What is the mounting height range for intruder photoelectric units?

• A. Not less than 18 inches nor more than 36
• B. 12-24
• C. 60-72
• D. 12-18

Answer: (A)

Photoelectric beams detect intrusion by a clear line-of-sight path between a transmitter and a receiver. The height at which you mount these units matters because it influences both reliability and false alarms. Mounting them between 18 and 36 inches above the floor places the beam where a typical person will break it when crossing the path, but it’s high enough to avoid many common floor-level disturbances and furniture movement that could cause false alarms. It also helps guard against easy tampering, since the units are out of easy reach but still accessible for maintenance. If you mount them much higher, someone could pass over the beam; if too low, everyday objects or pets could trigger it. So the best range for intruder photoelectric units is 18 to 36 inches above the floor.