As a second step towards a digital telecommunications network, the D-70 automatic exchange enabled local systems to be converted to digital operation. The world's first fully LSI-based subscriber circuit was developed in 1981 (Showa 56) and the system was made practical by adopting a time-division multi-channel system which provides an interface suitable for both digital and analog subscriber lines. The system first went into service at the Daido exchange in Nagoya in 1983 (Showa 58). From that time on, the system was introduced around the country as the standard local exchange.

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