FACOM138A System

The FACOM138A was a practical automatic relay computer developed and manufactured by Fuji Tsushinki Seizo (now, Fujitsu). The FACOM128A was Fujitsu's first relay-based commercial computer developed in 1956 and the FACOM138A was a lower-cost model of the FACOM128A. To realize lower cost, arithmetic circuits were shared among addition, subtraction, multiplication, division and extraction of square root and memory unit was changed from crossbar-type to No.115 relay-type for downsizing. The FACOM138A registered here (see photo) was manufactured in 1960 and still in use today. The FACOM138A performs calculations using approximately 3,000 relays and has five functional units, computing unit, control unit, memory unit, input unit, and output unit same as current computers. In addition, FACOM138A equipped self-check and recovery functions, when the relays malfunctioned, stop and retry were automatically achieved to ensure high reliability as a commercial computer. Those functions are commonplace today, were cutting edge technology at that time. As a highly reliable and practical computer, the FACOM138A was widely applied to perform scientific calculations in manufacturing industry, including the design of camera lenses and automobiles.