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Twisted pair: Twisted pair is divided into shielded (Shielded Twisted pair, referred to as STP) and unshielded (Unshielded Twisted pair, referred to as UTP). The so-called shielding means that the signal wire inside the network cable is wrapped with a layer of metal mesh, and the shielding layer is the insulating sheath, which can effectively isolate the interference of external electromagnetic signals.

UTP is currently the most frequently used network cable in local area networks. This kind of network cable is wrapped in a plastic insulating sheath with 8 signal wires. Two of them are entangled with each other as a pair, forming a total of four pairs. The twisted pair is also named. The purpose of twisted pairs twisted with each other is to use the electromagnetic field generated by the current in the copper wire to cancel the interference of adjacent lines and reduce the interference from the outside world. The number of times that each pair of wires are twisted with each other in each inch of length determines the anti-interference ability and the quality of communication. The tighter the twist, the higher the communication quality and the higher the network data transmission rate. Of course, its cost is also higher. high.

Coaxial cable: Coaxial cable refers to a cable with two concentric conductors, and the conductor and the shielding layer share the same axis. Because it wraps the insulating material outside the main line, and there is a layer of woven shielded metal wire outside the insulating material, it can well block the external electromagnetic interference and improve the quality of communication. The advantage of coaxial cable is that it can support high-bandwidth communication on a relatively long line without repeater, but its disadvantages are also obvious: First, it is large in size, and the diameter of a thin cable is 3/8 inches thick, which takes up the cable. There is a lot of space in the pipeline; the second is that it cannot withstand tangles, pressures and severe bends, which will damage the cable structure and prevent signal transmission; and the third is the high cost. All these shortcomings can be overcome by twisted-pair cables. Therefore, in the current local area network environment, they have basically been replaced by Ethernet physical layer specifications based on twisted-pair cables. Coaxial cables are divided into thin cables and thick cables.