Texas Instruments TI-1255 (Prototype)

Date of introduction:  (1976) Display technology:  LED-stick
New price:   Display size:  8
Size:  5.5" x 2.8" x 1.4"
 138 x 70 x 35 mm3
Weight:  3.9 ounces, 110 grams Serial No:  1242627
Batteries:  9V  Date of manufacture:  wk 16 year 1976
AC-Adapter:  AC9180 Origin of manufacture:  USA (LTA)
Precision:   Integrated circuits:  TMS0972
Memories:  1    
Program steps:   Courtesy of:  Joerg Woerner

TI-1255_BACK.jpg (406179 Byte)Texas Instruments took in 1976 in conjunction with mathematics educators at two major universities an initiative to introduce a group of 6 calculators for educational use. Including the Little Professor, the limited function ABLE calculator, the colorful TI-1205 and TI-1255, the TI-30 and the sophisticated SR-51-II, these calculators helped students understand and use math concepts from kindergarten through college and career.

The TI-1255 is based on the TI-1250 but includes rechargeable NiCd-batteries instead the standard 9V block battery. To enhance the readability of the keyboard both the size of the numerals and the color-scheme was improved.

The featured TI-1255 with Date code 1676 LTA and manufactured in April 1976 in Lubbock, Texas reveals an internal construction identical with the TI-1250 Version 3 with a single-sided printed circuit board (PCB) centered around a TMS0972 single-chip calculator circuit based on the TMS1000, the World's first Microcomputer.

This TI-1255 is probably an early design study or was used for sales demonstrations. We found several hints supporting this assumption:

The calculator is powered with a 9V battery instead the expected two
    rechargeable AA-sized batteries.
The black label on the back of the calculator reads TI-1250 while a known
    later model sports a white TI-1255 label.
The earliest calculators of the TI-1205, TI-1255 and TI ABLE trio in the
    final design (NiCd batteries, white labels) were manufactured in September 1976
    while this model was assembled already in April 1976.

The TI-1255 is one of the rarest members in the TI-12xx line and was sold only in the US.

Fellow collectors - if you own a Texas Instruments TI-1255 calculator,  please report us the serial number and date code from the back of the calculator for our Database.

Don’t miss the LADY 1200, a design developed by marketing guys to attack women’s hand-bags.

CB-272_Reunion.jpg (258368 Byte)On September 17, 2009 we were able to celebrate reunion of the calculators featured in the TI Learning Center Sales Leaflet CB-272 including three of the rarest portable electronic calculators.


Find here an excerpt from the TI Learning Center leaflet CB-272 dated 1976:

TI-1255. A rechargeable, full-function capability calculator with automatic constant and 4-key memory.

Texas Instruments rechargeable TI-1255 is well-suited for students in fundamental mathematics curricula. It includes the same features as the TI-1205, plus independent memory and change-sign key for entering negative numbers.

Using the TI-1255’s versatile memory system, students are able to store intermediate results and answers as they explore secondary level math topics. Students may add to [M+] or subtract from [M-] memory a displayed number without affecting the calculation in process. Stored numbers may be displayed by using memory recall [MR], and the memory can be cleared [MC] without clearing the calculator.

Convenient algebraic entry allows students to enter problems in the same order they would write them on paper. A touch of the change-sign key [CS] changes the displayed number from positive to negative or vice versa, and the bright 8-digit display and large keyboard numerals offer good visibility.

A supplement learning package “Calculator Math™ Fundamental Mathematics”, was developed and tested by the University of Denver Mathematics Laboratory for use with the TI-1255 expressly for the secondary level classroom.

© Texas Instruments, 1976

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© Joerg Woerner, October 22, 2009. No reprints without written permission.