When installing outdoor photo beams, what should the installer ensure regarding the beam?

The correct choice emphasizes the need for a proper security setup when installing outdoor photo beams, specifically regarding how the beam is designed to operate. Photo beams work by creating an invisible line or beam between two points, and the interruption of this beam triggers an alarm or alert.

When an installer aims to set up these beams, they should ensure that the beam can effectively detect unauthorized access without generating false alarms. The guideline indicating that the beam should block 85% without causing an alarm suggests a balance between sensitivity and reliability. This level of obstruction allows for a degree of environmental interference—such as moving tree branches or weather elements—while still being able to trigger warnings when actual intrusions occur.

By providing a threshold that allows for some interference without activating alarms, this option highlights an important factor in outdoor security systems: they must be sensitive enough to detect threats but also robust enough to avoid false alarms, which can lead to unnecessary responses. Such a setup ensures that the system remains reliable and efficient in safeguarding property.