The DS938Z is a ceiling-mount, 360 degree passive infrared intrusion detectors that uses Motion Analyzer II to reduce false alarms. It is equipped with advanced PIR detection and supervision circuits and is designed to provide an alarm condition upon detection of an intruder passing through its area of coverage. Motion Analyzer II uses multiple thresholds and timing windows to analyze timing, amplitude, duration, and polarity of signals to make an alarm decision, Three PIR sensitivity settings are available. Several unique self-test features, including Motion Monitor, provide coverage integrity. Field replaceable mirrored optics allow it to be mounted on ceilings from 8 ft. to 18 ft. (2.4 m to 5.5 m in height).