Communication cables are cables that carry telephones, telegrams, fax documents, television and radio programs, data, and other electrical signals. It is made by twisting a pair of mutually insulated wires. The communication cable has the advantages of large communication capacity, high transmission stability, good confidentiality, less influenced by natural conditions and external interference compared with the overhead open line.
Communication cables can be divided into six series of products, namely, domestic communication cables (including paper-insulated local cables, polyolefin-insulated polyolefin sheathed local telephone cables), long-distance symmetrical cables (including paper Insulated high- and low-frequency long-distance symmetric cable, copper-core foam polyethylene high- and low-frequency long-distance symmetric cable and digital transmission long-distance symmetry cable), coaxial cable (including small coaxial cable, medium coaxial and small coaxial cable), submarine cable (separable Symmetrical submarine and coaxial submarine cables), fiber optic cables (including conventional cable, ribbon array, and skeleton types), and RF cables (including symmetric and coaxial RF).
According to the type of cable, the communication cable is classified as follows:
1, single wire: refers to the most primitive communications cable, single-wire loop, with the earth as a regression line.
2. Symmetrical cable: It consists of two wires that are identical under ideal conditions.
3. Coaxial cable: The two conductors inside and outside on the same axis will form a loop. The outer conductor surrounds the inner conductor and both are insulated.
According to the application, communication cables can be divided into the following three categories:
1. Long-distance cables: long transmission distances are generally used for multiplexing, and most of them are directly buried underground. In rare cases, they are installed by overhead installation or installed in pipelines.
2. Cables in the city: The wires in the cables are “double pairs” and they are many. Generally installed in the pipeline, a small amount of local cable is attached to the building or installed overhead.
3. Local cable: mainly refers to the communication cable used in the telecommunication bureau, generally installed in the distribution frame, and some are installed in the cable duct; the office cable is used between the transmission equipment and the exchange equipment in the telecommunication office, and other Inside the office equipment. In order to prevent fire in the telecommunications bureau, it is sometimes necessary to add fire-retardant jackets to the office cables.
According to the above classification method, the communication cable may be asymmetrical cable or a coaxial cable.