The interlaced scanning system Video images are generated using an interlaced scanning system. An image is scanned from left to right and from top to bottom. Each complete scan from top to bottom is known as a field, which is designated as field 1 or field 2. The combining or interlace of two fields creates a frame, For the UK and most of Europe, the PAL system (Phase Alternating Line) has 312M lines in each field and as a frame consists of two fields it is therefore made up of 625 scanning lines. The American NTSC system (National Television Standards Committee) uses 262% Sines per field and two fields per frame giving a total of 525 lines per frame. For the PAL system there are 25 frames per second and for NTSC there are 30 frames per second. In fact the NTSC system has a defined frame rate of 29.97 frames per second (see the discussion on timecode in Chapter 5 for more details). There is also the French system called SECAM (Sequential Couleur a Memoire), which uses 625 scanning lines with a repetition rate of 25 frames per second.