625-line (or CCIR 625/50) is a late 1940s
Europeananalogstandard-definition television resolution standard.[1][2] It consists of a 625-line
raster, with 576 lines carrying the visible image at 25
interlacedframes per second. It was eventually adopted by countries using 50 Hz
utility frequency as regular TV broadcasts resumed after World War II.[3] With the introduction of color television in the 1960s,[4] it became associated with the
PAL and
SECAM analog color systems.
A similar
525-line system was adopted by countries using 60 Hz utility frequency (like the
US). Other systems, like
375-line,
405-line,
441-line,
455-line and
819-line existed, but became outdated or had limited adoption.
The modern standard-definition
digital video resolution
576i is equivalent and can be used to
digitize an analogue 625-line TV signal, or to generate a 625-line compatible analog signal.[5]
At a CCIR
Geneva meeting in July 1950, Dr. Gerber (a Swiss engineer), proposed a modified 625-line system using a 7 MHz channel bandwidth - informally known as the "Gerber Standard". The system was based on work by
Telefunken and
Walter Bruch, and was supported by
Belgium,
Denmark,
Italy,
Netherlands,
Sweden and
Switzerland.[3]
At a CCIR Geneva meeting in May 1951, the existing
VHF broadcast standards were standardized.[3] The older 405-line system was designated
CCIR System A, the Gerber Standard was designated
System B, the Belgian variant
System C and the I.B.T.O. standard
System D.
In the 1960s, with the introduction of
UHF broadcasts, new 625-line standards were adopted, again with slightly different broadcast parameters, leading to the creation of Systems
G,
H,
I,
K and
L.
The following
analog television color systems were used in conjunction with the previous standards (identified by a letter after the colour system indication):
PAL analog color television system (ex: PAL-B, PAL-D, etc.)
SECAM analog color television system (ex: SECAM-D, SECAM-L, etc.)