In 1960, the CM-1 (using approx. 41,000 parametrons) was developed at Nippon Telegraph and Telephone Public Corporation as a commercial telephone charge calculation system using parametrons. The incentive was that, at the time, telephone exchanges were being continually installed to resolve telephone network congestion, and it was impossible to keep up with billing work using the previous method of manually calculating charges. Another motive was the need to adopt centralized automatic message accounting (CAMA) in order to quickly achieve nationwide automation of telephone exchanges.
However, the processing capacity was still insufficient so NTT developed the CM-100, a transistor-based computer for general billing and one of the first machines to use the multi-job parallel processing system. After finishing research and development on the CM-100 and DEX-1, NTT began research (around 1966) on DEX for telephone exchange tasks and DIPS for information processing.