SECAM

SECAM (SÉquential Couleur à Mémoire, "Sequential Color with Memory") is an analog color television encoding system developed in France in the 1960s. It was designed to transmit color information separately from luminance, using a sequence approach that differs from the more common PAL and NTSC systems. SECAM was adopted in France and many Francophone countries, and was widely used in parts of Africa and Eastern Europe for several decades before digital television.

Technically, SECAM transmits the picture's brightness (luminance) as a conventional black-and-white signal. The color information is carried as two color-difference signals, but unlike PAL or NTSC these signals are not sent simultaneously. Instead, the system alternates transmitting the two color differences on successive lines or fields using a pair of subcarriers and frequency modulation. The receiver uses a memory (hence 'à mémoire') to hold chroma information from one line to the next, enabling color reconstruction. This design makes SECAM inherently robust against phase errors and some types of interference that degrade PAL/NTSC, and it avoids cross-color artifacts caused by incorrect subcarrier phase.

However, SECAM requires more complex receivers and broadcast infrastructure, and is not compatible with PAL or NTSC. As digital television spread, many countries migrated away from SECAM to DVB, MPEG-2/HEVC-based standards or other digital formats; some sectors still rely on SECAM domestically or on legacy equipment.

Related topics include analog color television, PAL, NTSC, and digital television standards.