English Dictionary

fog signal

noun

(rail transport, UK) A small explosive charge (detonator) which can be placed on a railway line in fog, to be detonated by a train passing over it as a warning signal to the driver.

The fog signal warned the approaching train of the thick fog ahead.

意味（1）

(rail transport, UK) A small explosive charge (detonator) which can be placed on a railway line in fog, to be detonated by a train passing over it as a warning signal to the driver.

The layman does not realise the dreadful nightmare of running in fog, especially at night, when the safety of everyone depends on the driver hearing the fog signal detonate.