Sinclair Executive

Sinclair Executive

Sinclair Executive Type 1
Introduced	September 1972
Invented by	Clive Sinclair
Cost	GB£79.95
Calculator
Display Type	Light-emitting diode
Display Size	8 digits
CPU
Processor	Texas Instruments GLS 1802[1]
Frequency	200 Khz
Programming
Other
Power supply	4 button cells
Power consumption	20 milliwatts
Dimensions	56 by 138 by 9 millimetres (2.20 × 5.43 × 0.35 in)

The Sinclair Executive was Clive Sinclair's first venture into the pocket calculator market, and the world's first "slimline" pocket calculator. Introduced in 1972, there were at least two different versions of the Sinclair Executive, with different keyboard markings, and another called the Sinclair Executive Memory, introduced in 1973.

History

The Executive was launched in September 1972 at the price of GB£79.95 plus VAT, around half the price of comparable calculators, but still twice the average weekly wage.^[2][3][4] It was one of the first mass-produced hand-held calculators, and its introduction to the market coincided with a number of other companies entering the calculator market.^[4][5]

Clive Sinclair, reckoning that the market for "executive toys" was not especially sensitive to price, ordered components for 100,000 calculators.^[6] The Executive was highly successful, and made 1.8 million pounds profit for Sinclair Radionics.^[7] It was well received by foreign markets as well as domestically, with US$1.5 million worth of Executives sold in Japan in early 1974 at six times the price of Japanese ones.^[8] The parts, consisting of the chip, 22 transistors, 50 resistors and 17 capacitors, cost close to GB£10, compared with a sale price of close to GB£80.^[9]

It was described as "at once a conversation piece, a rich man's plaything and a functional business machine" by Design Magazine.^[10] An example of the calculator is displayed at the Museum of Modern Art in New York, and the futuristic design earned it the Design Council Award for Electronics in 1973.^[7][11]

Texas Instruments, using the same chip, had produced a calculator that was longer and wider and over three times as thick and a great deal more expensive.^[9]

A Sinclair Executive purchased by a Russian diplomat exploded exploded in his breast pocket, allegedly leading to an official Soviet investigation.^[10] It was found that it had been left on by accident, leading to a current drain on the batteries that overheated them until they burst.^[12]

Design

It was significantly smaller than any of its competitors, and the first calculator that could easily be carried in a pocket.^[2][13] According to a Sinclair executive quoted in the Financial Times, "one must always bear a packet of cigarettes in mind as the ideal size," possibly a quip on Clive Sinclair's smoking habit.^[9] The Executive weighed only 2.5 ounces (71 g) and measured 56 by 138 by 9 millimetres (2.20 × 5.43 × 0.35 in).^[13] The case, designed by Richard Torrens and made of black injection-moulded polycarbonate, required flexible glue the hold the two halves together.^[9]

Functions

As well as four-function arithmetic, the Executive had the ability to compute squares, reciprocals, and multiply or divide by a fixed constant.^[6]

Chip

The calculator was powered by a Texas Instruments GLS 1802, a metal oxide semiconductor integrated circuit with 7000 transistors.^[6][1] An chip of this kind normally consumes 350 milliwatts, but by pulsing the power this requirement was reduced to 20 milliwatts.^[6] It was discovered that an early prototype using the 1802 chip worked if the batteries were disconnected and then reapplied quickly enough.^[14]

Power is supplied to the chip in 1.7 microsecond pulses as determined by the storage time of a control transistor. An oscillator clock operating at 200 kilohertz during calculations and dropping to 15 kilohertz between each operation means shut off time ranges from 3.3 microseconds during calculations to over 65 microseconds between.^[6] The device relies on the capacitance of the chips to store information when there is no power, and 1.7 microseconds proved sufficient for the chip to carry out a single change of state of the electronics.^[6] Any calculation can be done in 1000 such changes.^[6]

This had the effect of extending battery life to about 20 hours of continuous use with three small hearing aid batteries, equivalent to about four months of normal usage.^[13][6]

Executive Memory

The Executive Memory was launched in November 1973, with the same physical dimensions as the original, but 1 Kilobyte of memory.^[15][16] There were at least 3 versions, including the black and white Type 1, and the Type 2 with a gold keyboard.^[15][16] The Executive Memory sold at the lower price of GB£24.95.^[7]

References

Citations

Sources

• Dale, Rodney (1985). The Sinclair Story. Duckworth. ISBN 9780715619018.