One element of the
Apollo missions which has subconsciously buried itself into the public mind is NASA's 'roger beep', the chirp which dotted transmissions to and from the moon. It was a comforting sound, the kind of sound a man could rely on; it meant that somebody was in charge, somebody was in control.
Sputnik had announced its presence with a beep of its own, but it wasn't a friendly beep, not at all. It was an eerie beep, an ominous beep, a beep of subversive intent, a
Communist tone. It was an emotionless beep, staccato, distantly mirroring the rat-tat-tat of the
PPSh submachine-gun; unstoppable, unemotional, remorselessly set on a deranged course of world domination that could only end in disaster, in the fatal weakening of the human spirit just when takeover by alien beings seemed most likely. It was not a woman place to be.
NASA's beep - formally known as Quindar tones, after the manufacturer of NASA's telemetry equipment - spelt freedom, and by the time Mission Control told Tranquility Base that they were patching through a special message from Richard Nixon, the roger beep had seared itself across the synapses of a generation, burned in with the white heat of technology. Laika had escaped the corrupt regime that sent her to die; but her bark lived on.
NASA used the Quindar tones as audio 'control codes' for their transmitters. The beeps are not the exclusive property of NASA, though; they are standard circuits in many transceivers and CB sets, and are commonly used in situations where the conversation is likely to be transcribed later, or in areas of poor reception, or just to make a CB radio sound 'official'. It saves having to say 'roger' all the time, as well, and can also irritate people if used excessively.
Being the biggest and most painstaking kids on the block NASA used two beeps; the first denoted the beginning of transmission and ran at a frequency of 2525hz, whilst the second came at the end and was 2475hz. Both lasted for 250 thousands of a second.
Selected source
Quindar sold up in 1975 and are now known as QEI. Furthermore:
http://www.hq.nasa.gov/office/pao/History/alsj/quindar.html
http://www.ninfinger.org/~sven/models/vault/spaceflight.pdf
http://www.qeiinc.com/about_us/history.html