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Long Line (telecommunications)
In telecommunication, a long line is a transmission line in a long-distance communications network such as carrier systems, microwave radio relay links, geosynchronous satellite links, underground cables, aerial cables and open wire, and Submarine communications cables. In the United States, some of this technology was spun off into the corporate entity known as ''AT&T Long Distance'' with the breakup of AT&T in 1984. Previously, the AT&T Long Lines division of the Bell System provided maintenance and installation of long line facilities for the Bell System's long-distance service. See also * Long-haul communications * Long-distance calling In telecommunications, a long-distance call (U.S.) or trunk call (also known as a toll call in the U.K. ) is a telephone call made to a location outside a defined local calling area. Long-distance calls are typically charged a higher billing rate ... {{DEFAULTSORT:Long Line (Telecommunications) Telephony Communication circuits ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telecommunication
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. 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. Other examples of pre-modern long-distance communication included audio messages, such as coded drumb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications Network
A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, message switching, or packet switching, to pass messages and signals. Multiple nodes may cooperate to pass the message from an originating node to the destination node, via multiple network hops. For this routing function, each node in the network is assigned a network address for identification and locating it on the network. The collection of addresses in the network is called the address space of the network. Examples of telecommunications networks include computer networks, the Internet, the public switched telephone network (PSTN), the global Telex network, the aeronautical ACARS network, and the wireless radio networks of cell phone telecommunication providers. Network structure In general, every telecommunications network conceptually c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carrier System
A carrier system is a telecommunications system that transmits information, such as the voice signals of a telephone call and the video signals of television, by modulation of one or multiple carrier signals above the principal voice frequency or data rate.Western Electric (1969) ''Fundamentals of Telephone Communication Systems'', p.16.2 Carrier systems typically transmit multiple channels of communication simultaneously over the shared medium using various forms of multiplexing. Prominent multiplexing methods of the carrier signal are time-division multiplexing (TDM) and frequency-division multiplexing (FDM). A cable television system is an example of frequency-division multiplexing. Many television programs are carried simultaneously on the same coaxial cable by sending each at a different frequency. Multiple layers of multiplexing may ultimately be performed upon a given input signal. For example, in the public switched telephone network, many telephone calls are sent over sha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microwave Radio Relay
Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300MHz to 300GHz(1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signals are normally limited to the line of sight, so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter, but such systems are expensive and generally used only in specialist roles. Although an experimental microwave telecommunication link across the English Channel was demonstrated in 1931, the development of radar in World War II provided the technology for practical exploitation of microwave communication. During the war, the British Army introduced the Wireless Set No. 10, which used microwave relays to multiplex eight telephone channels over long distances. A link across the English Channel allow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope thermoelectric generators (RTGs). Most satellites also have a method of communication to ground stations, called Transponder (satellite communications), transponders. Many satellites use a Satellite bus, standardized bus to save cost and work, the most popular of which is small CubeSats. Similar satellites can work together as a group, forming Satellite constellation, constellations. Because of the high launch cost to space, satellites are designed to be as lightweight and robust as possible. Most communication satellites are radio Broadcast relay station, relay stations in orbit and carry dozens of transponders, each with a bandwidth of tens of megahertz. Satellites are placed from the surface to orbit by launch vehicles, high enough to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerial Cable
An aerial cable or air cable is an insulated cable usually containing all conductors required for an electrical distribution system (typically using aerial bundled cables) or a telecommunication line, which is suspended between utility poles or electricity pylons. As aerial cables are completely insulated there is no danger of electric shock when touching them and there is no requirement for mounting them with insulators on pylons and poles. A further advantage is they require less right of way than overhead lines for the same reason. They can be designed as shielded cables for telecommunication purposes. If the cable falls, it may still operate if its insulation is not damaged. As aerial cables are installed on pylons or poles, they may be cheaper to install than underground cables, as no work for digging is required, which can be very expensive in rocky areas. Use Aerial cables are mostly used for telecommunication systems or for power transmissions with voltages bel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Wire
Open wire was an early transmission technology in telecommunication, first used in telegraphy. It consisted of pairs of electric wire strung on a pole line between communities, towns, and cities. The wire of the transmission line was attached to the cross-arms of each pole with glass insulators.E.F. O'Neill (ed.), Bell Telephone Laboratories Staff,, ''A History of Engineering and Science in the Bell System–Transmission Technology (1925–1975)'' AT&T Bell Laboratories (1985), ISBN 0-932764-08-8, p.4 It was originally manufactured from iron or steel, but developments in annealing of copper made it possible to use this metal by the 1890s to reduce electrical resistance substantially. Copper wire was drawn to a diameter of up to 1/6 inch (165 mils). The glass insulators on the pole cross-arms were spaced at about 12 inches apart. Typically up to five wire pairs were installed on each crossarm, and multiple cross-arms could be installed on each pole. The practical limit in dista ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submarine Communications Cable
A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean and sea. The first submarine communications cables laid beginning in the 1850s carried telegraphy traffic, establishing the first instant telecommunications links between continents, such as the first transatlantic telegraph cable which became operational on 16 August 1858. Subsequent generations of cables carried telephone traffic, then data communications traffic. Modern cables use optical fibre technology to carry digital data, which includes telephone, Internet and private data traffic. Modern cables are typically about in diameter and weigh around for the deep-sea sections which comprise the majority of the run, although larger and heavier cables are used for shallow-water sections near shore. Submarine cables first connected all the world's continents (except Antarctica) when Java was connected to Darwin, Northern Terr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications In The United States
The primary regulator of communications in the United States is the Federal Communications Commission. It closely regulates all of the industries mentioned below with the exception of newspapers and the Internet service provider industry. History The Federal Communications Commission (FCC) is an independent government agency responsible for regulating the radio, television and phone industries. The FCC regulates all interstate communications, such as wire, satellite and cable, and international communications originating or terminating in the United States. Press Newspapers declined in their influence and penetration into American households in the late 20th century. Most newspapers are local, having little circulation outside their particular metropolitan area. The closest thing to a national paper the U.S. has is ''USA Today''. Other influential dailies include ''The New York Times'', ''The Washington Post'' and ''The Wall Street Journal'' which are sold in most U.S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell System Divestiture
The breakup of the Bell System was mandated on January 8, 1982, by an agreed consent decree providing that AT&T Corporation would, as had been initially proposed by AT&T, relinquish control of the Bell Operating Companies, which had provided local telephone service in the United States. This effectively took the monopoly that was the Bell System and split it into entirely separate companies that would continue to provide telephone service. AT&T would continue to be a provider of long-distance service, while the now-independent Regional Bell Operating Companies (RBOCs), nicknamed the "Baby Bells", would provide local service, and would no longer be directly supplied with equipment from AT&T subsidiary Western Electric. This divestiture was initiated by the filing in 1974 by the United States Department of Justice of an antitrust lawsuit against AT&T. AT&T was, at the time, the sole provider of telephone service throughout most of the United States. Furthermore, most telephonic eq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AT&T Long Lines
AT&T Communications, Inc., was a division of the AT&T Corporation that, through 23 subsidiaries, provided interexchange carrier and long-distance calling, long-distance telephone services. History AT&T Long Lines The American Telephone & Telegraph Long Lines wire, cable, and microwave radio relay network provided long-distance services to AT&T and its customers. The connection to other countries from the United States began here. By the 1970s, 95% of distance and 70% of intercity telephone calls in the United States were carried by AT&T. Before utilizing microwave relay and coaxial cables, AT&T used lines for long-distance calling, long-distance service. In 1911, the system connected New York to Denver. The introduction of repeater towers allowed such connections to reach across North America. In the 1930s the company experimented with long-distance coaxial cable. The first long-distance L-carrier coaxial link in 1936 connected Philadelphia and New York City. With impr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell System
The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America for over one hundred years from its creation in 1877 until its antitrust breakup in 1983. The system of companies was often colloquially called Ma Bell (as in "Mother Bell"), as it held a vertical monopoly over telecommunication products and services in most areas of the United States and Canada. At the time of the breakup of the Bell System in the early 1980s, it had assets of $150 billion (equivalent to $ billion in ) and employed over one million people. Ever since the 1910s, American antitrust regulators had been observing and accusing the Bell System of abusing its monopoly power, and had brought legal action multiple times over the decades, until in 1974 the Antitrust Division of the U.S. Department of Justice brought a lawsuit against Be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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