A tuner converts over-the-air (OTA) radio frequency transmissions into audio and video signals used by receiving devices to create picture and sound. NTSC (National Television System Committee) and ATSC (Advanced Television Systems Committee) are two standards for television transmission that require separate tuners. NTSC is an analog standard that has been in place since 1941, and ATSC is a digital standard adopted in 1995.
NTSC was developed for use with black-and-white television in 1941 and was modified in 1953 to allow for color broadcasts. This new color standard for color televisions was designed to be backward compatible with black-and-white broadcasts for which the standard was originally created.
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ATSC was developed by the Grand Alliance, a consortium designed to develop high-definition television (HDTV) standards in the early 1990s to support digital broadcasts of much higher picture quality and sound than the NTSC standard.
NTSC and ATSC tuners convert over-the-air television transmission signals into audio and video signals for use with a display device (e.g., television). A tuner's specific tasks include demodulation to extract the specific signal, error correction, demultiplexing to extract the specific channels, decompressing the signal, synchronizing the audio and video signals and formatting the signal to the optimal input for a display device. While these two types of tuners perform the same functions, NTSC tuners are designed to work with analog signals and ATSC tuners work with the much larger digital signals.
NTSC tuners support analog signals and use a standard frame refresh rate of slightly under 30 frames per second, 525 scan lines, an aspect ratio of 4:3 and a frequency modulation (FM) sound signal.
ATSC tuners support HDTV signals with a wide-screen aspect ratio of 16:9, resolutions ranging from 352 x 288 pixels to 1920 x 1080 pixels, refresh rates ranging from 24 to 60 frames per second and Dolby Digital 5.1 surround sound.
Transition from Analog to Digital TV
Congress mandated that ATSC broadcasts replace NTSC broadcasts in the United States by June 12, 2009. Similarly, Canada will convert by Aug. 31, 2011, and Mexico will convert by Dec. 31, 2021. The switch requires consumers to purchase digital-to-analog converter boxes to receive ATSC broadcasts on their old analog TVs.
TVs sold in the U.S. since May 2007 are required by the Federal Communications Commission (FCC) to have built-in digital tuners. ATSC has been widely adopted by the U.S., with other countries such as Canada and South Korea planning complete transitions by 2012.
NTSC-M is the analog color television standard adopted by the U.S., Canada, Mexico and several Caribbean, Central American, South American and Asian countries. Japan adopted a variant of NTSC-M, called NTSC-J, which uses minor differentiations in color voltage levels.
Most European countries use the PAL-M standard, which uses different color encoding with the same bandwidth levels and frame rate. As a result, NTSC tuners will display PAL broadcasts in black in white because it cannot decode the color information.