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The Sinclair Executive electronic pocket calculator was the first slimline pocket calculator. The brainchild of designer Clive Sinclair, the device caused quite a stir on its release in 1972. At 56 by 138 by 9mm, it was a good deal thinner than its competitors.
The Executive used a Texas Instruments GLS 1802 chip and achieved its miniaturisation by using small mercury batteries. The device saved power by switching off power to the chip many times a second, relying on its undocumented ability to remember its state in the absence of voltage. This was discovered by Sinclair's chief engineer Jim Westwood, who made similar unorthodox contributions to many Sinclair products.
Photo credit: Science Museum
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