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Image of track with ramp engaged and steam locomotive on the tracks.
"The Great Western Railway are equipping their engines with an automatic device which prevents a driver from passing a danger signal in foggy weather. If the signal is at danger a ramp in the track operates an attachment to the engine which in its turn applies the vacuum brake. A clear road is indicated by the ringing of a bell in the cab", 15 Nov 1928.
There is no information available.