The car telephone service was introduced in the 23 districts of Tokyo in December 1979 (Showa 54). Five years later, in 1984 (Showa 59), the system became available throughout the country. Coin operated car telephones were also introduced to allow convenient calling from inside buses or taxis. The car telephone system provided by NTT used the "small zone" system. This system uses radio base stations with a coverage extending to a radius of only 5 - 10km. This allows other radio zones to use the same frequencies.

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