CCIR System M explained

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 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.^[9]

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, Laos 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]

In 1965, Thailand decided to replace System M with 625-line CCIR System B, which started in 1967, adopting PAL at the same time.^[11]

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

Specifications

Some of the important specifications for System M are listed below:^[12]

• Lines (total): 525
• Lines (visible): 486
• Frame rate: 29.97 Hz (NTSC color), 30 Hz (monochrome and PAL-M color)
• Channel bandwidth: 6 MHz
• Visual bandwidth: 4.2 MHz
• Sound offset: +4.5 MHz
• Vestigial sideband: 0.75 MHz
• Vision modulation: Negative
• Preemphasis: 75 μs
• Sound modulation: FM
• Color standards: NTSC-M, NTSC-J, PAL-M, SECAM-M, Clear-Vision, B-MAC

Color standards

NTSC-M and NTSC-J

See main article: 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 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

See 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

See main article: SECAM. Between 1970 and 1991 a variation of the SECAM color system, known as SECAM-M, was used in Cambodia,^[13] Laos, and Vietnam (Hanoi and other northern cities).

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 and System N audio carriers
• Pan-American television frequencies

Notes and References

1. Book: Korea Electronics Association . Journal of Korean Electronics . 1991.
2. Book: 2015 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting . Rodney Martínez. Alonso. Ernesto Fontes. Pupo. Changyong. Pan. Co-channel and adjacent channel interference in DTMB with 6MHz channel bandwidth . June 10, 2015. 1–5. IEEE Xplore. 10.1109/BMSB.2015.7177274. 978-1-4799-5865-8 . 11038252 .
3. Web site: C.C.I.R - Documents of the Xlth Plenary Assembly Oslo, 1966 .
4. Book: https://ieeexplore.ieee.org/document/9379925. Protection ratios and overload thresholds between 700 MHz FDD-LTE and analog/digital terrestrial television. Ernesto Fontes. Pupo. Rufino Cabrera. Alvarez. Alejandro González. García. Reinier Díaz. Hernández. 2020 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB) . October 10, 2020. 1–5. IEEE Xplore. 10.1109/BMSB49480.2020.9379925. 978-1-7281-5784-9 . 232373635 .
5. Book: https://ieeexplore.ieee.org/document/7811615. Interference between UHF analog/digital television and LTE APT 700 MHz band: A field evaluation. Martínez. Odiaga. Hansel. Joussef. Yarlequé. Medina. Manuel. Augusto. 2016 8th IEEE Latin-American Conference on Communications (LATINCOM) . November 10, 2016. 1–5. IEEE Xplore. 10.1109/LATINCOM.2016.7811615. 978-1-5090-5137-3 . 11567258 .
6. Book: Pursell, Carroll. A Companion to American Technology. April 30, 2008. John Wiley & Sons. 9780470695333 . Google Books.
7. Book: Herbert, Stephen. A History of Early Television. June 21, 2004. Taylor & Francis. 9780415326681 . Google Books.
8. Book: Meadow, Charles T.. Making Connections: Communication through the Ages. February 11, 2002. Scarecrow Press. 9781461706915 . Google Books.
9. Book: Rova, Andy . NTSC: Nice Technology, Super Color . February 22, 2005.
10. http://www.itu.int/dms_pub/itu-r/opb/act/R-ACT-RRC.1-1961-PDF-E.pdf Final acts of the European Broadcasting Conference in the VHF and UHF bands. Stockholm, 1961.
11. Web site: The Project of Nationwide Television Broadcasting Network in Thailand . Overseas Technical Cooperation Agency, Government of Japan . 4 March 2024 . 234 . January 1967.
12. Web site: 2007-05-15 . World Analogue Television Standards and Waveforms . 2023-04-13 . https://web.archive.org/web/20070515044128/http://www.pembers.freeserve.co.uk/World-TV-Standards/Transmission-Systems.html#CCIR . 2007-05-15 .
13. Book: Broadband Data Book . Cisco . August 2019 . 31.