第30课听力
| UNIT 30 Something about Telephone When imaginative scientists first suggested the possibility that one person could speak directly to another over a long distance,few people took them seriously. Among the few who did was a Scotsborn American named Alexander Graham Bell, who was one of the first to develop a telephone in 1876. Now the most common means of voice communication in the world, the telephone of today, is infinitely more sophisticated and effective than the crude instrument developed by Bell, and it is being used in ways he could not possibly have foreseen. One area that is rapidly expanded is communications service "on the move".Because America is such a highly mobile society a society on wheelstelephones in cars and trucks are becoming as essential as those in homes and offices. Industry officials have predicted that mobile communications service will soon be more competitive in many respects than the service provided by telephones that do not move. Another area rapidly developing is overseas telephone service. In 1927, when overseas telephone service was inaugurated with a radio telephone call between New York and London, the occasion was heralded as "thrilling". Today, many telephone users regard international calls as routine and overseas service, thanks largely to undersea cables and communications satellites, has undergone extraordinary improvement. Transmission has been made clearer, charges have been greatly reduced and dependability has been improved. Overseas telephone service has now been extended to nearly 350 countries and areas throughout the world. The introduction of direct distance dialing in 1951 was one of the most significant developments in the effort to improve longdistance service. Direct distance dialing is not only fast and convenient for the caller, it has also enabled telephone companies to handle the extraordinary growth of telephone use that has occurred since the 1950s. Between 1950 and 1973 the number of telephones in the United States tripled, with the addition of 90 million telephones. For the Bell Telephone System alone, longdistance calls in the same period have increased from 1.4 billion to 8.5 billion, and indications have shown that longdistance calls will continue to increase significantly in the years ahead. In 1972, 77 percent of the 8.5 billion longdistance calls were dialed by the customer. Another very significant development in telephone use is in the area of data communications. Here is an example of how medical data are being transmitted. In a small town in the western part of the United States about 300 people gathered in the local school to undergo tests for lung diseases. The procedures followed marked a major advance in detecting diseases by providing almost instantaneous computer diagnosis over longdistance telephone lines. First, technicians at the school used touchtone telephones to send vital statistics on the person being tested to the computer, which was located in a hospital 60 miles away. The individual then exhaled into a spirometer, which measures volume and rate of air exhalation, and these measurements were automatically transmitted to the computer. The computer instantly calculated the results and within two seconds relayed them back to the testing center. Normally, it takes hours or even weeks to evaluate spirometer measurements. By utilizing a computer and data communications, however, the time lag is reduced to seconds. Moreover, people in a remote community are put within arm's length of the most upto date medical facilities available. For many people the most exciting development in recent years is picturephone service. Picturephone service, which will become available commercially at the beginning of this century, is being used by large business corporation; but it will no doubt spread from the office to the home. It is already clear that the next best thing in telephone service is going to be picturephone call. Possibly the most significant research now being conducted is in the use of the laser beam in telephone communications. This wonderful light,first produced by scientists in 1960, can beam continuously and with extraordinary intensity. Instead of using light to see by,telephone researchers are thinking of way to use light to communicate by. In other words,they are thinking of using light as radio waves to transmit telephone calls, television programs and data messages from one point to another, with the expansion of picturephone service and high speed data communications between computers, present messagecarrying capacities may soon become inadequate. If it turns out to be technically and economically sound, the laser might prove to be a major breakthrough in telephone communications. Current research in telephone communications is so extensive and changes are coming about so rapidly that no one can predict with accuracy what the telephone of tomorrow will look like. But there is at least one prediction that can be made with assurance: there will be more and more telephones in the future, and they will be much better than present ones. |
京公网安备 11011202003401号
