Texas Instruments SR-56 Handheld Electronic Calculator

Texas Instruments SR-56 Handheld Electronic Calculator

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Description
This scientific calculator is a modification of the Texas Instruments SR-50A and a less expensive device than the contemporary SR-52. 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 clear key, the calculator has twenty-one further keys. Many keys (including some of the number keys) take on a second function if the "2nd" key is pushed. This second function is indicated on the keyboard above the key. Texas Instruments advertised this as a programmable calculator.
Text above the keys reads: TEXAS INSTRUMENTS SR-56. 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-56. It also gives the serial number SR-56 2400279. It also reads: Assembled in USA. Above the sticker is a battery compartment. A mark below the sticker reads: LTA1677.
Unscrewing three screws on the back reveals the workings of the calculator. It has six chips, three relatively large. One of the large ones is marked: TMC0538NL (/) P 7650. This is a TMC0538 chip, manufactured in 1976. Another is marked: TMC0501NL (/) EP 7706. This is a TMC0501 chip, manufactured in 1977. The third is marked: TMC0537NL (/) AP 7644.
The calculator comes in a black plastic, cloth-lined, zippered case with loop.
References:
[Advertisement], Boston Globe, February 4, 1976, p. 31. New, programmable SR-56 advertised as selling for $179.95.
[Advertisement], Los Angeles Times, February 28, 1976, p. OC_A5. New programmable SR-56 selling for $179.95. Compatible with PC-100 printer.
[Advertisement], Washington Post, April 23, 1976, p. B4. Calculator has list price of $179.95, sale price of $159.95. Also lists SR-52, with program strips, selling for $359.95.
[Advertisement], Los Angeles Times, July 10, 1976, p. C5. Lists SR-56 as having list price of $179.95, sale price of $89.95.
[Advertisement], Los Angeles Times, October 9, 1976, p. C7. Lists SR-56 as selling for $89.95, regular price $109.95.
[Advertisement], Los Angeles Times, December 22, 1976, p. D8. Price for SR-56 $85.
[Advertisement], Los Angeles Times, May 28, 1977, p. C4. Price for SR-56 $79.
Location
Currently not on view
Object Name
electronic calculator
date made
1977
maker
Texas Instruments
Physical Description
plastic (case; keys; carrying case material)
metal (circuitry; zipper material)
Measurements
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
1986.0988.355
catalog number
1986.0988.325
accession number
1986.0988
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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Comments

I own a SR-56 calculator that is in excellent condition (complete with Manuals, Charger, and Case). Although the Battery Pack is still intact, I am concerned that it might someday corrode. What do you suggest that I do to preserve the product and battery pack? Thank you.
Behind the keyboard is a switch that may be set at R (radians) or D (degrees). The key should read G (gradians) or D (degrees). Wikipedia The gradian is a unit of measurement of an angle, equivalent to 1/400 of a turn, 9/10 of a degree, or π/200 of a radian. The gradian is defined as 1/100 of the right angle (in other words, there are 100 gradians in the right angle), which implies a full turn being 400 gradians. To change it radians, you press 2nd RAD.

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