Analog TV systems in various countries
TV is transitioning to digital, and international cooperation should use fewer digital systems to change the current analog TV system too many problems, to facilitate program conversion and exchange, if each country engages in a set of independent intellectual property systems, then give programs Recording, playback and equipment manufacturing will bring a series of problems.
Most people may know that analog TV has three standards such as NTSC, PAL, and SECAM, but this only refers to the color system. In fact, from the black and white TV, there are several scan line number standards because of the different power frequency of the power supply. Others include video bandwidth, The differences in sound modulation methods, etc. are combined to form several analog TV systems in the world, which are distinguished by Latin letters, as shown in the following table: 
For example: Mainland China uses the PAL-D system, while Hong Kong uses the PAL-I system. The two mainly differ in the carrier frequency difference between the sound and the image. With a single system TV, you cannot receive the sound of another system. Some places in the Pearl River Delta will feel very obvious, because some town cable TV stations use Hong Kong ’s PAL-I equipment, often some channels are PAL-D signals, while others are PAL-I signals, and only dual systems can be used. TV watching.
Countries / regions where some formats are used (Note: This information is older and the only source, and the correctness has not been verified):
A / I: Ireland, United Kingdom, Hong Kong
B: South Yemen, Algeria, Australia, Austria, Congo, Cyprus, Denmark, Egypt, Ethiopia, Finland, Germany, Ghana, Iceland, India, Iran, Israel, Italy, Kenya, Kuwait, Liberia, Malaysia, Malta, Mauritius, Morocco , Netherlands, New Zealand, Nigeria, Norway, Pakistan, Portugal, Saudi Arabia, Spain, Sweden, Switzerland, Syria, Turkey, Yugoslavia, Tanzania
C: Belgium
D: China, Albania, Bulgaria, Czech Republic, Hungary, Poland, Romania, Soviet Union
E: Morocco, Ivory Coast, France, Algeria
F: Luxembourg
G: Austria, Belgium, Denmark, Finland, West Germany, Italy, Libya, Netherlands, Portugal, Spain, Sweden, Switzerland
H: Belgium, Yugoslavia
L: France, Malaysia
M: Brazil, Cambodia, Canada, Colombia, Cuba, Dominica, Ecuador, Guatemala, Haiti, Honduras, Japan, North Korea, Mexico, Nicaragua, Peru, Philippines, Saudi Arabia, Thailand, United States, Uruguay
N: Argentina, Jamaica, Venezuela
NTSC: United States, Canada, Mexico, Central America, Bolivia, Chile, Colombia, Ecuador, Japan, North Korea, Taiwan, Philippines, Jamaica, Caribbean Islands
PAL: Western Europe (Austria, Belgium, Denmark, Finland, Germany, Netherlands, Italy, Norway, Portugal, Sweden, Switzerland), Australia, Malaysia, Thailand, New Zealand, Hong Kong, Singapore, China
SECAM: France, Bulgaria, Hungary, Monaco, Poland, the former Soviet Union, Eastern European countries, Iran, Iraq, Guyana (attentive people can see the content beyond the technology included, such as geopolitics, colonial history, etc. The information may write interesting historical stories)
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