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当人们谈到电视时,立即想起家家户户普遍使用的电视机,每天接收电视广播节目。回顾历史,当初电视的发展确实是从无线广播开始,从黑白至彩色,都是模拟电视,由电视台通过高塔天线,使射频电磁波传送到家家户户的电视接收机,但广播范围是有限的。如果中央电视台节目要向全国广播,那就需要用无线通信网,把电视信号传送至各地,由地方电视台无线转播。通信网配合电视广播事业,承担电视节目长途传输的业务。近年各地城市建筑高楼大厦,电视台天线辐射的电磁波受到高楼的反射,产生多个不同途径和不同延时的电磁波,当其传送至每家的电视机时,在接收屏幕上出现画面的重影,使无线电视广播的收看质量大受损害。为了克服无线传播的这种不良影响,保证收看质量;又为了能够提供更多频道的电视节目,满足大众自由选看的要求,各地区纷纷建立有线电视(CATV)广播网,
When people talk about television, they immediately think of television sets that are widely used by every household and receive television and radio programs every day. Looking back at history, the original development of television did start from radio broadcasting. From black and white to color, it was an analog TV. The television station passed the tower antenna to transmit radio frequency electromagnetic waves to television receivers of every household, but the broadcasting range was limited. If CCTV programs broadcast to the whole country, they need to use wireless communication networks to transmit television signals to different places and broadcast them wirelessly by local TV stations. Communication network with the television broadcasting business, to undertake long-distance transmission of television business. In recent years, all over the city buildings in high-rise buildings, television antennas radiating electromagnetic waves by the high-rise reflection, resulting in a number of different ways and different delays in electromagnetic waves, when transmitted to each of the television, the screen appears ghosting on the screen, So that the quality of wireless television broadcasts greatly jeopardized. In order to overcome the adverse effects of wireless transmission and ensure the quality of viewing, in order to be able to provide more channels of television programs and satisfy the public’s free choice of viewing, various regions have set up cable television (CATV) broadcasting networks,