电子信息类专业英语Unit_18_Digital_Television教材教学课件.pptVIP

;Text　　Television is the most widespread form of communication in the world. It is a system of sending and receiving pictures and sound by means of electronic signals transmitted through wires and optical fibers or by electromagnetic radiation. Television has a variety of application in society, business, and science. The most common use of television is as a source of information and entertainment for viewers in their homes.;　　Over the past years, digital technology has rapidly changed the world we live in. It changes the way we communicate, the way we do business and the way we learn. By way of example, the application of digital technology to our telephone service has not only improved the quality of service but has also enabled the development of value-added services such as interactive enquiry and phone-banking services. With the forthcoming third generation mobile phone technology, even multimedia services can be provided. The traditional television set will be turned into a multifunctional media receiver, meeting various demands of users. ;China launched its cable TV network plan in 2003, and will start digital satellite services in 2005. By the year 2008, digital technologies will be introduced to most parts of the country.　　What is Digital Television (DTV)?　　At present, our terrestrial television services are transmitted in analogue forms. Analogue transmission technology converts sound and pictures into continuously varying electric signals which, after transmission, are converted back to sound and pictures by television sets.;　　Digital television receivers, which convert the analog, or continuous, electronic television signals received by an antenna into an electronic digital code ( a series of ones and zeros), are currently available. The analog signal is first sampled and stored as a digital code, then processed, and finally retrieved. That means DTV is a new way of transmitting television services. Sound and pictures are processed electronically int