backup for the wireline network, and as the principal means for handling international telephone and telegraph communications. Multiconductor cable is used primarily for municipal telecommunications. Coaxial cable has only recently been deployed for use in longdistance telecommunications. A wideband microwave radio relay network is also in service and is being used for national television and facsimile transmission. Open Wirelines The Chinese have made substantial progress in expanding both the traffic-handling capability and the geographic coverage of the open wireline network. The network boasted more than 4 million kilometers of long-distance wire telephone lines at the end of 1974, an increase of 40 percent over 1965 and 15 times the length of the system in 1949. Main trunk routes are equipped with carrier multiplex capable of providing 12 two-way voice channels on one wire pair. Many secondary routes are equipped with a three-channel and one-channel voice carrier system. In addition, subchannel multiplexing techniques and equipment are in use on most lines to obtain from 4 to 16 telegraph circuits on one voice-grade channel. The long-distance open wireline network in China is based on the "four-level converging radial system." The four levels are the interprovince central, the intra-province central, the interhsien central, and the intrahsien central. The interprovince central bureaus are located at most provincial capitals and major municipalities and are linked to Peking and to one another by the main wireline trunk routes. Major industrial centers, important harbors, and national defense centers are also key subscribers to the trunkline network and enjoy direct telecommunications service. Production and installation of open-wire telephone lines continue to be given a high priority in China. More than 60 wire and cable production facilities exist, the largest in Harbin and Shanghai. Facilities at these two locations manufacture copper and aluminum telephone wire and multiconductor and coaxial cable. Together, they reportedly produce as much as 10,000 metric tons of rough-drawn wire a month. Steel and iron wire are produced in large quantities throughout China and are generally used at the local level in rural telephone and wire broadcasting networks. Multiconductor Cable Multiconductor cable is widely used in China's municipal telecommunications as feeder lines and, to a lesser extent, in long-distance telephone communications. Star-quad and loaded multiconductor cable links have been installed between Peking and a few provincial capitals, but high-frequency cross-talk has limited their usefulness as a suitable telecommunications medium for long-haul circuits. Most of China's multiconductor cable is produced at the Harbin and Shanghai electric cable plants. Coaxial Cable Until recently, coaxial telecommunications cables were not widely used in China. A 1962 reference indicates that the Shanghai Cable Plant trial produced a coaxial cable capable of providing one tele vision channel and 3,600 telephone channels. A Soviet prototype may have been used, possibly a four-tube coaxial cable similar to that manufactured in the U.S.S.R. Since 1969, the Chinese press has made frequent references to underground cable projects. For example, in July 1973, a PLA unit was reported to have advanced its schedule for laying an underground cable in order not to hamper agriculture production. Similar reports in October 1973 suggested that the laying of multichannel coaxial cable was national in scope. Submarine Cable China has traditionally used domestically produced low-capacity submarine cable to connect the mainland with many of the islands located along the coast. Recently, the Chinese have turned to Japan for high-capacity 120-channel coaxial submarine cable for installation between Tientsin and Luta in the Po-hai Gulf. The purchase is apparently part of an overall plan to link major cities by underwater cable placed along the coastline and in riverbeds. China has contracted with a Japanese shipbuilder to construct a cable-laying vessel capable of handling coaxial submarine cable. Point-to-Point Radio The inadequacy of the wireline network in remote areas has led to the use of point-to-point radio networks for the transmission of telephone and telegraph traffic. Furthermore, when communications over the wireline network are disrupted, point-to-point radio circuits may provide the only telecommunications service available. Microwave Radio Relay Low-capacity (12- and 24-channel) microwave radio relay systems manufactured in Eastern Europe and the Soviet Union have been used in internal telecommunications since the late 1950's. Wideband radio relay transmission systems are currently being deployed, as part of the Fourth Five-Year Plan. The plan calls for establishing a nationwide television network to link Peking with most provincial capitals. This microwave radio relay network will eventually evolve into China's major telecommunications trunk system. Until this wideband radio relay system can be equipped with appropriate carrier multiplexing equipment, its primary use will be for television transmission. Construction of the high-capacity microwave radio relay system has proceeded at a rapid pace. In December 1971, the Chinese reported that the October 1, 1970 National Day celebration was telecast and relayed from Peking to 15 other provinces and autonomous regions. have reported receiving live television transmissions from Peking. The microwave radio relay network probably covers more than 13,000 kilometers. Signals are transmitted through more than 260 microwave repeater and terminal stations, assuming that the stations are spaced at a standard distance of 50 kilometers. The microwave radio relay system probably provides the Chinese with a potential capacity of 600 to 960 channels of telephone traffic per active radio frequency (RF) trunk channel. Because as many as five RF trunk channels per route are common, such a microwave system potentially can carry close to 5,000 telephone channels. Any of the trunk channels can serve alternatively to carry television. Telecommunications Media in Prospect Although construction of a new wideband high-capacity system is far from complete, China probably will advance into other areas of modern telecommunications technology. Tropospheric scatter research has apparently been under way since 1964. An article in a Chinese journal in 1964 reflected knowledge of tropospheric scatter theory equivalent to the U.S. state of the art at that time. The Chinese also have shown an interest in low-capacity pulse code modulation (PCM). Because China is in an early stage of deploying a wideband communications system, 24-channel PCM equipment would reduce the cost of installing short-haul toll circuits or in adding local junction cable or conduits in large cities. A domestic satellite communications network also can be expected. The Chinese have been actively seeking test instrumentation used in ground station operations. A Chinese scientist who visited the United States in 1973 indicated that research was being conducted on a communications satellite. Laser and millimeter wave-guide research is under way in China and could have applications suitable for telecommunications transmission. Carrier Multiplex Equipment As with most countries, the Chinese have standardized 12-channel and 3-channel carrier multiplex systems on open wirelines. If used in combination, these systems will provide a total of 16 voice channels including baseband-on one wire pair. The most often referenced telephone multiplex equipment for open wirelines is the ZB 312 series. ZB 312-IV-type 12-channel group carrier equipment was first produced in 1964 at the Shanghai Posts and Telecommunications Equipment Plant. A ZB-316-type telegraph multiplexer was also manufactured at the same facility and is used to obtain 16 telegraph channels on a single voice-grade circuit. Transistorized versions of this equipment are now being manufactured in China. Despite the progress the Chinese have made in developing wideband transmission, the systems cannot operate at designed capacity unless adequate multiplexing equipment is available. Except for a limited amount of time division multiplexing equipment, most carrierequipped telephone channels in China employ the technique of frequency division multiplexing (FDM). In 1958, a 24-channel carrier FDM system was reportedly trial produced at the Peking Telecommunications Scientific Research Institute. The following year, the Chinese announced the trial manufacture of a 60-channel FDM carrier system. Serial production of 60-channel FDM supergroup equipment was apparently not begun until 1971. Telephone Switching Telephone switching in China is accomplished through a network of regional branch offices located at various administrative levels. At 51-174 - 75 - 20 present, there are about 3,000 local and toll telephone exchange offices in the cities. Lower level telephone exchanges offices are estimated to number at least 40,000. There are about 5 million automatic lines in China, including poorquality private automatic exchange lines. The majority of these lines are used in antiquated step-by-step exchanges, with only a small percentage of common-control crossbar switching equipment. Obsolete Soviet and East European technology is used in Chinesemanufactured exchanges, most of which have a capacity of about 200 to 900 lines. In addition, China operates a large number of magnetotype manual exchanges in small cities and rural areas. Modern telephone switching equipment is essential for efficient utilization of China's newly acquired high-capacity telecommunications transmission networks. China also is faced with a growing demand for external telephone communications because of rapid expansion of foreign economic and diplomatic activities. In addition, growing requirements for communcations by the armed forces are in competition with civil requirements for use of local and toll switching facilities. In order to develop its growing subscriber communications, China must revamp much of the available switching capacity. The government recognizes the limitations of its telephone switching system and, since 1971, has sponsored the study of technology available in the non-Communist world. A thorough evaluation is called for because the type of switching equipment used dictates what other equipment can subsequently be added to the system. Chinese interest in Western equipment and manufacturing facilities covers a variety of electromechanical and electronic exchanges. The Chinese apparently have not decided whether to go with crossbar or opt for the more sophisticated electronic switching equipment. On the basis of previous practice, the Chinese will probably import enough switching equipment to meet most current needs and will satisfy future requirements by importing a complete manufacturing facility. V. TELECOMMUNICATION MODES AND SERVICES Telephone and telegraph communications, including manual Morse, automatic Morse, teleprinter, and facsimile are China's principal modes of telecommunication. Telecommunications service ranges from poor to good. Local service is generally poor. Long-distance service is rapidly improving with the recent addition of modern transmission systems. Further improvement is expected with the installation of advanced switching equipment. In almost all provinces and municipalities, an effort is now underway to expand available telephone and telegraph service. Telephone Local and interurban telephone service is the major telecomunications service available in China. The system, with approximately 1 million telephone outlets, ranks low compared with the systems in other large LDC's. Nonetheless, the system meets the basic needs of the state, industry, and the armed forces. Even the minimal needs of agriculture are now being met because of the quadrupling of rural telephone outlets in the last decade. More than 98 percent of the nation's communes now have telephone service. Approximately 80 percent of the nation's cities are now equipped with automatic dial systems. The telephone numbering system reflects an expansion of urban services. Shanghai converted from a 5to a 6-digit number system in 1957; Peking in 1965. The capital now has about 170,000 telephones. Eleven other major cities use a 5-digit numbering system, and a 4-digit system. Direct dialing service started in October 1969 between Peking and Tientsin. This is the only known long-distance dialing service available in China. Telephones are installed on a priority basis according to the needs of Party, military, government, industrial, and commune officials. Some hotel rooms in large cities have telephones that can be connected into the local telephone system. An increasing number of public pay telephone booths are being installed in the larger cities-in public parks, post offices, and shops, and on the main streets. Only highranking officials have phones in their private residences. A common feature of the telephone service in China is the telephone conference call. The extensive bureaucratic organization of Chinese society requires a multitude of meetings to exchange information, pass on instructions, spur lagging production, and coordinate papers. Because China has few resources to spare, telephone conferences are used in preference to time-consuming and costly gatherings. Telegraph The telegraph system has played second fiddle to the telephone system. The wireline and point-to-point radio networks have provided only a small capacity, made even smaller by the use of Morse transmissions over most of the circuits. In addition, telegraph operation is hampered by the complex nature of the written Chinese language. To overcome this problem, the Chinese have adopted a numerical 4-digit code, a time-consuming procedure involving both manual encoding and decoding of the transmitted message. With the exception of some recently imported West German teleprinters, most of the telegraph transmission equipment in China is obsolete. The most widely used teletype machines are the model 68, the model 51, and the model 55. The model 68, a tape-perforating teletype unit manufactured by Siemens of West Germany, was initially imported in 1957. The model 51 was first imported from East Germany in 1955. The model 55 is manufactured in China and is an adaption of various types of foreign equipment. A major breakthrough in China's telegraph service was achieved in 1969 with the trial production of an electrostatic telegraph printer. The printer is equipped with a memory storage device and is able to automatically convert a punched tape of 4-digit telegraphic code directly into Chinese character text. The machine operates at a speed of 1,500 characters a minute, 75 times the speed of manual decoding. In addition, the Chinese announced in November 1974 the production of their first electronic telegraph relaying machine. Facsimile The introduction of facsimile telegraph service is another attempt by China to overcome the language problem in telegraph transmission. Facsimile equipment allows the direct transmission of character text, |