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Exactra 21 (Second Design) by Texas Instruments 

Date of introduction:  February 1975 Display technology:  LED-stick
New price:   Display size:  8
Size:  5.1" x 2.9" x 1.3"
 130 x 74 x 34 mm3
   
Weight:  5.1 ounces, 144 grams Serial No:  2100297344
Batteries:  3*AA  Date of manufacture:  wk 09 yr 1975
AC-Adapter:   Origin of manufacture:  USA
Precision:   Integrated circuits:  TMS0803
Memories:      
Program steps:   Courtesy of:  Joerg Woerner

The Exactra 21 with it's brown keyplate uses a 8-digit display and similar electronics to the TI-1500 and TI-2500-II calculators. All three were available in the same period, this gives you an idea of the positioning in the marketing of each calculator:

Datamath solid and well established since 1972
TI-1500 modern and stylish
Exactra 21 young and cheap



Dismantling this Exactra 21 calculator manufactured by Texas Instruments in March 1975 reveals a design very similar to the original Exactra 21 but adopting the display technology of the cost-reduced Exactra 19 introduced in Fall 1974. We compiled an overview of all Exactra Calculator LED Displays.

The keyboard makes still use of the costly double-shot injection molding process and the keyboard assembly is identical with the Exactra 20. Please notice the the LED-display found in this particular calculator was manufactured by Bowmar. We know the Opto-Stick display with its small numbers already from the TI-2500B.

The double-sided printed circuit board (PCB) of the Exactra 21 makes use of the TMS0803 single-chip calculator circuit and a tiny display driver. The remaining parts form a small power-converter to use the 3 AA-sized batteries instead a 9V battery block.

Don't miss a rare prototype of the Exactra 21 manufactured in early in 1974, probably only few weeks before the formal market introduction. Main difference to the later production model is the display construction. 

If you are interested in the Exactra series you should view the remaining siblings Exactra 19, Exactra 20, Exactra 22 and Exactra 23. Complete the line with the TI-2000 and Exactra 31.

 

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If you have additions to the above article please email: joerg@datamath.org.

Joerg Woerner, January 4, 2018. No reprints without written permission.