This alarm signal was not military issue, but as a nice pyrotechnic I placed it here with mines.
It was manufactured by JNS Leeuwarden, NL.
It was used by the NS "Nederlandse Spoorwegen" to be placed at a distance of people working on the railroad track.
When the train went over this, a loud signal could be heard and the driver was alarmed to slow down and stop the train.
Photos © M. Jochoms.