Browse Prior Art Database

The Sinclair Calculators Disclosure Number: IPCOM000129956D
Original Publication Date: 1996-Sep-30
Included in the Prior Art Database: 2005-Oct-07
Document File: 2 page(s) / 77K

Publishing Venue

Software Patent Institute

Related People

IEEE Computer Society: OWNER


The Sinclair Calculators

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Copyright ©; 1996 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Used with permission.

The Sinclair Calculators

The following material is drawn from a highly entertaining account of the rise and fall of the varied enterprises of Sir Clive Sinclair. Although our interest for this column is on the broad line of Sinclair calculators, Sinclair also developed transistor radios, hi-fis, computers, and flat- screen televisions.

The Sinclair Executive Calculator

Jim Westwood and Chris Curry developed a breadboard of a calculator using a Texas Instruments GLS 1802 four-function calculator chip. The breadboard was powered by three hearing-aid batteries, but the power consumption of the NMOS calculator chip and the light- emitting diode display was so high that battery life was too short. It was discovered that if the power was disconnected and reapplied "fairly quickly," data were retained in the memory. The circuit would hold a charge for about five seconds. David Park designed a circuit that pulsed the power under control of the clock. Originally the chip consumed about 350 milliwatts, but with pulsed power it consumed only 30 milliwatts.

The Sinclair Executive was housed in a sleek and small (5.5 inches by 2.25 inches by .38 inch,
2.5 ounces) black plastic case. It was introduced in September 1972. The functions provided are add, subtract, multiply, divide, square, and reciprocal. It displays eight digits with a choice of fixed or floating decimal point. It consists of a Texas Instruments GLS 1802 processor, 22 transistors, 50 resisters, and 17 capacitors. The cost of parts was close to 10, and the selling price was 80. A bit over a year later (November 1973), the Sinclair Executive Memory calculator was introduced. In appearance it was similar to the Sinclair Executive (it was packaged in the same slim case), but had memory so that it could save subtotals.

The Sinclair Cambridge Family of Calculators

In August 1973 the Sinclair Cambridge was introduced. Compared to the Sinclair Executive, a more conventional calculator case was used that measured 4.5 inches by 2 inches by .7 inch and weighed 3.5 ounces. It sold for 29.95 assembled or 24.95 in kit form.

The Sinclair Cambridge Scientific was introduced in March 1974. Designed by Nigel Searle, it used a new processor from Texas Instruments to perform the standard four functions and a suite of scientific functions, including logarithm, antilogarithm, sine, cosine, tangent, arcsine, arccosine, and arctangent. It used the same case...