Since 1970, Shanghai Cable Factory used a new steam-cross-linked polyethylene material to trial-produce cross-linked cables. In November 1971, Shanghai First Bureau Mechanical and Electrical Engineering issued the third batch of mechanical and electrical products needed for the "123 Mine", and Shanghai Cable Factory undertook the production task of cross-linked cables. After repeated experiments, it finally succeeded on August 2, 1972. The first cross-linked cable in China in the 1970s replaced the oil-impregnated paper-insulated cable processing technology. Its performance is better than that of oil-impregnated paper-insulated cables. At the same time, its laying conditions are not restricted by the vertical drop. It is a special project and ground. Since then, cross-linked cables have been widely used in power transmission in most cities in East China.

On March 13, 1845, Britain successfully laid the world's first submarine cable in the English Channel, as the immature technology and no armor protection, it was damaged by external forces the next day. Then the British Cable Research Institute started to develop and strengthen cables, and added steel wire armor to the outside of the cables according to the depth of the seabed to reduce the possibility of external damage in the deep sea. After several years of experimental research, it was finally put into production in 1851. On November 28,1851, the world's first armored submarine cable was successfully laid, which not only increased the strength of the cable, but also increased the service life of the cable. At the same time, a new chapter in international telegraph communications was opened.

On July 3, 1855, William Thomson, a famous British physicist, published the submarine cable signal attenuation theory, which solved the attenuation problem of cable terminal signal when laying the first Atlantic submarine cable. After nearly three years of practice, late at night on July 26, 1858, two cable-laying ships met in the middle of the Atlantic Ocean. After assembled, the cable-laying ships lays the cables in the opposite direction. On August 5, a total length of 3240 kilometers of cable was completed. At 2:45 a.m, the first marine cable traversed the Atlantic Ocean. The submarine cable telegram was broadcast between the United States and the United Kingdom on August 12, but it did not last long. At 1 a.m on September 3, the cable insulation was damaged due to the operator's operation error.

After inventing the telephone in his laboratory on June 2, 1875, Bell successfully conducted the first long-distance telephone experiment between Boston and New York (300 kilometers apart) in 1878. After that, the telephone soon became popular in major cities in North America. Since then, telephones have come into homes like running water and gas, people can talk without going out. In 1880, Bell conducted the first experiment of "optical telephone" with the sun as the light source, and helped the New York Cable Institute successfully lay the first telephone cable on September 7 of that year, making the telephone cable as a medium for long-distance communication.

Since 1880, Danish, Russian, British and other imperialists had invaded and occupied China's telecommunications sovereignty in an attempt to control its important telecommunications industry after the war of aggression against China. At the same time, they entered the domestic wire and cable industry, tried to destroy the development of domestic national industry. In the face of the national crisis, some wire and cable companies may not negotiate with foreign companies by handing over the operation authority. This action aroused the caution of many patriots at that time. After the success of the Fujian-Taiwan submarine cable, the first submarine cable independently built by Zhongnuo on February 3, 1887. The establishment of Taiwan Telegraph Office was put forward by Ding Richang , the government officials of Fujian province, and draw up the construction of telegraph lines, then he sent the telegraph school students Su Ruzhuo and Chen Pingguo focus on it. The construction of an open wire telegraph line between Gaoxiong (formerly known as Qihou) and Tainan (formerly known as Fucheng), with a total length of 95 huali, started in August 1887 and was completed on October 11 of the same year, which is the first telecommunications line built and managed by ourselves.

From 1871, the business of Denmark's Great North Telegraph company was limited to enter Shanghai, then the Danish Telegraph Office was set up in Shanghai in an attempt to monopolize China's telegraph industry. At that time, China's electric wire and cable industry was in a backward stage of development due to the cholera of the war and the qing government's absurd idea of building the country behind closed doors. In the face of the immigration of outsiders, some people of insight gradually realized that the industry crisis facing the country. On February 3, 1887, under the leadership of the Governor of Taiwan, Liu Mingchuan, the government spent a lot of money to lay a 433 mile telegraph cable between Fuzhou and Taiwan. It connected Taiwan to the mainland and played an important role in Taiwan's development for a long time. It was also the first submarine cable built by China independently.