The relationship between communication and DC is far more complicated than you think.
The same is electricity, why should we divide DC and exchange?
Have you ever thought about why the charging plug of a mobile phone is larger than a normal plug? In fact, strictly speaking, this "plug" is called a switching power adapter, and the purpose is to convert the AC power from the power grid into DC power into the electronic device. 220 volts / 50 Hz AC is China's power supply standard, so many people think that household appliances are all AC, but it is not.
DC is referred to as DC, which refers to the current whose direction does not change with time, also known as "constant current".
AC, abbreviated as AC, refers to a current that changes periodically in both size and direction.
AC power is common in our lives. Our household electricity uses alternating current. AC has a typical advantage, and that is convenience. Everyone knows that the electricity we use has zero change and two lines of fire. Take the 220V electricity of the household. The potential of the zero line is 0V. The fire line generates and subtracts the corresponding potential for the zero line because of the time. The current is one direction. When the current is subtracted, the current is one aspect. This forms a current that alternates direction, so it is called alternating current.
Observing from the oscilloscope, one is straight, one is curved...
So why use DC power for IT products and most household appliances?
In the field of household appliances, DC products are used internally in IT products (such as mobile phones, computers) and most home appliances. Because notebooks and mobile phones are demanding, the rectifiers are placed outside, while desktop computers, refrigerators, and air conditioners put the rectifier inside the appliance.
Back to the essence, the direct current continuously flows from the positive pole to the negative pole, and the alternating current is fluctuating. The electronic components work by recognizing high and low potentials. For example, a computer has a potential of 1, and no potential is 0. The alternating current itself has a potential of zero crossing, so that electronic components cannot perform correct logic judgment. Therefore, household appliances must use direct current.
In fact, the application of direct current is also very extensive. For example: battery, DC engine, various electronic instruments, electrolysis, electroplating, DC power drag and so on.