Fog bells

[Carl S Zimmerman]

In David Cawley's interesting article on buoy bells (this week's RW, 
p.1081ff), there is reprinted a 1911 advertisement from J.Warner & 
Sons for "lighthouse, fog and buoy bells". That terminology seems 
odd to me, because all of the instances of fog bells which I have 
found in America have been associated with lighthouses. (Buoy bells 
are apparently the same the world over.) What is the distinction 
between lighthouse bells and fog bells in English usage? Or were 
Warners simply being sure to cover all possible terminology at once?

CSZ