Bunker Hill Security magnetic window and door alarm chime set provides a simple and effective way to monitor entry points in your home or office. This two-pack features a magnetic sensor switch that detects entry and offers two distinct modes: a loud alarm for security or a pleasant "ding-dong" chime for visitor notification. Designed for easy installation, these units attach to doors or windows using the included adhesive tape, requiring no complex wiring. Each unit is powered by three 1.5V LR44 button cell batteries, which are included in the factory-sealed packaging. Distributed exclusively by Harbor Freight Tools, these compact white sensors are a practical addition to any basic security setup.