No Snoring

This morning I was reading on the train when I happened to look up at the electronic display at the end of the carriage.  These displays are used to inform passengers of the stations visited and other relevant information.   Each display shows a fixed number of letters which are formed out of rather chunky triangular pixels.  The information is flashed up cyclically, a few words at a time.  This way a display will take several minutes to show the full list of stations and other information, then it goes back and starts at the beginning again.  Some of the displays have faulty pixels which either stay dark or stay bright all the time.  Well, this morning, when I glanced up, I am sure I saw the message:

Snoring is not permitted

It took a while for the strangeness of this to register in my brain.  When it did, I put my book away and kept watch waiting for the message to come round again but, unfortunately, we got to my stop before it reappeared.