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==Pre-emphasis=====Pre-emphasis===Pre-emphasis amplifies the high-frequency components through a simple Pre-emphasis circuit. In North America 75μs is used, and in Europe, 50μs is used. In order to have a normal frequency response, a De-emphasis circuit should be added to the radio receiver. Just as the same as Pre-emphasis circuit, it has a time interval after receiving the radio waves, and it is the same as the one of Pre-emphasis circuit.