PAL-50
In color television technology, PAL-50 refers to the use of the PAL system of color transmission in connection with a refresh rate of 50 Hz. This is the case worldwide in the vast majority of countries that use PAL; PAL-50 is the "normal" PAL. The PAL-50 standards include PAL-B, PAL-C, PAL-D, PAL-G, PAL-H, PAL-I, PAL-K, PAL-L, and PAL-N. PAL-M is not one of them.
The " Phase Alternating Line " process, or PAL for short, is a process for color transmission (color coding process) in analog television . It was developed in Germany with the aim of solving the problem of unaesthetic, annoying color tone errors that often occur in the original American NTSC process . In contrast to NTSC, which is essentially only used in the NTSC-M variant, there are many subspecies of PAL that differ in some technical data (line frequency, channel bandwidth, frame rate, video frequency bandwidth, image-sound carrier distance, residual sideband, image modulation and tone modulation) and identified by an additional letter. In Germany and most other Western European countries, for example, on the VHF used frequencies PAL-B, on the UHF frequencies, however PAL-G; one speaks briefly of PAL-B / G. In the UK, however, the subspecies PAL-I is used.
With all PAL-50 variants, 625 picture lines are transmitted per full picture, of which, however, usually only about 575 lines are visible. For comparison: With PAL-60 and NTSC, 525 lines are transmitted, of which approx. 485 (sometimes only 480) are visible.
The lines not shown contain the vertical blanking interval and then give the receiving circuit some time to sufficiently stabilize again. More recently, various additional information is also sent in this area, e.g. B. Teletext or switchable subtitles . With PALplus , the missing 16: 9 information is transmitted in the invisible lines and some of the lines in the black bars at the top and bottom of the picture, "camouflaged" as blue color information, in order to achieve a picture quality similar to that even with appropriately equipped analog receivers anamorphic 16: 9 transmission via digital television. The importance of PALplus has been declining since digital television has become increasingly dominant. The various subspecies of PAL-50 also no longer play a role in digital television.