Channel Marker Query

[Z6982667]

Just a general question.
Is there a rule/reason as to why some channel markers have bells in and some don't?

 

[KREW2]

Isabelle necessary on a channel marker
I'll get me coat.

 

[johnalison]

If every marker had a bell, then a mariner in a fog would be unable to tell one from another. With only the occasional one having a bell, as with topmarks, you should know where you are if you have a rough idea in the first place.

 

[PeterV]

Yes, I think it’s a strategic choice. I once sailed into Plymouth Sound in very thick fog. We picked up the first bell buoy off the western entrance then set a course for the next bell and so on until we got into Millbay dock. Pre gps, Decca etc.