There are three main formats of analog video signals; PAL\NTSC and SECAM, in which PAL is called P system and NTSC is called N system, as is often said.
PAL (phase Alternating Line) is a TV system established in 1965. With the exception of NTSC in parts of North America and East Asra and SECAM is adopted in most parts of the world, which serves 25 frames per second.
NTSC is the color television broadcasting standards formulated by National televition setting committee in 1952. It is adopted by most of the American countries, like America, Canada and Mexico, and China Taiwan, Japan, Korea and Philippine, as well as some TV company in Hongkong, South China. It serves 30 frames per second.
SECAM: At present, countries that adopted SECAM is mainly commonwealth of In dependent stares, such as Russia AND France, Egypt and some French-speaking countries
Therefore, in order to ensure that the analog video output of the movement can be used normally, movement will output two kinds of analog video: PAL and NTSC for choice。