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AN003 Application Note

?? J. Styer, Sep 28, 2001

Most of the world television formats are based on three main television standards. These are known as NTSC, PAL and SECAM.? The official standard in the US is NTSC and all television broadcasts (except for the new HDTV) must meet this standard. In the UK, PAL is the dominant format. SECAM is used in France and Russia among other countries. PAL cameras are occasionally used with computers in the USA since PAL has more scan lines and therefore a bit more vertical resolution than NTSC. There are also numerous sub-standards within each standard but for the most part they are minor variations or combinations of the NTSC and PAL standards.

It is important to make sure your equipment works together. A device designed only for NTSC will likely not work with a PAL signal and vice versa. Since NTSC and PAL are similar in operation, it is possible to build certain types of equipment that support both standards. The SECAM standard is considerably different and therefore is not as common in multi standard equipment. This is important for all pieces of equipment in the chain. The key specs of NTSC and PAL differ as follows:

Vertical Frequency 59.94Hz commonly referred to as 60Hz 50Hz
Horizontal Frequency 15.73426Khz 15.650Khz
Chroma Frequency 3.579545Mhz 4.43Mhz
Scan Lines 525 Total 625 Total

As an absolute last resort, a standards converter may be used to change from one standard to another but this is not recommended if any better solution is available. There will always be losses in the conversion and the output will not have the same quality as the source signal.

NTSC and PAL only describe the system of color and are not the full specifications by themselves. B&W signals sometimes use these names or are referred to by their underlying standards. NTSC is based on the RS170(A) sync and timing specification. A B&W camera that is compatible with the US standard may be called NTSC compatible timing or RS170, with the latter being the more common choice. Similarly, B&W cameras destined for the UK may be referred to as PAL compatible or CCIR compatible.