The Wattstopper LMLS-400-L is a closed loop single-zone DLM photosensor with an extended tube, used to measure ambient light levels and automatically switch or dim one zone of lighting to maintain a target setpoint. The extended tube configuration reduces fixture spill light interference, improving measurement accuracy in open office, classroom, and daylit commercial spaces. Compatible with the Wattstopper DLM network for plug-and-play commissioning.