PAL, short for Phase Alternating Line, is a colour-encoding system used in broadcast television systems in large parts of the world. Other common analogue television systems are SECAM and NTSC. This page discusses the colour encoding system only. See Broadcast television systems and analogue television for discussion of frame rates, image resolution and audio modulation. For discussion of the 625-line 25 frame/s television standard, see 576i.
In the 1950s, when the Western European countries were planning to establish colour television, they were faced with the problem that the already existing American NTSC standard would not fit the 50 Hz AC frequency of the European power grids. In addition to that NTSC demonstrated several weaknesses, including colour tone shifting under poor transmission conditions. For these reasons the development of the SECAM and PAL standards began. The goal was to provide a colour TV standard with a picture frequency of 50 fields per second (50 hertz), and sporting a better colour picture than NTSC.