# How do split-flap display boards work? **URL:** \ **Category:** Factual Questions\ **Created:** [April 9, 2003, 4:40am UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495 "2003-04-09T04:40:53Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Garfield226](https://avatars.discourse-cdn.com/v4/letter/g/9e8a1a/32.png) [@Garfield226](https://boards.straightdope.com/u/Garfield226)\ **Post date:** [April 9, 2003, 4:40am UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/1 "2003-04-09T04:40:53Z")
You know the things I mean… Commonly used in airports and train stations before the advent of LCD screens (and still in some today), these are those boards that make a “clack clack clack” or “flip flip flip” sound as they change messages. I’ve been looking for information on these for a few days now, and I mostly come up with manufacturers. I don’t want to buy one (unless they’re really cheap), but I can’t figure out how they work (especially since they were around before computers, I think). Anyhow, if you want to see an example, go to the Conseco Fieldhouse in Indianapolis, as they have a large one that continually cycles through sports standings. I took a short, low-quality video of it the last time I was there, you can find it [here](http://php.indiana.edu/~baljones/flipper.mpg). Any information would be appreciated. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [April 9, 2003, 4:49am UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/2 "2003-04-09T04:49:40Z")
They’re computerized. They always were. Each little colored element is controlled by a little solenoid that either flips it to the black side or the colored side, depending on the signal being sent to it. All of the solenoids are wired in an array, controlled by the computer, which can address a particular solenoid by thge appropriate X- and Y-coordinate wires in the array. ---
**Author:** ![Garfield226](https://avatars.discourse-cdn.com/v4/letter/g/9e8a1a/32.png) [@Garfield226](https://boards.straightdope.com/u/Garfield226)\ **Post date:** [April 9, 2003, 5:03am UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/3 "2003-04-09T05:03:18Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > \*\*They’re computerized. They always were. Each little colored element is controlled by a little solenoid that either flips it to the black side or the colored side, depending on the signal being sent to it. All of the solenoids are wired in an array, controlled by the computer, which can address a particular solenoid by thge appropriate X- and Y-coordinate wires in the array. \*\* I think we’re not thinking of the same thing, or we are, but I just don’t understand you. Split-flap displays (at least the kind I’m talking about) are made up of segments. Each segment can display many different things. Usually they can display every letter (usually upper-case), several punctuation marks, and a blank flap. There are some which have segments that are long and can display entire words. Disregarding the big ones, the single-letter ones seem to resemble a sort of Rolodex. Imagine a tile with the letter “A” imprinted on it. Now split that tile in half horizontally. On the board what would happen when going from A to B is that something lets the top of the A flap fall, it swings down and covers the bottom half. A “B” is revealed ( the bottom half on the BACK of the TOP half of the “A” tile, and the top half on the top of the next tile. Complicated, I know. I guess I have no direct evidence they were around before computers, but there was one in “The Hudsucker Proxy,” the job board. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [April 9, 2003, 5:10am UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/4 "2003-04-09T05:10:18Z")
Ohhhhhh…those kind. Sort of like the “digital” alarm clocks of old. There’s a little pin at the top which holds the flap from falling forward, and motor that drives the bottom ones back up from behind. The motor is also connected through a series of gears and levers to the pin, which gets pushed up enough to let the foremost flap fall foward, and catches the next one in the series, holding it on the top. The cycle is repeated until the desired display is reached. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [April 9, 2003, 5:23am UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/5 "2003-04-09T05:23:41Z")
Those things are really cool. I was sad when they replaced the ones at the track gates at Grand Central Terminal with digital LED displays. ---
**Author:** ![rjk](https://avatars.discourse-cdn.com/v4/letter/r/ed655f/32.png) [@rjk](https://boards.straightdope.com/u/rjk)\ **Post date:** [April 9, 2003, 5:47am UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/6 "2003-04-09T05:47:30Z")
I seem to recall clocks that worked that way. The digits were split as you describe, attached to the axle, and held in place by a little spring-loaded catch that would slip as the panel rotated forward. Each digit worked the next with a little pin on the appropriate tab. The display you’re talking about probably rotated a segment’s axle one position for each pulse of electricity reaching the motor. Lots of electro-mechanical gadgets, including adding machines, used pulsed motors. (I suppose they could have a single motor for the whole display or one for each row or column, but that would need a clutch for each character anyway. Individually-switched motors would be simpler.) ---
**Author:** ![bradwalt](https://avatars.discourse-cdn.com/v4/letter/b/858c86/32.png) [@bradwalt](https://boards.straightdope.com/u/bradwalt)\ **Post date:** [April 9, 2003, 6:03am UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/7 "2003-04-09T06:03:20Z")
It’s amazing what solenoids, gears, levers and old-fashioned elecro-mechanical gizmos could do back in the stone age “before computers!”. And I do miss the “click-click-click” that those machines made, especially when they reset the scoreboard clock or when a train was delayed at Grand Central! OT: But how did horse tracks figure out pari-mutuel betting payoffs before computers? ---
**Author:** ![Garfield226](https://avatars.discourse-cdn.com/v4/letter/g/9e8a1a/32.png) [@Garfield226](https://boards.straightdope.com/u/Garfield226)\ **Post date:** [April 9, 2003, 7:10pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/8 "2003-04-09T19:10:59Z")
Ok, NOW we’re on track. I have a pretty good idea now of how the mechanics of the things actually worked (though the sheer size of some of them boggle my mind still), so now what I’m looking for is how they were programmed. Or perhaps they were not programmed at all, beyond maybe a simple countdown display, as **rjk** described. Maybe the old ones were simply set up a certain way, and the motors were turned on and off manually when they need to flip the sign. The one I saw at Conseco (the one in the video I took) showed the standings for a particular divison in basketball, then flipped and showed the next, and the next, and so on. I assume it could be programmed to show any message you wanted. Could they do THAT sort of thing before computers, and if so, how? Also, if anyone knows of any websites showing details of how these work, I would greatly appreciate it. Thanks for your help. ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [April 9, 2003, 8:25pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/9 "2003-04-09T20:25:59Z")
Wellllll…not everything is on the Internet. I can’t find a “How Split-Flap Displays Work” web page, but I have amassed many valuable clues as to their operation. Hint: they use electricity. Enjoy. 😃 [http://www.vst-vossloh.com/eng/produkte/fahrgastinfo-fallblatt.htm](http://www.vst-vossloh.com/eng/produkte/fahrgastinfo-fallblatt.htm) > [@](#): > > Split-flap displays and boards for quality and reliability > > With their high contrast, VST split-flap displays and boards are presently the only ones that have excellent readability - even in direct sunlight - ensuring a very wide viewing angle. The clear script is achieved by the printing on the split-flap modules. The colours for the display of texts and graphics can be selected as required. VST split-flap displays and boards are also remarkable for their extremely long life and low energy costs. > > Advantages: > > ``` > Information changes extremely quickly with low-noise and fast rotating split-flap modules (on average 1.5 seconds for modules with 52 split flaps) > Individual design of the displays - the printing allows practically any scripts, colours and fonts > 4 module heights and various module widths > Customized housing design > Easy cleaning of the split-flap modules thanks to removable rotors > Quick and uncomplicated replacement of assemblies thanks to modular construction > Split-flap modules can be removed from the board and replaced even when they are in operation and electrically connected > > ``` [http://www.railway-technology.com/contractors/operation/vossloh/press2.html](http://www.railway-technology.com/contractors/operation/vossloh/press2.html) > [@](#): > > The resulting decision was for modern split flap display units. The VST split flap display units have implemented modern micro computer and electronic technologies. The industry standard HDLC is used as the communication protocol with an optional LAN interface. The synchronic engine means both very little wear and tear and noise is kept at a minimum. > > Noteworthy are the remote diagnostic facilities of VST’s system which will enable a trained technician to see exactly down to the module in the display device at any given time. The device in question can then be disconnected until repaired. All of this information is then logged for future reference. [http://www.solari.it/eng/sistemi/display/confront.html](http://www.solari.it/eng/sistemi/display/confront.html) > [@](#): > > Split Flap Technology > > The flap unit displays owe their extensive application to the perfect legibility of the information. > > The wide reading angle, as well as their proven reliability, makes them valid for applications to large sized areas. Even though the flap is typically an alphanumeric display, it can also show graphic symbols. > > An important advantage is that this is the only technologies that can provide a positive feedback of the information displayed. This can be accomplished by means of a sensor of the “neutral” position and by counting the successive pulses of the stepper motor used to rotate the flaps. > > Disavantage > > Flexibility: wide, multi-module flaps are not flexible since the set of possible messages is limited (max. 79). Single module flaps allow to display whatever message using the characters silk-screened on them. In order to add a new special character it is necessary to silk-screen it on the neutral flap (when available). > Brightness and Contrast during Module Life: it isn’t possible to assure the brightness and contrast uniformity of the whole display when you replace a faulty module with the new one. > Writing time: it can be high. > > Advantage > > Consumption: power is required only during updating operation. > Maintenance Service: no preventive maintenance is required. > Information: permanence of information in case of power failure. > Feedback: automatic checking of displayed information. > Pictograms: multicolor characters / Pictograms [http://www.vst-vossloh.com/wDesign30/presse\_eng/press280901.shtml](http://www.vst-vossloh.com/wDesign30/presse_eng/press280901.shtml) > [@](#): > > Following in the footsteps of Frankfurt/Main and Cologne/Bonn airports, Dortmund Airport is now also equipped with new display technologies supplied by Vossloh Systemelektronik(VST) of Karlsfeld, near Munich. The installation in Dortmund officially went into operation at the beginning of November 2000. In addition to other types of display, split-flap displays are an important element in all VST projects - a technology which seemed on the way to obsolescence, but is now once again at the centre of interest. The reason is the architecture of modern airports which allows a maximum amount of light into buildings, thus making displays with non-reflecting surfaces essential. Thanks to their high contrast ratio, split-flap displays are currently the only displays which guarantee very good legibility at the extreme angle of 140º; - even in direct sunlight. > > Complete change of information in 3 seconds > > The new-generation split-flap displays developed by VST for travel information are high-performance devices. A 100-line board with 6,000 split-flap modules can change all information within 3 seconds. The important advantages of this technology in comparison with others include the long service life of the displays (at least 20 years), low energy costs and individuality of appearance. High-resolution characters and graphics can be selected and combined as required, as well as the colours of the characters and background. In addition there are about 250 different fonts to choose from. When in operation the display only consumes energy when information is changed or erased. The installation does not require any maintenance. For cleaning the split-flap set is simply removed. If you really, really had to know–if you got all obsessive about this and started dreaming about split-flap displays, and every time you put a tape in the VCR you saw grainy B & W “The Ring”-type imagery of split-flap displays–then you could e-mail VST, who seem to be the industry leader in this field, and beg them to send you a diagram of some kind. Tell them you only have seven days. 😃 ---
**Author:** ![Garfield226](https://avatars.discourse-cdn.com/v4/letter/g/9e8a1a/32.png) [@Garfield226](https://boards.straightdope.com/u/Garfield226)\ **Post date:** [April 9, 2003, 9:39pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/10 "2003-04-09T21:39:27Z")
Yup, found all those sites. Considered emailing VST, but I thought I’d ask here first. Guess I could see if they’ve got any info for me. “If **DDG** can’t find it, it ain’t online.” ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [April 9, 2003, 10:48pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/11 "2003-04-09T22:48:49Z")
The alarm clock in the movie _Groundhog Day_ was of this type (in case anyone is still having trouble visualising it) ---
**Author:** ![NinjaChick](https://avatars.discourse-cdn.com/v4/letter/n/71c47a/32.png) [@NinjaChick](https://boards.straightdope.com/u/NinjaChick)\ **Post date:** [April 9, 2003, 11:34pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/12 "2003-04-09T23:34:12Z")
[hijack] One of my most comfortable memories in a very bizarre way: sitting in 30th St. Station at four in the morning, leaning against my suitcase and listening to “Click-click-click-click-click”. Kinda like whatever that background clicking noise is that they pipe into some news radio stations (KYW 1060 for you philly folk). [/hijack] ---
**Author:** ![azulita](https://avatars.discourse-cdn.com/v4/letter/a/898d66/32.png) [@azulita](https://boards.straightdope.com/u/azulita)\ **Post date:** [May 18, 2013, 2:04pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/13 "2013-05-18T14:04:05Z")
So I fell on this site while looking for the mechanics as well. Believe it or not, wikipedia has a nice drawing which helped illustrate it: [Split-flap display - Wikipedia](http://en.wikipedia.org/wiki/Split-flap_display) Just the drawing: [![](https://en.wikipedia.org/wiki/File:Analog_clock_with_digital_display.png) ](https://en.wikipedia.org/wiki/File:Analog_clock_with_digital_display.png) I found those helpful. I’m trying to design something like that for a theatrical production. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [May 18, 2013, 2:13pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/14 "2013-05-18T14:13:30Z")
I can’t find very much information on it, but the first public “digital” clock must have been of this design, since it was introduced over the reception desk of the Chrysler Building when it opened in 1931. See [Chrysler: The Life and Times of an Automotive Genius By Vincent Curcio](http://books.google.com/books?id=dt0uwGwuxPgC&pg=PA431&dq=chrysler+building+digital+clock&hl=en&sa=X&ei=x4uXUdClFvWt4AOO6YC4Dw&ved=0CDoQ6AEwAA#v=onepage&q=chrysler%20building%20digital%20clock&f=false) ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [May 18, 2013, 2:19pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/15 "2013-05-18T14:19:34Z")
> [@bradwalt](#): > > OT: But how did horse tracks figure out pari-mutuel betting payoffs before computers? They always used computers. There was a brief era when single-track betting expanded into the beginnings of pari-mutuel betting where the odds were run by hand calculation, using published tables as a source, but mechanical tabulators - the “French Clicker” - was in use by the 1870s. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [May 18, 2013, 4:14pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/16 "2013-05-18T16:14:05Z")
> [@Exapno\_Mapcase](#): > > I can’t find very much information on it, but the first public “digital” clock must have been of this design, since it was introduced over the reception desk of the Chrysler Building when it opened in 1931. See [Chrysler: The Life and Times of an Automotive Genius By Vincent Curcio](http://books.google.com/books?id=dt0uwGwuxPgC&pg=PA431&dq=chrysler+building+digital+clock&hl=en&sa=X&ei=x4uXUdClFvWt4AOO6YC4Dw&ved=0CDoQ6AEwAA#v=onepage&q=chrysler%20building%20digital%20clock&f=false) I wouldn’t bet on it. A more likely technology would be “dot matrix,” with an array of incandescent lamps. These were used in the early 1900’s. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [May 18, 2013, 4:16pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/17 "2013-05-18T16:16:12Z")
[QUOTE=NinjaChick] … listening to “Click-click-click-click-click”. Kinda like whatever that background clicking noise is that they pipe into some news radio stations [/QUOTE] How times have changed. Ten years later, do any radio news stations still use teletype noise in the background? ---
**Author:** ![NinjaChick](https://avatars.discourse-cdn.com/v4/letter/n/71c47a/32.png) [@NinjaChick](https://boards.straightdope.com/u/NinjaChick)\ **Post date:** [May 18, 2013, 5:36pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/18 "2013-05-18T17:36:16Z")
> [@gotpasswords](#): > > How times have changed. Ten years later, do any radio news stations still use teletype noise in the background? Yes. And at least one apparently now streams online as well, complete with faux-teletype in the background, which I find far more amusing than I probably should. (Also, hello unexpected email notifying me of replies to a 10-year-old thread.) ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [May 18, 2013, 5:47pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/19 "2013-05-18T17:47:41Z")
> [@gotpasswords](#): > > How times have changed. Ten years later, do any radio news stations still use teletype noise in the background? WINS is famous for its faux teletype noise. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [May 18, 2013, 8:59pm UTC](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495/20 "2013-05-18T20:59:13Z")
> [@gotpasswords](#): > > How times have changed. Ten years later, do any radio news stations still use teletype noise in the background? CBS news broadcasts have gone through many versions of this over the years. Each version has been a little more “stylized”, more musical and less like an actual teletype, than the previous version. Currently (at least as recently as I have heard), they have this brief theme music that they play at the start of each broadcast. It still has a beat and tone faintly reminiscent of the old teletype sound, to give a hint of the auld-time “newsroom” environment. [Next page](https://boards.straightdope.com/t/how-do-split-flap-display-boards-work/167495.md?page=2)