Most US NTSC broadcasters were required by the FCC to shut down their analog transmitters in 2009.
Low-power stations, Class A stations and translators were required to shut down by 2015.
The compatible color standard retains full backward compatibility with existing black-and-white television sets.
Color information was added to the black-and-white image by introducing a color subcarrier of precisely 315/88 MHz (usually described as 3.579545 MHz or 3.58 MHz).
The first NTSC standard was developed in 1941 and had no provision for color.In 1953 a second NTSC standard was adopted, which allowed for color television broadcasting which was compatible with the existing stock of black-and-white receivers.NTSC was the first widely adopted broadcast color system and remained dominant until the 2000s, when it started to be replaced with different digital standards such as ATSC and others.This blanking interval was originally designed to simply blank the receiver's CRT to allow for the simple analog circuits and slow vertical retrace of early TV receivers.However, some of these lines may now contain other data such as closed captioning and vertical interval timecode (VITC).The standard recommended a frame rate of 30 frames (images) per second, consisting of two interlaced fields per frame at 262.5 lines per field and 60 fields per second.Other standards in the final recommendation were an aspect ratio of 4:3, and frequency modulation (FM) for the sound signal (which was quite new at the time).The National Television System Committee was established in 1940 by the United States Federal Communications Commission (FCC) to resolve the conflicts that were made between companies over the introduction of a nationwide analog television system in the United States.In March 1941, the committee issued a technical standard for black-and-white television that built upon a 1936 recommendation made by the Radio Manufacturers Association (RMA).The NTSC standard has been adopted by other countries, including most of the Americas and Japan.With the advent of digital television, analog broadcasts are being phased out.