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.
This and other rules need strengthening.