Sinclair Wrist Calculator
{{Short description|Wrist-worn calculator introduced in 1977}}
{{ infobox calculator
| name = Sinclair Wrist Calculator
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| designfirm = Sinclair Instrument
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| introduced = February 1977
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| processor = Mostek MK50321N
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| display_type = Light-emitting diode
| display_size = 8 digits
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| supply = 8.1V
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| dimensions = {{convert|47|x|45|x|18|mm}}
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The Sinclair Wrist Calculator was a wrist-worn calculator produced by Sinclair Instrument and introduced in 1977.
History
The Wrist Calculator was launched in February 1977 by Sinclair Instrument, a company established in parallel to Sinclair Radionics when the latter started to encounter financial difficulties.{{cite web |url=http://www.vintagecalculators.com/html/wrist_calculator.html |title=Sinclair Wrist Calculator |publisher=vintagecalculators.com |accessdate=26 January 2014}}
It was only available as a mail-order kit, and cost around {{GBP|11}}.{{cite web |url=http://oldwww.nvg.ntnu.no/sinclair/calculators/wristcalc.htm |title=Sinclair Wrist Calculator |publisher=Planet Sinclair |accessdate=26 January 2014}} Despite the difficulty in assembling the kit due to the small size of the parts and their variability in specification, 10,000 were sold around the world. 20,000 were exported to the United States, but most went unsold and were returned to Sinclair. It was described as an "utter dud" and "impossible-to-build" by the journal International Design.{{cite journal |url=https://books.google.com/books?id=mfY4AQAAIAAJ&q=Sinclair+Wrist+Calculator |title=International Design |year=2005 |volume=52 |issue=5–8 |page=105}}
Design
The design used 10 keys, with a three-position switch to select the correct function. The switch was held to the left to access the functions to the left above the keys, and to the right to get the functions to the right above the keys. In the centre position it would enter the numbers on the keys.{{cite journal |url=https://books.google.com/books?id=quIDAAAAMBAJ&pg=PA195 |title=Unique full-function 8-digit wrist calculator... available only as a kit |journal=Popular Mechanics |date=April 1977 |page=195}}
It used normal algebraic logic, as opposed to the reverse Polish notation employed on some Sinclair calculators.