“Quindar-tones” are the twinned beeps best known from the Apollo and Space Shuttle missions. They’re named for Quindar Electronics, Inc., which produced the related equipment.
50: The difference in Hz between the two tones
2,525 Hz: The higher of the two pitches, in hertz
250ms: The length, in milliseconds, of each of the two tones, individually
I thought to do this entry because someone at some point searched for the word “Quindar” on disquiet.com. There was no entry, so I figured I’d make a brief one, and the Sound Ledger seemed like a good format in which to do so.
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¹Footnotes
Quindar-tones resources: [wikipedia.org](https://en.wikipedia.org/wiki/Quindar_tones), [nasa.gov](https://www.hq.nasa.gov/alsj/quindar.html), [archive.org](https://web.archive.org/web/20130929033302/http://apollo17.ehartwell.com/MissionTranscriptCollection.htm#Quindar).