Illaveago
Guru
- Location
- Chippenham,Wiltshire.
They were used on railway lines to tell the driver to stop in the event of signal failure, Iembankment was 3 of them spaced at intervals that meant stop immediately.
EDIT - Linky
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiVs8Cen5DKAhXF_Q4KHTzcCNEQFggdMAA&url=https://en.wikipedia.org/wiki/Detonator_(railway)&usg=AFQjCNH2qkUTT3h8o1woVJjJQba1Yve_Fg
Yes, I think one was for caution, and two were for stop. I think they had an automatic loading system. I was born and lived next to a railway enbankment for 23 years so I got used to all sorts of noises.