题目内容
The Flying Phone Box
A surprise for air travelers
The strides made in satellite-communications technology in recent years are at last yielding benefits for air travelers, particularly executives who need to keep in touch with their offices. Five airlines— three of them based in the Asia-Pacific region—have recently equipped aircraft to offer outbound (向外的)telephone calls to anywhere in the world using a new satellite system. And in the not-too-distant future, businessmen will be able to send faxes in flight, too.
Air Canada, Qantas of Australia, United Airlines of the US and Japan Air Lines have at least one satellite-communication aircraft apiece. Hong Kong's Cathay Pacific Airways is also about to offer the service and several other airlines are expected to follow. The calls, dialed directly and charged to a credit card, will cost about US $ 9 ～ 10 per minute.
The earlier flying phones
Phone communications from aircraft are not entirely new. For some time, telephones have been available to passengers on US internal flights, for example, and on private jets.
But these systems have used cellular phones operating on very high frequency radio links. These systems—the same links that keep pilots in touch with flight controllers—have either limited range or low quality and reliability, particularly over vast oceans such as the Pacific. By contrast, the new satellite service will provide clear links instantly to destinations around the world.
Technological obstacles
Several technological problems had to be resolved before the service could be introduced. One was to define an effective technical standard, Airinc 741, that guarantees compatibility among different manufacturers' avionics systems—essential if the service was to be truly global.
Another was to make reliable antennas(天线) small enough and light enough to mount on aircraft of different types. And a third was to perfect voice-coding algorithms(规则系统), which tell machinery how to break down voice signals into digital signals for transmission at the standard rate of 9,600 bits a second.
A further drawback, for any type of call routed by satellite, is an uncomfortable time lag between words being spoken and received. Because of the distance that signals have to travel, there is a delay of about a quarter of a second. With airborne calls, there is the potential for a double delay as signals arriving via satellite at a ground station are passed on via another satellite to their destination.
To avoid this problem, ground stations have been equipped to identify calls from aircraft and route them to coaxial or fibre-optic cables for the second lag of their journey. Surface links, though long, are still considerably shorter than the 72,000-km round-trip into space. Most calls will therefore not suffer the double delay.
The International Maritime Satellite Organization (Inmarsat) approved the initial sitcom system for commercial service last November 'after two years of trials. Besides the handful of aircraft operated by the five major carriers who have signed on to the system, about two dozen company jets have fitted with the necessary equipment.
A new technology
The technology has three components: antennas and associated equipment on board planes, communications satellites, and ground stations.
In the course of development, antennas have lust both their dish shape and several kilograms. Even so, antenna and avionics weigh as much as two occupied scats. One obstacle to further weight savings, however, is that lighter antennas are more easily confused by the plethora(过多) of satellites now circling the Earth.
The satellites themselves are provided by Inmarsat, a London-based cooperative of 64 nations. One operational satellite and several 'back-ups
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Section B
Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C and D.
听力原文： Spacemen have to be specially trained for traveling in space. They should be in very good mental and physical health. Most of them are experienced pilots of very fast aeroplanes.
All spacemen have to do various space exercises before traveling to space. They have to be strong enough to bear the great pressures they will feel at launching and landing. When traveling in space or orbiting round a planet, spacemen have to become used to the weightless conditions and learn how to walk, eat, drink and sleep in a condition of weightlessness. They train for their space travels in model spacecraft, which are like the actual spacecraft. Spacemen also have to know all about the various parts of their spacecraft. They should be able to repair any part that is damaged while traveling.
When man goes into space he must take air, food and water. He must also get rid of bad air and waste matter. Food is prepared in a paste form. and kept in tubes. Waste is stored in containers and got rid of when the spacecraft reaches the Earth. These problems have been solved for short space trips, but not for long trips.
(35)
听力原文： Do you know that there's a kind of bird that can sew？ This bird, called the tailorbird, uses its mouth as a needle. It sews leaves together in a shape of a cup. Then it adds a layer of straw to the inside of the cup and lays its eggs there. Each bird species builds its own special kind of nest. The most common materials used for nests are grasses, branches and feathers. A bird must weave these materials into a nest. Just imagine building a house without cement or nails to hold it together. Another bird is called the weaverbird. The weaverbird builds a nest that looks like a basket. The nest is shaped like a pear with a hole in the middle. The hole is the door of the nest. The third bird is called the ovenbird. The ovenbird makes a nest that is very solid. The nest is made of mud. The ovenbird forms the mud into the shape of an oven and then lets it dry in the sun. The sun bakes the mud, making it very hard. Not all birds make their homes in branches. Some birds build their nests on the ground, while others bury their eggs under the ground. And some birds do not build nests at all. So when you look for nests and eggs in the branches of trees and bushes, remember, that some nests may be right under your feet.
(38)
A．Biology.B．Geology.C．History.D．Political Science.
听力原文：W: Suppose the company offered you a pay raise of 50 per cent, would you be so determined to leave and look for a job elsewhere？
M: Yes. I've set my mind on it. I'd like to find a job with full scope to show my ability.
Q: Why has the man decided to leave the company？
(19)
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