Sentinel GPS BPR-1a WM Basic Wall Mount Power Relay The BPR-1a Basic Power Relay is designed to allow seamless integration of controllers, devices and equipment in gardens, greenhouses, grow rooms or other environments The BPR-1a can operate in a Normally Off mode  where the trigger cable activates attached devices  allowing controllers or timers to operate multiple pieces of equipment or larger amounts of amperage The BPR-1a can also operate in a Normally On mode  where the trigger cable turns off attached devices  allowing controllers or timers to coordinate various functions (for example, turning CO2 equipment off when ventilation fans activate)