Messages From Hell: Human Signal Processing

Despite the title, there’s no religious content in this post. The Hell in question is the German inventor [Rudolph Hell]. Although he had an impressive career, what most people remember him for is the Hellschreiber–a device I often mention when I’m trying to illustrate engineering elegance. What’s a Hellschreiber? And why is it elegant?

The first question is easy to answer: the Hellschreiber is almost like a teletype machine. It sends printed messages over the radio, but it works differently than conventional teletype. That’s where the elegance comes into play. To understand how, though, you need a little background.

Giant Brains and Porn

You don’t hear it as much as you used to, but there was a time when people called computers “electronic brains.” In the 1970’s, RCA had a recruitment ad that stated (if I recall correctly): “The best electronic brains are human.” That slogan made a big impression on me, and I’ve found it to be true in many cases.

You don’t have to look far to see examples. Phones have become pretty good at speech recognition, but little kids are at least as good. Computers can write novels, for instance, but humans do better. Even in places where computers can do better than us, like chess, it takes a really big computer.

Racknitz_-_The_Turk_3Of course, our computers are superb at some things that we aren’t good at doing. That’s why, to me, the most elegant systems use the strength of the computer along with the power of the human brain. One of the strangest examples of that is Amazon’s Mechanical Turk service. The Mechanical Turk (seen at left) was a famous 18th-century fraud that appeared to be a chess playing robot. It was actually a puppet operated by a chess playing man.

That’s not elegant at all. However, Amazon’s service allows companies to get human services from people in exchange for small payments. For example, suppose you have a photo sharing site, and you want to filter out pornographic images. As the U.S. Supreme Court’s Justice Stewart said:

I shall not today attempt further to define… [“hard-core pornography”]… But I know it when I see it…

It is difficult (or maybe impossible) to write a computer algorithm to classify pictures correctly as pornographic or not with no false positives or negatives. However, just about anyone could look at a picture and press a yes or no button and be right just about all the time. That’s the kind of thing you can farm out to the Turk service. The computer is good at transmitting and storing images. The human is good at classifying them.

So the Hellschreiber is Porn?

No, the Hellschreiber is not porn (unless you transmit the text of “50 Shades of Gray” with it, I suppose). However, it is an elegant use of the computer/human symbiosis. Think about a conventional teletype. A five- or eight-bit code modulates a radio signal (usually via frequency shift keying). The receiver notes the frequency shifts and reconstructs the code to determine what the message is.

That’s great if the link between the transmitter and receiver is a quiet wire. When the connection is via noisy radio, that’s different. Today, we can use digital signal processing to get better results than ever. We could put in sophisticated forward error correction codes, and we could use more robust modulation. But this takes more hardware that wasn’t available in Hell’s day. If a static crash or fading took out a bit, the result was a garbled message.

Humans are pretty good at recovering messages. If I wrote:

The ouick brown fox jumps over the l!zy red do8.

smartYou can probably figure that out. You’ve seen the social media meme (to the left) where a message jumbles letters, and you can still read it. But in both cases, those messages still resemble the original message (and you sort of know what to expect them to say). If you got the message:

Meet me at the ($sdfk82.

Looking at this message, you probably can’t figure out my meaning. With a Hellschreiber, you have a better chance. Why? The Hellschreiber is like a cross between a teletype and a FAX machine. The device sends pictures of the letters, not codes. Not too surprising when you realize that Rudolph Hell had a background in television. Your brain can more easily unscramble a picture than a code that was randomly changed by noise.

Actually, the machine sends two images of the text to help in recognition. Noise or phase differences may make it a little hard to read, but it has to be very bad for the wetware between your ears to not be able to make sense of it. You can see a sample below:

Feldhell

The machine uses a 7×7 grid to form the letters. The characters are only sent once, but printed twice. As you can see, sometimes (due to timing errors) both lines are visible. Other times, one line is legible in the center and the other line appears chopped off at the top and bottom.

Modern Hell

Hams still use Hellschreiber as a communication tool. Today, of course, the mechanical machines are gone, and you use software with a sound card. Using software allows wide variation of character sets and even gray scale as an enhancement. You can see an example of some QSOs (ham-speak for contacts) using Hellschreiber in the video below.

Granted, digital modes that use forward error correction and other sophisticated methods can use the power of the computer to (usually) ensure error-free transmission. But Hell’s invention is a great example of why RCA said the best electronic brains are still human.

As designers, we are often in love with the machine parts of our design. However, a good system may be able to integrate human intelligence with the machine and surpass both.

54 thoughts on “Messages From Hell: Human Signal Processing

    1. Interestingly when Deep Blue was being developed, the best computer chess at the time ran on a single core pentium, and was also able to sometimes win or draw a tie with Kasparov.

      In fact the had big blue play against this desktop class AI, and the desktop AI essentially held it’s own at first.

      1. That’s because chess rules have such a large number of possible games that it’s practically impossibe for any machine to find all of them. In other words, it’s not a “solvable” game, like checkers or connect four is.

        It takes exponentially more computing power to improve on the game, so to beat a basic desktop computer in chess hands down requires the fastest supercomputer there is, and there’s still a chance it will lose sometimes.

  1. A technique taught by the Army to help get through some forms of (audio) jamming is to repeat each word.
    A A technique technique taught taught by by the the Army Army to to get get through through…

  2. “Humans are pretty good at recovering messages. If I wrote:
    The ouick brown fox jumps over the l!zy red do8.
    You can probably figure that out.”

    Sure, the message there is that your mind just painted the dog in red.
    :o)

  3. Well, yeah, it gets a clear message over a slightly noisy channel, at the expense of 7x the bandwidth. Not really a signal issue at all, more a “what he had available” one. And I’m sure the aether was quieter back then.

    1. Indeed, in todays world of LDPC, hamming codes and MIMO antennae, this is definitely more of a hack than a useful tool. We have vastly more principled ways to do error correction today. I don’t think Al has fully grokked the rise of the machines. And for what it’s worth, I expect current OCR would out perform a typical human at this code too.

  4. I love hearing about old technology ideas like this. It makes one wonder at the thought-evolution-process humans go through when inspired by a problem. However, it’s more amazing when they achieve a solution where no problem exists. I like Hell’s idea however. It was used by the German’s in WW2 to enhance ENIGMA transmissions I believe, And of course SIEMENS arguably dirty hands are all over it too, They are still going strong today in high technology,

    Al Williams – I particularity was impressed about your HaD article about FREEDV (Hams Talk Digital Sept 6, 2015) . I’m still blown away by it and want to play with it ASAP. I downloaded it but haven’t had the time to set it up yet.

    Reading all this stuff inspired me to diagram this. I call it OVALTINE for obvious reasons some of you will get right away. I know you HAMS will say ALREADY DONE! RE-INVENTING THE WHEEL! Just humor me and look at it and tell me what you think. You can be brutally honest I don’t mind – just don’t flame me! :) http://oi66.tinypic.com/9gzx9u.jpg

    SQTB

  5. Al Williams –

    You can probably figure that out. You’ve seen the social media meme (to the left) where a message jumbles letters, and you can still read it. But in both cases, those messages still resemble the original message (and you sort of know what to expect them to say). If you got the message:

    You were right! I read that thing the first time without backtracking at all! What an anomaly. I like stuff like that. Keep ’em coming…

    SQTB (aka SOTB)

  6. Human beings are great at pattern matching with lossy data, hell we’re so good at it we sometimes see patterns that aren’t there, e.g. faces in clouds and conspiracy theories.

    1. Most cases of seeing faces etc in cloud shapes are due to the pattern being there, if the pattern isn’t really there you are hallucinating. The brain is good at extrapolating and interpolating to get the most likely solution. The most likely solution in the case of a cloud ‘face’ is a generic approximation to a face and that is what you see. If you see an image of Big Brother or Chairman Mao etc then you are hallucinating. Same with conspiracy theories.
      Always wondered what Hellschreiber was – great article, and well written.

      1. Yeah but the “pattern” that’s there is a lot less like the pattern we recognise it as. Pareidolia is the word. There’s big chunks of brain devoted to face-recognition, and seeing emotions on faces, etc, even babies can do it. And often it over-matches. It’s a problem electronic neural networks have too.

          1. Actually my favourite old-time NN story is, some defense contractors, or the US Army, or whoever, were working on a tank-spotting NN. They fed it tons of pictures of leafy glades, with tanks, and without tanks.

            It got pretty good with the test set, but was useless with most other data.

            After much analysis and hypothesising, they discovered all the pics of tanks were taken on cloudy days. The no-tank pics were sunny. And that’s what the NN was spotting.

            From the 80s or so, this story.

          2. Greenaum – I heard about this too. It’s probably apocryphal as DARPA would not just rely on one input – a camera. It’s logical that RADAR would have been used as there are tress and a tank (duh!). Also the hiding tank already knows you’re there so a RADAR blast would not expose you. You already are exposed.

            Also the Germans learned from their NN experiments to add in OCR to look for partial serial numbers to match up. But of course I need to through in my brainstorm as you know that is my predilection:

            1. The Israeli Defense Force (IDF) likes to recruit color-blind soldiers (they are mostly males). Morgan, M. J.; Adam, A.; Mollon, J. D. (June 1992). “Dichromats detect colour-camouflaged objects that are not detected by trichromats”. Proc. Biol. Sci. 248 (1323): 291–5. doi:10.1098/rspb.1992.0074. PMID 1354367

            2. Red-Green Dichromats can see camouflaged people, animals, and tanks in forest moving about. But moving their own heads will also reveal stationary objects (like how owls do). I know this is true as I’ve done it.

            3. If DARPA could design a pseudo-Dichromat camera, they too could exploit this effect in spotting camouflaged tanks.

            4. However, if the latest active-camouflaged (i.e. invisible) tanks the British MoD are bragging about and the Americans refuse to confirm nor deny for their optical metamaterial suits for their tank commanders… That will need to involve a different tactic like RADAR. ultrasonics, bathing area in UV light and using UV detector or the new USN magnetometer. Or use an aerosol spray to flood area with clear fluorescing paint and UV light again. Urine works well :)

            SQTB

          3. I think the story’s referring to research in a lab, not an implemented system. They probably would rely on more than just image-recognition in practice, but this story is from the development of the image-recognition.

            I can’t see why they couldn’t invent a dichromatic camera, just pull out the “blue” wire or whatever. Perhaps spectrograms would help, perhaps cameras with a very narrow and specific wavelength range for each of the RGB sensors. If it were me, I’d be researching exactly what the difference is between colour-blind perception and trichromatic in humans.

            Or look outside the visible spectrum. Certainly from crop photographs from satellites, plants show up very vividly in some IR ranges, and not in others. So in a forest it might be easy to tell the difference between leaves and something just painted green, particularly if it uses paint that’s a mixture of pigments.

            Of course the stage after that is to invent better paints, at a cost of millions of dollars that could be going somewhere useful instead. Perhaps the world should agree to keep everyone’s weapons exactly as they are. Arms races are incredibly expensive for something so ultimately pointless.

          4. Greenaum says:
            January 1, 2016 at 12:49 pm

            I think the story’s referring to research in a lab, not an implemented system. They probably would rely on more than just image-recognition in practice, but this story is from the development of the image-recognition.

            I can’t see why they couldn’t invent a dichromatic camera, just pull out the “blue” wire or whatever. Perhaps spectrograms would help, perhaps cameras with a very narrow and specific wavelength range for each of the RGB sensors. If it were me, I’d be researching exactly what the difference is between colour-blind perception and trichromatic in humans.

            Or look outside the visible spectrum. Certainly from crop photographs from satellites, plants show up very vividly in some IR ranges, and not in others. So in a forest it might be easy to tell the difference between leaves and something just painted green, particularly if it uses paint that’s a mixture of pigments.

            Of course the stage after that is to invent better paints, at a cost of millions of dollars that could be going somewhere useful instead. Perhaps the world should agree to keep everyone’s weapons exactly as they are. Arms races are incredibly expensive for something so ultimately pointless.

            The truth be told it’s the problems in the RED-GREEN band that is key not the BLUE. We R-G dichromats confuse shades of red’s and greens and feel a tree trunk is GRAY not GREEN. WE also have trouble with BROWN leaves. At the thrift store they use color codes. I have to always ask WHAT COLOR IS THIS? Same with resistors.

            You’d have to play around with glass filters over your camera lens to make it truly dichromat like us. We can see a soldier or tank because they are trying to replicate the greens and browns too much with their paints (as you say). But that doesn’t explain how we can see natural camouflage like baby deer, tigers, chameleons. etc. However, cephalapods like Cuttlefish and Octopus have us totally fooled.

            I personally think it involves movement too. Some animals can not see you if you stand still (i.e. allegedly Tyrannosaurs, Bears, Elephants, etc.) but will instantly see you if you move. If we are going to evolve our Active Camo devices we better study the Cuttlefish more closely. We need to exploit the chromatosphore and nanotechnology and scrap the optical metamaterial idea as it is easily defeated. The intrinsic scintillation-effect gives it away (just like in the movie Predators).

            You should be a quartermaster for MI-6 or GHCQ – but maybe I’m too late? I lost my chance when I didn’t join the military back during Vietnam. And I allowed others to convince me to take a pass on the “other” stuff for conscientious reasons. My social-media techy-pontifications are not helping either. I’d love to work for DARPA.

          5. Well, I did say “or whatever”! Yep I know red-green is the most common colour-blindness, my brother has it to some degree. Much more common in men, since it’s a defect on the X chromosome, women have a spare one as backup. I’ll have to ask my brother actually, got some RGB LEDs, might experiment on him one day. I mean, with him.

            Working as Q for James Bond would be a massive laugh, but I’m not going to join any militaries or spies either. Due to, y’know, all the evil stuff they do and are responsible for. It’s a shame, the worst people have the most money and the best toys. I’ll just remain a geek at large.

            Metamaterials are still pretty new, give them a bit of time maybe. Chromatophores might possibly come along from some display technology. Adam Hart-Davies, a great British TV nerd, did a thing where he stuck LED video panels and cameras on a car and drove it through a wood. Worked better than you’d think. I think the “invisibility cloak” is being developed as much because it’s cool and awesome, as for any practical use. Men are just big kids sometimes!

            Actual cuttlefish chromatophores, as you probably know, are little coloured units that can expand and contract, to show or hide a colour, there’s a variety of them, for each colour it can do. Nanomechanics might do that. Maybe it’d end up a faster E-ink. Maybe E-ink itself would be faster if they found a different liquid to suspend the balls in, something thinner, but with some way of keeping the pigment balls where they are.

            Stuff stuff, things things…

          6. Oh Christ! All this time I just ASSUMED you were a bloke vs. bird… I believe I got your bloody chromosomes all cocked-up! Sorry mum! :-)

            But anyways… you are correct about that cloak. The Japanese are perfecting one too, If you want to freak out your brother… get one of those colour-blind charts and ask him to find the number in red or green. He wont find it and will probably start swearing…

            The Cuttlefish is so bloody alien! Even a marine biologist recently said that but I don’t know what he meant by that. Look at some YouTube videos about it and be amazed. If we could harness that camouflage it would be amazing. And yes nanotechnology will probably discover it soon.

            You know first Jurassic Park movie was originally written to have Camouflaging Tyrannosaurs? But they took it out of the script. Don’t know any birds or chickens that can do that. http://rlv.zcache.com/camouflage_chicken_silhouette_stamps-r564d1e8b80d84dbe8d90be3b8558813d_zh10c_1024.jpg?rlvnet=1

          7. Not to sound misogynistic but I some how feel relieved by your revelation here. I envisioned you more of a Daniel Craig character versus a Dr. Madeleine Swann (Spectre 2015). You can envision me as an American version on Ben Whinshaw sans anti-hetero proclivities. I guess John Cleese (also a quartermaster) would be a better example as he is older and is very hetero like myself. ( I hope that’s not a homophobic self-incrimination? LOL)

            Not to sound like hero-worship nor bro’mance, But I am quite impressed with your perspicacity here, Not once have you ask for clarification on my eccentricities nor have you resulted to invectives or pejoratives to compensate for lack of intellectual acumen. Bravo Bro! (I’m silly I know…) %-P

            SQTB

    2. Hirudinea – “Human beings are great at pattern matching with lossy data, hell we’re so good at it we sometimes see patterns that aren’t there, e.g. faces in clouds and conspiracy theories.”

      So true! Here is a pattern… can you match it? http://oi63.tinypic.com/2n7gvix.jpg
      To me it appears to be biological in nature… however it could be the infamous “overlyglibourushackadayusposter” I think it’s a conspiracy theory though! :-P

      1. Wow! Tinypic is a heap of fucking shit nowadays! You get an actual small pic, then a whole page full of click-baiting nonsense. Maybe bandwidth needs to get expensive again. Or the magnetoresistance effect turning off, so hard drives will be small enough to not clog web servers up with so much shit.

        1. Yeaj I know… tinypic has really loaded up the bloat. However, I thought I had it beat by using the longer oi63… url but I noticed even I got hit by the bloat too this time. I wanted to offer a bloat-free full screen image. They fooled me again! Maybe I’ll use IMGUR from now on.

          Thanks your magnetorestiction comment just exposed another gap in my autodidact education. Now I have to research the hell out of it and brainstorm another application they didn’t think of yet. I’m still trying to figure out what it is and how it differs from the Hall Effect. I’m thinking the US NAVY could use something like this for their new magnetometer gadget. It may already be on their SPAWARS invention website. I love that web site about as much as I love HaD. However, they monitor your visit heavily…

          1. I think it’s something to do with the direction of electrons travelling down a thin wire. A magnetic field perturbs that, so the electrons don’t travel as efficiently = greater resistance. Giant magnetoresistance might be something else. As much as it matters… I’m all in favour of useless information, but MR is a bit specific to learn in depth. Then again I know greater depth about equally impractical stuff to my life. Depends what takes me that day!

          2. I probably should not post this but they do put it out in the public forum. If you are brave enuf’ to look around at some of the NEW latest and greatest stuff “THEY” have – go ahead, I can’t vouch for the digital certificates but they probably are looking up your skirt (as some say) during your visit – so bad guys beware!:

            http://www.public.navy.mil/spawar/productsServices/Pages/default.aspx

            This site can give us HaD folks some really cool ideas for our R&D?

  7. Commenters seem to be forgetting that this is retrotech; sure, modern techniques are better and faster, but this is a “man/technology who paved the way” article. And, in the 1970’s, the airwaves really were jam-packed with activity. They didn’t have modern fiber optic trunk lines, and satellites were still in the experimental stages. [my comment feels incomplete to me, but I can’t figure out what else to say]

      1. Shortwave is not shut down, Very much alive. VOIP is really starting to pickup and ROIP (Radio over IP) is actually breaking technology. Many organizations haven’t really exploited ROIP to it’s real potential. Only HAMS have really exploited it. Check out ZELLO dot com and their ROIP product. You can connect your FRS/GMRS to it and have radio nodes across the USA for your company’s mobile radio units. You can use their free service and VOX or the paid service with a RS232C trigger for your radio’s PTT button. http://www.youtube.com/watch?v=VjvYjFkYalI

    1. Thanks to our overly paranoid government during the Cold War – satellite technology started in the 1950’s but we were told we were putting monkeys into space… Google: Corona Program. It was declassified by POTUS Clinton in 1990’s. Also fiber optics used for communications dates back to 1965 by Telefunken but we knew about glass fibers to conduct light as far back as 19th century – just not communications yet, Alexander Graham Bell could have used them for his Photo Phone VLC device if he had known of the research being done by his contemporaries.

      In 1975, the United States Government decided to link the computers in the NORAD headquarters at Cheyenne Mountain using fiber optics to reduce interference. In 1977, the first optical telephone communication system was installed about 1.5 miles under downtown Chicago, and each optical fiber carried the equivalent of 672 voice channels.

      There’s a lot of logistical reasons why the common American never knew of these technologies as they were being R&D;d, BION (believe it or not) glass disc’s used to record audio to a photo conductive material dates back to the late 19th century (By Bell and HG Rogers), Only they had no idea how to play the discs back. That was not until recently someone at the Smithsonian figured out how to play those old discs. Now today we have Blue-Ray, DVD’s and CD’s.

        1. Bell did some other strange things I am still trying to figure out. He wrote some papers from his public conferences around the country. Not only was his Photo Phone way ahead of its time he was working on something else. The Photo Phone really was not his. A British man did the same thing about a year earlier but could not or did not patent it.

          He was talking about spinning up a large disk of vulcanized rubber, He had some sort of diffraction grating in front of it. He claims that every time he illuminated it with the sun via mirrors or a focused beam of light from a oil lamp it made an audible sound directly from the rubber (a deep hum)! But only while it was spinning. No one has seemed to care to study it any further for over a century. Is this just another “orchard” awaiting exploitation? Remember his Photo Phone idea led to the VLC FSO Communication devices today NASA is using for outer-space comms right now,

          That “spinning” thing I think is key. We recently discovered TRUE anti-gravity with a 5000 rpm disk of Yittrium-Barium soaked in liquid Helium, Boeing and BaE are already exploiting it. A NASA employ did parallel research and quit to start her own consultancy on this AG subject matter and got sucked up under contract to US Army (Redstone Arsenal).

          So many things we miss when we fail to think outside the box! Ben Franklin and Thomas Jefferson were two out of the box thinkers way ahead of their times.

          1. Alexander Graham Bell delivered a lecture before the American Association for the Advancement of Science, in the Institute of Technology, Boston, August 27, 1880. The topic was “ON THE PRODUCTION OF SOUND BY LIGHT”. He was describing how he and his partner where R&D’ng the Photophone (later changed to Radiophone). In the lecture he goes into the various things they used as photo-voltaic detectors. They finally decided on selenium which turned out to be very good but not as good as silicone and germanium we use today. However, what they discovered in between all that was in fact BAFFLING, even today.

            Supposedly some materials are photo-voltaic in a very DIFFERENT way then we understand. They can allegedly give off a audio tone when exposed to light that is moving across it’s surface. Hence a spinning disk with some sort of light diffuser is what reproduces the anomaly.

            If you want to take a crack at explaining it please be my guest. Popular Science did an article on it in it’s October 1880 Volume 17 addition. Here is the article: http://en.wikisource.org/wiki/Popular_Science_Monthly/Volume_17/October_1880/On_the_Production_of_Sound_by_Light Please read it carefully before being summarily dismissive about the part with the vulcanized rubber. I’m sure there is no easy answer. An answer is there but it may involve some more R&D to see what it is and what Bell & Sumter just dismissed as an oddity and moved on to selenium.

            BTW to all you Brits – Bell was Scottish not a natural-born Yank.FWIW! :-)

            SQTB

    1. theres a thin line between being cooked alive by radio waves and expierencingnothing…

      the in-between zone might result in you “seeing” certain repeating, specific formulaicpatterens…

      thats why radio techs tasked with climbing 5-foot radio towers while switched-on use a safety harness!

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