While the NTSC was discussed in this article - http://e-articles.info/e/a/title/NTSC/ (opens in new window) - below ware described the other 2 international TV broadcasting standards.
The United States pioneered color television, and the rest of the world learned from its mistakes. The NTSC system is used only in North America and Japan. The rest of the world does things a bit differently. Most of the world uses a color system called PAL. France and most of the nations that were the USSR, such as Russia and Ukraine, use a system called SECAM.
With the benefit of hindsight, the engineers who developed the PAL standard added a twist to the signals they used for color television. By reversing the phase of one of the chrominance signals (R-Y) after every scan line, they were able to make the color in an image more stable. Any phase distortion that arises during the broadcast of such a signal can be reduced by the use of a simple delay line in a television receiver. The change of phase gave the system its name-PAL stands for Phase Alternating Line.
By itself, the change of phase doesn't yield higher resolution. When PAL was developed, however, the engineers chose different parameters that do yield a better image. Most nations that use PAL have a power line frequency of 50 Hz instead of the 60 Hz common in North America. Consequently, they chose 50 Hz as the field rate (yielding a frame rate of 25 Hz). This change allowed time to put more lines on the screen, 625 in PAL. To improve horizontal resolution, most PAL systems use a subcarrier frequency of 4.43 MHz, allowing both luminance and chrominance a wider bandwidth.
In 1959 France developed a system called Sequence Couleur a Memoire (in English, sequential color with memory), commonly known by its abbreviation, SECAM. Instead of one quadrature modulated color subcarrier, SECAM uses two FM subcarriers, one for each chrominance signal. The luminance portion of its signal is the same as PAL with the same frame rate and line count. Table below summarizes the characteristics of the major television standards used in the world today.
International Television Standards
| Name | Field rate | Frame rate | Lines per frame | Sub-carrier type | Sub-carrier freq | Audio carrier offset | Channel width |
| Units | Hz | Hz | None | None | MHz | MHz | MHz |
| NTSC | 59.94 | 29.97 | 525 | AM | 3.58 | 4.5 | 6 |
| PAL | 50 | 25 | 625 | AM | 4.43 | 6 | 8 |
| PAL-M | 59.94 | 29.97 | 525 | AM | 4.43 | 6 | 8 |
| PAL-N | 50 | 25 | 625 | AM | 3.58 | 4.5 | 6 |
| SECAM | 50 | 25 | 625 | FM | 4.43 | 6 | 8 |
The signals of all three color systems are mutually incompatible. The different number of pixels alone is sufficient to guarantee that images meant for the European systems won't work with NTSC. Even videotapes must be translated to move their images between any two of the standards, a process that uses a device appropriately called a standards converter.
As long as you stick to one standard, you shouldn't encounter problems. However many video accessories for PCs are available to meet NTSC, PAL, and SECAM specifications. Be sure to match the standard you buy to what you want to watch-and what's compatible with the video system you intend to use.
Our website is not responsible for the information contained by this article. Webworldarticles.com is a free articles resource thus practically any visitor can submit an article. However if you notice any copyrighted material, please contact us and we will remove the article(s) in discussion right away.
This article was sent to us by:
Jacques Trichot at
06182010
1. Buying Your First LCD TV
All articles in this directory are property of their respective authors. Additionally, read our Privacy Policy
© 2010 WebWorldarticles.com - All Rights Reserved. Partners: Gunblade Saga