The History of ESS
by Lex Luthor

Of all the new 1960's wonders of telephone technology - satellites,
ultra-modern Traffic Service Positions (TSPS) for operators, the picturephone,
and so on - the one that gave Bell Labs the most trouble was, and unexpectedly
became the greatest development effort in Bell System's history, was the
perfection of an electronic switching system, or ESS. ESS should be well known
to many a technical enthusiast. It is known as the big brother of the phone
system, capable of controlling almost all aspects of any phone call and keeping
track of calling patterns. How ESS works and what it is capable of has been
covered previously in 2600 (February, 1984) and will be covered in future
issues.

It may be recalled that such a system was the specific end in view when the
project that had culminated in the invention of the transistor had been
launched back in the 1930's. After successful accomplishment of that planned
miracle in 1947-48, further delays were brought about by financial strategy and
the need for further development of the transistor itself.  In the early
1950's, a Labs team began serious work on electronic switching. As early as
1955, Western Electric became involved when five engineers from the Hawthorne
works were assigned to collaborate with the Labs on the project. The
president of AT&T in 1956 wrote confidently, "At Bell Labs, development of the
new electronic switching system is going full speed ahead. We are sure this
will lead to many improvements in service and also to greater efficiency. The
first trial will start in Morris, Illinois in 1959.". Shortly thereafter,
Kappel said that the cost of the whole project would probably be $45 million.
But it gradually became apparent that the development of a commercially usable
electronic switching system - in effect, a computerized telephone
exchange - presented vastly greater technical problems than had been
anticipated, and that, accordingly, Bell Labs had vastly underestimated both
the time and the investment needed to do the job. The year 1959 passed without
the promised first trial at Morris, Illinois; it was finally made in November
1960, and quickly showed how much more work remained to be done. As time
dragged on and costs mounted, there was concern at AT&T and something
approaching panic at Bell Labs. But the project had to go forward; by this
time the investment was too great to be sacrificed, and in any case, forward
projections of increased demand for telephone service indicated that within a
few years a time would come when, without the quantum leap in speed and
flexibility that electronic switching would provide, the national network would
be unable to meet the demand. In November 1963, an all-electronic switching
system went into use at the Brown Engineering Company at Cocoa Beach, Florida.
But this was a small installation, essentially another test installation,
serving only a single company. Kappel's tone on the subject in the 1964 annual
report was almost apologetic: "Electronic switching equipment must be
manufactured in volume to unprecedented standards of reliability...To turn out
the equipment economically and with good speed, mass production methods must
be developed; but, at the same time, there can be no loss in precision...."
Another year and millions of dollars later, on May 30, 1965, the first
commercial electronic central office was put into service at Succasunna, New
Jersey.

Even at Succasunna, only 200 of the town's 4300 subscribers initially had the
benefit of electronic switching's added speed and additional services, such as
provision for three party conversations and automatic trasnfer of incoming
calls. But after that, ESS was on its way. In January 1966, the second 
commercial installation, this one serving 2900 telephones, went into service in
Chase, Maryland. By the end of 1967 there were additional ESS offices in
California, Connecticut, Minnesota, Georgia, New York, Florida, and
Pennsylvania; by the end of 1970 there were 120 offices serving 1.8 million
customers; and by 1974 there were 475 offices serving 5.6 million customers.
The difference between conventional switching and electronic switching is the
difference between "Hardware" and "Software"; in the former case, maintenance
is done on the spot, with screwdriver and pliers, while in the case of
electronic switching, it can be done remotely, by computer, from a central
point, making it possible to have only one or two technicians on duty at a time
at each switching center.

The development program, when the final figures were added up, was found to
have required a staggering four thousand man-years of work at Bell Labs and to
have cost not $45 million but $500 million!


2600 Magazine, Volume 2, Number 11, November 1985