Eric joined Bell Laboratories in 1948 and soon established himself as an engineering inventor par excellence, specializing in switching and transmission systems development. He led the development of the first commercial pulse-code modulation system. This T1 system became the most widely used transmission system in North America and signaled the start of the digital era. He was promoted to director of Bell Labs' work on antisubmarine detection systems, where he applied new automated detection and data processing to those worldwide systems. In 1967 he was promoted again, to executive director of the Transmission Media Division with responsibility for a new laboratory in Atlanta, Georgia, tied to a ''mother'' factory in the same city. This period in his career saw the birth of electronic loop transmission systems, so-called SLC systems, and the design and manufacture of early optical fiber and cable systems. Spurred by the recurring service problems of the early 1970s, he pioneered the design of a family of "operations systems"—computers, software, sensors/controllers and terminals—used to design, install, monitor, operate, and reconfigure as well as maintain complex communications systems—a field that now pervades not just communications but all businesses, from airlines to banks.
He was elected vice-president, Computer Technologies and Military Systems Division in 1981. Under his drive, the many internal versions of UNIX were coalesced into a single operating system for universal use, allowing portable application software—an area of growing commercial importance. He foresaw the need for increased software productivity as a business necessity and led a major architectural and technical thrust to satisfy this need. Over a three-year period, he managed to triple the productivity of certain software systems. Then from 1984 until his retirement in late 1989, Eric was vice-president of operations systems and network planning.
Eric Sumner was an expert in research and development management and business analysis, especially troubleshooting, functional audits, and efficiency evaluation. He was granted eleven patents and several honors. He received the following awards: the Alexander Graham Bell Medal of the IEEE; the