System Sensor System Sensor 2151 Photoelectronic Low-Profile Plug-In Detector for Special Applications JMAC# SYSTEM-SENSOR-2151 The System Sensor 2151 is a low profile, plug-in photoelectric smoke detector.100 Series Plug-in Smoke Detectors offer superb performance and reliability in a profile which is just 2" (5.1 cm) deep.Model 2151 (photoelectric sensor) and model 2151T... MSRP: Was: Now: $73.19 In Stock Expedited Shipping Available Need it Tomorrow? Need it Tomorrow? Select the NEED IT FAST shipping option at checkout and a member of our team will contact you promptly with any available Expedited Shipping options once we receive your order. Add to Cart