Micro Instrumentation and Telemetry Systems - Calculators

Calculators

Ed Roberts' interest in computers began in high school when he built a simple digital computer from relays. His first real experience with computers came while at Oklahoma State University where engineering students had free access to an IBM 1620 computer. Roberts' office at Weapons Laboratory had the state of the art Hewlett-Packard 9100A programmable calculator in 1968. In July 1970, a semiconductor company, Electronic Arrays, announced a set of six LSI ICs that would make a four-function calculator. Roberts was determined to design a calculator kit.

To fund the new project, Roberts sold 15% of MITS to fellow Air Force officer, Lieutenant William Yates. He also got an investment from another Weapons Laboratory officer, Major Ed Laughlin. Several other officers and scientist at the lab were interested in this state of the art calculator kit and helped with the design. Forrest Mims wrote the assembly manual in return for a calculator kit.

The MITS 816 was known as a "four-function" calculator; it could add, subtract, multiply and divide. The display was only 8-digits but the calculations were done to 16-digits of accuracy. The custom molded case gave the kit a professional appearance; the kit was $179 and an assembled unit was $275. The MITS 816 was featured on the November 1971 cover of Popular Electronics. Thousands of calculator orders came in each month, in contrast to poor results for previous kits that MITS had offered.

The steady flow of calculator sales allowed MITS to run full page advertisements in Radio-Electronics, Popular Electronics and Scientific American. In the June 1972 Radio-Electronics, MITS announced a 14 digit calculator (Model 1440) with memory and square root function for $199.95 kit and $249.95 assembled. The original 816 kit was reduced from $179 to $149.95. Both calculators could be controlled by upcoming programming unit.

The monthly sales reached $100,000 in March 1973 and MITS moved to larger building with 10,000 square feet (930 square meters) of space. To meet the demand for assembled calculators, an automated wave solder machine was installed. In 1973 MITS was selling every calculator they could make, 110 employees worked in two shifts assembling calculators.

The functionality of calculator ICs increased at a rapid pace and Roberts was designing and producing new models. The MITS 7400 scientific and engineering calculator was introduced in December 1972. It featured trigonometric functions, polar to rectangular conversion, two memories, and up to a seven-level stack. A kit with a three-level stack was $299.95 and an assembled unit with a seven-level stack was $419.95. The next month the Series 1200 four-function pocket calculators were announced. The six-digit model was $59.95 and the twelve-digit model was $99.95.

The Programmer accessory had been mentioned in the earliest advertisement but it was not featured until March 1974. This was the same size as a desktop calculator and could hold 256 programming steps. (It could be expanded to 512 steps.) It was limited to emulating calculator key presses and simple sequence branching. The programming was done by entering hexadecimal key codes. The combination of the MITS 7440 calculator and the programmer was not nearly as sophisticated as the HP 9830 calculator but $400 for both kits was a fraction of the HP price.