Type 991 cable layer is a family of Chinese cable layers first saw service in Chinese navy, and later on, additional units also entered service with Chinese civilian authorities. Type 991I Type 991 I is the first member of Type 991 series, and it is the first purposely designed cable layer / repair ship in China. Program begun in early 1961 when Chinese naval headquarter formally issued the order to the 708th Institute of China State Shipbuilding Corporation, and the 708th Institute is also more commonly known as China Shipbuilding and Oceanic Engineering Design Academy (中国船舶及海洋工程设计研究 ) nowadays. After extensive research, the 3rd Directorate of the 708th Institute (708所3室) begun design work in October 1963, but reviews revealed that there are some inadequacy in the design, so two new modified design was created in February 1964. The biggest change of the modified designs is that the original cable carrying capacity is limited to 155 tons in a single cargo hold compartment with cable length of 40 km at maximum. In the modified design, this is increased to 270 tons in two cargo hold compartments with cable length of 40 km at maximum. The diameter of the cable remained unchanged at 40 mm. On August 2, 1965, the 6th Ministry approved the design of Type 991. In March 1966, some final modification begun at Wuchang Shipyard, where the ship was planned to be built, and this final modification was completed in June 1966. However, Wuchang Shipyard did not built the ship, but instead, the ship was built in Guangzhou Shipyard, with work begun in 1967 and launched on June 7, 1969. On January 1, 1971, trials were successfully completed and the ship entered service in Chinese South Sea Fleet with pennant number B230. Type 991I is equipped with10 ton (98.1 KN) EKM-20 cable laying machine that is indigenously designed in China. Specification: Overall length (m): 54.6 Length between perpendiculars (m): 48 Waterline (m): 50 Beam (m): 9 Depth (m): 4.4 Standard draft (m): 2.6 Full load draft (m): 3.06 Standard displacement (t): 691 Full load displacement (t): 850 Speed (k): 12 Engine: 2 x 294 kW (400 hp) Crew: 56 Cable payload: 270 t of 40 mm cable, 70 km long Type 991II After Type 991I cable layer entered service, Chinese navy recommended upgrading the ship based on the experience gained from deployment, but in order to reach the new requirement,