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一、数字通信网的建立1969年,日本专用线已建成2400比特的系统,不久又将建立4800比特和48千比特的专用线。那时日本国内对高速数据传输的要求还不多。50比特专用线占总数的70%,1200比特的专用线仅占6—8%。1965年底统计市外电路线路数目为50万条线路,而总数据传输线路的数目只不过4000条线路,还不到1%。但近年来数据传输线路增加很快,一年时间就增加50%,预计五年期间就可增加10倍。对于数据传送的速度年年都有
First, the establishment of digital communications network In 1969, Japan dedicated lines have been built 2400-bit system, and soon will be the establishment of 4800-bit and 48-kilobit dedicated lines. At that time, there was not much demand for high-speed data transmission in Japan. 50-bit dedicated lines accounted for 70% of the total, 1200-bit dedicated lines only accounted for 6-8%. By the end of 1965, the number of external circuit lines counted was 500,000 lines, while the total number of data transmission lines was only 4,000 lines, less than 1%. However, the number of data transmission lines has increased rapidly in recent years by 50% in one year and is expected to increase by 10 times in five years. For data transfer speed every year