525-line (or EIA 525/60) is an American standard-definition television resolution used since July 1, 1941, mainly in the context of analog TV broadcast systems. It consists of a 525-line raster, with 480 lines carrying the visible image at 30 interlaced frames per second. It was eventually adopted by countries using 60 Hz utility frequency as TV broadcasts resumed after World War II. With the introduction of color television in the 1950s, it became associated with the NTSC analog color systems.
The system was given their letter designation as CCIR System M in the ITU identification scheme adopted in Stockholm in 1961.
A similar 625-line system was adopted by countries using 50 Hz utility frequency. Other systems, like 375-line, 405-line, 441-line and 819-line existed, but became outdated or had limited adoption.
The modern standard-definition digital video resolution 480i is equivalent to 525-line and can be used to digitize a TV signal, or to it playback generating a 525-line compatible analog signal.
The following International Telecommunication Union standards use 525-lines:
The following analog television color systems were used in conjunction with the previous standards (identified by a letter after the color system indication):
525-lines is sometimes mentioned when digitizing analog video, or when outputting digital video in an standard definition analog compatible format.