Montgomery Ward P800 aka TXI-8642A

Date of introduction:   Display technology:  LED-modules + lens
New price:   Display size:  8
Size:  5.8" x 3.4" x 1.45"
 147 x 87 x 37 mm3
Weight:  10.1 ounces, 287 grams Serial No:  37B-26340
Batteries:  4*AA NiCd Date of manufacture:  year 1973
AC-Adapter:   Origin of manufacture:  USA
Precision:  8 Integrated circuits:  TMS0109 or TMS0103, 2*SN75491, 2*SN75492
Memories:   Displays:  DIS40, DIS95
Program steps:   Courtesy of:  Joerg Woerner

This boxy calculator does not look like a Texas Instruments product. To identify it, you have to know more about the coding on the product labels used by Montgomery Ward:

Models starting with

TXI were manufactured by Texas Instruments
DAN were imported by APF Electronics, Inc.
DNS were manufactured by National Semiconductor (later Novus)
EKJ were imported by Kings Point Corporation
GLE were manufactured by Lloyd's Electronics, Inc.

TXI-8642A_PCB.jpg (56146 Byte)If you dig deeper into the calculator you'll notice that the P800 is very similar to the TI-2500 Datamath. The circuit diagrams look identical, the single-chip calculator circuit is either the TMS0109 borrowed from the TI-3000 or the TMS0103 found in the Bowmar 901B. The other components located on the printed circuit board (PCB) of the featured calculator manufactured in 1973 are well known from the reference design of the TMS0100, namely two SN75491 Segment Driver chips and two SN75492 Digit Driver chips, each for the LED display composed of two pre-configured LED-modules (DIS40, DIS95) are based on the TIL360 arrays and soldered directly to the PCB. The remaining components on the PCB are mainly used to generate the necessary supply voltage of the TMS0103 and its clock signal for the internal timing. 

TXI-8642A_2.jpg (71924 Byte)The keyboard is clearly identified as a standard
Klixon™ product manufactured by Texas Instruments. The color of the housing, the LED-modules and some other details like the rubber feet are known from the Datamath calculator.

First_TI.jpg (52283 Byte)A similar calculator was sold by Longines Symphonette with the Electronic Calculalator and by Radio Shack with the EC-200.

Don't miss the rare TXI-8661A based on the Exactra 23 calculator.

Datamath™ and Klixon™ are trademarks of Texas Instruments.

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If you have additions to the above article please email:

© Joerg Woerner, December 5, 2001. No reprints without written permission.