One hundred and thirty-eight years ago this week — on March 10, 1876, to be exact — Alexander Graham Bell spoke the first words into a "tele-phone," as it was called, to his assistant Thomas Watson, positioned at a receiver in another room. "Mr. Watson!" Bell exclaimed in staccato bursts. "Come here! I want to see you!" And for decades, telephones looked like elaborate pieces of furniture, affixed to walls and hard-wired out to the street, and up and down the blocks to local-area switchboards. If you wanted to talk on the phone, you had to go stand next to a wall.

What a difference just over a century makes! Modern smartphones still require electric power to operate, a microphone and speaker to translate voices into signals, and a ringer of some type to make your party aware you’re calling. But beyond that, virtually everything has changed. Check out this infographic showing, from a scientific and technical perspective, what happened then and what happens now, every time you make a call.

(Click and zoom to enlarge)

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