Talk:165: Turn Signals

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I have at times become mesmerized by the "click-click click-click" of my turn signal relay while watching the flashing signals on the car ahead of me. It's fun to notice how they drift in and out of sync, but I never bothered to determine the beat frequency. --Smartin (talk) 03:53, 2 January 2013 (UTC)

What, to me, seems amazing, is not just that they are (certainly within extreme observational tolerance) beating at the same frequency, but are also in phase. At that point I would begin to suspect that they're each connected up to the same time-signal source (e.g. a GPS data output), and cued to begin each cycle on the flip of each whole second, or similar. Of course, IRL, that'd be an answer in search of a problem. And you want your signals to start flashing the moment you activate them, so even if guided by an atomic clock you'd probably have any given pair (albeit maintaining the same frequency) exhibiting a (constant) phase separation.

As for talking about being not held externally in sync, reminds me of the lights certain riders of tricycles have on their machine, in a 24-hour cycle race (mainly for bicycles, but trikies do tend to ride it as well). Flashing LED rear lights, very bright. On the backs of trikes they tend to put the lights out on each splayed rear stay, as well as the axle between the two rear wheels, to emphasise their width to any traffic that will be overtaking them in the night. Usually three identical flashers, but (as noted) the timings are rarely in sync, never mind in phase. As they're arranged in a triangle and very rarely all three on the same beat you can watch the machine as it retreats into the distance (my usual view of these phenomena) and when two of the lights are in sync and agreeing with each other, but the is off the beat, there's an effective directional 'wash' of light, this direction of wash changing as the in-syncs depart and perhaps the odd one syncs up anew with one of the other two originals. And if they all find themselves +/- 120-degrees out of phase with the other two, at any time, you get a rotary pattern emerging for a few moments.

You probably have to be there, but it's a sight to see, in the dead of night. And analyse. ;) 178.98.31.27 03:12, 22 June 2013 (UTC)


This merits a more fleshed-out explanation of beat frequencies and such. It's good enough, however. I'm not mean enough to mark it as incomplete for something like that. --Quicksilver (talk) 05:55, 24 August 2013 (UTC)

I would expect an irrational ratio of frequencies and all possible relationships appearing over a long enough time period. If ratio is close to one, they would appear to be nearly together for a reasonable period and far off for a reasonable period.--DrMath 01:49, 31 October 2013 (UTC)

This is somewhat reminiscent of Neal Stephenson's discussion, in Cryptonomicon, of Alan Turing's bicycle with a damaged link and a bent spoke, and how the two have to sync up for the chain to fall off. From this, he then does a wonderful sleight of hand, and before we know it, we have a fairly decent understanding of the Enigma machine. -- Ravenpi 23:50, 20 Feb 2013 (EST)

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