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Royal Digital I-K Desktop Calculator

Royal Digital I-K

The Royal Digital I-K is an augment to Royal Typewriter Company's first electronic calculator, the Royal Digital I. The Digital I and Digital I-K calculators were manufactured by TEAL (Tokyo Electronic Application Laboratory) in Japan under contract to Royal Typewriter Company. Royal Typewriter Co. never manufactured its own electronic calculators, instead marketing machines designed and constructed by other manufacturers throguh OEM agreements with those manufacturers, most of which were in Japan.

Both the Royal Digital I and Royal Digital I-K are visually and functionally identical with the exception of three extra keys on the Digital I-K that provide additional functions that do not exist on the Digital I.

There are likely two different versions but functionally and visually identical versions of this calculator. One version will have nomenclature to the right above the display panel reading "ROYAL DIGITAL I-K" (as pictured here), and the other reading only "DIGITAL I-K". The ROYAL DIGITAL I-K uses small and medium-scale Japanese-made MOS IC logic. The DIGITAL I-K version uses a combination of two Large Scale MOS integrated circuts, along with a much smaller number of small-scale MOS ICs. Both machines look and function identically, with the DIGITAL I-K version being a revision to the design to reduce cost through the use of Large Scale (LSI) integrated circuits. The use of the term "Digital I-K" in this text refers to either version of the calculator.

The Digital I-K adds to the functionality of the Digital I with a constant function, percentage function, and a change-sign key. The constant function, activated by the push-on/push-off [K] key, operates for multiplication and division. The percentage function ([%] key) simply shifts the decimal two digits to the left in the second number entered in multiplication and division operations, e.g., 10 ends up being 0.10. The change sign key [θ] toggles the sign of the number currently being entered. It appears that the logic inside the Digital I-K is very similar to that of the Digital I, with some modifications/additions to provide the logic for the extra features. Operationally, the Digital I-K is identical to the Digital I as far as the normal four math functions go.

Royal Digital I-K Specifications

Manufacturer: Tokyo Electronic Applications Laboratory (Tokyo, Japan)
Marketer: Royal Typewriter Co., a division of Litton Industries
Model Number: Digital I-K
Manufactured In: Tokyo, Japan
Display Technology: Futaba DG-12C, Ten-segment Vacuum-Fluorescent Tubes
Right-hand decimal point and upper-left tick symbol
Power Requirement: 115VAC, 50/60Hz
Logic Technology: Two Versions
ROYAL DIGITAL I-K: Small and Medium-Scale MOS Integrated Circuits
DIGITAL I-K: Two LSI MOS chips with a few small-Scale MOS Integrated Circuits
Digits of Capacity: 10
Decimal Modes: Fixed at 0, 2, 3 and 4 digits behind decimal
Math Functions: Four function plus Percent [%]
Memories: None
Constant: Yes. Multiply and Divide via [K] Key
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