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The Evolution of Communication Networks

November 22, 2010 - 0 Comments

By Steven Shepard, Contributing Columnist

When the telephone network became a commercial offering in the waning years of the 19th century, its architecture was quite different than the switch-centric, hub-and-spoke system that we have today. In that first iteration there was no concept of switching, the mechanical or electrical process of setting up a temporary connection between two parties for the duration of the call.

To talk with David on the telephone in those days, I would have had to have a dedicated circuit installed between my house and his. If I also wanted to be able to call my son or daughter, I would have to have additional circuits installed from my house to theirs.

This leads to what is known in the world of network topology as the “n times n minus one over two problem.” N is the number of people who want to be able to communicate with each other, and the little equation yields the number of circuits that must be installed to allow n people to talk with each other. Five people require ten circuits, but beyond that the number goes exponential. For a small city of 35,000 people like Burlington, Vermont, where I live, the number of circuits required to connect the city this way would be somewhere north of 600 million.

In those early days, wires were dragged over rooftops, attached to the walls of houses, and strung in great sagging bundles between poles. Clearly, this meshed architecture was an untenable model.

Please Hold, While I Connect You…

Relief came with the evolution from a meshed model to the hubbed model I mentioned earlier. Instead of connecting every customer permanently to every other customer, the circuits were instead connected to a central “hub” — today’s exchange or central office.

There, human operators would establish temporary connections between callers on-demand. The first operators were young boys, but they proved to be so rude to customers that they were soon replaced by women and the iconic voice of Ma Bell. Operators, then, were the world’s first telephone switches.

Before long, as telephone service became increasingly popular, it became clear that a single operator could not handle the call requests of more than about 100 customers. As a consequence the number of operators grew, and they sat at long switchboards, establishing and tearing down calls as required. Some of the boards were so long that supervisors wore roller skates to help them move efficiently from operator to operator.

Invention of the Automatic Telephone Switch

The story takes an interesting twist in 1891 when Almon Strowger, an undertaker in Kansas City, Missouri, changed the direction of telephony in a fascinating and far-reaching way.

One morning it dawned on him that his business was declining, and since the death rate in Missouri hadn’t gone down, he concluded that there had to be another cause. A little bit of investigation on his part turned up an interesting factoid: his only competitor was married to the town’s telephone operator, which meant that any calls that came in for the undertaker went directly to her husband. Strowger didn’t stand a chance.

Or did he? A lifelong tinkerer and part-time inventor, Strowger came to the conclusion that the answer to the one-sided undertaker monopoly was to take the operator out of the picture and give the caller the ability to choose, rather than placing that responsibility into the hand of Ma Bell.

He did this when he invented the Strowger Switch, which gave customers the ability to dial the person they wanted to talk to directly, without operator intervention. That switch became the step-by-step switch, the mainstay of the telephone network for over 50 years. Funny isn’t it? Once again, technology prevails over human foible!

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