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Miscellaneous Calculator Photo Library

Texas Instruments' Cal-Tech Handheld Calculator Prototype
Image Courtesy of Texas Instruments
Used with Permission

This is a photo of one of very few Texas Instruments (TI) "Cal-Tech" proof-of-concept battery-powered printing electronic calculators made. The Cal-Tech was an internal TI project to develop advanced integrated circuit technology for application in what could potentially become a consumer product. Prior to the development of the desktop electronic calculator, integrated circuits were only used in commercial computers, military/national security systems and spacecraft(manned & un-manned) electronics.

The idea of using digital integrated circuit technology in consumer-market products could potentially open up a floodgate of opportunities for sales of advanced ICs for use in consumer consumer devices. The problem at hand was figuring out just what kind of device could address the consumer market that would need the complexity of digital integrated circuis. Television and radio technology had begun to look into the use of analog integrated circuits to reduce the component count and complexity (as well as cost), but the only consumer product using digital logic that existed at the time that was was the desktop electronic calculator.

The proof-of-concept project at TI's Semiconductor R&D Laboratory got its start in 1965 at the direction of TI's president, Patrick E. Haggerty[3/17/1914-10/1/1980]. Haggerty and one of TI's engineers, Jerry Merryman, happened to be on a plane flight together. During the flight, they they chatted about the possible uses of advanced integrated circuits in the consumer marketplace. The result of the discussion was an idea for a pocketable, battery-powered electronic calculator that was low-priced enough for the consumer market. The thought was that this could create a huge demand for advanced digital IC's for calculators, and Texas Instruments could be poised to fill that demand.

As a result of the discussion, Haggerty decided to fund a proof-of-concept project to develop the technology to product such a calculator. The project got its start in 1965 at Texas Instruments' Dallas, TX, Semiconductor Research & Development Lab. Haggerty appointed three key members of a small team dedicated to the development of the calculator. The leader of the team was Jack Kilby[11/8/1923-6/20/2005] (one of the original inventors of the first integrated circuit). Along with Kilby were Jerry Merryman [6/17/1932-2/27/2019], and James Van Tassel[2/15/1929-6/19/2018]. The three men quickly began the development of the logic design, and built a breadboard version of the logic for the calculator using TI's off-the-shelf small-scale digital integrated circuits so that the basis for the design could be made tried and true before committing the logic to the large-scale integrated circuits used in the Cal-Tech. Once this large prototype (consuming two stacked layers of hand-wired breadboard circuits placed on a large piece of plywood) was working properly, the process to reduce all of this logic down to a small number of highly complex digital ICs began.

The first-article Cal-Tech became operational in December of 1966, using large-scale bipolar, discretionary-wired gate-array integrated circuit technology that was far ahead of its time. The calculator was completely self-contained, with a rechargeable battery pack included. The only exterior part was a small power-pack that would serve to run the calculator on AC power, as well as charging the internal battery. TI's choice of bipolar technology was unusual in that there were limits to the complexity of bipolar ICs as opposed to the up-and-coming Metal Oxide Semiconductor (MOS) technology that made it possible to create much smaller and less complicated transistors than bipolar devices could allow. TI's expertise was with bipolar IC technology, and they had not yet invested deeply in MOS devices, leading to the bipolar large-scale devices being the choice for use in Cal-Tech. The logic of the calculator breadboard was implemented in the gate-array chips, which provided a large number of logic devices arranged on the chip such that a layer of metallization could be deposited on top of the array of logic elements that connected them together to create the logic of the calculator. The calculator used four of these gate-array devices, as well as three bipolar shift-register integrated circuits used for storing the calculator's working registers. The Cal-Tech used a new thermal printer technology developed by Texas Instruments for data logging equipment. The thermal printer printed out the inputs and results of calculations by energizing tiny heating elements on a ceramic substrate that would form the image of the digits and symbols a narrow strip of special thermally-sensitive paper that was manufactured for TI by 3M (Minnesota Mining & Manufacturing).

In the end, Texas Instruments' management team did not support Haggerty's proposal of the company entering the rapidly-changing electronic calculator market itself, but was interested in partnering with an existing calculator company to develop a commercially-viable version of the Cal-Tech. Cal-Tech itself was simply too expensive to make to be a practical product, but it did prove that Texas Instruments had the skills and technology needed to develop such a device as a proof-of-concept.

A small number of calculator companies were shown the Cal-Tech. Amongst them was Canon, a company that was already a large customer of TI's small and medium-scale off-the-shelf integrated circuit technology for its early IC-based desktop calculators (an example being the Canon 141). When shown the Cal-Tech, Canon's executives and engineers expressed a strong interest in developing a calculator like Cal-Tech for production as a commercial product. A partnership was quickly put together for joint development of such a calculator, which became a product in the Canon Pocketronic. The Pocketronic calculator, which ended up a bit longer, but not quite as wide as the Cal-Tech, and was about the same thickness as the Cal-Tech, and weighed a little less because of the use of a plastic cabinet versus the metal cabinet of Cal-Tech. The Pocketronic became available for sale in Japan in the fall of 1970, and in the US in early 1971. The machine was "pocketable", but you needed a pretty good-sized pocket to hold it, though it would fit comfortably in an average executive briefcase, leaving plenty of room for other normal briefcase content.

The Canon Pocketronic was a direct descendent of the Cal-Tech, but was based on MOS integrated cicuits developed by TI. Texas Instruments had quickly developed it's MOS integrated circuit technology after it was realized that it was simply too costly to implement the complex logic required for devices like electronic calculators using bipolar chip technology as was used in the Cal-Tech. The Pocketronic proved to be a successful product for Canon, with the calculator becoming coveted by high-end executives as a "show-off" item.

The chips that TI developed for the Pocketronic were TI's first electronic calculator chipset, and set the stage for TI's eventual development of its first calculator-on-a-chip, which TI ended up using to produce its own electronic calculators for sale under the Texas Instruments brand.

The very first Cal-Tech calculator was presented to Pat Haggerty in March of 1967 as a momento of the development of the machine. When Haggerty left TI to go to work for NCR, he left the calculator in the care of Texas Instruments, who later gifted the machine to the Smithsonian's American Museum of Natural History, Kenneth E. Behring Center. The Cal-Tech is exhibited in the museum's permanent collection.

For more information, see the museums exhibit for the Canon Pocketronic.
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