Amos Joel: Electronic switching, cellular roaming


Amos Joel, like other honorees on our list this year, was responsible for developing more efficient ways to communicate via not only the landline wireline telephone, but also the wireless phone.

Amos Joel

Joel (Image source:

Joel, who spent 40 years at Bell Labs, is best known for three major breakthroughs in the telecommunications industry: electronic switching, the Traffic Service Position System (TSPS), and cellular roaming.

While Joel's early work at Bell Labs focused on cryptology studies with Claude Shannon, a 2011 FierceTelecom innovators honoree, to help the Allied Powers in World War II, his interest in electronic switching began as student at the Massachusetts Institute of Technology (MIT). At MIT, he worked under the direction of Vannevar Bush (the founder of Raytheon) on the Rockefeller-funded differential analyzer project, and wrote a thesis on functional design of relays and switch circuits.

But it was between the years 1948-1960 when Joel began writing his story in the telecom history books when he conducted studies on electronic switching systems.

The results of those studies helped drive the advent of the Number One Electronic Switching System (1ESS), one of the first stored program control exchanges (SPC), which are telephone exchanges controlled by a computer program. AT&T (NYSE: T) introduced the 1ESS into the former Bell System in Succasunna, N.J. in May 1965. In addition to helping to move electronic switching into commercial use, Joel also designed automatic telephone billing equipment.

Later, Joel created the Traffic Service Position System (TSPS) used to automate telephone operators' work; the Automatic Intercept System (AIS) to automatically handle calls to non-working numbers; and Automatic Message Accounting (AMA) to provide detailed billing for telephone calls.

During his 43 years at Bell Labs, Joel filed over 70 patents, but the one lasting innovation that ties Joel with today's communications reality is his contribution to the wireless industry. Long before the Apple's (Nasdaq: AAPL) iPhone caught fire, Joel helped create a method for cellular handoff, which enables a wireless phone user to make an uninterrupted call while moving from one phone region to another, in 1972.  

One of Joel's Bell Labs supervisors who was quoted in his obituary in The Telegraph in October 2008, said that "Without his invention there wouldn't be all these people walking around with cell phones."

While most users just expect their cellular calls and landline phone calls, even if they are driving around town, or to pick up a phone and get dial tone, without Joel's innovation, neither would be part of today's communications reality.