A bell is on each of my bikes. When on a trail if I can not see beyond a turn I ring the bell BEFORE THE TURN alerting anybody/dogs that I am approaching. Over the years this has resulted in people often commenting with "Thank You" along with a smile as we meet around the bend. On open areas I ring as I approach from the rear AND ALSO INFORM with "Passing on your left." This combination also can result with a "Thank You" or a simple "Wave Of The Hand" as the person moves over. What is strange is when I approach from the front and am seen by people walking towards me, there are times when one goes right and the other left instead of getting INLINE. Not only is that move not smart, it results in reducing the allowable distance of passage.
Ringing a bell EVEN LIGHTLY will often result in some form of recognition by a dog BEFORE THE PERSON because the dog's hearing is often better.
My bells are old Schwinn Approved Bells from the '70's.