SECAM
Sequentiel couleur avec mémoire
SECAM (Sequentiel Couleur avec Mémoire, French for "sequential color with memory") is an analog color television system first used in France. SECAM uses frequency modulation to encode chrominance information. It is so named because it uses memory to store lines of color information, in order to eliminate the color artifacts found on systems using the NTSC standard. It was developed for the same purpose as PAL, but employs a different mechanism. R-Y and B-Y information is transmitted in alternate lines, and a video line store (a 64 µs delay line) is used to combine the signals. This means that the vertical colour resolution is halved relative to NTSC. It is however not halved compared to PAL, which also combines color information from adjacent lines at the decoding stage, in order to compensate for color subcarrier phase errors occurring during the transmission. This is normally done using a delay line borrowed from SECAM (the result is called PAL DL or PAL Delay-Line, sometimes interpreted as DeLuxe), but can be accomplished "visually" in cheap TV sets (PAL standard). Phase errors do not cause loss of color saturation in SECAM, although they do in PAL. SECAM is also free of the dot crawl problem commonly encountered with the other analog standards and first widely noticed with the Laserdiscs. Dot crawl can be removed from 'PAL standard'- and NTSC-encoded signals using a comb filter.
There are three varieties of SECAM: French SECAM, used in France and its former colonies MESECAM, used in the Middle East SECAM D/K, used in the Commonwealth of Independent States and Eastern Europe. (This is simply SECAM used with the D and K monochrome TV transmission standards.)
SOURCES:
http://en.wikipedia.org/wiki/SECAM