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]
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.
Further information: Broadcast television systems § ITU identification scheme |
Some of the important specifications for System M are listed below:[11]
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 |
---|---|---|---|---|---|---|---|---|---|---|---|
M | 525 | 480 | 29.97 (NTSC color) | 6 | 4.2 | +4.5 | 0.75 | Negative | 75 μs | FM | NTSC-M NTSC-J PAL-M SECAM-M Clear-Vision B-MAC |
30 (original/PAL color) |
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.
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.
Main article: SECAM |
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).