Sekimoto was immediately infatuated with the technology, which had not found much commercial success after its invention in the late 1930s. He was intrigued by PCM's ability to get messages through noise and became convinced he could use it to transmit high-quality signals over long distances, via repeaters.

While his company supported his work on this project, allowing his team to grow from five to 10 members, his superior at the laboratory gave him a piece of friendly advice: don't become too absorbed in this PCM technology, because it has no future. Indeed, most engineers in those days were skeptical about the viability of the new technology. Sekimoto thought otherwise, but he did not argue, just quietly continued his work.

“Typical,” says Michio Naruto, chairman of Fujitsu Ltd.'s Research Institute, in Tokyo. (Fujitsu is a longtime competitor of NEC.) “He is stubborn. He'll just say the same thing, year after year. You'll disagree, but next year he'll say the same thing; he won't change.”

Sekimoto later came up with this maxim to respond to such situations: “Majority is for today, minority is for tomorrow.”

Sekimoto's involvement in PCM led to another life-changing encounter. In 1965, Kokusai Denshin Denwa Co. (now KDDI Corp.), the Japanese international telecommunications carrier based in Tokyo, nominated him for a one-year post in the laboratories of the newly formed Communications Satellite Corp. (Comsat) in Washington, D.C., now part of Lockheed Martin Corp. Comsat was then part of Intelsat, the international satellite-communications consortium. Asked if he would like to apply for the job, Sekimoto worried that his then-rudimentary English wouldn't pass muster. Still, he decided to go for an interview.

The Comsat people, however, were so impressed by his résumé and research papers on PCM that they waived the interview and immediately offered him a post as a department manager. Though still unsure about his English, he decided to take the job.

“Chance,” he says, “is something you have to grasp with commitment, suppressing a feeling of uneasiness.”

O. Gene Gabbard, now a private investor and venture capitalist who in the 1990s was executive vice president and chief financial officer of MCI Communications Corp., was the first engineer to join Sekimoto's group at Comsat, just 10 days after Sekimoto had arrived as department head of modulation technique. “His English was pretty poor, but he could communicate anyway,” Gabbard recalls. “In our first conversation, we gestured, drew diagrams, and chose words that were easily understood. Still, I instantly liked and respected this man....I recognized immediately that he was a visionary.”

One of the key innovations of that Comsat group was a practical version of time-division multiple access (TDMA), a multiplexing scheme now used everywhere in international telephony, as well as in the Global System for Mobile Communications (GSM) cellphone system. The concept was not brand new: basically, TDMA takes a communications channel—a piece of radio bandwidth, say—and turns it into many channels by assigning different time slots to different channels. Before the Comsat group started working on the problem, researchers had studied time-division concepts for military-satellite communications, but had not yet applied it to commercial satellites.

Traditionally, the transponders on communications satellites were shared by simply giving each user a separate frequency. The scheme was fine for high-volume users, who could make use of all that transmission capacity, but was inefficient for medium- and low-volume users, who couldn't. A method was needed to let users share transponders and thereby achieve high overall efficiency. TDMA filled the bill perfectly: with computer controls, it would allow capacity to be adjusted dynamically, making the system extremely flexible and efficient.

There were challenges, of course, and some of the toughest revolved around the burst-mode communications that the system would employ. In practice, the data coming from an individual earth station would be sent as a burst of high-speed data that would have to be interleaved with the bursts from many other stations. To prevent any overlapping of all those bursts at the satellite, engineers put so-called guard times in between bursts from different stations; the fundamental design challenge is to synchronize the transmissions so accurately that those guard times are for all intents and purposes insignificant.