What Is High Definition Television?

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High Definition Television (HDTV) is a new form of television that has a much higher quality image than standard television. While HDTV has received wide publicity in recent years, it is still in the experimental phase and is not yet commercially available.

The amount of detail shown in a television picture is determined by the number of lines of information and by the number of picture elements on each line. The latter is mostly determined by the width of the electron (negatively charged particle) beam that scans and reproduces images. To obtain a picture closer to that seen in movie theaters, HDTV uses more than twice the number of scan lines, with a much smaller picture element than standard television. In the United States and Japan, standard television has 525 scanning lines, and in Europe it has 625 scanning lines. HDTV uses more than 1,000 lines.

HDTV not only increases the sharpness of the image, but it displays a much more complete spectrum of colors and gives the image a three-dimensional effect. The quality of sound is the same as a compact disc's. And HDTV may be interactive, allowing the user to both receive and transmit information.

While RCA's Otto Schade first developed the concept of HDTV in the mid 1940s, the technology did not yet exist to bring his ideas to fruition. The Japanese broadcasting corporation NHK, generally credited with pioneering HDTV, began research on the new television system in 1968. At present, NHK broadcasts some high definition programs daily, using 1,125 scanning lines.

HDTV has faced many problems in the United States and in other parts of the world. One obstacle in the United States is the development of technical standards that meet Federal Communications Commission (FCC) requirements for use of commercial broadcast bands. The more immediate problem, however, is a technological one: HDTV requires the transmission of five times more data than is currently assigned to each television channel. A possible solution is signal compression—squeezing the 30 megahertz bandwidth signal that HDTV requires into the 6 megahertz bandwidth currently used for television broadcasting.

In 1994, the television industry accepted a signal transmission system developed by Zenith as the technical standard. And in 1996 the first "model" HDTV station, WHD-TV (owned by NBC), went into operation in Washington, D.C. On August 6, WHD-TV made its first broadcast and reception of HDTV.

HDTV sets have not yet been made available to the public. When they finally show up in stores, they will cost an estimated $3,500 to $5,000.

Sources: Ailes, Christopher. HDTV: A Thing of the Past or the Future? [Online] Available http://www.emerson.edu/acadepts/mc/cnme/tool/hdtv/hdtv.html, July 16, 1997; Brennan, Richard P. Dictionary of Scientific Literacy, pp. 140-41; Inglis, Andrew F. Behind the Tube: A History of Broadcasting Technology and Business, pp. 473-87; The New Book of Popular Science, vol. 6, p. 259.546; "NHK." Encyclopaedia Britannica CD 97; Popular Mechanics, vol. 171 (July 1994), pp. 90-91; WHD-TV Dedicated as Model HDTV Station Broadcasts First Live, On-Air Grand Alliance HDTV Signal. [Online] Available http://www.eia.org/cema/CESNEWS/FILES/prO796/whd-tv.htm, July 16, 1997.

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