Sinclair Executive

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Sinclair Executive
Sinclair Executive Type 1
IntroducedSeptember 1972
Invented byClive Sinclair
Cost£79.95
Calculator
Display typeLight-emitting diode
Display size8 digits
CPU
ProcessorTexas Instruments TMS1802NC[1][2]
Frequency200 kHz
Other
Power supply4 button cells
Power consumption20 milliwatts
Dimensions56 by 138 by 9 millimetres (2.20 in × 5.43 in × 0.35 in)

The Sinclair Executive was the world's first "slimline"

pocket calculator, and the first to be produced by Clive Sinclair's company Sinclair Radionics
. Introduced in 1972, the calculator was produced in at least two versions with different keyboard markings; a variant called the Sinclair Executive Memory was introduced in 1973.

Its small size was made possible by pulsing current to the Texas Instruments TMS1802 "calculator on a chip" integrated circuit, reducing the power consumption more than tenfold. The Executive was highly successful, making £1.8 million of profit for Sinclair and winning a Design Council Award for Electronics.

History

The Executive was launched in September 1972 at the price of £79.95 plus

VAT, equivalent to £1,120 in 2021 when adjusted for inflation. This was around half the price of comparable calculators, but still twice the average weekly wage.[3][4][5] It was the first pocket calculator, and the first to be mass-produced, and its introduction to the market coincided with a number of other companies entering the calculator market.[5][6]

Clive Sinclair, reckoning that the market for "executive toys" was not especially sensitive to price, ordered components for 100,000 calculators.[7] The Executive was highly successful, and made 1.8 million pounds profit for Sinclair Radionics.[8] It was well received by both domestic and foreign markets, and US$1.5 million worth of Executives were sold in Japan in early 1974 at six times the price of Japanese models.[9] The parts, consisting of the TMS1802 chip, 22 transistors, 50 resistors and 17 capacitors, cost close to £10, compared with a sale price of close to £80.[10] The Executive impressed the engineers at Texas Instruments, who had used the same chip to produce a longer and wider calculator that was over three times as thick and a great deal more expensive.[10] In 1974, sales of the Executive were greater than £2.5 million, and Sinclair was producing 100,000 calculators each month, of which 55% were exported.[11]

A Sinclair Executive purchased by a Russian diplomat exploded in his breast pocket, allegedly leading to an official Soviet investigation.[12] 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.[13]

Design

It was significantly smaller than any of its competitors, and the first calculator that could easily be carried in a pocket.[3][1] 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.[10] The Executive weighed 2.5 ounces (71 g) and measured 56 by 138 by 9 millimetres (2.20 in × 5.43 in × 0.35 in).[1] The case, designed by Iain Sinclair,[14] was made of black injection-moulded polycarbonate and required flexible glue to hold the two halves together.[10]

Design Magazine described it as "at once a conversation piece, a rich man's plaything and a functional business machine".[12][15] One Executive is on display at the Museum of Modern Art in New York City, and the futuristic design earned it the Design Council Award for Electronics in 1973.[8][16] It was the first calculator designed for aesthetic appeal, and New Scientist described it as "not so much a professional calculator - more a piece of personal jewellery".[10]

Functions

As well as four-function arithmetic, the Executive could compute

floating decimal point.[15]

Microprocessor

The calculator was powered by a Texas Instruments TMC1802NC, a

CPU normally consumes 350 milliwatts, but by pulsing the power this requirement was reduced to 20 milliwatts.[7] It was discovered that an early prototype continued to work if the batteries were disconnected and then reapplied quickly enough, as the capacitors in the circuit could hold a charge for up to five seconds.[17]

Power is supplied to the chip in 1.7-microsecond pulses as determined by the storage time of a control

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 more than 65 microseconds between.[7] 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.[7] Any calculation can be done in 1,000 such changes.[7] This extended battery life to about 20 hours of continuous use with three small hearing-aid batteries, equivalent to about four months of normal usage.[7][1]

Screen

The screen on the Executive was a monolithic seven-segment

light emitting diode display bought from a Canadian firm.[18] The small screen reduced the power consumption and material costs,[15] but it was revised several times in pursuit of lower power consumption, creating reliability problems.[19]

Executive Memory

The Executive Memory was launched in November 1973, with the same dimensions as the original, but with the ability to memorise subtotals from any number of chain calculations.[20][21][19] There were at least three versions, including the black and white Type 1, and the Type 2 with a gold keyboard.[20][21] The Executive Memory sold at the lower price of £24.95.[8]

References

  1. ^ a b c d e Tout, Nigel. "Sinclair Executive and Sinclair Executive Memory". Vintage Calculators Web Museum. Retrieved 15 September 2017.
  2. ^ Tout, Nigel. "The Calculator-on-a-Chip". Vintage Calculators Web Museum. Retrieved 15 September 2017.
  3. ^ a b "Have you got a Sinclair Executive?". BBC. Archived from the original on 15 April 2003. Retrieved 6 December 2013.
  4. ^ "A sectioned Sinclair Executive pocket calculator, 1972". Science Museum. Archived from the original on 12 December 2013. Retrieved 6 December 2013.
  5. ^ a b Cockshott, Mackenzie & Michaelson 2012, p. 90
  6. ^ Tout, Nigel. "Calculator Time-line". Vintage Calculators Web Museum. Retrieved 26 January 2014.
  7. ^ a b c d e f g h Information, Reed Business (20 July 1972). "Pocket calculators add up to a big market". New Scientist: 144. {{cite journal}}: |first1= has generic name (help)
  8. ^ a b c "Executive". www.vintagesinclair.co.uk. Retrieved 6 December 2013.
  9. ^ Dale 1985, p. 53
  10. ^ a b c d e Dale 1985, p. 45
  11. ^ Dale 1985, p. 54
  12. ^ a b Rawsthorn, Alice (4 March 2012). "Farewell, Pocket Calculator?". New York Times. Retrieved 6 December 2013.
  13. ^ Dale 1985, pp. 55–56
  14. ^ Torrens, Richard. "Sinclair Executive calculator". Retrieved 23 January 2023.
  15. ^ a b c Rowlands, David (1973). "The push-button abacus". Design: 36–7.
  16. ^ "Executive Pocket Calculator". The Museum of Modern Art. Retrieved 6 December 2013.
  17. ^ Dale 1985, p. 44
  18. ^ "Clive Sinclair: "creative electronics" visionary". InfoWorld. Vol. 4, no. 47. Infoworld Media Group Inc. 29 November 1982. pp. 112–116.
  19. ^ a b Dale 1985, p. 48
  20. ^ a b Tout, Nigel. "Sinclair Executive Memory". Vintage Calculators Web Museum. Retrieved 6 December 2013.
  21. ^ a b "Sinclair Executive Memory". mycalcdb.free.fr. Retrieved 6 December 2013.

Further reading

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