A doorbell is a signaling device installed near the entrance of a building, allowing visitors to alert the occupants of their presence. When pressed, it typically produces a sound, such as a chime or a ring, to notify those inside. Doorbells can be wired or wireless, with wireless versions often powered by batteries. Modern doorbells may also include features like video cameras and intercom systems, enabling homeowners to see and communicate with visitors remotely. These advanced models are often connected to smartphones, providing added convenience and security for residents.