The network cable is essential to connect to the local area network. The common network cables in local area networks are mainly twisted-pair cables. Twisted-pair cables are data transmission lines composed of many pairs of wires. Its characteristic is that it is cheap, so it is widely used, such as our common telephone lines. It is used to connect with RJ45 crystal head. It has two kinds of STP and UTP, the one we commonly use is UTP.