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The story behind the "Beep"
Those fortunate enough to listen to any of the actual mission control air-to-ground audiotapes will notice a high-pitched beep emitted before and after every air-to-ground communication between mission control and the astronauts. This sound is called a Quindar tone. Steve Schindler, an engineer with voice systems engineering at NASA’s Kennedy Space Center, offers the following history of its origins.
"Quindar tones, named after the manufacturer of the tone generation and detection equipment, are actually used to turn on and off, or "key," the remote transmitters at the various tracking stations (Merritt Island Launch Area–now Kennedy Space Center, Bermuda, Australia, etc.) that were used to communicate with the Mercury through Apollo spacecraft and, in some cases, are still used with the Space Shuttle. A one-half second tone burst is generated when someone in a control room depresses the push-to-talk (PTT) button of their headset. The decoder at the remote transmitter site detects this tone and keys the transmitter. When the PTT button is released a different frequency tone burst is generated. When the decoder detects this second tone, it unkeys the transmitter. Because the telephone lines between the control rooms and the remote transmitters were originally designed to carry only voice frequencies, the tones had to be in the voice frequency range ("in-band signaling") and thus audible to humans. The tone signaling could have been done on a separate phone line, but to keep costs down, signaling and audio were done on the same line."
"Although it usually worked well, there were a couple of peculiarities with this system. If the transmitter was keyed and the telephone line connection broken, the transmitter would never get the tone to turn off. To prevent this there was a "transmitter on" light at each remote site that would come on when the transmitter was keyed. Someone was supposed to monitor the circuit and if the audio dropped, but the "transmitter on" light was still on, they would have to manually unkey the transmitter. Also, just before communications was handed over to a new tracking station, the key-unkey tone pair was sent 10 times to ensure that everything was functioning correctly. This was done before the audio was patched to the tracking station’s line so it wasn’t heard in the control room or on NASA Select audio.
The Quindar system was actually built from a piece of equipment that was used to put multiple teletype circuits on a single phone line by means of frequency domain multiplexing. Because replacement parts are no longer available, an "out-of-band signaling" system was installed in 1998 for the transmitters located in the U.S. This system uses a continuous tone that is below the normal audio frequency range. When the tone is present, the transmitters are keyed. When the tone is not present, the transmitters are unkeyed. It worked fine, but the Astronaut Office complained about the lack of tones which everyone had become accustomed to as an alert that a transmission was about to start. So, the Quindar tone generator, which was still installed in case it was necessary to key the transmitters at an overseas site, was re-enabled.
Mercury Through Apollo
The Mission Transcript Collection includes scanned transcripts from recorded air-to-ground transmissions and from tapes recording the words of the astronauts while onboard the Mercury through Apollo missions. The collection contains 80 transcripts (approximately 45,000 pages of text). Some of the transcripts include a detailed explanation of the contents.
Originally posted by decisively
reply to post by prevenge
I will use my spelling and grammar and punctuation checker for you to help you understand even though this takes a lot of time for me to do.
I have a disability and writing is very difficult for me. For many of us we were encouraged to write phonetically and not worry about spelling so that we could actually write something otherwise we get confuse like trying to understand if we want to use "f" or "ph" to make the f sound. So most of the time I just use f and don't go back to look at where the computer shows maybe I should change the spelling or make a capital or put a comma which I almost never do. This way I can write at least something.
When we write for special school or write a paper or do a project we do all of the correcting like I am trying to do here and it takes a very long time so most of the time when I am just writing for a forum like this I will not bother to do that. It is sort of a wasted time.
I kind of know what cointelpro is from reading about the Black Panthers and those things. You are sort of funny to recommend me as one of those people. I think as you read more of my writing and ideas you will see I cannot be that type of person because I am very convinced Apollo is phony and my ideas are very true. Anybody that knows about star sightings knows that Michael Collins cannot sight and mark a star correctly if he cannot put the star in the correct context of the constellation.
Another thing is that even though I have a disability in this one area I am considered one of the best in the United States and maybe even the world. But I know this is not everything and I have limitations.
LAst thing to say about cointelpro is that I believe Jarrah and Patrick are very great and important people writing about Apollo and probably have the correct general ideas that show Apollo phony and no cointelpro would link Jarrah and Patrick here. IF they would do anything they would be working against them as they more than any other Apollo workers seem to be pushing for the truth and helping the whole world see it.
so if apollo is fony it must be so that a lot of the astronaut part is taped to avoid mistakes and the mission control part is live everything else is not really an issue for this type of thing we are considering
Originally posted by Pauligirl
I remember the beeps, but didn’t know what they were for. Now I know.
The story behind the "Beep"
" The tone signaling could have been done on a separate phone line, but to keep costs down, signaling and audio were done on the same line. "
"But no one, not Armstrong and Aldrin nor anyone in mission control, knew just where Eagle was. The location would be a helpful, though not essential, piece of information for this computer to have during tomorrow's rendezvous. It fell to Collins to try to find the LM on the surface, using the command modules 28 power sextant."