Network cable, usually made of metal or glass, can be used to transmit information within the network. There are three commonly used network cables: twisted pair, coaxial cable and optical fiber cable (optical fiber). Twisted pair is a data transmission line composed of many pairs of wires. It is characterized by low price, so it is widely used. Twisted pair is used to connect with RJ45 crystal heads. There are STP and UTP, and UTP is commonly used.