Texas Instruments SR-50A Handheld Electronic Calculator

Texas Instruments SR-50A Handheld Electronic Calculator

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This scientific calculator is a modification of the Texas Instruments SR-50. A handheld electronic calculator, it has a black plastic case with an array of forty small rectangular plastic keys. In addition to ten digit keys, a decimal point key, a change sign key, a total key, four arithmetic function keys, a clear entry key, and a clear key; the calculator has twenty-one further keys. Some are for entering exponents, pi, storage, recall, summation, exchange, powers, squares, square roots, reciprocals, factorials, general roots, hyperbolic functions, conversion between radians and degrees, natural logarithms, exponents, and common logarithms. Four keys are for trigonometric functions and inverse trigonometric functions.
Text above the keys reads: TEXAS INSTRUMENTS SR-50A. Behind the keyboard is a switch that may be set at R (radians) or D (degrees). Next to it is an on/off switch. Behind the keyboard is an LED display that shows ten-digit positive and negative numbers and two-digit positive and negative exponents.
The calculator has a jack for a recharger/adapter along the back edge. A sticker on the back gives instructions. It reads in part: TEXAS INSTRUMENTS (/) SR-50A. It also gives the serial number SR-50A 875346. It also reads: Assembled in USA. Above the sticker is a compartment for three batteries. A mark below the sticker reads: 3375DTA.
Unscrewing three screws on the back reveals the workings of the calculator. It has six chips, two relatively large. One of the large ones is marked: TMC0521NL (/) ΔE7535-5. This is a TMC0521 chip, manufactured in 1975. The other is marked: TMC0501NL (/) DΔ7533-5. This is a TMC0501 chip, manufactured in the same year.
The calculator comes in a black plastic, cloth-lined, zippered case with belt clip.
[Advertisement], Los Angeles Times, June 28, 1975, p. C6. Gives a reduced price of $89.95.
[Advertisement] Boston Globe, July 9, 1975, p. 22. Gives a price of $84.95.
[Advertisement], Los Angeles Times, August 30, 1975, p. OC A5. Gives a price of $84.95.
[Advertisement], Los Angeles Times, November 26, 1975, p. B5. Gives a reduced price of $79.76.
[Advertisement], Los Angeles Times, April 10, 1976, p. C7. Gives a reduced price of $58.85.
According to the online Datamath Museum, accessed May 15, 2015, the calculator was introduced in March of 1975 at an initial price of $109.50.
Guy Ball and Bruce Flamm, The Complete Collector’s Guide to Pocket Calculators, Tustin, CA: Wilson/Barnett, 1997, p. 154. They give a 1975 price of $109.50.
Currently not on view
Object Name
electronic calculator
date made
Texas Instruments
Physical Description
plastic (case; carrying case; keys material)
metal (jack; circuitry material)
paper (sticker material)
cloth (lining of carrying case material)
overall: 1 1/4 in x 3 in x 5 3/4 in; 3.175 cm x 7.62 cm x 14.605 cm
ID Number
catalog number
accession number
Credit Line
Gift of John B. Priser
See more items in
Medicine and Science: Computers
Handheld Electronic Calculators
Computers & Business Machines
Data Source
National Museum of American History
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I stored my SR-50A away in 1980, when I bought a new model. Well, I took it out this year and it still works! I did make a new battery pack though. I have the belt holster, and wore it on my belt when I went to Northeastern in 1976, and in the subway as well. What a nerd I was! Glad to see my model in the Smithsonian!
I have this calculator with the original battery, minus the charger. The battery pack is dead, but I was able to power up the calculator using 4.5vdc from a variable power supply, and am happy to report it works. I remember borrowing this calculator from my dad when I was in high school, and now that he's passed on, I have it to use, and have memories back when i was 15 yrs old, and using it in school.

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