid-2009. The renovation of the four suspension chains was completed in March 2010 using a state-of-the-art coating system requiring up to six different layers of paint. A lighting system based on RGB LED luminaires was installed, concealed within the bridge superstructure and attached without drilling holes, owing to the bridge's Grade I listing.


title: Tower Bridge

text: On 8 July 2012, as part of the London Olympics, the west walkway was transformed into a Live Music Sculpture by the British composer Samuel Bordoli. 30 classical musicians were arranged along the length of the bridge above the Thames behind the Olympic rings. The sound travelled backwards and forwards along the walkway, echoing the structure of the bridge.


title: Tower Bridge

text: Following the Olympics, the rings were removed from Tower Bridge and replaced by the emblem of the Paralympic Games for the 2012 Summer Paralympics.


title: Tower Bridge

text: In 2016, Tower Bridge was closed to all road traffic from 1 October to 30 December. This was to allow structural maintenance work to take place on the timber decking, lifting mechanism and waterproofing the brick arches on the bridge's approaches. During this, the bridge was still open to waterborne traffic. It was open to pedestrians for all but three weekends, when a free ferry service was in operation.


title: Tower Bridge

text: The bridge is in length with two towers each high, built on piers. The central span of between the towers is split into two equal bascules, or leaves, which can be raised to an angle of 86 degrees to allow river traffic to pass. The bascules, weighing over 1,000 tons each, are counterbalanced to minimise the force required and allow raising in five minutes.


title: Tower Bridge

text: The two side spans are suspension bridges, each long, with the suspension rods anchored both at the abutments and through rods contained within the bridge's upper walkways. The pedestrian walkways are above the river at high tide, and accessed by lifts and staircases.


title: Tower Bridge

text: One of the chimneys on the bridge connects up to an old fireplace in a guardroom of the Tower of London. It is long-disused.


title: Tower Bridge

text: The original raising mechanism was powered by pressurised water stored in several hydraulic accumulators. The system was designed and installed by Hamilton Owen Rendel while working for Armstrong, Mitchell and Company of Newcastle upon Tyne. Water at a pressure of was pumped into the accumulators by a pair of stationary steam engines. Each drove a force pump from its piston tail rod. The accumulators each comprise a ram on which sits a very heavy weight to maintain the desired pressure.


title: Tower Bridge

text: The entire hydraulic system along with the gas lighting system was installed by William Sugg & Co Ltd. The gas lighting was initially by open-flame burners within the lanterns, but was soon updated to the later incandescent system.


title: Tower Bridge

text: In 1974, the original operating mechanism was largely replaced by a new electro-hydraulic drive system, designed by BHA Cromwell House. The only remaining parts of the old system are the final pinions, which fit into the racks on the bascules and were driven by hydraulic motors and gearing. Oil is now used in place of water as the new hydraulic fluid.


title: Tower Bridge

text: Originally, river traffic passing beneath the bridge was required to follow a number of rules and signals. Daytime control was provided by red semaphore signals, mounted on small control cabins on either end of both of the bridge piers. At night, coloured lights were used, in either direction, on both of the piers: two red lights to show that the bridge was closed, and two green to show that it was open. In foggy weather, a gong was sounded as well.


title: Tower Bridge

text: Vessels passing through the bridge were required to display signals. By day, a black ball at least in diameter was mounted high up where it could be seen. Night passage called for two red lights in the same position. Foggy weather required repeated blasts from the ship's steam whistle. If a black ball was suspended from the middle of each walkway (or a red light at night) this indicated that the bridge could not be opened. These signals were repeated about downstream, at Cherry Garden Pier, where boats needing to pass through the bridge had to hoist their signals/lights and sound their horn, as appropriate, to alert the Bridge Master.


title: Tower Bridge

text: Some of the control mechanism for the signalling equipment has been preserved and is housed in the Tower Bridge's museum.


title: Tower Bridge

text: Tower Bridge is still a busy crossing of the Thames, used by more than 40,000 people (motorists, cyclists and pedestrians) every day. The bridge is on the London Inner Ring Road, and is on the eastern boundary of the London congestion charge zone (drivers do not incur the charge by crossing the bridge).


title: Tower Bridge

text: To maintain the integrity of the structure, the City of London Corporation has imposed a speed restriction, and an weight limit on vehicles using the bridge. A camera system measures the speed of traffic crossing the bridge, using a number plate recognition system to send fixed penalty charges to speeding drivers.


title: Tower Bridge

text: A second system monitors other vehicle parameters. Induction loops and piezoelectric sensors are used to measure the weight, the height of the chassis above ground level, and the number of axles of each vehicle, with drivers of overweight vehicles also receiving fixed penalty notices.


title: Tower Bridge

text: From the outset, the high-level connection was a pedestrian route and was intended to allow pedestrian movement to continue while the bridge was open. This was closed in 1910 due to growing crime in this hidden area, but was reopened in 1982 when a glass floor was also installed.


title: Tower Bridge

text: The bascules are raised about a thousand times a year. River traffic is now much reduced, but it still takes priority over road traffic. Today, 24 hours' notice is required before opening the bridge, and opening times are published in advance on the bridge's website; there is no charge for vessels to open the bridge.


title: Tower Bridge

text: The nearest London Underground tube stations to Tower Bridge are Tower Hill on the Circle and District lines, London Bridge on the Jubilee and Northern lines and Bermondsey on the Jubilee line, and the nearest Docklands Light Railway station is Tower Gateway. The nearest National Rail stations are at Fenchurch Street and London Bridge.


title: Tower Bridge

text: The Tower Bridge Exhibition is a display housed in the bridge's twin towers, the high-level walkways and the Victorian engine rooms. It uses films, photos and interactive displays to explain why and how Tower Bridge was built. Visitors can access the original steam engines that once powered the bridge bascules, housed in a building close to the south end of the bridge.


title: Tower Bridge

text: The exhibition charges an admission fee. Entrance is from the west side of the bridge deck to the northern tower, from where visitors ascend to level 4 by lift before crossing the high-level walkways to the southern tower. In the towers and walkways is an exhibition on the history of the bridge. The walkways also provide views over the city, the Tower of London and the Pool of London, and include a glass-floored section. From the south tower, visitors can visit the engine rooms, with the original steam engines, which are situated in a separate building beside the southern approach to the bridge.


title: Tower Bridge

text: Although Tower Bridge is an undoubted landmark, professional commentators in the early 20th century were critical of its aesthetics. "It represents the vice of tawdriness and pretentiousness, and of falsification of the actual facts of the structure", wrote Henry Heathcote Statham, while Frank Brangwyn stated that "A more absurd structure than the Tower Bridge was never thrown across a strategic river".


title: Tower Bridge

text: Benjamin Crisler, the "New York Times" film critic, wrote in 1938: "Three unique and valuable institutions the British have that we in America have not: Magna Carta, the Tower Bridge and Alfred Hitchcock." Architectural historian Dan Cruickshank selected Tower Bridge as one of his four choices for the 2002 BBC television documentary series "Britain's Best Buildings". The bridge and its surrounding landscape was depicted in an official BBC trailer for the 2021 Rugby League World Cup (in reference to London being one of the host cities).


title: Tower Bridge

text: Tower Bridge has been mistaken for the next bridge upstream, London Bridge. A popular urban legend is that in 1968, Robert P. McCulloch, the purchaser of the old London Bridge that was later shipped to Lake Havasu City in Arizona, believed that he was in fact buying Tower Bridge. This was denied by McCulloch himself and has been debunked by Ivan Luckin, the vendor of the bridge.


title: Tower Bridge

text: A partial replica of Tower Bridge has been built in the city of Suzhou in China. The replica differs from the original in having no lifting mechanism and four separate towers. The Suzhou replica was renovated in 2019, giving it a new look that differs from the original London design.


title: Tower Bridge

text: On 10 August 1912, the pioneering stunt pilot Francis McClean flew between the bascules and the high-level walkways in his Short Brothers S.33 floatplane. McClean became a celebrity overnight because of the stunt, and went on to fly underneath London Bridge, Blackfriars Bridge and Waterloo Bridge.


title: Tower Bridge

text: On 3 August 1922, a 13-year-old boy fell off a slipway next to the south side of Tower Bridge. A man jumped into the Thames to save him, but both were pulled under a barge by Butler's Wharf and drowned.


title: Tower Bridge

text: In December 1952, the bridge opened while a number 78 double-decker bus was crossing from the south bank. At that time, the gateman would ring a warning bell and close the gates when the bridge was clear before the watchman ordered the raising of the bridge. The process failed while a relief watchman was on duty. The bus was near the edge of the south bascule when it started to rise; driver Albert Gunter made a split-second decision to accelerate, clearing a gap to drop onto the north bascule, which had not yet started to rise. There were no serious injuries. Gunter was given £10 (equivalent to £ in ) by the City Corporation to honour his act of bravery.


title: Tower Bridge

text: On 5 April 1968, a Royal Air Force Hawker Hunter FGA.9 jet fighter from No. 1 Squadron made an unauthorised flight through Tower Bridge. Unimpressed that senior staff were not going to celebrate the RAF's 50th birthday with a flypast, the pilot flew at low altitude down the Thames without authorisation, past the Houses of Parliament, and continued on towards the bridge. He flew beneath the walkway, at an estimated . He was placed under arrest upon landing, and discharged from the RAF on medical grounds without the chance to defend himself at a court martial.


title: Tower Bridge

text: On 31 July 1973, a single-engined Beagle Pup was twice flown under the pedestrian walkway of Tower Bridge by 29-year-old stockbroker's clerk Peter Martin. Martin, who was on bail following accusations of stock market fraud, then "buzzed" buildings in the city before flying north towards the Lake District, where he died when his aircraft crashed some two hours later.


title: Tower Bridge

text: In May 1997, the motorcade of United States President Bill Clinton was divided by the opening of the bridge. The Thames sailing barge "Gladys", on her way to a gathering at St Katharine Docks, arrived on schedule and the bridge was opened for her. Returning from a Thames-side lunch at "Le Pont de la Tour" restaurant with UK Prime Minister Tony Blair, President Clinton was less punctual and arrived just as the bridge was rising. The bridge opening split the motorcade in two, much to the consternation of security staff. A spokesman for Tower Bridge is quoted as saying: "We tried to contact the American Embassy, but they wouldn't answer the phone."


title: Tower Bridge

text: On 19 August 1999, Jef Smith, a Freeman of the City of London, drove a flock of two sheep across the bridge. He was exercising a claimed ancient permission, granted as a right to freemen, to make a point about the powers of older citizens and the way their rights were being eroded.


title: Tower Bridge

text: Before dawn on 31 October 2003, a Fathers 4 Justice campaigner climbed a tower crane near Tower Bridge at the start of a six-day protest dressed as Spider-Man. Fearing for his safety, and that of motorists should he fall, police cordoned off the area, closing the bridge and surrounding roads and causing widespread traffic congestion across the City and East London.


title: Tower Bridge

text: On 9 August 2021, the bridge remained open after a technical failure. The bridge had opened to let the Jubilee Trust Tall Ship through from 2 p.m. before getting stuck. The bridge was closed and reopened to traffic approximately 12 hours later.


title: Telecommunications

text: Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that feasible with the human voice, but with a similar scale of expediency; thus, slow systems (such as postal mail) are excluded from the field.


title: Telecommunications

text: The transmission media in telecommunication have evolved through numerous stages of technology, from beacons and other visual signals (such as smoke signals, semaphore telegraphs, signal flags, and optical heliographs), to electrical cable and electromagnetic radiation, including light. Such transmission paths are often divided into communication channels, which afford the advantages of multiplexing multiple concurrent communication sessions. "Telecommunication" is often used in its plural form.


title: Telecommunications

text: Other examples of pre-modern long-distance communication included audio messages, such as coded drumbeats, lung-blown horns, and loud whistles. 20th- and 21st-century technologies for long-distance communication usually involve electrical and electromagnetic technologies, such as telegraph, telephone, television and teleprinter, networks, radio, microwave transmission, optical fiber, and communications satellites.


title: Telecommunications

text: A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909, and other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included Charles Wheatstone and Samuel Morse (inventors of the telegraph), Antonio Meucci and Alexander Graham Bell (some of the inventors and developers of the telephone, see Invention of the telephone), Edwin Armstrong and Lee de Forest (inventors of radio), as well as Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth (some of the inventors of television).


title: Telecommunications

text: According to "Article 1.3" of the Radio Regulations (RR), telecommunication is defined as "« Any transmission, emission or reception of signs, signals, writings, images and sounds or intelligence of any nature by wire, radio, optical, or other electromagnetic systems".» This definition is identical to those contained in the Annex to the Constitution and Convention of the International Telecommunication Union (Geneva, 1992).


title: Telecommunications

text: The early telecommunication networks were created with copper wires as the physical medium for signal transmission. For many years, these networks were used for basic phone services, namely voice and telegrams. Since the mid-1990s, as the internet has grown in popularity, voice has been gradually supplanted by data. This soon demonstrated the limitations of copper in data transmission, prompting the development of optics.


title: Telecommunications

text: The word "telecommunication" is a compound of the Greek prefix "tele-" (τῆλε), meaning "distant", "far off", or "afar", and the Latin "communicare", meaning "to share". Its modern use is adapted from the French, because its written use was recorded in 1904 by the French engineer and novelist Édouard Estaunié. "Communication" was first used as an English word in the late 14th century. It comes from Old French comunicacion (14c., Modern French communication), from Latin communicationem (nominative communicatio), noun of action from past participle stem of communicare, "to share, divide out; communicate, impart, inform; join, unite, participate in," literally, "to make common," from communis."


title: Telecommunications

text: Homing pigeons have been used throughout history by different cultures. Pigeon post had Persian roots and was later used by the Romans to aid their military. Frontinus claimed Julius Caesar used pigeons as messengers in his conquest of Gaul.


title: Telecommunications

text: The Greeks also conveyed the names of the victors at the Olympic Games to various cities using homing pigeons. In the early 19th century, the Dutch government used the system in Java and Sumatra. And in 1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels, a service that operated for a year until the gap in the telegraph link was closed.


title: Telecommunications

text: In the Middle Ages, chains of beacons were commonly used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use was during the Spanish Armada, when a beacon chain relayed a signal from Plymouth to London.


title: Telecommunications

text: In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system (or semaphore line) between Lille and Paris. However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres (six to nineteen miles). As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880.


title: Telecommunications

text: On July 25, 1837, the first commercial electrical telegraph was demonstrated by English inventor Sir William Fothergill Cooke and English scientist Sir Charles Wheatstone. Both inventors viewed their device as "an improvement to the [existing] electromagnetic telegraph" and not as a new device.


title: Telecommunications

text: Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on September 2, 1837. His code was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable was successfully completed on July 27, 1866, allowing transatlantic telecommunication for the first time.


title: Telecommunications

text: The conventional telephone was patented by Alexander Bell in 1876. Elisha Gray also filed a caveat for it in 1876. Gray abandoned his caveat and because he did not contest Bell's priority, the examiner approved Bell's patent on March 3, 1876. Gray had filed his caveat for the variable resistance telephone, but Bell was the first to document the idea and test it in a telephone.[88] Antonio Meucci invented a device that allowed the electrical transmission of voice over a line nearly 30 years before in 1849, but his device was of little practical value because it relied on the electrophonic effect requiring users to place the receiver in their mouths to "hear." The first commercial telephone services were set up by the Bell Telephone Company in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London.


title: Telecommunications

text: In 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using the then-newly discovered phenomenon of radio waves, showing by 1901 that they could be transmitted across the Atlantic Ocean. This was the start of wireless telegraphy by radio. On 17 December 1902, a transmission from the Marconi station in Glace Bay, Nova Scotia, Canada, became the world's first radio message to cross the Atlantic from North America. In 1904, a commercial service was established to transmit nightly news summaries to subscribing ships, which incorporated them into their onboard newspapers.


title: Telecommunications

text: World War I accelerated the development of radio for military communications. After the war, commercial radio AM broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated the development of radio for the wartime purposes of aircraft and land communication, radio navigation, and radar. Development of stereo FM broadcasting of radio began in the 1930s in the United States and the 1970s in the United Kingdom, displacing AM as the dominant commercial standard.


title: Telecommunications

text: On March 25, 1925, John Logie Baird demonstrated the transmission of moving pictures at the London department store Selfridges. Baird's device relied upon the Nipkow disk and thus became known as the mechanical television. It formed the basis of experimental broadcasts done by the British Broadcasting Corporation beginning on 30 September 1929. However, for most of the 20th century, televisions depended on the cathode ray tube invented by Karl Braun. The first version of such a television to show promise was produced by Philo Farnsworth and demonstrated to his family on 7 September 1927. After World War II, interrupted experiments resumed and television became an important home entertainment broadcast medium.


title: Telecommunications

text: The type of device known as a "thermionic tube" or "thermionic valve" uses thermionic emission of electrons from a heated cathode for a number of fundamental electronic functions such as signal amplification and current rectification.


title: Telecommunications

text: The simplest vacuum tube, the diode invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—from the cathode to the anode. Adding one or more control grids within the tube enables the current between the cathode and anode to be controlled by the voltage on the grid or grids. These devices became a key component of electronic circuits for the first half of the 20th century and were crucial to the development of radio, television, radar, sound recording and reproduction, long-distance telephone networks, and analogue and early digital computers. While some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, leading to the creation of electronics.


title: Telecommunications

text: In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, cheaper, and more efficient, reliable, and durable than thermionic tubes. Starting in the mid-1960s, thermionic tubes were replaced with the transistor. Thermionic tubes still have some applications for certain high-frequency amplifiers.


title: Telecommunications

text: On 11 September 1940, George Stibitz transmitted problems for his Complex Number Calculator in New York using a teletype and received the computed results back at Dartmouth College in New Hampshire. This configuration of a centralized computer (mainframe) with remote dumb terminals remained popular well into the 1970s. In the 1960s, researchers started to investigate packet switching, a technology that sends a message in portions to its destination asynchronously without passing it through a centralized mainframe. A four-node network emerged on 5 December 1969, constituting the beginnings of the ARPANET, which by 1981 had grown to 213 nodes. ARPANET eventually merged with other networks to form the Internet. While Internet development was a focus of the Internet Engineering Task Force (IETF) who published a series of Request for Comments documents, other networking advancements occurred in industrial laboratories, such as the local area network (LAN) developments of Ethernet (1983) and Token Ring (1984).


title: Telecommunications

text: The effective capacity to exchange information worldwide through two-way telecommunication networks grew from 281 petabytes (pB) of optimally compressed information in 1986 to 471 pB in 1993 to 2.2 exabytes (eB) in 2000 to 65 eB in 2007. This is the informational equivalent of two newspaper pages per person per day in 1986, and six entire newspapers per person per day by 2007. Given this growth, telecommunications play an increasingly important role in the world economy and the global telecommunications industry was about a $4.7 trillion sector in 2012. The service revenue of the global telecommunications industry was estimated to be $1.5 trillion in 2010, corresponding to 2.4% of the world's gross domestic product (GDP).


title: Telecommunications

text: Modern telecommunication is founded on a series of key concepts that experienced progressive development and refinement in a period of well over a century:


title: Telecommunications

text: Telecommunication technologies may primarily be divided into wired and wireless methods. Overall, a basic telecommunication system consists of three main parts that are always present in some form or another:


title: Telecommunications

text: In a radio broadcasting station, the station's large power amplifier is the transmitter and the broadcasting antenna is the interface between the power amplifier and the free space channel. The free space channel is the transmission medium and the receiver's antenna is the interface between the free space channel and the receiver. Next, the radio receiver is the destination of the radio signal, where it is converted from electricity to sound.


title: Telecommunications

text: Telecommunication systems are occasionally "duplex" (two-way systems) with a single box of electronics working as both the transmitter and a receiver, or a "transceiver" (e.g., a mobile phone). The transmission electronics and the receiver electronics within a transceiver are quite independent of one another. This can be explained by the fact that radio transmitters contain power amplifiers that operate with electrical powers measured in watts or kilowatts, but radio receivers deal with radio powers measured in microwatts or nanowatts. Hence, transceivers have to be carefully designed and built to isolate their high-power circuitry and their low-power circuitry from each other to avoid interference.


title: Telecommunications

text: Telecommunication over fixed lines is called point-to-point communication because it occurs between a transmitter and a receiver. Telecommunication through radio broadcasts is called broadcast communication because it occurs between a powerful transmitter and numerous low-power but sensitive radio receivers.


title: Telecommunications

text: Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and share the same physical channel are called multiplex systems. The sharing of physical channels using multiplexing often results in significant cost reduction. Multiplexed systems are laid out in telecommunication networks and multiplexed signals are switched at nodes through to the correct destination terminal receiver.


title: Telecommunications

text: Communications signals can be sent by analog signals or digital signals via analog communication systems or digital communication systems. Analog signals vary continuously with respect to the information, while digital signals encode information as a set of discrete values (e.g., a set of ones and zeroes). During propagation and reception, information contained in analog signals is degraded by undesirable physical noise. Commonly, the noise in a communication system can be expressed as adding or subtracting from the desirable signal in a random way. This form of noise is called additive noise, with the understanding that the noise can be negative or positive at different instances.


title: Telecommunications

text: Unless the additive noise disturbance exceeds a certain threshold, the information contained in digital signals will remain intact. Their resistance to noise represents a key advantage of digital signals over analog signals. However, digital systems fail catastrophically when noise exceeds the system's ability to autocorrect. On the other hand, analog systems fail gracefully: as noise increases, the signal becomes progressively more degraded but still usable. Also, digital transmission of continuous data unavoidably adds quantization noise to the output. This can be reduced, but not entirely eliminated, only at the expense of increasing the channel bandwidth requirement.


title: Telecommunications

text: The term "channel" has two different meanings. In one meaning, a channel is the physical medium that carries a signal between the transmitter and the receiver. Examples of this include the atmosphere for sound communications, glass optical fibers for some kinds of optical communications, coaxial cables for communications by way of the voltages and electric currents in them, and free space for communications using visible light, infrared waves, ultraviolet light, and radio waves. Coaxial cable types are classified by RG type or "radio guide", terminology derived from World War II. The various RG designations are used to classify the specific signal transmission applications. This last channel is called the "free space channel". The sending of radio waves from one place to another has nothing to do with the presence or absence of an atmosphere between the two. Radio waves travel through a perfect vacuum just as easily as they travel through air, fog, clouds, or any other kind of gas.


title: Telecommunications

text: The other meaning of the term "channel" in telecommunications is seen in the phrase communications channel, which is a subdivision of a transmission medium so that it can be used to send multiple streams of information simultaneously. For example, one radio station can broadcast radio waves into free space at frequencies in the neighborhood of 94.5 MHz (megahertz) while another radio station can simultaneously broadcast radio waves at frequencies in the neighborhood of 96.1 MHz. Each radio station would transmit radio waves over a frequency bandwidth of about 180 kHz (kilohertz), centered at frequencies such as the above, which are called the "carrier frequencies". Each station in this example is separated from its adjacent stations by 200 kHz, and the difference between 200 kHz and 180 kHz (20 kHz) is an engineering allowance for the imperfections in the communication system.


title: Telecommunications

text: In the example above, the "free space channel" has been divided into communications channels according to frequencies, and each channel is assigned a separate frequency bandwidth in which to broadcast radio waves. This system of dividing the medium into channels according to frequency is called "frequency-division multiplexing". Another term for the same concept is "wavelength-division multiplexing", which is more commonly used in optical communications when multiple transmitters share the same physical medium.


title: Telecommunications

text: Another way of dividing a communications medium into channels is to allocate each sender a recurring segment of time (a "time slot", for example, 20 milliseconds out of each second), and to allow each sender to send messages only within its own time slot. This method of dividing the medium into communication channels is called "time-division multiplexing" (TDM), and is used in optical fibre communication. Some radio communication systems use TDM within an allocated FDM channel. Hence, these systems use a hybrid of TDM and FDM.


title: Telecommunications

text: The shaping of a signal to convey information is known as modulation. Modulation can be used to represent a digital message as an analog waveform. This is commonly called "keying"—a term derived from the older use of Morse Code in telecommunications—and several keying techniques exist (these include phase-shift keying, frequency-shift keying, and amplitude-shift keying). The "Bluetooth" system, for example, uses phase-shift keying to exchange information between various devices. In addition, there are combinations of phase-shift keying and amplitude-shift keying which is called (in the jargon of the field) "quadrature amplitude modulation" (QAM) that are used in high-capacity digital radio communication systems.


title: Telecommunications

text: Modulation can also be used to transmit the information of low-frequency analog signals at higher frequencies. This is helpful because low-frequency analog signals cannot be effectively transmitted over free space. Hence the information from a low-frequency analog signal must be impressed into a higher-frequency signal (known as the "carrier wave") before transmission. There are several different modulation schemes available to achieve this [two of the most basic being amplitude modulation (AM) and frequency modulation (FM)]. An example of this process is a disc jockey's voice being impressed into a 96 MHz carrier wave using frequency modulation (the voice would then be received on a radio as the channel "96 FM"). In addition, modulation has the advantage that it may use frequency division multiplexing (FDM).


title: Telecommunications

text: A telecommunications network is a collection of transmitters, receivers, and communications channels that send messages to one another. Some digital communications networks contain one or more routers that work together to transmit information to the correct user. An analog communications network consists of one or more switches that establish a connection between two or more users. For both types of networks, repeaters may be necessary to amplify or recreate the signal when it is being transmitted over long distances. This is to combat attenuation that can render the signal indistinguishable from the noise.


title: Telecommunications

text: Another advantage of digital systems over analog is that their output is easier to store in memory, i.e. two voltage states (high and low) are easier to store than a continuous range of states.


title: Telecommunications

text: Telecommunication has a significant social, cultural and economic impact on modern society. In 2008, estimates placed the telecommunication industry's revenue at US$4.7 trillion or just under three percent of the gross world product (official exchange rate). Several following sections discuss the impact of telecommunication on society.


title: Telecommunications

text: On the microeconomic scale, companies have used telecommunications to help build global business empires. This is self-evident in the case of online retailer Amazon.com but, according to academic Edward Lenert, even the conventional retailer Walmart has benefited from better telecommunication infrastructure compared to its competitors. In cities throughout the world, home owners use their telephones to order and arrange a variety of home services ranging from pizza deliveries to electricians. Even relatively poor communities have been noted to use telecommunication to their advantage. In Bangladesh's Narsingdi District, isolated villagers use cellular phones to speak directly to wholesalers and arrange a better price for their goods. In Côte d'Ivoire, coffee growers share mobile phones to follow hourly variations in coffee prices and sell at the best price.


title: Telecommunications

text: On the macroeconomic scale, Lars-Hendrik Röller and Leonard Waverman suggested a causal link between good telecommunication infrastructure and economic growth. Few dispute the existence of a correlation although some argue it is wrong to view the relationship as causal.


title: Telecommunications

text: Because of the economic benefits of good telecommunication infrastructure, there is increasing worry about the inequitable access to telecommunication services amongst various countries of the world—this is known as the digital divide. A 2003 survey by the International Telecommunication Union (ITU) revealed that roughly a third of countries have fewer than one mobile subscription for every 20 people and one-third of countries have fewer than one land-line telephone subscription for every 20 people. In terms of Internet access, roughly half of all countries have fewer than one out of 20 people with Internet access. From this information, as well as educational data, the ITU was able to compile an index that measures the overall ability of citizens to access and use information and communication technologies. Using this measure, Sweden, Denmark and Iceland received the highest ranking while the African countries Nigeria, Burkina Faso and Mali received the lowest.


title: Telecommunications

text: Telecommunication has played a significant role in social relationships. Nevertheless, devices like the telephone system were originally advertised with an emphasis on the practical dimensions of the device (such as the ability to conduct business or order home services) as opposed to the social dimensions. It was not until the late 1920s and 1930s that the social dimensions of the device became a prominent theme in telephone advertisements. New promotions started appealing to consumers' emotions, stressing the importance of social conversations and staying connected to family and friends.


title: Telecommunications

text: Since then the role that telecommunications has played in social relations has become increasingly important. In recent years, the popularity of social networking sites has increased dramatically. These sites allow users to communicate with each other as well as post photographs, events and profiles for others to see. The profiles can list a person's age, interests, sexual preference and relationship status. In this way, these sites can play important role in everything from organising social engagements to courtship.


title: Telecommunications

text: Prior to social networking sites, technologies like short message service (SMS) and the telephone also had a significant impact on social interactions. In 2000, market research group Ipsos MORI reported that 81% of 15- to 24-year-old SMS users in the United Kingdom had used the service to coordinate social arrangements and 42% to flirt.


title: Telecommunications

text: In cultural terms, telecommunication has increased the public's ability to access music and film. With television, people can watch films they have not seen before in their own home without having to travel to the video store or cinema. With radio and the Internet, people can listen to music they have not heard before without having to travel to the music store.


title: Telecommunications

text: Telecommunication has also transformed the way people receive their news. A 2006 survey (right table) of slightly more than 3,000 Americans by the non-profit Pew Internet and American Life Project in the United States the majority specified television or radio over newspapers.


title: Telecommunications

text: Telecommunication has had an equally significant impact on advertising. TNS Media Intelligence reported that in 2007, 58% of advertising expenditure in the United States was spent on media that depend upon telecommunication.


title: Telecommunications

text: Many countries have enacted legislation which conforms to the International Telecommunication Regulations established by the International Telecommunication Union (ITU), which is the "leading UN agency for information and communication technology issues". In 1947, at the Atlantic City Conference, the ITU decided to "afford international protection to all frequencies registered in a new international frequency list and used in conformity with the Radio Regulation". According to the ITU's "Radio Regulations" adopted in Atlantic City, all frequencies referenced in the "International Frequency Registration Board", examined by the board and registered on the "International Frequency List" "shall have the right to international protection from harmful interference".


title: Telecommunications

text: From a global perspective, there have been political debates and legislation regarding the management of telecommunication and broadcasting. The history of broadcasting discusses some debates in relation to balancing conventional communication such as printing and telecommunication such as radio broadcasting. The onset of World War II brought on the first explosion of international broadcasting propaganda. Countries, their governments, insurgents, terrorists, and militiamen have all used telecommunication and broadcasting techniques to promote propaganda. Patriotic propaganda for political movements and colonization started the mid-1930s. In 1936, the BBC broadcast propaganda to the Arab World to partly counter similar broadcasts from Italy, which also had colonial interests in North Africa.


title: Telecommunications

text: Modern insurgents, such as those in the latest Iraq War, often use intimidating telephone calls, SMSs and the distribution of sophisticated videos of an attack on coalition troops within hours of the operation. "The Sunni insurgents even have their own television station, Al-Zawraa, which while banned by the Iraqi government, still broadcasts from Erbil, Iraqi Kurdistan, even as coalition pressure has forced it to switch satellite hosts several times."


title: Telecommunications

text: On 10 November 2014, President Obama recommended the Federal Communications Commission reclassify broadband Internet service as a telecommunications service to preserve net neutrality.


title: Telecommunications

text: According to data collected by Gartner and Ars Technica sales of main consumer's telecommunication equipment worldwide in millions of units was:


title: Telecommunications

text: In a telephone network, the caller is connected to the person to whom they wish to talk by switches at various telephone exchanges. The switches form an electrical connection between the two users and the setting of these switches is determined electronically when the caller dials the number. Once the connection is made, the caller's voice is transformed to an electrical signal using a small microphone in the caller's handset. This electrical signal is then sent through the network to the user at the other end where it is transformed back into sound by a small speaker in that person's handset.


title: Telecommunications

text: As of 2015, the landline telephones in most residential homes are analog—that is, the speaker's voice directly determines the signal's voltage. Although short-distance calls may be handled from end-to-end as analog signals, increasingly telephone service providers are transparently converting the signals to digital signals for transmission. The advantage of this is that digitized voice data can travel side by side with data from the Internet and can be perfectly reproduced in long-distance communication (as opposed to analog signals that are inevitably impacted by noise).


title: Telecommunications

text: Mobile phones have had a significant impact on telephone networks. Mobile phone subscriptions now outnumber fixed-line subscriptions in many markets. Sales of mobile phones in 2005 totalled 816.6 million with that figure being almost equally shared amongst the markets of Asia/Pacific (204 m), Western Europe (164 m), CEMEA (Central Europe, the Middle East and Africa) (153.5 m), North America (148 m) and Latin America (102 m). In terms of new subscriptions over the five years from 1999, Africa has outpaced other markets with 58.2% growth. Increasingly these phones are being serviced by systems where the voice content is transmitted digitally such as GSM or W-CDMA with many markets choosing to deprecate analog systems such as AMPS.


title: Telecommunications

text: There have also been dramatic changes in telephone communication behind the scenes. Starting with the operation of TAT-8 in 1988, the 1990s saw the widespread adoption of systems based on optical fibers. The benefit of communicating with optical fibers is that they offer a drastic increase in data capacity. TAT-8 itself was able to carry 10 times as many telephone calls as the last copper cable laid at that time and today's optical fibre cables are able to carry 25 times as many telephone calls as TAT-8. This increase in data capacity is due to several factors: First, optical fibres are physically much smaller than competing technologies. Second, they do not suffer from crosstalk which means several hundred of them can be easily bundled together in a single cable. Lastly, improvements in multiplexing have led to an exponential growth in the data capacity of a single fibre.


title: Telecommunications

text: Assisting communication across many modern optical fibre networks is a protocol known as Asynchronous Transfer Mode (ATM). The ATM protocol allows for the side-by-side data transmission mentioned in the second paragraph. It is suitable for public telephone networks because it establishes a pathway for data through the network and associates a traffic contract with that pathway. The traffic contract is essentially an agreement between the client and the network about how the network is to handle the data; if the network cannot meet the conditions of the traffic contract it does not accept the connection. This is important because telephone calls can negotiate a contract so as to guarantee themselves a constant bit rate, something that will ensure a caller's voice is not delayed in parts or cut off completely. There are competitors to ATM, such as Multiprotocol Label Switching (MPLS), that perform a similar task and are expected to supplant ATM in the future.


title: Telecommunications

text: In a broadcast system, the central high-powered broadcast tower transmits a high-frequency electromagnetic wave to numerous low-powered receivers. The high-frequency wave sent by the tower is modulated with a signal containing visual or audio information. The receiver is then tuned so as to pick up the high-frequency wave and a demodulator is used to retrieve the signal containing the visual or audio information. The broadcast signal can be either analog (signal is varied continuously with respect to the information) or digital (information is encoded as a set of discrete values).


title: Telecommunications

text: The broadcast media industry is at a critical turning point in its development, with many countries moving from analog to digital broadcasts. This move is made possible by the production of cheaper, faster and more capable integrated circuits. The chief advantage of digital broadcasts is that they prevent a number of complaints common to traditional analog broadcasts. For television, this includes the elimination of problems such as snowy pictures, ghosting and other distortion. These occur because of the nature of analog transmission, which means that perturbations due to noise will be evident in the final output. Digital transmission overcomes this problem because digital signals are reduced to discrete values upon reception and hence small perturbations do not affect the final output. In a simplified example, if a binary message 1011 was transmitted with signal amplitudes [1.0 0.0 1.0 1.0] and received with signal amplitudes [0.9 0.2 1.1 0.9] it would still decode to the binary message 1011— a perfect reproduction of what was sent. From this example, a problem with digital transmissions can also be seen in that if the noise is great enough it can significantly alter the decoded message. Using forward error correction a receiver can correct a handful of bit errors in the resulting message but too much noise will lead to incomprehensible output and hence a breakdown of the transmission.


title: Telecommunications

text: In digital television broadcasting, there are three competing standards that are likely to be adopted worldwide. These are the ATSC, DVB and ISDB standards; the adoption of these standards thus far is presented in the captioned map. All three standards use MPEG-2 for video compression. ATSC uses Dolby Digital AC-3 for audio compression, ISDB uses Advanced Audio Coding (MPEG-2 Part 7) and DVB has no standard for audio compression but typically uses MPEG-1 Part 3 Layer 2. The choice of modulation also varies between the schemes. In digital audio broadcasting, standards are much more unified with practically all countries choosing to adopt the Digital Audio Broadcasting standard (also known as the Eureka 147 standard). The exception is the United States which has chosen to adopt HD Radio. HD Radio, unlike Eureka 147, is based upon a transmission method known as in-band on-channel transmission that allows digital information to "piggyback" on normal AM or FM analog transmissions.


title: Telecommunications

text: However, despite the pending switch to digital, analog television remains being transmitted in most countries. An exception is the United States that ended analog television transmission (by all but the very low-power TV stations) on 12 June 2009 after twice delaying the switchover deadline. Kenya also ended analog television transmission in December 2014 after multiple delays. For analog television, there were three standards in use for broadcasting color TV (see a map on adoption ). These are known as PAL (German designed), NTSC (American designed), and SECAM (French-designed). For analog radio, the switch to digital radio is made more difficult by the higher cost of digital receivers. The choice of modulation for analog radio is typically between amplitude (AM) or frequency modulation (FM). To achieve stereo playback, an amplitude modulated subcarrier is used for stereo FM, and quadrature amplitude modulation is used for stereo AM or C-QUAM.


title: Telecommunications

text: The Internet is a worldwide network of computers and computer networks that communicate with each other using the Internet Protocol (IP). Any computer on the Internet has a unique IP address that can be used by other computers to route information to it. Hence, any computer on the Internet can send a message to any other computer using its IP address. These messages carry with them the originating computer's IP address allowing for two-way communication. The Internet is thus an exchange of messages between computers.


title: Telecommunications

text: It is estimated that 51% of the information flowing through two-way telecommunications networks in the year 2000 were flowing through the Internet (most of the rest (42%) through the landline telephone). By 2007 the Internet clearly dominated and captured 97% of all the information in telecommunication networks (most of the rest (2%) through mobile phones). , an estimated 21.9% of the world population has access to the Internet with the highest access rates (measured as a percentage of the population) in North America (73.6%), Oceania/Australia (59.5%) and Europe (48.1%). In terms of broadband access, Iceland (26.7%), South Korea (25.4%) and the Netherlands (25.3%) led the world.


title: Telecommunications

text: The Internet works in part because of protocols that govern how the computers and routers communicate with each other. The nature of computer network communication lends itself to a layered approach where individual protocols in the protocol stack run more-or-less independently of other protocols. This allows lower-level protocols to be customized for the network situation while not changing the way higher-level protocols operate. A practical example of why this is important is because it allows an Internet browser to run the same code regardless of whether the computer it is running on is connected to the Internet through an Ethernet or Wi-Fi connection. Protocols are often talked about in terms of their place in the OSI reference model (pictured on the right), which emerged in 1983 as the first step in an unsuccessful attempt to build a universally adopted networking protocol suite.


title: Telecommunications

text: For the Internet, the physical medium and data link protocol can vary several times as packets traverse the globe. This is because the Internet places no constraints on what physical medium or data link protocol is used. This leads to the adoption of media and protocols that best suit the local network situation. In practice, most intercontinental communication will use the Asynchronous Transfer Mode (ATM) protocol (or a modern equivalent) on top of optic fiber. This is because for most intercontinental communication the Internet shares the same infrastructure as the public switched telephone network.


title: Telecommunications

text: At the network layer, things become standardized with the Internet Protocol (IP) being adopted for logical addressing. For the World Wide Web, these "IP addresses" are derived from the human-readable form using the Domain Name System (e.g. 72.14.207.99 is derived from www.google.com). At the moment, the most widely used version of the Internet Protocol is version four but a move to version six is imminent.


title: Telecommunications

text: At the transport layer, most communication adopts either the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). TCP is used when it is essential every message sent is received by the other computer whereas UDP is used when it is merely desirable. With TCP, packets are retransmitted if they are lost and placed in order before they are presented to higher layers. With UDP, packets are not ordered nor retransmitted if lost. Both TCP and UDP packets carry port numbers with them to specify what application or process the packet should be handled by. Because certain application-level protocols use certain ports, network administrators can manipulate traffic to suit particular requirements. Examples are to restrict Internet access by blocking the traffic destined for a particular port or to affect the performance of certain applications by assigning priority.


title: Telecommunications

text: Above the transport layer, there are certain protocols that are sometimes used and loosely fit in the session and presentation layers, most notably the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols. These protocols ensure that data transferred between two parties remains completely confidential. Finally, at the application layer, are many of the protocols Internet users would be familiar with such as HTTP (web browsing), POP3 (e-mail), FTP (file transfer), IRC (Internet chat), BitTorrent (file sharing) and XMPP (instant messaging).


title: Telecommunications

text: Voice over Internet Protocol (VoIP) allows data packets to be used for synchronous voice communications. The data packets are marked as voice type packets and can be prioritized by the network administrators so that the real-time, synchronous conversation is less subject to contention with other types of data traffic which can be delayed (i.e. file transfer or email) or buffered in advance (i.e. audio and video) without detriment. That prioritization is fine when the network has sufficient capacity for all the VoIP calls taking place at the same time and the network is enabled for prioritization i.e. a private corporate-style network, but the Internet is not generally managed in this way and so there can be a big difference in the quality of VoIP calls over a private network and over the public Internet.


title: Telecommunications

text: Despite the growth of the Internet, the characteristics of local area networks (LANs)—computer networks that do not extend beyond a few kilometres—remain distinct. This is because networks on this scale do not require all the features associated with larger networks and are often more cost-effective and efficient without them. When they are not connected with the Internet, they also have the advantages of privacy and security. However, purposefully lacking a direct connection to the Internet does not provide assured protection from hackers, military forces, or economic powers. These threats exist if there are any methods for connecting remotely to the LAN.


title: Telecommunications

text: Wide area networks (WANs) are private computer networks that may extend for thousands of kilometres. Once again, some of their advantages include privacy and security. Prime users of private LANs and WANs include armed forces and intelligence agencies that must keep their information secure and secret.


title: Telecommunications

text: In the mid-1980s, several sets of communication protocols emerged to fill the gaps between the data-link layer and the application layer of the OSI reference model. These included AppleTalk, IPX, and NetBIOS with the dominant protocol set during the early 1990s being IPX due to its popularity with MS-DOS users. TCP/IP existed at this point, but it was typically only used by large government and research facilities.


title: Telecommunications

text: As the Internet grew in popularity and its traffic was required to be routed into private networks, the TCP/IP protocols replaced existing local area network technologies. Additional technologies, such as DHCP, allowed TCP/IP-based computers to self-configure in the network. Such functions also existed in the AppleTalk/ IPX/ NetBIOS protocol sets.


title: Telecommunications

text: Whereas Asynchronous Transfer Mode (ATM) or Multiprotocol Label Switching (MPLS) are typical data-link protocols for larger networks such as WANs; Ethernet and Token Ring are typical data-link protocols for LANs. These protocols differ from the former protocols in that they are simpler, e.g., they omit features such as quality of service guarantees, and offer medium access control. Both of these differences allow for more economical systems.


title: Telecommunications

text: Despite the modest popularity of Token Ring in the 1980s and 1990s, virtually all LANs now use either wired or wireless Ethernet facilities. At the physical layer, most wired Ethernet implementations use copper twisted-pair cables (including the common 10BASE-T networks). However, some early implementations used heavier coaxial cables and some recent implementations (especially high-speed ones) use optical fibers. When optic fibers are used, the distinction must be made between multimode fibers and single-mode fibers. Multimode fibers can be thought of as thicker optical fibers that are cheaper to manufacture devices for, but that suffer from less usable bandwidth and worse attenuation—implying poorer long-distance performance.


title: Proton

text: A proton is a stable subatomic particle, symbol , H, or H with a positive electric charge of +1 "e" elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ratio). Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred to as "nucleons" (particles present in atomic nuclei).