首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Part Ⅱ Reading Comprehension (Skimming and Scanning) Directions: In this part, you will have 15 minutes to go over the passage q
Part Ⅱ Reading Comprehension (Skimming and Scanning) Directions: In this part, you will have 15 minutes to go over the passage q
admin
2013-01-22
26
问题
Part Ⅱ Reading Comprehension (Skimming and Scanning)
Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1. For questions 1-7, choose the best answer from the four choices marked A), B), C) and D). For questions 8-10, complete the sentences with the information given in the passage.
Satellite Ⅳ
Today, you see compact satellite dishes perched on rooftops all over the United States. Drive through rural areas beyond the reach of the cable companies and you’ll find dishes on just about every house. The major satellite television companies are bringing in more customers every day with the lure of movies, sporting events and news from around the world.
The Broadcast TV Problem
Conceptually, satellite television is, a lot like broadcast television. It’s a wireless system for delivering television programming directly to a viewer’s house. Both broadcast television and satellite stations transmit programming via a radio signal. Broadcast stations use a powerful antenna to transmit radio waves to the surrounding area. Viewers can pick up the signal with a much smaller antenna.
The main limitation of broadcast television is range. The radio signals used to broadcast television shoot out from the broadcast antenna in a straight line. In order to receive these signals, you have to be in the direct "line of sight" of the antenna. One problem is that the Earth is curved, so it eventually breaks the signal’s line of site. The other problem with broadcast television is that the signal is often distorted even in the viewing area. To get a perfectly clear signal like you find on cable, you have to be pretty close to the broadcast antenna without too many obstacles in the way.
The Satellite TV Solution
Satellite television solves the problems of range and distortion by transmitting broadcast signals from satellites orbiting the Earth. Since satellites are high in the sky, there are a lot more customers in the line of site. Satellite television systems transmit and receive radio signals using specialized antennas called satellite dishes.
The television satellites are all in geosynchronous orbit, meaning that they stay in one place in the sky relative to the Earth. Each satellite is launched into space at about 7,000 mph (11,000kph), reaching approximately 22,200 miles (35,700km) above the Earth. At this speed and altitude, the satellite will revolve around the planet once every 24 hours—the same period of time it takes the Earth to make one full rotation. In other words, the satellite keeps pace with our moving planet exactly. This way, you only have to direct the dish at the satellite once, and from then on it picks up the signal without adjustment, at least when everything works right.
The Overall System
Early satellite TV viewers were explorers of sorts. They used their expensive dishes to discover unique programming that wasn’t necessarily intended for mass audiences. The dish and receiving equipment gave viewers the tools to pick up foreign stations, live feeding between different broadcast stations, NASA activities and a lot of other stuff transmitted using satellites.
Some satellite owners still seek out this sort of programming on their own, but today, most satellite TV customers get their programming through a direct broadcast satellite (DBS) provider, such as Direct TV or the Dish Network. The provider selects programs and broadcasts them to subscribers as a set package. Basically, the provider’s goal is to bring dozens or even hundreds of channels to your television in a form that approximates the competition, cable TV. Unlike earlier programming, the provider’s broadcast is completely digital, which means it has much better picture and sound quality. Early satellite television was broadcast in C-band radio—radio in the 3.4-gigabertz (GHz) to 7-GHz frequency range. Digital broadcast satellite transmits programming in the Ku frequency range (12 GHz to 14 GHz ).
The Programming
Satellite TV providers get programming from two major sources: national turnaround channels (such as HBO, ESPN and CNN) and various local channels (NBC, CBS, ABC, PBS and Fox affiliates in a particular area). Most of the turnaround channels also provide programming for cable television, and the local channels typically broadcast their programming over the airwaves.
Turnaround channels usually have a distribution centre that beams their programming to a geostationary satellite. The broadcast centre uses large satellite dishes to pick up these analogs and digital signals from several sources.
The broadcast centre converts all of this programming into a high-quality, uncompressed digital stream. At this point, the stream contains a vast quantity of data—about 270 megabits per second (Mbps) for each channel. In order to transmit the signal from there, the broadcast centre has to compress it. Otherwise, it would be too big for the satellite to handle.
Compression, Encryption and Transmission
The two major providers in the United States use the MPEG-2 compressed video format—the same format used to store movies on DVDs. With MPEG-2 compression, the provider can reduce the 270-Mbps stream to about 5 or 10 Mbps (depending on the type of programming). This is the crucial step that has made DBS service a success. With digital compression, a typical satellite can transmit about 200 channels. Without digital compression, it can transmit about 30 channels.
At the broadcast centre, the high-quality digital stream of video goes through an MPEG-2 encoder, which converts the programming to MPEG-2 video of the correct size and format for the satellite receiver in your house.
After the video is compressed, the provider needs to encrypt it in order to keep people from accessing it for free. Encryption scrambles the digital data in such a way that it can only be decrypted (converted back into usable data) if the receiver has the correct decryption algorithm and security keys.
Once the signal is compressed and encrypted, the broadcast centre beams it directly to one of its satellites. The satellite picks up the signal with an onboard dish, amplifies the signal and uses another dish to beam the signal back to the Earth, where viewers can pick it up.
The Dish and the Receiver
A satellite dish is just a special kind of antenna designed to focus on a specific broadcast source. The standard dish consists of a parabolic (bowl-shaped) surface and a central feed horn. To transmit a signal, a controller sends it through the horn, and the dish focuses the signal into a relatively narrow beam.
The end component in the entire satellite TV system is the receiver. The receiver has four essential jobs:
It de-scrambles the encrypted signal. In order to unlock the signal, the receiver needs the proper decoder chip for that programming package.
It takes the digital MPEG-2 signal and converts it into an analog format that a standard television can recognize. In the United States, receivers convert the digital signal to the analog NTSC format. Some dish and receiver setups can also output an HDTV signal.
It extracts the individual channels from the larger satellite signal. When you change the channel on the receiver, it sends just the signal for that channel to your TV.
It keeps track of pay-per-view programs and periodically phones a computer at the provider’s headquarters to communicate billing information.
While digital broadcast satellite service is still lacking some of the basic features of conventional cable (the ability to easily split signals between different TVs and VCRs, for example), its high-quality picture, varied programming selection and extended service areas make it a good alternative for some. With the rise of digital cable, which also has improved picture quality and extended channel selection, the TV war is really heating up.
Satellite television is similar to broadcast television in the way that it is ______for sending television programming directly to a viewer’s home.
选项
答案
a wireless system
解析
细节题。由题目中的Satellite television is similar to broadcast television找到小标题The Broadcast TV Problem下第一段前两句Conceptually, satellite television is, a lot like broadcast television. It’s a wireless system for delivering television programming directly to a viewer’s house. (从概念上来说,卫星电视和广播电视很相像,它也是一种直接无线传播电视节目的系统。)由此可得答案。
转载请注明原文地址:https://kaotiyun.com/show/RBI7777K
0
大学英语六级
相关试题推荐
Readingbecamedifficultfortheoldlady,sotheoptician______glasses.
Thedirectionswereso_______thatitwasimpossibletocompletetheassignment.
Forthispart,youareallowed30minutestowriteashortessayonthetopicofStudents’StartingTheirOwnBusinesses.Yoush
Forthispart,youareallowed30minutestowriteashortessayonthetopicofChildrenObesity.Youshouldwriteatleast150
A、Encouragethegrowthofreading.B、Changepeople’sattitudestoreading.C、Showhowreadingmethodshavebeenimproved.D、Expl
Inmostmessages,thereisanobviousmeaningthataliteralreadingofthewordsandsentencesreveals.Butthereisoftenanot
Inmostmessages,thereisanobviousmeaningthataliteralreadingofthewordsandsentencesreveals.Butthereisoftenanot
Inmostmessages,thereisanobviousmeaningthataliteralreadingofthewordsandsentencesreveals.Butthereisoftenanot
Inmostmessages,thereisanobviousmeaningthataliteralreadingofthewordsandsentencesreveals.Butthereisoftenanot
随机试题
心悸而烦、善惊梦多、食少泛恶、舌苔黄腻、脉滑数者,宜选用何方()(1996年第58题)
油藏动态分析必须以单井分析为单元,以油砂体为基础,分析油层内部的变化,搞清各类油层的开发状况及其动态变化规律,从而为改善油田的开发效果服务。()
慢性萎缩性胃炎临床表现可见
下列说法错误的是
患者,男,26岁。心悸,气促1年。查体:两颊暗红,颈静脉明显怒张,下肢浮肿,心浊音界向左扩大,心尖区可闻及舒张期隆隆样杂音,肝右肋下4cm,质软,有压痛,肝颈静脉回流征阳性。应首先考虑的是( )。
对经营性存款人违反规定不及时撤销银行结算账户的法律责任是( )。
胡锦涛同志在十八大报告中指出:扎实推进社会主义文化强国建设,建设社会主义文化强国,关键是增强全民族文化创造活力。加强社会主义文化建设的内容包括:
甲与同村的五名选民同时在外打工,不能回村参加乡人大代表的选举。甲的下列做法,符合法律规定的是()
论证有效性分析:分析下述论证中存在的缺陷和漏洞,选择若干要点,写一篇600字左右的文章,对该论证的有效性进行分析和评论。(论证有效性分析的一般要点是:概念特别是核心概念的界定和使用上是否准确并前后一致,有无各种明显的逻辑错误,论证的论据是否支持结论,论据成
Lookatthenotesbelow.Someinformationismissing.YouwillhearareportonE-money.Foreachquestion(16-22),fillinthem
最新回复
(
0
)