System Sensor D4120 Detector

System Sensor D4120 Gas/Smoke Detection, 24Vac/dc or 120Vac Power Supply, 4-Wire Photoelectric Low-Flow Duct Smoke Detector with two DPDT relay contacts and Test/Reset button

D4120 is the direct replacement for 70-540000-002, 70-600000-054, 70-600000-157