The rapid progress of computer technology prompted the introduction of stored-program electronic exchange (analog SMM switch) in 1979. Furthermore, stored-program digital exchange was introduced in 1985, enabling direct connection to fiber-optic cables and realizing the general digital network in the future.
Table 1 shows different exchange systems.
Table 1 Exchange systems
The first train radio was employed on the commuter's express on the Tokaido line in 1960, followed by the Shinkansen, and gradually introduced to existing lines. Train protection radios, already adopted on Shinkansen lines, were brought in for the roughly 7,000 km of main lines in 1986. Train radios were installed for about 12,000 km by the same time.
The data-exchange system (DACS) was completed in 1974, and was improved to a digital-transmission network which could serve as a VAN (Value Added Network) in 1986.
A seat-reservation system (MARS-l) was developed in 1960 as the first on-line-real-time system in Japan. After several improvements to cope with increasing demand, the present system (MARS-301), which can handle all types of tickets and is connected with travel-companies' terminals to promote merchandising, was completed in 1986.
As for transmission lines, open-wire lines and lead-covered cables were replaced by plastic cables with the progress of the petrochemical industry in the 1950s. Cable-carrier transmission technology also developed, particularly in the case of co-axial cables.
In order to cope with increasing demand, SHF (7.5 GHz, 960 ch) radio networks were opened as a means of long-distance transmission between Tokyo and Osaka in 1959 and spread nationwide.
