Paper 2000 Question: 1 (a) Al-Beruni
Download 0.98 Mb.
|
| For residential service, voice mail can either be purchased from the telephone company or can be obtained by purchasing an answering machine. An answering machine usually contains a regular telephone set along with the ability to detect incoming calls and to record and play back messages, with either an audiotape or a digital system. After a preset number of rings, the answering machine plays a prerecorded message inviting the caller to leave a message to be recorded.
Toll-free 800 numbers are a very popular service. Calls made to a telephone number that has an 800 area code are billed to the called party rather than to the caller. This is very useful to any business that uses mail-order sales, because it encourages potential customers to call to place orders. A less expensive form of 800-number service is now available for residential subscribers. In calling telephone numbers with area codes of 900, the caller is billed an extra charge, often on a per-minute basis. The use of these numbers has ranged from collecting contributions for charitable organizations, to businesses that provide information for which the caller must pay. While the United States and Canada are the most advanced countries in the world in telephone-service technologies, most other industrialized nations are not far behind. An organization based in Geneva, Switzerland, called the International Telecommunication Union (ITU), works to standardize telephone service throughout the world. Without its coordinating activities, International Direct Distance Dialing (a service that provides the ability to place international calls without the assistance of an operator) would have been extremely difficult to implement. Among its other services, the ITU creates an environment in which a special service introduced in one country can be quickly duplicated elsewhere. V THE HISTORY OF THE TELEPHONE The history of the invention of the telephone is a stormy one. A number of inventors contributed to carrying a voice signal over wires. In 1854 the French inventor Charles Bourseul suggested that vibrations caused by speaking into a flexible disc or diaphragm might be used to connect and disconnect an electric circuit, thereby producing similar vibrations in a diaphragm at another location, where the original sound would be reproduced. A few years later, the German physicist Johann Philip Reis invented an instrument that transmitted musical tones, but it could not reproduce speech. An acoustic communication device that could transmit speech was developed around 1860 by an Italian American inventor, Antonio Meucci. The first to achieve commercial success and inaugurate widespread use of the telephone, however, was a Scottish-born American inventor, Alexander Graham Bell, a speech teacher in Boston, Massachusetts. Bell had built an experimental telegraph, which began to function strangely one day because a part had come loose. The accident gave Bell insight into how voices could be reproduced at a distance, and he constructed a transmitter and a receiver, for which he received a patent on March 7, 1876. On March 10, 1876, as he and his assistant, Thomas A. Watson, were preparing to test the mechanism, Bell spilled some acid on himself. In another room, Watson, next to the receiver, heard clearly the first telephone message: “Mr. Watson, come here; I want you.” A few hours after Bell had patented his invention, another American inventor, Elisha Gray, filed a document called a caveat with the U.S. Patent Office, announcing that he was well on his way to inventing a telephone. Other inventors, including Meucci and Amos E. Dolbear, also made claim to having invented the telephone. Lawsuits were filed by various individuals, and Bell’s claim to being the inventor of the first telephone had to be defended in court some 600 times. Gray’s case was decided in Bell’s favor. Meucci’s case was never resolved because Meucci died before it reached the Supreme Court of the United States. A Advances in Technology After the invention of the telephone instrument itself, the second greatest technological advance in the industry may have been the invention of automatic switching. The first automatic exchanges were called Strowger switches, after Almon Brown Strowger, an undertaker in Kansas City, Missouri, who invented the system because he thought his town’s human operators were steering prospective business to his competitors. Strowger received a patent for the switches in 1891. Long-distance telephony was established in small steps. The first step was the introduction of the long-distance telephone, originally a special highly efficient instrument permanently installed in a telephone company building and used for calling between cities. The invention at the end of the 19th century of the loading coil (a coil of copper wire wound on an iron core and connected to the cable every mile or so) increased the speaking range to approximately 1,000 miles. Until the 1910s the long-distance service used repeaters, electromechanical devices spaced along the route of the call that amplified and repeated conversations into another long-distance instrument. The obvious shortcomings of this arrangement were overcome with the invention of the triode vacuum tube, which amplified electrical signals. In 1915 vacuum-tube repeaters were used to initiate service from New York City to San Francisco, California. The vacuum tube also made possible the development of longwave radio circuits that could span oceans. Sound quality on early radio circuits was poor, and transmission subject to unpredictable interruption. In the 1950s the technology of the coaxial-cable system was combined with high-reliability vacuum-tube circuits in an undersea cable linking North America and Europe, greatly improving transmission quality. Unlike the first transatlantic telegraph cable placed in service in 1857, which failed after two months, the first telephone cable (laid in 1956) served many years before becoming obsolete. The application of digital techniques to transmission, along with undersea cable and satellites, finally made it possible to link points halfway around the earth with a circuit that had speech quality almost as good as that between next-door neighbors. Improved automatic-switching systems followed the gradual improvement in transmission technology. Until Direct Distance Dialing became available, all long-distance calls still required the assistance of an operator to complete. By adding a three-digit area code in front of the subscriber’s old number and developing more sophisticated common-control-switching machines, it became possible for subscribers to complete their own long-distance calls. Today customer-controlled international dialing is available between many countries. B Evolution of the Telephone Industry In the late 1800s, the Bell Telephone Company (established in 1877 by Alexander Graham Bell and financial backers Gardiner Greene Hubbard, a lawyer, and Thomas Sanders, a leather merchant) strongly defended its patents in order to exclude others from the telephone business. After these patents expired in 1893 and 1894, independent telephone companies were started in many cities and most small towns. A period of consolidation followed in the early 1900s, and eventually about 80 percent of the customers in the United States and many of those in Canada were served by the American Telephone and Telegraph Company (AT&T), which had bought the Bell Telephone Company in 1900. AT&T sold off its Canadian interests in 1908. From 1885 to 1887 and from 1907 to 1919 AT&T was headed by Theodore Vail, whose vision shaped the industry for most of the 20th century. At that time, AT&T included 22 regional operating companies, each providing telephone service to an area comprising a large city, state, or group of states. In addition to owning virtually all of the long-distance circuits in use in the United States, AT&T owned the Western Electric Company, which manufactured most of the equipment. Such a corporate combination is called a vertically integrated monopoly because it dominates all facets of a business. Both the long-distance part of AT&T and the operating companies were considered to be “natural monopolies,” and by law were decreed to be the sole provider of telephone service within a designated area. More than 5,000 independent companies remained, but each independent was also a monopoly with an exclusive service region. This arrangement reduced the costs associated with more than one company stringing wires in an area, and eliminated the early problems that had arisen when customers of one company serving a region wished to call customers of another company serving the same area. In exchange for the absence of competition, the companies were regulated by various levels of government, which told them what services they must provide and what prices they could charge. During this time, telephone sets were never sold to the customer—they were leased as part of an overall service package that included the telephone, the connecting lines to the exchange, and the capability of calling other customers. In this way, the telephone company was responsible for any problems, whether they arose from equipment failures, damage to exposed wires, or even the conduct of operators on their job. If a telephone set broke, it was fixed or replaced at no charge. Since stringing wires between exchanges and users was a major part of the cost of providing telephone service, especially in rural environments, early residential subscribers often shared the same line. These were called party lines—as opposed to private, or single-party, lines. When one subscriber on a party line was making a telephone call, the other parties on the line could not use the line. Unfortunately, they could listen to the conversation, thereby compromising its privacy. Such arrangements also meant that, unless special equipment was used, all the telephones on the line would ring whenever there was a call for any of the parties. Each party had a distinct combination of short and long rings to indicate whether the call was for that house or another party. Business telephones were usually private lines. A business could not afford to have its service blocked by another user. This meant that business service was more expensive than residential service. Businesses continued to be charged more for their private lines than were subscribers with private lines in homes. This subsidization of telephones in homes permeated the government-regulated rate structure of the telephone industry until about 1980. Long-distance service was priced artificially high, and the consequent extra revenues to the telephone company were used to keep the price of residential service artificially low. While most consumers were happy with the control of all equipment by the telephone companies, some were not. Also, because of strong vertical integration within AT&T, the purchase of equipment from independent manufacturers was tightly controlled. AT&T initially refused to allow the independently manufactured Carterphone, a device that linked two-way-radio equipment to a telephone, to be connected to its network. After protracted lawsuits, AT&T agreed in 1968 to allow the connection of independently manufactured telephones to its network, provided they met legal standards set by the Federal Communications Commission (FCC). While the AT&T agreement did not directly involve the other telephone companies in the country, over time the entire industry followed AT&T’s lead. In 1974 MCI Communications Corporation challenged AT&T about its right to maintain a monopoly over long-distance service. Antitrust proceedings were brought, and eventually settled in 1982 in a consent decree that brought about the breakup of AT&T. In a consent decree, the federal government agrees to stop proceedings against a company in return for restrictions on or changes in the company. The antitrust proceedings were dropped when AT&T agreed to sell off its local operating companies, retaining the long-distance network and manufacturing companies. The former AT&T operating companies were regrouped into seven Regional Holding Companies (RHCs), which were initially restricted from engaging in any business other than telephone service within their assigned service area. The RHCs promptly began sidestepping these restrictions by setting up subsidiaries to operate in the unregulated environment and seeking legislation to further remove restrictions. At the same time, alternate long-distance carriers, such as MCI and Sprint, sought legislation to keep AT&T under as much regulation as possible while freeing themselves from any regulation. C The Telephone Industry Today In 1996 the U.S. government enacted the Telecommunications Reform Act, which removed government rules preventing local and long-distance phone companies, cable television operators, broadcasters, and wireless services from directly competing with one another. The act spurred consolidation in the industry, as regional companies joined forces to create telecommunications giants that provided telephone, wireless, cable, and Internet services. In other countries, until the 1990s, most of the telephone companies were owned by each nation’s central government and operated as part of the post office, an arrangement that inevitably led to tight control. Many countries are now privatizing telephone service. In order to escape government regulation at home, U.S. companies are investing heavily in the phone systems of other countries. For example, in 1995 AT&T announced it would attempt to gain a share of the market for telephone services in India. In a reverse trend, European companies are investing in U.S. long-distance carriers. Other major markets for telephone companies are opening up around the globe as the developing world becomes more technologically advanced. Nonindustrial countries are now trying to leapfrog their development by encouraging private companies to install only the latest technology. In remote places in India and Africa, the use of solar cells is now making it possible to introduce telephones in areas still without electricity. VI RECENT DEVELOPMENTS The introduction of radio into the telephone set has been the most important recent development in telephone technology, permitting first the cordless phone and now the cellular phone. In addition to regular telephone service, modern cellular phones also provide wireless Internet connections, enabling users to send and receive electronic mail and search the World Wide Web. Answering machines and phones with dials that remember several stored numbers (repertory dials) have been available for decades, but because of their expense and unreliability were never as popular as they are today. Multifunctional telephones that use microprocessors and integrated circuits have overcome both these barriers to make repertory dials a standard feature in most phones sold today. Many multifunctional telephones also include automatic answering and message-recording capability. Videophones are devices that use a miniature video camera to send images as well as voice communication. Videophones can be connected to regular telephone lines or their messages can be sent via wireless technology. Since the transmission of a picture requires much more bandwidth (a measure of the amount of data a system can transmit per period of time) than the transmission of voice, the high cost of transmission facilities has limited the use of videophone service. This problem is being overcome by technologies that compress the video information, and by the steadily declining cost of transmission and video-terminal equipment. Video service is now used to hold business “teleconferences” between groups in distant cities using high-capacity transmission paths with wide bandwidth. Videophones suitable for conversations between individuals over the normal network are commercially available, but because they provide a picture inferior to that of a television set, have not proven very popular. Television news organizations adopted the use of videophones to cover breaking news stories in remote areas. Their use escalated in 2001 during the U.S. war against terrorists and the Taliban regime in Afghanistan. Telecommunications companies are rapidly expanding their use of digital technology, such as Digital Subscriber Line (DSL) or Integrated Services Digital Network (ISDN), to allow users to get more information faster over the telephone. Telecommunications companies are also investing heavily in fiber optic cable to meet the ever-increasing demand for increased bandwidth. As bandwidth continues to improve, an instrument that functions as a telephone, computer, and television becomes more commercially viable. Such a device is now available, but its cost will likely limit its widespread use in the early part of the 21st century. Contributed By: Richard M. Rickert Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved. Question:6 Latitude and Longitude Latitude and Longitude Latitude and Longitude, system of geometrical coordinates used in designating the location of places on the surface of the earth. (For the use of these terms in astronomy, see Coordinate System; Ecliptic.) Latitude, which gives the location of a place north or south of the equator, is expressed by angular measurements ranging from 0° at the equator to 90° at the poles. Longitude, the location of a place east or west of a north-south line called the prime meridian, is measured in angles ranging from 0° at the prime meridian to 180° at the International Date Line. Midway between the poles, the equator, a great circle, divides the earth into northern and southern hemispheres. Parallel to the equator and north and south of it are a succession of imaginary circles that become smaller and smaller the closer they are to the poles. This series of east-west-running circles, known as the parallels of latitude, is crossed at right angles by a series of half-circles extending north and south from one pole to the other, called the meridians of longitude. Although the equator was an obvious choice as the prime parallel, being the largest, no one meridian was uniquely qualified as prime. Until a single prime meridian could be agreed upon, each nation was free to choose its own, with the result that many 19th-century maps of the world lacked a standardized grid. The problem was resolved in 1884, when an international prime meridian, passing through London's Greenwich Observatory, was officially designated. A metallic marker there indicates its exact location. Degrees of latitude are equally spaced, but the slight flattening at the poles causes the length of a degree of latitude to vary from 110.57 km (68.70 mi) at the equator to 111.70 km (69.41 mi) at the poles. At the equator, meridians of longitude 1 degree apart are separated by a distance of 111.32 km (69.17 mi); at the poles, meridians converge. Each degree of latitude and longitude is divided into 60 minutes, and each minute divided into 60 seconds, thereby allowing the assignment of a precise numerical location to any place on earth. Contributed By: Geoffrey J. Martin Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved. Question:7 (a)Cardiac Muscles and Skeletal Muscles Skeletal Muscle Skeletal muscle enables the voluntary movement of bones. Skeletal muscle consists of densely packed groups of elongated cells known as muscle fibers. This type of muscle is composed of long fibers surrounded by a membranous sheath, the sarcolemma. The fibers are elongated, sausage-shaped cells containing many nuclei and clearly display longitudinal and cross striations. Skeletal muscle is supplied with nerves from the central nervous system, and because it is partly under conscious control, it is also called voluntary muscle. Most skeletal muscle is attached to portions of the skeleton by connective-tissue attachments called tendons. Contractions of skeletal muscle serve to move the various bones and cartilages of the skeleton. Skeletal muscle forms most of the underlying flesh of vertebrates. Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved. Cardiac Muscle Cardiac muscle, found only in the heart, drives blood through the circulatory system. Cardiac muscle cells connect to each other by specialized junctions called intercalated disks. Without a constant supply of oxygen, cardiac muscle will die, and heart attacks occur from the damage caused by insufficient blood supply to cardiac muscle. This muscle tissue composes most of the vertebrate heart. The cells, which show both longitudinal and imperfect cross striations, differ from skeletal muscle primarily in having centrally placed nuclei and in the branching and interconnecting of fibers. Cardiac muscle is not under voluntary control. It is supplied with nerves from the autonomic nervous system, but autonomic impulses merely speed or slow its action and are not responsible for the continuous rhythmic contraction characteristic of living cardiac muscle. The mechanism of cardiac contraction is not yet understood. Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved. (b)Haze and Smog haze 1 haze [hayz] noun (plural haz•es) 1. particles in atmosphere: mist, cloud, or smoke suspended in the atmosphere and obscuring or obstructing the view 2. vague obscuring factor: something that is vague and serves to obscure something 3. disoriented mental or physical state: a mental or physical state or condition when feelings and perceptions are vague, disorienting, or obscured intransitive verb (past and past participle hazed, present participle haz•ing, 3rd person present singular haz•es) become filled with particles: to become saturated with suspended particles • As the temperatures rose, the sky began to haze over. [Early 18th century. Probably back-formation < hazy ] Microsoft® Encarta® 2006. © 1993-2005 Microsoft Corporation. All rights reserved. Smog Smog, mixture of solid and liquid fog and smoke particles formed when humidity is high and the air so calm that smoke and fumes accumulate near their source. Smog reduces natural visibility and often irritates the eyes and respiratory tract. In dense urban areas, the death rate usually goes up considerably during prolonged periods of smog, particularly when a process of heat inversion creates a smog-trapping ceiling over a city. Smog occurs most often in and near coastal cities and is an especially severe problem in Los Angeles and Tokyo. Smog prevention requires control of smoke from furnaces; reduction of fumes from metal-working and other industrial plants; and control of noxious emissions from automobiles, trucks, and incinerators. In the U.S. internal-combustion engines are regarded as the largest contributors to the smog problem, emitting large amounts of contaminants, including unburned hydrocarbons and oxides of nitrogen. The number of undesirable components in smog, however, is considerable, and the proportions highly variable. They include ozone, sulfur dioxide, hydrogen cyanide, and hydrocarbons and their products formed by partial oxidation. Fuel obtained from fractionation of coal and petroleum produces sulfur dioxide, which is oxidized by atmospheric oxygen, forming sulfur trioxide (SO3). Sulfur trioxide is in turn hydrated by the water vapor in the atmosphere to form sulfuric acid (H2SO4). The so-called photochemical smog, which irritates sensitive membranes and damages plants, is formed when nitrogen oxides in the atmosphere undergo reactions with the hydrocarbons energized by ultraviolet and other radiations from the sun. See Air Pollution. Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved. (c) Enzyme and Harmone Enzyme I INTRODUCTION Enzyme, any one of many specialized organic substances, composed of polymers of amino acids, that act as catalysts to regulate the speed of the many chemical reactions involved in the metabolism of living organisms, such as digestion. The name enzyme was suggested in 1867 by the German physiologist Wilhelm Kühne (1837-1900); it is derived from the Greek phrase en zymē, meaning “in leaven.” Those enzymes identified now number more than 700. Directory: 2014 2014 -> For want of a nail 2014 -> The Global Warming that Wasn’t 2014 -> Assembly, No. 3901 state of new jersey 216th legislature 2014 -> Stop Militarizing Law Enforcement Act of 2014 2014 -> Ihbb asian Championships 2014 middle school bowl Round 4 First Quarter 2014 -> Unit: Automotive and Auto Body 2014 -> Ihbb european Championships 2014 Bowl Round 4 First Quarter 2014 -> International History Bee and Bowl 2013-14 Asian Division Question Set Bowl Round Six 2014 -> United states patent and trademark office 2014 -> Walnut creek, ca branch executive committee meeting minutes Download 0.98 Mb. Share with your friends:
|