There are two fields that make up a frame, and 30 frames in a second of a black and white NTSC signal. The first color broadcast occurred in the United States in 1953. But due to some problems with the color information the frame rate was actually 29.97. NTSC stands for National Television System Committee. This standard is also used in many Asian countries.
Japan is one of the most important, becuase they manufacture most of the equipment.
NTSC has 525 lines per frame. Its vertical frequency is 60 Hz. The PAL standard was first transmitted in the early 1960's in most European countries except France and Russia. PAL stands for Phase Alternating Lines. The AC current in these countries is 220 volts at 50 cycles.