In a UL burglar alarm system, motion detectors shall be installed so that they are not influenced by outside movement in an unprotected area.

• A. They should be mounted on the floor
• B. They should be installed only in closets
• C. They’re not influenced by outside movement in an unprotected area
• D. They should be placed near windows

Answer: (C)

Motion detectors in a UL burglar alarm system must be placed so they respond to activity inside the protected area and aren’t driven by activity outside that area. This reduces false alarms from people or movement outside the secure zone and keeps the system reliable. The best answer states that detectors are not influenced by outside movement in an unprotected area, which directly matches the goal of proper installation.

Other placement ideas don’t ensure this reliability: mounting on the floor isn’t typical for most detectors and can introduce blind spots or false triggers; installing only in closets leaves large interior spaces unprotected; placing near windows makes it easier for outside movement to trigger the detector.