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Texas Instruments T-1220 distributed by True Value

Date of introduction:  1976 Display technology:  LED-stick
New price:  $9.95 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:  A 226135
Batteries:  9V  Date of manufacture:  wk 23 year 1976
AC-Adapter:  AC9180 Origin of manufacture:  USA
Precision:  8 Integrated circuits:  TMS0972
Memories:      
Program steps:   Courtesy of:  Joerg Woerner

Texas Instruments introduced the TI-1200 in March 1975 and followed within just a few months with the TI-1250 featuring a 4-key Memory and a [CS] or [+/-] key. The TI-1200/TI-1250 family developed into one of TI's most successful calculator series, selling millions and millions units not only under its own name plate but branded for different companies like HEMA, Koh-I-Noor Hardtmuth, True Value Hardware Stores, Zayre Corporation and Western Auto.

Maybe there is a story behind this calculator - and its TI-1250 based sibling T-1225? One source (The National Museum of American History's Chip Collection, Comments by Bill Heye, Ralph McCullough) tells us that this calculator was planned as a regular TI product. Shortly after approval of the calculator by the QRA the project was stopped.

The box of the T-1220 proudly states: Custom model manufactured for True Value Hardware Stores

The warranty address on the back of the calculator is: Texas Instruments Service Facility. Later T-1220 models removed this text.

Dismantling the featured T-1220 calculator with Date code 2376 LTA and manufactured in June 1976 in Lubbock, Texas reveals a very efficient and cost-optimized design 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.

The TMS0952 used with the original TI-1200/TI-1250 was soon replaced with the TMS0972, a pin-compatible design dropping the additional resistors and capacitor and further reducing the manufacturing costs of the calculators.

Learn more about the evolution of the TI-1200 between March 1975 and its discontinuation in 1977.

Learn more about the different Product Labels used with the TI-1200 - here at the Datamath Calculator Museum we classify the featured T-1220 as Hardware Version 3, PCB Type 2 and Product Label Style 4, A-Series 6-Digit.


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

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