Royal I.C.-90 (a.k.a. Digital IV)
&
Imperial I.C.-90
In late-1971/early-1972 Litton Industries, the parent company of Imperial and Royal, started to market two versions of a unique design of hand-held calculator that uses a stylus for input rather than a normal keypad. These models are the Royal Digital III (link to the parent Vintage Calculators site) and the Royal Digital IV, shown below. The Royal Digital IV sold in Britain is additionally labelled I.C.-90 and was also available under the Imperial label.
This model does not have keyboard buttons, but uses an electrical stylus which is touched on the gold-plated pads on the circuit board (above) to enter the numbers and operators.
Royal I.C.-90 (a.k.a. Digital IV)
Display is 8 digits, red LED.
4-function.
Main integrated circuit - General Instruments GI 251 (here date coded early 1972).
7.2 v (6 x AA rechargeable cells).
81 mm x 165 mm x 39 mm (3.2" x 6.5" x 1.6").
Introduced January 1972.
Labelled:
I.C.-90
IMPERIAL TYPEWRITER CO. LTD.
LEICESTER, ENGLAND
MADE IN U.S.A.
In the U.S.A. this model is labelled 'ROYAL DIGITAL IV'.
From the magazine 'Electronics', in January 1972[1]:
"Royal Consumer Products division, Hartford, Conn., a part of Litton Industries. With its Digital
III and IV, made by the Monroe division of Litton, Royal is in a position to market these units to consumer outlets, from mass merchandisers to the corner stationery shop. With quantity discounts and prompt payment, dealers get
these machines for under $90. Suggested retail prices are $139 and $149."
Price in UK, in June 1972, complete with carrying case and charging unit GBP £52-50[2].
At this time calculator keyboards were complicated and expensive components. To cut the cost this calculator shows gold-plated pads on the circuit board through the front of the calculator. Touching a pad with the electrically connected stylus has the same effect as pressing a key on a standard calculator.
Only this model, the Imperial I.C.-90 version below, and the Royal Digitial III are known to have this stylus feature.
Imperial I.C.-90
This model is identical to the Royal I.C.-90 (a.k.a. Digital IV) at the top except for the colour of the casing and the label on the front.
Display is 8 digits, red LED.
4-function.
Main integrated circuit - General Instruments GI 251 (here date coded early 1972).
7.2 v (6 x AA rechargeable cells).
81 mm x 165 mm x 39 mm (3.2" x 6.5" x 1.6").
Labelled:
I.C.-90
IMPERIAL TYPEWRITER CO. LTD.
LEICESTER, ENGLAND
MADE IN U.S.A.
References:
Imperial models
Vintage British Calculators
Text & photographs copyright, except where stated otherwise, © Nigel Tout 2000-2024.