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Exactra 21 Prototype by Texas Instruments 

Date of introduction:  July 1974 Display technology:  LED-modules
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:  none
Batteries:  3*AA  Date of manufacture:  wk 09 yr 1974
AC-Adapter:   Origin of manufacture:  USA
Precision:   Integrated circuits:  TMS0803
Memories:      
Program steps:   Courtesy of:  Joerg Woerner

The rare prototype of the Exactra 21 uses a different display construction compared to the later series model. Instead the cheaper Bowmar Opto-Stick or LED display with Chip-on-Board (COB) technology we noticed 9 small LED-modules with an additional magnifier lens. We we compiled an overview of all Exactra Calculator LED Displays.

Fellow calculator collector David Butler reported recently a Eactra 21 calculator manufactured in week 34 sporting the 9 LED-modules and we assume that Texas Instruments switched in August 1974 to Bowmar Opto-Stick and in February 1975 to COB technology.



The printed circuit board (PCB) of the prototype is already in the final design stage. The date code found on the TMS0803 single-chip calculator circuit indicates a manufacturing date of week 9 or early in March 1974.


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

© Joerg Woerner, October 17, 2003. No reprints without written permission.