semaphore flags

Although Marconi didn’t realize it at the time, the hill separating him from his brother did, in fact, impede radio waves. But the hill blocked only straight-line waves. Other waves emanated upward and ricocheted off the ionosphere back to earth. Thus radio transmissions go far, far beyond the horizon. Marconi didn’t understand the phenomenon at the time, but he saw immediate business potential for establishing communication with ships at sea. Previously, ships had been limited to semaphore flags and flashing mirrors, which of course meant that ships were incommunicado with anything over the horizon. Marconi made a fortune.

Television After radio, television was a logical next step in media technology. There was agreement that television signals could be transmitted on the airwaves somewhat like radio. The trick, though, was to capture movement visually for transmission. Physicists and engineers at major university research labs toyed for years to create “radio with pictures,” as early television was called.

But it was a south Idaho farm boy, Philo Farnsworth, who at age 13 came up with a concept that led to his invention of television. Plowing the fields, back and forth in furrows, the young Farnsworth had an epiphany. Applying what he knew about electricity from science magazines and his own tinkering, he envisioned a camera-like device that would pick up light reflected off a scene, with the image being sent radio- like to a receiver that would convert the varying degrees of light in the image and zap them one at a time across stacked horizontal lines on a screen, back and forth so rapidly that the image on the screen would appear to the human eye as real as a photograph. then, another electron would be zapped across the screen in, so to speak, “furrows,” to replace the first image with images coming so quickly that the eye would perceive them as motion. Farnsworth called his device an image dissector, which literally was what it did.

Like motion picture technology invented 40 years earlier, television froze movements

at fraction-of-a-second intervals and played them in fast sequence to create an illusion that, like movies, capitalized on the persistence of vision phenomenon. Unlike movies, Farnsworth did not do this with photographic technology, as television uses electronics rather than chemicals. Also, unlike movie technology, images recorded by a television camera are transmitted instantly to a receiving device, called a picture tube, or to a recording device for later transmission.

Although Farnsworth had sent the first television picture from one room in his San Francisco apartment to another in 1927, the complexities of television technology delayed its immediate development—so did national survival while Americans focused on winning World War II. By the 1950s, however, a radio-like delivery infrastructure for television was in place.