The “Model K” lays groundwork for digital computing


If you need inspiration for using your free time wisely, look no further than Bell Labs computer pioneer George Stibitz. One weekend during fall 1937, Stibitz (who was born April 30, 1904) sat at his kitchen table and used a small assortment of items to build a device that could add and subtract binary numbers, laying the groundwork for the future of digital computing.

Stibitz’s supply list included relays, which are metallic devices that open and close based on passage of an electric current, as well as dry cell batteries, plywood, flashlight bulbs, and metal strips cut from a tobacco can. A lit bulb equated to the binary number “1” and an unlit bulb to “0.”

His colleagues were amused and called the device “Model K” after the kitchen table where it was created. It might have ended there, if it was not for Stibitz’s innate curiosity. He kept going and developed plans for more complex computations. That was when Bell Labs took note, moving from amusement to intrigue. This relay device could potentially work far more quickly than the human “computers” in the laboratory.

Stibitz introduces the CNC

Stibitz did not stop there, as he continued to push forward with his innovations for digital computing. Working with switching engineer Samuel Williams, Stibitz developed the Complex Number Calculator (CNC), which could add, subtract, multiply and divide complex numbers—the type of computations it took multiple operations on a desk calculator to complete. What’s more, the CNC could be operated remotely via three Teletype machines across Bell Labs.

On Sept. 11, 1940, Stibitz demonstrated the CNC at Dartmouth College during an American Mathematical Society meeting. Attendees could enter a math problem into a Teletype at Dartmouth. The Teletype would communicate with the CNC back in New York, and a moment later the Teletype would display the computation’s result.

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