Telephone and internet have penetrated into the lives of thousands of households. The internet has brought us closer to each other, while telephone has promoted people's communication. The telephone cannot be separated from the telephone line, and the network cannot be separated from the network line. Most telephone lines appear as parallel lines, with two cores.

The telephone line passes through ADSL, converts the information in the computer into analog line number, and then transmits it to another telecommunication terminal through the telephone line, and then converts the analog signal into digital signal. The telephone line frequency is not high, and it is usually used for analog signal related work.