Coaxial cable refers to the cable with two concentric conductors, in which the conductor and shielding layer share the same axis. The most common coaxial cable consists of copper conductors separated by insulating layers. The inner insulating layer is followed by a ring conductor, and the outer layer has another insulating layer. The whole cable is wrapped by PVC or PVC sheath. Teflon material.
1、 Classification of coaxial cables:
Coaxial cable can be divided into two basic types: baseband coaxial cable and broadband coaxial cable. At present, baseband is a commonly used cable. Its shielded wire is made of copper mesh, and its characteristic impedance is 50 (RG-8, RG-58, etc.); The shielded broadband coaxial cable is usually made of aluminum and has a characteristic impedance marked as 75 (such as RG-59).
Coaxial cables can be divided into thick coaxial cables and thin coaxial cables according to their diameters. The thick wire is suitable for a large LAN. The standard distance is long and reliable. The wire does not need to be cut during installation. The computer can be flexibly connected to the network according to needs and can be adjusted. The thick wire network needs to be installed with transceiver lines, which is difficult to install and increases the overall cost. In contrast, installing thin cables is relatively easy and inexpensive, but requires cutting the cable and connecting the basic network connector (BNC) at both ends during installation, and then connecting to both ends. Therefore, the more connectors there are, the easier it is to have undesirable defects and hidden dangers, which is one of the most common faults in Ethernet operation today.
Both thick cables and thin cables are bus topologies in which multiple machines are connected to one cable. This topology is suitable for machine intensive environments.