Digital TV

Digital television (Digital TV), also known as HDTV, will eventually replace the current NTSC system, which was invented in the 1940s and 1950s. The goal of Digital TV is to greatly improve the picture and sound quality.

After nearly a decade of evaluating alterna tive Digital TV systems, the FCC has finalized the standards and decreed that Digital TV will eventu ally become the U.S. TV standard by 2006. The first Digital TV stations began transmission in the ten largest U.S. cities on September 1, 1998. Digital TV sets can now be purchased by the con sumer, but they are very expen sive. As more Digital TV stations come on line and as more Digital TV pro gramming becomes available, more consumers will buy Digital TV receivers and the cost will drop dramatically.

Advantages Of HDTV Television

HDTV Television signals are made up of coded instructions - the same 'bits' of 'ones and zeros' that make your computer work, and give life to your 'CD's' and 'DVD's' - which are transmitted to your Digital Receiver, (aka: Tuner, Decoder or Set-Top-Box "STB") which in turn deciphers the code. Your receiver isn't concerned with the signal strength, or what conditions exist between you and the transmitter. As long as the signal gets to the receiver, it can read the code and reproduce a near-perfect picture.

HDTV Television eliminates "snow" and "ghosting" caused by the weak signals from distant or blocked transmitting towers. If your analog TV set is not receiving a strong, undistorted signal from the tower, you will not get a perfectly clear picture.

Both HDTV Television and analog Televisin signals get weaker the farther they travel away from the transmitting tower. On an analog TV, the picture slowly deteriorates from bad to worse for more distant receivers. However, the picture on a HDTV Television set will stay perfect until the signal becomes too weak for the receiver to distinguish between a (1) and a (0), at which point the image disappears completely. HDTV Television displays pictures that contain significantly more detail, resulting in much 'crisper' pictures. Images viewed on TV screens are made up of small picture elements known as 'pixels.' Each of these pixels is made up of three, closely spaced 'dots' of color - red, blue and green. Combined together on the TV's phosphor screen, and viewed from a distance, the colors are seen as one. The phosphor at each of these dots emits light directly proportional to the intensity from the electron beam that hits it, as it scans across the screen.

On traditional, NTSC TV's 256 levels of intensity are possible for each of the three colors. The result is a range of 16.8 million colors for each pixel. The pixels in the analog system are slightly 'taller' than their width. Get up close to an analog screen - especially the larger projection sets - and you can easily see the red, blue and green rectangles. This is why distortion is sometimes seen on traditional, NTSC TV's.

The pixels in HDTV Television sets are square; they are also smaller, and spaced closer together. There can be (4 1/2) HDTV pixels in the same space that a single NTSC pixel requires. The result is that HDTV Television can display at least 4.5 times more detail than NTSC-analog TV.

HDTV Television sets are sold in two 'Aspect Ratios.' Aspect Ratio refers to the ratio between the horizontal (width) measurement and the vertical (height) measurement of the screen. This ratio is also used in reference to how the picture is transmitted and displayed on the screen.

The two aspect ratios used in HDTV Television are (4:3) and (16:9). That is, (4) units wide by (3) units high, and (16) units wide by (9) units high respectively.

HDTV Television vs.Standard Definition Television

As already stated, the ATSC has assigned (18) formats to Digital TV. At the current time, in HDTV Television we are primarily concerned with just two: 1080-i and 720-p. "True" HDTV Television may have, either 1080 interlaced lines, or 720 progressive-scanned lines. (Higher resolutions may be introduced in the future; for instance 1080-p, which is not currently used because of high manufacturing costs).