Planet Sinclair

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Enterprise Programmable
O Executive /
Executive Memory
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Last updated
8 Jan 1998


sinclair@nvg.ntnu.no

Executive / Executive Memory

The Sinclair Executive was the very first Sinclair calculator, launched in September 1972 at a price of £79.95 + VAT. It was also the first pocket calculator, measuring 5.5" x 2.25" x 0.375" and weighing only 2.5 oz. The advert described it as being "as thick as a cigarette, reflecting Sinclair's stated belief that "One must always bear a packet of cigarettes in mind as the ideal size"; it was a running joke at Radionics that Clive, who smoked 40 cigarettes a day at the time, designed everything to be the size of a packet of 20.

By modern standards, the Executive was astoundingly limited: it had an eight-digit display and could add, subtract, multiply and divide - no other functions. It had automatic squaring, reciprocals and a choice of fixed or floating decimal points. Inside the case were 22 transistors, 50 resistors, 17 capacitors and the piéce de resistance, the Texas Instruments GLS 1802 integrated circuit, which the advert described breathlessly as "an electronic marvel... the largest ever produced for commercial use".

The Executive would vanish without trace nowadays, but in 1972 it was seen as a genuinely revolutionary advance (which in truth it was). Calculators prior to the Executive had been bulky, desk-bound affairs, often depending on mains power. The fundamental problem was the high power demands of the LED display: indeed, it was precisely that problem which drove the development of liquid crystal displays and ultimately killed off the LED-equipped calculators.

The advert for the Executive highlighted this problem, though it was a little disingenous about how Sinclair had resolved it:

"But the real genius lies in the circuitry linking the brain [sic], the batteries, the keyboard and the display. Circuitry soaks up power, which is why other pocket calculators have to use large batteries - and that, in turn, makes them bulky.

In the Executive, the Sinclair flair for miniaturisation has developed circuitry which absorbs virtually no power. Tiny hearing-aid batteries take up the minimum space and, used from time to time during the day, will last for several weeks."

In fact, what Sinclair had done was to exploit the persistence of the diode displays and the chip memory. It was immediately apparent that continuous demands on the batteries drained them very rapidly. Jim Westwood, Radionics' chief designer, discovered that if one disconnected the power and turned it on again fairly quickly, the display and the contents of the memory remained intact. With the transistors built into the circuit holding up to five seconds of charge, it was a simple matter to pulse the power on and off. It reduced the power demand from an unacceptable 350 milliwatts to a barely acceptable 30 milliwatts.

Even so, battery life was only a few hours and the machine could be physically dangerous. If it was left on, the batteries had a nasty habit of exploding and blowing the machine to bits. One day a telex arrived from Moscow. A senior Soviet diplomat had been carrying an Executive in his breast pocket when it exploded, convincing the unfortunate man and his entourage that he was suffering a massive heart attack. After the fuss had died down, investigators found that he had forgotten to switch the calculator off: the current drain was so high on the batteries that they grew hotter and hotter, finally exploding. Perhaps fortunately, the incident was accepted as an accident, rather than a capitalist provocation! Such were the joys of early 1970s electronics.

Such slight mishaps did not dent the Executive's deserved success, however. It was virtually the first attractively-styled calculator, its rivals and predecessors being utilitarian lumps of plastic. The neat design of the injection-moulded polycarbonate casing won its designer, Richard Torrens, the Design Council Award for Electronics in 1973. New Scientist described it as "not so much a professional calculator - more a piece of personal jewellery". Design magazine called it "at once a conversation piece, a rich man's plaything and a functional business machine". It was even exhibited at the Museum of Modern Art in New York, an event which Clive still holds dear. Good looks are so much taken for granted these days that such a reaction seems impossible for a modern calculator - which just goes to show how big an influence the Executive has had on the development of calculator design.

The Executive was a major success, earning Sinclair over £1.8m in profits, and was followed up at the end of 1973 with the Executive Memory. This had the eponymous extra feature and "a new black and white styling", at a far cheaper price of £24.95 + VAT.