A security alarm is a system designed to detect intrusion – unauthorized entry – into a building or other area. Security alarms are used in residential, commercial, industrial, and military properties for protection against burglary (theft) or property damage, as well as personal protection against intruders. When a door or window is closed, the two parts of the sensor are joined together, creating a security circuit. When the security system is armed at the control panel, these sensors communicate with it by reporting that the point of entry is secure. Our home alarm security systems are constantly monitoring to ensure that once a burglary alarm is received at a Customer Monitoring Center, a trained ADT professional will notify you and first responders quickly.