CCIR System M


CCIR System M, sometimes called 525-line, NTSC, NTSC-M, or CCIR-M, is the analog broadcast television system approved by the FCC for use in the United States since July 1, 1941, replacing the 441-line TV system introduced in 1938. It is also known as EIA standard 170. System M comprises a total of 525 interlaced lines of video, of which 486 contain the image information, at 30 frames per second. Video is amplitude modulated and audio is frequency modulated, with a total bandwidth of 6 MHz for each channel, including a guard band.
It was also adopted in the Americas and Caribbean; Myanmar, Philippines, South Korea, Taiwan, Thailand, and Japan ''. System M doesn't specify a color system, but NTSC color encoding was normally used, with some exceptions: NTSC-J in Japan, PAL-M in Brazil and SECAM-M in Cambodia, Laos, and Vietnam.
The letter M designation was attributed by the ITU at the 1961 Stockholm meeting.
In 1965, Thailand decided to replace System M with the 625-line CCIR System B, which began implementation in 1967 and eventually adopted the PAL color standard.
Circa 2003, the transition from analog System M to digital television broadcasting began, and in 2009 the United States ended high power analog transmissions. Other nations such as Japan, South Korea, and Taiwan also transitioned to digital while the Philippines remain on analog transmissions with digital simulcasts.

Specifications

Some of the important specifications for System M are listed below:
  • Frame rate: 29.97 Hz, 30 Hz
  • Field rate: 59.94 Hz, 60 Hz
  • Lines : 525
  • Lines : 486
  • Line rate: 15.734 kHz
  • Visual bandwidth: 4.2 MHz
  • Vision modulation: Negative
  • Preemphasis: 75 μs
  • Sound modulation: FM
  • Sound offset: +4.5 MHz
  • Channel bandwidth: 6 MHz
  • Vestigial sideband: 0.75 MHz
  • Color standards: NTSC-M, NTSC-J, PAL-M, SECAM-M, Clear-Vision

    Color standards

NTSC-M and NTSC-J

Strictly speaking, System M does not designate how color is transmitted. However, in nearly every System M country, NTSC color encoding is used for color television. This combination is called NTSC-M, but usually simply referred to as "NTSC", because of the relative lack of importance of black-and-white television. In NTSC-M and Japan's NTSC-J, the frame rate is offset slightly, becoming frames per second, usually labeled as the rounded number 29.97.

PAL-M

The main exception to System M's being paired with NTSC color is Brazil, where PAL color is used instead, resulting in the PAL-M combination unique to that country. It is monochrome-compatible with other System M countries, but not compatible with other PAL countries, which use 625-line based systems.

SECAM-M

Between 1970 and 1991 a variation of the SECAM color system, known as SECAM-M, was used in Cambodia, Laos, and Vietnam.

Clear-Vision

is a Japanese EDTV television system introduced in the 1990s, that improves audio and video quality while remaining compatible with the existing System M broadcast standard. Developed to improve analog NTSC, it adds features like progressive scan, ghost cancellation and widescreen image format.