Make: Volume 78

and his wife 100 years before our visit. We were

accompanied by representatives from National

Geographic, the Smithsonian Institution, and Bell

Laboratories. Our purpose was to recognize the

first time Bell transmitted the human voice over

a beam of sunlight by a photophone exactly a

century earlier.

To celebrate the photophone centennial, I built

a simple version of the device with which we sent

our voices across the site over beams of sunlight.

We then unwound a 100-foot length of optical

fiber to which I had attached a red LED at each

end, and we talked to one another with the red

LEDs serving as both emitters and detectors of

voice-modulat ...