A burglar alarm is a security device designed to detect unauthorized entry into a building or area. It typically consists of sensors that monitor doors, windows, and other entry points. When a sensor is triggered, the alarm emits a loud sound to alert occupants and deter intruders. Some systems can also send notifications to the property owner or local authorities. Modern burglar alarms may include features like motion detectors, surveillance cameras, and remote monitoring through smartphones. They can be wired or wireless, making them adaptable for various settings, from homes to businesses. Proper installation and maintenance are essential for effective security.