Internet and Telecommunications




Internet and Telecommunications


                                          This sitecovers the internet, telecommunication systems, standards, data storage formats, networks, software, hardware, communication protocols, business models, network economics, applications, services, products and future technologies of each sector. It also includes links to related sites and services such as other internet resources.


Please note that this is an unofficial version of a website maintained by a member of Encyclopædia Britannica publishing group. While it may be revised and updated periodically, it is never considered an authoritative source for any particular subject matter. You will need to check with your own sources before considering an article here as reliable information. For more general coverage of computer technology and digital media, see Wikipedia's Digital Media page.


Internet:


                        The internet has grown from its beginnings in 1969 when British mathematician Alan Kay created what we now call "The World Wide Web". Originally designed as a system for storing text files, emails, and maps, today the web has become one of the dominant forces in our global economic, cultural, intellectual, scientific, political and social life. The internet is made up of millions or billions of individual pages containing the data we use every day. They are called World-Web-Pages (W-Web-pages) and they are linked together via hyperlinks on their homepages which contain further information about them. These links are known as backbones. Each W-Web-page contains all information found on it, including those found elsewhere in the web as well. All pages on the internet can access and share information from anywhere using a web browser of choice. Information can even be viewed almost instantaneously and accessed across a world wide area of interconnected computers. However, the most important characteristic of the internet is its dynamic nature that allows it to dynamically change depending upon events that occur on the Web. Because of this, it provides us with many possibilities to explore the information on the internet. There are several different ways to navigate it: surfing the internet (e.g., the Amazon homepage when you start browsing), downloading web pages (e.g., Google Chrome and Mozilla Firefox), watching videos, playing games, making purchases (e.g., eBay), searching for content online (e.g., YouTube and Netflix), subscribing to email lists, etc. The Internet remains a single medium, but it can be divided into three areas, namely, open sources, commercial web services, and gateways (e.g., e.g., Microsoft Exchange Server). At present the number and density of online websites (including e-mail providers) on the Web has increased dramatically over the last 20 years and continues to increase. In 2000 there were approximately 30 million people with Internet connected machines and 1.5 billion active users. By 2014 more than 500 million new Internet users were added each year, in part due to mobile devices allowing users to browse the Web from their phones and tablets.[1] The following figure shows the growth rate of subscribers for five major Internet search engines, followed by the expected percentage annual growth rates.


Telecommunications;


The telephone was invented in 1876 by Alexander Graham Bell.[2] Soon after it became widely available to the public in England, it soon spread around Europe and quickly became popular throughout Western civilization. The telephone was first used in the United States in 1905 as a way to communicate between cities and towns, but did not make much impact on America until later that century. Since then, communications between one city and another have been greatly improved thanks to inventions like telegraphy (1843), wires (1880), radio signals (1891), and television (1939). Telephone lines are often referred to as wireline telephones because they used copper cabling. On land, the phone line is separated from a fixed exchange in a building or factory. When moving on water, the phone line is connected to a submarine cable or a high-voltage aerial connection, typically at very low frequencies, so that messages get sent over long distances. Although fiber optics and fiber wire technology allow for better signal quality, they still lack some features of traditional telecommunications, including voice and video calling. Today, cell phones have replaced the conventional telephone as the primary mode of receiving telephone calls; however, in some cases this method only works between two people, such as through VoIP (voice over internet protocol).[3] Mobile services allow people to browse the entire web on their smartphones and tablet devices. With advanced wireless technology, portable devices like smartwatches and wearable accessories like earbuds can provide these functions without sacrificing connectivity either at a distance or within the same device. Wireless carriers and service providers can offer Wi-Fi networks that connect multiple handheld devices simultaneously. Moreover, Wi-Fi and Bluetooth systems allow users to enjoy music or movies while they are away.[4]


History [ edit ] ;


                                  The earliest example of a telephone is believed to have been composed of primitive electrical circuits developed by Thomas Edison in 1878.[5]


According to Joseph Weizenbaker's theory of electronic circuitry, the circuit is composed of transistors, resistors, capacitors, switches, diodes, and coils. He defined analog or digital electronics, based on his work on metal oxides. His design included the formation of light bulbs (photovoltaic cells) and capacitors, the basic elements of electrical circuits. Electricity was discovered by the Irish physicist James Joule in 1879 and he wrote: "A current is induced by a falling drop, not by a jump of electrons." But not everyone was convinced by him. Albert Szent-Györgyi who published his book Modern Electronic Circuits, written under the pseudonym Szymbryozhets and authored an encyclopedia of electrical engineering, questioned the concept of a 'current' flowing in straight lines in which case it could have originated from outside the circuit but this was proven false by Robert C. May in 1895.[6]


Hoffmann developed a mechanical telegraphy system based on electrochemical reactions (which had just begun to emerge at that time). A metal membrane was used to transmit electrical impulses and transmit the signals through wires. After a few experiments, it was noticed that the currents flowing through the wires were in actuality voltages that existed in the voltage field but did not necessarily flow in that direction. Electrostatic coupling, a process in which the polarity, amplitude, and phase of both pulses are determined by the electric charges carried by each pulse, was the mechanism responsible for this discovery. The phenomenon was named electromagnetism. Before this point, alternating polarity current was used to transfer energy only between adjacent circuits, which caused delays in switching on and off of electric lamps on watch faces, electric lights, clocks, and timers. As a result, electricity would be transmitted in waves instead of currents, therefore leading to higher costs of transmission. A solution to this was presented by Siemens AG, which developed the prototype of an electromagnetic transmission system that used alternating AC power.


At the end of the 19th century, the French engineer Pierre Faraday built a simple instrument known as a galvanometer that measured the intensity of magnetic fields. This proved useful for creating large rotating electric motors, such as generators used in railway rolling Stock stations. However, in 1881, the English Mathew Boulton demonstrated how electricity could be converted from direct current to magnetizing coil. This discovery changed the course of science forever! Electrical currents could flow in both directions: from cathode towards anode; from the opposite direction can act as negative and positive charges, respectively, generating a potential difference. This potential difference is necessary for the generation of a static magnetic field (a rotating electric motor) because magnets do not charge themselves out of thin air or move by inertia but rather require a constant, strong external force.[7]


In 1919, Paul Nipkow’s paper: “On the Effect of Transient Current on Resistance" proposed a series of experiments that confirmed results received by the German physico-electrical and electrical scientist Wilhelm Röhler. The experiment led to the construction of a short range transmitting machine that used synchronous rectifiers (resistance transformers) to separate the input pulse, the resulting differential voltage, and its output. Röhler’s experiment showed that the amount of time needed for a signal to travel the length of a conductor (usually 50 centimeters) increases with the velocity of current passing through. Röhler’s experimental results were not reported until 1928. The findings laid the foundation for an extensive investigation into the effect of transient and permanent currents on human resistance. An extension of Röhler's research was done in 1929 by Otto von Guericke, who showed that when varying the frequency of the current source, the resistance of human skin decreased almost linearly as a function of current level. From 1930 onward, scientists were encouraged to continue investigating the effects of inductive and capacitive currents, such as the Tesla coil, the induction motor, and the induction transformer.


Early history [ edit ] ;


                                           In 1885, Frenchman Jules Mercadier patented an invention that used the principle of variable potentials (V) to convert alternating current into a stream of sound waves. V is the sum of an amplitude and a phase. If the amplitude of the current flowing in a circuit is varied at each stage, the resultant waveform should possess random changes of amplitude and phase. To demonstrate this,[8] Mercadier used an arrangement of parallel conductors of various lengths with varying weights attached to them. He placed a battery in the middle and marked each wire with a letter ("a," "b," "c," etc.) and applied a varying voltage to each wire at different positions across the circuit. When he switched on the battery, the voltage at the ends went down, whereas the voltage at the center remained the same. Similarly, when he turned the battery off, the letters on the right side of the battery were reversed, but the left side of the battery was unchanged.


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