The physical layer of the computer network

1. Whether the data should be digital or analog should be determined by the nature of the data transmitted.

2. What is modulation? is the process of converting a digital signal to an analog signal.

What is the role of 3.PCM encoder? is to turn the analog signal into a digital signal.

4. ISM band is industrial,scientific,medical, industry, technology, medical abbreviation.

5. Electrical signals generally between the 200m/us~300m/us, away from the ground 36,000 km of satellites, upstream and downstream delay of about 270ms.

6. code element and digital channel.

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The physical layer of the computer network