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Uchida Yoko USAC 10B Desktop Calculator

Uchida Yoko USAC 10B (Model UC-10B1)
Image Courtesy of Mr. Takaharu Yoshida

The USAC 10B is the first of a series of four different desktop electronic calculators developed and marketed by Uchida Denshi Kogyo Co., Ltd. (later Uchida Yoko Co., Ltd.). Uchida Yoko is a large Japanese multi-faceted manufacturing and marketing company that has been involved in numerous businesses, including accounting & billing machines, small office small computers, office furniture, scientific equipment for educational institutions, mechanical adding machines, office supplies, and, for a short time, electronic calculators. After only slight over two years in the electronic calculator marketplace, Uchida Yoko shut down its electronic calculator division due to intense market competition that made it impractical for the company to remain competitive.

The USAC 10B was the result of early electronic calculating machine development at Unoke Denshi Kogyo, a firm that was acquired by Uchia Yoko in 1962. Unkoke Denshi Kogyo had developed some sophisticated electromechanical bookkeeping machines, and had acquired enough digital electronics skills to create an electronic accounting machine. Not long after the work on the electronic accounting machine was in its final stages, work began on developing a fully electronic desktop calculator. This work continued after the acquisition by Uchida Yoko, and resulted in a number of prototype calculators that never became products. Eventually, the USAC 10B (one wonders what the story might be of the USAC-10A?) came to be after Uchida Yoko negotiated a volume purchase agreement with Fairchild Semiconductor in the US to purchase the integrated circuits used to make the USAC 10B. At the time the USAC 10B was developed,

The USAC 10B calculator was first entry into the electronic calculator market, and was introduced in June of 1967. The USAC 10B is of a very unusual design, being as far as is known, one of only two electronic calculators ever made to exclusively use RTL (Resistor-Transistor Logic) small-scale Integrated Circuits. The ICs in the USAC 10B are made by the famous American semiconductor manufacturer Fairchild Semiconductor. The machine's logic is based entirely on approximately 350 of Fairchild's µLogic devices. Each µLogic IC (10-pin radial lead round plastic packages) contains a few logic gates or a single flip-flop. The Fairchild µLogic family of ICs were the first commercial family of general purpose digital integrated circuits. The other known commercially-offered electronic calculator using primarily Fairchild µLogic devices is the very rare American-made Dero Research & Development Sage 1 electronic calculator.

The USAC 10B was advertised as the world's first production all-IC desktop electronic calculator, a claim which is incorrect, as the Victor 3900 lays claim to this distinction, introduced nearly a full two years earlier. While not the first all-IC-based electronic calculator, the USAC 10B was the first to have its logic primarily implemented using small-scale integrated circuit devices. Sharp Corp. says it was first with it's Japan-only Sharp Compet CS-31A, which was introduced in October, 1966. While the CS-31A utilized Mitsibishi-made small-scale TTL integrated circuits to implement its memory register, the rest of the calculator was built using discrete transistor technology. The CS-31A may have been the first electronic calculator to use small-scale ICs, the USAC 10B was the first to implement its logic entirely with small-scale integrated circuits.

The 10B is a basic four-function office calculator, with a single accumulator-style memory register. Capacity is ten digits, with a Nixie tube display. It operates with keyboard panel pushbutton-selectable fixed decimal position. Follow-on calculators included the USAC 10R (added square root), the USAC 22B, and the USAC 22R. The Old Calculator Museum would like to acquire any of these models. If you have any information, documentation, or photos of any of Uchida Yoko's calculators, please contact the museum by clicking on the EMail button in the menubar at the top of this page.


Uchida Yoko USAC 10B Specifications

Manufacturer: Uchida Denshi Kogyo Co., Ltd. (Uchida Yoko)
Model Number: UC-10B1 (USAC 10B)
Manufactured In: Japan
Date of Introduction: June, 1967
Size: 13" wide, 16" deep, 8" high
Weight: 20 pounds
Power Requirements: 100V (Japanese Market), 90W, 50/60Hz
Price: ~$650 at introduction
Display Technology: Nixie Tube
Logic Technology: ~350 Fairchild µLogic small-scale RTL ICs
Digits of Capacity: 10
Decimal Modes: Fixed via pushbutton at 0, 3 and 5 digits behind decimal
Math Functions: Four Function
Memories: One accumulator-style memory register
Constant: Yes. Unclear if available for addition/subtraction
Features: [←] key for error correction
Performance: Addition/Subtraction: 1ms; Multiplication/Division: 20ms

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