Detonator (railway)
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A railway detonator (also called a torpedo in the U.S.) is a device used to make a loud sound as a warning signal to train drivers. The detonator is the size of a large coin with two lead straps, one on each side. The detonator is placed on the top of the rail and the straps are used to secure it so that it does not fall off. As the first wheel of the train passes over the detonator, the detonator explodes, making a loud bang.
Typical uses of detonators include:
- a warning of a caution or stop signal aspect in dense fog, when signals are difficult to see
- a warning of a train stopped on the line ahead by an incident or accident – the train's personnel are usually responsible for placing the detonators
- a warning of permanent way works ahead
- when a signaller or other railway employee requires to stop approaching trains in an emergency
As with all explosives, detonators could become unstable after a period of time and therefore they must be replaced regularly.
[edit] Detonator placer
Many mechanical signal boxes in the UK were fitted with detonator placers, which automatically placed a number of detonators on a running line when a lever was operated in the signal box. The levers were painted a striking white and black chevron pattern – pointing upwards for the "up line" or pointing downwards for the "down line". The placers were fed from a cartridge holding a number of detonators.
