跪求一篇英语口语材料大概能说3分钟,描述一项家用电器.是大学里用的.

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The origins of what would bee today's television system can be traced back as far as the discovery of the photoconductivity of the element selenium by Willoughby Smith in 1873 and the invention of the scanning disk by Paul Nipkow in 1884. All practical television systems use the fundamental idea of scanning an image to produce a time series signal representation. That representation is then transmitted to a device to reverse the scanning process. The final device, the television (or T.V. set), relies on the human eye to integrate the result into a coherent image.
Electromechanical techniques were developed prior to World War II, most notably by Charles Francis Jenkins and John Logie Baird. Baird gave the world's first public demonstration of a working television system that transmitted moving images with tone graduation (grayscale) on 26 January 1926 at his laboratory in London. Baird further demonstrated the world's first color television transmission on 3 July 1928.
Completely electronic television systems relied on the inventions of Philo Taylor Farnsworth, Vladimir Zworykin and others to produce a system suitable for mass distribution of television programming. Farnsworth gave the world's first public demonstration of an all-electronic television system at the Franklin Institute in Philadelphia on 25 August 1934.
Regular broadcast programming occurred in the United States,[1] the United Kingdom,[2] Germany,[3] France,[4] and the Soviet Union[5] before World War II. The first regular television broadcasts with a modern level of definition (240 or more lines) were made in England in 1936, soon upgraded to the so-called System A with 405 lines. Large scale network broadcasting began in the United States in 1946, and television became mon in American homes by the middle 1950s. While North American over-the-air broadcasting was originally free of direct marginal cost to the consumer (i.e., cost in excess of acquisition and upkeep of the hardware) and broadcasters were pensated primarily by receipt of advertising revenue, increasingly United States television consumers obtain their programming by subscription to cable television systems or direct-to-home satellite transmissions. In the United Kingdom, on the other hand, the owner of each television must pay a licence fee annually which is used to support the British Broadcasting Corporation.
Elements of a television system
The elements of a simple television system are:
An image source - this may be a camera for live pick-up of images or