The SuperDuct SD Series duct detectors offers the convenience of modular design plus the power of advanced sensing technology. Available in a two wire version or a four wire version with separate controllers able to serve two detectors, installers have the freedom to configure the SuperDuct to suit the tight spaces typical of duct applications - and still have ready access to field connections and maintenance features. The SuperDuct's advanced circuit board-mounted photoelectric sensor is an integral part of the detector assembly and features environmental compensation that does away with sensitivity drift once and for all, ensuring unparalleled stability and reliability even under harsh environmental conditions. With its innovative remote test station, SuperDuct detectors can be tested for dirt contamination remotely, eliminating the need to physically access the detector with a sensitivity tester. This feature saves countless hours of fumbling with ladders and climbing into awkward spaces.