Alexander Graham Bell is widely credited with inventing the telephone, in 1876. It’s not entirely undisputed: Elisha Gray, Antonio Meucci, and Johann Philipp Reis each also have a decent claim as well, but Bell’s name is the one we most associate with the invention that lets us send a voice through a wire.
So what about sending a voice without a wire? Besides the obvious method of just yelling, people tend to think of wireless voice transmissions as being by radio. Radio is ubiquitous today – with AM and FM broadcasts and cell phones and satellite dishes. But the first wireless telephone predates the first radio system by a decade and a half. Its technological descendants are just as important as radio, and it was created by an inventor you might have heard of.
That inventor is Alexander Graham Bell.
Alexander Graham Bell: Wireless Pioneer
On April 1st, 1880, just as Bell’s telephone was starting to take off with customers, Bell himself had a new invention to test. Fellow inventor Charles Sumner Tainter, standing on the roof of the Franklin School in Washington, DC, spoke into a thin, flexible mirror. As the sound waves of his voice hit the mirror, its shape changed ever so slightly, moving a glint of sunlight back and forth.
About 700 feet away, at Bell’s laboratory, that sunlight hit a parabolic mirror, focusing and amplifying the moving sunbeam onto a curious new device. Bell had learned of a recent discovery that the element Selenium had a varying electrical resistance depending on the amount of light shining on it. By hooking up a battery and a telephone receiver to a Selenium cell at the heart of the mirror, Bell would be able to convert the beam of sunlight back into to sound.
This wasn’t the very first test of the device – an earlier version using a metallic grating instead of a mirror had been used within the confines of the laboratory – but it was by far the longest distance test. Tainter requested that Bell wave his hat out the laboratory window; Bell happily complied. The signal was clear as daylight.
This device, the “photophone”, was the first true wireless telephone. Bell was even more proud of his new invention than his famous telephone. He even suggested naming his second daughter after the invention, which his wife thankfully rejected.
Marian Bell, who narrowly avoided being named “Photophone”
The public was not nearly as enthusiastic about the photophone, however. It relied on clear skies and precisely aligned equipment, and even then was limited in range by the diffusion of sunlight in the air. The photophone still hadn’t yet caught on when Guglielmo Marconi first demonstrated radio communications in 1895, further reducing its advantages.
Still, the photophone wasn’t entirely dead. In World War One and Two, it saw some use as a more secure alternative to radio, since an eavesdropper would have to stand directly in the transmission path to have a hope of decoding the signal.
But the true heyday of light-based telephone communications would finally come a century after its invention, in the 1970s and 1980s, when fiber optic cables allowed light to travel across hundreds or thousands of miles, with much higher bandwidth than radio thanks to the shorter wavelength of visible light. The first transatlantic fiber-optic cable, TAT-8, started operating in 1988. Appropriately, it was designed by Bell Labs.
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