Texas Instruments TI-1265

Date of introduction:  April 9, 1976 Display technology:  Fluorescent
New price:  $26.95 Display size:  8
Size:  5.5" x 2.8" x 1.4"
 138 x 70 x 35 mm3
Weight:  4.5 ounces, 127 grams Serial No:  A 1056444
Batteries:  9V  Date of manufacture:  wk 09 year 1977
AC-Adapter:  AC9180 Origin of manufacture:  USA (LTA)
Precision:  8 Integrated circuits:  TMS1043
Memories:  1    
Program steps:   Courtesy of:  Joerg Woerner

Texas Instruments introduced in March 1975 with the TI-1200 the first member of a very successful calculator family for budget oriented customers. The design of the TI-1200/TI-1250 was a result of continuous cost optimization and centered around a TMS0950 or TMS0970 single-chip calculator circuit driving directly a small LED display with 8 or 9 digits. This TI-1265 introduced in April 1976 traded the red LED display for a blue-green Vacuum Fluorescent Display (VFD) sporting not only larger and better readable digits but resulting in a longer lifetime of the 9V batteries, too. Main disadvantages of VFDs are the higher voltages required for its proper operation and the extra filament circuit, resulting typically in higher manufacturing costs.

Dismantling the featured TI-1265 with Date code 0977 LTA and manufactured in March 1977 in Lubbock, Texas reveals indeed a much more complex design than a TI-1250 manufactured in the same timeframe and having similar capabilities. Instead a very efficient and cost-optimized design with a single-sided printed circuit board (PCB) centered around a TMS0972 single-chip calculator circuit and no other components than an 8-digit display modules, do we recognize:

TMS1043 single-chip calculator circuit with integrated high voltage drivers, based on the TMS1000 - the World's first Microcomputer
DC/DC Converter Module to generate the high voltage (around -22V) for the Anodes and Grids of the VF-Display
ITRON 9-digit VFD Module

The TMS1043 was used with the TI-2550 III, too and sporting even [1/x], [x2] and [√x] keys.

The Dutch department store HEMA sold an identical model as reactor 1265.

Don't miss the rare Texas Instruments 1265 manufactured for Koh-I-Noor Hardtmuth.

Learn more about the evolution of the TI-1250 between June 1975 and its discontinuation in 1977.

Learn more about the different Product Labels used with the TI-1250 - here at the Datamath Calculator Museum we classify the featured TI-1265 as Hardware Version 1, PCB Type 1 and Product Label Style 4, A-Series.

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If you have additions to the above article please email:

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