The HM-50 Series sensor provides Bi-Directional High Bay Aisle Way sensing extending 70 to 110 feet when mounted at heights of 30 to 45 feet. HID Bi-Level or T-5 / T-8 Fluorescent systems can be switched using this sensor and power packs. The HM-50-SH controls Bi-Level HID with a Start-to-High timer, whereas the HM-50 controls individual fluorescent fixtures. The sensors view pattern provides coverage of the lighting areas of three typically spaced High Bay fixtures. Therefore, when mounted at a fixture, the coverage area extends out to the area that is lighted by the neighboring fixtures. This effect is useful with some Program-Start ballasts that have a delay such that when traveling in a fork-lift truck, lighting needs to be initiated On ahead of the truck. Masking the sensor to cutoff at the end of an aisle is easily done with the enclosed kit. For freezer or high humidity applications, use the HM-50-LT or HM-50-SH-LT which allows for cold temperatures or condensing humidity. For total aisle way sensing consider the HM-10 at each end, and HM-50s in the center section.