JNR long-distance transmission lines had comprised of SHF radio and co-axial-cable carrier transmission systems for a comparatively long time. Since their introduction, there had been remarkable progress in fiber-optic technology, which has the advantages of large transmission capacity, low transmission loss and no electromagnetic interference. Fiber-optic cables were laid for about 800 km by 1983, a figure that has since been increasing sharply.
When JNR was privatized in 1987, its long-distance transmission systems were transferred to Railway Telecommunication Co., nationwide information systems such as MARS, EPOCS and DACS to Railway Information System Co., and other local facilities to JR companies, respectively.
