Texas Instruments TI-40

Date of introduction:  1982 Display technology:  LCD
New price:  $25.00 Display size:  8 (5+2)
Size:  5.8" x 3.1" x 0.90"
 147 x 79 x 23 mm3
Weight:  3.7 ounces, 106 grams Serial No:  2885585
Batteries:  2*LR44 Date of manufacture:  wk 45 year 1981
AC-Adapter:   Origin of manufacture:  USA (ATA)
Precision:   Integrated circuits:  TP0455/CD4507 or TP0456/CD4557
Memories:  1    
Program steps:    Courtesy of:  Joerg Woerner
    Download manual: (US: 6.3M Bytes)

This TI-40 looks somewhat odd. If you compare it with the TI-55-II you notice that the upper line of keys is missing. The advantage of the TI-55-II compared with the slimline calculators like the original TI-35 was the bigger display and the extra line of keys. And now this one - the electronics and the display of a slimline calculator in the slanted housing.

Difficult to understand, but on Texas Instruments' production lines in 1982. Roughly four years later we received with the slanted TI-53 again a hybrid between a slimline and slanted calculator.


Dismantling this TI-40 manufactured end of 1981 in Abilene, Texas reveals the TP0456/CD4557 single-chip calculator circuit known from the second generation of the TI-35. We spotted in earlier models of the TI-40 a TP0455/CD4507 chip.

Read more about the "CD4507+50=CD4557" equation here.

If you are interested in the calculating accuracy of scientific calculators don't miss the Calculator forensics.

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