Talk:Quindar tones

As part of the discussion about the selection of audio tones, I vaguely remember there being certain choices for audio frequencies that would disable or otherwise interfere with the operation of long-distance phone repeaters that were in use at that time. My guess is that the selection of the frequencies for the Quindar Tones would have taken this into consideration, but I can't find any information that would validate this assumption. Maybe somebody else knows more.

Gary Neff used to have some nice .wav files on his site that would generate the two tones, but that site has since disappeared. I'd love to be able to link to those audio files.

I saw some discussion on various sites that I googled about the name Quindar. There isn't strong evidence that this name came from the company that built the equipment, but it's a pretty good guess. Since the name is so unique, it would be great to include a solid reference for this if it exists.

- todd


 * For more about the "audio frequencies that would disable or otherwise interfere with the operation of long-distance phone repeaters" see Blue box et al. Tonywalton | Talk 09:45, 8 April 2006 (UTC)

I found documentation of the source of the name in the Mission Transcript Collection and added it to the article with reference. Todd's assumption was correct. - Mark Dixon (talk) 01:02, 18 August 2009 (UTC)

More references?
This is a very interesting article that answers a lot of questions I had. Unfortunately its only reference is now kaput, going to a GoDaddy domain advertisement. Pmcgrane (talk) 07:33, 30 May 2013 (UTC)

Justification for 08 Jul 2013 updates
A lot of great work has been done on this page since I first wrote it in 2006. A quick search on Google for the word &quot;Quindar&quot; shows that this article has been cited for reasons as far ranging as disproving Apollo moon landing conspiracies all the way to one fine fellow who was glad to see that the government could save money by sharing when necessary. :-)

After reviewing the edits that have been made in the last few years, I reverted a few items to their semi-original state (original + some modifications that followed). I thought that it would be useful to justify these modifications for future reference:

1. I updated the links to The Mission Transcript Collection, or at least to what I believe to the page that was previously referenced but no longer worked. I must admit that I am slightly uncomfortable relying so heavily on a single reference, so it could be helpful to beef up the sources for the article.

2. This article is primarily about the technology of Quindar tones and their application, yet some of the edits went beyond the main interest of the article to discuss the need for PTT functionality between Houston and the transmitting stations. While the presence of white noise and cross-talk on the phone lines between Houston and the transmitting stations is interesting, it's not really relevant to this article. The article as originally written assumes that PTT was necessary and describes how remote PTT was accomplished using this technology. I removed any reference to the need for PTT and reinserted the section on using in-band signaling as a means for reducing cost. I also provided a reference to this as a driving force behind Quindar tones by citing The Mission Transcript Collection. As far as I can tell, The Mission Transcription Collection does not cite this article (direct circular reference) nor does it appear to cite any sources influenced by this article (indirect circular reference) so I believe that it's a good source.

Should it become necessary to include a discussion on the need for PTT, I suggest a separate article or perhaps a separate section at the bottom of this article which describes the need for PTT so as to not confuse PTT with Quindar (one of many possible implementations of PTT). There are other reasons for PTT than just white noise and cross-talk on the dedicated telephone lines. The Mission Transcript Collection states that there was a handover process between tracking stations which implies that PTT was used in other ways as well. Perhaps PTT was disabled to prevent transmission station interference or to allow for service repair while offline or just as a way of being "green". Whatever the reason(s), this has nothing to do with Qunidar and everything to do with PTT.

3. I relocated the discussion about Quindar tones no longer being needed in modern space communication systems from the section on Common Misconceptions to the section on the Need for Quindar Tones. It seemed more appropriate there. As part of that move, I removed any referenced to the USB or full-duplex voice transmissions because they didn't appear to be relevant to the discussion on the in-band nature of Quindar tone signaling.

4. I heavily reworked the section on cell phones and FM subcarriers because it appears to confuse the issue. While I believe that the comment the USB and audio subcarriers being full-duplex is correct, the paragraph may likely leave the reader confused as to the nature of the communications being "like a cell phone" where each person can hear the other all of the time. Even if the audio subcarrier was present all of the time in the USB (which it may not have been if you believe the Wikipedia article on USB that says that NASA turned off the audio subcarrier when astronauts were sleeping), that does not mean that the audio subcarrier was modulated. In other words, Houston couldn't hear the astronauts unless they keyed using PTT or VOX. So while the nature of the uplink/downlink was full-duplex (two different frequencies according to that same USB article), the nature of the control of the audio transmission was half-duplex in that it could only be controlled from one side. So I replaced that section with a discussion on the full-duplex nature of the audio channel and how it could support simultaneous communication. I believe that this communicates what the original author wanted to say without leaving open alternative interpretations by the reader. — Preceding unsigned comment added by Toddbu (talk • contribs) 06:32, 9 July 2013 (UTC)

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To me, this line, "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." does a far better job of explaining "The Need for Quindar Tones" than the entire section of that name, and I think it (or a suitably edited copy of it) really should be the introductory line of that section. That one line summarizes the answer to that question perfectly, while the reference to "keying the PTT" in that section as it now stands doesn't clearly provide the fact crucial to understanding why they were needed: that the transmitters are (were) remotely situated (at the tracking stations), and needed to be turned on and off somehow. (Knowing that, everything else in that section suddenly makes sense, where before reading all the way down to that line, I was still scratching my head thinking "but what do they DO?") -- Tallinu 97.93.57.252 (talk) 04:06, 20 October 2016 (UTC)


 * OK, tried to explain better in the section "why the tones are needed". See what you think.  LouScheffer (talk) 17:10, 20 October 2016 (UTC)