PAL is the analogue video format used in most of Europe (except France, Bulgaria, Russia, Yugoslavia, and some other countries in Eastern Europe, where SECAM is used), Australia and some Asian and African countries. The name PAL comes from Phase Alternating Line, which decribes the way that color information on the video signal is reversed in phase with each line, which prevents color artifacts that can affect NTSC encoded video signals. The format has 625 lines per frame and a refresh rate of 25 frames per second. Like NTSC it is an interlaced format. Each frame consists of two fields (half-a-frame), each field has half of the lines of a frame (one has all the even lines, one has all the odd lines). Fields are transmitted and displayed successively. There are 50 fields per second. At the time of its design the interlacing of fields was a compromise between flicker and bandwidth. PAL was first introduced in Germany in 1967.