Texas Instruments Little Professor (1976 Version A)

Date of introduction:  June 13, 1976 Display technology:  LED-stick
New price:  $19.95, 11.95 Display size:  8
Size:  5.0" x 3.5" x 1.1"
 127 x 89 x 29 mm3
Weight:  4.2 ounces, 119 grams Serial No:  034204
Batteries:  9V   Date of manufacture:  wk 37 year 1976
AC-Adapter:   Origin of manufacture:  USA (LTA)
Precision:   Integrated circuits:  TMS0975/ZA0356 AP
Memories:   Displays:  DIS713
Program steps:   Courtesy of:  Joerg Woerner
    Download manual:   (US: 7.3M Bytes)

You certainly know this cute math trainer, the Little Professor. Millions and millions were sold in the past 4 decades from this simple but funny educational product. The basic idea behind the Little Professor is opposite to a normal calculator: The child has to type the answer of simple questions like "3 + 5 = ?". You can choose between the four basic math functions and four different grade levels. If the child gives a wrong answer "EEE" occurs, otherwise another of more than 16000 different questions is asked.

This educational toy was rated by Texas Instruments for children aged between 5 and 9 years.

LittleProf_LTA4276_PCB.jpg (131577 Byte)From the technology this First Generation Little Professor introduced in Summer 1976 is related to the TI-1200 calculator of the same year. You'll notice a similar evolution during the production of the Little Professor to optimize manufacturing costs but a minor mishap added one interims step not observed with the TI-1200 and its sibling TI-1250 and all their variations like the fancy T-1225. The pictures on the right compares two Little Professors, an early one and a later one. Here at the Datamath Calculator Museum we named them based on the Revision of the used single-chip calculator circuits accordingly Version A, Version B, Version C, and Version XC.

Dismantling the featured Little Professor (Version A) with Date code LTA 3776 and manufactured in September 1976 in Lubbock, Texas reveals an internal construction very similar to the TI-1200/TI-1250. The single-sided printed circuit board (PCB) is centered around a TMS0975/ZA0356 single-chip calculator circuit and powered by a 9V alkaline battery. The keyboard with 5 rows of keys is borrowed from the TI-1200 although the Little Professor is using only 4 rows of keys.

The TMS0975/ZA0356 chip is a member of the TMS0970 Product Family introduced in March 1976 with the TI-1200 and based on the TMS1000. The TMS0970 integrated both segment and digit drivers to the TMS1000 feature set allowing for highly cost-optimized designs and paving the way of four-banger calculators with 4-key memory selling below the magic $10 threshold. While the original TMS0970 chips were housed in a standard 0.6 wide 28-pin DIP (Plastic Dual In-line Package with a 0.1 / 2.54 mm lead pitch), started Texas Instruments in 1977 to use a smaller 0.4 wide 28-pin SPDIP (Shrink Plastic Dual In-line Package with a 0.07 / 1.778 mm lead pitch) design.

Preparing our DCM-50A Platform to allow the Characterization of Single-Chip Calculator Circuits of the TMS0970/TMC0900 Family, we studied a TI-1270 calculator manufactured in July 1976, this Little Professor (Version A) manufactured in September 1976, a TI-1200 manufactured in October 1976, a Little Professor (Version B) manufactured in December 1976, a TI-1250 calculator manufactured in August 1977, a Little Professor (Version C) manufactured in May 1978, a WIZ-A-TRON educational toy assembled in June 1978 and a Little Professor (Version XC) manufactured in September 1978. Learn more about the Bearcat 210 Computer Radio Scanner unleashing the potential of the TMS0970 chip.

Summarizing the internal design of the Little Professor (1976), we differentiate between two different printed circuit boards and four different versions:

Version PCB
Date codes
Date codes
Display Comments
Version A 1014912 3476 LTA 4676 LTA TMS0975NL
ZA0356 AP
DIP28 DIS713 Original
Version B 1014912 4776 LTA 5076 LTA TMS0975NL
ZA0356 BP
DIP28 DIS713 External
Clock Osc.
Version C 1014928 1577 MTA 1878 MTA TMS0975NL
ZA0356 CP
SPDIP28 DIS713 Cost
Version XC 1014928 2778 MTA 0479 MTA TMS0975NL
ZA0356 GCS
ZA0356 KCS
SPDIP28 DIS713 Final

Please notice that the above table lists only Little Professor (1976) units manufactured in the Lubbock and Midland, Texas facilities, it was actually manufactured in Italy, too but design changes were typically introduced in the US facilities first.

While the "look and feel" of the four versions of the Little Professor (1976) is identical, did we encountered significant differences in the software implementation of the TMS0975NL chips despite their identical "ZA0356" marking. Follow this link to deep dive into the TMS0975NL/ZA0356.

We provided physical samples of the three different TMS0975NL Single-Chip Calculator Circuits located in the Little Professor (Version A, Version B, and Version C) to Sean Riddle who not only de-capped and photographed the silicon chips but even extracted the raw ROM transcriptions and PLA programming for both the Output and Instruction Decoders from the pictures for future emulation in the MAME Framework.

We expected some changes in the Output Decoder PLA of the three different Versions of the Little Professor but couldn't spot the differences yet.

Texas Instruments did not only change the internal pieces of the Little Professor over time, even the Product Labels on the rear of the calculators evolved over the years and we differentiate for the US version between four evolutions:

Style 1 (3476 LTA - 3476 LTA): Label with Serial Number and Country of Origin, Label for Battery Type (inside), Date Code and Manufacturing Facility heat-stamped
Style 2 (3676 LTA - 1477 LTA): Label with Serial Number and Country of Origin, Date Code and Manufacturing Facility heat-stamped
Style 3 (2077 MTA - 4877 MTA): Serial Number, Country of Origin, Date Code and Manufacturing Facility heat-stamped
Style 5 (5077 MTA - 0479 MTA): Country of Origin, Date Code and Manufacturing Facility heat-stamped

This first version of the Little Professor could easily recognized by the two sliding switches to the left and right of its face, in December 1978 they were replaced by three additional keys [OFF], [SET] and [LEVEL] slightly disturbing the design of the product. Meet the Little Professor (1978).

Another education toy of this time are the rare MATH MAGIC and its sibling WIZ-A-TRON.

The Little Professor was mentioned in TI's press release dated August 15, 2002 to celebrate the 35th anniversary of its invention of the electronic calculator.

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

Little Professor. A fun way for children to practice basic math facts.

The Little professor is a unique product designed specifically to aid children 5 years and older in exploring basic mathematics. Although it is not truly a calculator, the Little Professor generates a sequence of problems over 16,000 preprogrammed problems in all and involves children in math practice through an enjoyable instant feedback and reinforcement situation.

By using the four-position switch indicating degrees of difficulty, and the appropriate function key ([+], [ࢤ], [x], [÷]), the teacher can select a range of random math problems needed for individual students. The student can then work independently as he progresses toward mastering math skills.

Problems appear on the large LED display as an equation, and the child is given three opportunities to input the correct answer through the keyboard. An error indication is displayed for one second each time the child incorrectly answers the problem. If the correct answer is not given in three chances, the completed equation appears in the display, allowing the child to see the mistake. By pressing [GO], he can then proceed to the next problem. If the child inputs the correct answer, the complete equation is displayed for one second and a new problem appears. As an additional incentive, the Little Professor displays the score of correct first answers after each set of 10 problems.

Powered by a single nine-volt disposable battery, the Little Professor is fully portable and is perfect for individual students use in the class room.

Texas Instruments, 1976

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If you have additions to the above article please email:

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