DDX [Japanese digital switching network]
Masashi Kato, Toshiharu Takatsuki, Yutaka Yoshida · IEEE Communications Magazine · 1981
To meet Japan's diverse data communication needs, Nippon Telegraph & Telephone Public Corporation (NTT) has been researching and developing the digital switching network, DDX. The circuit-switching network was put into commercial service in Tokyo, Osaka, Nagoya, and Yokohoma on 25 December 1979.