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How AT&T Works

What AT&T Did (and Still Does)

After the Kingsbury Commitment, AT&T was off and running. Now with government sanction, AT&T was free to fulfill Vail's vision of "universal service." In the succeeding decades after 1913, AT&T consolidated its hold on the market and continued to expand almost uninterrupted until 1949. By that time, AT&T was a monopoly with no equal.

To give a sense of the scope of AT&T's functions at it height, imagine if Alexander Graham Bell invented the automobile instead of the telephone. AT&T would have owned and built the entire interstate highway system, every service station, even every traffic light and road sign. No one would "own" a car. Automobiles would be rented to subscribers. Every toll booth would pay Ma Bell, and there would be no freeways to drive on -- much less free roads.

That's exactly what AT&T did for telephones. It manufactured the device and built the network for that device to transmit its messages along. The Bell System represented the world's first complex electronic network. The standards AT&T set for the composition of its ever growing network are the same standards and systems applied to networking today, no matter what kinds of devices are being connected.

AT&T breaks the network down in to three elements: transmission, switching and management. One way or the other, all modern networks are organized in this way.


Transmission covers all media used to transmit a voice signal. In the beginning, copper wires strung between exchanges carried the signal. As distances increased, attenuation forced long-distance lines to become thicker to help maintain the signal. Properly spaced loading coils helped diminish resistance on the line, decreasing the need for thicker wires. The development of vacuum tube repeaters ushered in the transcontinental telephonic age.

Transmission technology continued to evolve with the development of the transistor. The transmission path evolved to broadband delivery via coaxial cable, wireless relay, satellite communication and fiber optic cable. AT&T built and deployed cables across the ocean floor and underground over long distances. Enabling transmission was key to AT&T's growth, as well as essential to achieving "universal service."


Without switching, you would need to have a cable for each person you called via landline. Switching enables specific routes to be used over and over again. Your call begins at your local exchange. Depending on where it's going, it will then be relayed to a long-distance call center or to another local exchange, moving from node to node along a hierarchal chain until your call reaches its destination.

In the early days of the telephone, operators did the switching manually. A caller would tell an operator where he wanted his call to go, and that operator would have to figure out how to route that call through the transmission network. As time went on, a hierarchy was established for routing calls. For long distance, your local exchange would use one of 2,000 toll offices to one of 140 primary centers, which then connects to one of eight regional centers and then back down the chain to the local exchange for the location of your call. AT&T kept this hierarchy in use until the 1980s. By then, the switching had become automated and instantaneous. (For more information on switching, check out How Telephones Work.)


The development of this hierarchy was the result of network management. We take network management for granted today, given that all electronic data transmission now travels over a network. AT&T had to develop it from scratch. As phone traffic increased, management became as important to making calls happen as the equipment enabling the call. What began as individual operators discovering the best way to complete a call circuit became a highly complex combination of automated systems and traffic monitors coordinating millions of calls a day.

AT&T could manage increasing volumes of traffic because it controlled the network. As a de facto national utility, AT&T could direct its resources through a central command structure. This approach could not have been achieved in a system of multiple networks managed by multiple competing providers. A monopoly had to build and manage a single system before providers could compete for delivery of service on that system. For proponents of the monopoly, the network and its management justified its existence.