ever have in grown popularity with this 5) NI R - The Russian system that is the same as provide a compromise to which all the system. Fortuitously, the war in Korea NTSC except that the phase modulation, countries of Europe could agree. caused a shortage of copper which but not the amplitude modulation, of the subcarrier is prevented color receivers being built at omitted on alternate lines, 6)SECAM - Sequential with memory, and this time, so it was possible for the FCC to International adopt the 7) PAL - Phase alternation by lines. exchange present NTSC system in 1953 of programs without any public outcry from the peo- Of these seven systems, only the last two ple who had purchased field -sequential have been extensively tested by members All the tv systems, receivers. both monochrome and of the European Broadcast Union(EBU), color, can operate from movie film and and are in use at this time. France and the this is still the simplest method of systems USSR are using the SECAM system, program exchange between all systems. while most of the other countries of The NTSC color television system, as Europe are using, or have stated they will Monochrome programs can also be ex- used in the USA since 1953, was the only use PAL. changed by video tape, microwave, and system used in until mid satellites between countries using the 1967. At present, England and Germany same scanning standards. In some cases use the PAL system and France uses the The PAL signal is the same as the NTSC there will be a reduction in picture quality SECAM system. Again it may be asked, signal except that the phase of the R- Y because of the difference in video "Why is there not some international component of the color subcarrier is bandwidth between the systems. standardization?" Again there is no reversed (changed by 180 °) every line. technical argument in favor of more than The claimed advantages of this system are Very satisfactory electronic standard one system. that it has good immunity to phase and converters are also available for con- differential phase errors, and also that verting between systems having the same In the early days of NTSC color broad- ghosts do not change the color of the field frequency, and these are used quite casting, there were some technical received pictures and are visible only as a extensively in Europe at the present time. difficulties resulting in unsatisfactory change of brightness. The important dis- Satisfactory standard converters have color pictures on certain occasions. These advantage of PAL is the increase in cost also been built for converting between 50 difficulties were all due to shortcomings of the home receivers. To achieve the and 60 field systems. Previously, optical of the apparatus in use at the time and advantages of PAL, each receiver must converters that consist of a camera have been completely overcome in have a delay line (64 µs). focused on a picture monitor were used, modern equipment. The three important but they had poor resolution and also difficulties in the early days of NTSC introduced substantial . In addition, were: SECAM uses an fm color subcarrier that there was usually some 10 -cycle flicker carries the color -difference signals se- output. quentially R- Yon one line and B- Yon the I) Errors in hue due to differential phase in next line. A delay line in the receiver International exchange of color equipment, provides the necessary storage for making programs is more complex. Even if there 2) Errors in saturation due to , R- Y and B- Y available for display at the were only one color system, say NTSC, and same time. The SECAM system has throtghout the world, there would still 3) Errors in hue due to the phase of the color greater tolerance to differential gain and have to be six different standards for the subcarrier burst being inconsistent in rela- differential phase than NTSC, but it also signals if color were to be tion to the color information in the picture. has many shortcomings compared with used with all the monochrome systems. These shortcomings were, of course, NTSC, the important ones being: reduced These different standards are indicated known to engineers in Europe and a large resolution of color in both the vertical by arbitrary numbers in the right -hand number of different color systems were and horizontal direction; poor com- column of Table I. Fortunately, agree- developed to overcome the difficulties. patibility with monochrome receivers; ment has been reached in the CCIR that Very little work was done in Europe to greater sensitivity to noise, and difficulty color tv will be confined to 625 -line eliminate the cause of problems in the of mixing signals in the studio. Also, of systems in Europe; thus only three color NTSC system, but this has been done course, the receivers must have a delay standards would be necessary if only one quite successfully in the United States. All line. color system were to be used. the color tv systems developed in Europe were the same as NTSC except for the The NIR system, sometimes called For exchange of color programs between method of encoding the color- difference SECAM -IV, is the same as NTSC except countries to be accomplished easily, other signals; they are: that the phase of the color subcarrier is than by means of film, not only must the held constant at a reference value on scanning standards be the same, but the alternate lines. The amplitude modula- color standards must also I)TSC - The two subcarriers systems, be the same. tion of the subcarrier is the same as NTSC The CCIR has obtained agreement that 2)FAM - The frequency and amplitude modulation systems, on all lines. The only advantage of NIR the color subcarrier frequency will be 4.43 appears to be that it is not the same as in 625 50 3) DST - The fm subcarriers system with an MHz Europe for the -line -field additional subcarrier on the color sub- NTSC, PAL, and SECAM. The NIR systems, but this frequency is not suitable carrier, system was strongly recommended by a for system "N" which is used in some 4) ART - The added reference transmitter few people at the 1966 meeting of the South American countries, because the system, CCIR, because they thought that it might vision -to -sound carrier spacing is only 4.5

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