Texas Instruments TI-55

Date of introduction:  1977 Display technology:  LED-stick
New price:   Display size:  8 + 2
Size:  5.8" x 3.1" x 1.4"
 148 x 78 x 36 mm3
Weight:  6.4 ounces, 180 grams Serial No:  1111794
Batteries:  BP7 Date of manufacture:  wk 46 year 1979
AC-Adapter:  AC9132 Origin of manufacture:  USA
Precision:  11 Integrated circuits:  TMC1503
Memories:  10    
Program steps:  32 Courtesy of:  Joerg Woerner
Download leaflet:   (US: 2.0 MByte) Download manual: (US: 10.8 MBytes)

The TI-55 continued the line of scientific calculators with statistical capabilities started with the SR-51 and continued with the SR-51A and SR-51-II. In Europe the same calculator was marketed as TI-51-III, mathematically and historically correct.

The TI-55 was introduced shortly after [or before - continue here] its sibbling MBA with advanced financial and statistical capabilities. 

TI-55_PCB.jpg (83662 Byte)From a technical aspect the TI-55 continued the ideas of the SR-40 with three main differences: The LED-stick using LED chips mounted and bonded to the printed circuit board, was expanded to 12-digits instead of the 9-digits. The ON/OFF key was replaced by a mechanical slider and the battery connector was changed from a 9V battey style to a small 3-pin header. As a consequence the usage of cheap 9V batteries wasn't possible.

If we discover the sources of the components used in this TI-55 we locate:

The LED chips were furnished by the SC Group in Dallas.
The lens by an Ohio supplier. 
The circuit board and the IC are from TI Singapore. 
The board assembly was by TI Taiwan. 
The keyboard was made at TI Lubbock and assembled to the board in the Lubbock or Abilene plant.

The TI-55 added 4 keys to do some kind of programming. A small memory hold up to 32 key-codes to repeat simple calculations with different entry values. In comparision to the TI-57 the capabilities were lousy.

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

Simply by comparing the designation of the integrated circuits of the advanced line "Majestic" calculators, you'll get the all members of this family:

TMC1501    TI-57 
TMC1502    MBA
TMC1503    TI-55

From the TI-55 two different versions were reported, one with and without chrome-border around the display. Compare with the chromeless TI-55.

Don't miss the later TI-55 II sporting a stylish slanted housing and the modern LC-display.

Introduction of the TI-55

TI-55-Proto_PCB.jpg (44672 Byte)Recently we received from a fellow engineer of a Dallas based company a box with some calculator prototypes. One of the surprises was a very early TI-55. The internal construction of the calculator was already final, the only missing item was the date code on the calculator chip. The housing itself carried with the magic LTA2577 number some confusing information. We assume that the TI-55 was introduced after the MBA released in August, 1977. Two explanations:

The TI-55 was released together with the TI-57 in May or latest June 1977.
The TI-55 prototype uses a housing of the TI-57 and carries a wrong date code.

The TI-55 is featured in the Texas Instruments Incorporated bulletin CL-318 dated 1977.

Find here an excerpt from the Texas Instruments Incorporated leaflet CL-199J dated 1981:


An advanced slide rule calculator with statistical functions and simple programmability.

Science. Engineering. Statistics. Social Science. Whatever your field.
Packed with the features and functions to handle almost any mathematical operation, from logarithms and trigonometry to more advanced statistical problems.
Powerful statistical capability mean, variance, standard deviation, linear regression. Simple keyboard programmability with 32 steps lets you perform repetitive calculations at the touch of a key. Ten user-accessible memories are available to increase the flexibility of calculations.
Calculator Decision-Making Sourcebook shows you how to use the advanced functions of the TI-55 in making better decisions, whatever your field or profession.

* Registered Trademark of Texas Instruments Incorporated

Texas Instruments, 1981


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If you have additions to the above article please email:

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