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fire alarm system monitoring 131. Door contacts may be hardwired or wireless; hardwired contacts are usually buried in the doorframe, which is less obvious than wireless and are preferable. Window Contacts: Can be hardwired or wireless. Motion Sensors: It’s the most essential and common form of protection. Passive infrared sensors: Detect motion by sensing a sudden change in heat. Dual Tech motion detectors use two different technologies in the same unit: passive infrared and microwave. These devices are designed to avoid false alarms since both technologies must detect motion before setting off the alarm. Photoelectric Sensors: These sensors project a beam of light across a hall or doorway to detect motion and are triggered when a person passing through interrupts the beam. Glass Break Detectors: Usually mounted near windows to detect the specific high frequency sound of glass being shattered. They are usually installed on a wall opposite or adjacent to the protected glass and are effective within about 15′ to 25′. Smoke and Heat Detectors: Detect smoke and heat.

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