Flanagan never expected to be an electrical engineer. He grew up on a cotton farm in Mississippi and figured he'd stay there. In fact, when offered a choice between a typing course and a physics course in high school, he selected physics only because the encyclopedia definition, "the study of natural phenomena and how to use them," implied that physics could be useful in cotton farming.

This pioneer in voice communications didn't even have a telephone—or electricity—during most of his childhood. The farm was too far from any town to be on the grid until the Communications Act of 1934 and the Rural Electrification Act of 1936 extended phone and electricity networks into rural America.

Getting electricity at about age 12 was, for Flanagan, like getting a new toy. He read about Guglielmo Marconi, got some instruction manuals, and built a spark-gap transmitter, using a spark coil from a Model T. He also made arc lamps, wired an induction coil to a doorknob to shock his brother, and built a telephone system, pirating the carbon button microphone from his home telephone, since he couldn't afford to buy that expensive part.

In the summer of 1943, Flanagan took engineering classes at Mississippi State University, Starkville, biding his time until he turned 18 and could join the U.S. Army, where he hoped to become a pilot. A mild deficiency in color vision got him booted out of the pilot training program and reassigned to communications. As part of that group, he was trained to maintain and operate the first radar-based air traffic control systems, a job that gave him his first exposure to nonlinear circuits and precision engineering.

In 1946 he went back to Mississippi State, turning down the Army's offer—an 18-month stint testing nuclear bombs on Bikini Atoll. This time he entered the university as an electrical engineering major, determined to learn how to design the type of systems he had been working with in the Army. After graduating from Mississippi State, he accepted a graduate assistantship in MIT's acoustics lab, which led to his seminal research in voice coding.

And that led to a job, in 1957, at what was then called Bell Telephone Laboratories, in Murray Hill, N.J., where Flanagan would spend the next 33 years. "I hired him because of his interest in speech and hearing—and because he was a prize student," recalled Edward E. David Jr., then executive director at Bell Laboratories and later science advisor to President Richard M. Nixon. "He brought a new look to the whole area of communications."