A doorbell is a bell on the outside of a house which you can ring so that the people insideknow that you want to see them.
doorbell in British English
(ˈdɔːbɛl)
noun
a bell that is rung by visitors to a house to alert someone inside to their arrival
A few days later, the doorbell rang at the home of designer Halston.
There was a long ring on the doorbell.
I rang the doorbell but no-one answered.
doorbell in American English
(ˈdɔrˌbɛl)
noun
a mechanism, now usually activated by a push button at the entrance of a building or room, that rings, buzzes, etc. to alert the occupants of a visitor