Geek Trivia

What Common Electronic Device Was Once Remote Controlled By Ultrasound?

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Answer: Televisions

Get anyone who came of age in the early days of television talking about their family’s first television set and you’re bound to hear stories about children sent scurrying across the living room to change the channel using the controls on the front of the set. In the early days of television there were no remotes to speak of and if you wanted to watch another of the handful of stations available in your area you had to get up and change the channel on the set itself.

All that changed when the first, albeit unpopular, television remote came along. The first television remote was released in 1950 and was, unimaginable to a modern consumer, tethered directly to the television set by a cable that snaked across the living room to the viewer’s chair. Despite the increase in convenience very few people wanted a semi-permanent cable installation in their living room. Zenith, the same television company responsible for introducing the wired remotes, spent the first half of the 1950s working on a wireless version. Radio-based remotes were proposed but ultimately never saw use outside of the lab thanks to the poor quality of 1950s era radio receivers–it simply wasn’t practical or efficient to use radio frequencies for remote control at the time.

If not radio waves, what then? If you guessed infrared, you’d be well informed about the mechanics of modern remotes but off base in guessing how the first wireless remote functioned. Modern remote controls use infrared pulses to control televisions and peripheral equipment but infrared didn’t start appearing in consumer products until the early 1980s.

The first television remote control used ultrasonic frequencies to control the television set. The bulky remote housed a series of tubes that were struck by the buttons with a loud click (thus the term “clicker” to refer to remote controls) and fired ultrasonic waves out the front of the remote. The design of ultrasonic remotes was refined with the introduction of more compact electronics. Later models contained piezoelectric crystals, configured in a sort of electronic tuning-fork-like apparatus, that issued specific frequencies for various functions (like changing the channel up and down or adjusting the volume). The receiver housed a microphone that picked up on the frequencies and made the adjustments to the television set.

The design was not without shortcomings. Some people could hear the frequencies (much to their annoyance), dogs were reported to be less than fond of the devices, and natural sounds from the environment could cause the receiver to malfunction.

Ultrasonic remotes were eventually phased out in favor of infrared remotes which generated no sound and were radically less susceptible to environmental interference. Although radio-frequency based remotes were impractical in the 1950s, high-end remote manufactures would return to the concept decades later with much success. Today the majority of remote control functions in domestic electronics are handled by a infrared, radio frequency, or a combination of the two.