A coaxial cable consists of a hollow cylindrical conductor and an inner conductor on the central axis, and the inner conductor is insulated from the cylindrical conductor, the cylindrical conductor and the outside. Its characteristics are good anti-interference ability, stable data transmission and low price. It is also widely used, such as closed-circuit television line and so on.

Coaxial cable can be divided into two basic types, baseband coaxial cable and broadband coaxial cable. At present, the baseband is a common cable, its shield line is made of copper mesh, the characteristic impedance is 50 (for example, RG-8, RG-58, etc.); the shielding layer of the cable commonly used for broadband coaxial cable is usually stamped with aluminum, and the characteristic impedance is 75 (for example, RG-59, etc.).

Coaxial cable can be divided into coarse coaxial cable and thin coaxial cable according to its diameter. Coarse coaxial cable is suitable for large local network. Its standard distance is long and its reliability is high. Because it does not need to cut the cable in installation, it can adjust the position of the computer flexibly according to the need, but the cable network must install the transceiver cable, so the installation is difficult, so the overall cost is high. On the contrary, the cable installation is relatively simple, and the cost is low, but because of the installation process to cut off the cable, two heads must be installed on the basic network connection head (BNC), and then connected to the two ends of the T connector, so it is easy to produce a bad hidden danger when the joint is many times, which is one of the most common faults in the current running Ethernet network.

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