PAL, NTSC, as well as SECAM, are the world's three analog color TV technology standards. This standard is for television station and television to implement a video and audio signal together. Only under the same technical standards, can be able to achieve the TV signal normal acceptance. This is just like the power outlet and plug, only the same type can be plugged together. China's plug can not be inserted in the UK standard power outlet.
Color TV image display is composed of mixed signal of three primary colors red, green and blue. The brightness degree of the three colors makes the colorful images. How to deal with the three primary color signals and to achieve broadcast and receive, this needs a certain technical standards, which formed a color TV standard. So comes the three TV system: NTSC (also known as N system, or the United States standard), PAL system (also known as Parr or West Germany, UK), SECAM system (also known as Sekon system or French system). The main differences between these three systems are frame frequency (field frequency), the decomposition rate,signal bandwidth and carrier frequency, relationship of color space conversion,etc.
PAL (Phase Alternating Line), is a television system developed in 1965, mainly used in China, Hong Kong, the Middle East and Europe. This system is with color bandwidth of 4.43Mh, audio bandwidth of 6.5Mhz, 25 frames per second.
NTSC (National Television System Committee) standard is made by the United States National Television Development Committee in 1952. The United States, Canada, and Japan, China Taiwan, South Korea, the Philippines and other countries use this standard. This system is with color bandwidth of 3.58Mhz, audio bandwidth of 6.0Mhz, 30 frames per second picture.
Why NTSC system is 30 frames per second while PAL system is 25 frames per second ? This is because the country's electricity is 110V \ 60HZ, so the TV field frequency signal directly get the frequency AC 60HZ, and two constitute a frame, so 60 divided by 2 is equal to 30, which is the number of TV frames. China's electricity is 220V \ 50HZ, so it’s 25 per second.