High-density polyethylene or polypropylene, indicating the color of the insulating wire according to the national standard chromatography; Twist the single insulation into pairs according to different pitches, and use the specified chromatogram combination to identify the wire pairs to reduce the mutual interference and crosstalk between the wires, and the power loss is small.

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.