A doorbell is a device which is typically installed to or near a door. When a visitor presses a button, the bell rings inside the building, alerting the presence of the visitor.
Older doorbells were fully mechanical. Newer electrical doorbells were installed by wires and use a push-button to activate the sound. The latest doorbells have wireless connections.
Images for kids
Doorbell at the entrance of Chetham's Library, Manchester, England
Doorbell mechanism from 1884 in Andrássy Avenue, Budapest
Old door bell pull knobs in Edinburgh, United Kingdom. It is unclear whether bells were running by wire and pullies, or by electrical connection.