Sinclair Wrist Calculator

The Sinclair Wrist Calculator was a wrist-worn calculator produced by Sinclair Instrument and introduced in 1977.

Sinclair Wrist Calculator
IntroducedFebruary 1977
Design firmSinclair Instrument
Calculator
Display typeLight-emitting diode
Display size8 digits
CPU
ProcessorMostek MK50321N
Programming
Other
Power supply8.1V
Dimensions47 by 45 by 18 millimetres (1.85 in × 1.77 in × 0.71 in)

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.[1]

It was only available as a mail-order kit, and cost around GB£11.[1][2] 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.[2] It was described as an "utter dud" and "impossible-to-build" by the journal International Design.[3]

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.[4]

It used normal algebraic logic, as opposed to the reverse Polish notation employed on some Sinclair calculators.[4]

References
  1. "Sinclair Wrist Calculator". vintagecalculators.com. Retrieved 26 January 2014.
  2. "Sinclair Wrist Calculator". Planet Sinclair. Retrieved 26 January 2014.
  3. "International Design". 52 (5–8): 105. Cite journal requires |journal= (help)
  4. "Unique full-function 8-digit wrist calculator... available only as a kit". Popular Mechanics: 195. April 1977.
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