From Sega Retro
NTSC is the analog television system in use in the United States and many other countries, including most of the Americas and some parts of East Asia. It is named for the National Television System(s) Committee, the industry-wide standardization body that created it.
The NTSC format—or more correctly the M format—consists of 30/1.001 (approximately 29.97) interlaced frames of video a second, each consisting of 480 lines of vertical resolution out of a total of 525 (the rest are used for sync, vertical retrace, and other data such as captioning). The NTSC system interlaces its scanlines, drawing odd-numbered scanlines in odd-numbered fields and even-numbered scanlines in even-numbered fields, yielding a nearly flicker-free image at its approximately 59.94 Hz refresh frequency. This compares favorably to the 50 Hz refresh rate of the 625-line PAL and SECAM video formats used in Europe, where 50 Hz alternating current is the standard; the European standards have noticeably more flicker than NTSC. Interlacing the picture does complicate editing video, but this is true of all interlaced video formats, including PAL and SECAM.
NTSC was originally a monochrome signal running at 30 frames per second. During the transition from monochrome to color television, certain interference constraints needed to be satisfied among the horizontal, sound, and color frequencies. These constraints were resolved by reducing the 60.00 Hz field rate of monochrome television by a factor of exactly 1000/1001 to create the color NTSC field rate of 60/1.001 Hz (approximately 59.94 Hz).
Countries that use NTSC