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Television is a telecommunication system for broadcasting and receiving moving
pictures and sound over a distance . The term has come to refer to all the aspects of television programming and transmission as well. The word is derived from mixed Latin and Greek roots, meaning "far seeing". The origins of what would become today's television system can be traced back at least as far as the scanning disk of Paul Nipkow . All practical television systems use the fundamental idea of scanning an image to produce a time series signal representation which is then transmitted to a device which reverses the scanning process and which relies on the human eye to integrate the result into a coherent image again. While electromechanical techniques were developed extensively prior to World War II, most notably by John Logie Baird , all-electronic televison systems relied on the inventions of Philo Taylor Farnsworth , Vladimir Zworykin and others to produce a system suitable for mass distribution of television programming. Commercial broadcast programming, starting with experimental broadcasts seen only in a few specially-equipped homes, occurred in both the United States, and the United Kingdom before World War II, but television did not become commonplace in homes until the middle. While North American over-the-air broadcasting was originally free of direct cost to the consumer and supported primarily by advertising revenue, increasingly television consumers obtain their programming by subscription to cable television systems or direct-to-home satellite transmissions.
Practical telelvision systems include equipment for selecting different image sources, mixing images from several sources at once, insertion of pre-recorded video signals, synchronizing signals from many sources, and direct image generation by computer for such purposes as station identification. Transmission may be over the air from land-based transmitters, over metallic or optical cables, or by radio from synchronous satellites . Digital systems may be inserted anywhere in the chain to provide better image transmission quality, reduction in transmission bandwidth , special effects, or security of transmission from theft by non-subscribers.
An interesting factor to consider when planning your purchase of a new plasma television is altitude. Plasma TVs use millions of tiny, gas-flled chambers to create a picture. When you move to higher altitudes, the constant pressure in the chambers and the now lower ambient air pressure create a buzzing sound reminiscent of a halogen beer sign. This buzz is a combined result of the increased power consumption necessary to overcome the pressure differential, and the increase in fan use because the high power consumption heats the unit. This change in noise is really the only.
Published: September 12, 2006
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