Apollo Comms Part 27: Quindar Tones Microphone Hack

Nothing is more emblematic of the Apollo communications than the Quindar tones, which you hear at the beginning and end of each transmission. In this episode, we hack a cheap commercial microphone to bring it up to NASA standards by adding the tones. After explaining what they do, of course.
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[@CuriousMarc]

I just posted my lab book notes with explanations and the schematics on my website: www.curiousmarc.com/space/quindar-tone-generator . Have a go at it, and let me know if you ever make a proper PCB for this project!

[@frankbrockler]

Quindar tones still work to this day. Whenever I hear one, it instantly triggers "7 year old boy sitting on the living room floor 2 feet from the TV watching astronauts on the moon" mode in my brain. Thanks for the trip down memory lane, Marc.

[@sethtaylor5938]

Quindar aka QEI is an Electronic Manufacturing firm in Springfield NJ that manufactured analog DTMF and FSK hardware back in the 70's and 80's. They are still in business.

[@brocktechnology]

Thankyou, the only thing mark left out was where the name came from.

[@greenconscious210]

Darn it. Now I want a Quintar tones plugin for Zoom PTT mode

[@624Dudley]

Ooh 😮, that would be useful!!

[@MikeF1189]

That would just piss my teammates off. I have to have it!

[@rootvalley2]

huh didn’t even know zoom had ptt neat

[@user2C47]

Or as an external program, so it would be usable by all platforms.

[@greenconscious210]

@@rootvalley2 when your MIC is muted you can use the space bar as a PTT key

[@Yrouel86]

Not only the Quindar tones were used for Shuttle but they are still in use today with Crew Dragon

[@stevewalston7089]

Seems like a far better method than saying "roger" or "over".

[@Yrouel86]

@@stevewalston7089 Indeed plus astronauts are generally already familiar with it so it didn’t make sense to change. It’s one of those things that you keep because it actually works and not because of inertia and resistance to change

[@muadeeb]

​@@stevewalston7089 Huh? What?Who ?

[@stevewalston7089]

@@muadeeb Maybe the Quindar tones?!

[@Gracana]

@@muadeeb What's your vector, Victor?

[@richardmattocks]

I had no idea these beeps had an official name and also, until you pointed it out I hadn’t spotted that the start and end transmission tones were different, and the reasons for them is so obvious once I thought about it. Also, I appreciate you using actual electronics to generate the tones. You absolutely nail the tones in every way that any digital version just couldn’t and would have been ever so slightly “off” (it’s a real niggle of mine when I hear recreations of oldschool sounds made via digital generation). It never quite hits the mark IMHO, so total respect to you sir! Loving your channel. Great work!

[@rogervanbommel1086]

I mean, gnuradio can do exact FSK, so I can probably get it exactly the same in software in THIS CASE

[@paulmorley1225]

Can you tell me the word origin of niggle?

[@zh84]

I was used to hearing those beeps and never knew what they were. Thank you for the excellent explanation!

[@comput3rman77]

They were named after the manufacturer Quindar Electronics.

[@MatthijsvanDuin]

It's trivial to perfectly recreate these digitally using a microcontroller and an audio DAC

[@thes764]

Always learn something new on this channel. This time: NASA "roger beeps" are called "Quindar Tones" and really are in-channel signalling for the ground station networks PTT. Excellent video Marc & crew!

[@bblod4896]

Roger beeps are still popular with the CB crowd.

[@TimoNoko]

These two tones are already ingrained to our psyche. I have push button which turns a remote device on or off. I wanted immediate feedback what it is doing. So I made these Moon Men Microphone Sounds from a small speaker, without knowing what they are called.

[@TheM4man]

Spending my saturday night watching 20 minutes about beeping sounds and im not even sad! This is amazing, thank you for your service for humanity!

[@AndyFletcherX31]

Back in the 1980s I used to design equipment which used a continuous 2970Hz tone to key transmitters. Because the tones were present whenever someone was speaking they had to be filtered out of the audio stream. There is a problem with Qiundar keyon and keyoff tone system design in that if a tone burst is missed by the transmitter it will stay stuck in whatever mode it was in until the next tone burst comes along. Considering the worldwide routing of the Apollo audio streams I would expect occasional dropouts which could if you were unlucky would lose the Quindar keytones.

[@W6EL]

I had the same thought. But it could be solved with a VOX circuit AND’d with a timer. If no tone and no audio and we’re past the timeout, then we switch off anyway. Of course most likely this would be noticed and someone would just have to click the mic to get it back I assume.

[@clayp6415]

If only NASA had saved all this stuff and preserved it all in one place. It would be amazing to go to a museum and see all this stuff working and integrated together. Also I just wanted to say, what you are doing is amazing.

[@christopherwhull]

The Apollo Applications (Skylab) and shuttle programs used much of the same stuff through about 1973-1998. Ground equipment would have been cheap to file away but the spending and focus was getting the remaining very large artifacts, flight ready and ground articles to museums across the nation while the program was still fresh in the mind of the us tax payers. The Tracking and Data Relay Satellite System also reworked the direct to ground, VHF, HF electronics on the spacecraft and was the sole standard communications path by 1998. The interesting item will be the implementation of 5G chipsets and software defined radios into future spacecraft. With communications companies such starlink putting 25,000 bent pipe and packet switched solutions under long term space test, bespoke voice and data solutions are a bit archaic outside of VHF and HF backups to backups. A UHF, HF, VHF and Packet Radio radio set is good to 250,000feet Once on orbit Manned spacecraft will just be temporary space based node in meshes of communications services. The weight of comms gear on the Apollo spacecraft in total must have been non trivial. Comms gear to orbit of Mars or the surface of mars will be dominated by high gain for data delivery, the rest of gear more than likely will be Starlink components with in space histories of more than a decade. The economy of the scale of developing what would be bespoke between NASA and Boeing is just Lego components of SpaceX ecosystem is the amazing part of the story.

[@624Dudley]

Thanks Marc! All these years I thought the tones were simply audio cues, used in the way you mentioned. I didn’t know about their triggering function. This channel is awesome! 👍👍

[@moo3993]

I know you're catching up on footage you've recorded, and getting it into a finished video. I am loving seeing your videos more often Marc! Always love and appreciate what you do for everyone!

[@benjaminhanke79]

05:20 "Radio teletype transmitter" I'm looking forward to see a video of this.

[@rsmrsm2000]

It was exactly what I expected. Thank you very much for this survey. It had a bonus: simulating the quinder tone in current circuits. You guys are amazing, keeping the magic of man going to the moon alive.

[@reneschmitz4845]

You have to do this with an original Apollo era Headset. Fran Blanche had showed one on her channel. The sonic signature of these makes it sound like Apollo instantly.

[@johnk7302]

haha stir the oxygen tanks that's a good one man.

[@JD_Viddy]

I remember using a XR2206 back in the mid 1970's when I built a controller for a 2m RTTY repeater above Los Angeles. In normal operation it would convert the incoming audio to digital using a common circuit using a couple of toroids. That would then go into a UART to be converted to 5 parallel bits and then back into the UART for regeneration and then on to the XR2206 to go back to audio. For testing you could apply a PL tone and it would just route audio from the receiver to the transmitter. Good times.

[@soulrobotics]

Fantastic Marc! (add french pronunciation! lol. clever output with that mosfet!. so this video make my day! thanks! I am not the only one that wants to visit that basement!!!Man, that is a living museum!

[@thomasgrunwald9065]

Marc.... Kudos to you and your team for all the amazing restoration of this sometimes maddening original Apollo comms equipment!! The trigger for my comment is the elite 2 Circuit Design Test System that you breadboarded the Quindar circuitry on. I worked on one of them for over 10 years, mocking up the circuit designs that the engineer I worked with came up with. I just finished a 42-year career with the FAA, specializing in Air Traffic Control Radar, then Physical Security. I believe that the Moon Race is what sparked my early-teens interest in electronics, leading to my career. Again, congratulations to you and your team!!!

[@tbp-channel8870]

Hi Marc, XR2206 and Baudot are warm reminders of my first ham-experiments with an old teletyper and a ZX81, my first computer. The Interface (and the ZX81) still exists. Always a pleasure to watch your videos. Great team also, absolutely.

[@surplushunter]

Marc, an excellent video!! I remember hearing the Quindar tones when I was a little boy and wondering what they were for, I investigated years later and found out. Way to go!!!

[@garylucas6511]

My initial education was Broadcast Comms and Electronic Theory. Brings back memories fooling around the lab at college. And also being a long time space nut, I LOVE this channel!

[@sarhtaq]

I remember back in the late 1970'ies early 80'ies, the CB community around here simply called them "Apollo beeps" when we used them on our radioes :)

[@GordonjSmith1]

Every time I watch, my world gets larger! My thanks.

[@karlmadsen3179]

This is so wonderfully geeky, it is irresistible to me.

[@alexpinkerton7459]

Every Teams meeting demands the use of a "Quindar Tones" intercom mic. It will make you sound like you're talking to your team from another planet, and discourage others from asking you any questions - which is a win win!

[@rhyoliteaquacade]

No No, No, Don't stir the 02 tanks!!! Thanks came here for the Quindar tones. Think I will stay and go down the retro-tech rabbit hole you created!

[@yuglesstube]

So very interesting! I had wondered why, and now, years later, i know.

[@ntsecrets]

I had no idea what the beeps were called and that they were at different frequencies. I actually thought they were just made periodically to show you were receiving, but now I know! Thanks!

[@SubTroppo]

I wonder how many bleeping meetings were required to decide on the bleeps back it the day, or whether an engineer just said, "...here they are".

[@LostAgain1970]

Marc managed to find "Mr Fancy pants" so maybe he can also find the bleep engineers? That would be cool!

[@garylucas6511]

With 400,000+ folks working on the program, I don’t doubt they had a dedicated engineer for the beeps.

[@SubTroppo]

@@garylucas6511 An engineer for the higher tone and one for the lower tone? ...and a tonal manager to keep the peace in the inevitable turf-war.

[@mikus4242]

Don’t forget this NASA. You would have the higher tone contractor engineer and manager….. AND the lower tone contractor and manager. PLUS the safety NASA engineer and safety manager + their contractors.

[@benjaminhanke79]

@@LostAgain1970 That Person would probably be in his 90s but everything is possible.

[@thickdickwad7736]

Excellent video! Thanks for sharing 😊

[@AlexanderGibbonsAudio]

I'm seeing a lot of TekTronix scopes in the images you shared, lovely to see them in play :)

[@ReneSchickbauer]

The XR2206 is a good thing for one of my future projects. I was currently looking into how to generate sine signals, then i watched this video. This chip will make my project so much easier, now that i know it exists!

[@ComputerHistoryArchivesProject]

Very informative, and very cool! I did not know about Quindar tones. Thanks for this explanation, great technical equipment too!

[@Derrick6162]

I have a faded memory of my grandfather sitting in front of an old black and white console tv watching the landing as I stirred about.

[@haom95]

Awesome!!! I Didn't find that kind of project in magazines such as Popular Electronics, or Electronics Now. It's very cool because you use a lot of electronics, that I used to use in my career as Electronics Engineer so long ago Great Project !!!

[@Carlou_]

je vote pour que ce soit installé dans tous les supermarchés, j'adore! :) Merci encore pour toutes ces vidéos super intéressantes!

[@dhpbear2]

Those tones bring to mind "The Jetsons" (!) I also heard it on radio call-in shows back in the early 60s. They were sent at regular intervals during a call.

[@eurisko84]

Brilliant as always. 10 minutes to learn about something I didnt know I needed to know! This is getting shared far and wide (already annoyed the wife about my new found knowledge lol)

[@KeritechElectronics]

A lightweight, quirky and cool piece of tech :)

[@PeopleAlreadyDidThis]

When I heard your first generated tone following the original, I thought, “No, that’s not it. It’s flat.” Then you explained the pitch/frequency difference between the two. So now neither of us are crazy.

[@RowanHawkins]

I always thought they were a standard RogerBeep. Some amature repeaters use a tone for exactly the same purpose. Learned yet another something new.

[@Zadster]

Ahh the good old "roger bleep". Many fond memories of the CB radio days here in the early 1980s, and a young me, making roger bleep circuits for me and my friends, with 555 timers, a relay and a whaterer other components this particular 11-year-old had to hand or could obtain. Later on, with the addition of a 4017 and a bunch of preset pots, it was possible to play a little tune. I don't think I ever appreciated they were 2 different tones!

[@bborkzilla]

Good old Exar 2206. Brings me back to when I was messing around with packet radio and HF RTTY.

[@PeterGagen]

What a nice little projecct - well done and thanks. I thnk my radio ham transmissions will be definatly be getting an improvment. 🙂

[@MonkeyUnit]

Ohhh! My favorite game. Pause at 2:33. What instruments can you identify? At the top I see a Tektronix RM 503 oscilloscope. Just below that I see a Dymec 2401C voltmeter/counter. Further down at chin level I see an HP 5245L counter. I need help identifying the HP instrument with the analog meter at forehead level.

[@CuriousMarc]

That last instrument would be an HP 413AR null voltmeter. Pretty rare to see an “AR”, the rack version of it.

[@AntoninKral]

Niiice, I think I am going to build this one as an USB soundcard for my Zoom/Meet/Teams calls ...

[@74HC138]

Our local ham radio repeaters have a 'courtesy tone' which sounds when you drop carrier, so the others you're talking to know when they can key up, just a short beep. Sounds like you're talking to the moon to the uninitiated :-)

[@paddle_shift]

Crazy, but the "bad" mic sounded better in the video than the "good" one! 😂

[@johnstevens2163]

I think I have just found my build/modify project. I should have an FSK encoder decoder as I ran a teletype link over HF radio from James Cook University in Australia to the University of the South Pacific. If not I will go with the ‘cheap’ solution. One comment - the tones don’t sound like I remember them. I had 2 references 1. From the broadcast TV in Australia and 2. From one of the network control centres on the way to and from Honey suckle. Of course it could be my antique hearing or KZbin mangling the tones!

[@AndyGoth111]

9:00 Ohh that's so dark!

[@marvintpandroid2213]

The term quindar tone is going to push something out of my circuits, even with a brain the size of a planet I only have so much space.

[@Mrshoujo]

"We Apologize For The Inconvenience."

[@marvintpandroid2213]

@@Mrshoujo and other terms from the good book.

[@alexlandherr]

I think all video conferencing software should use this. Would solve that pesky problem of people talking over each other...

[@paulromsky9527]

Great video. I am going to add Quidnar tones to my home landline phone. I am going to use an Adafruit Trinket M0 which has a true DAC Analog output that can produce these tones in phase, a single pole RC LPF, and a 2N2222 as a speaker driver, that should do it.

[@marcusdamberger]

I remember that untill they built the new Huston mission control center rooms they had these tones going into 90's from the original Apollo era control room. You knew Huston had control when those tones sounded. When they would transfer control over occasionally to the Marshall Spaceflight Center those tones would go away tell Huston took over again. During Shuttle missions.

[@ryanhebron4287]

I'm surprised you didn't decide to modify a desktop PTT mic from a ham radio set.

[@paulmorley1225]

Marc chose that one specifically for it's aesthetic and extra mute button that could be repurposed.

[@Testequip]

Thanks for that interesting topic. Since there were just over 20 STADAN stations worldwide, I'm assuming the Quindar tones were also used for all the STADAN nodes. I'm curious if they were. In the early 80's I had a brief stint at the Hartbeeshoek Earth Satellite Station (telephony division) South Africa. Next door is Hartrao/SANSA fomerly known as DSS-51- one of the STADAN nodes.

[@leewyton7975]

Pretty damn good!

[@davidyoder562]

I was thinking about it, wondering how we would have ever heard these tones if they are used to signal PTT. My logic was that if PTT was not initiated until the tone, then the transmission would not include the tones (or at least they would be somewhat truncated). Then I realized, well of course, recordings we've heard on the ground would have been sources upstream of the remote link. So we hear the what the transmitter station hears. I wonder, then, if what the astronauts heard would have been a more chopped off version of these tones? Kinda makes me wonder about whether they did, indeed, use these as courtesy tones? 🤔 (I'm also the guy who watches Back to the Future and points out all the logical flaws 🤦‍♂️)

[@TeslaTales59]

I like the Quindar tones. The are important for clarity. NASA should always use them.

[@draganlalkovic567]

Very interesting work. The symbol for NMOS in the final schematic is wrong 😄

[@Wizardofgosz]

Just make a foam windscreen for the cheap mic and it will probably clear up the boominess.

[@BM-jy6cb]

Really interesting. No idea they were developed for the equipment and not the people, but what exactly did they enable in the equipment? Would be a nice follow up video. Thanks.

[@muadeeb]

Probably just a simple xmit on/off control circuit. Used to have something similar in the Marti RPU great, but it was typically used in a repeater setup and not exactly in band audio

[@gcewing]

Beep, fascinating video, boop!

[@TomKappeln]

One for the algorythm

[@Damien.D]

never understood why these tones are not mandatory in any ptt comms. It's so easy to mentally iolsate a message thanks to them.

[@marka7831]

I think I will use the "Apollo Beep" courtesy tone on the club ham radio repeater during the week of the moon landing anniversary.

[@ml.2770]

The cheap mic sounds more authentic.

[@cprogrck]

The only legitimate use of a roger beep lol.

[@rtchrg440]

Fantastic - love hearing the original tones! Any thoughts on hooking up a Plantronics M50 headset, like they used in mission control?

[@Richardincancale]

Does anyone know there the word ‘Quindar’ comes from? Is it a company name or something? [Edit: A quick search shows it was named after the company who made the tone creation/detection system - Quindar Electronics]

[@nigeljames6017]

I’m getting a little old I suppose, but I can hear the talk, make out the circuit diagram, but for the life of me I can no longer hear those tones. Another bit of history lost but logged in my brain.

[@dataruin]

Marc, any chance you know about the tones generated by the Soviets? I’ve got the tone from the Chernobyl fire station call stuck in my head. Was going to try and tackle it with an FM synthesizer.

[@giggling_boatswain]

I think that an exhibition stand is needed that can be safely transported from museum to museum with a detailed description and connection diagrams, so that even after 60 years the stand can work and repairmen can quickly figure out what's what according to the instructions and the attached diagrams with a description of the work (this is very important create a detailed service manual for future generations). You can even come up with a special shipping container with fasteners for all the elements. The idea is this: I brought it, took it out, assembled it, dismantled it after the exhibition, put it in a container, and took it away. And such a special shipping container for each stand, for each interesting equipment. After all, the task is to demonstrate live a working sample to as many people as possible. It's worth it.

[@TheHighlander71]

My two cents: "Quindar tones were named for the manufacturer Quindar Electronics, Inc., now QEI" - Google

[@muadeeb]

Thank you. Had some of their fm equipment at a station I worked at, and that kinda explains their look

[@Allan_aka_RocKITEman]

*_Cool._*

[@Pedro8k]

On CB they were called Roger bleep

[@DRNEGOLICIS]

im currently trying to add the tones to my UHF repeater system DE KG5DHL

[@AmauryJacquot]

genius !

[@DrewNorthup]

I have no idea what you did this time in processing your audio, but it oversaturates a 10mbit/sec (max) bandwidth completely.

[@ezquimal]

How they connect the push to talk with the relay of the linear amplifier that transmite the voice? Or that was made manual?

[@camhyde9701]

3:46 - Eb and D roughly =)

[@MrMilarepa108]

Not the stir to the oxygen tanks!!!!

[@Consequator]

Neat!

[@kd1s]

Ooo cover DTMF and the old MF signaling

[@zebop917]

I can think of one or two Zoom calls I’ve been on where these tones would have been useful and maybe stop people,talking over each other 😀

[@johankotze42]

Roger-Bleeps?

[@SidneyCritic]

Why didn't they put them on CB radios, because "over" was very over used over in those old days - lol -.

[@kd1s]

In the amateur radio community they're known as roger beeps

[@leovanzantvoort]

as a HAM in the seventy's, everyone has to have "roger-piep" in europe! We all build one!

[@NonEuclideanTacoCannon]

What the hell kind of fancy breadboard is that? I want one.

[@CuriousMarc]

Here is the whole repair adventure of the E&L breadboard system: kzbin.info/aero/PL-_93BVApb582yUOlRmTJYVtPwrs1pbrh

[@NonEuclideanTacoCannon]

@@CuriousMarc Neat! I would definitely use something like that.

[@EthanRDoesMC_]

“Warning, it’s loud EEEEEEEEeeeeeEEEEEeeeeEEEE”

[@zeproo]

Sounds like a ham international CB radio roger beep lol

[@mfx1]

If the intro tone started the transmission then how would the astronauts hear them?

[@smartups1]

I requeste you . Please open the Apollo comand module sine wave inverters .

[@gesamtszenario]

And I thought it was just a peculiar kind if roger beep.

[@flinkiklug6666]

nooo, where is the Intro Music

[@mick_hyde]

Would they have used these components though?

[@Edisson.]

Thus, these notes can be created with the help of two potatoes, ten balls of grape wine, a quarter of a kilo of lemons, several gold and silver bars, three Deuxtelidr decanters and two grams of Tracoquazischutroiridibixtenia. Unfortunately, in today's over-technological age, Deuxtelidre decanters and Tracoquazischutroiridibixtenium are completely unavailable, so it's done the way it's done - simply and brilliantly. Great work 👍 Nice day 😁 Tom

[@mikemallano2484]

And, on Star Trek....