A doorbell is a signaling device installed near the entrance of a building, typically used to alert occupants of a visitor's presence. When pressed, it activates a chime or sound inside the home, notifying residents that someone is at the door. Doorbells can be traditional mechanical types or modern electronic versions, which may include features like video cameras and intercom systems. Many doorbells are powered by electricity, while others may use batteries. Some advanced models connect to the internet, allowing homeowners to see and communicate with visitors through their smartphones. This technology enhances security and convenience for residents.