A bicycle horn/hooter that when squeezed warns pedestrians that a cyclist is present. It would be attached in an easily accessible place to the handlebars by a bracket.
Bicycle horns like this were not only used on bicycles but on some of the first motor cars designed by Henry Ford. The horns had a rubber bellow on the end and when squeezed let out loud “honk honk” noise.
These were later replaced by bells and the first one was patented by British Inventor John Richard Dedicoat in 1887. The bell is a simple clapper again attached to the handlebar that can be operated to ring out a “ding-ding” sound. Other ways to attract attention are battery operated horns or horns that are powered with cans of compressed gas.
It is not a legal requirement to have a bell or horn fitted to a bicycle although one has to be fitted to your bike when it is sold to you. The Highway code, rule 66 states:
Be considerate of other road users, taking extra care around blind and partially sighted pedestrians. Use your bell when necessary to signal you are nearby.