The Engineering Book: From the Catapult to the Curiosity Rover: 250 Milestones in the History of Engineering

1876

Telephone

Alexander Graham Bell (1847–1922)

Imagine that the year is 1850 and you want to talk to someone. You have exactly one option: You can travel and meet with that person face-to-face, which could take days or weeks, depending on distance. Your alternative: a handwritten letter. Or, by 1850, the telegraph system has started to expand. But the simple act of talking to someone still requires a face-to-face meeting.

Enter the telephone. The patent for Alexander Graham Bell’s telephone was issued in 1876. The device itself was incredibly simple—a microphone made of carbon granules and a speaker. To connect two telephones together, all you needed was copper wire and a small source of electric current, like a battery—with this innovation, two people talked to each other at a distance for the first time.

How did engineers scale this up? The first innovation was the central office. In a town, copper wires ran from each home or business to the central office. An operator could connect any line to any other line in town. Wires are added to connect the town to the next town over. At that point, anyone in the two towns could communicate. As additional towns connected, this led to the creation of regional central offices. Eventually trunk lines spanned the country, then the world, and now everyone could connect to everyone else.

Engineers developed mechanical switches to replace the human operators. The telephone dial told the switches what to do. As a result, the cost of calling fell. Engineers created much smaller computers to replace the mechanical switches, and touch-tone dialing became possible. The cost of calling fell again. Engineers turned voice signals into digital bits and sent the bits through fiber optic cables, drastically reducing costs and increasing capacity. Then engineers created voice over IP (VoIP) so calls were routed through the Internet. Internet telephony was born and calling became free on many VoIP networks. The success story for engineering: taking something that used to be impossible and eventually making it free!

Illustrations depicting the Bell Telephone.