CCIR System M

CCIR System M,[1][2][3] sometimes called 525–line, monochrome NTSC, NTSC-M, or CCIR-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. Video is amplitude modulated.[9]

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 the Americas and Caribbean; Myanmar, Philippines, 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 in Cambodia and Vietnam (see Color standards section below).

The letter M designation was attributed by the ITU at the 1961 Stockholm meeting (see ITU identification scheme).[10]

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

Specifications
Further information: Broadcast television systems § ITU identification scheme

Some of the important specifications for System M are listed below:[11]

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 Preemphasis Sound modulation Color Standards
M525 48029.97 (NTSC color)64.2+4.50.75Negative 75 μsFM NTSC-M
NTSC-J
PAL-M
SECAM-M
Clear-Vision
B-MAC
30 (original/PAL color)
  • Radio spectrum of a System M television channel with NTSC color
    Radio spectrum of a System M television channel with NTSC color
  • Plan showing VHF frequency ranges for ITU Systems
    Plan showing VHF frequency ranges for ITU Systems

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

NTSC-M and NTSC-J
Main articles: NTSC and NTSC-J

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 30⁄1.001 frames per second, usually labeled as the rounded number 29.97.

PAL-M
Main article: 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
Main article: SECAM

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

References
  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. ISBN 978-1-4799-5865-8. S2CID 11038252 – via IEEE Xplore.
  3. "C.C.I.R - DOCUMENTS OF THE Xlth PLENARY ASSEMBLY OSLO, 1966" (PDF).
  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". 2020 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB). pp. 1–5. doi:10.1109/BMSB49480.2020.9379925. ISBN 978-1-7281-5784-9. S2CID 232373635 – 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". 2016 8th IEEE Latin-American Conference on Communications (LATINCOM). pp. 1–5. doi:10.1109/LATINCOM.2016.7811615. ISBN 978-1-5090-5137-3. S2CID 11567258 – 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. Meadow, Charles T. (February 11, 2002). Making Connections: Communication through the Ages. Scarecrow Press. ISBN 9781461706915 – via Google Books.
  9. Rova, Andy (February 22, 2005). NTSC: Nice Technology, Super Color.
  10. Final acts of the European Broadcasting Conference in the VHF and UHF bands. Stockholm, 1961.
  11. "World Analogue Television Standards and Waveforms". 2007-05-15. Archived from the original on 2007-05-15. Retrieved 2023-04-13.

See also
  • 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
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