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Texas Instruments TI-2500B (Datamath) Handheld Electronic Calculator

Texas Instruments TI-2500B (Datamath) Handheld Electronic Calculator

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Description
This is an example of an early handheld electronic calculator marketed by Texas Instruments under its own name. The calculator has a tan plastic case with a dark brown keyboard. It has an array of eighteen keys, sixteen of them square and two rectangular. These include ten digit keys, a decimal point key, a total key, four arithmetic function keys, a clear entry key, and a clear key. A switch at the right in the top row of keys may be set at “CHAIN” or “CONST.” A mark above this switch reads: Datamath. Behind the keyboard is an eight-digit LED display.
A jack for a power outlet is along the back edge. An on/off switch is on the left side.
The back of the calculator has a compartment for storing either three rechargeable nickel-cadmium batteries or four AA sized non-rechargeable batteries. According to Flamm, it is the presence of this compartment that distinguishes the TI-2500 from the TI-2500B.
A sticker on the compartment cover reads: TI-2500B electronic calculator. It also reads in part: Datamath (/) electronic calculator (/) A Product of Texas Instruments Incorporated. It also reads in part: Serial Number (/) 2500B 564926. The sticker indicates that the calculator had a built-in battery that gave four to six hours of portable operation and could be fully recharged in ten hours using an AC9130 adapter/charger.
Unscrewing three long screws on the back of the case does not reveal the chips.
This modification of the TI-2500 was introduced in 1974 and discontinued the same year.
Compare 1986.0988.188, 1986.0988.189, 1986.0988.190, 1986.0988.342, and 1986.0988.359.
References:
Guy Ball and Bruce Flamm, The Complete Collector’s Guide to Pocket Calculators, Tustin, CA: Wilson/Barnett, 1997, p. 157.
Online Datamath Museum, accessed May 13, 2015.
Location
Currently not on view
Object Name
electronic calculator
date made
1974
maker
Texas Instruments
Physical Description
plastic (case; keys; feet; circuit board material)
metal (circuitry material)
paper (sticker material)
Measurements
overall: 1/2 in x 2 3/4 in x 5 1/2 in; 1.27 cm x 6.985 cm x 13.97 cm
ID Number
1986.0988.190
accession number
1986.0988
catalog number
1986.0988.190
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 was the engineer that designed the Datamath2500B. I received a patent on the switching that allowed 4 NiCad or 3 alkaline batteries. (never was used). I also built the only prototype for the LCD version. TI had produced a chip for the LCD version. It took me 2 month to kill the project because the chip had a DC component that turned the LCDs they had black in about 10 minutes.

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