CCIR System M


CCIR System M,[1][2][3] sometimes called 525–line, monochrome NTSC or NTSC-M,[4][5] is the analog broadcast television system approved by the FCC (upon recommendation by the National Television Systems Committee - NTSC)[6] for use in the United States since July 1, 1941,[7][8] replacing the 441-line TV system introduced in 1938.[8] System M displays a total of 525 lines of video (with 480 carrying visible image information) at 30 frames per second using 6 MHz spacing between channel numbers, and is used for both VHF and UHF channels.

Television line count by nation; countries that are using System M or J currently or have used them prior to digital switchover, are in green.

It was also adopted in most of the Americas and Caribbean, South Korea,Taiwan and Japan (here with minor differences, informally referred to as System J). System M doesn't specify a color system, but NTSC (NTSC-M) was normally used, with some exceptions: NTSC-J in Japan, PAL-M in Brazil and SECAM-M on Cambodia and Vietnam (see Color standards section below).

The letter M designation was attributed by the ITU on the 1961 Stockholm meeting (see ITU identification scheme).[9]

Since 2015, System M is being replaced by digital broadcasting, in countries such as the Americas, Japan, South Korea, Taiwan and the Philippines.


Radio spectrum of a System M television channel with NTSC color
Plan showing VHF frequency ranges for ITU Systems
World television systems
System(CCIR) Lines (total) Lines (visible) Frame rate (fps) Channel bandwidth (MHz) Visual bandwidth (MHz) Sound offset (MHz) Vestigial sideband (MHz) Vision modulation Sound modulation Notes
M 525 480 29.97 (NTSC color) 6 4.2 +4.5 0.75 Negative FM Most of the Americas and Caribbean; Myanmar, Philippines, South Korea, Taiwan (all NTSC-M)
Japan (NTSC-J)
Brazil (PAL-M)
Cambodia, Vietnam (SECAM-M).
30 (original/PAL color)

Color standardsEdit

Television color encoding by nation; Brazil (PAL-M) and all green countries (NTSC) are based on monochrome System M.


Strictly speaking, System M does not designate how color is transmitted. However, in nearly every System M country NTSC is used for color television. This combination called 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 301.001 frames per second, usually labeled as the rounded number 29.97.


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.


Between 1970 and 1991 a variation of the SECAM color system, known as SECAM-M, was used in Cambodia and Vietnam (Hanoi and other northern cities).


  1. ^ Korea Electronics Association (1991). Journal of Korean Electronics (PDF).
  2. ^ Alonso, Rodney Martínez; Pupo, Ernesto Fontes; Pan, Changyong (June 10, 2015). ""Co-channel and adjacent channel interference in DTMB with 6MHz channel bandwidth"". pp. 1–5. doi:10.1109/BMSB.2015.7177274 – via IEEE Xplore.
  4. ^ Pupo, Ernesto Fontes; Alvarez, Rufino Cabrera; García, Alejandro González; Hernández, Reinier Díaz (October 10, 2020). "Protection ratios and overload thresholds between 700 MHz FDD-LTE and analog/digital terrestrial television". pp. 1–5. doi:10.1109/BMSB49480.2020.9379925 – via IEEE Xplore.
  5. ^ Odiaga, Martínez; Joussef, Hansel; Medina, Yarlequé; Augusto, Manuel (November 10, 2016). "Interference between UHF analog/digital television and LTE APT 700 MHz band: A field evaluation". pp. 1–5. doi:10.1109/LATINCOM.2016.7811615 – via IEEE Xplore.
  6. ^ Pursell, Carroll (April 30, 2008). A Companion to American Technology. John Wiley & Sons. ISBN 9780470695333 – via Google Books.
  7. ^ Herbert, Stephen (June 21, 2004). A History of Early Television. Taylor & Francis. ISBN 9780415326681 – via Google Books.
  8. ^ a b Meadow, Charles T. (February 11, 2002). Making Connections: Communication through the Ages. Scarecrow Press. ISBN 9781461706915 – via Google Books.
  9. ^ Final acts of the European Broadcasting Conference in the VHF and UHF bands. Stockholm, 1961.

See alsoEdit

  • NTSC — dominant color system used with System M, so much so that System M is often referred to as "NTSC". Much of the information in the NTSC article is actually about System M.
  • Broadcast television systems — explains other types of television system standards
  • Multichannel television sound — usual method for adding stereo to System M audio