Texas Instruments SR-11 Handheld Electronic Calculator

This is an example of an early scientific calculator marketed by Texas Instruments. Building on the success of the SR-10, TI introduced it in 1973. The handheld electronic calculator has a black- and ivory-colored plastic case with an array of twenty-four small rectangular plastic keys. In addition to ten digit keys, a decimal point key, a change sign key, a total key, and four arithmetic function keys, the calculator has a reciprocal key, a square key, a square root key, a pi key, an enter exponent key, a clear key, and a clear display key. Text on the keyboard, just above the keys and two the left, reads: SR-11. A constant switch is to the right of this. Behind the keyboard is a twelve-digit LED display. A mark behind the display reads: TEXAS INSTRUMENTS. The on/off switch is right and slightly above this mark.

The back edge of the calculator has a jack for a recharger/adapter. A sticker on the back gives extensive instructions. It also gives the serial number SR-11 277378. A small sticker above this reads: INSPECTED (/) BY (/) J-01.

Unscrewing screws near the top and bottom of the back reveals the workings of the calculator. It has a total of five chips. The largest of these is marked TMS0602NC (/) 7427. This is a TMS0602 chip, manufactured in mid-1974. Also in the case is space for three AA nickel-cadmium batteries.

The calculator comes in a black plastic zippered case.

Texas Instruments described the SR-11 as an “electronic slide rule calculator,” hence the “SR” in the name. Ball & Flamm indicate that the calculator sold for $66.50 in 1974.

References:

Guy Ball and Bruce Flamm, The Complete Collector’s Guide to Pocket Calculators, Tustin, CA: Wilson/Barnett, 1997, p. 153.

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