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, notifying those inside that someone is at the door. Doorbells can be mechanical, producing a simple ringing sound, or electronic, offering various tones and features. Modern doorbells often include additional functions, such as video capabilities, allowing homeowners to see who is at the door through a connected device. Some advanced models, known as smart doorbells, can connect to the internet, enabling remote monitoring and communication with visitors via a smartphone app.