Texas Instruments SR-51-II Handheld Electronic Calculator

This handheld electronic scientific calculator is a modification of the earlier SR-51 and SR-51A. It has a black plastic case with an array of forty small rectangular plastic keys. All but five of these keys have a “dual function”—one function is indicated on the key, the other on the keyboard above the key. This makes it possible to use keys to perform conversions from some common to metric measures, rather than using the system of codes employed on the SR-51. A key also can be used to convert from degrees to radians, something performed by a switch on the SR-51.

Text above the keys reads: TEXAS INSTRUMENTS SR-51-II. Behind the keyboard is an on/off switch. Behind this is an LED display that shows ten-digit positive and negative numbers and two-digit positive and negative exponents. The jack for a charger/adapter is on the right side of the calculator.

Text on the back of the calculator (there is no sticker) reads: TEXAS INSTRUMENTS (/) electronic calculator (/) SERIAL NO. (/) 6389263 LTA5076 (/) ASSEMBLED IN USA. An empty battery pack inside the middle of the back is marked: TEXAS INSTRUMENTS (/) ELECTRONIC BATTERY BP-5.

There are no screws to easily take apart the calculator. The device has a black plastic zippered case.

References:

[Advertisement], Boston Globe, September 26, 1976, p. 87. Lists calculator as a new product from Texas Instruments that sells for $67.95.

[Advertisement], New York Times, March 6, 1977, p. 98. Lists calculator as selling for $54.95.

[Advertisement], Washington Post, September 14, 1978, p. A19. SR-51-II on sale for $29.95, a $20 savings.

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