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Which common electronic device was previously remotely controlled by ultrasound?

  Zenith old display with the first wireless TV remote control

Answer: Television

Let everyone who came of age in the early days of television talk about their family's first TV, and You are required to hear stories about children being sent through the living room to change the channel using the controls on the front of the unit. At that time, there were no remote controls to talk about, and if you wanted to see another of the few stations in your area, you had to get up and change the channel on the device itself.

All this has changed when the first, although unpopular, remote control came with the television. The first television remote control was released in 1

950 and was, for a modern consumer unthinkable, connected directly to the TV via a cable that snaked through the living room to the viewer's chair. Despite the increased comfort, few people wanted a semipermanent cable installation in their living room. Zenith, the same television company responsible for introducing the aforementioned wired remote controls, was working on a wireless version in the first half of the 1950s. Radio-controlled remote controls were proposed, but they were never used, as radio receivers from the 1950s were of poor quality. At the time, it was simply not practical or efficient to use radio frequencies for the remote control.

If not radio waves, what then? If you have opted for infrared, you are well acquainted with the mechanics of modern remote controls, but can not guess how the first wireless remote works. Modern remote controls use infrared pulses to control televisions and peripherals, but infrared was first used in consumer products in the early 1980s. Bluetooth remotes as a standard feature would be even thirty years away.

The first remote control for wireless TVs used ultrasound frequencies instead to control the TV. The bulky remote contained a series of bars that were hit with a loud click of the buttons (hence the term "clicker" for remote controls) and fired ultrasonic waves in front of the remote. The design of ultrasound remote controls has been refined by the introduction of more compact electronics. Later models contained piezoelectric crystals that were configured in some sort of electronic tuning fork device and output certain frequencies for various functions (eg, changing the channel up or down, adjusting the volume, and turning it on and off). In the receiver was a microphone that recorded the frequencies and made the settings on the TV.

The design was not without defects. Some people with very sensitive high frequency hearing could hear the remote (much to their chagrin), dogs were perceived as less well by the devices, and natural sounds from the environment could cause the receiver to malfunction.

Ultrasonic remote controls were eventually discontinued in favor of infrared remote controls that produced no sound and were radically less susceptible to environmental noise. Although wireless remote controls were impractical in the 1950s, manufacturers of high-end remote controls returned decades later with great success. Nowadays most of the remote control functions in household electronics are carried out via infrared, radio frequency or a combination of the two.

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