Electro-Mechanical Calculator FACOM128B

The FACOM128B is a relay computer developed in 1958 by Fuji Communication Equipment Manufacturing Company (now Fujitsu Ltd.). In this relay computer, calculations are performed by mechanically opening and closing electrical circuits using relays, and results are stored using a crossbar mechanism based on the company's telephone exchange systems, with no electronic circuitry involved. Each digit comprises two sets of units representing 0 or 5 and five sets of units representing 0 to 4, and calculations are performed in the decimal system. This mechanism differs fundamentally from that of current electronic calculators, which perform binary arithmetic operations. This model was used in the design of camera lenses and the wings of the domestically produced YS-11 passenger aircraft. This machine was manufactured in 1959, and after being utilized for research at the Nihon University's College of Science and Technology, it is now preserved in the working order at the Fujitsu Numazu Plant and used for in-house training.
The history of calculators began with manual mechanical systems, which progressed to electrically powered systems and then to mechanoelectric systems that mechanically control the potential of circuits, followed by the disappearance of the mechanical components and a major shift to the electronic conversion of circuits. This computer, with its electrically assisted mechanical mechanism, is a testament to mechanical computers using a decimal calculation system during the transition from mechanical to electronic systems.