The digital cable is developed from the local telephone cable. Commonly known as “data cable” and “network cable”. Some experts propose producing cables with a maximum transmission frequency of 1000 MHz (1GHZ). There is no conclusion yet, but many units are producing high-speed digital lines, and the transmission frequency must reach more than 21804GHZ. The cable core is composed of a plurality of mutually insulated wires or conductors, and the communication line is provided with a sealing sheath on the outside. Some are also equipped with an outer sheath outside the sheath.There are various laying methods such as overhead, direct burial, pipeline and underwater. According to the structure, it is divided into symmetrical, coaxial and integrated cables; according to functions, it is divided into the field and permanent cables (underground and submarine cables).The communication cable has a wider transmission frequency band, a larger communication capacity, and less external interference, but it is not easy to repair. It can transmit telephone calls, telegrams, data and images, etc. As an important branch product of digital cable products, water-blocking digital cable is mainly used outdoors. It can prevent water vapour and moisture from entering the cable in wet seasons and ensure good transmission performance.