Vintage electronic calculators

Sept. 16, 2022
by Mark Ollig

Last week’s column mentioned the Sinclair computer I used in 1981.

Another computing device I used in 1976 was a handheld electronic calculator.

The company I purchased this calculator from started in 1930 as Geophysical Service, an independent contractor specializing in reflection seismograph methods within the ground.

Its name was changed to Texas Instruments Incorporated in 1951 and is today headquartered in Dallas, TX.

Texas Instruments, a semiconductor and technology manufacturer, began work on its first handheld electronic calculator in 1965.

They named their calculator Cal Tech. It was an experimental prototype and not yet ready for commercial resale.

Cal Tech was a binary-coded decimal calculator that handled the essential four arithmetic functions: addition, subtraction, multiplication, and division.

It was a small rectangular device measuring about 4.25 by 6.15 by 1.75 inches, weighed a little over two and a half pounds, and was battery-powered.

In 1964, Canon Inc., based in Japan, engineered and built a working prototype electronic calculator called the Canon Canola 130.

It used 545 germanium semiconductor transistors and hundreds of germanium diodes soldered onto circuit boards. It weighed 45 pounds.

In 1968, Canon began selling the Canola 130S electronic calculator for $995, which today is equivalent to the purchasing power of $8,641.

In 1970, Texas Instruments negotiated with Canon Inc. to manufacture a commercial version of Cal Tech, which had proven to be a reliable electronic device.

Cal Tech became known as the Pocketronic calculator.

In 1971, the Pocketronic was sold in the US for $345, equivalent to $2,568 in today’s purchasing power.

The Pocketronic has been called the first handheld, battery-powered, paper printing electronic calculator.

The Pocketronic had no electronic display. Instead, the device printed typed calculations and the results on a strip of thermal paper tape fed from a plastic cassette spool made by 3M Corp.

The electronics inside the Pocketronic included the Texas Instruments TMC1730B, TMC1731A, and TMC1732A electronic integrated circuit packages.

Although called a “Pocketronic” calculator, it weighed two and a half pounds, and its length was 8.2 inches.

Also, in 1971, Busicom (formerly The Nippon Calculating Machine Corp) manufactured what some call the first genuine “pocket-sized” electronic calculator, the Busicom LE-120A.

The LE-120A calculator included an impressive 12-digit red LED display and is reportedly the first electronic calculator to use an LED display.

It was powered with four six-volt AA batteries, weighed 10.5 ounces, and was priced at $395 in 1971, the same buying power as $2,940 today.

On December 4, 1975, the Smithsonian Institution accepted Texas Instruments’ donation of their original 1965 Cal Tech prototype handheld calculator.

In 1976, Texas Instruments began selling their T-1225 solid-state electronic handheld calculator for $24.95, equivalent to $132 today.

I purchased a Texas Instruments T-1225 in 1976.

The T-1225 calculator was a custom model manufactured by Texas Instruments for the True Value hardware store chain.

The calculator’s box has the following text, “Custom Model manufactured for True Value Hardware Stores.”

The Texas Instruments T-1225 measures 1.25 by 2.625 by 5.375 inches, weighs 3.7 ounces, and is about the same size as those transistor pocket radios we used during the 1960s.

It is an eight-digit microelectronic calculator using red LEDs (Light-Emitting-Diode) to display digits typed and computation results across its thin, horizontal screen.

The T-1225 calculator is powered using a single nine-volt transistor battery or with the Texas Instruments AC adapter model AC9180.

The T-1225 featured logic technology known as VLSI (Very Large-Scale Integration), which creates an integrated circuit by combining large numbers of metal-oxide-semiconductor transistors onto a single computer chip. In the case of the T-1225, it is an integrated circuit package called TMS0972.

During the late 1970s, the buyer’s market for pocket-sized handheld electronic calculators dramatically increased as the cost of owning one decreased.

Businesses, students, and the general public appreciated the convenience of having a portable electronic “personal calculating device” one could hold in the palm of their hand.

During the 1970s, some electronic calculator manufacturers used LCD (liquid-crystal display) screens because of their low power consumption and cost.

However, the LCD turned out not to be as reliable (parts of the LCD digit would sometimes fade out); thus, manufacturers ended up selling more electronic calculators with longer-lasting LED displays.

We had fun with those early electronic calculators, such as typing the number “0.7734” and then turning the calculator upside down to see the word “hello.”

Today, my vintage 1976 Texas Instruments T-1225 calculator resides on the memorabilia bookshelf.

I am happy to report it still worked fine after installing a new nine-volt transistor battery.

While talking with my brother Mike, I learned he still has his Keystone SC 656 handheld electronic calculator from 1975.

And yes, it still works.

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