Quindar Tones
Your useless but fascinating cultural minutiae trivia for the week...
You know them as "NASA beeps." They're the sound you heard at the beginning and end of each transmission between Houston control and manned spacecraft during the Space Program. Here's a sample:
Pretty much everyone in the world knows what the sound is and can instantly identify it. But do you know what it's for?
One common misconception is that it's an encoder signal, similar to what military radios use for real-time encryption of battlefield transmissions. Those of you who served in ground forces in the '70s and '80s know it as a "KY" encryption, short for KY-57 Speech Encryption Device. It was a bulky, heavy add-on for a PRC-77 field radio. It sometimes worked and mostly didn't. But it was effing heavy -- just what a grunt needs: more dead weight.
But that's not what a Quindar tone is for.
The Quindar tone is a perfect sine wave, the "outro" tone being 50 cycles slower than the "intro" tone. The tones told the transmitters for the global communications system to turn themselves on and off at the beginning and end of each transmission. It was a purely economic solution: running separate lines for that purpose, the traditional means at the time, would have been prohibitively expensive for a worldwide network the likes of which NASA needed to stay in constant communication with a capsule in orbit. So a company named Quindar came up with the ingenious analog solution of using sound tones which the human voice couldn't produce but which the transmitters would recognize as on/off signals, so it could all be done over a single channel.
Wikipedia article on Quindar tones.
You know them as "NASA beeps." They're the sound you heard at the beginning and end of each transmission between Houston control and manned spacecraft during the Space Program. Here's a sample:
Pretty much everyone in the world knows what the sound is and can instantly identify it. But do you know what it's for?
One common misconception is that it's an encoder signal, similar to what military radios use for real-time encryption of battlefield transmissions. Those of you who served in ground forces in the '70s and '80s know it as a "KY" encryption, short for KY-57 Speech Encryption Device. It was a bulky, heavy add-on for a PRC-77 field radio. It sometimes worked and mostly didn't. But it was effing heavy -- just what a grunt needs: more dead weight.
But that's not what a Quindar tone is for.
The Quindar tone is a perfect sine wave, the "outro" tone being 50 cycles slower than the "intro" tone. The tones told the transmitters for the global communications system to turn themselves on and off at the beginning and end of each transmission. It was a purely economic solution: running separate lines for that purpose, the traditional means at the time, would have been prohibitively expensive for a worldwide network the likes of which NASA needed to stay in constant communication with a capsule in orbit. So a company named Quindar came up with the ingenious analog solution of using sound tones which the human voice couldn't produce but which the transmitters would recognize as on/off signals, so it could all be done over a single channel.
Wikipedia article on Quindar tones.
posted by Jar(egg)head at 14:17
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